GEOLOGY OF THE

GREYMOUTH AREA

SIMON NATHAN

M. S. RATTENBURY

R . P. SUGGATE

(COMPILERS)

Interim New Zealandgeological time scale fromCrampton & others (1995),wi th geochronology afterGradstein & Ogg (1996) andMartinson & others (1987).Modified after Crampton &others (2000) and Graham& others (2000).

Interna tional New ZealandI ;;

*~M-l. Pleistocene

;J £§ SelinuntianCasUediffian W,

"?•• Gelasian l Nukumaruan W.e" M" aparlliln Wm." PlaC8rwan

g~Wai ·

o. ~ lanclean Oporuo. Wo

Me5Slnliln Kapilean Tk

~• $ T"""""""",,,," nj ",,,""'.

""""""""W~ S.• I0 e

- ~,

00" •~i 0 ~ s

N .........0 ~ """"""'" So•Z 'i:

!UJ ~

!""""". "

0 Burdigalian" ""'". F'<>

u aman Wallaluan l.

li ChaltJan ~ DunlrOOnian CO

jWha'ngaroaon l"'"

Ow Rupelian

Late nabon'an " " ·, 1., Itoman ge ~ " """"'""

,.§. Lute!lan Poran an 0W Herelau '" 0'

~ YpI'esian ~ Mangaorapan Omw > Wal awan

~ " Thanellan I~,Selan<:lIan0" Teunan 01

*~ Dan;ano.w

Maastricht'an

~ Haumurian M'Campanian

3 SantO<1ianPiripauan MF

Coniacian

!Teratan R,

Turonian Man aotanean Rm0

,Arowhanan R"0 "0 CenomanIan

Ngaterian C.~ !" ~ """~. Cm~ AIO".<.l u

UnJtawan C,_.. K~. • Uk

0 """"""'. :gwUndifferentlated

HauteflYl3<'l ~ Taltal........... """_.0 T_ ~ """"" Dp

-0 § """"'" Ko

N "'"""""""'0 """"""" """""" ""(f) c-.. JUJ .2 1 "'-::;; ~~Temaikan ~~>

0

"''''''''',""-

Toa.rtian Ururoan H,

, Pliensbachian

orI

~Sinemurian

Arataufan H"Hettangian

Rhaetian Otapirian So

~ Warepan ,.~

Norian~ Otamitan ' m

Oretian B'.~ Carnian Kaihi"uan Gk0•i" ~ Ladiman

~ Etalian G.>

Anrsian

Gm'a a aVIanOlenekian

~ Ir.duan ?

227

206

"

'"

53

"

'"

""1M"

..0

2"

11.2

",

'"

28.5

33.737.0

98.9

61 .0

4g.0

65.0

238

"..

Interna tiona l New Zeala"d

~~~~~~DZl'Iulfianl f Maltarewan VDm

§WLlChiaPlngJan 0

'0TatananIMld'3n

allllan

"""~.•e•~ ! Branonian VA'"§

Mangaplrian YAm•0. M."",", '."

j """"""'.w pre-Telfordian V........

3

00e~ Fe0£•<.l~

0w

•j JU

I---,~ JM ,

e>I---0 ..

- e

0 ~ Ems;an J,'•N D I---0 ~ Pragian JF '0UJ w

I---..J

«: LochoVIan Jotl.

p"",,"

~e".~ l""","0 E

ijj~ W..-0w

ua""",""

""""....... Vb<>

EaslOnian Veo§

e..-e

"""""""" V.

:~t uaodoi<>

~:i ""'"'" Oarriwillian V'"

0 §i ~....... ma'"lan ~-- Vbo

~

"""'''''''. "'"T_pre-lancefieldian V.,

'" ''''3 Pa nlO<1ian

"""1 •• teOm •Mind anan

BoomerangJan 'boI---

Undillan ''"eI---

~~ Flo,,,. '"E~ I---•<.l Templeton ian '"I---Ordlan 'oc

~ Xlw

Precambrian Z

505

518

323

370

256

290

",

39,

<IT

'"

"0

"3

'90

'56

GEOLOGY OF THE

GREVMOUT;H AREA

Scale 1:250 000

SIMON NATHAN

M. S.R:ATTENBURY

R. P. SUGGATE(COMPILERS) ..

Institute of Geological & Nuclear Sciences 1:250 000 geological map 12

Institute of Geological & Nuclear Sciences LimitedLower Hutt, New Zealand

2002

BmLIOGRAPHIC REFERENCENathan, S.; Rattenbury, M.S.; Suggate, R.P. (compilers) 2002: Geology of the Greymouth area. Institute of

. Geological & Nuclear Sciences 1:250000 geological map 12.' 1 sheet + 58 p. Lower Hutt, New Zealand.Institute of Geological & Nuclear Sciences Limited.

Edited, designed and prepared for publication by P. J. Forsyth and P. L. Murray

Printed by Graphic Press & Packaging Ltd, Levin

ISBN 0-478-09752-2

© Copyright Institute of Geological & Nuclear Sciences Limited 2002

FRONT COVER

The town of Greymouth is situated on postglacial sediments at the mouth of the Grey River, in front of limestone bluffs that makeup the Twelve Apostles Range. In past years coal from the Greymouth Coalfield was shipped out of the river port in small colliers,but it is now railed over the Southern Alps to Christchurch.

Photo CN35937R: D.L Homer

CONTENTS

ABSTRACT . v LATE CRETACEOUS AND TERTIARy . ..25

Keywords .

INTRODUCTION .

THE QMAP SERIES .

. v

. I

...... I

Late Cretaceous to Paleocene sedimentary rocks 25Eocene sedimentary rocks 25Ol igocene to earliest Miocene sedimentary rocks T!Earl y to Middle Miocene sed imentary rocks 29Late Miocene to Pliocene sedimentary rocks 30Late P liocene to Early Pleistocene sedimentary rocks. 30

GEOMORPHOWGY 3

STRATIGRAPHy.... II

CAMBRIAN TO EARLY CARBONIFEROUS II

T he QMAP geographic information system 1Data sources 1Reliability I

. 49

. 39

......... 31

ENGINEERING GEOLOGY .

GEOLOGICAL RESOURCES ....

Paleozoic-Mesozoic rocks west of the Alpine Fault 49Paleozoic-Mesozoic rocks east of the Alpi ne Fault 49Tertiary sedimentary rocks 49Quaternary sedi ments .. 49

AVAILABILITY OF QMAP DATA 51

QUATERNARY.

Seis l1lo tectonic (earthquake) hazard . 46Lands liding . 47Tsunam.i................................... . 47

GEOLOGICAL HAZARDS 46

Gold. . 39Ilmenite (and associated minerals) . .. 40Other metallic mjnerals 40Clay... . 41Rock 41Greenstone (nephrite. pounamu) and good letite 42Limestone. .. ...42Other non-metall ic minerals 42Coal ............ . 43Oil and gas .. .. 45Water 45Warm spri ngs . 45

Glacia l deposits 31A lluvial deposits 34Alluvial fan deposits ... 34Coasta l marine deposits and dunes . .. 34Swamp and lake depos its 34Scree deposits . .. 36Landsli de deposits 36Deposi ts of human origin . 36

TECTONIC HISTORy 37

17

.3

. 3

PERMIAN TO EARLY CRETACEOUS .

Takaka terrane . 1.3Cambrian to Ordovician volcanjc and sedimentaryrocks 13Late Devoni an to Early Carboniferous intrusive rocks 14

Buller lerrane . 11Ordovic ian sedi mentary rocks 11Paragneiss and associated rocks 12Devonian sed imentary rocks 13

West of the Alpine FOliit . . 17Triassic-Jurassic sedjmentary and volcanic rocks 17Early Cretaceous granitoid rocks 17Early Cretaceous sed imentary rocks 17Cretaceous d ikes and high level intrusions. 19

Southern Alps 3Alpine Fault. . 3Western mountains . . 5Lowland areas 5Plateau areas . 9Present day deformat ion . 9Offshore bathymetry. 10

East of the Alpine Fault: Rakaia terrane .... 21Late Triassic sedimentary rocks . .. 21Late Tri assic semischi stose and schistose rocks 21Structure of Rakaia rocks 22

Culture and land-use .

REGIONALSEITING ...

ACKNOWLEDGMENTS. . 51Esk Head belt. . 22Late Jurassic - Early Cretaceous melange 22 REFERENCES . . 52

ABSTRACT

The Greymouth 1:250 000 geological map covers13 000 km2

, and includes the central part of the West Coastregion in the South Island of New Zealand. The map area isbisected by the Alpine Fault- a major strikC}-slip fault fonningthe active plate boundary between the Pacific and Australiantectonic plates. Late Cenozoic movement (which continuesto the present day) has led to the juxtaposition of twodifferent geological provinces.

Southeast of the Alpine Fault the rocks are part of theMesozoic Torlesse composite terrane, a thick, highlydeformed sequence of mainly submarine fan sedimentaryrocks, of quartzofeldspathic, continental derivation. Thetopography is mountainous, and the Southern Alps rise fromnear sea level to a maximum height of over 2200 metres.

Northwest of the Alpine Fault the pre-Cretaceous rocks arePaleozoic metasedinientary and plutonic rocks that representa fragment of the Gondwanaland supercontinent.Gondwanaland started to break up in the Early Cretaceous,a period of widespread· emplacement of granitoid rocks,uplift, and detachment faults -resulting in the formation ofmetamorphic core complexes. Fanglomerates were depositedaround the rising mountain ranges.

The older rocks on both sides ofthe Alpine Fault were largelycovered by Cenozoic sediments. Regional extension led tosubmergence by the middle of the Oligocene,·and widespreaddeposition of limestone or calcareous sedimentary rocks.Development of the present oblique-compressional plateboundary started in the Early Miocene, and led to a complexlate Cenozoic history, with development of small fault­bounded basins and widespread uplift and erosion. Rapid

Keywords

uplift of the Southern Alps started in the Pliocene, but theWest Coast ranges did not start to rise and form the presentrange-and-basin topography until the early Quaternary.Regional uplift by folding and faulting continues to thepresent day.

Glaciation during cool periods in the Quaternary resultedin downstream aggradation from moraines and down-valleyglacial outwash gravels. During warmer, interglacial periodsthere is evidence of higher sea levels near the coast frommarine terraces that have been subsequently uplifted.

Gold has been mined for over 100 years from both quartzveins and alluvial deposits. Over 70 000 kg ofgold has beenextracted from quartz veins in the Reefton Goldfield, andplanning is currently underway to open a new opencast mine.Substantial reserves of ilmenite have been defined by drillingin postglacial sands near the coast. The map area containsalmost all the reserves of bituminous coal in New Zealand(300 million tonnes estimated as recoverable), mainly inthe Buller and Greymouth coalfields, although not all ofthis may be able to be mined. Recorded seeps and shows ofoil and gas have encouraged prospecting for hydrocarbons,but no commercial finds have yet been located.

The Greymouth map area is subject to natural hazards,including a high level of seismic hazard from the AlpineFault and other active faults, with potential for earthquakeshaking, landsliding, liquefaction and ground rupture.Several large, damaging earthquakes with epicentres withinthe map area have occurred within the last 100 years.Landsliding, rockfall, tsunami and flooding are ongoinghazards.

Greymouth; West Coast region; 1:250 000 geological map; geographic information system; QMAP; digital data;bathymetry; Buller terrane; Takaka terrane; Torlesse composite terrane; Rakaia terrane; Pahau terrane; EskHead belt; metamorphism; textural zones; Karamea suite; Rahu suite; Separation Point suite; Alpine Fault;Southern Alps; Grey Valley; Paparoa Range; Victoria Range; Greenland Group; Gondwanaland; Waipounamuerosion surface; glaciation; interglacial; dredge tailings; gold; ilmenite; uranium; clay; greenstone; pounamu; .nephrite; limestone; coal; hydrocarbons; Kotuku oil seep; active fault; engineering geology; earthquake; ModifiedMercalli scale; landslide; tsunami, 133, J31, J32, J33, K29, K30, K31, K32, K33, L29, L30, L31, L32, L33.

v

170" E: 175" E

180" E'

0i-...."".;.;'OO~_....;;;200Kilometres

2000

Auckland

--.-- --..-, -. -.. --. ----- -. --.-- ---.-- --. ---- .. ~!i:_~Whangar ~i

175" E

';SI-_ -,--!,i-.L---, '5

Campbel/ Plateau

/, Dunedin

I

Chatham Rise !I,,

, ,I Waitakr - -- -- ---- ._-- --- ---- - . - - -"t - -. --. - _. -- ------ - -- - .- . . .. __ .~~?~_~_

,,

Bounty !Trough !

,

170" E ,

I

,

Murihiku~7 mm/ r

.----i /~ "'-Wak:ati6l!J "

.I

,,I

,

1

'%~O :

:>_~: ~- -- -- __c$>~ _ ------- -.- .-----. ·-··r -.---- -.------.. '-K"t,,;,,"00...... . 200~ :-~ v :~ i

is'-0 ',,I, I

: f-----r+-I -L._,--_----,; \ / /.... ~ :'

, Waikato . R~O;~~~~ II ~ 11 !Chal/enger :, ';.j i 47 ~m/y~Taranaki ,I. Raukumara :

Plateau ; Basin ~ .' jL / j ;I, ,

' " HawKes I

: Tar,!~akl - B'aY ";4 i, " ) '.f< ; ,

.~9:-?- - ..------ -- -~~~~-;~~;~~.T'------..--..------- ---- -.- . --.--- ..-; ; j/~/' -.- -.-.:~~~~lf ..4Q:i~·

, ';S Plate Nelson well lnQt69! wa"a.~rapa ~ i1 '5 ,/;;.. / 'l>\:- !

,/ ~ .-'" Ii ~ d~ :

" QMAP : ' jf If/f"V / I V .},\, :, ---.-~ . 1-1" l!7.'9 -/,/ ..,,? " ' ,

Greymouth I.... Jt./"Co ' f ~ I\ ,,/:Z~oUra ...... .....r 41 mm/yr p, f/ ~Y.. ~ acific, /.0'-' - [if'£-! Plate1 '~'~~;i-1;"?"'-

~\' /" 38 in'1fl1 r~/ . \ Christchurch

HaasV~ Aor.aki "./ I ~ r

Figure 1 Regional tectonic setting of New Zealand showing the location of the Greymouth geological map and otherQMAP sheets, major offshore features (as illustrated by the 2000 metre isobath), and active faults . Arrows indicate thedirection and rate of convergence of the Pacific Plate relative to the Australian Plate.

Adapted from Anderson & Webb (1994)

vi

INTRODUCTION

THE QMAP SERIES

This geological map of the Greymouth area (Fig. 1) is oneof the new national QMAP series (Quarter-million map;Nathan1993) being produced by the Institute ofGeological & Nuclear Sciences Ltd (GNS). QMAPsupersedes the current Geological Map of New Zealand1:250 000 (''four miles to the inch") series. Three published"four mile" sheets - Buller (Bowen 1964), Hokitika(Warren 1967), and Hurunui (Gregg 1964) - overlap withthe Greymouth QMAP area. Since then, a considerableamount of geological research has been completed,including detailed geological mapping at 1:63 360or 1:50000scales (Laird 1988; Nathan 1975; Nathan 1978a; Nathan1978b; Nathan 1996; Roder & Suggate 1990; Suggate &Waight 1998), as well as industry investigations and

.university theses. In addition the whole sheet has beenpart of a regional synthesis of Cretaceous and Cenozoicsedimentary basins (Nathan and others 1986).

The geology of the Greymouth QMAP area is in manyplaces so complex that it has been considerably simplifiedin order to present it legibly at 1:250 000 scale. Rock unitsare mapped primarily in terms of their age of deposition,eruption, or intrusion. As a consequence, the colour of theunits on the map face reflects their age, with overprintsused to differentiate some lithologies. Letter symbols (inupper case, with a lower case prefix to indicate early,middle or late if appropriate) indicate the predominant ageof the rock unit. The last lower case letter or letters indicatea formally named lithostratigraphic unit and/or thepredominant lithology. Metamorphic rocks are mapped interms of age of protolith (where known), with overprintsindicating degree of metamorphism. Age subdivision is interms of the international time scale. Correlation betweeninternational and local time scales and absolute ages inmillions of years (Ma), revised as necessary for QMAP(Crampton and others 1995), is shown inside the frontcover.

The description of the geology accompanying thegeological map is generalised and is not intended to be anexhaustive description of the various rock units mapped.For more detailed information the reader is referred toreferences cited throughout the text.

The QMAP geographic information system

The QMAP series uses computer methods to store,manipulate and present topographic and geologicalinformation. The maps are drawn from data stored in theQMAP geographic information system (GIS), a databasedeveloped and maintained by GNS. The primary softwareused is ArcInfo®.

Digital topographic data were purchased from LandInformation New Zealand and its predecessor theDepartment of Survey and Land Information. The QMAPdatabase is complementary to, and can be used inconjunction with, other spatially referenced GNS digitaldata sets, e.g. gravity and magnetic surveys, mineral

resources and localities, fossil localities, active faults, andpetrological samples.

The QMAP series and database are based on detailedgeological information plotted on 1:50 000 topographicbase maps. These data record sheets are available forconsultation at GNS offices in Lower Hutt and Dunedin.The 1:50 000 data have been simplified for digitisingduring a compilation stage, with the linework smoothed,and geological units amalgamated to a standard nationalsystem based on age and lithology. Pointdata (e.g. structural measurements) have not beensimplified. All point data are stored in the GIS, but onlyselected representative structural observations are shownon the map. Procedures for map compilation, and detailsof data storage and manipulation techniques, are givenby Rattenbury & Heron (1997).

Data sources

The map and text have been compiled from publishedmaps and papers, unpublished university theses, GNStechnical and map files, mining company reports, fieldtrip guides, the New Zealand Fossil Record file in itsdigital form (FRED), and GNS geological resources(GERM) and petrological (PET) digital databases (Fig. 2).Additional field mapping has been undertaken to resolveproblems and to ensure a minimum level ofcoverage overthe map area. Landslides were mapped from aerial photos,with limited field checking. Offshore data have beencompiled from published studies of the West Coast region(Nathan and others 1986). Data sources used in mapcompilation are summarised in Fig. 2, and are cited withother studies relating to the Greymouth QMAP area inthe references.

Reliability

As a result of the compilation and simplification process,the accuracy with which geological contacts, faults, andfolds are shown on the 1:250 000 map has diminished,although point data are accurately located in terms of theNZMS 260 grid; the unpublished 1:50 000 data recordmaps have a higher standard of detail and accuracy. The1:250 000 map is of regional scale only, and should notbe used alone for land use planning, planning or designof engineering projects, earthquake risk assessment, orother work for which detailed site investigations arenecessary. Some data sets incorporated with the geologicaldata (for example the Geological Resources Map of NewZealand [GERM] data) have been compiled from old orunchecked information of lesser reliability (seeChristie 1989).

1

"

..

"

"

..

"

..

"

"

1 Angus 19842 Becker & Craw 20003 Bell & Fraser 19064 Berryman & others 19925 Blackmore 19986 Botsford 19837 Bowen 19648 Bradshaw & Hegan 19839 Bradshaw 199510 Brown 199811 Browne 198712 Cave 198213 Cave 198614 Chinn 197315 Cooper 199216 Cutten 197617 Dixon 200118 Findlay 197919 Fyfe 196820 Gage 194521 Gair 196222 Gregg 196423 Inwood 199724 Ireland & others 1984

25 Jury 198126 Koons 197827 Laird 198828 MacKinnon 198029 Maxwell 198230 McLean 198631 Morgan 190832 Mortimer & Smale 199633 Mortimer 198434 Munden 195235 Nathan 197536 Nathan 197637 Nathan 197738 Nathan 1978a39 Nathan 1978b40 Nathan 199441 Nathan 199642 Nathan & others 198643 Parish 199844 Petrie 197445 Rattenbury & Stewart 200046 Rattenbury 198747 Roder & Suggate 199048 Suggate & Munden 1952

49 Suggate & Waight 199850 Suggate 195751 Suggate 196552 Suggate & others 196153 Tulloch 1979, 199554 Turnbull & Forsyth 198655 Waight 199556 Warren 196757 Wellman 194558 Wellman 195059 Wellman & others 195260 White 198861 Wilson 195662 Wright 199863 Yang 198964 Young 196665 Young 1968

2

Figure 2 Major sources of geological data used in compiling the Greymouth geological map.

REGIONAL SETTING

QMAP Greymouth is bisected by the Alpine Fault - amajor active fault with predominantly dextral strike-slipmovement - that forms the active plate boundary betweenthe Australian Plate (to the northwest) and the PacificPlate (to the southeast) in the central part ofNew Zealand.Many of the other major faults within the map area alsoreflect the wide zone of deformation associated with theplate boundary.

The plate boundary developed during the later part of theCenozoic, and approximately 480 km of strike slipmovement has been demonstrated by offsetting of terraneboundaries across the Alpine Fault. This has led to thejuxtaposition of two different geological provinces within

. the Greymouth map area;

Fig. 3 shows the complex 'pattern of pre-Cretaceoustectonostratigraphic terranes in the New Zealand region.Within the Greymouth map area the pre-Cretaceous rocksof the Australian Plate are Paleozoic metasedimentary andplutonic rocks that represent a fragment of theGondwanaland supercontinent. Southeast of the AlpineFault, the rocks of the Pacific Plate are entirely of theTorlesse composite terrane - a thick, highly deformedsequence of mainly submarine fan sedimentary rocks,predominantly quartzofeldspathic, of continentalderivation.

The pre~Cretace{>us rocks on both sides of the Alpine Faultwere largely covered by Late Cretaceous and Cenozoicsediments, although these have been partly removed byerosion. Development of the plate boundary along theAlpine Fault has led to a complex later Cenozoic history,with uplift leading to the formation of mountains fromPliocene time onwards. During the Quaternary period therewas extensive glaciation in the mountains, and the lowlandareas are covered with a widespread veneer of lateQuaternary gravels and glacial deposits.

Culture and lan.d-use

The Greymouth geological map covers the West Coast ofthe South Island from Ross north to Westport and extendsinland into northwest Canterbury and the upper Bullervalley, aland area of approximately 13 000 km2 (Fig. 4).The map area is sparsely populated with most people livingin the coastal towns of Greymouth (population 10000),Westport (4600), and Hokitika (4000), and smaller inlandcommunities of Inangahua, Reefton, Dobson and Ross.The West Coast is linked to Canterbury by road and railvia Arthur's Pass, and by road via Lewis Pass to the eastofSprings Junction. The lower reaches of the Buller, Grey,and Hokitika rivers are extensively farmed. Plantationforestry, coal mining and alluvial gold mining are alsosignificant land uses. Most of the map area is covered inindigenous forest and the area includes Paparoa NationalPark, Victoria Conservation Park, and parts ofArthur's Passand Kahurangi national parks.

GEOMORPHOLOGY

The landscape of the Greymouth area has been mouldedby a combination of late Cenozoic uplift (withaccompanying erosion), the effects of Quaternaryglaciation, and coastal erosion.

Southern Alps

Within the Greymouth map area the Southern Alps risefrom near sea level to a maximum height of2280 m (Mt Davie). The mountains trend northeast andform a drainage divide, the Main Divide, betweenCanterbury rivers draining to the southeast and thenorthwest-flowing rivers of the West Coast (Figs 4 & 5).

The northwestern range front of the Southern Alps is steepand high, and deflects the prevailing westerly air streamupwards, resulting in periods of exceptionally heavyrainfall. The maximum rainfall recorded exceeds 10 metresper year in an area 3-5 km southeast of the range front(Griffiths & McSaveney 1983), and the rivers draining thisarea are often steep, deeply incised and prone to rapidflooding. Rainfall decreases westwards to less than3 metres per year at the coast.

Southeast of the Main Divide rainfall also decreasesmarkedly. The southeastern flanks of the Southern Alpsare dissected by a complex series of tributaries that coalescedownstream into relatively large, braided, shallow-gradientrivers.

During the colder phases of the Quaternary, the SouthernAlps were extensively glaciated, with glaciers extendingdown the main valleys. Small glaciers are now found above1900 metres on east- to south-facing slqpes. Valleys thatwere previously glaciated typically have steep sides, andlandslides, alluvial fans and lakes are common as thelandscape readjusts to a warmer, wetter climate(Figs 6 & 7).

Alpine Fault

The Alpine Fault is a clearly marked feature that effectivelysplits the map area into two parts (Fig. 8). Ittrends about 050", and satellite images highlight a straight,linear trace.

The dip of the Alpine Fault is generally about 40-50° SE(Sibson and others 1979). Locally, however, surfaceoutcrops show that the dip flattens, probably partly due tonear-surface effects, and consequently the surface trace issinuous in detail where there is incised topography(Suggate 1963).

There are many examples of streams, terrace risers andchannels right-stepping in 6-13 metre multiples across theAlpine Fault reflecting the recent and ongoing dextral­component displacement of the fault (Wellman 1953;Berryman and others 1992). Some of the larger valleysdraining the Southern Alps, such as the Hokitika and

3

4

0 Cretaceous & Cenozoic sedimentary rocks

Median Batholith - Northland and East Coast Allochthons

• • Waipapa composite terrane Tor1esse compositeu Takaka terrane u (western North Island) terrane (eastern NZ)- l"h~ -> Buller terrane composite > • Monin~ai8HiII 1-"0 terrane 0

Esk Head bellundifferentiated Hunua-Bayollsl9nd$ melange~ ~

Rakaia- Cretaceous plutonic rocks - Caples terrane

~ ~ Dun Mountain - Maltai terrane 1111111 schist

· - Devonian-Carboniferous plutonic rocks ·• • Murihiku terrane~ - w

~ gneiss?Silurian-?Devonian gneissic rocks Brook street terrane

Figure 3 Pre-Cenozoic basement rocks of New Zealand, subdivided into tectonostratigraphic terranes; the extent ofthe Northland and East Coast allochthons is also shown. The map on the right shows more detail for the QMAPGreymouth area.

Taramakau, suggest 3- 10 Ian right lateral shifts, althoughthe evidence is equivocal. For example, it is inferred thatthe glaciers that once filled the Kokatahi-Toaroha-Styxcatchment may have previously flowed into Lake Kaniere.

Western mountains

The north-trending Victoria and Brunner ranges and theNNE-trending Paparoa Range are separated by the Greyand Inangahua valleys, with range-and-basin topographyresulting from late Cenozoic tectonic shortening.The higher parts of the ranges show abundant evidencefor g lac iation including cirques, hanging va lleys anddeposits of till.

The Paparoa Range has a maximum height of 1525 m atMt Uriah, where rugged peaks and ridge tops surroundglacial cirques cut in hard crystalline gneiss and granitoidrocks. The western flank of the Paparoa Range dropssharply to a large low-lying dissected area underla in byCenozoic sedimentary rocks. The eastern flank is morecomplicated with subsidiary ranges and two major riversystems (Grey and lnangahua).

The Victoria Range, rising to 1749 m at Mt [vess, also hasglacial cirques and hanging valleys cut into hard crystallinerocks. The eastern flank of the Victoria Range descendssteeply into the Maruia River, whereas the western flankhas an intricate pattern of deeply inci sed rivers wi thmultiple branches in their headwaters.

10 km

Tasman Sea

The Buller and Grey rivers have incised deep gorges acrossthe Paparoa and Victo ria ranges . The go rges arespectacular ev idence that the rivers have maintained theirwestward path from the Southern Alps as the mountainshave been uplifted during the Quaternary. Many smallerstreams have been deflected to flo w parallel to the ranges.Tn a detailed analysis of the defonnation of terraces withinthe Upper Buller Gorge (Fig. 9), Suggate (L 988) has shownthat uplift takes pLace by a combination of faulting androlding, reflecting deformation of the underlying Tertiarysediments that continues to the present day. Approximately350000 years ago the Buller River flowed along a muchwider floodplain , now preserved as high terraces, and hassubsequently cut a narrow gorge.

Lowland areas

Between the major ranges extensive low-lying areasi!1 clude the Grey-lnangahua Depres s ion and theMaruia va ll ey. These areas are tectonic graben orhalf-graben that have been partially filled by MiddleMiocene to late Quaternary coarse-grained sand and graveldeposits.

The lowland area s also have preserved a lon ghi story of glacial and inte rglacial events, with deposits thatrecord at least five glaciations and three interglacials.Moraines are preserved near the coast in the southwestaround the western fl anks of Mt Greenland ,and in an arcuate lobe between Kumara and Lake Haupiri,

Figure 4 Shadedtopographic relief model ofthe Greymouth map areaderived from 20 metrecontour data supplied byLand Information NewZealand (L1NZ), illuminatedfrom the northeast.

5

Photo CN10403l18: D.L Homer

Photo CN38312121: D.L. Homer

Figure 5 Lake Browning lies just below Browning Pass (1400 m), a low-altitude pass on the Main Divide just west ofMt Davie. The headwaters of the Wilberforce River (foreground) give access, via a historic zig-zag miners' track, up thesteep escarpment to the pass. The Arahura River, which drains Lake Browning, flows through deep gorges to the low­lying land west of the Alpine Fault (distance), and thence to the sea.

Figure 6 The Southern Alps are formed of hard, greywacke-type rocks of the Rakaia terrane. Rock avalanches andalluvial fans, often triggered by earthquakes, are a feature of the landscape. The large rock avalanche in the foregroundcollapsed from the northwest side of Falling Mountain during an earthquake in 1929, transporting an estimated 60million tonnes of broken rock into the west branch of the Otehake River.

Figure 7 Lake Christabel occupies a trough carved by a glacier that flowed down the Blue Grey River. The lake isdammed by terminal moraines deposited during the later part of the last glaciation (about 14 000 years ago), but thehummocky topography immediately downstream is formed by a landslide from the steep valley walls on the southern(left) side; the head scarp of the landslide is not visible in this photograph. The Alpine Faull extends along the valleyof the Upper Grey River about two-thirds of the way up the photograph, with the Victoria Range in the background andthe Paparoa Range in the far distance. Photo CN3862019: D.L Homer

Figure 8 The Alpine Fault cuts obliquely across the Taramakau valley. An abrupt change in lithology on opposite sides,and surface traces cutting Holocene alluvium, allow the location of the fault to be accurately fixed as a narrow, linearzone of deformation. The Hope Fault, which appears to join the Alpine Fault at an oblique angle, is defined by theoffsening of metamorphic isograds and the straightness of the Taramakau valley.

Photo CN32364/ 19: Dol. Homer

Figure 9 About 350 000 to 250 000 years ago the Buller River formed a wide, open valley, now represented by the highterrace at centre left. SUbsequent uplift has caused the Buller River to incise its present, much narrower gorge. Thehigh terrace is crossed by the Lyell Fault, which locally warps the terrace surface (Suggate 1988). The large landslide(upper right) formed during the 1968 Inangahua earthquake, and blocked the Buller River for several hours. Manysmaller landslides also formed during the Inangahua earthquake. Photo CN779/8: D.L. Homer

Figure 10 The Denniston Plateau, northeast of Westport, is part of a widespread Late Cretaceous to early Tertiaryunconformity surface (Waipounamu erosion surface) that was here buried under younger sediments in Late Eocene!Oligocene time and subsequently exhumed by Quaternary uplift. The unconformity is capped by about 30-50 metresof hard, cemented quartz sandstone (Brunner Coal Measures), which has effectively protected the underlying rockfrom erosion. The sandstone forms infertile soil, so that it is largely bare of trees. The surface is warped downwardstowards the viewer, and the zig-zag road actually climbs across coal measures dipping 10-15' west. In the backgroundthe unconformity has been offset approximately 330 metres across the Mt William Fault, and bare sandstone is foundat the top of the uplifted plateau. Photo CN32464/17: D.L. Homer

indicating that substantial glac iers covered much of thewider Lake Br unner area at variou s times in themiddle to late Quaternary. Numerous isolated mountainssuch as Mt Turiwhate, Mt Te Kinga, Island Hill and theHohonu Range were partly glaciated nunataks that the iceflowed around without complete ly covering.

Most of the major lakes in the Greymouth area, includingKaniere, Moana, Poerua, Hochstetter and Sumner, are ofglacial origin, and were formed in glacially-scoured valleysand/or dammed by glacial moraines (e.g. Fig. 7).

Plateau areas

Gently east-dipping plateau areas on the ranges northeastand south of Westport are relics of the once-widespreadLate Cretaceous to early Tertiary erosion surface that hasbeen displaced by subsequent fau lting and largely erodedaway. The erosion surface is commonl y indicated byremnants of Late Cretaceous to Oligocene sedimentaryrock resting uncon formabl y on granitoid, gneiss ic, andmetasedimentary basement (Fig. 10).

Between the coast and the Paparoa Range crest is anundulating , low-reli e f area at 100 to 400 m elevationform ed in Ol igocene limestone overlain by Miocenesediments. The gentle dips of the limestone and high rainfallhave resulted in extensive karst topography inc ludingsinkholes, large cave systems and underground rivers.

Present day deformation

Deformation associated with the plate boundary extendsthroughout the Greymouth map area. Folds and faults havebeen mapped as active structures (in red) on the geologicalmap if there is positive evidence of deformation over thelast 125 000 years. As there have been few detail edinvestigations of individual struc tures, we expect thenumber of structures classified as active to increase as moreresearch is undertaken.

Over the last 100 years there have been several largeearthquakes (magni tude 6.0 or greater) with epicentreswithin the Greymouth map area, although none has beenassociated with the Alpine Fault. This level of earthquakeactivity is an indi cation of the o ngo ing deformationassociated with the AustralianlPacific plate boundary, andis like ly to continue in the future.

The Alpine Fault is infelTed to have ruptured at the surfacein association with large ealthquakes in 1717 AD, about1630 AD, and around 1460 AD (Wells and others 1998).The probabili ty of major rupture on the Alpine Fault isestimated to be up to 20% over the next 20 years (Rhoades& Van Dissen 2000).

The re lati ve plate motion across the A lpine Fault atInchbonnie is 39.5 ± 3 mmtyr along an azimuth of74 ± 3°calculated using the Nuvel-l determination (DeMets andothers 1990; Berryman and others 1992). The relative platemotion determ ined fro m differences in GPS location

measurements repeated over several years is severalmillimetres per year greater (Beavan and others in press).

Longer-term estimates of the rate of strike-s lip movementon the Alpine Fau lt south of the Taramakau River areapproximately 10 mm/year (equi valent to 10 km/millionyears). Dip-s lip movement has proved more difficult toquantify, but is likely to range between 3 and 6 mm/yr(Norri s & Cooper 2000). It is clear that a significaot patt,but not all , of the plate motion is being taken up bymovement at the Alpine Fault. Much of the remaini ngmovement is being accom modated within a zone up to 20km southeast of the Alpine Fault (i.e. mainly within thenalTow belt of schist and semischist) (Beavan & Haines200 1).

The A lpine Fa ult s lip-rate red uces northeast o f theTaramakau River where the Hope Fault joins from the east(Norris & Cooper 2000). The process of transfer of muchof the motion from the Alpine Fault to the Hope Fault is sofar poorly understood.

Figure 11 Displacement of Ihe road between Murchisonand Inangahua across the White Creek Fault caused bymovement during the 1929 Murchison earthquake (Fyfe1929). The photographer is standing on the downthrownside, and the fi gure with bicycle (H .E. Fyfe, geologist) isstanding on the upthrown side. A vertical offset of 14 It 9 in(4.5 m) was recorded , and later investigations indicate ahorizontal offset of 2.5 m (Berryman 1980; Suggate 1990).

Photo: M. Ongley

9

Northwest of the Alpine Fault, the White C reek Faultruptured during the 1929 Murchison earthquake (Fig. II ),and sma lle r surface ru ptures accompani ed the 1968Inangahua earthquake (Lensen & Suggate 1969). Studiesofdefonned late Quaternary terrace surfaces (Suggate 1987,1988, 1992) have shown that there is evidence for ongoingdeformation both close to many mapped faulls and at foldsin the underlying Cenozoic rocks.

Southeast of the Alpine Fault there are active dextral sLrike­sl ip faulls such as the Hope and Poulter fau lts, which haveruptured to the surface in historic times (1888 and 1929respectively). GPS measurements through the Arthur'sPass area indicate marked strain accumulation betweenArthur 's Pass and the Alpine Fault near Inchbonnie (J .Beavan pers. comm. 200 I). Largeeartllquakes such as 1994Arthur's Pass also indicate ongoing defonnatioll .

Offshore bathymetry

The cont inental she lf in the Q MA P Greymouth areaextends northwards to join the submerged continental shelfof the C hallenger Plateau. The sealloor slopes gently«0.5") wi thin 60 km of Cape Foulwind and 45 km ofGreymouth, and steepens to 2_30 and attains a maxi mumdepth of 700 m at the western edge of the map area. There lati vely flat seafloor is inc ised by the Hokit ika Canyonto within 20 km west of Hoki tika. The head ofth e canyonfa lls steeply to the west with wall slopes of up to 8Q

• Thecanyon trends northwest for 20 km and turns to the westacross the Challenger Plateau to the abyssal plains, a tota ldistance exceeding 325 km . The overall smoothness ofthe sea fl oor probably re llec ts the depos ition of largequantities of the bed load carried by the West Coast rivers.

undifferentiatedorthogneiss

I

4

4'"

MiddleDevonian

EarlyDevonian

Silurian

Ordovician

Fraser Complex(older parts)

undifferentiatedparagneiss

I Pecksniff~MetasedimentaTY.

Gneiss

VictoriaParagneiss

Karamea Suite

Terrane

Reefton Group

-------­Greenland tec tonic e vent

Golden Bay Group

Greenland Group

IRiwaka Complex' Iamalgamation

Baton Group'

Ellis Group'

Mount ArthurGroup

LateCambrian

{iQ~-•••••••••••••••••.•••_••••••••

MiddleCambrian

BULLER TERRANE

DevilRiver

olcanicsGroup

HaupiriGroup

I

10

TAKAKATERRANE

Figure 12 Major rock units of the Bulle r and Taka ka terra nes, and the major tectonic events that have affected them.., indicates units that do not occur in the Greymouth map area.

STRATIGRAPHY

The rocks of the Greymouth QMAP area are describedbelow in terms of four time intervals

Cambrian to Early Carbon iferous rocks• Perm ian to Early Cretaceous rocks

Late Cretaceous and Tertiary sedimentary rocksQuaternary sediments

CAMBRIAN TO EARLY CARBONIFEROUS

Early Paleozoic rocks form two IlOIth-trending terranes­the Buller and Takaka terranes (Fig. 3)- separated by theA natoki Fault (B ishop and others 1985; Cooper 1989).Rocks of the Buller lerrane occur widely in the wes ternpa rt of the QMAP Greymouth area and throughoutWestl and. The Takaka terrane is best developed in westNelson but also occurs near Springs Junction (Cooper 1989,1992). The relationships between units in the Buller andTakaka terranes are shown diagrammatically in Fig. 12.

The Buller and Takaka terranes are the oldest structuralunits in New Zealand and can be regarded as constituting"proto-New Zealand" which, together wi th easternAust rali a and Antarct ica, formed the southwest Pacificsegment of Gondwanaland in the early PaJeozoic. These

terranes show strong affinities with terranes in easternAustral ia and Antarctica (Cooper & Tulloch 1992; MOnker& Cooper 1995).

Buller terrane

Ordovician sedimentary rocks

A small area of un fossiliferous siltstone, quartzi te andminor black shale, mapped as part of the Golden BayGroup (8b) occurs in a thin sliver on the western slopes ofBaldy near Springs Junction, separated from Takaka terranerocks by the Anatoki Fault. Correlation with Golden BayGroup in west Nelson (Rattenbury and others 1998) isbased on lithological and structural similarities.

To the west of th e Maruia va ll ey, the wid espre adGreenland Group (eg) consists of interbedded li ghtgreenish-grey muddy sandstone (grey wacke) and shale(argill ite) (Fig. 13a, b), interpreted as a proximal turbiditesuccession deposited on a submarine fan (Laird 1972; Laird& Shelley 1974). It has a uniform and highly quartzosecomposi tion (Nathan 1976a; Roser & Nathan 1997), wi thabundant detrital quartz, minor sodi e plagioclase, andscattered volcanic and sedimentary rock fragments.

Figure 13 Typical exposures of Greenland Group on the coast north of Greymouth.

(a) Interbedded thick-bedded greywacke (dark brown) and argi llite (grey) north of Seventeen Mile Bluff.Photo: S. Nathan

(b) Interbedded greywacke and argillite on the south side of Fourteen Mile Bluff, with bedding dipping about 70° south(right). Argi ll ite beds have a distinct, almost vertical fracture cleavage. This appears to be an axial plane cleavageassociated with tight folding . An anticline axis, with a steeply dipping axial plane, is mapped a few hundred metresnorth (left) of the photograph (Nathan 1978a).

Photo CN43288/4: D.L. Homer

II

Photo: $. Nathan

Photo: M.S. Rattenbury

Figure 14 Gneissic rocks of the Buller terrane

(a) Orthogneiss (Okari Granite Gneiss, Dkn) interlayered with paragneiss (Pecksniff Metasedimentary Gneiss, Sgp)and intruded by a granitic dike on the coast north of Fox River.

(b) Well-segregated Devonian blotite±muscovite±garnet orthogneiss (Dog) with locally developed mylonitisation.Base of Mt Elliot range front near the Ahaura River.

(c) Incipiently mylonitised orthogneiss from Fraser Complex (Sf). Nearby this gneiss has been intruded by basaltic andlarnprophyre dikes that have in turn been mylonitised. Doctor Creek, upstream from Smith Gorge.

Photo: M.S. Rattenbury

12

Only a single fossil locality within the Greenland Group isknown. Graptolites from the Waitahu River ind icate anEarly Ordovician age (Cooper 1974).

The Greenland Group is closely to tightly folded with awell developed penetrative axial plane cleavage (Fig. 13b).The strike of the beds and fold axial planes is SE at MtGreenland and ESE on the coast north of Greymouth, butchanges to NNW on the eastern side of the Paparoa Range(Nathan 1978a) and N to NEat Lyell and Reefton(Gage 1948). It is not clear whether the cleavage fonnationand difference in orientation result from more than onedeformation episode.

Adams and others (1975) obtained K-Ar ages on GreenlandGroup argillites. The oldest ages, around 440 Ma, suggesta Late Ordovician to Early Silurian age for a widespreadlow-grade (chlorite zone) metamorphic event associatedwith deformation and cleavage formation (GreenlandTecton ic Event). Younger granitoid plutons thal intrudethe Greenland Group are surrounded by aureoles (from 0.5to 2 km wide) of dark grey biotite hornfel s.

Paragneiss and associated rocks

The Pecksniff Metasedimentary Gneiss (6gp, Nathan1978b) in the Paparoa Range and the Victoria Paragneiss(6gv, Tulloch 1978) of the southern Victoria Range arequartzose metasedimentary rocks containing biotite andsome garnet. The paragneisses have psammitic and peliticbands typically several centimetres thick with leucosomesof feldspar, rare calc-silicate bands (Fig. 14a), and locallywith migmatite textures indicative of partial melting (White1994). They are geochemically similar to the GreenlandGroup (Roser & Nathan 1997) and are generally acceptedas more highly metamorphosed equivalents (Laird 1988;White 1988; Ireland 1992). Metamorphism to upperamphibolite facies (s il limanite-grade) occurred around360-370 Ma (Late Devonian), based on monazi te U-Pbgeochronology (Ireland & Gibson 1998). Garnet-bioti teparagneiss (8pg) from the southern Victoria Range has anunknown but pre-Devoniandepositional protolithage, andrecords both Devon ian and Cretaceous metamorphism(Ireland & Rattenbury unpublished data 200 I).

In the Paparoa Range the paragneiss (with minor associatedorthogne iss) has a tectoni c/metamorphic foli ation thatgenerally strikes north. Sub-horizontal myloni tic foli ationoccurs in several areas (Shelley 1970) and is associatedw ith a mid-Cretaceous detachment fau lt. The fault hasdisplaced a cover sequence of lower grade, upper crustalrocks, including Greenland Group, from a higher grademetamorphic core complex comprising the gneisses andmid-crustal plutonic rocks (Tulloch & Kimbrough 1989).Th e geometri ca l re lation ships between low -gradeGreenland Group and upper amphibolite fac ies gne issesof the southern Victoria Range have been compli cated byCenozoic fau lting. Thejuxtaposition of low-grade and high­grade rocks in the Grey River is further evidence for adetachment faul t/metamorphic core complex (di scussed onp. 19).

Paragneiss OCcuITi.ng fruthersouth between the Alpine Faultand the Fraser Fault contains a metapeli tic assemblage ofsillimanite and kyanite in association with gru'net and biotite(Mason & Taylor 1987; Rattenbury 199 1; Waight andothers 1997). lnterlayered wi th the metapelitic paragneissare horn bl e nd e- plag ioc la se± ga rne t amphibolit eorthogneisses deri ved from igneous components such asmafic sill s , fl ows or tuffaceous horizons. These gneisses,with migmatitic gneiss , orthogneiss and granitoid rocks(Sf) ha ve been variabl y mylonit ised (Sfm) and arecollecti vely named Fraser Complex (Rattenbury 1991),whi ch here inc ludes rocks described as Granite Hi llComplex by Waight and others (1 997). The metapel iticg ne iss has z irco n age di strib utio ns s ugge stin g adepositional age of early Paleozoic (Ireland 1992), but alsorecords intense metamorphism in the Late Devonian andEarly Cretaceous (Ireland & Rattenbury unpublished data200 J) . Both Devonian and Cretaceous emplacement agesare inferred for the various components of FraserComplexorthogneisses.

Devonian sedimentary rocks

The Devonian Reefton Group (De) occurs as fi ve smalloutliers, all with faulted contacts with the older GreenlandGroup. Eleven units have been differentiated withi n thequartzose sandstone (quartzite), limestone and mudstone(shale) sequence, which is about 1500 m thick. It is inferredto have been deposited in shallow marine beach to she lfenvironments (Bradshaw & Hegan 1983; Bradshaw 1995).

The Reefton Group contains a shell y fauna dominated bybenthic organi sms that are part icularly abundant in thelimestone and mudstone units. Studies of the macrofaunaindicate an Early Devonian age, with some uncertaintyabout whether the fauna is Pragian or Emsian (Bradshaw1999).

Sandstone boulders containing an Early Devonian faun asimilar to that at Reefton occur in g lacial outwash nearLake Haupiri , but no outcrops have been found (Johnstonand others 1980).

Takaka terrane

Cambrian to Ordovician volcanic and sedimentaryrocks

The Paleozoic sedimentary rocks of the Takaka terranenear Springs Junction are di vided into the Early to MiddleCambrian volcanogenic De vi l River Volcanics Group, thesedimentary Haupiri Group, and the Late Crunbrian to LateOrdovic ian carbonate-rich Mount Arthur Group. A smallsliverof greenschi st derived from gabbro, dolerite, and/orvolcaniclastic sedimentary rock (Fanner J967) is correlatedwith the Devil River Volcanics Group (€d) of northwestNelson (Rattenbury and others 1998; Monker & Cooper1999). Dolomitic mudstone and ankerit ic sandstone with

Tectonic history of the Buller and Takaka terranes prior to amalgamation

Buller terrane rocks were deposited in Ordovician time adjacent to a continental landmass inferred to have beenthe Australo-Antarctic segment of Gondwanaland (Cooper 1979, 1989). Cambrian rocks of the Takaka terraneformed on, and adjacent to, a volcanic island arc/back arc setting (Miinker & Cooper 1995; Roser and others1996; Wombacher & Miinker 2000). The histories and tectonic sellings of the two terranes suggest that theywere originally a considerable distance apart, perhaps hundreds of kilometres (Cooper 1989). The Late Cambrianto Devonian passive margin part of the sequence was previously thought to have been deposited conformably onthe arc-related part of the Takaka terrane (Grindley 1980; Coleman 1981; Cooper 1989). The recognition of thewidespread Late Cambrian Balloon Melange Event in northwest Nelson, however, may indicate a significanttectonic contact. Although they are here retained as parts of the one terrane it is possible that the passive marginpart of the sequence is allochthonous (Cooper 1997).

Amalgamation of the two terranes post-dates deposition of the Early Devonian Baton Formation (Cooper 1989;Bradshaw 2000), but pre-dates emplacement of the Late Devonian granitoids (Muir and others 1996b) and istherefore taken as Early to Middle Devonian.

The Anatoki Fault forms the boundary between the Takaka and Buller terranes. South of Maruia, the fault isinferred to have been offset 5 km by a later strike-slip fault. The two terranes were juxtaposed by substantiatstrike-slip movement along the Anatoki Fault in the Early-Middle Devonian (Jongens 1997). In northwes(Nelsonthe Anatoki Fault also underwent Early Cretaceous ductile dextral strike-slip, followed by brittle deformation.

13

14

minor monomict conglomerate (€hr), polymict pebble­granule conglomerate (€ha), and grey laminated dolomiticmudstone and sandstone with abundant interlayered felsicvolcanic rocks (€hh) are cOITelated with the Haupiri Groupof northwest Nelson.

The Mount Arthur Group in the Springs Junction area(Bowen 1964) is represented by the Sluice Box Limestone(ems) and the Alfred Formation (emw) of Fauner (1967)(see also Cooper 1979). The Sluice Box Limestone is thelateral equivalent of the Arthur Marble I and SummitLimestone in northwest Nelson and is composed ofmainlyrecrystallised grey limestone and si li ceous lime­stone (Fig. 15). Conodonts, trilobites and inarticulatebrachiopods indicate an age range of Late Cambrian toMiddle Ordovician (Cooper 1989). The overlyi ng AlfredFormation is the equivalent of the Wangapeka and Baldyformations in west Nelson and consists of siltstone andminor quartz sandsLOne with graptolites of Late Ordovician(Gisbomian) age (R.A. Cooper, pers. comm . 200 I ).

The Haupiri Group rocks around Springs Junction areseparated from the structurall y overlying and youngerMount Arthur Group rocks by a detachment fault (R.A.Cooper, pers. comm. 200 I). The whole succession has beentightly folded into an an[ifoun and cut by later faulting.The finer grained rocks are commonly cleaved.

Late Devonian to Early Carboniferous intrusive rocks

Voluminous potassic biotite granitoids of the KarameaSuite fonn the bulk of the Karamea Batholith that extendsfrom west Nelson southwards into the Greymouth map areaalong the Victoria and Brunner ranges (Mu ir and othersI 996a). Isolated plutons of Karamea Suite granitoids al sooccur in the Paparoa Range and in the southwest.

Figure 15 Quarry in SluiceBox Limestone (Mt ArthurGroup), about twokilometres southwest ofSprings Junction . Most ofthe outcrop is forest­covered, but the limestoneforms a distinctive ridge thatcan be traced for severalkilometres. At this localitylimestone is recrystallisedto marble by the thermaleffects of a nearby pluton.

Photo CN4349217: DL Homer

Muir and others (I996b) recorded a group ofU-Pb SHRIMPages on Karamea suite granites that were statisticallyindi stinguishable at 375 ± 5 Ma, as well as two youngerdates at -330 Ma. Subsequent dati ng of additional sampleshas ind icated a spread of ages in the range 375-315 Ma,with a concentration of ages at about 370 Ma (Fig. 16a;A. J. Tulloch, pers. comm. 200 I ).

The most widespread granitoid lithology is muscovite­biotite granite (Dkg; Fig. 17a), which includes a variety oftextural types, some of which have been mapped asseparate plutons (e.g., Roder & Suggate 1990; Tulloch1978). A distinctive pluton ofleucocratic muscovite±biotitegranite with large white tabular megacrysts of K-feldspar(Dunphy Granite, Dkm) occurs on the western side of theBrunner Range. Highly foliated biotite-muscovite granite­gneiss in the Paparoa Range is mapped as Okari Granite­Gneiss (Dkn). Although the dominant lithology in theNelson area is a distinctive, coarse-grained porphyriticgranite containing large pink megacrysts of potash feldspar(Dkp), this lithology occurs on ly as a single small plutonnear the northwest edge of the Greymouth map.Two smallplutons, both foliated biotite granite with large K-feldsparmegacrysts, have U-Pb ages less than 350 Ma, and aremapped as Ckg (Fig. 17c).

Biotite-bearing granodiorite and tonalite (Dkt & Ckt) aresubordinate to granite. A few small areas of hornblendediorite (Ckd; Fig. 17b) occur in the Victoria Range wherethey intrude granitic rocks.

Undifferentiated orthogneiss (Dog) in the southern Victoriarange (Fig 14b) is probably Late Devonian in age basedon preliminary U-Pb zircon and monazite geochronology(Ireland & Rattenbury unpub li shed data 200 I ). Someorthogneiss within the Fraser Complex (Fig. 14c) is of LateDevonian to Early Carboniferous age (Jreland & Rattenburyunpubli shed data 200 I).

Figure 16a

His togram show ingdistribution of all avai lableU-Pb ages for granitoidrocks , illustrating thatthere is a clear bimodaldistribution .

35,!g

.~ : .~c

30 C:'-I e""'" ~'2

VI i:l~ "',-\I) ~ I U ~ ~'" 25'"

,.0 ,0,- 20

,::::l ,- I0

15 I~

\I) ,.0 IE 10 I::lZ I,

5 I,0

,

0 100 200 300 400 500

U-Pb ages (Ma)

Figure 16b

Typical variation diagram(Si0

2vs Sr) , us ing

chemical analyses of allthe rocks shown inFig. 16a. Geochemistrycan aid the distinctionbetween different suites,bu t is not completelyunambiguous.

..... French Creek GraniteIo Rahu SUite Cretaceous• Separation POint SUite

... Rocky Creek Granite

• Karamea Suite } Devonian toCarboniferous

••••

•

•

Eis: 1000 .~

(/)

Distinction between granitoid rocks of different ages

The mountains northwest of the Alpine Fault are largety composed of granitoid rocks. Tulloch (1988)dislinguished three batholiths (Karamea, Paparoa and Hohonu) on geographic grounds. We consider that thegranitoid rocks are essentially contiguous, with satellite intrusions into country rock, and therefore prefer toinclude them all in the Karamea Batholith as was done in the adjacent Nelson map (Ratlenbury and olhers1998).

Radiometric dating indicates that granitoids in the Greymouth map area were emplaced in two distinct timeperiods: Late Devonian to Carboniferous and Early Cretaceous (Fig. 16a). One of the major challenges inpreparing this map has been to consistently distinguish between granitoids ofdifferent age groupings. There arenow approximately 50 U-Pb ages on granitoid ptutons within or immediately adjacent to the QMAP Greymouthsheel (Kimbrough & Tulloch 1989; Muir and others 1994; Muir and others 1996b; Muir and others 1997; Tulloch1983; Waight and others 1997; AJ Tulloch, pers. comm. 2001), and these have been used as the basis for agediscrimination. Most of the Late Devonian to Early Carboniferous rocks are S-type granitoids, while most of theEarly Cretaceous granitoids are t-types, and it has therefore been possible to supplement the dating bygeochemical criteria (Fig. 16b; see Tulloch & Brathwaite 1986) and measurement of magnetic susceptibility(Tulloch 1989). There are, however, still uncer1ainties, and more radiometric dating is required.

The granitoids have been grouped into suites defined by age and composition. In order to generalise informationat 1:250000 scale, individual mapped plutons within each suite have been combined into similar granitoid types- for example, granite, granodiorite/tonalite, and diorite (see map legend).

15

16

Figure 17 A selection of U-Pb dated granitoid rocks of the QMAP Greymouth area. Although most plutons havedistinctive lithologies, the photographs illustrate the difficulty of distinguishing between Devonian-Carboniferous andCretaceous granitoids without supporting geochemistry and radiometric dating.

(a) Two dated Devonian granites, mapped as Dkg. Medium-grained biotite-bearing Whale Creek Granite intruded byfine-grained phase of the O'Sullivans Granite (Roder & Suggate 1990; Muir and others 1996b). Buller River nearWhale Creek.

(b) Early Carboniferous biotite diorite (Ckd; Tobin Diorite of Tulloch 1978). Rahu River.(c) Foliated granite with large K-feldspar megacrysts (Ckg ; Foulwind Granite of Nathan 1976b), dated as Early

Carboniferous (Muir and others 1996b). Cape Foulwind, near Westport.(d) Early Cretaceous Darran Suite biotite granite (Kdg; Rocky Creek Granite of Tulloch 1978) from near Rahu Saddle.(e) Early Cretaceous Rahu Suite biotite-hornblende granodiorite (Krt) intruded by granitic dike. Upper Grey River near

Robinson River confluence.(f) Megacrystic K-feldspar hornblende-biotite granodiorite (Early Cretaceous Separation Point Suite, Ksy) with well

developed foliation , locally mylonitic. Snow Creek, tributary of the Upper Grey River.

PERMIAN10EARLYCRETACEOUS

West ofthe Alpine Fault

Triassic-Jurassic sedimentary and volcanic rocks

A small area of early Mesozoic rocks near Kirwans Hill,northeast of Reefton, has particular significance becauseof its close similarities with Gondwanaland sequences inAustralia and Antarctica (Mortimer and others 1995;Mortimer & Smale 1996).

The Topfer Formation (Top), covering an area of only 2km2

, consists of massive brown volcaniclastic sandstone,with rare beds ofpebble conglomerate and coal. Althoughrelationships with older rocks have not been seen, the unitcannot be more than a few hundred metres thick.Petrographic studies suggest a continental, magmatic-arcsource area, possibly similar to that ofthe Murihiku terrane.Pollen indicates ages ranging from Middle to Late Triassic(Smale and others 1996).

The Topfer Formation is intruded by steeply dipping sillsoflow-Ti tholeiitic basalt and dolerite (Kirwans Dolerite,Jkd). The dolerite has very close geochemical and isotopicaffinities with the Ferrar magmatic province ofAntarctica(Mortimer and others 1995). K-Ar ages range from 151-172Ma, indicating a Middle Jurassic age.

Early Cretaceous granitoid rocks

Early Creta<;:eous granitoid rocks make up a significantpart of the Karamea Batholith in the Paparoa, Victoria andHohonu ranges. Although there are some differences inhand-specimen from the older Devonian/Carboniferousgranitoids that crop out in the same areas, distinguishingplutons of different ages requires geochronology aided bygeochemistry (see text box on p. 15).

Most of the Cretaceous granitoids are included in the RahuSuite (Tulloch 1983; Tulloch & Brathwaite 1986), which,as used here, incorporates the Hohonu Suite ofWaight andothers (1998aj. The rocks are typically calc-alkaline I1S­type granitoids. The dominant lithology is equigranularbiotite or biotite-muscovite granite (Krg), but there arealso several large plutons ofleucocratic muscovite granite(Krm), typically with minor biotite. Biotite granodioriteand tonalite (Krt) are less common, but several small, high­level plutons of these compositions are chilled againstcountry rock in the north ofthe Lower Buller Gorge (BerlinsPorphyry of Nathan 1974a). There are also several smallareas of hornblende diorite (Krd).

U-Pb dating ofRahu Suite plutons (Muir and others 1994;Muir and others 1997; Waight and others 1997;A. J. Tulloch, pers. comm. 2001) indicates that the RahuSuite was emplaced in a short period arouild 110 Ma (withinlimits of 115-105 Ma), at a range of depths (Tulloch &Challis 2000).

The Separation Point Suite occurs mainly in the SeparationPoint Batholith in the Nelson map area (Rattenbury andothers 1998) as well as forming a number ofisolated plutonsin the Greymouth map area. They are distinctive Na-richalkali-calcic granitoids with high Sr and SrlY ratios, oftenwith,visible titanite in hand specimen. The main lithologyis equigranular biotite and biotite-hornblende granite(Ksg), with minor granodiorite and tonalite (Kst) andhornblende diorite (Ksd). A linear belt of granite­granodiorite with large K-feldspar megacrysts (MaceyGranite ofTulloch 1978) crops out along the western sideofthe Victoria Range, and is locally mylonitised (Ksy; Fig.17f). U-Pb dating indicates that the Separation Pointplutons were emplaced between 126 and 109 Ma (slightlyolder than, but overlapping with, the Rahu Suite).

An isolated pluton ofbiotite granite in the eastern VictoriaRange, mapped by Tulloch (1978) as Rocky Creek Granite(Kdg; Fig. 17d), gives a U-Pb age of 132 Ma (A. J. Tulloch,pers. comm. 2001). The granite has calc-alkaline I-typeaffinities more typical of the Darran Suite in northernFiordland (Muir and others 1998), with which it is tentativelycorrelated. A small area ofbiotite-hornblende diorite nearSprings Junction (Jdd) is also included in the Darran Suite.

Early Cretaceous sedimentary rocks

Mainly coarse-grained, non-marine sedimentary rocks ofthe Pororari Group (Ko) are preserved in partly fault­bounded blocks in and around the Paparoa Range. Thedistinctive maroon colour of many outcrops probablyindicates a non-marine oxidising environment, but doesnot occur in all places. The basal contacts with older rocksare mostly faulted, but locally unconformable.

The Pororari Group contains clasts of nearby basementlithologies, indicating local derivation. Pollen and sporesshow it is of late Early Cretaceous age (Albian; Raine 1984),implying that deposition was immediately afte~ graniteemplacement and uplift (Adams & Nathan 1978; Tulloch& Palmer 1990).

The dominant lithology within the Pororari Group ispoorly-sorted, matrix-supported breccia and breccia­conglomerate, locally with outsize clasts up to 0.3 m indiameter, in a coarse-grained sandy matrix (Hawks CragBreccia, Koh; Fig. 18).

In the Lower Buller Gorge four members or facies of theHawks Crag Breccia have been recognised locally (Beckand others 1958; Nathan 1978b) based on variations inclast lithology (either Greenland Group or a mixture ofGreenland Group and granite). The sequence is interpretedto be a series of overlapping alluvial fans from different,local sources. In other areas, the breccia consistspredominantly ofclasts of Greenland Group or granite fromnearby sources.

17

18

Figure 18 Typical lithologies of the Hawks Crag Breccia (Koh).

(a) Hawks Crag in the Lower Buller Gorge, the type locality, consists of very thick massive beds of greywacke-derivedbreccia, dipping about 40' west (right). The moss-covered cliff drops straight into the river, so it has been necessaryto excavate a narrow cutting for the road.

(b) Hawks Crag Breccia exposed in the road cutting at Hawks Crag. The clasts here are entirely hornfels derived fromthe Greenland Group, and the largest is about 0.5 metres long. Rapid uplift and erosion of the hornfels occurredin Albian time.

(c) Hawks Crag Breccia at Fox River mouth is composed of thick beds containing granite clasts in a sandy matrix. Apollen sample from this local ity has been dated as late Albian , typical of other samples dated from the Hawks CragBreccia (Raine 1984).

Photos: S. Nathan

In addition to the Hawks Crag Breccia, the Pororari Groupcontains fluvial , sandstone-conglomerate sequences andlocaJ lacustri ne beds containing interbedded debris flowsand turbidites. A number of local units have been named indifferent areas (Laird 1988; Nathan 1978b), buton this mapthey are mapped as undifferentiated Pororari Group. In thePunakaiki area, Laird (1995) interpreted the sediments as afan-delta sequence which built out into a lake that occupieda rapidly subsiding half-graben.

Quek (1976) descri bed a narrow, fault-bounded sequencein the Brown Grey River which is dominantly greysandstone with carbonaceous lenses. It includes local red­stained lenses and is tentatively incl uded in the PororariGroup, although it is so far undated .

I n the Lower Buller Gorge, Sti t ts Thff M ember (Kos)comprises light grey rhyolitic tuff with minor carbonaceous

shale (Nathan 1978b), and forms the basal 60 metres of thePororari Group. V-Pb dating gives an age of 101 -J02 Ma(Muir and others 1997) .

C retaceous dikes and high level intr usions

Thin dikes and si ll s of lamprophyre, basalt and trachyte,generally less than I metre thick, intmde the Pororari Groupand older rocks, including mylonite withi n the FraserComp lex (Nath an 1978b; Huot & Nath an 1976;Rattenbury 1987). K-At· ages range from 90-78 Ma (Adams& Nathan 1978) .

In the Hohonu range a di ke swarm which c uts thegranitoids incl udes lamprophyre. doleri te and phonolite.It is thought to be genetically related to, and the same ageas, the alkaline syenogranite mapped as F rench CreekGranite (Kfg) (82 Ma; Waigh! and others 1998b).

Early Cretaceous structural development

Geological and geochronological evidence indicates that emplacement of granitoid rocks, uplift and erosion,took place in a short period between 115 and 95 Ma (Adams & Nathan 1978; Spell and others 2000). This is alsothe time when high-grade metamorphic and granitoid rocks were juxtaposed immedialely beneath low-gradeGreenland Group and cross-cutting plutons by movement on low-angle detachment faults, forming metamorphiccore complexes (Tulloch & Kimbrough 1989). Rapidly uplifted basement rocks provided source material for thePororari Group, which is now preserved as faulted blocks around the margins of the core complex in thePaparoa Range (Fig. 19).

The geological map gives a plan view of the distribution of rocks from different structural levels. Cross-sectionsA-A' and 8-8' provide an interpretation of the possible subsurface extrapolation of low-angle detachment faults.

The tectonic and magmatic events are together inferred to record the end of subduction and terrane accretion,changing abruptfy to continental extension preceding the break-up of Gondwana (Waight and others 1998a).

Cretaceousgranitords

North

~--

LOWERPLATE

Pororari Grouperosion

;::,....

paragneiss

South

Figure 19 Diagrammatic cross secl ion through the metamorphic core complex in the Paparoa Range. The lower platewas uplifted along shallOW-dipping mylonitic detachment taulls displacing the upper plate of early Paleozoic GreenlandGroup and some small granitoid intrusions. The extensional deformation also resul ted in the formation of fault­bounded basins in Ihe upper plate that were rapidly filled with Pororari Group terrestrial sediments derived from theeroding lower plate. Modified after Tulloch & Kimbrough (1989).

t9

20

Figure 20 Typical sedimentary lithologies within the Rakaia terrane and Esk Head belt.

(a) Thin-bedded alternating sandstone and mudstone, a typical turbidite association(Tt). State Highway 73, near Bealey Bridge. Photo CN43424116: D.L. Homer

(b) Thick-bedded sandstone, with an interbedded package of alternating sandstoneand mudstone (Tt). East branch of the Poulter River. Photo: M.s. Raffenbury

(c) Lenticular boudinaged sandstone and mudstone, a weakly transposed precursorto broken formation (Tt) . Upper Wilberforce River near Browning Pass. Photo: K.R. Berryman

(d) Typically knobbly broken knocker topography associated with Esk Head beltmelange (Tem) with purple-red coloration to right due to interlayered red mudstoneand volcanogenic rocks. Looking towards Esk Head on the Puketeraki Range. Photo: M.J. Isaac

(e) Typically strongly sheared and transposed red and green mudstone and interlayeredvolcanogenic rocks within Esk Head belt melange (Tem). North Esk River. Photo: M.J. Isaac

East ofthe Alpine Fault: Rakaia terrane

Rakaia terrane fonns part ofthe Torlesse composite terranewhich incorporates the fonner Torlesse Supergroup andranges in age from ?Late Permian to Early Cretaceous.Rakaia terrane is separated from the neighbouring Pahauterrane by the Esk Head belt, which is further describedbelow (p. 22).

Late Triassic sedimentary rocks

Grey, indurated quartzo-feldspathic sandstone (greywacke)and mudstone (argillite) (Tt) comprise much of the easternSouthern Alps within the Greymouth map area. Thesandstone is typically poorly to moderately sorted, fine­to medium-grained, and contains abundant lithic clasts of

. felsic igneous and sedimentary rocks. Sedimentarylithotypes are dominated by (a) thick to very thick, poorlybedded sandstone, and (b) thin- to medium-beddedalternating sandstone and mudstone (Fig. 20). Thesandstones are commonly well-graded and showsedimentary structures such as cross-bedding, solemarkings and ripples. Both lithotypes were fonned byturbidite deposition in a submarine fan environment.

Thick mudstone beds, with or without thin- to medium­bedded sandstone, are less common in the map area.Conglomerate occurs sparingly, and is more obvious inriver boulders than in outcrop. The clasts range from sub­angular to well rounded and are dominated by sandstoneand mudstone, with lesser amounts of felsic igneous andquartz-rich metamorphic rocks.

Coloured mudstone is a minor but significant rock type inthe map area. Typically, dark red to brown, or pale greento grey mudstone occurs in bands with dark grey mudstoneand sandstone up to several hundred metres thick (Ttv).Rare occurrences of basalt and limestone are found inassociation with the coloured mudstone. Colouredmudstone may have fonned by very slow, clastic-poordeposition (Roser & Grapes 1990) rather than by anincreased volcanogenic component. Bands of colouredmudstone are one ofthe few distinct marker horizons withinthe Rakaia terrane that can be used to map regionalstructural trends. Coloured mudstone is commonlyassociated with zones of layer-parallel shearing whichlocally inten.sifies into broken formation (Ttm). Theshearing probably results from low rock strength ratherthan tectonic incorporation of "exotic" components inmelange.

Late Triassicfossils are relatively abundant in the vicinityof Arthur's Pass, and include Monotis with fewerTerebellina mackayi, and other bivalves, crinoids,bryozoans, fish vertebrae and trace fossils (Campbell &Warren 1965; Cave 1982). Monotis is also present in theTrent River area (Wellman and others 1952).

Tectonic shearing is common throughout the Rakaiaterrane, and the zones are usually either parallel to beddingor have transposed bedding parallel to the shearing. The

zones commonly change in width from several hundredmetres to less than a metre along strike and are difficult tomap over extended distances.

Late Triassic semischistose and schistose rocks

West of the main divide the Rakaia terrane rocks becomeprogressively metamorphosed into semischist and schisttowards the Alpine Fault. The metamorphosed rocks havebeen mapped in textural zones (IIA, lIB, III, IV), using aclassification that is now widely accepted in New Zealand(see box on p. 22; also Fig. 21).

Incipiently cleaved to strongly transposed alternatingsandstone and mudstone and thick sandstone semischist(Tt, textural zones IIA and lIB) comprise a zoneapproximately 6-8 km wide in the south that thins to about2 km in the northeast. This zone is also slightly oblique tothe Alpine Fault trend. The intensity of cleavage andfoliation development increases to the northwest and isgradational into schist.

Laminated and segregated t.z. III-IV schists occur in anortheast-trending, 2-10 km wide belt immediatelysoutheast of the Alpine Fault. Pelitic and psammiticgreyschist are inferred ~o be metamorphosed quartzo­feldspathic sedimentary rocks dominated by alternatingsandstone-mudstone sequences. The schists grade fromquartz-albite-muscovite-chlorite mineral assemblages tobiotite-albite-oligoclase and garnet assemblages towardsthe northwest.

The westernmost part of the schistose rocks includes ahigher proportion ofpelitic schist and mafic metavolcanicgreenschist layers, and is correlated with the Aspiringlithologic association (Ya), a subdivision of the Rakaiaterrane recognised in northwest Otago (Craw 1984;Turnbull 2000) and in Marlborough (Mortimer 1993b;Begg & Johnston 2000). In the Greymouth map area theserocks also include the Pounamu Ultramafics (Yap)comprising serpentinite, gabbro and metabasite inassociation with pelitic schist and rare limestone and chert.These ultramafic rocks occur in lenses up to 200 m wideand 1 km long, collectively aligned along a belt betweenthe Kokatahi and Maruia rivers, on a slightly oblique trendto that ofthe Alpine Fault. These metamorphosed ultramaficrocks host pods of highly valued greenstone (also knownas pounamu or nephrite; see p. 42).

Schist of the Aspiring lithologic association becomesincreasingly mylonitised close to the Alpine Fault (YTm)and the mylonite zone has a maximum width ofapproximately 2 km near the southern map boundary. Themylonite zone narrows to the northeast, and is probablytruncated by the Alpine Fault near the Blue Grey River.Greenschist (YTg) and ultramafic (YTv) bands are mappedwithin the mylonite zone.

The eastern part of the belt of schistose rocks is dominatedby quartzofeldspathic greyschist (Tt). Rare greenschistbands occur near the boundary with the Aspiring lithologic

21

association. The boundary between the greyschi st andthe Aspiring lithologic association is inferred to be a faultthat post-dates textural metamorphism. A local reversal ofthe regional westward increase in textural metamorphismis apparent at the boundary where the western pe lit ic andmafic/ultramafic schist is t. z. lIB, and the eastern greyschistis t. z. III .

A Late Triassic depositional age fo r the semi schist (thesame as the unmetamorphosed part of the Rakaia terrane)is indicated by Torlessia in the lower grade rocks of theArahura River (Campbell & Warren 1965).

Structure of Rakaia rocks

The structure of the Rakaia terrane is complex and difficultto resolve due to multiple fo ld ing events, a general lack ofmarker horizons, limited age contro l and widespreadfau lting. In general, bedding trends north to northeast andconverges to northeast closer to the Alpine Fault. Thereare multi ple phases of foliat ion development within thesemischist and schist refl ecting a protracted defo l111ationaland metamorphic history. Schist foliation trends northeast,sub-parallel to the Alpine Fault. Some macroscopic fo ldsare preserved in both the schi stose and non-schistoserocks, commonJ y with one and rarely botJllimbs oveltumed.Mesoscopic folds are rare in the nOll -schistose rocks.

Esk Head belt

Late Jurassic - Early Cretaceous melange

Thick to very thick, poorly bedded , and locally shearedsandsto ne (Te) and strongly sheared melange (Tern)comprise the Esk Head belt in the southeast of theGreymouth map area. At Esk Head at the northern end ofthe Puketeraki Range, the distinctive knocker topographyis characteristic of melange (Fig. 20d). The knockersty pically consist of indurated, partly silicified massivesandstone and they are enveloped in a strongly shearedmatrix of broken sandstone and mudstone. In addition themelange contains lensoid tectonic clasts of sandstone,coloured mudstone, basalt and limestone (Fig. 20e). Manyof these rock types are simi lar to those found in the Rakajaterrane and therefore are not strictly exotic components.Late Triass ic M anolis shells have been found in limestoneblocks and clasts with in the melange (B radshaw 1973) atEsk Head. Tn addition, however, Late Jurassic belemnitesand Early to Late Jurassic radiolari a occur within the EskHead belt beyond the map sheet boundary (Silberling andothers 1988), co nstra inin g the age of defo rm at io n!emplacement to post-Late Jurassic.

The western boundary with Rakaia terrane rocks is welldefined and mappable to within 100 m in places. The eastem

22

Textural zones

Textural subdivision is a useful method for mapping low grade metamorphic rocks, and has been widelyapplied (Bishop 1974; Turnbull 1988; Mortimer 1993a). Textural zones (t.z.) separated by "isotects" areindependent of metamorphic facies boundaries, and can cut across isograds or foliation.

The application of the textural zonation system established by Hutton & Turner (1936) and Bishop (1974) hasbeen revised by Turnbull and others (2001). Characteristics of these revised textural zones are summarised:

t.Z. I: Rocks retain their sedimentary (primary) appearance. Detrital grain texture is preserved, and bedding(when present) dominates outcrops. Metamorphic minerals may be present, but are very fine-grained «75 11m),and there is no foliation.

t.Z. flA: Rocks retain their primary appearance and sedimentary texture, although detrital grains are flattened.Metamorphic minerals are fine-grained «75 11m), and impart a weak cleavage to sandstones. Mudstones haveslaty cleavage. Bedding and foliation are equally dominant in outcrop. Rocks are termed semischist.

t.Z. fiB: Rocks are well foliated, although primary sedimentary structures may still be seen. Bedding is transposedor flattened. Clastic grains are flattened and metamorphic overgrowths are visible in thin section. Metamorphicmica grain size is still <75 11m and metamorphic segregation appears. Mudstone is changed to phyllite; meta­sandstone is well foliated and forms parallel-sided slabs. Rocks are termed semischist.

t.Z.Iff: Planar schistosity identified by metamorphic micas is developed in all rocks. Bedding is barelyrecognisable, and is transposed and parallel to foliation. Clastic grains may still be recognisable in sandstones,but are recrystallised and overgrown, and metamorphiC segregation laminae are developed. Rocks are termedschist. Quartz veins develop parallel to foliation, or are rotated and flattened. Metamorphic micas are typicallyabout 75-125 11m long (very fine sand size).

t.z. IV: Primary sedimentary structures and clastic grains are destroyed at a mm-cm scale, although primarysedimentary units may be discernible in outcrop. Schistosity tends to be irregular due to porphyroblast growth.Metamorphic mica grain size is 125-500 .urn . Schistosity and segregation are ubiquitous and rocks are termedschist. Quartz veins are abundant in most lithologies.

boundary of the melange is 110t well defined and rocks tothe east show generally less shearing in more localisedzones, but the melange component is up to 10 km wide.The melange has a steeply dipping fabric that is close toparallel to the bedding within less deformed Rakaia ten-anerocks to the west.

The Esk Head belt is widely believed to represent thetectonic suture between the contrast ing Rakaia and Pahauterranes and extends from Canterbury to Marlborough(Si lberling and olhers 1988) .The belt isoffset by the AlpineFault and reappears in the lower North Island through theRimutaka, Tararua and Ruahine ranges (Begg & Johnston2roJ).

Figure 21 Progressive development ofschistosity on the western side of the SouthernAlps.

(a) Subhorizontal thin-bedded alternatingsandstone and mudstone (Tt), withincipient steeply dipping cleavage (1.z. IIA).Northwest of Newton Saddle.

PhotO: K. R. Berryman

(b) Strongly transposed and fo liated west­dipping semischist (Tt , I.z. liB) on theNewton Range west of Mt Newton.

Photo: J. Adams

(c) Strongly foliated and segregatedI.z. III schist (Va) transitional to schistmy lon ite (VTm). Approximate ly2.5 km southeast of the Alpine Fault inCamp Creek on the northwest flanks of theAlexander Range.

PhotO: M.S. Rattenbury

23

l

Figure 22 Gently dipping Paparoa Coal Measures (bottom half of cliff) overlain by Eocene (Brunner) coal measuresand shallow marine sandstone in the Pike River Coalfield, central Paparoa Range. View looking eastwards to theGrey Valley. Both the Brunner and Paparoa Coal Measures in this section contain thick coal seams, which have beenprospected by helicopter-supported drilling .

Photo CNI0362133: D.L. Homer

Figure 23 Light-coloured Paparoa Coal Measures exposed in a cliff on the south side of Ten Mile Stream, consistingof thick-bedded conglomerate with a few sandstone interbeds. The overlying Eocene rocks (covered with vegetation)consist of shallow marine sandstone with a thin coal seam at the base. The contact represents a period of timeduring which the Waipounamu erosion surface developed and the underlying rocks were deeply weathered. In thisview, the weathered material is the paler uppermost 10m of the Paparoa Coal Measures.

Photo: S. Nathan

LATECRETACEOUS AND TERfiARY

Late Cretaceous to earliest Pleistocene sedimentary rocksrecord the format ion and subsequent deformation oflocalised, faul t-bounded basins in response to changingtectonic stresses across the developing boundary betweenthe Australian and Pacific plates. Most time intervals fromLate Cretaceou s to Earl y Pleistocene are represented,although no single basin has a complete sequence. Thesedimentary succession locally shows marked lateral faciesand thi ckness changes as well as abrupt chan ges indepocentres and changing paleo-highs. Virtually the wholearea was subm erged be neath the sea by the lates tOligocene, with a regression and the emergence of lowhills th rough the Miocene and Pliocene. The present daymountain ranges are a latest Cenozoic feature.

T he Southern Alps, immediately southeast of the AlpineFault , did not stal1 to rise rapidly until late Cenozoic time.Although onl y two small areas of Cenozoic sedimentaryrocks are preserved southeast of the Alpine Fault in thi smap area, it is infe rred that much of Cante rbury wassubmerged during the Cenozoic (Field & Browne 1989),with maxi mum submergence during the Oligocene.

Late Cretaceous to Paleocene sedimentary rocks

Late Cretaceous to Paleocene rocks are restri cted to anarrow, NNE-trending basin (Paparoa Trough) in thecentra l part of the map area (Nathan and others 1986).Paparoa Coal Measures (Kpc) consist of a non-marineassemblage of flu vial conglomerate, sandstone, lacustrinemudstone, and lensoid coal seams (Figs 22 & 23). Drillingfor coal and petro leum exploration has defined thethickness variatio n with in the formation , indicating amaximum thickness of abollt 750 metres in the axis of thetrough. Detailed mapping within the Greymouth Coalfield(Gage 1952) showed that the Paparoa Coal Measures canbe subdivided into seven units, now mapped as members(Nathan 1978a). The key to subdi vision is the recogni tiono f three lacustri ne mudstone marker bands separatingthicker un its of coal measures (predominantly quartzo­feldspathic sandstone. with conglomerate and coal seams).The uppermost (Dunollie) member is di stinctly morequartzose towards the top, indicating increased chemicaldecomposition of less stable mineraJs as the tempo of upliftand erosion slowed in the Early Paleocene.

Basalt flows and breccia are interbedded withi.n the lowerpart of the Paparoa Coal Measures at several locaJities,and have been dated at 68-7 1Ma (Sewell and others 1988;Nathan and others 2000). They appear to be part of anepisode of latest Cretaceous basaltic volcani sm that waswidespread on the West Coast (Nathan and others 1986).

Pollen dating, summari sed by Raine (1984), shows thatmost of the Paparoa Coal Measures is lates t Cretaceous inage, but the uppermost part is Earl y Paleocene. TheCretaceous-Tertiary boundary occurs within a coal seamin the upper part of the Rewanui Member (Raine 1994;Vajda and others 2001).

Eocene sedimenta ry rocks

Tectonic acti vity recommenced in the late Middle Eocene(about 38 million years ago), with reg ional extensionleading to the fo rmation of local bas ins, many faul t­bounded, separated by areas of low-lying land. At the sametim e a g radual marin e tran sg ress io n s tarted , andprogressively inundated the whole West Coast region overthe succeeding 15 mi llion years. By the end of the Eocenethe map area had become an archipelago of low-lyingislands sunounded by shallow seas (Nathan and others1986).

The oldest Eocene sedimentary rocks are Brunner CoalMeasures (Eb) , c on s is tin g o f quart z sand s ton e,conglomerate, carbonaceous shale, and lensoid coal seamslocally up to 10m thick (Flores & Sykes 1996; Titheridge1993) . The formation is characteristically quartzose, beinglargely derived from deeply weathered, granitoid basementrocks . Having been deepl y buried in some areas, thesandstone beds are commonly silica-cemented, and thusform characteri stic bluffs and plateaus (Figs 10, 24).

The coal measures are conformabl y (and in most placesg radationall y) overlain by shallow-water sedimentaryrocks. The most widespread unit is mass ive, dark browncarbonaceous mudstone of the Ka iata Formation (Erk;Fig. 26) which locall y contains interbedded mass-flo wdeposits near Greymouth and Westport (Nathan and others1986). In some areas, the coal measures are overlain byshallow marine sandstone which has been given a varietyof local names (e.g., [sland Sandstone near Greymouth),but which are here generali sed as a single un it (Ers).

Late Paleocene - Early Eocene unconformity

Early in the Paleocene there was a general slowing in tectonic activity. Sedimentation ceased over the whole of themap area, and there is no Late Paleocene - Early Eocene stratigraphic record. This break represents a period ofwidespread peneplanation and a regional unconformity that affected much of the New Zealand region (Suggate andothers 1978), more recently named Ihe Waipounamu erosion surface (LeMasurier & Landis 1996).

Generally the rocks immediately beneath the unconformity are deeply leached, wilh the less resistant minerals suchas feldspar and biotite decomposed, leaving a residuum consisting mainlyofquartz and kaolin clay (Fig. 25). Wellman(1951) described the nature of the contact between the Paparoa Coal Measures and overlying Eocene sedimentsnear Greymouth, providing evidence for a break in sedimentation accompanied by subaerial weathering (Fig. 23).

The Waipounamu erosion surface forms a marked topographic feature in several parts of the Greymouth map area(e.g. Fig. 10). In all cases the surface has been covered by Late Eocene-Oligocene sediments, and subsequentlyuplifted and exhumed in the late Cenozoic.

'-----------------------------J 25

Figure 24 Aerial view of an opencast mine in Brunner Coal Measures (Eocene) on the top of Mt Frederick, BullerCoalfield, 1995. Approximately 20 metres of hard, cemented quartzose sandstone have been stripped off to exposethe thick coal. The Stockton plateau in the background is formed of similar quartzose sandstone, but coal only occursin local, lensoid seams.

Photo CN32454116: D.L. Homer

Figure 25 Unconformity between Brunner Coal Measures (Eocene) and deeply weathered granitoid rocks exposedon State Highway 6 south of Charleston. In some places the rocks beneath the unconformity are so deeply weatheredthat they consist of little more than kaolin clay and quartz. Locally the clay has been quarried and processed for usein sanitary ware.

Photo CN43407113: D.L. Homer

Figure 26 Gently dipping Tertiary sequence exposed on the coast east of Cape Foulwind. In the foreground light grey­brown Kaiata Formation (Late Eocene to Early Oligocene) dips about 13' eastwards. Detailed micropaleontologicalstudies show that the Eocene-Oligocene boundary occurs near the bend in the coastl ine. The cliffs in the backgroundare composed of O'Keefe Formation (Late Miocene-Pliocene), and the whole sequence is capped by 3-4 metres ofbrown ilmenite-rich sand beneath a last interglacial terrace surface.

Photo CN43418114: D.L. Homer

L

Within the Murchison Basin, at the northeast edge of themap area, the Maruia Formation (Em) consists ofcarbonaceous mudstone containing a high proportion ofthick-bedded quartzofeldspathic sandstone, with minorcongfomerate and rare coal seams (Fyfe 1968; Roder &Suggate 1990).

On the southeast side of the Alpine Fault, ves icul ar,columnar basalt and adjacent glauconitic greensand in theEsk Ri ver near Grant Stream underli e late Tert iarysedimentary rocks. This section is similar to that in theBrechin Burn 15 km farther southwest (Newman &Bradshaw 198 1). There the basalt and greensand areinferred to be Eocene (Field & Browne 1989), in the upperpart of the Eyre Group (Ee).

Oligocene to earliest Miocene sedimentary rocks

Continued marine transgression from Late Eocene into theOligocene led to the gradual drowning of the low-lyingland, and by the end of the Oligocene virtually the wholemap area was submerged. The supply of terrigenoussediment dwindled, and as a consequence Oligocenesediments are typically calcareous and limestone iswidespread. A lthough it is inferred th at Ol igocenesediments originally covered the whole map area, theirpresent limited distribution isdue to subsequent upli ft anderosion, and to a lesser extent, burial by younger sediments.Seismic exploration has shown that there is a widespread

Oligocene reflector offshore and onshore beneath lateCenozoic deposits.

Nathan ( 1974b) included all thecaleareous sedimentsovermuch of the West Coast region in the Nile Group (On),which was divided into two major facies (Nathan and others1986):(a) Platform fac ies (usually < 100m thick), consisting of

shallow-water bioclas ti c lim eston e and muddymicaceouslimestone fOOlled 0 11 arelatively stableshelf;and

(b) Basinal facies (usually> I00 m thick), predominantlymuddy limestone, massive calcareous mudstone andinterbedded calcareous sandstone and mudstone,formed in rapid ly subsiding basins.

The Platform facies, which includes numerous units thathave been distinguished in detailed mapping, is found aserosional remnants over much of the map area, mainly asbluff-forming limestone. On the coast south of Westport,limestone bluffs are one of the most striking features ofthe Paparoa ationa! Park (Figs 27-29). The Basinal faciesoccurs mainly around Greymouth, where calcareousmudstone of the Port Elizabeth Member (Onp) at thetop of the Kaiata Formation grades upwards into muddymicritic limestone of the Cobden Limestone (One).Within the M urchison Basin , at the northeastern corner ofth e map area, mass ive ca lcareous mudston e withinterbedded calc-fl ysch is mapped as Matiri Formation(Om).

27

Figure 27 Panoramic view looking eastwards over the Punakaiki area, showing the gently-dipping sheet of Oligocenelimestone that dominates the topography, with the Paparoa Range in the background. The small settlement in thecentre foreground is Punakaiki, and Pancake Rocks are in the right foreground.

Photo CN36159: D.L. Homer

28

Figure 28 Punakaiki township isdominated by cliffs of Oligocenelimestone. This small area of lateHolocene coastal plain, between thelimestone cl iffs and the sea, is oneof the few flat areas aroundPunakaiki, but is subject to naturalhazards. Because it is open to theTasman Sea, coastal erosion is anever-present problem , and thesettlement could be subject totsunami. On the landward side ,rockfalls and landslides from thecliffs are likely to accompany largeearthquakes. Large blocks fallenfrom the cliff can be seen on theright.

Photo CN4213119: D.L. Homer

Figure 29 Aerial view of the PancakeRocks , Punakaiki , showing thewalkway which is mainly on the lastinterglacial (oxygen isotope stage 5)marine bench. Thin-b eddedOligocene limestone has beeneroded into spectacular landforms bya combination of coastal erosion andslow chemical solution along jointsand caverns beneath the marinegravel. The Devil 's Punchbowl in thecentre was probably formed by thecollapse of the roof of anunderground cavern.

Photo CN9833110: D.L. Homer

Figure 30 An almost continuous section through the gently dipping Late Miocene to Early Pliocene O'Keefe Formationis exposed in the coastal cliffs east of Cape Foulwind. The flat surface above the cliffs is a last interglacial (oxygenisotope stage 5) marine terrace, and about 5 metres of marine sand is exposed at the top of the cliffs.

Photo CN32853/2: D. L. Homer

Early to Middle Miocene sedimentary rocks

A major change in the pattern of sedimentation, related tothe initiation of oblique compression between the Pacificand Australian plates. took place in earl iest Miocene time.After almost complete submergence in the Late Oligocene,the Early Miocene was marked by the emergence of land.Upl ift and renewed tectonic acti vity is reflected in aregional change from carbonate-rich to terrigenous muddysediments, locally called 'papa' . Several local formationshave been idenfified and included in the Blue BottomGroup.

The change in tectonic reg ime led to local upl ift andchang in g depocentres. In so me areas the re is anunconformity beneath or within Early Miocene sediments(Nathan and others 1986).

Earl y to Middle Miocene sediments are preserved indifferent structural basins, now separated by uplifted rangesof pre-Tertiary rocks. Because of this isolation, severaldifferent nomenclatural schemes have been devised fordifferent areas, as summari sed by Nathan and others( 1986).

West of the Paparoa Range , around Punakaik i, theuppermost unit of the Nile Group (Potikohua Limestone)is overlain sharply by brown calcareous sandy mudstone(Welsh Formation, Mbw), with 1-2 metres of glauconiticmudstone immediately above the contact. The rapid changein lithology indicates a hiatus, but micropaleontologicalstudies do not indicate a recogni sable tjme break.

In the lnangahua valley, between the Papru'oa and Victoriaranges, the Nile Group passes gradationally upwards intolight brown calcareous mudstone, locally containinglimestone bands near the base. Thick interbeds of granite­derived sandstone in the upper part ind icate a nearby risingsource area, probably to the east. With the increase in sand,there is a progress ive shallowing in to estuarine and

fluviatil e facies, with locallensoid coal seams, mapped asRotokohu Coal Measures, Mbr (Johnston 1988).

Further south, a thick sequence of grey-brown calcareousmudstone (Inangahua Formation, Mbi) occurs in the axi sof the Grey valley trough, bUlthere is an unconformity tothe west and the basal part of the sequence is mi ssing.There is a grad ation al change into grey ca lcareou smudstone (Stillwater Mudstone, Mbs) near the base ofthe Middle Miocene .

In the Murchi son Basin, in the northeast corner of the maparea, calcareous mudstone of the Matiri Formation passesup wa rd s into a deep-water turbidite sequ e nce ofinterbedded quart z- mi ca sa nd stone and mud ston e(Mangles Formation, Mm). An influx of Caples-derivedvolcanogenic sediment led to rapid infilling of the basin ,and deposit ion of shallow marine sandstone. Overly ing isa flu vial sequence of muddy sandstone and conglomeratewith lensoid coal seams near the base (Longford Fomlation- not exposed 0 11 this map). Correlative sediments in theMaruia va lley, to the south, are mapped as the lower partof the Rappahannock Group (eMr). In a study of clastprovenance, Cutten (1979) showed that there is an upwardsincrease in metamorphic grade, and the clasts in the upperpart of the Rappahannock Group (mMr) consist largelyof Caples-derived schist.

29

Late Miocene to Pliocene sedimentary rocks

Parts of the present mountain ranges were emergent duringthe Late Miocene to Pliocene, although the topography isinferred to have been generally low- lying. Sediments weredeposited in basins approximating to the present daylowlands, and basin margin unconformities are common.

West of the Paparoa Range there is a shallow marinesequence, predominantly blue-grey muddy sandstone,which is mapped as O'Keefe Formation (Mbo) (Fig. 30).1n Haku-I offshore well , the O'Keefe Formation consistsof deeper water mudstone, and this is assumed to be typicalof the offshore success ion . There is a widespreadunconformity beneath the O'Keefe Formation (Fig. 3 1),and this is interpreted as evidence of a period of MiddleMiocene uplift (Nathan and others 1986; Kamp and others1996).

In the Grey valley and the lowland area to the south, thedominant lithologies are blue-grey muddy sandstone andyell ow-brown fin e-g rained san dstone (Eight MileFormation, Mbc). A small area offluvial sandstone withcoal seams and conglomerate beds on the western side ofthe Grey Valley (Nathan 1978a) is mapped as Mbf.

On the southeastern side of the Alpine Fault several smallin-faulted blocks of late Tert iary sedimentary rocks occurin the Esk River catchment. These blocks contain basal

muddy sandstone, carbonaceous sandstone and thin coalseams, overlain by Torlesse-deri ved conglomerate andinterbedded sandstone. The conglomerate correlates withthe upper p3l1 of a similar section in the Brechin Burn, 15km to the southwest (Newman & Bradshaw 1981) and isassigned to theLate Miocene to PlioceneMotunau Group (1Pn).

Late Pliocene to Early Pleistocene sedimentary rocks

Rapid uplift of the Southern Alps is refl ected by a flood offlu vial gravel and sand that extended n0l1hwest from theAlpine Fault, and is inferred to have originally coveredmost of the present anIand map area (Nathan and others19 86). Th e res ultin g conglomerate, containingpredominantly clasts of greywacke and schist, is mappedas Old Man Group (1'0) (Fig. 32a, b) Petrological studiesshow that it is entirely derived from Rakaia terrane rocks(MOItimer and others 200 I). Locally, glacial beds have beenrecorded within the Old Man Group (Gage 1945; Bowen1966), indicating the start of marked cooling (Fig. 32c).

In the Inangahua valley the Old Man Group rests on a thinun.it of flu vial sandstone and estuarine mudstone, mappedas IPbw.ln the Grey valley near Ahaura, the Torlesse-delivedconglomerates rest on older Pliocene conglomerates ofloeal (western) derivation (I'oc), and funher south the EightMile Formation grades upwards into the Old Man Group.

30

Figure 31 Steeply dipping unconformity between the O'Keefe Formation (Late Miocene to Early Pliocene) on the le«and Kalata Formation (Late Eocene) on the right , on the Denniston road near Waimangaroa. The figure is standingat the contact. Although the nature of the contact is not clear from the photograph , the basal part of the O'KeefeFormation contains pebbles of the underlying Kaiata Formation. The same contact has a low dip at Cape Foulwind(Fig. 26), but here the beds have been tilted up steeply, adjacent to the range front.

Photo CN31518119: D.L. Homer

Figure 32 Old Man Group Co; Late Pliocene to earl iestPleistocene) exposed In and near the opencast pit at Ross(see Fig. 43). These photographs were taken in late 2001,and the pit Is now partly filled.

Photos: S. Nathan

(a) Weathered conglomerate, composed almost enti relyof Rakaia terrane rocks. Most of the larger bouldersare greywacke , but many of the smaller clasts areschist.

(b) Selection of t.z. III-IV schist clasts picked out of theconglomerate.

(c) Steeply dipping till (left) overlying possible f1uvloglaclalgravels and lake silts.

QUATERNARY

There is a gap in the stratigraphic record of about 1.5 Mabetween deposition of the youngest pan of the Old ManGroup and the oldest late Quaternary deposi ts in theGreymouth map area. Tn many places this is representedby a major unconformity, representing a period of regionaluplift (wi th greatest uplift along the mountain ranges)lead ing to the erosion that began to shape the presentlandscape.

Much of the Grey and [nangahua valleys and the lowlandto the south has a co mplex cover of late Quaternarymoraine, river and alluvial fan gravel, coastal and lagoondeposits. and swamps. These surface and near-surfacedeposits together record a succession of ice advances andcontemporary periods of low sea levels, and interven inginterglacial high sea levels (Fig. 33). DetaiJed investigationshave revealed a glacial-interglacial sequence covering thelast 400 000 years, which is correlated with oxygen isotopestages 1- 10 (Table I). T he strati graphic and alt itud inalrelat ionships between g lacial outwash gravels andinterglacial marine deposits can be seen in the Hokitikaarea (Suggate & Waight 1998), and provide a unique linkin correlating glacial and interglacial sequences in NewZealand.

The deposits of th e last (Ot ira) g laciation are bestpreserved, and provide the key to interpretat ion of olderg lacial depos its. Likewise, the shoreline deposi ts andprocesses of the present interglacial (postglacial) providea model for o lder interglacia l deposits.

Glacial deposits

Glacial landforms , espec iall y morain e r idges andhummocky topography, can be recognised from aerialphotographs, in places even under forest cover. Tn mostexposures the glacial deposits consist of interbedded till(subrounded to subangu lar clasts up to boulder size in atight clayey matrix; Fig. 34) and fluvial outwash gravel.Clasts are predominantly greywacke from the Rakaia terrane,with lesser amounts of schist and minor graniloid clasts,indicating that derivation was mainly from the SouthernA lps.

Ti ll deposits of successive glaciations(Qlt, Q2t, Q4t, Q6t,Q8t, QlOt, eQt) cannot be distinguished from each otheron lithology, but are mapped as discrete units based ontheir elevation, dissection, and the relationship to nearbyoutwash gravels. The limits of different ice advances areshown in Fig . 33. More than one ice advance is ident ifiedin some glacia l periods, notably in oxygen isotope stage2, and these can be recognised by detai led studies in mostmajor catchme nts. Generally, older units are moreweathered than younger, but the degree of weathering isvariable between outcrops, and is not a reliable guide todistinguishing deposits ofdifferent age (Suggate & Waight1998).

31

32

Interglacial Glacial Ag. a-isotopeShoreline ice limits (Calendar yrs) stage

,....... 6000 1

--- ~::": - 195OO215000

.--- 66000 4

-----,'-- 123000 5-.----- 135000 6

-----,....... 220000 7

--- .--- 265000 8

---.--- 320000 9-- ,.----- 350000 10--I 580 000 1__'5_--,

GREYMOUTH

W~

Figure 33 Limits of late Quaternary ice advances and interglacial shorelines in the Greyrnouth area, derived fromgeological mapping and geomorphic interpretation. The coloured area shows the extent of ice during the last glacialmaximum (oxygen isotope stage 2), approximately 19 500 years ago - upper valleys and mountainous areas weresnowfields at this time. The dashed line shows the extent of ice 15 000 years ago, just before postglacial warming.

Oxygen Age Glaciation Map Interglacial MapIsotope (Calendar Symbol SymbolStage years BP)

1 Present day Aranui QIto 12 000 (postglacial)

2 12 000 Q23 to Otira4 74 000 Q4

5 74 000 to Kaihinu Q5130 000

6 130 000 to Waimea Q6190 000

7 190 000 to Karoro Q7248 000

8 248 000 to Waimaunga Q8300 000

9 300 000 to un-named Q9340 000

10 c. 360 000 Nemona Ql0

Older un-named eQ un-ll,amed eQ

Table 1 Sequence and chronology of late Quaternary units in the Greymouth area, after Suggate & Waight (1998).Chronology is based on Martinson and others (1987).

Figure 34 Bouldery till overlain by clayey till in morainedeposits dating from late in the last glaciation (oxygenisotope stage 2). Arnold valley. 2 km south of Kaimata.

Photo CN31384/24: D.L. Homer

Figure 35 Typical fluvial outwash gravel downstream fromlast glaciation (oxygen isotope stage 2) moraines. in theArnold valley, 3 km NNW of Kokiri. Coarser gravel in theupper part of the outcrop overlies finer gravel in the lowerpart.

Photo CN31384/25: D.L. Homer

33

Photo: $. Nathan

34

Alluvial deposits

Alluvial and f1u vioglacial gravels are widespread and wellpreserved in the flood plains and aggradation surfaces ofmaj or river vall eys and date from both glacial andinterglacial periods (Qla, Q2a, Q4a, Q5a, Q6a, Q7a,Q8a, Q9a, QIOa, eQa). Typically most outcrops consistof rounded boulders in a sandy matrix (Fig. 35). Clastli thologies in glacial outwash gravels are predominantlyRakaia greywacke, with minor schist. There is a clearcontrast between these and gravels derived from localsources west of the Alpine Fault, and this is sometimesuseful when considering the origin of particular graveldeposits.

There is a close relationship between term inal moraines,mark ing the dow nstream extent of glaciers, and thei rassoc iated outwash aggradation surfaces underlain byflu vial gravel. As a result of subsequent dissection, theremnants of many outwash surfaces are preserved asterraces. Although outwash surfaces may be clearl yrecognisable close to moraines. many become fragmentarydown-valley, especially when they have been eroded innarrow valleys. The key to matching different surfaces hasbeen the analysis of long profi les as they are traceddownstream (Suggate 1965; Suggate & Waight 1998).

Fluvial gravels have also been deposited by rivers duri ngin terg lac ial pe ri ods. Such gra ve ls have onl y beenrecognised close to the coast, where they are graded tointerglacial marine surfaces. Further inland. interglacialperiods are inferred to be times of net down-cutting, withlittle aggradation.

Alluvial fan deposits

Large alluvial fa ns, screes and collu vial deposits (Ql a,Q2a, Q6a, uQa) are prom inent at the foot of steep streamsdraining range fronts. The fa ns genera ll y consist ofmodcrately to poorly sortcd pcbble- to boulder-size clastsof local derivation. usually in a sandy matrix. Many smallerfans are included wi th mapped alluvial gravels.

Coastal marine deposits and dunes

Near the coast, the deposits of successive interglacialperiods (i ncluding the postglacial) consist mai nly of wellsorted beach sand and nearshore gravel and sand (Ql b,Q5b, Q7b, Q9b, eQb). Much ofthe sand is dark-colouredas a result of concentration of heavy minerals, includi ngilmcnite, garnet and epidote (Fig. 36). Weathering in oldersands has resulted in cementation by haematite. At eachinterglacial high-stand of sea level, the sea cut a cliff inolder rocks, and the beach deposits beneath the cliffs areoften highly enriched in heavy minerals, locally includ inggold . In some places the thin marine beds have beenoverlain by younger all uvial gravels.

Figure 36 Typical example of ilmenite-rich sand on thecoast, near the mouth of the Fox River. The dark patch inthe centre of the photograph shows subtle fractionation ofthe dominant minerals ca used by current action . The blackareas are dominantly ilmenite; pinkish~brown areas containconcentrations of garnet; dark greenish areas containconcentrations of epidote. Biotite is scatte red throughout.The lighter coloured sand is predominantly quartz andfeldspar.

A spectacular set of upli fted interglacial terraces is seenncar Westp0l1 (Fig. 37), where marine erosion during eachinterglacial has cut wide marine platforms across soft , lateTertia ry sediments (McPherson 1978; Suggate 1989).Similar terraces are seen elsewhere in the map area close tothe coast (Figs 38 & 39). [n most places there is a cover ofno more than 5- 10 metres of marine sand and gravel restingon older sediments. Close to the Paparoa Range, the oldestmarine cover beds and overlying fan gravels are mappedtogether as eQb.

A Ilarrow strip of dunes (Qld) is found on the postglacialcoastal plain close to the sea. Some dune sand has beenincluded in older units mapped as marine deposits.

Swamp and lake deposits

Swamp deposits (Q l a) consisting of poorly consolidatedsand, mud and peat are mapped in fl at, generally low-lyingareas close to the coast, commonly on the landward sideof sand dunes, and on hummocky morain ic topography.

Figure 37 A sequence of marine and fiuvial terraces on the western side of the Paparoa Range, south of Westport,labelled according to their map symbols. The highest terrace at the foot of the Paparoa Range is underlain by a marinebench, at least as old as 0 13, whose marine deposits are overlain by younger fan gravels (mapped as eOa). Belowthe high terrace on the left is the 09 terrace, with minor Q7 terraces. A similar, less extensive sequence is seen on theright of the photograph between the Totara and Little Totara rivers. In the centre much younger fluvial terraces wereformed as the Totara River cut down through the interglacial sequence. The Little Totara River in the foreground issurrounded by Holocene river fiats which have been grassed for farming.

Photo CN32462111 : O.L. Homer

Figure 38 Uplifted interglacial terraces at the southend of Rapahoe beach, near Greymouth. The lower(postglacial) terrace , about 9.5 metres above sealevel, contains a log radiocarbon dated at 4720 ± 70years BP (Suggate 1968). The higher terrace isapproximately 36-40 metres above sea level, andrepresents a widespread last interglacial (oxygenisotope stage 5) surface that is underlain by 3-5metres of marine and gravel. The clills in thebackground are Cobden Limestone (Oligocene).

Photo CN4330712: D.L. Homer

Figure 39 Uplifted postglacial terrace east of CapeFoulwind, near Westport. Shallow marine sand restsunconformably on Pliocene O'Keefe Formation, witha layer of boulders and scattered logs (probabiysimilar to the present beach) along the contact. A pieceof wood has been radiocarbon dated at 6330 ± 65years BP (Nathan 1976b) . This amount of uplift istypical of postglacial terraces found close to the coastthroughout the map area (compare Fig. 38).

Photo CN43419/16: O.L. Homer

35

Postglacial lake deposits of peat and unconsolidated greylacustrine mud (Qlk) accumu lated in hollows left bymelting ice at the end of the last glaciation .

Lacustrine mud, sand and gravel are found at an altitude

of up to 290 metres above sea level in the Murchison area(Suggate 1984; Roder & Suggate 1990), and indicate thepresence of a fomler large glacial lake. Their height relativeto nearby terraces suggests an age intermediate between

the flu viatile deposits of isotope stages 6 and 8, so thesebeds are mapped as Q7k.

Scree deposits

Large areas of scree (Qls) are present in areas of Rakaiaterrane in the higher parts of the Southern Alps. The screeslargely consist of slightly weathered, pebble to boulder­sized, angular clasts of indurated sandstone.

A lthough di screte areas of active downslope movement

can be easily distinguished, most screes are relati velystable, and rock weathering dating shows that the clasts

on the surface of screes were formed between the present

day and about 3000 years BP (McSaveney & Whitehouse1989). The buried parts of mapped screes are probably noolder than Holocene.

Landslide deposits

Landslides (Qll, uQI) are common features in Sleepercountry throughout the map area, although many are toosmall to be mapped separately. They vary in compositionfrom largely coherent but very shattered rock to unsortedfragments of rock in a silty clay matrix.

One of the largest areas of landsl iding, on the hillside eastof Westport , resultsmainly from bedding-plane slip withinBrunner Coal Measures (Inwood 1997).

Many landslides have been triggered by large earthquakes.Within the 20'" century, the 1929 Murchison, 1929 Arthur 'sPass, and the 1968 Inangahua earthquakes each causedsubstantial landsliding in parts of th e map area(Figs 6 & 9), and locally ponded small lakes.

Deposits of human origin

Areas of ground disturbed by sluicing and dredging forgold, especially around Kumara, have been mapped asQln. Some of the older dredge tailings have si mply beenpiled up, and show a characteristic hummocky landfonn(Fig. 40). Since the 1980s it has been mandatory torehabilitate mined land, and such land cannot now be easilyrecognised by its surface morphology.

Figure 40 Tailings and ponds left by past dredging operations for gold in early postglacial terrace gravels in the lowerreaches of the Arahura valley.

Photo CN31356113: DL Homer

TECTONIC HISTORY

Paleozoic to early Mesozoic margin of Gondwanaland

Rocks of the Buller terrane are characteristically quartzose,and were deposited adjacent to a continental landmassduring the Ordovician. In contrast, the Cambrian/Ordovician rocks of the Takaka terrane were formed in oradjacent to a volcanic arc. The different lithologies andtectonic settings imply that the two terranes were originallya considerable distance apart. Amalgamation of the twoterranes on the margin of Gondwanaland took place inEarly to Middle Devonian time, and was almostimmediately followed by emplacement of Late Devonianto Early Carboniferous granites.

There is almost no record of later Paleozoic to earlyMesozoic events apart from a small area of Triassic non­marine sediment which is intruded by sills of Jurassic low­Ti tholeiitic dolerite. This is geochemically similar towidespread flood dolerites of the same age in Antarctica,Tasmania and South Africa that were erupted prior to thebreak-up of Gondwanaland.

Mesozoic eastern terranes

The Torlesse composite terrane is interpreted as anextensive and complex submarine fan apron,predominantly deposited as a sequence of turbidites andmass-flow beds. The quartzo-feldspathic nature of thesandstone indicates continental derivation, and recentprovenance studies have suggested eastern Australia as alikely source.

The Rakaia terrane is a Triassic fan complex, and theyounger Pahau terrane (Jurassic to Early Cretaceous) hasbeen tectonically accreted against it. The suture zone isrepresented by the Esk Head belt, comprisingpredominantly melange but containing blocks from bothterranes.

At deeper crustal levels, rocks of the Rakaia terrane havebeen metamorphosed to schist, which has been exposedby late Cenozoic uplift in a narrow belt immediately eastof the Alpine Fault.

Early Cretaceous break-up of Gondwanaland

The break-up of Gondwanaland was marked by severalmajor events in the period 105-95 million years ago, in theEarly Cretaceous. Widespread emplacement of granitoidplutons was accompanied by uplift. Movement alongdetachment faults led to the juxtaposition of high-grademetamorphic and granitoid rocks against low-grademetasediments, forming metamorphic core complexes.Uplifted basement rocks provided source material for thenon-marine Pororari Group, now mainly preserved as faultedblocks around the margins of the Paparoa Range.

Late Cretaceous - early Cenozoic extension

At about 80 million years ago (Late Cretaceous) the NewZealand continental block started to separate fromAustralia, with the opening of the Tasman Sea. This wasmarked by a period of magmatism, with widespreademplacement oflamprophyre and associated dikes as wellas the localised A-type French Creek Granite.

Extension led to the formation of small inland basinsbetween 75-60 million years ago (latest Cretaceous to EarlyPaleocene), filled with non-marine (paparoa) coal measures.The end of spreading in the Tasman Sea about 60 millionyears ago corresponds to the slowing down of tectonicactivity. During the following 12-15 million years most ofthe region was emergent, and undergoing slow subaerialerosion approaching peneplanation, to form the widespreadWaipounamu erosion surface.

A period ofrenewed crustal extension which started about45 million years ago (Eocene) led to regional subsidence,as well as the development of local, fault-bounded basins.By the end of the Oligocene, almost the whole region wassubmerged, with widespread deposition of limestone.

Late Cenozoic oblique compression

Renewed uplift at the end of the Oligocene reflected thechange from oblique extension to oblique compressionacross the Australian/Pacific plate boundary. Many lateCenozoic basins were fault-bounded, but with a sense ofmovement reversed compared to the early Cenozoic. LateCenozoic sediments are predominantly terrigenous, derivedfrom uplifted areas on both sides of the Alpine Fault.

Dextral strike-slip movement started on the Alpine Fault,and continues to the present day. Progressive displacementon the Alpine Fault over a period of 20 million years hasresulted in the juxtaposition of contrasting rock types.

An increasing component ofcompression across the AlpineFault during the Pliocene, starting about 5 million yearsago, led to uplift along the eastern side, and the formationof a widespread alluvial gravel plain that covered most ofthe onshore area west of the Alpine Fault. Uplift wasgreatest immediately east of the Alpine Fault, leading tothe exposure and erosion of schist formed by deep burialand metamorphism of Rakaia terrane rocks.

Continuing compression led to uplift of the West Coastranges during the Quaternary, and resulted in the presentday range-and-basin topography between the Alpine Faultand the coast. Major climate changes during the Quaternaryresulted in periods of glaciation in the mountains (withdownstream aggradation) alternating with warmerinterglacial periods with higher sea levels close to the coast.The current level of tectonic activity, with continuingregional uplift of the land area and regular earthquakes, isprobably typical of what has occurred through theQuaternary.

37

38

J:,..,.~~ "'~}ii;~ ': ~, ' tf[' ~

-;'1;(fA·' """IT,"­~ .••. ,~, ;"",

.. " ~

Figure 41 Dredge working in the Grey valley near Ngahere. 1995. The tailings from the dredge are being piled up onthe upper side of the dredge pond and then smoothed out and covered with soil. The dark,coloured mounds are soilthat has not yet been spread across the surface. In the upper part of the photograph grass is growing on the restoredland, and in a few years it will be difficult to tell that the land has been mined (compare with Fig. 40).

Photo CN32385122: D.L. Homer

Figure 42 Technological advances have allowed some previously un-mined areas to be worked by small operationswith considerable conservation of water. This small working is in older outwash gravel (Q6a) in the upper Waimeavalley. Gravel is loaded into the hopper at the back of the screen, and water is reticulated from holding ponds.

Photo CN31623122: D.L. Homer

GEOLOGICAL RESOURCES

The Greymouth map area contains a range of mineralcommodities including almost all of New Zealand'sreserves of bituminous coal. It is also a major gold­producing region, has significant hydrocarbon potential,and is one of the few areas in New Zealand where pounamu(greenstone) is found. The geological resources of theGreymouth area have been described in detail byMcPherson and others (1994) and Eggers & Sewell (1990),and the following account is largely summarised from thosepublications, with some updating.

Gold

The South Island was the scene ofone of the world's largestgold rushes in the early l860s (Morrell 1968), and goldmining has continued to the present day, with much of thegold won within the Greymouth map area. Gold occurs inthree distinct ~eological settings: associated with quartzveins (also referred to as lodes or reefs), in alluvial orfluvioglacial placers, and concentrated with other heavyminerals in marine beach placers (locally termed blacksandleads).

Gold associated with quartz veins. Lensoid and sheet­like gold-bearing quartz veins occur within fold-relatedshear zones in the Greenland Group. The veins, containinggold and minor pyrite~ arsenopyrite and stibnite, areinferred to have been deposited from hydrothermal fluidsgenerated in the later stages of a regional metamorphicevent at about 420 Ma (Brathwaite & Pirajno 1993). Thehost rock is also mineralised adjacent to the quartz veins.

The main producing area is the Reefton Goldfield and itsnorthern extension, the Lyell Goldfield; at least 70 000 kgof gold has been extracted. Gold mines are restricted to anorth-trending belt about 10 km wide, in a zone of tightfolding (Gage 1948; Brathwaite & Pirajno 1993;Rattenbury & Stewart 2000). About halfof this productioncame from the Blackwater Mine and the Globe-Progressgroup of mines, both of which still contain substantialreserves. Although there is currently no hard-rock miningin the region; planning is under way by GRD Macraes Ltdto reopen the Globe-Progress workings as an opencast pit.

Quartz veins have been prospected and mined from otherareas of Greenland Group, including the southern PaparoaRange and the area around Ross, but the overall productionis less than 500 kg of gold.

A number of weakly auriferous quartz veins occur inTorlesse rocks east of the Alpine Fault, notably in theheadwaters of the Taipo and Wilberforce rivers (Bell &Fraser 1906; Becker and others 2000). Although there hasbeen considerable prospecting, there has been nosignificant production from any of these veins. Howeverthey are inferred to represent the source of much of thealluvial gold found west of the Alpine Fault (see below).

Fluvioglacial placers. Erosion of the Southern Alps overthe last two million years has produced a large amount ofsediment from the Rakaia terrane, which has been carried

westwards by glaciers and major rivers. Some of thissediment contains low-grade gold mineralisation derivedfrom quartz veins. Progressive reworking, particularly byfluvioglacial processes close to terminal moraines, has ledto the formation of areas of auriferous gravel whichcollectively constitute a giant placer field (Henley & Adams1979; Craw and others 1999).

An especially favourable situation for gold concentrationexists in the Taramakau and Hokitika valleys. A sequenceof ice advances terminated at about the same area, withmeltwater outflows of successively younger glaciationsconcentrating gold near the terminal moraines and proximaloutwash of earlier advances (Suggate & Waight 1998).

Alluvial placers have been worked by a variety of handand mechanical methods (Figs 41 & 42), ofwhich dredginghas been the most profitable. The major areas that havebeen worked are shown on the geological map. Since 1975there has been sustained production using small- to large­scale alluvial gold recovery plants. Total production ofalluvial gold in 1999 from the Greymouth map area was1244kg.

Locally rich placer deposits occur close to areas of goldmineralisation in the Greenland Group. The recently closedopencast pit at Ross (Fig. 43), working alluvial gravelsfrom the Mt Greenland block, yielded approximately 1400kg of gold over a 10-year period (C. Douch, CrownMinerals, pers. comm. 2002).

Marine placers. Detrital gold carried downstream to thecoast by rivers is continually washed along the coast andconcentrated in the surf zone by the prevailing northwardslongshore drift. The gold, together with ilmenite,titanomagnetite, gamet, zircon, and other heavy minerals,is concentrated in lenticular beach placers which are locallycalled blacksand leads. The gold is invariably very fine­grained and often difficult to recover.

Placers in the present day beaches were extensively minedin the early gold rush years by small-scale manual methodsknown as. blacksanding. A few beaches continue to beworked by these methods, which need little capital outlay.Small dredges worked some of the uplifted postglacialdeposits, especially around Barrytown.

Older raised interglacial deposits consist of sand andgravel, which weather rusty brown and become variablycemented with age due to oxidation ofmagnetite. This coatsthe gold particles, and results in the gold being even moredifficult to recover than in the younger deposits. Althoughindividual deposits may have locally high grades, theseare localised along the interglacial shorelines, where thegold was concentrated in blacksand leads (McPherson1978).

Gold deposits on the continental shelf, inferred to havebeen formed during lower sea-levels associated with lateQuaternary glaciations, have been the target of severaloffshore sampling programmes (Brathwaite & Pirajno

39

Figure 43 Deep opencast pit (centre) in Quaternary alluvial gravels, apparently derived from Donnelly Creek (left) onthe edge of Ross township. Deep leads or horizons of high gold values have been known for many years, and 19"century underground gold workings extended beneath Ross township. The photograph was taken in 1995. SUbsequentlythe pit was enlarged, and mining ceased in 2002.

Photo CN38488123: D.L. Homer

40

1993). Sea floor sediment sampling showed that Holocenemuddy sediments cover 1110St of the shelf apal1 from anarea 8- 14 km offshore from Hokitika, where an area ofsub­economic gold-bearing gravel was located.

Ilmenite (and associated minerals)

Most of the postglacial sand deposits. together with lateQuaternary interglacial raised beach deposits along thecoast, contain ilmenite, epidote, and garnet (Fig. 36) as

well as minor titanomagnetite, zircon, and traces of mona­

zite and gold.

The heavy mineral assemblage has been derived mainlyfrom schist immediately east of the Alpine Fault (Bradleyand others 1979,2002). The ilmenite grains contain tinysilicate inclusions, leading to relatively low titanium con­tent (45-47% TiO,). Chromium (0.2%) and vanadium(0.02%) contents in the ilmenite are low, and well withincommercial specifications. The zircon content of the sandvaries from 0.1 to 0.3%. Traces of monazite, gold, rutile,cassiterite, scheelite and beryl in some deposits may berecoverable as a by-product from large scale mining andrecovery of ilmenite.

The largest ilmen ite deposits are at Fairdown (east ofWestport), Carters Beach. Nine Mile Beach, Barrytown.

and south of Hokitika. These deposits indi vidually havereservesin the range of 1-7 million tonnes of ilmenite, at anaverage grade of 6- 13.8% ilmenite (Brathwaite & Pirajno1993), but to date have been regarded as sub-economic.

Other metallic minerals

Antimony in the fann of stibnite is a minor mineral insome gold-bearing quartz veins within the GreenlandGroup in the southern Paparoa Range and the ReeftonGoldfield. The only recorded production is fromLangdon's reef, a gold-stibnite vein. Ten tonnes wereshipped to England prior to 1882 (Morgan 1911) but laterattempts to open up this reef were unsuccessfu l.

McPherson and others ( 1994) described widespreadoccurrences of minor copper mineralisation in sma llquantities, associated with plutonic rocks, quartz veins andschist. There has been no production from the Greymouthmap area.

Several western tributariesof Cascade Creek in the LowerBu ller Gorge have been prospected since copper­molybdenum mi neral isationwas discovered in the 19505(Braithwaite 1959). An area of propy litic alteration, about150-200 m wide and 800-1000 mlong, occurs within aplutonof Bed insPorphyry (Early Cretaceous) and the surrounding

hornfelsed Greenland Group. Sulphide phases consist ofpyrite, molybdenite, and minor chalcopyrite. The Bald Hillprospect (Bates 1989), in mountainous country north ofLyell, occurs in Greenland Group intruded by small, high­level granitoid plutons. Molybdenite-quartz veins inhornfels form a weak stockwork zone, 2.5 km long by 700 mwide.

Silver is insignificant in both reef and alluvial deposits asthe gold contains less than 10% Ag. Regional prospectingof small granitoid plutons in the southern Paparoa Rangelocated float material with significant silver values (Price1984), although no source has been found.

Traces of cassiterite ("stream tin") are widespread in lateQuaternary alluvium and beach sand throughout the area.Although recognised in all dredge concentrates examined(Hutton 1950), it is generally no more than a mineralogicalcuriosity except in the Grey valley near Blackball (Morgan1911; Henderson 1917; Minehan 1989) where it appearsto be derived from the nearby Paparoa Range. Some ofthe highest values were found in concentrates from theNgahere dredge, where Nicholson (1955) estimated that40 tonnes/year of cassiterite were being discharged.

Greisen-hosted tungsten mineralisation occurs at DoctorHill-Falls Creek; Ba.rry'town, Kirwans Hill and BatemanCreek, and is associated with roof pendants of GreenlandGroup in plutons of S-type Karamea·granitoids (Pirajno& Bentley 1985; Brathwaite & Pirajno 1993). Theoccurrences are unusual as granite-related greisen zoneselsewhere commonly develop wolframite rather thanscheelite (Tulloch & Mackenzie 1986).

Traces of the rare earth minerals monazite, thorite,uranothorite and xenotime are found in the ilmenite-richheavy mineral fraction of sand in present day coastalbeaches. Rare earth minerals have also been recognised inthe concentrates from gold workings in the Westport,Reefton and Grey River areas (Hutton 1950; Minehan1989). They could be a useful by-product of large-scaleworkings for gold or ilmenite.

The Pororari Group hosts low grade, sedimentary uraniummineralisation in the Lower Buller Gorge, in the PororariRiver area, and near the mouth of Fox River (Beck andothers 1958; Williams 1974). Since its discovery in 1955a number of companies have tested the mineralisation byadits and drilling. The mineralised beds are thin andlenticular, resulting in erratic grades, almost everywhereless than 0.1 % Ups' Despite considerable prospecting inthe late 1960s and 1970s, no new areas of uraniummineralisation or higher grades have been found. Nosignificant uranium mineralisation has been found in thegranitoid rocks of this area, nor concentrations ofU-bearingminerals in the alluvium or beach sand derived from them(Nicholson 1955).

Clay

Kaolin clay deposits, of varying quality, are widespreadon the western side of the Alpine Fault. Clay formed by

deep weathering of gneiss or granitoid rocks, locallypreserved beneath Brunner Coal Measures, contains mainlykaolinite with minor quartz and mica, and has been minedin several places. In the 1970s and 1980s clay was quarriedfrom near Charleston for the production of white sanitaryware in Westport.

Similar clay is found as beds within the Brunner CoalMeasures. The floor clay of the main Brunner seam nearBrunner was mined in conjunction with the coal seam inseveral mines, and used for making fire bricks (Morgan1911; Gage 1952).

Some of the marine mudstone units within the Tertiarysuccession have been locally used for the manufacture ofbricks. In particular, the Stillwater Mudstone (Blue BottomGroup, Miocene) was quarried for use in the KaroroBrickworks near Greymouth until the 1960s.

Rock

Abundant supplies of aggregate are present throughoutthe Greymouth map area, almost entirely as gravel frompresent day rivers, late Quaternary terraces, and locallyfrom dredge tailings. Material is usually quarried close towhere it is needed rather than being transported over largedistances. The gravel commonly used consistspredominantly of granite and Rakaia terrane- or GreenlandGroup-derived greywacke, with varying amounts of schistand gneiss depending on local sources. From the GreyRiver southwards the dominant lithology in river gravelsis Rakaia terrane greywacke.

In 1999 about 162000 tonnes of aggregate were producedfor roading within the Greymouth map area, as well as9000 tonnes for use as building aggregate.

There is a continuing need for large blocks of rock (rip­rap) for use in stopbanks to prevent riverbank erosionduring frequent, high-volume flooding in West Coast rivers.Transport is expensive, so the West Coast Regional Counciltries to maintain a network of quarries that can be usedwhen needed, often at short notice. Although there is noshortage of hard rock, much ofit is too fractured to providelarge blocks that do not break up on weathering. Oligocenelimestone is quarried for rip-rap in a number of places(often using quarries opened for agricultural lime). TheCobden Limestone near Greymouth has been quarried formany years, and provided the material for building andextending Greymouth Harbour. One of the few quarries ingranitoid rocks was developed at Cape Foulwind, wherelarge blocks were used to develop the Westport Harbourmoles.

Several rock types from the QMAP Greymouth area arepotentially suitable for use as building and facing stone(dimension stone), particularly granite, schist, limestoneand serpentine. A significant limiting factor in finding newresources is the almost ubiquitous presence of irregularjointing, caused by Cenozoic tectonism. At present it isgenerally more economic to import stone for buildingpurposes than to use local material. 41

Figure 44 A large lens of earliest Oligocene algal limestone is quarried near Cape Foulwind (centre right) as thefeedstock for cement manufacture. The limestone is trucked for processing to the Milburn Cement works (centre left).Most of the cement is transported by ship from the port of Westport (above cement works), or is railed to other partsof the South Island.

Photo CN3236814: D.L. Homer

42

Marshall (1929) li sted several local rock types that havebeen tested and used as facing stone in New Zealand,including the Fou lwind Granite, which contains spectacularlarge K-feldspar megacrysts. Serpentine from the GriffinRange has been used as facing stone and a small amount isstill being quarried.

Greenstone (nephrite, pounamu) and goodletite

New Zea land greenstone (nephrite, loca l ly cal ledpounamu) is the common name for an amphibole groupminera l within the tremolite-actinol ite series. It hastraditionally been used by Maori for jewellery, tools andweapons and has strong cultural significance. Modern useis mainly for jewellery and ornaments. Ownership ofpounamu has now been vested in the local Maori , NgaiTahu.

Nephrite occurs as thin lenses within the PounamuUltramafics (Bell & Fraser 1906; Johnston 1983). Almostall of the material recovered in recent years hascome fromfloat material in Olderog Creek, a tributary of the ArahuraRi ver, where nephrite occurs as boulders, exceptionallyup to 25 tonnes in weight. Most of the larger bou lders havenow been removed and liule float material remains.

Goodletite is the local name for a rare and distinctivegree ni sh~grey ruby rock which is highly prized as anornamemal rock. It is found only as boulders in rivers andfiuvio-glacial gravels between the Taramakau River andRoss, and consists of corundum (varying between rubyand sapphire), tounnaline and greenchrome-rich mica. TIlepresence of rare serpentine rinds indicates that the bou lderswere derived from the Pounamu Ultramafics. They mayhave formed aspan of a reaction sequence between sch istand adjacent ultramafic rock (Grapes & Palmer 1996).

Lim~tone

Abundant resources of limestone and marble suitable foragricultural and industrial use are available in theGreymouth map area. In particular, the widespreadoccurrence of high-grade Oligocene limestone (platfonnfacies of the ile Group, mainly algal and bryozoanlimestones), with CaCO) consistently greater than 90%,means that quarries can be opened in many parts of thearea west of the A lpine Fault, and thustmnsport costs canbe minimi sed. Ordovic ian marble from the Mt ArthurGroup is also quarried near SpringsJunction.

At Cape Foulwind, near Westpon, a large lens of high­grade algal limestone provides the feedstock for theMilburn Cement works, together with a smaller amount ofKaiata Formation (Fig. 44). Most of the cement israiled orshipped outside the West Coast region.

Weathering and solution of limestone has also developedseveral karst featuresused for recreational purposes. Cavesand underground streams are present in most areas oflimestone, with spectacular caves near the Nile Ri ver, FoxRiver and Bullock Creek. Pancake Rocks and th ei rassociated blowholes are a famous tourist auraction nearPunakaik i (Coates 1988).

Other non-metallic minerals

Fluorite mineralisation has been recorded from severallocalities in the Lower BulierGorge, especially from KehuStream, where green fluorite veins cut the Berl insPorphyry(Nathan I978b), and near Sinclair 's Castle (Beck and others1958). Despite intensive prospecting in the 1970s, noeconomic deposits have been found.

Mica occurs in pegmatites, which are common in granitoidrocks throughout the map area. A small amount of micawas mined in 1911-12 from a pegmatite near Constant Bay,but the grade is low (Morgan & Bartrum 1915). Some sheetmica also occurs in a nearby pegmatite at Deep Creek.The demand for sheet mica is low, and these deposits arenot likely to be worked.

Silica Sand comprising quartz-rich sand and sandstoneoccurs in the Buller, Charleston and Greymouth coalfieldsand at Cape Foulwind and Ross as well as in bands ofquartzite in Devonian rocks near Reefton. Young (1964)summarised the silica resources of the region, concludingthat in most places the silica content did not exceed 80%,andthat much of the material appears to be too micaceousand carbonaceous for ferrosilicon manufacture.

Eocene quartz .sand near Charleston (Little Totara Sand;Nathan 1975) is one of the most easily worked resourcesof silica sand in the area, and is generally rather highergrade (average around 85% Si0

2, locally up to 95%) than

other localities mentioned above. In recent years it hasbeen quarried for use in cement manufacture, and a smallamount has been used in glass manufacture.

Coal

The Greymouth map area contains virtually all the reservesof bituminous coal in New Zealand, as well as substantialreserves of sub~bituminouscoal. Coal mining started inthe 1860s in the Greymouth and Buller coalfields, and hascontinued since then. Initially the bituminous coal was usedfor steam-raising (rail, shipping and industrial boilers) andtown gas supply, with associated coke production. Sincethe 1950s these uses have declined, and in recent yearsmost bituminous coal has been exported for specialist usein the steel-making and chemicalindustries.

The higher rank Cretaceous and Tertiary bituminous coalshave low-medium ash, satisfactory fluidity characteristics,high swelling, and a high proportion ofreactive macerals.Lower rank bituminous and sub-bituminous coals aremarketed for domestic and industrial use, but are in lowerdemand because of lower specific energy (calorific value)and commonly higher sulphur content.

All mining was underground until large-scale opencastmining started in the Buller Coalfield in the 1940s,·providing a much more economic way ofmining shallowcoal, with potential to recover virtually all the coal in thickseams. Several areas previously worked by undergroundmethods have been re-opened as opencast mines (Fig.45). There is further potential for opencast mining in theBuller, Reefton, Garvey Creek and Charleston coalfields.Coal seams are deeper in the Greymouth and Pike Rivercoalfields, and are likely to be mined only by undergroundmethods.

Three groups of coal measures contain mineable coal:Paparoa Coal Measures (Late Cretaceous-Paleocene), inthe Greymouth and Pike River coalfields, were depositedin the narrow north-south trending Paparoa Trough(Nathan and others 1986). In the Greymouth Coalfield,mapped in detail by Gage (1952), seven local units ofalternating fluviatile sediment (sandstone, conglomerateand coal seams) and lacustrine mudstone have beenrecognised. Coal seams are lensoid, and locally up to 9metres thick. All Paparoa coals have low sulphur content,and generally low ash.

Brunner Coal Measures (Middle to Late Eocene) weredeposited following a Paleocene to Early Eocene periodof quiescence. Regional subsidence led to progressiveinundation of theregion, with coal measures at the base ofthe Tertiary sequence. Fault-controlled subsidence led toincreased thickness in local basins, especially the BullerCoalfield. Apart from local conglomerates, Brunner CoalMeasures are dominated by quartzose sandstone. Coalseams are sporadic in distribution (Flores & Sykes 1996;Titheridge 1993) and usually lensoid, but locally containseams up to 10 metres thick.

Rotokohu Coal Measures and Longford Formation(Early Miocene) are fluviatile beds (mainly sandstone,conglomerate, and carbonaceous shale), representing anEarly Miocene regression in the Inangahua valley andMurchison Basin. Both units contain a few lensoid coalseams near the base. Although they have been minedlocally, the seams represent only a minor part of the totalcoal resource.

The Coal Resources Survey undertook a complete re­evaluation of coal resources throughout New Zealand inthe late 1970s and early 1980s, including drilling in somepoorly known areas (Taylor 1999). A summary of coalresources for each coalfield is presented by Barry andothers (1994), from which the recoverable reserves for thecoalfields in the Greymouth QMAP area have beenextracted (Table 2).

Although the total reserves ofrecoverable coal seem large,not all this coal may be able to be mined for technical orenvironmental reasons. Almost all the reserves of opencastbituminous coal occur within the Buller Coalfield, andsome areas of indicated and inferred coal reserves aresituated in ecological reserves. Much of the large indicated!inferred reserves in the Greymouth Coalfield can be minedonly by underground technology, and past experienceindicates that this is likely to be difficult because ofstructural complexities and the gassy nature of the coal.

43

Photo CN313314: D.L. Homer

44

Underground OpencastMeasured Indicated Inferred Measured Indicated In ferred

BITUMINOUS COAL

(+ semi-anthracite)Buller 1.87 3.54 9.4 24.93 48.6 26.0Garvey Creek om 0.37 1.8 358 0.72 0Pike River 0 21.83 65 0 0 0Greymouth 0.47 124.97 37.4 0.7 0 0Murchison 0 0 0.5 0 0 0.2Fox River 0 0 0.3 0 0 0Total 2.37 150.71 55.9 29.21 49.32 26.2

SUB-BITUMINOUS COAL

Inangahua 0 0 1.0 0. 18 2.64 2.2Reefton 0.75 05 3.1 0.17 0.5 0Charleston om om 0.1 0 12.8 0Punakaiki 0 0 1.7 0 0 0Total 0.78 0.51 5.9 0.35 15.94 2.2

Table 2 Reserves of recoverable coal (in million tonnes) from the Greymouth map area. Data has been extracted IromBarry and others (1994).

Figure 45 Opencast mining in the Stockton No 2 Opencast, Buller Coalfield. A thick coal seam is found below hardsandstone which has been stripped off prior to mining. Much of this area was previously mined by underground methods,which left behind most of the thick coal seam. The Mt Frederick Fault forms a natural western limit to mining on the leftside of the view, and hills of granitoid rock (left) have been thrust over coal measures. The fault is exposed in the cliff atcentre left, and forms the boundary between granite (white) and mudstone (brown).

Figure 46 Some of the largest oil seeps in New Zealandoccur at Kotuku, in the Arnold valley. Pits have been dugto extract the oil, which now forms a thin skin on top ofsaline water.

Photo CN3137615: D.L Homer

Oil and gas

Prospecting for oil and gas has been encouraged by seepsand shows, including oil seeps at Kotuku (Fig. 46), as wellas widespread traces ofoil and gas in prospecting drillholesand within mines in the Greymouth Coalfield (Wellman197 I ; Gage & Wellman 1944; Young 1967; Suggate &Waight 1998).

Shallow wells were dri lled in the Kotuku area in the e,u·ly1900s, with recorded production of only a few hundredbarrels. Modern exp loration in the region beganimmediately before and during World War 2, with seismicsurveys(Modriniak & Marsden 1938) and detailed surfacegeological mapping leading to the drilling of four deepholes. Considerable seismic exploration was carried outfrom the 1960s onwards, followed by the drilling of oneoffshore well and eleven deep onshore wells. several withoil and gas shows. The most significant have been a gasblowout in SFL- I (west of Kumara), and subcommercialquantities of high-gravity oil recovered from Niagara-I.drilled west of Moana.

Geochemical and maturation properties of Paparoa andBrunner Coal Measuressuggest that they are good sourcerocks for hydrocarbon generation (Nathan and otherst986). Sandstones of the Paparoa Coal Measures, BrunnerCoal Measures and Island Sandstone (and correlativeEocene sandstones) have good reservoir potential, andoverlying mudstonesform an effective cap.

The late Cenozoic formation of the Brunner Anticline andrelated structures post-dated maximum burial of the coalmeasures, and therefore some hydrocarbons may havemigrated out of the Paparoa Trough prior to formation ofstructural traps. Discovery of hydrocarbons depends onlocating structural or strat igraphic traps that haveeffectively held hydrocarbons since the Late Oligocene,or secondary traps where oil and gas have subsequentlymigrated. The Grey Valley Trough is probably the mostprospective area because there ispotential for hydrocarbongeneration in the late Cenozoic (Thrasher and others 1996;Suggate & Waight 1998). The Kotuku oi l seeps indicatethat oil has been generated and has migrated up-dip (Nathanand others 1986).

Water

Most of the water used in the urban areas and on farms isobtained from streams, and stored in local reservoirs.Because of the high rainfall, tank water from roofs is usedin many rural houses, and little use is made of groundwater.lfneeded. largeamounts ofhigh quality groundwatercouldbe obtained from late Quaternary alluvial gravels.

Warm springs

A number of isolated warm springsoccur in the SouthernAlps (Fig. 47), and have been listed by Mongillo & Cleland(1984). They are used locally for bathing. It is assumedthat the springs discharge meteoric water that has beenheated beneath the mountains, and transported to thesurface along faults and fractures. The spring waters aregenerally of Na-bicarbonate composition, with varyingamounts of minerali sation (Cave and others 1993).Hydrogen su lphide gas is often discharged, and the smellof H

2S is a distinctive feature of warm springs in the

mountain valleys.

Figure 47 Harold Wellman (left) and George Grindleyrelax in a warm spring close to the Alpine Fault in theHaupiri valley. Wellman discovered the Alpine Fault andundertook a large amount of mapping throughout the areacovered by the Greymouth map in the 1940s and 1950s.

45

GEOLOGICAL HAZARDS

Seismotectonic (earthquake) hazard

Over the last 150 years, the Greymouth map area hasexperienced moderate to high leve ls of se ismi c(earthquake) activity, and this is likely to continue.

Earthquakesare measured in lel111Sorlheir released energyaccording to the magnitude (M) scale. The effects (or fe ltintensities) are assessed according to the Modified MercalliIntensity (MM) scale (Table 3). The follow ing large,shallow earthquakes have al l had epicentres within the maparea:191 3 Westport (M6.0)1929 Arthur's Pass (M7. 1)1929 Murchison (M7.8)1962 WestpOJ1 (M5.9)1968 Inangahua (M7. 1)199 1 Hawks Crag (M6.3)1995 Arthur 's Pass (M6.3)

A re-evaluation of seismic hazard in ew Zealand byStirling and others ( 1998) used models based on the likelyground acceleration at any place based on both historicearthquakes and the late Quaternary geological record. Thehighest levels of Peak Ground Acceleration (PGA),corresponding to the most severe shaking and damage,

occur along the Alpine Fault and havea 9- 19% probabilityof occurrence in 20 years (Rhoades & Van Dissen 2000).The Greymouth QMAP area might expect an MM6 eventwith an average return period of 6 years, an MM7 eventevery 15 years, an MM8 event every 2 1years, and an MM9event every 32 years (w. Smith, pers. comm. 200 I).

The consequences of a large. shallow earthquake in oradjacent to the Greymouth map area are strong groundshaking, multiple aftershocks, shaking-induced slopeinstability, and possible surface fault rupture. Known faultrupture within the last 500 years has occurred on the AlpineFault as well as on parts of the White Creek and lnangahuafaults.

Unconsolidated, fine-grained sediments such as swampdeposits, estuarine mud, marine sand and gravel, andlandfill have low strength, and are likely to show significantamplification of ground shaking during an e3lthquake. Thetowns of Westport, Greymouth, Hokitika and Reefton arebuilt on Quaternary deposits, and it is likely that parts ofthese urban areas may show some shaking amplification,as they did in the 1968 Inangahua earthquake (Suggate &Wood 1979). Landslides and rockfalls are likely in urbanareas close to steep hills, for example around Punakaiki(Fig. 28).

46

MM 2: Felt by persons at rest, on upper floors or favourably placed.

MM 3: Felt indoors; hanging objects may SWing, vibration similar to passing of light trucks.

MM 4: Generally noliced indoors but not outside. Light sleepers may be awakened. Vibration may be likened topassing of heavy traffic. Doors and windows rattle. Walls and frames of buildings may be heard to creak.

MM 5: Generally felt outside, and by almost everyone indoors. Most sleepers awakened. A few people alarmed.Some glassware and crockery may be broken. Open doors may swing.

MM 6: Felt by all. People and animals alarmed. Many run outside. Objects fall from shelves. Glassware and crockerybroken. Unstable furniture overturned. Slight damage to some types of buildings. A few cases of chimney damage.Loose material may be dislodged from sloping ground.

MM 7: General alarm. Furniture moves on smooth floors. Un-reinforced stone and brick walls crack. Some pre­earthquake code buildings damaged. Roof tiles may be dislodged. Many domestic chimneys broken. Small slidessuch as falls of sand and gravel banks. Some fine cracks appear in sloping ground. A few instances of liquefaction.

MM 8: Alarm may approach panic. Steering of cars greatly affected. Some serious damage to pre-earthquake codemasonry bUildings. Most un-reinforced domestic chimneys damaged, many brought down. Monuments and elevatedtanks twisted or brought down. Some post-1980 brick veneer dwellings damaged. Houses not secured to foundalionsmay move. Cracks appear on steep slopes and in wet ground. Slides in roadside cuttings and unsupportedexcavations. Small earthquake fountains and other instances of liquefaction.

MM 9: Very poor quality un-reinforced masonry destroyed. Pre-earthquake code masonry buildings heavily damaged,some collapsing. Damage or distortion to some post-1980 buildings and bridges. Houses not secured to foundationsshifted off. Brick veneers fall and expose framing. Conspicuous cracking of flat and sloping ground. Generallandslidingon steep slopes. Liquefaction effects intensified, with large earthquake fountains and sand craters.

MM 10: Most un-reinforced masonry structure destroyed. Many pre-earthquake code buildings destroyed. Manypre-1980 buildings and bridges seriously damaged. Many post-1980 buildings and bridges moderately damaged orpermanently distorted. Widespread cracking of flat and sloping ground. Widespread and severe landsliding onsloping ground. Widespread and severe liquefaction effects.

Table 3 Pan of the Modified Mercalli Intensity scale (MM), summarised from Downes ( 1995).

Landsliding

Shaking during the 1929 (Arthur's Pass and Murchi son)and 1968 (lnangahua) earthquakes caused a large numberof landslides, and it is likely thal most older landslideswithin the Greymouth map area are also earthquake­initiated (Fig. 48). Hancox and others (2002) havecompiled maps showing the distribution of large landslidescaused by these earthquakes.

The effects ofearthquake-induced landsliding may last formany years after an earthquake, wi th a marked increase inriver aggradation, and increased risk of flooding.

The hillside east of Westport is mapped as a large complexlandslide, essentially caused by downslope movementalong weak units in the Brunner Coal Measures which heredip 10- 15° west. Inwood ( 1997) has identified severalphases of movement, and shownthat the landslide complexhas been reactivated several times over the last 200 000years. Most parts of the lands lide complex appear to becurrently stable. However, Lake Rochfort, dammed with inthe landslide complex at an alti tude of 480 metres abovesea level (Fig. 49), is of concern because of the possibi lityof a catastrophic dam break after anearthquake or torrentialrain.

Tsunami

Coastal flooding and damage caused by tsunami (seismicsea waves) is possible along the entire coastline of theGreymouth map area as well as the lower reachesof rivers.The coastal towns of Westport, Greymouth and Hoki tikaare all at risk. Even small tsunami can cause erosion andproblems for sl11all boats because of the strong currentsgenerated. Large tsunami of more than 4 111 are life­threatening, and can be very damaging to structures.

In historical times the coastline hasbeen little affected bytsunami generated by distant events, outside New Zealand'scontinental shelf. Locally-generated tsunami, potentiallycaused by near-shore fa ult rupture or submarinelandsliding, pose a greater threat.

A rise of ri ver water level of about a metre occurred atWestport and Ngakawau at the time of the magnitude 6.0earthquake of 22 February 19 13, located offshore fromWestport (G. L. Downes, pers. comm. 200 I).

Figure 48 Landslide in the Maruia valley, one of many that formed during the 1929 Murchison earthquake. The landslidediverted the course of the river, and caused it to cut down in a new course, thus uncovering the Maruia Falls (left centre)(Suggate 1988).

Photo CN4645 t/35: D.L. Homer

47

48

Figure 49 The hillside beneath Mt Rochfort, northeast of Westport, is a complex series of landslides formed onBrunner Coal Measures, which in the main photograph dip gently towards the observer. In the bottom of the photographalluvial fans, formed during major flood events, spread outwards from the hills. Lake Rochfort (smaller photograph)fills a depression within the landslide complex, with the outlet artificially raised for hydroelectric generation, andcontains approximately 320 000 cubic metres of water. The lake poses a long-term hazard to the area below in theevent of sudden dam-burst.

Photos CN3//12//4 &CN311/S/21: D.L. Homer

ENGINEERING GEOLOGY

This section prov ides ge nera li sed backgro und forgeotechnical investigations and hazard assessments, butis not a substitute for a detailed site investigation. Potentialdifficu lties with some rock units are highlighted.

Paleozoic-Mesozoic rocks west of the Alpine Fault

Granitoid, metamorphic and sedimentary rocks that mainlycrop out in the mountain ranges west of the Alpine Faultare s trong . hard , and nea rl y a lways unweathered.Excavation usually requires blasting, and steep facesgene rall y remai n stabl e. Th e rocks are generall ypervasively jointed, often with a joint spacing ofO.S m orless, which makes it difficult to quarry large, unfracturedblocks.

Adjacent to major, brittle fault zones, which may be tensof metres wide, the rocks are intensely fractured, and locallyare very weak due to the presence of crush zones and veryclosely spaced joints.

Paleozoic-Mesozoic rocks east of the Alpine Fault

Greywacke sandstones of the Rakaia terrane are strong,hard, and variably jointed. Interbedded argi llites are notas strong, and often highly fractured. Slopes cut in freshrock are usually stable, although rocks in very steep faceslocal ly co ll apse, especiall y in areas that have beenglaciated.

Rock strength decreases with increasing metamorphicgrade (e.g. in the 5- 15 Ian belt immediately east of theAlpi ne Fault) as foljation develops into a significant planarweakness.

The Arthur 's Pass highway (SH73), ooe of the main alpi neroutes across the South Island, is entirely through Rakaiaterrane rocks..Keeping the highway open throughout theyear poses distinct engineering challenges (Figs 50-52).

Rocks of the Esk Head belt , in the southeast corner of themap area, are distinct ly weaker than the Rakaia terranerocks to the west. The belt is characterised by lower, morerounded topography. There is considerable close-spacedjointing and widespread shearing.

Tertiary sedimentary rocks

There is enormous variat ion in the geotechnical propertiesof Tertiary rock units, both because of the range of rocktypes, and also because of the variation in induration(caused by depth of buri al). Bruoner Coal Measures(Eocene) provides an extreme example. Near Cape Foulwiod,the unit has never been buried by more than a few hundredmetres, and is an unconsol idated quartz sand. In contrast,in the Bu ller Coalfield, where it is inferred that there hasbeen up to 6 km of burial (Kamp and others 1996), the sameunit is a massive, strong rock that needs to be blasted inmining operations (Figs 24 & 45).

Oligocene limestones are usuall y highly cemented andhard, and can be quarried in large blocks. Most mudstones,especial ly those of Miocene and Pliocene age, are re lativelysoft, and may be prone to erosion and landsliding.

Quaternary sediments

Quaternary gravel and sand deposits in moraines, alluvialterraces and fans are poorly consolidated (classified asengineering soils) . However the individual clasts in theyoungest (Holocene and last glaciation) gravels are usuallyunweathered, and have local ly been quarried as aggregate.

The properties of some glacial deposits are highly variable,and may be unpredictable on a local (e.g. 10 m) scale,especially in localities where lake silts are interbedded withgravel. Till is often of low permeability, and may causedrainage problems.

Figure 50 Protection of theArthur's Pass highway isnecessary in sections subject tos li ps and localised flooding asshown by this section of the roadnear Candy's Bend.

Photo CN43256/21: D.L. Homer

Figure 51 Active landslides and screes combined with very heavy rainfall present a hazard for road construction andmaintenance in the Southern Alps. Several different approaches are needed to keep State Highway 73 across Arthur 'sPass open throughout the year. A winding section of the road previously skirted around the top of the unstable part ofthe landslide in the centre of the photograph. In 2001 this was replaced by a viaduct close to the Otira River beneaththe zig-zag.

Photo CN35817/25: D.L. Homer

Figure 52 The new viaduct which largely avoids the zig-zag route across the landslide (left).

Photo CN43352123: D.L. Homer

AVAILABILITY OF QMAP DATA

The geological map accompanying this book is derivedfrom information stored in the QMAP geographicinformation system (GIS) database, maintained by theInstitute of Geological & Nuclear Sciences, and from otherGIS-compatible digital databases. The data shown on themap are a subset of the available information. Customisedsingle-factor and multifactor maps can be generated fromthe GIS and integrated with other data sets to produce, forexample, maps showing fossil or mineral localities inrelation to specific rock types, or maps showing rock typesin relation to the road network. Data can be presented foruser-defined specific areas, for irregular areas such as localauthority territories, or in the form of strip maps showinginformation within a specified distance of linear featuressuch as roads or the coastline. The information can be madeavailable at any required scale bearing in mind the scale

. ofdata capture and the generalisation involved in digitising.Maps produced at greater than 1:50 000 scale will not showaccurate, detailed geological information unless they arebasedon point data (e.g. structural information). Ifrequiredthe QMAP series maps can also be made available in digitalform using standard data interchange formats.

The digital data have been captured from data record mapscompiled on standard 1:50 000 NZMS 260 topographicmaps. These record maps are filed in GNS offices inDunedin and Lower Hutt (Gracefield) and, althoughunpublished, are available fOfconsultation. They are storedon transparent film and copies can be made. The legendand mapping philosophy used for the detailed maps arebased on lithostratigraphy and may differ from those usedonQMAP.

For new or additional information, for prints of this mapat other scales, for selected data or combinations of datasets or for derivative or single-factor maps based on QMAPdata, please contact:

QMAPLeaderInstitute of Geological & Nuclear Sciences Ltd.P.O.Box30368LowerHutt

ACKNOWLEDGMENTS

This map was compiled by S. Nathan (part or all ofNZMS260 sheets 133, 131, 132, 133, K29, K30, K31, K32, L29,DO, L31), M.S. Rattenbury (133, K33, DO, Ul, L32,L33), and RP. Suggate (Quaternary geology of mostsheets). Major sources of contributing information weregeological maps at 1:50000, 1:63360, or other scales byCave (1986), Laird (1988), Nathan (1975,1976b, 1978a& b, 1996), Roder & Suggate (1990), Tulloch (1995),Suggate (1957), Suggate & Waight (1998), Waight (1995),and White (1988) as well as published papers, reports,bulletins, and unpublished material from the files of theInstitute of Geological & Nuclear Sciences, mineralexploration company reports and university theses.

New fieldwork during 1998-2001 concentrated on visitingselected key areas and filling gaps in knowledge, especiallythe granitoid rocks of the Victoria Range (Sheets L29, L30,L31; undertaken with considerable assistance from RJongens), and the area southeast of the Alpine Fault (sheetsU2, K32 and U3). K.R Berryman, S. Cox, MJ. Isaac,and I.M. Turnbull also assisted with the mapping.

Aerial photograph interpretation of landslides by N. Perrinand T. Coote was compiled from the Landslide Map ofNew Zealand project. The offshore geology has beencompiled from Nathan and others (1986). We thank theNational Institute ofWater and Atmospheric Research forpermission to reproduce offshore bathymetry from theirdigital records.

The use of information from unpublished university theses,notably Angus (1984), Blackmore (1988), Botsford (1983),Brown (1998), Cutten (1976), Dixon (2001), Inwood(1997), Jury (1981), Koons (1978), McLean (1986), Parish(1998), Petrie (1974), Waight (1995) and White (1988) isappreciated. The co-operation ofgeology department headsfrom Auckland, Victoria, Canterbury and Otagouniversities in allowing access to theses is gratefullyacknowledged.

Development and maintenance of the GIS database wasby D.W. Heron and M.S. Rattenbury. Digital capture andmap production was by J. Arnst, C. Atkins, D.W. Heron,S. Nathan, M.S. Rattenbury and D. Townsend. Thediagrams were prepared by P. Carthew, C. Hume and M.S.Rattenbury.

Parts or all of the map and text were reviewed byM.G. Laird, J. Campbell and D. Shelley (University ofCanterbury), G. L. Downes, M.J. Isaac, A.J. Tulloch andI.M. Turnbull (Institute of Geological & Nuclear Sciences),and M.R Johnston (Nelson).

Funding for the QMAP project was provided by theFoundation for Research, Science & Technology undercontract C05X0003. The base map is sourced from LandInformation New Zealand. Crown copyright reserved.

51

52

REFERENCES

Adams, CJ.; Harper, C.T.; Laird, M.G. 1975: K-Ar ages oflowgrade metasediments of the Greenland and Waiuta Groupsin Westland and Buller, New Zealand. New Zealand JournalofGeology and Geophysics 18: 39-48.

Adams, C.J.; Nathan, S. 1978: Cretaceous chronology of thelower Buller valley, South Island, New Zealand. NewZealand Journal ofGeology and Geophysics 21: 455-62.

Anderson, H.; Webb, T.H. 1994: New Zealand seismicity:patterns revealed by the upgraded National SeismographNetwork. New Zealand Journal ofGeology and Geophysics37: 477-93.

Angus, P.V. 1984: Geology ofInchbonnie, Westland. BSc (Hons)thesis, University of Otago, Dunedin.

Barry, lM.; Duff, S.w.; MacFarlan, DAB. 1994: Coal resourcesof New Zealand. Resource Inforrrultion Report 16. Energyand Resources Division, Ministry ofCommerce, Wellington,New Zeaiand.

Bates, T.E. 1989: Bald Hill molybdenum prospect. AustralasianInstitute ofMining & Metallurgy Monograph 13 : 137-138.

Beavan, l; Haines, J. 2001: Contemporary horizontal velocityand strain rate fields ofthe Pacific-Australian plate boundaryzone through New Zealand. Journal of GeophysicalResearch 106: 741-770.

Beavan, J.; Tregoning, P.; Bevis, M.; Kato, T.; Meertens C. inpress: The motion and rigidity of the Pacific Plate andimplications for plate boundary deformation. Journal ofGeophysical Research.

Beck, kC.; Reed, J.J.; .Willet, R.W. 1958: Uraniummineralisation in the Hawks Crag Breccia of the LowerBuller Gorge region, South Island, New Zealand. NewZealand Journal ofGeology and Geophysics 1: 432-50.

Becker, J.A.; Craw, D. 2000: Structure and neotectonics on theMain Divide, upper Wilberforce valley, mid Canterbury, NewZealand. New Zealand Journal ofGeology and Geophysics43: 217-28.

Becker, J.A.; Craw, D.; Horton, T.; Chamberlain, C.P. 2000:Gold mineralisation near the Main Divide, upper Wilberforcevalley, Southern Alps, New Zealand. New Zealand JournalofGeology and· Geophysics 43: 199-215.

Begg, J;G.; Johnston, M.R.2ooo: Geology of the Wellingtonarea. Institute ofGeological & Nuclear Sciences 1:250000geological map /0. 1 sheet + 64p.

Bell, J.M.; Fraser, C. 1906: The geology of the Hokitika sheet,north Westland quadrangle. New Zealand Geological SurveyBulletin 1. 101 p.

Berryman, K.R. 1980: Late Quaternary movement on the WhiteCreek Fault, South Island, New Zealand. New ZealandJournal ofGeology and Geophysics 23: 93-102.

Berryman, KR.; Beanland, S.; Cooper, A. F.; Cutten, H. N.;Norris, R. J.; Wood, P. R. 1992: The Alpine Fault, NewZealand: variation in Quaternary structural style andgeomorphic expression. Annales Tectonicae 6: 126-163.

Bishop, D.G. 1974: Stratigraphic, structural and metamorphicrelationships in the Dansey Pass area, Otago, New Zealand.New Zealand Journal of Geology and Geophysics17: 301-55.

Bishop, D.G.; Bradshaw, J.D.; Landis, C.A. 1985: Terrane mapof the South Island, New Zealand. In Howell, D. G. ed.Tectonostratigraphic terranes of the Circum-Pacific region.Circum-Pacific Council for Energy and Mineral Resources,Earth Science Series 1. pp. 24-31.

Blackmore, SJ. 1998: Structural and engineering geology ofBaldRange and Kellys Hill, Southern Alps. MSc thesis, UniversityofAuckland, Auckland.

Botsford, J.w. 1983: The Esk Head Melange in the Esk Head!Okuku area, North Canterbury. MSc thesis, University ofCanterbury, Christchurch.

Bowen, F.E. 1964: Sheet 15 - Buller. Geological Map of NewZealand 1:250 000. Wellington, New Zealand, Departmentof Scientific and Industrial Research.

Bowen, F.E. 1966: Early Pleistocene glacial and associateddeposits of the West Coast ofthe South Island, New Zealand.New Zealand Journal of Geology and Geophysics 10:164-81.

Bradley, J.P.; Wilkins, C.J.; Oldershaw, w.; Smale, D. 1979: Astudy ofdetrital heavy minerals in the Taramakau catchment.Journal of the Royal Society ofNew Zealand 9: 233-251.

Bradley, J.P.; Chew, P.M.; Wilkins, c.J. 2002: Transport anddistribution of magnetite and ilmenite on Westland beachesof New Zealand: with comment on the accumulation ofotherhigh-density minerals. Journal of the Royal Society ofNewZealand 32: 169-81.

Bradshaw, J.D. 1973: Allochthonous Mesozoic fossil localitiesin melange within the Torlesse rocks of north Canterbury.Journal of the Royal Society ofNew Zealand 3: 161-167.

Bradshaw, M.A. 1995: Stratigraphy and structure of the LowerDevonian rocks of the Waitahu and Orlando Outliers, nearReefton, New Zealand, and their relationship to theInangahua Outlier. New Zealand Journal of Geology andGeophysics 38: 81-92.

Bradshaw, M.A. 1999: Lower Devonian bivalves from theReefton Group, New Zealand. Association ofAustralasianPaleontologists Memoir 20: 171.

Bradshaw, M.A. 2000: Base of the Devonian Baton Formationand the question of a pre-Baton tectonic event in the TakakaTerrane, New Zealand. New Zealand Journal of Geologyand Geophysics 43: 601-10.

Bradshaw, M.A.; Hegan, B.D. 1983: Stratigraphy and structureof the Devonian rocks of Inangahua outlier, Reefton, NewZealand. New Zealand Journal ofGeology and Geophysics26: 325-344.

Braithwaite, J.C. 1959: Prospecting activities ofLime and MarbleLtd, Nelson. Fourth mineral conference, School of Minesand Metallurgy, Otago, paper 173. 10 p.

Brathwaite, RL.; Pirajno, F. 1993: Metallogenic map of NewZealand. Institute ofGeological & Nuclear Sciences Monograph3. 2 maps + 215 p.

Brown, M.E.D. 1998: Structural and engineering geology ofthe KellyRange, Arthur's Pass National Park, South Island. MSc thesis,University of Auckland, Auckland.

Browne, G.H. 1987: Geological comments on the Lake Sumner­Harper Pass area, Southern Alps. Unpublished immediate report,file L32171, Institute of Geological & Nuclear Sciences, LowerHutt.

Campbell, J.D.; Warren, G. 1965: Fossil localities of the TorlesseGroup in the South Island. Transactions ofthe Royal Society ofNew Zealand (Geology) 3: 99-137.

Cave, M.P. 1982: Sedimentology, paleontology and structure of theTorlesse rocks and the geological hazards of Arthurs PassNational Park. PhD thesis, University of Auckland, Auckland.

Cave, M.P. 1986: Geology of Arthur's Pass National Park. NationalPark Scientific Series. Department of Lands and Survey,Wellington, New Zealand.

Cave, M.P.; Lumb, J.T.; Clelland, L. 1993: Geothermal resources ofNew Zealand. Resource Information Report. Energy andResources Division, Ministry of Commerce, Wellington,New Zealand.

Chinn, T.J. 1973: Unpublished Field Notes, file K33171, Institute ofGeological & Nuclear Sciences, Lower Hutt.

Christie, AB. 1989: Computerised minerals bibliography usersguide. New Zealand Geological Survey report M 161.48 p.

Coates, G.F. 1988: Guide to the Pancake Rocks, Punakaiki.InstituteofGeological & Nuclear Sciences Natural History Brochure 2.5 p.

Coleman, AC. 1981: Parts of Sheets S18, S19, S25, & S26 ­Wangapeka. Geological Map of New Zealand 1:63 360.Wellington,. New Zealand, Department of Scientific andIndustrial Research.

Cooper, R.A. 1974: Age ofthe Greenland and Waiuta Groups, SouthIsland, New Zealand. New Zealand Journal of Geology andGeophysics 17: 955-962.

Cooper, RA 1979: Lower Paleozoic rocks of New Zealand. Journalof the Royal Society ofNew Zealand 9: 29-84.

Cooper, R.A. 1989: Early Paleozoic terranes of New Zealand.Journal of the Royal Society ofNew Zealand 19: 73-112.

Cooper, RA 1992: Paleozoic rocks of the Springs Junction area.Unpublished map, file L31171, Institute ofGeological & NuclearSciences, Lower Hutt.

Cooper, RA 1997: The Balloon Melange and early Paleozoic historyof the Takaka Terrane, New Zealand. Terrane Dynamics 97:10-14. Christchurch, New Zealand.

Cooper, R.A.; Tulloch, AJ. 1992: Early Paleozoic terranes in NewZealand and their relationship to the Lachlan Fold Belt.Tectonophysics 214: 129-44.

Crampton, J.S.; Beu, AG.; Campbell, H.J.; Cooper, RA; Morgans,H.E.G.; Raine, J.I.; Scott, G.H.; Stevens, G.R.; Strong, C.P.;Wilson, G.J. 1995: All interim New Zealand time scale. InstituteofGeological. & Nuclear Sciences science report 9519. 5 p.

Craw, D. 1984: Lithologic variations in Otago Schist, Mt Aspiringarea, northwest Otago. New Zealand Journal of Geology andGeophysics 27: 151-166.

Craw, D.; Youngson, J.H.; Koons, P.O. 1999: Gold dispersal andplacer formation in an active oblique collisional mountain belt,Southern Alps, New Zealand. Economic Geology 94: 605-614.

Cutten, H.N.C. 1976: The Rappahannock Group: late Cenozoicsedimentation and tectonics in the Alpine Fault zone in southeastNelson. MSc thesis, University of Canterbury, Christchurch.

Cutten, H.N.C. 1979: Rappahannock Group: late Cenozoicsedimentation and tectonics contemporaneous with Alpine Faultmovement. New Zealand Journal of Geology and Geophysics22: 535-53.

DeMets, C.; Gordon, RG.; Argus, D.E; Stein, S. 1990: Current platemotions. Geophysical Journal International 101: 425-478.

Dixon, M. 2001: An interpretation of the metamorphic history ofthe Alpine Schist, northern Westland. MSc thesis, VictoriaUniversity of Wellington, Wellington.

Downes, G.L. 1995: Atlas of isoseismal maps of New Zealandearthquakes. Institute of Geological & Nuclear Sciences·Monograph 11. 304 p.

Eggers, M.L; Sewell, R.J. 1990: Sheet QM360 Hanmer.Geological Resource Map of New Zealand 1:250 000.New Zealand Geological Survey report M 173. 2 enclosures+43 p.

Farmer, RT. 1967: Stratigraphy and structure of Palaeozoic rocksnear Springs Junction, southwest Nelson. MSc thesis, Universityof Canterbury, Christchurch.

Field, B.D.; Browne, G.H. 1989: Cretaceous and Cenozoicsedimentary basins and geological evolution of the Canterburyregion, South Island, New Zealand. New Zealand GeologicalSurvey Basin Studies 2. 4 sheets + 94 p.

Findlay RH. 1979: Age and structure ofTorlesse rocks (CanterburySuite), Otira Gorge, Westland, New Zealand. New ZealandJournal of Geology and Geophysics 22: 285-89.

Flores, R.M.; Sykes, R. 1996: Depositional controls on coaldistribution and quality in the Eocene Brunner Coal Measures,BulJer Coalfield, South Island, New Zealand. InternationalJournal of Coal Geology 29: 291-336.

Fyfe, H.E. 1929: Movement on the White Creek Fault, New Zealand,during the Murchison earthquake of 17 June 1929. New ZealandJournal of Science and Technology 11: 192-97.

Fyfe, H.E. 1968: Geology of the Murchison subdivision. NewZealand Geological Survey Bulletin 36. 12 maps + 52 p.

Gage, M. 1945: The Tertiary and Quaternary geology of Ross,Westland. Transactions of the Royal Society of New Zealand75: 138-59.

Gage, M. 1948: The geology of the Reefton quartz lodes. NewZealand Geological Survey Bulletin 42. 6 maps + 69 p.

Gage, M. 1952: Greymouth Coalfield. New Zealand GeologicalSurvey Bulletin 45. 14 maps + 232 p.

Gage, M.; Wellman, H.W. 1944: Petroleum in coal measures atGreymouth. New Zealand Journal ofScience & Technology B26:140-43.

53

54

Gair, H.S. 1962: Notes on the geology of the Esk Valley, Canterbury.New Zealand Journal of Geology and Geophysics 5: 531-44.

Gradstein, EM.; Ogg, J. 1996: A Phanerozoic time scale. Episodes19: 3-5.

Grapes, R.; Palmer, K 1996: (Ruby-Sapphire)-chromian mica­tourmaline rocks from Westland, New Zealand. Journal ofPetrology 37: 293-315.

Gregg, D.R. 1964: Sheet 18 - Hurunui. Geological Map of NewZealand 1:250 000. Wellington, New Zealand, Department ofScientific and Industrial Research.

Griffiths, G.A.; McSaveney, M.J. 1983: Distribution of mean annualprecipitation across steepland regions of New Zealand. NewZealand Journal of Science 26: 197-209.

Grindley, G~w. 1980: Sheet Sl3 - Cobb. Geological Map of NewZealand 1:63 360. Wellington, New Zealand, Department ofScientific and Industrial Research.

Hancox, G.T.P.; Perrin, N.D.; Dellow, G.D. in press: Recent studiesof historical earthquake-induced landsliding, ground damage,and MM intensity in New Zealand. Bulletin ofthe New ZealandSociety for Earthquake Engineering.

Henderson, J. 1917: The geology and mineral resources of theReefton subdivision, Westport and North Westland divisions.New Zealand Geological Survey Bulletin 18. 14 maps + 232 p.

Henley; RW.; Adains, J. 1979: On the evolution ofgiant gold placers.Transactions o/the Institution of Mining and Metallurgy 88:B41-50.

Hunt, T.M.; Nathan, S. 1976: Inangahua magnetic anomaly, NewZealand. New Zealand Journal ofGeology and Geophysics 19:395-406.

Hutton, C.O. 1950: Studies of heavy detrital minerals. Bulletin ofthe Geol?gical Society ofAmerica 61: 635-716.

Hutton, e.O.; Turner, FJ. 1936: Metamorphic zones in north-westOtago. Transactions of the Royal Society ofNew Zealand 65:405-6.

Inwood, K.S. 1997: Geologic setting, gravity collapse and hazardassessment of the Kongahu Fault Zone, Westport. MSc thesis,University of Canterbury, Christchurch.

Ireland, T.R 1992: Crustal evolution ofNew Zealand: evidence fromage distributions of detrital zircons in Western Provinceparagneisses and Torlesse greywacke. Geochimica etCosmochimica Acta 56: 911-20.

Ireland, T.R.; Reay, A.; Cooper, A. E 1984: The Pounamu UltramaficBelt in the Diedrich Range, Westland, New Zealand. NewZealand Journal of Geology and Geophysics 27: 247-256.

Ireland, T.R; Gibson, G.M. 1998: SHRIMP monazite and zircongeochronology of high-grade metamorphism in New Zealand.Journal of Metamorphic Geology 16: 149-67.

Johnston, M.D. 1988: Geology of the Rotokohu Coal Measures,Inangahua Valley, Buller, New Zealand. Ministry ofEnergy CoalGeology Report 8. 30 p.

.Johnston, M.R. 1983: Nephrite in the Pounamu Formation, McArthurCrags, Olderog Creek, Arahura valley. Industrial Minerals andRocks (New Zealand Geological Survey) 8: 5-8.

Johnston, M.R.; Mackinnon, D.I.; Mew, G. 1980: Early Devoniano(Emsian) fossils from the Lake Haupiri area, North Westland.New Zealand Journal ofGeology and Geophysics 23: 391-394.

Jongens, R. 1997: The Anatoki Fault and the structure of the adjacentBuller and Takaka Terrane rocks, northwest Nelson, NewZealand. PhD thesis, University of Canterbury, Christchurch.

Jury, A.P. 1981: Mineralization at Mt Rangitoto and Mt Greenland,Westland. MSc thesis, University of Canterbury, Christchurch.

Kamp, P.J.; Webster, KS.; Nathan, S. 1996: Thermal history analysisby integrated modelling of apatite fission track and vitrinitereflectance data: application to an inverted basin (BullerCoalfield, New Zealand). Basin Research 8: 383-402.

Kimbrough, D.L.; Tulloch, A.J. 1989: Early Cretaceous age oforthogneiss from the Charleston Metamorphic Group, NewZealand. Earth & Planetary Science Letters 95: 130-40.

Koons, P.O. 1978: The Pounamu ultramafics: a study ofmetasomatism. MSc thesis, University of Otago, Dunedin.

Laird, M.G. 1972: Sedimentology of the Greenland Group in thePaparoa Range, West Coast, South Island. New Zealand Journalof Geology and Geophysics 15: 372-393.

Laird, M.G. 1988: Sheet S37 - Punakaiki. Geological Map of NewZealand 1:63 360. Wellington, New Zealand, Department ofScientific and Industrial Research.

Laird, M.G. 1995: Coarse-grained lacustrine fan-delta deposits(Pororari Group) of the northwestern South Island, New Zealand:evidence for Mid-Cretaceous rifting. International Associationfor Sedimentology Special Publication 22: 197-217.

Laird, M.G.; Shelley, D. 1974: Sedimentation and early tectonichistory of the Greenland Group, Reefton, New Zealand. NewZealand Journal of Geology and Geophysics 17: 839-854.

LeMasurier, W.E.; Landis, C.A. 1996: Mantle-plume activityrecorded by low-relief erosion surfaces in west Antarctica andNew Zealand. Bulletin of the Geological Society of America108: 1450-66.

Lensen, G.J.; Suggate, R.P. 1969: Inangahua e,arthquake: apreliminary account of the geology. DSIR Bulletin 193: 17-36.

Marshall, P. 1929: Building stones of New Zealand. DSIR BulletinIJ. 47 p.

Mason, B.; Taylor, S.R 1987: High-grade basement gneisses andgranitoids in Westland, New Zealand. Journal of the RoyalSociety ofNew Zealand 17: 115-138.

MacKinnon, T.C. 1980: Geology ofMonotis-bearing Torlesse rocksin Temple Basin near Arthur's Pass, South Island, New Zealand.New Zealand Journal of Geology and Geophysics 23: 63-81.

McLean, G.w. 1986: Structure and metamorphism near the Alpineand Awatere Faults, Lewis Pass. MSc thesis, University ofCanterbury, Christchurch.

McPherson, R.I. 1978: Geology of Quaternary ilmenite-bearingcoastal deposits at Westport. New Zealand Geological SurveyBulletin 87. 95 p.

McPherson, RI.; Roser, B.P.; Suggate, R.P.; Christie, A.B.; Nathan,S.; Deeley, J.M.; Mackwell, J.A.; Leslie, M.G.; Brooker, M.;Doole, M.H.; Brown, M.J.; 1994: Sheet QM359 Greymouth.Geological Resource Map of New Zealand 1:250000. InstituteofGeological & Nuclear Sciences science report 94/13. 2 maps+ 2 enclosures + 91 p.

McSaveney, M.J.; Whitehouse, I. 1989: Anthropic erosion ofmountain land in Canterbury. New Zealand Journal ofEcology12: 151-163.

Martinson, D.G.; Pisias, N.G.; Hays, J.D.; Imbrie, J.; Moore, T.e.;Shackleton, N.J. 1987: Age dating and the orbital theory of theice ages: development of a high resolution 0 to 300 000 yearchronostratigraphy. Quaternary Research 27: 1-29.

Maxwell, M.G. 1982: The geology and mineralisation of PL 31­1192 Doctor Hill, South Island. New Zealand unpublished miningcompany report MR 871 for Gold Mines NZ Ltd. Ministry ofEconomic Devlopment, Wellington.

Minehan, P.J. 1989: The occurrence and identification of economicdetrital minerals associated with alluvial gold mining in NewZealand. Australasian Institute of Mining and MetallurgyMonograph 13: 159-67.

. Modriniak, N.; Marsden, E.1938: Experiments in geophysical surveyin New Zealand. Department of Scientific and IndustrialResearch Geological Memoir 4. 92 p.

Mongillo, M.A; Clelland, L. 1984: Concise listing of informationon the thermal areas and hot springs of New Zealand. DSIRGeothermal Report 9. 228 p.

Morgan, P.G. 1908: The geology of the Mikonui Subdivision, NorthWestland. New Zealand Geological Survey Bulletin 6. 12 maps+ 175 p.

Morgan, P.G.1911: The geology ofthe Greymouth subdivision, northWestland. New Zealand Geological Survey Bulletin 13. 8 maps+ 159 p.

Morgan, P.G.; Bartrum, J.A. 1915: The geology and mineral resourcesof the Buller-Mohikinui subdivision, Westport Division. NewZealand Geological Survey Bulletin 17. 9 maps + 210 p.

Morrell; WP. 1968: The Gold Rushes (2nd edition). A & C Black,London.

Mortimer, G. 1984: Report on reconnaissance investigation ofCampCreek Catchment, Alexander Range. Unpublished immediatereport, file K32171, Institute of Geological & Nuclear Sciences,Lower Hutt.

Mortimer, N. 1993a: Geology ofthe Otago Schist and adjacent rocks.Institute .ofGeological & Nuclear Sciences geological map 7.

Mortimer, N. 1993b: Metamorphic zones, terranes and Cenozoicfaults in the Marlborough Schist, New Zealand. New ZealandJournal of Geology and Geophysics 36: 357-368.

Mortimer, N. 1995: Origin of the Torlesse terrane and coeval rocks,North Island, New Zealand. International Geology Review 36:891-910.

Mortimer, N.; Parkinson, D.; Raine, J.I.; Adams, C.J.; Graham, I.J.;Oliver, P.J.; Palmer, K. 1995: Ferrar magmatic province rocksdiscovered in New Zealand: implications for Mesozic Gondwanageology. Geology 23: 185-88.

Mortimer,N.; Smale, D. 1996: Petrology of the Topfer Formation:first Triassic Gondwana sequence from New Zealand. AustralianJournal of Earth Sciences 43: 467-477.

Mortimer, N.; Sutherland, R; Nathan, S. 2001: Torlesse greywackeand Haast schist source for Pliocene conglomerates near Reefton.New Zealand Journal ofGeology and Geophysics 44: 105-112.

Muir, R.J.; Ireland, T.R; Weaver, S.D.; Bradshaw, J.D. 1994: Ionmicroprobe U-Pb zircon geochronology of granitic magmatismin the Western Province of the South Island, New Zealand.Chemical Geology (Isotope Geoscience Section) II3: 171-89.

Muir, R.J.; Weaver, S.D.; Bradshaw, J.D.; Eby, G.N.; Evans, J.A.;Ireland, T.R 1996: Geochemistry of the Karamea Batholith, NewZealand and comparisons with the Lachlan Fold Belt granitesof SE Australia. Lithos 39: 1-20.

Muir, RJ.; Ireland, T.R; Weaver, S.D.; Bradshaw, J.D. 1996: Ionmicroprobe dating ofPaleozoic granitoids: Devonian magmatismin New Zealand and correlations with Australia and Antarctica.Chemical Geology /27: 191-210.

Muir, RJ.; Ireland, T.R; Weaver, S.D.; Bradshaw, J.D.; Waight, T.E.;Jongens, R.; Eby, G.N. 1997: SHRIMP U-Pb geochronology ofCretaceous magmatism in northwest Nelson-Westland, SouthIsland, New Zealand. New Zealand Journal of Geology andGeophysics 40: 453-63.

Muir, RJ.; Ireland, T.R.; Weaver, S.D.; Bradshaw, J.D.; Evans. J.A.;Eby, G.N.; Sheely, D. 1998: Geochronology and geochemistryof a Mesozoic magmatic arc system, Fiordland, New Zealand.Journal of the Geological Society of London ISS: 1037-52.

Munden, EW 1952: Notes on the Alpine Fault, Haupiri Valley, NorthWestland. New Zealand Journal ofScience & Technology B33:404-408.

Mlinker, C.; Cooper, R.A. 1995: The island arc setting of a NewZealand Cambrian volcano-sedimentary sequence: implicationsfor the evolution of the SW Pacific Gondwana fragments.Journal of Geology 103: 687-700.

Mlinker, C.; Cooper, RA. 1999: The Cambrian arc complex of theTakaka Terrane, New Zealand: an integrated stratigraphical,paleontological and geochemical approach. New ZealandJournal of Geology and Geophysics 42: 415-445.

Nathan, S. 1974a: Petrology ofthe Berlins Porphyry: a study of thecrystallisation of granitic magma. Journal ofthe Royal SocietyofNew Zealand 4: 463-483.

Nathan, S. 1974b: Stratigraphic nomenclature for the Cretaceous­lower Quaternary rocks of Buller and north Westlaqd, WestCoast, New Zealand. New Zealand Journal of Geology andGeophysics 17: 423-445.

Nathan, S. 1975: Sheets S23 & S30 - Foulwind and Charleston.Geological Map of New Zealand 1:63 360. Wellington, NewZealand, Department of Scientific and Industrial Research.

Nathan, S. 1976a: Geochemistry of the Greenland Group (earlyOrdovician), New Zealand. New Zealand Journal of Geologyand Geophysics 19: 683-706.

Nathan, S. 1976b: Sheets S23/9 & S2417 - Foulwind and Westport.Geological Map of New Zealand 1:25 000. Wellington, NewZealand, Department of Scientific and Industrial Research.

Nathan, S. 1977: Preliminary geological report on the Ahaura area,north Westland. New Zealand Geological Survey report M 60(Appendix B). 1 map + 4p.

Nathan, S. 1978a: Sheet S44 - Greymouth. Geological Map of NewZealand 1:63 360. Wellington, New Zealand, Department ofScientific and Industrial Research.

55

56

Nathan, S. 1978b: Sheets S31 & part S32 - Buller-Lyell. GeologicalMap of New Zealand 1:63 360. Wellington, New Zealand,Department of Scientific and Industrial Research.

Nathan, S. 1993: Revising the 1:250000 Geological Map of New.Zealand - a discussion paper. Institute of Geological & NuclearSciences science report 93/26. 28 p.

Nathan, S. 1994: Geology of the Reefton Goldfield. Unpublishedmap, file L31, Institute of Geological & Nuclear Sciences,Lower Hutt.

Nathan, S. 1996: Geology ofthe Buller Coalfield, 1:50 000. Instituteof Geological & Nuclear Sciences geological map 23.

Nathan, S.; Anderson, H.J.; Cook, RA.; Herzer, RH.; Hoskins, R.H.;Raine, J.I.; Smale, D. 1986: Cretaceous and Cenozoicsedimentary basins of the West Coast region, South Island, NewZealand. New Zealand Geological Survey Basin Studies I. 4sheets + 99 p.

Nathan, S.;' Thurlow, C.; Warnes, P.; Zucchetto, R. 2000:Geochronology database for New Zealand rocks (2nd edition):1961-99. Institute of Geological & Nuclear Sciences sciencereport 2000/1. 51 p.

Nicholson, D.S. 1955: Wartime search for uranium in New Zealand.New Zealand Journal ofScience and Technology 36: 375-96.

Newman J.; Bradshaw, J.D. 1981: Oligocene-Miocene rocks of theBrechinBurn outlier, Waimakariri valley, Canterbury. NewZealand Jo~nial of Geology and Geophysics 24: 469-76.

Norris, RJ.; Cooper, A.E 2000: Late Quaternary slip rates and slippartitioning on the Alpine Fault, New Zealand. Journal ofStructural.Geology 23: 507-520.

Parish, R, 1998: Metamorphism of the Alpine Schist in the NorthWestland region. BSc (Hons) thesis, Victoria University ofWellington, Wellington.

Petrie, J.M. 1974: Chaotic Mesozoic rocks of the Studleigh Range,North Canterbury, New Zealand. MSc thesis, University ofCanterbury, Christchurch.

Pirajno, EB.; Bentley, P.N. 1985: Greisen-related scheelite, goldand sulphide mineralisation at Kirwans Hill and Bateman Creek,Reefton district, Westland, New Zealand. New Zealand Journalof Geology and Geophysics 28: 97-109.

Price, G.D. 1984: Final report on EL 33147 Paparoa Range, WestCoast, New Zealand. New Zealand unpublished mining companyreport MR 739 for CRA Exploration Proprietary Limited.Ministry of Economic Development, Wellington.

Quek, S.w. 1976: Cambrian-Ordovician sediments in SW Nelsondistrict. MSc thesis, University of Canterbury, Christchurch.

Raine, J.I. 1984: Outline of a palynological zonation of Cretaceousto Paleogene terrestrial sediments in the West Coast region, SouthIsland, New Zealand. New Zealand Geological Survey report109.82 p.

Raine, J.1. 1994: Terrestrial Kff boundary studies in New Zealand.Paleoaustral2: 9-12.

Rattenbury, M.S. 1987: Timing of mylonitisation west of the AlpineFault, central Westland, New Zealand. New Zealand JournalpfGeology and Geophysics 30: 287-297.

Rattenbury, M.S. 1991: The Fraser Complex: High-grade gneisses,igneous and mylonitic rocks in central Westland, New Zealand.New Zealand Journal of Geology and Geophysics 34: 23-33.

Rattenbury, M.S.; Cooper, RA; Johnston, M.R 1998: Geology ofthe Nelson area. Institute of Geological & Nuclear Sciences1:250000 geological map 9. 1 sheet + 67 p.

Rattenbury, M.S.; Heron, D.W. 1997: Revised procedures andspecifications for the QMAP GIS. Institute of Geological &Nuclear Sciences science report 97/3. 52 p.

Rattenbury, M.S.; Stewart, M. 2000: The structural setting of theGlobe-Progress and Blackwater gold mines, Reefton goldfield,New Zealand. New Zealand Journal ofGeology and Geophysics43: 435-46.

Rhoades, D.A; Van Dissen, RJ. 2000: Probability of rupture of theAlpine Fault allowing for uncertainties. EQC Research Report991388, prepared by the Institute of Geological & NuclearSciences Ltd . 23 p.

Roder, G.; Suggate, RP. 1990: Sheet L29BD - Upper Buller Gorge.Geological Map of New Zealand 1:50 000. Wellington, NewZealand, Department of Scientific and Industrial Research.

Roser, B.P.; Grapes, R 1990: Geochemistry of a metabasite-chert­coloured argillite- turbidite association at Red Rocks,Wellington, New Zealand. New Zealand Journal of Geologyand Geophysics 33: 181-191.

Roser, B.P.; Cooper, R.A.; Nathan, S.; Tulloch, A.J. 1996:Reconnaissance sandstone geochemistry, provenance, andtectonic setting of the lower Paleozoic terranes of the West Coastand Nelson, New Zealand. New Zealand Journal of Geologyand Geophysics 39: 1-16.

Roser, B.P.; Nathan, S. 1997: An evaluation of element mobilityduring metamorphism ofa turbidite sequence (Greenland Group,New Zealand). Geological Magazine 134: 219-34.

Sewell, RJ.; Nathan, S.; Adams, C.J. 1988: Geochemistry of lateCretaceous basaltic rocks from North Westland. New ZealandGeological Survey Record 35: 113-121.

Shelley, D. 1970: The structure and petrography o~ the ConstantGneiss near Charleston, SW Nelson. New Zealand Journal ofGeology and Geophysics 13: 370-91.

Sibson, R.H.; White, S.H.; Atkinson, B.K. 1979: Fault rockdistribution and structure within the Alpine Fault Zone: apreliminary account. Bulletin of the Royal Society of NewZealand 18: 55-65.

Silberling, N.J.; Nichols, K.M.; Bradshaw, J.D.; Blome, C.D. 1988:Limestone and chert in tectonic blocks from the Esk Headsubterrane, South Island, New Zealand. Bulletin of theGeological Society ofAmerica 100: 1213-1223.

Smale, D.; Campbell, H.; Grapes, R; Mortimer, N.; Raine, J.1. 1996:Perrnianffriassic sedimentary sequences in north-western SouthIsland, New Zealand, and correlation with Australian Gondwanasequences. In Mesozoic 96, Geological Society of Australia.pp.51O-16.

Spell, T.L.; McDougall, I.; Tulloch, AJ. 2000: Thermochronologicconstraints on the breakup of th,e Pacific Gondwana margin: thePaparoa Metamorphic Compl¢x, South Island, New Zealand.Tectonics 19: 433-51. '

Stirling, M.W.; Wesnousky, S.G.; Berryman, K.R. 1998: Probabilisticseismic hazard analysis of New Zealand. New Zealand Journalof Geology and Geophysics 41: 355-75.

Suggate, R.P. 1957: The geology of Reefton subdivision. NewZealand Geological Survey Bulletin 56. 8 maps + 146 p.

Suggate, RP. 1963: The Alpine Fault. Transactions of the RoyalSociety ofNew Zealand (Geology) 2: 105-29.

Suggate, RP. 1965: Late Pleistocene geology ofthe northern part ofthe South Island, New Zealand. New Zealand Geological SurveyBulletin 77. 91 p.

Suggate, R.P. 1968: The thirty-foot raised beach at Rapahoe, northWestland. New Zealand Journal of Geology and Geophysics11: 648-50.

Suggate, RP. 1984: Sheet M29AC - Mangles Valley. GeologicalMap of·New Zealand 1:50000. Department of Scientific andIndustrial Research, Wellington, New Zealand.

Suggate, RP. 1987: Active folding in north Westland, New Zealand.New Zealand Journal ofGeology and Geophysics 30: 169-74.

Suggate, R.P. 1988: Quaternary deposition and deformation in theBuller and tributary valleys. New Zealand Geological SurveyRecord 25. 51 p.

Suggate, R.P. 1989: The postglacial shorelines and tectonicdevelopment ofthe Barrytown coastal lowland, north Westland,New Zealand. New Zealand Journal ofGeology and Geophysics32: 443-50.

Suggate, RP. 1990: Vertical displacement associated with the WhiteCreek Fault accompanying the 1929 Murchison (New Zealand)earthquake. New Zealand Geological Survey report EDS 131.23p.

Suggate, R.P. 1992: Differential uplift ofmiddle and late Quaternaryshorelines, northwest South Island, New Zealand. QuaternaryInternational i5/16: 47-59.

Suggate, R.P.; Gair, H.S.; Gregg, D.R. 1961: The south-westextension ofthe Awatere Fault. New Zealand Journal ofGeologyand Geophysics 3: 264-69.

Suggate, RP.; Munden F.w. 1952: Waiheke River. Unpublishedimmediate report, file L32nI, Institute ofGeological & NuclearSciences, Lower Hutt.

Suggate, RP.; Stevens, G.R.; Te Punga, M.T. 1978: The Geology ofNew Zealand (2 volumes). Wellington, New Zealand,Government Printer. 820 p.

Suggate, R.P.; Waight, T. 1998: Geology ofthe Kumara-Moana area.Institute ofGeological & Nuclear Sciences geological map 24.1 map + 120 p.

Titheridge, D.G. 1993: The influence ofhalf-graben syn-depostionaltilting on thickness variation and seam splitting in the BrunnerCoal Measures, New Zealand. Sedimentary Geology 87: 195­213.

Tulloch, AJ. 1978: Plutonic and metamorphic rocks in the VictoriaRange segment of the Karamea Batholith. PhD thesis,University of Otago, Dunedin.

Tulloch, AJ. 1983: Granitoid rocks of New Zealand - a brief review.Geological Society ofAmerica Memoir 15: 5-20.

Tulloch, AJ. 1988: Batholiths, plutons and suites: nomenclature forgranitoid rocks of Westland-Nelson. New Zealand Journal ofGeology and Geophysics 31: 505-509.

Tulloch, AJ. 1989: Magnetic susceptibilities of Westland-Nelsonplutonic rocks: discrimination of Paleozoic and Mesozoicgranitoid suites. New Zealand Journal of Geology andGeophysics 32: 197-204.

Tulloch, A.J. 1995: Geological map of the Victoria RangeUnpublished map, file L31, Institute of Geological & NuclearSciences, Lower Hutt.

Tulloch, AJ.; Brathwaite, RL. 1986: Granitoid rocks and associatedmineralisation of Westland-West Nelson, New Zealand. NewZealand Geological Survey Record 13: 65-92.

Tulloch, A.J.; Mackenzie, I.F. 1986: Tin-tungsten mineralisedgranites in New Zealand. Bureau ofJ'r{ineral Resources record1986/10: 75-76.

Tulloch, AJ.; Kimbrough, D. L. 1989: The Paparoa metamorphiccore complex, New Zealand; Cretaceous extension associatedwith fragmentation of the Pacific margin ofGondwana. Tectonics8: 1217-1235.

Tulloch, AJ.; Palmer, K. 1990: Tectonic implications of granitecobbles from the mid-Cretaceous Pororari Group, southwestNelson, New Zealand. New Zealand Journal of Geology andGeophysics 33: 205-217.

Turnbull,I.M. 1988: Sheet S133 - Cromwell. Geological Map ofNew Zealand 1:63360. Wellington, New Zealand,Departmentof Scientific & Industrial Research.

Turnbull, I.M. 2000:· Geology of the Wakatipu area. Institute ofGeological & Nuclear Sciences 1:250000 geological map 18.I sheet + 72 p.

Turnbull, I.M.; Forsyth, P.J. 1986: Schist structure east of the AlpineFault bends, southeast Nelson, New Zealand. New ZealandJournal of Geology and Geophysics 29: 165-77.

Turnbull, I.M.; Mortimer, N.; Craw, D. 2001: Textural zones in theHaast Schist - a reappraisal. New Zealand Journal of Geologyand Geophysics 44: 171-83.

Suggate, RP.; Wood, P.R. 1979: Inangahua earthquake - damage tohouses. New Zealand Geological Survey report 85. 58 p.

Taylor, P.e. 1999: New Zealand coal resource survey programme1976-1989. Wellington, Crown Minerals, Ministry ofCommerce. 55 p.

Thrasher, G,P.; Suggate, R.P.; Funnell, R.H. 1996: The KotukuAnticline, West Coast, South Island, Proceedings of the 1996Petroleum Conference: 71-75.

Vajda, Y.R.; Raine, J.I.; Hollis, C.J. 2001: Indication of globaldeforestation at the Cretaceous-Tertiary boundary by NewZealand fern spike. Science 294: 1700-02.

Waight, T.E. 1995: The geology and geochemistry of the HohonuBatholith and adjacent rocks, North Westland, New Zealand.PhD thesis, University of Canterbury, Christchurch.

Waight, T.E.; Weaver, S.D.; Ireland, T.R; Maas, R.; Muir, RJ.;Shelley, D. 1997: Field characteristics, petrography, andgeochronology ofthe Hohonu Batholith and the adjacent GraniteHill Complex, North Westland, New Zealand. New ZealandJournal of Geology and Geophysics 40: 1-17.

57

S8

Waight, T.E.; Weaver, S.D.; Muir, R.J. 1998a: Mid-Cretaceousgranitic magmatism during the transition from subduction toextension in southern New Zealand: a chemical and tectonicsynthesis. Lithos 45: 469-82.

Waight, T.E.; Weaver, S.D.; Maas, R.; Eby, G.N. 1998b: FrenchCreek Granite and Hohonu Dike Swarm, South Island, NewZealand: Late Cretaceous alkaline magmatism and the openingof the Tasman Sea. Australian Journal of Earth Sciences 45:823-45.

Warren, G. 1967: Sheet 17 - Hokitika. Geological Map ofNew Zealand 1:250 000. Wellington, New Zealand, Departmentof Scientific and Industrial Research.

Wellman, H.W. 1945: Geology of Coal Creek, Ross. New ZealandJournal ofScience and Technology B27: 8-14.

Wellman H.W. 1950: Tertiary geology of Sheet S51 (Kumara), withnotes on the Cretaceous and Tertiary outliers to the south (S57,S58, S64). Unpublished manuscript and map held in the Library,Institute bf Geological & Nuclear Sciences, Lower Hutt.

Wellman, H.W. 1951: Paparoa-Bronner contact near Greymouth.New Zealand Journal ofScience and Technology B32: 9-17.

Wellman, H.W. 1953: .Data for the study of Recent and LatePleistocene faulting in the South Island of New Zealand. NewZealand Journal ofScience and Technology B34: 270-288.

Wellman, H.W. 1971: Geology of the Kotuku Oilfield, Westland.New Zealand Geological Survey report 48. 46 p.

Wellman, H.W.; Grindley, G.w.; Munden, EW. 1952: The AlpineSchists and the Upper Triassic ofHarpers Pass (sheet S52), SouthIsland, New Zealand. Transactions ofthe Royal Society ofNewZealand 80: 213-227.

Wells, A.; Stewart, G.H.; Duncan, R.P. 1998: Evidence ofwidespread,synchronous, disturbance-initiated forest establishment inWestland, New Zealand. Journal of the Royal Society of NewZealand28: 333-345.

White,PJ. 1988: The petrology, geochemistry and petrogenesis ofigneous and metamorphic rocks from the Paparoa Range,southwest Nelson, New Zealand. PhD thesis, Victoria Universityof Wellington, Wellington.

White, P.L 1994: Thermobarometry of the CharlestonMetamorphic Group and implications for the evolution of thePaparoa Metamorphic Core Complex, New Zealand. NewZealand Journal of Geology and Geophysics 37: 201-211.

Williams, G.J. 1974: Economic geology of New Zealand (2ndedition). Australasian Institute of Mining and Metallurgy,Monograph 4. 490 p.

Wilson, D.D. 1956: Note on the geology of the Ant Stream Tertiaryoutlier, north Canterbury, New Zealand. New Zealand JournalofScience & Technology B37: 603-605.

Wombacher, E; Miinker, C. 2000: Pb, Nd, and Sr isotopes and REEsystematics of Cambrian sediments from New Zealand:implications for the reconstruction of the early PaleozoicGondwana margin along Australia and Antarctica. Journal ofGeology 108: 663-686.

Wright, C.A. 1998: The AD 930 long-ronout Round Top debrisavalanche, Westland, New Zealand. New Zealand Journal ofGeology and Geophysics 41: 493-497.

Yang, J.S. 1989: Seismotectonic study of the central Alpine Faultregion, South Island, New Zealand. PhD thesis, VictoriaUniversity of Wellington, Wellington.

Young, D.J. 1964: Ganister and silica sand deposits of the WestCoast, South Island. New Zealand Journal of Geology andGeophysics 7: 508-24.

Young, D.J. 1966: Unpublished field maps (scale 1:15 840) of theRoss area, file NZMS lIS57, Institute of Geological & NuclearSciences, Lower Hutt.

Young, D.J. 1967: Oil-bearing Paparoa Coal Measures near Rewanui,Greymouth Coalfield. New Zealand Journal of Geology andGeophysics /0: 666-674.

Young, DJ. 1968: The Fraser Fault in central Westland, New Zealand,and its associated rocks. New Zealand Journal ofGeology andGeophysics II: 291-310.

This full colour map illusrrates the geology of the Greymouth area, which covers the central part of theWest Coast of the South Island. The map is part of a series, initiated in 1996, which will eventually coverthe whole country. Onshore geology, offshore bathymetry, and major structural elements are shown,derived from published and unpublished mapping by GNS, NIWA, university and mineralexploration geologists. All geological data are held in a geographic information system (GIS), and areavailable in digital form, and as thematic maps at different scales. The accompanying, illustrated textsummarises the regional geology, tectonic development, economic geology, engineering geology, andpotential geological hazards.

The QMAP Greymourh area is bisected by the Alpine Fault a major dextral strike-slip fault that formsthe active plate boundary between the Austral ian Plate (to the northwest) and the Pacific Plate (to thesoutheast). This has led to the juxtaposition of rocks of two different geological provinces. To thenorthwest, the pre-Cretaceous rocks are Paleozoic sedimentary and plutonic rocks that represent afragment of the Gondwana supercontinent. On the southeast side of the Alpine Fault the rocks consistof the Torlesse composite terrane a thick, highly deformed sequence of mainly submarine fansedimentary rocks of Permian to Jurassic age. There is a widespread cover of Cenozoic sediments,including late Quaternary glacial and interglacial deposits.

View looking eastwards from the coastl ine near Charleston to the Paparoa Range in thebackground , illustrating the variety of geology in the area. The rock in the foreground is bandedparagneiss (Pecksniff Metasedimentary Gneiss). The flat surface in the centre is an uplifted lastinterglacial terrace (71 000 to 125 000 years), and the forest-covered cliffs are composed ofOligocene limestone.The Paparoa Range is composed of hard, granitoid rocks and paragneiss.

Photo: S. Nathan

ISBN 0-478-09752-2

T OO""9 780473 097523