A. van Vliet

SUBMARINE PANS AND ASSOCIATED DEPOSITS IN THE

LOWER TERTIARY OP GUIPUZCOA (NORTHERN SPAIN).

Proefschrift

ter verkrijging van de graad

van doctor in de landbouwwetenschappen,

op gezag van de rector magnificus

dr. C.C. Oosterlee,

hoogleraar in de veeteeltwetenschap,

in het openbaar te verdedigen

op woensdag 10 november 1982

des namiddags te vier uur in de aula

van de Landbouwhogeschool te Wageningen

: LANDBOUWCATALOGUS

\S\J; 1*>H M ^ C 111 I I I ! 11111 III »m i m • » '

0000 0086 6422

Promotor :

Co-promotor :

Co-referent :

dr. J.D. de Jong, emeritus-hoogleraar

in de geologie

dr. C.W. Drooger, hoogleraar in de

stratigrafie en paleontologie aan

de Rijksuniversiteit Utrecht

dr. P.J.C. Nagtegaal, hoofd afdeling

Exploratie geologisch onderzoek,

Shell-Rijswijk

- II -

CONTENTS

PaSe

Summary IV

I. INTRODUCTION 1

1.1. Scope of the study 1

1.2. Stratigraphie setting 1

1.3. Structural setting 2

1.4. Previous investigations 3

1.5. The need for biostratigraphic control 4

1.6. Nannoplankton biostratigraphy 4

II. SUBMARINE PANS: PHYSIOGRAPHY, DEPOSITIONAL PROCESSES

AND FACIES 7

11.1. Introductory remarks 7

11.2. The emergence of fan models in turbidite

sedimentology 7

11.3. Pan physiography 8

II.4.' Pan facies models 10

11.5. Different levels of sequential organisation 12

11.6. Submarine fans and associated deposits in the

Lower Tertiary of Guipuzcoa 13

III. AREAL SEDIMENTOLOGICAL DESCRIPTION AND INTERPRETATION 18

111.1. Introduction 18

111.2. The Zumaya-Guetaria section 19

III.3- The Zarauz-Guetaria section 22

111.4. The Orio section 24

111.5. The San Sebastian area 26

111.6. The Pasajes section 28

III.7« Monte Jaizkibel: Leznobar to Cabo. Higuer 29

IV. REGIONAL SYNTHESIS AND DISCUSSION 31

IV.1. Regional synthesis 31

IV.2. Discussion 34

References 37

Figures 1-60

- Ill -

CONTENTS (cont.)

Appendix I - Nannoplankton analyses

la - Distribution chart Zumaya-Guetaria section

lb - Distribution chart Zarauz-Guetaria section

Ic - Distribution chart Orio area

Id - Distribution chart Orio section

le - Distribution chart San Sebastian area

If - Distribution chart Pasajes section

Ig - Distribution chart Fuenterrabia-Cabo Higuer

Enclosures

1 - Zumaya-Guetaria section

2 - Zarauz-Guetaria section

3 - Orio section

4 - Pasajes section

5 - Detail-sections 1- 8

6 - Detail-sections 9-17

7 - Detail-sections 18-23

8 - Bed-thickness-logs 1-18

9 - Regional correlation of sections

iorto*2olfl/6-

STELLINGEN

1. Selley's interpretatie van geulpatronen en uitbouwrichtingen in fossiele "submarine fans", gebaseerd op "dipmeter logs", is aanvechtbaar.

Selley, R.C.,1979. Dipmeter and Log Motifs in North Sea Submarine-Fan Sands. AAPG Bulletin, vol. 63, p. 905-917

2. Rupke's suggesties betreffende de ligging van het Iberisch Schiereiland ten opzichte van de paleoè'quator en de snelheid van aardrotatie gedurende het Carboon getuigen van weinig reali­teitszin.

Rupke, N.A. , 1977. Growth of an ancient deep-sea fan. Journal of Geology, vol. 85, p. 725-744

3. De door Vail et al. ontwikkelde "coastal onlap"-curven geven een misleidend beeld van relatieve zeespiegelbewegingen en hun even­tuele eustatische componenten.

Vail, P.R. et al., 1977. Seismic Stratigraphy and Global Changes of Sea Level, Part 3 : Relative Changes of Sea Level from Coastal Onlap. AAPG Memoir 26, p. 63-81.

4. Het is, in tegenstelling tot de-interpretatie van Vail et al. (op. cit.), meer aannemelijk dat in sedimentaire bekkens relatieve zeespiegeldalingen zich in de regel langzamer voltrokken, als gevolg van eustatische bewegingen, dan relatieve zeespiegel-rijzingen.

5. Het belang van schijnbare eustatische zeespiegelbewegingen ver­oorzaakt door vormveranderingen van de geo'ide (Mörner, 1981) is algemeen onderschat.

Mörner, N.A., 1981. Revolution in Cretaceous sea-level analysis. Geology, vol. 9, p. 344-346 •

6. Directe interpretatie van het energie-niveau van een afzettings­milieu uit seismische facies, zoals voorgesteld door Mitchum et al., is onmogelijk.

Mitchum, R.M. et al., 1977. Seismic Stratigraphy and Global Changes of Sea Level, Part 6: Stratigraphie Interpretation of Seismic Reflection Patterns in Depositional Sequences. AAPG Memoir 26, p. 117-133

7. De "Boulder Beds" in de Wajid Zandsteen (Hadley en Schmidt, 1975) zijn vrijwel zeker een direct product van de Laat-Paleozoïsche glaciatie van het Arabisch Schiereiland.

Hadley, D.G. en Schmidt, D.L.,1975. Non-glacial Origin for Conglomerate Beds in the Wajid Sandstone of Saudi Arabia. In : Gondwana Geology (Editor: K.S.W. Campbell) Australian National University Press.

8. De door Hottinger opgestelde Alveolinen-zonering van het Ilerdien is, voornamelijk als gevolg van een onduidelijk soortbegrip, voor de praktijk niet bruikbaar.

Hottinger, L., 1960. Recherches sur les Alveolines du Paléocène et de 1'Eocène. Memoires Suisses de Paleontologie, vol. 75/76.

9. Bij het onderwijs in de stratigrafie is het gebruik van seismische profielen van wezenlijk belang.

10. De propaganda voor het creationisme van de Evangelische Omroep is, doordat zij zich hoofdzakelijk uit in een ongenuanceerde stellingname tegen het evolutionisme, niet bevorderlijk voor de geestelijke volksgezondheid.

Stellingen behorende bij het proefschrift van A. van Vliet : "Submarine fans and associated deposits in the Lower Tertiary of Guipuzcoa (Northern Spain)"

- IV -

SUMMARY

The Lower Tertiary outcrop along the coast of Guipuzcoa,

northern Spain, consists exclusively of deep-marine sediments,

deposited in a narrow elongated (ESE-WNW) basin. The early

Tertiary sedimentary history of this basin can be described in

terms of three main phases:

- a phase of predominantly (hemi-)pelagic deposition (almost the

entire Paleocene);

- a phase of deposition from axially flowing carbonate-rich

turbidity currents (latest Paleocene to earliest Eocene);

- a phase of lateral input of predominantly terrigenous elastics

via submarine fans (largest part of the early Eocene).

During the latter two phases (hemi-)pelagic sedimentation

became proportionally less important due to increasing rates of

turbidite sedimentation. Late Maastrichtian to early Paleocene

diapirism of Upper Triassic evaporites had created swells and

depressions in the basin floor and controlled the deposition of

turbidites well into the early Eocene. Various facies

associations can be distinguished in the Lower Eocene turbidite

successions. In the 'middle fan association' thick-bedded

proximal turbidites are concentrated in overall non-channelised

packages, tens of metres thick, which internally show

channelling. In the 'outer fan association' thick-bedded proximal

turbidites have planar geometries but are still concentrated in

packages. A vertical section through these packages commonly

displays a crude coarsening - and thickening - upward trend of

beds. In the 'fan fringe association' thick-bedded proximal

turbidites no longer occur concentrated in groups but

disseminated in a matrix of thin-bedded distal turbidites. The

'basin plain association' is characterised by monotonous

successions of thin-bedded turbidites. (Hemi-)Pelagic interbeds

may be present in all of these facies associations. Vertical and

lateral arrangements of different facies associations can be

interpreted to terms of episodes of progradation and abandonment

- V -

of submarine fan systems. Long-distance lateral facies

relationships could only be established with the aid of

biostratigraphic control, for which use was made of calcareous

nannoplankton from the interbedded hemipelagic marls. In the

Lower Eocene the turbidites derived from the northern basin

margin are carbonate-cemented quartz-arenites. Those derived from

the southern basin margin have a lithic-arenitic composition. The

stratigraphie superposition of submarine fans fed from opposite

basin margins directly indicates that the deep-marine basin must

have been rather narrow, probably only a few tens of kilometres

wide.

KEYWORDS

Spain, Pyrenees, Bay of Biscay, Tertiary, Paleocene, Eocene,

deep-marine sedimentation, turbidite, pelagic sediment, submarine

fan, biostratigraphy, nannoplankton.

SAMENVATTING

Langs de kust van de Spaanse provincie Guipuzcoa (hoofdstad: San

Sebastian) is een smalle dagzoom van Onder-Tertiair plaatselijk

goed ontsloten. Dit Onder-Tertiair (Paleoceen en Onder-Eoceen)

bestaat geheel uit sedimenten, afgezet in een verscheidenheid van

diep mariene milieu's in een langgerekt (WNW-OZO) bekken. In de

Vroeg-Tertiaire sedimentaire geschiedenis van dit bekken kunnen

drie hoofdfasen worden onderscheiden:

- een fase van bijna uitsluitend (hemi-)pelagische sedimentatie

(vrijwel het gehele Paleoceen)

- een fase van afzetting uit troebelingsstromen rijk aan

kalkfragmenten. Deze stromen volgden de richting van de bekken-

as (laatste Paleoceen en vroegste Eoceen)

- een fase van laterale aanvoer van overwegend terrigeen

materiaal eveneens door troebelingsstromen (vrijwel het gehele

Vroeg-Eoceen)

Gedurende de twee laatste fasen werd (hemi-)pelagische

sedimentatie verhoudingsgewijs steeds minder belangrijk.

Diapirisme van evaporieten uit de Boven-Trlas (Keuper) had

gedurende het Laat-Maastrichtien en vroegste Paleoceen een

topografie van ruggen en depressies veroorzaakt en beïnvloedde

daarmee de afzetting van turbidieten tot in het vroegste Eoceen.

In de turbidiet-opeenvolgingen van het Onder-Eoceen kunnen

verschillende facies-associaties worden onderscheiden, die in hun

onderlinge samenhang geïnterpreteerd kunnen worden in termen van

een model met submariene sediment-waaiers ("submariene fans") en

een daaraan grenzende bekken-vlakte ("basin plain"). In de

"middle fan"-assoclatie zijn dik-gelaagde proximale turbidieten

geconcentreerd in tientallen meters dikke pakketten met interne

geulvorming. In de "outer fan"-associatie zijn dik-gelaagde

proximale turbidieten eveneens geconcentreerd in pakketten waarin

echter geulvorming ontbreekt en individuele tubidieten een

plaatvormige geometrie bezitten. Een verticale sectie door

dergelijke pakketten vertoont gewoonlijk een globale opwaartse

toename van de maximale korrelgrootte in de turbidieten gepaard

gaande met een toename van de laagdikte. In de "fan fringe"-

associatie komen dik-gelaagde proximale turbidleten niet langer

geconcentreerd in pakketten voor maar zijn zij verstrooid in een

grondmassa van dun-gelaagde distale turbidleten. De "basin

plaln"-associatie bestaat uit monotone opeenvolgingen van dun-

gelaagde distale turbidleten. (Hemi-)Pelagische inschakelingen

kunnen in ieder van deze facies-associaties aanwezig zijn. De

ruimtelijke rangschikking van de verschillende facies-associaties

kan geïnterpreteerd worden in termen van episoden van groei en

afsterven van "submarine fan"-systemen. Grootschalige laterale

facies-relaties kunnen slechts met behulp van blostratigrafische

correlaties worden vastgesteld. Hiervoor is gebruik gemaakt van

nannoplankton uit hemipelagische inschakelingen. In het Onder-

Eoceen zijn de turbidleten die werden aangevoerd via de

noordelijke bekkenrand kalkhoudende kwartsarenieten.

De turbidleten aangevoerd via zuidelijke bekkenrand zijn van een

lithisch arenletische samenstelling. De stratigrafische

superpositie van "submarine fan" afzettingen aangevoerd via

tegenover elkaar liggende bekkenranden vormt een directe

aanwijzing dat het bekken smal, hoogstens enkele tientallen

kilometers breed, geweest moeten zijn.

- 1 -

SUBMARINE PANS AND ASSOCIATED DEPOSITS IN THE LOWER TERTIARY

OP GUIPUZCOA (NORTHERN SPAIN)

I. INTRODUCTION

1.1. Scope of the study

The sediraentology and stratigraphy of the Lower Eocene

turbidite successions, outcropping along the coast of the Basque

province of Guipuzcoa (capital San Sebastian, N. Spain, Pig. 1),

form the subject of this report ;. Facies analysis and

interpretation in terms of depositional processes and

environments are the principal elements in this study, but

biostratigraphic investigations proved to be indispensable for a

better understanding of lateral facies relationships. These

studies led to a regional synthesis of the early Tertiary

sedimentary history of the Guipuzcoan basin, as far as this can

be established from the available outcrop pattern.

Research by the Koninklijke/Shell Exploratie en Produktie

Laboratorium (KSEPL) in the area was initiated in 1972 by

Dr. C. Kruit and was stimulated by the growing interest in deep-

marine sands as potential hydrocarbon reservoirs. Since 1974 the

author has been entrusted with the continuation and completion of

these studies. The fieldwork for this report was carried out

during a period of five months spread over the years 1974 and

1975.

1.2. Stratigraphie setting

Lower Tertiary deposits form the uppermost part of the

preserved stratigraphie succession in Guipuzcoa and conformably

overly Upper Cretaceous strata (Pig. 1).

*) Locations cited throughout this report are indicated in Pig. 2.

- 2 -

Several major trends can be observed in the succession that

overlies the Hercynian basement of the Western Pyrenees (cf.

Lamare 1952, Rat 1959, Jerez Mir et al. 1971):

The Stephanlan, Permian and Lower Triassic are represented by

terrestrial deposits, which, with the exception of the

Stephanian, are mainly in a 'red bed facies'.

The Muschelkalk (Middle Triassic) is represented by carbonates

deposited in restricted shallow-marine environments. According to

Lamare (1952) these carbonates rarely occur in their normal

stratigraphie position. They are usually broken up and surrounded

by the evaporltic gypsiferous marls of the Keuper (Upper

Triassic). The Jurassic and Lower Cretaceous deposits are complex

but may in essence be regarded as shallow-marine deposits (mainly

carbonates). Prom the late Albian to, at least, the late early

Eocene, sedimentation continued in deep-marine environments. This

resulted in thick successions of turbidites, marls, pelagic

carbonates and, locally, debris flow and slump deposits. In

Western Guipuzcoa the Upper Cretaceous contains interbedded

pillow lavas and volcanic breccias.

1.3« Structural setting

The simplified post-Hercynian succession, as outlined above,

is in practice never encountered without complications, caused by

structural deformation (see e.g. cross-sections by Jerez Mir et

al. 1971).

The Keuper evaporites played an important role in

controlling the pattern of structural evolution in two ways.

Firstly, because during the late Maastrlchtian and earliest

Paleocene they gave rise to diapiric structures (Lotze 1953,

Hanisch 1974, Hanisch and Pflug 1974). Secondly, because they

acted as a décollement horizon for the nappe structures formed

during the compressional Pyrenean deformation phase, which

affected Guipuzcoa in the Oligocène (Boillot et al. 1972). The

Lower Tertiary coastal belt of Guipuzcoa is a simple seaward

- 3 -

dipping monocline, only interrupted by disturbances near Zarauz

and, to a much lesser extent, San Sebastian (Pig. 3)- The

disturbance of Zarauz is attributed to late Maastrichtian-

earliest Paleocene diapirism (Hanisch 1974). The less pronounced

disturbance of San Sebastian probably has a similar origin. At

topographically higher levels in the west (around Garate) strata

are overturned and dip southward (Pig. 3). This overturning was

most likely created by the drag of a northward moving nappe (cf.

Hanisch 1974) of which the remnants can be observed in the south

(Pig. 1).

The faults shown in Pig. 3 are inferred from abrupt changes

in dip and/or strike of the beds.

1.4. Previous investigations

Exposure quality and accessibility have made the Lower

Tertiary of Guipuzcoa a subject of considerable interest during

the last three decades. Pioneering sedimentological work, mainly

of a descriptive nature, was done by Gomez de Llarena (1954 and

1956).

Studies of palichnological tenor were presented by Seilacher

(1967), Hanisch (1972) and Crimes (1973). The biostratigraphy of

the Zumaya-Guetaria section was described in papers by

Von Hillebrandt (1965) on foraminifera and by Kapellos (1974) on

calcareous nannoplankton. The diapir of Zarauz and its presumed

effects on late Cretaceous and early Tertiary sedimentation were

discussed by Hanisch (1974 and 1978) and Hanisch and Pflug

(1974). Crimes (1976) gave a (very) generalised account of the

sedimentology of the entire (Upper Albian-Lower Eocene)

Guipuzcoan flysch succession. Submarine fan deposits were first

recognised in the Lower Tertiary by Kruit et al. (1972).

Kruit et al. (1975) published an extensive field-guide on these

fan deposits for an excursion on the occasion of the IXth

International Congress of Sedimentology at Nice. Much of the

information contributed by the present author to this field-guide

- 4 -

was re-used in a more recent paper (Van Vliet, 1978), which can

be regarded as à condensed version of the present report.

1.5- The need for blostratigraphic control

The deposition of a turbidite is from a geological point of

view an instantaneous event which affects a vast area. Every

individual turbidite layer therefore represents an ideal time-

stratigraphie marker. Unfortunately, the value of such markers

for correlation purposes is often downgraded by their abundance,

i.e. by the monotonous repetitive character of turbidite

deposition. In turbidite basins events of exceptional magnitude

can produce basinwide turbidites which are sufficiently

'characteristic' to be used as a means of time-stratigraphic

correlation (e.g. Ricci Lucchi 1975a, Rupke 1976). Such anomalous

beds have not been recognised in the Guipuzcoa area.

Llthostratigraphic correlation within the Lower Tertiary of

Guipuzcoa is further hampered by the fact that exposures are

almost entirely restricted to the coastline. Only river-mouths

and re-entrants of the coastline create an opportunity to examine

sections of sufficient (i.e. hundreds of metres) stratigraphie

thickness. Without time-stratigraphic control the facies

relationships between those widely spaced observation points are

difficult to understand.

Two separate blostratigraphic investigations were made: one

using planktonic foraminifera and a second using calcareous

nannoplankton. The analyses were focussed on the Lower Eocene,

which, having the largest facies variation, is the most

problematic interval. The foraminiferal biostratigraphy was

established by J. Brouwer and summarised by Kruit et al. (1975).

The nannoplankton studies were carried out by the present author.

1.6. Nannoplankton biostratigraphy

Since 1954, when Bramlette and Riedel demonstrated the

stratigraphie significance of calcareous nannofossils, a rapidly

- 5 -

increasing number of publications on this subject has appeared.

Martini (1971) presented a standard nannoplankton zonation for

the Cenozoic. This standard zonation is a compilation of a series

of previous investigations by various authors and subdivides the

Cenozoic into 46 zones. The zones are numbered NP 1 to NP 25 for

the Palaeogene and NN 1 to NN 21 for the Neogene and Quaternary.

In the present study this standard nannoplankton zonation has

been applied. The zone definitions (see Martini 1971) imply that

only a limited number of species have to be considered.

Nevertheless, in this study more species were taken into account

to increase the reliability of the results.

The samples analysed cover the zones NP 7/8 to NP 14. The

stratigraphie distribution of the following selected species and

subspecies formed the basis of the zonal determination:

Fasclcullthus tympaniformis HAY & MOHLER

Fasclcullthus involutus BRAMLETTE & SULLIVAN

Discoaster mohleri BÜKRY & PERCIVAL

Sphenolithus anarrhopus BUKRY & BRAMLETTE

Discoaster multiradiatus BRAMLETTE & RIEDEL

Fasclcullthus schaubli HAY & MOHLER

Trlbrachiatus bramlettel (BRONNIMAN & STRADNER)

Tribrachiatus contortus (STRADNER)

Dlscoaster dlatypus BRAMLETTE & SÜLLIVAN

Discoaster binodosus MARTINI

Tribrachiatus orthostylus SHAMRAI

Sphenolithus radians DEFLANDRE

Discoastero'ides kuepperi (STRADNER)

Cyclococcolithlna gammation (BRAMLETTE & SULLIVAN)

Discoaster distinctus MARTINI

Discoaster lodoensis BRAMLETTE & RIEDEL

Lophodollthus renlformls BRAMLETTE & SULLIVAN

Hellcosphaera seminulum semlnulum BRAMLETTE & SULLIVAN

Helicosphaera seminulum lophota BRAMLETTE & SULLIVAN

Retlculofenestra sp.

Discoaster sublodoensis BRAMLETTE & SULLIVAN

- 6 -

The stratigraphie distribution of these taxomic units as

observed in the uppermost Paleocene and Lower Eocene of Guipuzcoa

is indicated in Pig. 4.

The correlation between the Lower Eocene standard

nannoplankton zonation and the, slightly modified, foraminiferal

plankton zonation of Postuma (197D as applied by Kruit et al.

(1975) is given in Pig. 5.

The results of the nannoplankton analyses are presented in

Appendix I. The consistency of these results with an established

standard nannoplankton zonation, the planktonic origin of the

nannofossils and the relatively small size of the study area, are

factors which all together, justify the use of the biozones as a

means of time-stratigraphic correlation.

Owing to their small size, calcareous nannofossils can

easily become re-suspended after erosion under a wide range of

energy conditions. This property of nannoplankton creates the

possibility of encountering reworked specimens in mud-grade

sediments. In fact, such reworking is so common that virtually

every paper on nannoplankton biostratigraphy at least mentions

it.

In practically all of our samples substantial amounts of

Upper Cretaceous species (among which the genera

Arkhangelsklella, Prediscosphaera, Watznaueria, Micula) were

found. It suggests the 'nearby' existence of submarine and/or

subaerial outcrops of (deeper) marine Upper Cretaceous strata

during the early Tertiary. Intra-Tertiary reworking was also

deduced (see Appendix I) but is less important.

Where possible the nannoplankton samples were taken from

hemipelagic muds which, even in the field, can be distinguished

from turbidite muds on the basis of their sequential position and

their lighter colour.

The experience that reworking did not cause a serious

zonation problem in this study can be explained by the fact that

hemipelagic intervals are well developed in large parts of

- 7 -

the Lower Tertiary succession in Guipuzcoa. Consequently,

possible reworked forms would be severely 'diluted' anyhow.

II. SUBMARINE PANS: PHYSIOGRAPHY, DEPOSITIONAL PROCESSES AND

FACIES

II.1. Introductory remarks

It has become general practice in facies sedimentology to

start with a description of the observed facies and to conclude

with an interpretation of those facies in terms of depositional

processes. Such a description/interpretation procedure may be

repeated on the level of facies associations and depositional

environments. In some cases the procedure may even be applied to

an entire basin-fill.

The strict procedure outlined above has not been followed in

this report, because the 'small-scale' aspects of turbidite

facies are so well known as to render a formal facies description

and process interpretation on the scale of individual beds

redundant. In this report description and interpretation

generally start on the level of facies associations and

depositional environments. Only where considered necessary do the

description and interpretation involve more detail.

II.2. The emergence of fan models in turbidite sedimentology

Up to the late sixties the main interest in many papers

concerning ancient turbidite facies was directed towards

relatively small-scale aspects, viz: depositional processes of

individual units, origin of sedimentary structures, faunal

content and its bathymétrie significance, etc. The depositional

setting of turbidltes was usually discussed in broad terms using

fairly simple proximal/distal concepts (see Bouma 1962).

Occasionally (e.g. Walker 1966) certain turbidite facies were

related to more specific depositional environments.

- 8 -

A break-through in turbidite sedimentology was the

presentation of the first submarine fan facies models (Mutti and

Ghibaudo 1972, Mutti and Ricci Lucchi 1972). Previously, Jacka

et al. (1968) had developed a submarine fan model from the

Permian of the Delaware Basin (West-Texas). This latter model,

however, seemed to concern a fan built primarily by density

currents (see also Harms 1974) rather than sediment gravity

flows.

The emergence of submarine fan models in studies of ancient

turbidite facies was stimulated by data that became available on

the physiography and surface sedimentology of (sub-)recent fans,

in particular those on the Pacific margin of the united States

(e.g. Shepard et al. 1969, Carlson and Nelson 1969, Nelson et al.

1970, Normark 1970, Haner 1971, Normark and Piper 1972).

Nowadays recognition of submarine fan environments in

ancient turbidite successions is becoming more and more common.

As a result of the large number of ancient fan studies, a state

of considerable confusion has been created (Nilsen 1980, Walker

198O). One point of confusion, mainly pertaining to nomenclature,

arises from the physiographic interpretation of ancient facies. A

fundamental problem in this respect is that in fans with a known

physiography (i.e. 'modern' fans) only the surface sediment

distribution is observed (i.e. the uppermost metres). An

additional problem is that turbidite deposition on many 'modern'

fans ceased or was dramatically reduced due to the rapid Holocene

sea-level rise. Deposition on these fans is at present limited to

blankets of hemipelagic mud (Nelson 1976, Normark 1978). Por

these reasons physiography and facies of submarine fans have been

treated separately as set out below.

II.3. Pan physiography

Ideally, submarine fans are cone-shaped sediment bodies at

the base of a submarine slope. The development of such a perfect

fan involves the following requirements:

- 9 -

- a discrete point-source of sediment

- a flat basin floor

- absence of any morphological confinement

In reality, these requirements are difficult to meet. In

elongated orogenic basins and rift basins they are probably never

met. Therefore, a very precise definition of 'submarine fan' is

of little practical use.

In the present report a submarine fan is defined as an

organised (as opposed to 'chaotic') base-of-slope sediment body

with a positive depositional relief, which eventually may merge

into a basin plain. Contourite mounds are excluded from this

definition.

Studies of 'modern' fans (compiled in Normark 1978) have

revealed that the physiography of many of these fans is basically

similar in that they show three distinct morphologic divisions:

upper, middle and lower fan.

The upper fan is characterised by large relatively straight

channels ('fan valleys'), hundreds of metres to tens of

kilometres wide and tens to a few hundreds of metres deep. Levees

are well developed and the channel floors are usually elevated

above the adjacent fan surface. The position of the upstream part

of the channels is fixed by the feeder canyon. The downstream

course, on the transition to the middle fan, may switch

episodically as shown for the Navy Pan by Normark et al. (1979).

One or more channels may be active at one time, depending on the

number of canyons that feed the system.

The middle fan is the area where turbidity currents leaving

the confinement of an upper fan channel start to dump the bulk of

their sediment load. On a longitudinal fan profile the middle fan

shows up as a convex-upward 'bulge' termed the 'suprafan'

(Normark 1970). Each major, active channel develops its own

suprafan. A suprafan has a rough topography caused by the

presence of numerous small-scale channels and other erosional

depressions. Detailed suprafan physiography has extensively been

- 10 -

discussed by Normark (1978) and Normark et al. (1979). The

surface roughness of the suprafan vanishes In dovmfan direction.

The lower fan is a gently sloping area of smooth topography

that may merge into a basin plain. The extent to which a lower

fan division can be distinguished depends on whether or not

ponding of turbidity currents occurs in the basin. As a result of

ponding, basin plain physiography will expand over adjacent fan

physiography.

The physiographic model as outlined above is applicable to

fans containing appreciable amounts of coarse sediment (Normark

1974 and 1978). Relatively fine-grained fans, such as the huge

Bengal Pan, do not show suprafan development; their channels

persist almost across the entire fan surface and die out

gradually (Normark op. cit.).

II.4. Pan facies models

Some of the physiographic elements previously discussed, in

particular channels, are directly expressed in facies geometry,

which can be seen if exposure conditions are ideal. Por fan areas

of smooth topography the relationship between physiography and

facies is exceedingly, difficult, if not impossible, to trace,

even in ideal exposures. This difficulty is caused by the very

small gradients (less than one degree; see Nelson and Kulm 1973,

Normark 1978 Pig. 11) that characterise middle and lower fans and

that are inherent in deposition from turbidity currents. In terms

of stratigraphie geometry in outcrop, large parts of submarine

fans and basin plains are therefore expressed merely in parallel

bedding.

All submarine fan facies models (see 'review' by Walker

I98O) recognise: a large-scale channelised feeder system, a

transitional distributary system and a non-channelised

depositional lobe system. In the models of Walker and Mutti

(1973) and Walker (1978) the distributary system and the lobe

system are taken together as 'suprafan lobes' and termed 'middle

fan' deposits. Thus in these models it is assumed that smooth

- 11 -

suprafan physiography can be directly related to non-channelised

lobe facies. For reasons discussed earlier in this section and in

section II.2, this is a rather speculative assumption. The

original Italian models (Mutti and Ghibaudo 1972, Mutti and

Ricci Lucchi 1972, Ricci Lucchl and Parea 1973, Ricci Lucchi

1975a and b) are basically similar to Walker's models but use a

different terminology. Although at least Ricci Lucchi and Parea

(1973) and Ricci Lucchi (1975) mention Normark's (1970) suprafan,

these models do not rigidly relate lobe facies to suprafan

physiography and use the term »outer fan' for lobe facies lacking

channels. Because of the simple and practical criterion involved

(channels or no channels) Italian terminology is preferred by the

present author and used in the model applied for the Lower

Tertiary of Guipuzcoa (Pigs. 6 and 7, Section II.6). In a later

Italian model (Mutti and Ricci Lucchi 1974 and 1975, Mutti 1977

and 1979) a fundamental change appeared: The outer fan lobes were

separated from the distributary system by a zone of by-passing,

containing only minor sandy channel-mouthbars enveloped in

mudstone. The field of applicability of this model is still open

to discussion (see Walker 1980). In the present study a

depositional system with distributaries terminating _on_ the apices

of the lobes is supported (Pigs. 6 and 7).

Mutti (1979) introduced an 'efficiency'-concept in submarine

fan facies models. 'Highly efficient' fans are those in which the

main part of the sediment input is funnelled through the channels

and ultimately deposited in non-channelised lobes. 'Poorly

efficient' fans are those in which the sediment is largely

trapped in channels, resulting in a rudimentary development of

non-channelised lobe facies. Highly and poorly efficient fans are

not fundamentally different but rather represent 'end-members' of

a full spectrum in which probably grain-size characteristics of

the input and flow magnitude play a major role. Obviously, the

model of Pigs. 6 and 7 pertains to a 'highly efficient' fan.

Submarine fan facies models had an important impact on

classical proximality concepts as formulated by Bouma (1962) and

Walker (1967) • It appeared that a general proximal/distal trend

- 12 -

(in facies terms) not only occurs in a basinward direction, but

that similar trends can also be observed from channel to overbank

facies and from lobe to interlobe facies. Walker's (1967) ABC-

index has therefore become a tool of mainly descriptive value.

Yet the expressions 'proximal turbidite' and 'distal

turbidite' continue to be used in literature, albeit in a process

oriented rather than in an environment-oriented sense. Following

Middleton and Hampton (1973), in the present report distal

turbidites are termed those that were entirely deposited under

lower flow regime conditions. Proximal turbidites are termed

those that were, at least partly, deposited under upper flow

regime conditions. Moreover, in this report the term 'turbidite'

does not only apply to classical turbidites that can be described

using Bouma's facies model, but also to sandstone beds displaying

the characteristics of 'fluidised sediment flow' and 'grain flow'

as defined by Middleton and Hampton (1973). The latter group of

beds probably represents the products of high-density turbidity

currents that underwent late-stage flow modification (see

Middleton and Hampton op. cit., Walker 1978). In the low-gradient

(i.e. much less than the angle of repose of mud-free sand) fan

environments, 'true' grain flow can be ruled out as a long

distance sand transport mechanism (cf. Lowe 1976, p. 193)•

Fluidised sediment flow is likewise a depositional process rather

than a sediment transport process.

II.5» Different levels of sequential organisation

In a turbidite succession different levels of sequential

organisation can generally be recognised. In this report the

terms 'megasequence', 'cycle' and 'megacycle' are used.

'Megasequence' refers to a concentration of similar beds or

a concentration of beds displaying a certain trend (thickening-

upward, thinning-upward, symmetrical, etc.).

The term 'cycle' applies to a recurrent pattern in which

monotonous successions and megasequences are involved, for

instance: a basin plain-fan fringe-outer fan-basin plain cycle. A

- 13 -

cycle thus reflects a major episode of progradation and

abandonment of a fan system.

A 'megacycle' Is composed of one or more cycles and forms

the stratigraphie expression of the history of an entire fan

system. A megacycle is distinguished on the basis of its

pétrographie composition and palaeocurrent system.

II.6. Submarine fans and associated deposits in the Lower

Tertiary of Guipuzcoa (Pigs. 6, 7 and 8)

The facies associations observed in the Lower Tertiary of

Guipuzcoa range from middle fan to basin plain. In the models of

Pigs. 6 and 7 the inner fan is included to complete these models.

So far, however, no deposits interprétable as inner fan have been

encountered.

Middle fan facies association.

Middle fan deposits are recognised as concentrations of

proximal turbidite sandstones in overall non-channelised bodies

that internally show channeling. These bodies are thought to be

the apical portions of outer fan depositional lobes and have

widths of the order of few kilometres. In vertical section they

show a well-defined base and a crude coarsening- and thickening-

upward megasequence. The well-defined base is merely an abrupt

increase in bed thickness. Megasequence thickness ranges from 20

to 70 metres. Individual beds may attain thicknesses up to 15

metres. The sandstones are usually structureless or show

consolidation lamination (Lowe 1975) with broadly spaced pillars

and/or ordinary dish structures. The tops of the beds, if not

truncated, are crudely horizontally laminated. Grading, if

present, is of the coarse-tail type. The beds are interpreted as

being emplaced by high-density turbidity currents that passed

through a final stage of fluidised sediment flow. The internal

channelling mentioned before can be divided into three types:

- 14 -

1. scour-and-fills at the bases of individual sandstone beds

(scouring depths of the order of metres);

2 'true' channels (metres deep and tens of metres wide) with

lateral accretion units and shaly post-abandonment fills (clay

plugs);

3. gently concave scours (decimetres to ? metres deep, tens to ?

hundreds of metres wide) filled with thin-bedded turbidites,

often resembling 'Facies E' of Mutti and Ricci Lucchi (1972).

Lobe-apex deposits as described above are clearly compatible

with the suprafan physiography discussed in detail by Normark

et al. (1979)» In vertical section thick-bedded lobe-apex

deposits alternate with a thinner bedded (up to 1.5 m) facies. A

rather characteristic feature of that facies is the common

occurrence of erosionally based megaripple formsets and cross-

bedded scour-and-fills in the tops of many beds. Apparently, the

flanks of a lobe-apex are areas of erosion and subsequent

tractional reworking (? by suction currents) during the waning

phases of high-density turbidity currents.

Outer fan facies association.

In outer fan deposits proximal turbidite sandstones are

concentrated in non-channelised bodies. In vertical section these

bodies display a crude coarsening- and thickening- upward

megasequence. Outer fan deposits are distinguished from middle

fan deposits by the absence of internal channelling.

Outer fan deposits were first defined as such by Mutti and

Ghibaudo (1972) and Mutti and Ricci Lucchi (1972). The coarsening-

and thickening-upward megasequence is attributed to basinward

progradation of a depositional lobe.

In the Lower Eocene of Guipuzcoa lobe thicknesses range from

10 to 50 metres. Individual beds may attain thicknesses of up to

10 metres. Amalgamation along more or less planar surfaces is

common in the topmost parts of the lobe megasequences. Most

individual beds show similar characteristics to those in the

middle fan, although entirely horizontally laminated beds are

- 15 -

more common. In the distal parts of a lobe the megasequence has a

gradational character and contains a substantial, upward

declining, number of intercalated thin-bedded distal turbidites.

In their proximal parts the lobes abruptly overly interlobe

deposits. Vertical stacking of lobes is frequently observed and

probably results from an autocyclic process involving lobe build­

up, avulsion of the feeding distributary and formation of a new

lobe in an adjacent interlobe depression. The marked asymmetry

implies 'sudden' lobe abandonment.

Proximal interlobe deposits are thinner bedded (up to

1.5 metres) and do not show an obvious megasequential

organisation.

Pan fringe facies association.

In fan fringe deposits thick-bedded proximal turbidites are

no longer concentrated in distinct groups. In the fan fringe lobe

megasequences are 'diluted' in a matrix of thin-bedded distal

turbidites. This arrangement may lead to successions with a

bimodal bed-thickness distribution; i.e. successions of isolated

proximal turbidites (up to 2 metres) separated by groups of thin-

bedded (centimetre-scale) distal turbidites, while beds of

intermediate characteristics are lacking. The bimodality suggests

different origins for proximal and distal beds. A succession as

described is assumed to develop in situations where a nearby fan

lobe supplies the proximal beds, whereas the other beds are

derived from more distant lobes of the same fan or from other fan

systems. In this interpretation the succession has an indirect

physiographic significance in that the fan fringe lobe relief is

reduced to such an extent that it no longer forms an obstruction

to turbidity currents from elsewhere. In outer fan megasequences,

interbedded distal turbidites become less common upward, thereby

reflecting the build-up of lobe relief. In fan fringe successions

such interbedding remains consistently present (Pigs. 7 and 8).In

the upper part of the 'megacycle 1' system (see Chapter III)

proximal turbidites in the fan fringe still mostly have well

developed structureless or dish-structured divisions.

- 16 -

A highly characteristic feature of 'megacycle 1' distal

outer fan and fringe deposits Is the abundance of

intraformational clasts. The clasts are normally concentrated on

top of the structureless divisions of the proximal turbidites.

They consist of angular pieces of marl, siltstone, laminated fine

sandstone or even (if sufficiently large) whole sequences of

thin-bedded turbidites. Proximal turbidites with similar

concentrations of clasts were described by Ricci Lucchi (1965)

and Marschalko (1970). Ricci Lucchi (op. cit.) suggested they

result from processes 'intemediate between turbidity currents and

slidings'. Marschalko (op. cit.) thought the clasts to have been

ripped up from a soft substratum by high-density turbidity

currents. The latter interpretation directly explains the

abundance of clasts in distal outer fan and fringe deposits,

especially when the characteristic interbedding of thin-bedded

distal turbidites is considered. Occasionally, the soles of the

proximal turbidites do show flat-bottomed but steep-walled

depressions (see Kruit et al. 1975, p. 68) indicating that slabs

were lifted out from the substratum. The position of the clasts

on top of the structureless divisions implies that they worked

themselves up to a density discontinuity in the flow. The

irregular relief of the clast concentrations is filled in and

overlain by the laminated divisions of the proximal turbidites.

The significance of these 'clast-layers' in fan fringe turbidites

was previously discussed in Van Vliet (1978). Observations by

Ricci Lucchi and Valmori (1980) in the Marnoso Arenacea (Miocene,

Northern Apennines) support the explanation given above. In fan

fringe successions in which the proximal turbidites lack

structureless divisions (lower part 'megacycle 1' and

'megacycle 2') such concentrations of intraformational clasts are

less well developed or completely absent.

Basin plain facies association.

In this study 'basin plain deposits' have been termed

monotonous successions of centimetre- to decimetre-scale bedded

turbidites that do not show any sequential organisation. All

- 17 -

layers show base absent Bouma-sequences. Ricci Lucchi (1979),

Mutti and Johns (1978) and Ricci Lucchi and Valmori (1980)

suggest that basin plain turbidites do not necessarily represent

basinward extensions of fan lobe turbidites. Their studies

indicate that at least a part of the basin plain turbidites they

analysed were deposited from relatively large flows that by­

passed fan systems. In the Lower Tertiary outcrop of Guipuzcoa

the role of such by-passing cannot be established from the

geometry of individual layers under the present exposure

conditions. Nevertheless, evidence of by-passing was occasionally

found in the form of tractional lags intercalated in outer fan

deposits (examples will be discussed in the next chapter).

(Hemi-)Pelaglc sediments.

No quantitative study was undertaken concerning the amount

of (hemi-)pelagic interbedding. Qualitatively, the abundance and

thickness of such interbedding was found to be undiagnostic for

the position of facies in a fan/basin plain system.

In this report the adjective 'pelagic' has been used for

more or less pure, tightly cemented, lime-mudstones, whereas

'hemipelagic' pertains to impure (terrigenous admixture) non-

cemented marls.

Throughout the Lower Tertiary succession a trend of

proportionally decreasing (hemi-)pelagic interbedding is obvious.

The Lower Paleocene is almost exclusively pelagic. In the

lowermost Eocene (NP 10-11) interbeds of pelagic lime-mudstone

are still common, even in middle fan deposits. In parts of NP 13

and NP 14 hemipelagic marls are only poorly developed, even in

basin plain deposits. Dissolution effects can be ruled out on the

basis of the good preservation state of the nannofloras. The

overall trend of decreasing (hemi-)pelagic interbedding probably

merely reflects increasing rates of clastic sedimentation.

Additional remarks

It should be stressed that the various turbidite facies

associations can only be determined and interpreted from large

- 18 -

exposures. Moreover, the use of bed-thickness trends also has

limitations. A fundamental factor that obliterates the generation

of 'ideal' megasequences is the variability of the bulk sediment

input per event to any given depositional environment. Only when

this variability is limited can a 'reasonable' thickening-upward

megasequence be expected to develop from lobe progradation.

Therefore, in megasequence interpretation extreme detail is

unwarranted (compare Ricci Lucchi 1975b).

External controls sometimes strongly influence bed-thickness

and grainsize trends in turbidite successions, but then on a

basinwide scale. This is well illustrated in fans associated with

fault scarps as described by Surlyk (1978). The megasequences in

such fans seem to be governed by episodic faulting and subsequent

breakdown of fault scarps and not by autocyclic sedimentary

mechanisms.

III. AREAL SEDIMENTOLOGICAL DESCRIPTION AND INTERPRETATION

III.l. Introduction

This chapter gives an account of the sedimentology and

stratigraphy of the sections and the most relevant 'isolated'

exposures in the area. The description is in geographical order

from west to east and is supported by illustrations of the

following categories: a) general sections, b) detail-sections,

c) bed-thickness-logs and d) field photographs.

a) General sections (enclosures 1-4) give a synopsis of the

sedimentology and stratigraphy of large intervals. Their

locations are indicated in Pig 9, in which:

I is Zumaya-Guetaria section

II is Zarauz-Guetaria section

III is Orio section

IV is Pasajes section

- 19 -

b) Detail-sections (enclosures 5-7) highlight the smaller scale

aspects of facies. Their locations are indicated in Pig. 9 and

their stratigraphie positions are, where applicable, shown on

the general sections. The key to the detail-sections is given

in Pig. 10.

c) Bed-thickness-logs ; (enclosure 8) provide the possibility to

see vertical bed-thickness trends. In this context 'bed-

thickness' stands for 'thickness of the sand-grade part of a

turbidite layer'. Where applicable the stratigraphie position

is indicated on the general sections.

d) Pleld photographs are incorporated in the figures (numbers

11-58).

III.2. The Zumaya-Guetarla section (enclosure 1)

The Zumaya-Guetaria section measures approximately

2400 metres and is almost continuously exposed along the

San Telmo beach at Zumaya and the coastal road from Zumaya to

Guetaria. The section provides the most complete stratigraphie

record of the Early Tertiary in the area and therefore serves as

a reference section. The succession starts with 80 metres of

parallel-bedded (decimetre-scale) rose coloured lime-mudstones.

Interbedding of red-brown marls increases slightly upward.

Bioturbation is intense (Pig. 11). Prom 80 to 260 metres the

succession continues in a basically similar facies (Pig. 12) but

shows the following differences:

- Lime-mudstones and marls have a light grey colour;

- Marl beds are thicker (decimetre-scale) and locally dominate;

- Thin- to very thin-bedded turbidites occur (see detail-

section 1).

*) N.B. The numbering of the bed-thickness-logs does not correspond to the numbering of detail sections.

- 20 -

In thin-section the lime-mudstones appear to contain

disseminated non-fragmented tests of planktonic foraminifera

(Van Vliet 1978, Pig. 14-10A). Scanning Electron Microscope

analyses indicated the lime-mud to consist largely of

recrystallised nannofossils. Apparently, these limestones

represent lithified pelagic oozes. The turbidites are made up of

skeletal carbonate debris mostly of a shallow-marine origin.

Occasionally, the sand-grade parts of the turbidites are entirely

composed of planktonic foraminifera, suggesting that they are

resedlmented oozes. The part of the section described so far is

interpreted as a, predominantly pelagic, basin floor deposit,

formed during a period of virtual absence of clastic input into a

basin. The entirely pelagic character of the lowermost 80 metres

could be explained by assuming that the succession was deposited

on a swell, a slightly elevated area above the reach of turbidity

currents. This assumption needs support of regional evidence and

is discussed in the next chapter. Crimes (1973 and 1976) does not

mention the pelagic character of the lime-mudstones and

interprets them, based on the abundance of Zoophycos, as

•shallower though below wave-base'. Reineck (1973), however,

reports Zoophycos from abyssal depths in the Indian Ocean and

notes that it is there exclusively and abundantly present in the

pelagic carbonate oozes. The gradual disappearence of Zoophycos

over the Paleocene-lowermost Eocene in the San Telmo beach

section is probably related to the disappearence of clean lime-

mudstones rather than to a basin deepening as suggested by Crimes

(1973 and 1976).

The pelagic succession is overlain by a first megacycle of

turbidites of quartz-arenitic composition with a bioclastic

admixture (260 to 950 metres). These turbidites are invariably

carbonate-cemented. Up to circa 500 metres thin lnterbeds of

lime-mudstone are still present. The megacycle is symmetrical and

both starts and terminates in a basin plain facies association.

The lower basin plain interval (260-360 m) is illustrated in

Pigs. 13 and Ik, detail-section 2 and bed-thickness-log 1. The

main part of megacycle 1 is made up of fan fringe deposits

- 21 -

(Pigs. 15-18, detail-sections 3 and 4). Bed-thickness-logs 2 and

3 clearly show the 'isolated' settings of the (relatively) thick-

bedded proximal turbidites. Only at Punta Mariantón (not

accessible) are the otherwise dispersed proximal turbidites

concentrated into an outer fan lobe megasequence.

Just beyond Punta Arranaiz a second megacycle (950-2000 m)

commences. The turbidites of this megacycle are carbonate-

cemented lithic arenites with a bioclastic admixture. The lithic

fragments predominantly consist of chert, siltstone and phyllite

(see Van Vliet 1978, Pig. 14-10D). A single 'lost' quartz-arenite

was observed at Punta Izustarri. Megacycle 2 is asymmetric and

comprises a thick progradational part (basin plain to middle fan

over 650 metres), a stationary middle fan interval (200 metres

thick) and a recessional part (middle fan to basin plain over

200 metres). An isolated slump (Pig. 19) was found in the

lowermost part of the megacycle. The progradational part is

illustrated by Pigs. 20 to 22 and bed-thlckness-logs 4 to 7-

Figures 23 to 29 and detail-sections 6 and 7 focus on the

spectacular middle fan deposits of Bizcarrapia and Irategui. A

notable feature of megacycle 2 compared to megacycle 1 is its

restricted grainsize range (no extraformational fragments coarser

than medium sand) and the sporadic occurrence of structureless

and dish-structured divisions in the turbidites.

The uppermost 400 metres of the Zumaya-Guetarla section

(2000-2400 m) are formed by the quartz-arenitic sandstones of

megacycle 3. Prom 2000 to 2230 metres the succession is

predominantly thin-bedded (bed-thickness-log 8) and lacks any

obvious megasequences. These basin plain/fan fringe deposits are

abruptly overlain, with a planar contact, by a thick-bedded

succession (lowermost 50 m shown in detail-section 8 and bed-

thickness-log 9). Poor exposure conditions and problems of

accessibility preclude a further detailed analysis of the

section. Based on the apparent absence of large-scale

channelling, the whole sandstone complex is tentatively

interpreted as middle to outer fan.

- 22 -

In summary, the Zumaya-Guetaria section consists of a

sequence of predominantly pelagic basin plain deposits (Paleocene

and lowermost Eocene) succeeded by three megacycles of clastic

basin plain and fan deposits (Lower Eocene). Megacycles 1 and 3

are quartz-arenitic; megacycle 2 is composed of lithic arenites.

Palaeocurrent measurements from the section provide

interesting additional information. Regional observations

(Kruit et al. 1975) demonstrate that megacycle 1 represents a

fan, fed from the northern basin margin, whose palaeocurrents

gradually swung around to parallel the basin axis until they

point to west-northwest (N295E). Palaeocurrents that are

southward directed are, in fact, only seen in the lower part of

megacycle 1.

Megacycle 2 represents a fan that was fed from the southern

basin margin. The basin plain deposits from its lower part were

deposited by axially (N295E) flowing turbidity currents. Pan

fringe and outer fan palaeocurrents change to a north-northwest

(N330E mean) orientation. In the upper part of megacycle 2

palaeocurrents change back to a west-northwest direction.

Megacycle 3 was most likely again fed from the northern

margin of the basin. Its basin plain and fringe deposits resulted

from westward (N270E mean) flowing turbidity currents. Assuming

that the orientation of the basin axis remained more or less

constant throughout the early Eocene, this implies a northern

derivation for megacycle 3. This conclusion is supported by the

petrography, which is similar to that of megacycle 1.

III.3« The Zarauz-Guetaria section (enclosure 2)

The Zarauz-Guetaria section was measured al.ong the coastal

road from Zarauz to Guetaria. The strata here are in overturned

position and dip about 55 degrees to the east-southeast (Pig. 3).

The exposed part of the section includes portions of megacycles 1

and 2, as described from the Zumaya-Guetaria section. A

difference with the latter section, however, is the absence of

basin plain deposits between these megacycles. Pan fringe

- 23 -

deposits of quartz-arenitic megacycle 1 are directly succeeded by

fan fringe deposits of lithic arenitic megacycle 2.

The main interest in the Zarauz-Guetaria section concerns

the reconstruction of its palaeocurrents. In view of the

completely aberrant strike and dip (Pig. 3), correction for dip

alone is certainly not sufficient. The palaeocurrents shown in

enclosure 2 are only dip-corrected, which is merely meant as a

way of recording field observations.

Owing to poor exposure conditions, the structural

relationship of the overturned Zarauz-Guetaria section to the

normal dipping Zumaya-Guetaria section is far from clear. A fault

contact between normal and overturned dipping strata is only

exposed on the eastern side of the peninsula of Guetaria. Hanisch

(1975 and 1978), basing his work on a lead-plate model,

interprets both sections as the flanks of a synclinal fold with a

steeply plunging axis. In the present author's opinion Hanisch's

model suffers from scaling problems. Folding a lead-plate is not

simply comparable with folding a stratigraphie succession of

2.5 kilometres thickness containing competent thick-bedded fan

turbidites. It is not very likely that the entire Lower Tertiary

should be folded without faulting into such a tight fold as that

implied by Hanisch (1975 and 1978).

In this study a major fault separating the normal and

overturned sections is postulated. This is supported by the

observation of a fault contact on Guetaria (Pig. 3). Such a fault

makes an attempt to accurately reconstruct palaeocurrents of

doubtful validity. Nevertheless, regardless of any

reconstruction, an interesting observation can be made with

respect to palaeocurrent trends in the overturned succession. In

the Zarauz-Guetaria section the transition from megacycle 1 to

megacycle 2 coincides with an abrupt change in palaeocurrents

(about 100 degrees clockwise). This abrupt change confirms a

derivation from opposite basin margins for megacycle 1 (north)

and megacycle 2 (south). In the 'downstream' Zumaya-Guetaria

section megacycle 1 and the lower part of megacycle 2 (basin

plain deposits) were both deposited from axially flowing

- 24 -

currents. In the 'upstream' Zarauz-Guetaria section megacycle 2

turbidity currents were not yet reoriented parallel to the basin

axis (Pig. 59). Reconstruction of palaeocurrents in the Zarauz-

Guetaria section should be based on regional palaeocurrent

knowledge (approx. 270 measurements, see Pig. 59) rather than on

poor to non-definable structural relationships. Although in the

Zarauz-Guetaria section accurate reconstruction is impossible,

palaeocurrent trends correspond to a regional picture when 150

degrees (clockwise) have been added to the dip-corrected

measurements of enclosure 2 (see Pig. 59). This means that the

palaeocurrents in megacycle 1 are brought to an orientation

intermediate between the orientations observed in the Zumaya-

Guetaria section and the Orio section.

III.4. The Orio section (enclosure 3)

Por reasons of exposure, the Orio section as shown in

enclosure 3 is a composite section (Pig. 9). The lowermost part

(0-150 m) is derived from observations at Zaricola. Prom 150 to

750 metres the section was measured on the west-bank of the Oria

estuary, while detailed sedimentological data were in part

obtained from fresh motorway-cuts. The upper part of the section

(750-1200 m) is almost continuously exposed along the east-bank

of the estuary and the adjacent coastal zone up to Aizualquichl.

The integration into one section is made feasible by the fact

that certain lithological units are directly expressed in the

landscape (Pig. 30).

The uppermost Maastrichtian and Paleocene (not shown in

enclosure 3), which in surrounding areas are fine-grained basinal

deposits, consist of 'anomalous' facies near Orio. A detailed

analysis of the highly complex stratigraphy near Orio was carried

out by Hanlsch (1974). Local occurrences of slumps,

olistostromes, pebbly mudstones, graded clast-supported

conglomerates, breccias and proximal carbonate turbidites were

recorded by him. Towards the east these 'chaotic' facies (max.

thickness about 200 m) thin gradually and interdigitate with

- 25 -

'normal' basin plain deposits north of Usurbil. Westward they

seem to disappear rather abruptly by onlap onto the diapiric

structure of Zarauz (cf. Hanisch 1974). Hanisch suggests these

anomalous facies represent the fill of a rim-syncline by material

derived from the diapir. In the next chapter this interpretation

will be discussed and considered in a regional context.

The chaotic complex is overlain by an Upper Paleocene

(NP 7-8) lime-mudstone and marl succession (~ 50 m thick)

containing only minor chaotic bodies. Above this largely pelagic

interval a progradational turbidite succession is observed

(enclosure 3, 20-100 m) which forms a marked ridge in the

topography (Pig. 30). The turbidites are of quartz-arenitic

composition and are often conglomeratic (detail-section 9)«

Palaeocurrent indicators are virtually absent. Westwards the body

wedges out rapidly (over about 2 km) between Orio and Zarauz

(Kruit et al. 1975, Hanisch 1978). Towards the east it splits

into two turbidite bundles that gradually shale out near Ibaeta.

Poor exposure does not permit a detailed analysis. This body is

tentatively interpreted as being composed of two amalgamated fan

lobes.

The body is overlain by a 400 metres thick monotonous basin

plain succession of a mixed turbiditic and (hemi-)pelagic origin

(Pigs. 31 and 32, detali-section 10). Tc_e and Td e Bouma-

sequences predominate. Pew turbidite soles are exposed due to the

'welding together' of turbidites and their underlying pelagic

limestones by cementation. The few that are exposed indicate

westward transport. The turbidites are mainly bioclastic with an

admixture of terrigenous components.

Near the motorway viaduct over the Oria estuary, carbonate-

cemented quartz-arenitic turbidites mark the onset of

megacycle 1. Prom 500 to 940 metres, megacycle 1 comprises three

asymmetric cycles. The cycles begin with basin plain deposits and

continue through fan fringe deposits into outer fan deposits. The

lobe megasequences capping the cycles are 30 to 40 metres thick

and contain individual beds up to 5 metres. The basin plain and

fan fringe deposits of the second cycle are illustrated in bed-

- 26 -

thickness-log 10 and Pig. 33• The very top of the second cycle

and the base of the third cycle are shown in detail-section 11.

The lobe megasequence from the top of the third cycle is

represented by Pigs. 34 and 35, detail-section 12 and bed-

thickness-log 11. After the third cycle only a subtle recession

is observed. Distal outer fan deposits form the top of the Orio

section (940-1200 m). They consist of stacked distal lobe mega-

sequences, 10 to 20 metres thick and characterised by:

- gradual upward thickening and coarsening of beds;

- substantial, although upward decreasing, numbers of interbedded

thin distal turbidites;

- abundant rip-up clasts.

Examples of these megasequences are shown in Pigs. 36 and 37,

detail-sections 13 to 15 and bed-thickness-logs 12 and 13-

Throughout megacycle 1 southwesterly palaeocurrents

predominate.

III.5- The San Sebastian area

In the immediate vicinity of San Sebastian a long section

through the Lower Tertiary cannot be measured for lack of

accessible exposures. However, a few isolated exposures deserve

some attention. All these exposures are in quartz-arenitic

megacycle 1 and are discussed below from west to east.

Lurmanda

The headland of Lurmanda forms the very top of the

stratigraphie succession as preserved in the San Sebastian area.

Bed-thickness-log 14 represents the accessible lower part of a

thickening-upward lobe megasequence. Note that the interbedding

of thin distal turbidites clearly disappears gradually upward.

This part of the megasequence thus reflects progradation of the

distal portion of a depositional lobe and the build-up lobe

relief.

- 27 -

Chlmistarri

Around the headland of Chlmistarri middle fan deposits are

exposed. Figure 38 shows another example of a small channel with

lateral accretion deposits and a shaly post-abandonment fill

('clay plug').

Detail-section 17 was measured on the headland proper. Note

the scour-and-fill structures and the deformed mega-crossbedded

sets in the upper part of the section (see also Pig. 39). The

very coarse-grained megaripple beds in the lower part of the

section are thought to be tractional lags of by-passing high-

density turbidity currents (cf. Mutti and Ricci Lucchi 1975,

facies B2). Palaeocurrent measurements Indicate transport towards

south-southwest.

The middle fan deposits of Chimistarri are significant in

the sense that they are the westernmost observed middle fan

deposits within megacycle 1.

San Sebastian-West

Along the boulevard at the foot of the Monte Igueldo a

succession of about 65 metres is exposed in the basal part of

megacycle 1. Bed-thickness-log 15 covers the entire succession

and displays a distinct overall thickening-upward trend diluted

in a matrix of thin-bedded turbidites (about 50 per cent of the

beds is thinner than 5 cm). Part of the succession is shown in

detail-section 16 ' . Bouma B-divisions predominate, grading is

subtle and interbedded pelagic lime-mudstones are well developed

(Pig. 40). In places turbidite-mud is practically absent

(Pig. 40). The section is interpreted as a fan fringe deposit.

San Sebastian-East

Prom the eastern extremity of the Playa de Gros to

Punta Mompas the lower part of megacycle 1 is discontinuously

*) Black dots indicate corresponding beds on bed-thickness-log 15 and detail-section 16.

- 28 -

exposed. Bed-thickness-log 16 and detail-section 18 ; pertain to

fan fringe deposits similar to those observed in San Sebastian-

West, but an accurate correlation between the two localities is

not feasible. Figures 41 to 43 highlight some small-scale facies

characteristics.

Bed-thickness-log 17 and detail-section 19 both cover an

adjacent exposure, starting about 25 metres stratigraphically

above the top of detail-section 18. Interbedding of thin-bedded

distal turbidites is strongly reduced and there is a distinct

thickening-upward trend. Megaripple beds (detail-section 18:

6.5 m, 19 m and 29 m) are interpreted as tractional lags of by­

passing high-density turbidity currents (cf. Mutti and

Ricci Lucchi 1975, facies B2).

In conjunction, detail-sections 18 and 19 illustrate the

basal progradation, from fan fringe to outer fan, of the

megacycle 1 system. The progradation is accompanied by a slight

change in palaeocurrent direction from westerly to southwesterly.

III.6. The Pasajes section (enclosure 4)

An impressive megacycle 1 sandstone succession of 800 metres

thickness is discontinuously exposed along the harbour inlet of

Pasajes. Concentrations of thick-bedded proximal turbidites are

clearly expressed as ridges in the topography (Pig. 45).

Observations in a series of small exposures along the road from

Pasajes de San Juan to Lezo (not shown in enclosure 4) suggest

that the sandstone succession gradually developed from more shaly

thin-bedded turbidite facies. Up to approx. 550 metres the

concentrations of thick-bedded proximal turbidite regularly

exhibit small-scale (metre-scale depths) channelling (Pig. 46).

Only the top 64 metres of the Pasajes section are exposed well

enough to allow a detailed examination (Pigs. 47 and 48). Bed-

thickness-log 18 and detail-section 20 comprise two coarsening-

*) Open circles indicate corresponding beds on bed-thickness-log 16 and detail-section 18.

- 29 -

and thickening-upward megasequences separated by a thinner bedded

interval. The megasequences proper lack thin-bedded distal

turbidites and are interpreted as proximal lobe deposits.

On the east side of the nearby Ensenada Murguita similar

deposits are spectacularly, but inaccessibly, exposed over a

thicker interval (Pig. 44).

III.7« Monte Jaizkibel: Leznobar to Cabo Hlguer

As first noted by Kruit et al. (1972), the Monte Jaizkibel

represents the topographic expression of the proximal part of the

megacycle 1 fan system. The marked depression in the landscape

south of the Monte Jaizkibel covers a more shaly basin plain type

succession of Paleocene to earliest Eocene age. Inland exposures

on the Monte Jaizkibel are rather poor and strongly weathered.

Locally the leached sandstones are even quarried for loose sand.

Access to the military zone between Pasajes de San Juan and

Leznobar could not be obtained from the authorities. At Leznobar

and Punta Turrilla partly accessible exposures in middle fan

deposits could be studied in some detail. The Leznobar exposure

is shown in Pigs. 49 to 51 and partly in detail-section 21. A

very thick-bedded facies overlies with a gently scouring base a

relatively thin-bedded succession. In the thick-bedded interval

there is a crude overall coarsening- and thickening-upward trend

(Pig. 49) and common basal scouring of individual units. A highly

characteristic feature of the thinner bedded facies is the

abundance of erosionally based megaripple formsets and mega-

crossbedded scour-and-fills, capping the otherwise horizontally

laminated beds (detail-section 21: 0-9 m, Pigs. 50 and 51). The

foresetting is often deformed into recumbent folds. The

crossbedded units have bioturbated tops draped by hemipelagic

marl. In combination, all these features point to erosion and

subsequent, short-lived, tractional reworking of turbidite tops.

The thick-bedded part of the Leznobar exposure is

interpreted as a lobe-apex ('sufrafan') deposit. Consequently,

the thinner bedded part is likely to represent a deposit on the

- 30 -

flanks of such a lobe apex or In between lobe apices. The

tractional reworking Is tentatively interpreted as being caused

by the tails of high-density turbidity currents and/or their

subsequent suction currents.

The sequence in the exposure at Punta Turrilla (Pig. 52) is

basically similar to the section of Leznobar. Some peculiar

fluidisatlon phenomena in an isolated exposure about 1 kilometre

east of Punta Turrilla are shown in Pigs. 53 and 54.

Prom Leznobar eastwards the stratigraphie succession becomes

progressively more incomplete due to truncation by the shoreline.

The coastal exposures near Cabo Higuer pertain to the lower part

(NP 11) of megacycle 1 and comprise mainly middle fan deposits.

Detail-section 22 covers a relatively thin-bedded interval with

common erosionally based megaripple formsets, like at Leznobar,

and mud-covered erosion surfaces (at 25 and 29 m). The

interbedding of pelagic lime-mudstones in middle fan deposits is

noteworthy. Figure 55 shows the top of a relatively thick-bedded

concentration of proximal turbidites with internal channelling.

Detail-section 23 represents the deepest accessible stratigraphie

levels along the north coast of the Monte Jaizkibel and marks,

with its dominance of planar beds, the downward transition to

outer fan lobe deposits. Figures 56 and 57 highlight the splendid

examples of dish-structures in the exposure.

Palaeocurrents of the Monte Jaizkibel area display a

suggestive radiating (100 degrees) pattern (Pig. 59), first

recognised by Kruit et al. (1972).

Near the fishing port of Fuenterrabia the quartz-arenltic

outer to middle fan deposits of megacycle 1 abruptly overly fan

fringe deposits (Fig. 58). This quasi progradational

superposition is somewhat misleading, as these fan fringe

deposits are not genetically related to megacycle 1. They are

almost exclusively bioclastic and their westerly palaeocurrents

strongly contrast with the east-southeasterly palaeocurrents of

megacycle 1.

- 31 -

IV. REGIONAL SYNTHESIS AND DISCUSSION

IV.1. Regional synthesis (Summarised in Pigs. 59 and 60 and

enclosure 9)

Throughout this report the turbidltic Lower Eocene part of

the Tertiary outcrop in Guipuzcoa has been emphasized. On a

regional scale the Paleocene is definitely not sufficiently

exposed to permit a sophisticated analysis of its stratigraphy

and sedlmentology. With this limitation in mind an attempt has

been made to reconstruct the complete sedimentary history of the

Guipuzcoan basin from the base Tertiary onwards. The Paleocene

boundaries shown on the cross-section of Pig. 60 should, however,

be considered as tentative for the eastern part of the area.

The lowermost Paleocene (Danian) is regionally characterised

by rose coloured pelagic lime-mudstones exposed near Zumaya,

San Sebastian, Pasajes and Puenterrabia. Between Zarauz and

Usurbil this pelagic facies is absent to very poorly developed

and replaced by a localised 'chaotic' complex, which reaches its

maximum thickness (~ 200 m) near Orio. The rose coloured pelagic

lime-mudstones are interpreted as a slow deposition facies in a

deep-marine basin virtually lacking clastic input. The absence of

elastics can in part be attributed to an elevated depositional

setting in a basin with a hilly bottom topography, caused by late

Cretaceous to early Paleocene diapirism of Keuper evaporites (cf.

Hanisch 1974). Hanlsch (op. cit.) interprets the 'chaotic'

complex of Orio as the filling of the rim syncline of his

'Zarauz-diapir' by material derived from that diapir. Feulllée

and Mathey (1976), however, in all reason question the concept of

Hanlsch and Pflug (1973) that well rounded pebbles, as found in

the Orio complex, could form within an evaporitic mass during its

diapiric ascent. A contemporary nearby shallow-marine source for

the well rounded pebbles is an almost inevitable requirement.

Hence, some uncertainty exists as to the nature of Hanlsch's

(1974 and 1978) intrabasinal deep-marine diapir.

The Upper Paleocene regionally shows the following

differences compared to the Lower Paleocene:

- 32 -

- interbedding of hemipelagic marls Is considerable and Increases

further upward;

- lime-mudstones and marls lose their reddish colours in the

lower part of the Upper Paleocene;

- bioclastic turbidites appear, mainly in the east

(Puenterrabia), and become progressively more common upward. In

the west (Zumaya), (hemi-)pelagic sedimentation continues to

dominate.

Between Orio and Usurbil minor chaotic bodies, embedded in a

largely (hemi-)pelagic facies, still occur. This area remains

stratigraphically anomalous until the earliest Eocene, as it also

contains a localised very coarse-grained submarine fan body in

the basal Tribrachiatus contortus zone (NP 10). Poor exposure

precludes a detailed analysis of this body. On the basis of its

quartz-arenitic composition a northerly derivation is suggested

by comparison with younger fan systems.

The Tribrachiatus contortus zone (NP 10) and the lowermost

Discoaster binodosus zone (NP 11) are represented by mixed

turbiditic and (hemi-)pelagic basin plain deposits that thin

remarkably rapidly westward, beyond Orio, and become replaced by

exclusively (hemi-)pelagic facies near Zumaya. Only in the

extreme east (Puenterrabia) can fan fringe deposits be recognised

in this interval (Pig. 58). The turbidites are composed of

carbonate bio- and lithoclasts with an admixture, usually less

than 10 per cent, of terrigenous components. Palaeocurrents were

directed towards the west, at least in the zone between

Puenterrabia and Orio.

Almost the entire Discoaster binodosus zone and the lower

half of the Tribrachiatus orthostylus zone (NP 12) are formed by

quartz-arenitic megacycle 1. The Discoaster binodosus zone as a

whole thins clearly towards Zumaya. Widespread interbedding of

pelagic lime-mudstones is still present up to the lower

Tribrachiatus orthostylus zone. In megacycle 1 basin plain, fan

fringe, outer fan and middle fan turbidite facies associations

- 33 -

can be distinguished. In the east megacycle 1 displays a

suggestive radiating palaeocurrent pattern (Pig. 59), indicating

an entry point a few kilometres north of the Monte Jaizkibel. An

additional entry point was probably situated north of the

Monte Igueldo. West of San Sebastian megacycle 1 palaeocurrents

were gradually bent (Pig. 59) until they flowed towards the west-

northwest in the Zurnaya area. The bending of palaeocurrents, the

rapid westward thinning of the turbidite successions in NP 10 and

NP 11 (Pig. 60 and enclosure 9) and their replacement by a

(hemi-)pelagic fades, all strongly point to an elevated area in

the west (Zarauz to Zurnaya). Hanisch's (1974 and 1978)

intrabasinal deep-marine diapir was probably only part of a much

larger complex, which in its entity formed a protrusion of the

southern basin margin. In this context Hanisch's (1974) rim

syncline can be regarded as a re-entrant of that margin in

between diaplric complexes.

Initially (NP 11 and lowermost NP 12) the megacycle 1 fan

system was obstructed in its progradation into the slightly

elevated western zone. Later, with increased sedimentation rates,

as deduced from the disappearance of lime-mudstone interbeds, fan

progradation reached into the Zurnaya area, giving rise to a thick

pile (~ 400 m) of fan fringe deposits.

In the Zumaya-Guetaria and Zarauz-Guetaria sections the more

complete stratigraphie record allows further reconstruction of

the basin history. In the upper part of the Trlbrachiatus

orthostylus zone megacycle 1 shows a recessional trend towards

basin plain deposits. Quartz-arenitic megacycle 1 is overlain by

a thick succession (~ 1000 m) of llthic-arenitic turbidites

making up megacycle 2.

Megacycle 2 covers the uppermost Trlbrachiatus orthostylus

zone, the Dlscoaster lodoensls zone (NP 13) and the lowermost

Discoaster sublodoensis zone (NP 14). Palaeocurrents in

megacycle 2 (Pig. 59) indicate a southern entry point. The system

was probably fed via the previously suggested re-entrant of the

southern basin margin near Orio. In megacycle 2 a spectrum of

- 34 -

turbidite facies associations, ranging from basin plain to middle

fan, can be recognised.

The Lower* Tertiary succession is completed by another

quartz-arenitic fan system (megacycle 3, NP 14), supplied via the

northern basin margin.

In summary, the early Tertiary sedimentary history of the

basin can be described in terms of three main phases:

- a phase of slow, almost exclusively, pelagic deposition (early

Paleocene and most of the late Paleocene);

- a phase of deposition from westward axially flowing turbidity

currents (latest Paleocene to earliest Eocene);

- a phase of lateral sediment input via submarine fans fed from

opposite basin margins (early Eocene, NP 11-14).

The stratigraphie superposition of submarine fan facies

derived from opposite basin margins thus indicates that the early

Tertiary Guipuzcoan basin must have been relatively narrow,

probably only a few tens of kilometres wide. Late Cretaceous to

early Paleocene diapirism created swells and depressions in the

basin floor and controlled the deposition of turbidite facies

well into the early Eocene (before deposition of NP 12).

IV.2. Discussion

It should be borne in mind that a basin history as outlined

in the preceding section is based on an isolated narrow strip of

stratigraphie record. This limitation becomes even more important

when the early Tertiary Guipuzcoan basin as a whole has to be

placed in a regional context. Its actual basin margins have not

been preserved. Nor are there any nearby outcrops of time-

equivalent shallow-marine, coastal or terrestrial facies. The

Palaeogene slope and shallow-marine deposits exposed near

Biarritz and Bayonne (Pig. 1) are dinstinctly younger in age

- 35 -

(Middle Eocene-Lower Oligocène, BRGM et al. 1974) than the Lower

Tertiary outcropping in Guipuzcoa.

The Tertiary outcrop of the nearby Vizcaya synclinorium

(Paleocene-Middle Eocene) consists almost exclusively of deep-

marine sediments. Shallow-marine carbonates (Lower Eocene) are,

very locally, preserved along the southeastern margin of this

outcrop (Rat 1959, Plaziat 1975). The Vizcaya synclinorium has

been excluded from this study in view of its extremely poor

exposure conditions.

Plaziat (1975) concentrated on Paleocene resedlmented

carbonates from the Vizcaya synclinorium, Navarra and Guipuzcoa,

and.concluded that an extensive carbonate platform must have

bordered the Paleocene Basque deep-water basin(s) in the south. A

largely pelagic deep-marine Paleocene is not restricted to

Guipuzcoa. Quite similar facies can be observed in outcrops in

Vizcaya (Sopelana) and Navarra (Eugui, north of Pamplona). In the

entire Pyrenean realm the Paleocene represents an episode in

which clastic input into marine environments was arrested. This

can be attributed to a regional early Tertiary transgression (cf.

Plaziat 1975) following the terminal Cretaceous regression. The

arid climatic conditions that can be interpreted from the

Paleocene terrestrial facies ('Garumnian') in the eastern

Pyrenees will certainly have contributed to sediment starvation

in marine environments. Consequently, it can be stated that the

Guipuzcoan Paleocene fits very well in a Pyrenean context

The Lower Eocene turbidite successions of Guipuzcoa provide

direct evidence for an elongated narrow basin with a west-

northwesterly axial plunge. This is consistent with the model of

a North-Pyrenean transform zone as discussed by Choukroune and

Mattauer (1978) . In this model, from the Albian onwards a series

of en-échelon arranged, narrow and deep basins were formed along

a North-Pyrenean wrench fault zone. During the late Cretaceous

these basins became open-ended towards the northwest by

- 36 -

extension. The Upper Cretaceous pillow basalts of Guipuzcoa and

Vizcaya (see Rat 1959) mark this phase of 'opening'.

The source area of the quartz-arenitic submarine fans in the

Guipuzcoan basin remains a major problem. The entry point north

of the Monte Jaizkibel for megacycle 1 obviously suggests a

derivation from the 'Landes Marginal Plateau' or possibly an area

around Bordeaux (Kruit et al. 1975). The east-west trending

Cap Breton Canyon (Pig. 1) does not interfere with such an

interpretation. This canyon is a post-Eocene feature (Montadert

et al. 1974, Boillot et al. 1972) which roughly follows the

submarine North-Pyrenean thrust front. Seismic lines across the

Landes Marginal Plateau (Damotte et al. 1969, Winnock et al.

1973, Montadert et al. 1974) do not provide evidence for an

important and widespread Lower Eocene hiatus. Wells in the

western Aquitaine basin encountered a Lower Eocene dominated by

shallow-marine shales and carbonates (BRGM et al. 1974, map 22).

Thus the interpretation of a northerly source area for the

Guipuzcoan quartz-arenites seems not justified. At this point a

comparison with probably the best known modern submarine fan, the

Navy Pan (Normark et al. 1979), may be useful. Navy Pan

(California Borderland) occurs in a tectonic setting even fairly

similar (cf. Choukroune and Mattauer 1978) to the early Tertiary

Guipuzcoan basin. This fan is fed via a long channel system

(~ 100 km) with a complex, tectonically determined, winding

course (Normark et al. 1979, Pig. 2). Prediction of the position

of the canyon head from radiating fan palaeocurrents in this case

would result in a directional error of some 60 degrees. Keeping

this in mind, one could also envisage northeasterly to easterly

sources for the Guipuzcoan quartz-arenites. One 'advantage' of

easterly sources in the Aquitaine basin over northerly sources is

that they are somewhat more sand-prone (cf. BRGM et al. 1974,

map 22).

ACKNOWLEDGMENTS

I would like to express my sincere thanks to Dr. C. Kruit, not

only for enabling me to start this study while I was still at

Leiden University but also for his contribution to my geological

education in a more general sense. For fruitful cooperation, in

particular in matters concerning the biostratigraphy, I thank

Mr. J. Brouwer. I am grateful to Mr. B. Prins, who provided me

with the basic knowledge required to start the nannoplankton

work. Dr. B.K. Levell is acknowledged for his valuable comments

on the manuscript and for his effort to Improve the English. In a

later stage the manuscript benefitted from suggestions by

Prof. J.D. de Jong and Prof. C.W. Drooger. Mr. H. Veele was of

great help to me with the draughting of some figures.

Finally I am indebted to Shell Internationale Petroleum

Maatschappij B.V. for permission to publish this study.

- 37 -

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Transact. Gulf Coast Assoc. Geol. Soc, vol. 17,

pp. 428-480.

Jacka, A.D., Beck, R.H., St. Germain, L.C. & Harrison, S.C.,

1968, Permian deep-sea fans of the Delaware Mountain Group

(Guadalupian), Delaware Basin.

In: Guadalupian Facies, Apache Mountain Area, West Texas.

Soc. Econ. Paleont. Mineral., Permian Basin Section, Publ.

68-11, pp. 49-90.

Jerez Mir, L., Esnaola Gomez, J.M. & Rubio Susan, V., 1971,

Estudio Geologico de la Provincia de Guipuzcoa.

Mem. Inst. Geol. Min. Esp., vol. 79«

Kapellos, C , 1974, Ueber das Nannoplankton im Alttertiär des

Profils von Zumaya-Guetaria (Provinz Guipuzcoa, Nord

Spanien).

Ecl. Geol. Helv., vol. 67, pp. 435-444.

Kruit, C , Brouwer, J. & Ealey, P., 1972, A deep-water sand fan

in the Eocene Bay of Biscay.

Nature Phys. S c , vol. 240, pp. 59-61.

, Brouwer, J., Knox, G., Schöllnberger, W. &

Van Vliet, A., 1975, Une excursion aux cones d'alluvions

en eau profonde d'âge tertiaire pres de San Sebastian

(Province de Guipuzcoa, Espagne): Excursion 23, Proc. IX

Int. Congr. of Sediment. Nice, 75 p.

- 40 -

Lamare, P., 1952, La structure géologique des Pyrénées Basques.

In: Actas del primer congreso internacional de estudios

Pyrenaicos, San Sebastian, 1950, vol. 2, sect. 1,

pp. 1-44.

Lotze, P., 1953, Salzdiapirismus im nördlichen Spanien.

Zeitschr. Deutsch, geol. Ges., vol. 105, pp. 814-822.

Lowe, D.R., 1975, Water escape structures in coarse-grained

sediments.

Sediment., vol. 22, pp. 157-204.

, 1976, Grain flow and grain flow deposits.

J. Sed. Petrol., vol. 46, pp. 188-199-

Martini, E., 1971, Standard Tertiary and Quaternary calcareous

nannoplankton zonation.

In: A. Farlnacci (ed.), Proc. 2nd Planktonic Conference,

Rome, 1970, pp. 739-786.

Marschalko, R., 1970, The origin of disturbed beds in Carpathian

turbidites.

Sed. Geol., vol. 4, pp. 5-18.

Middleton, G.V. & Hampton, M.A., 1973, Sediment gravity flows:

mechanics of flow and deposition.

In: G.V. Middleton & A.H. Bouma (eds.), Turbidites and

deep-water sedimentation.

Soc. Econ. Paleont. Mineral., Pacific Section, Short

course, Anaheim, pp. 1-38.

Montadert, L., Winnock, E., Delteil, J.R. & Grau, G., 1974,

Continental margins of Galicia-Portugal and Bay of Biscay.

In: C.A. Burk & CK. Drake (eds.), The geology of

continental margins.

Springer, pp. 323-342.

Mutti, E., 1977, Distinctive thin-bedded turbidite facies and

related depositional environments in the Eocene Hecho

Group (South-central Pyrenees, Spain).

Sediment., vol. 24, pp. 107-131.

- 41 -

, 1979, Turbldites et cones sous-marins profonds.

In: P. Homewood (ed.), Sedimentation détritique

(fluviatile, littorale et marine).

Inst. Geol. Univ. Pribourg/Suisse, pp. 353-419.

& Ghibaudo, G., 1972, Un esempio di torbiditi di

conoide sottomarina esterna: Le Arenarie di San Salvatore

(Pormazione di Bobbio, Miocene) nell' Appennino di

Piacenza.

Mem. Ace. Sei. Torino, Cl. Sei. Pis. Mat. 16, pp. 1-40.

& Johns, D.R., 1978, The role of sedimentary by­

passing in the genesis of basin plain and fan fringe

turbidites.

Boll. Soc. Geol. Ital., vol. 18, pp. 15-22.

& Ricci Lucchi, P., 1972, Le torbiditi dell' Appennino

settentrionale: introduzione all' analisi di facies.

' Mem. Soc. Geol. Ital., vol. 11, pp. 161-199«

& Ricci Lucchi, P., 1974, La signification de

certaines unités séquentielles dans les séries a turbidites

Bull. Soc. Geol. Prance, vol. 16, pp. 577-582.

& Ricci Lucchi, P., 1975, Turbidite facies and facies

associations.

In: E. Mutti et al., Examples of turbidite facies and

facies associations from selected formations of the

Northern Appenines: Excursion 11, Proc. IX Int. Congr. of

Sediment. Nice, pp. 21-36.

Nelson, C.H., 1976, Late Pleistocene and Holocene depositional

trends, processes and history of Astoria deep-see fan,

Northeast Pacific.

Mar. Geol., vol. 20, pp. 129-173.

, Carlson, P.R., Byrne, J.V. & Alpha, T.R., 1970,

Development of the Astoria Canyon-Pan physiography and

comparison with similar systems.

Mar. Geol., vol. 8, pp. 259-291.

- 42 -

& Kulm, L.D., 1973, Submarine fans and channels.

In: G.V. Mlddleton & A.H. Bouma (eds.), Turbidites and

deep-water sedimentation.

Soc. Econ. Paleont. Mineral., Pacific Section, Short

Course, Anaheim, pp. 39-78.

Nilsen, T.H., 1980, Modern and ancient submarine fans: Discussion

of papers by R.G. Walker and W.R. Normark.

Amer. Assoc. Petr. Geol. Bull., vol. 64, pp. 1094-1101.

Normark, W.R., 1970, Growth patterns of deep-sea fans.

Amer. Assoc. Petr. Geol. Bull., vol. 54, pp. 2170-2195.

3 1974, Submarine canyons and fan valleys: Factors

affecting growth patterns of deep-sea fans.

In: R.H. Dott & H.A. Shaver, Modern and ancient

géosynclinal sedimentation.

Soc. Econ. Paleont. Mineral., Spec. Pub. 19, PP« 56-68.

, 1978, Pan valleys, channels and depositional lobes on

modern submarine fans: Characters for recognlstion of

sandy turbidite environments.

Amer. Assoc. Petr. Geol. Bull., vol. 62, pp. 912-931-

& Piper, D.J.W., 1972, Sediments and growth pattern of

Navy Deep-sea fan, San Clémente Basin, California

Borderland.

J. Geol., vol. 80, pp. 198-223.

, Piper, D.J.W. & Hese, G.R., 1979, Distributary

channels, sand lobes and mesotopography of Navy Submarine

Pan, California Borderland, with applications to ancient

fan sediments.

Sediment., vol. 26, pp. 749-774.

Plaziat, J.C., 1975,

Signification paléogéographigue des 'calcaires conglomérées',

des brèches et des niveaux a rhodophycées dans la

sédimentation carbonatée du Bassin Basco-Béarnais, a la base du

Tertiäre (Espagne-France).

Rev. Géogr. Phys. Géol. Dyn., vol. 17, pp. 239-258.

Postuma, J.A., 1971, Manual of planktonic Foraminifera.

Elsevier Publ. Cy., Amsterdam, London, New York.

- 43 -

Rat, P., 1959, Les pays crétacés basco-cantabriques (Espagne).

Thesis, Publ. Univ. Dijon, vol. 18, 525 pp.

Reineck, H.E., 1973, Schichtung und Wühlgefüge in Grundproben vor

der ostafrikanischen Küste.

'Meteor' Forsch. Ergebn. C. 16, pp. 67-81.

Ricci Lucchi, F., 1965, Alcune strutture di risedimentazione

nella formazione Marnoso-Arenacea Romagnola.

Giorn. Geol., vol. 33, pp. 265-283.

, 1975a, Miocene paleogeography and basin analysis in

the Periadriatic Apennines.

In: C. Squyres (ed.), Geology of Italy. Tripoli (1977),

pp. 129-236.

, 1975b, Depositional cycles in two turbidite

formations of Northern Apennines (Italy).

J. Sed. Petrol., vol. 45, pp. 3-43.

, 1978, Turbidite dispersal in a Miocene deep-sea

plain: The Marnoso-Arenacea of the Northern Apennines.

Geol. en Mijnb., vol. 57, pp. 559-576.

& Parea, G.C., 1973, Cicli deposizionali

(megasequenze) nelle torbidlte di conoide sottomarina:

formazione della laga (appennino marchigiano-abruzzese).

Atti Soc. Nat. Mat. Modena, vol. 104, pp.. 247-283.

& Valmori, E., 1980, Basin-wide turbidites in a

Miocene, over-supplied deep-sea plain: a geometrical

analysis.

Sediment., vol. 27, pp. 214-270.

Rupke, N.A., 1976, Sedimentology of very thick calcarenite-

marlstone beds in a flysch succession, Southwestern

Pyrenees.

Sediment., vol. 23, pp. 43-65«

Seilacher, A., 1967, Paleontological studies on turbidite

sedimentation and erosion.

J. Geol., vol. 70, pp. 227-234.

- 44 -

Shepard, P.P., Dill, R.F. & Von Rad, U., 1969, Physiography and

sedimentary processes of La Jolla Submarine Pan and Pan-

valley, California.

Amer. Assoc. Petr. Geol. Bull., vol. 53, pp. 390-420.

Surlyk, P., 1978, Submarine fan sedimentation along fault scarps

on tilted fault blocks (Jurassic-Cretaceous boundary, East

Greenland).

Grtfnl. Geol. Understfgelse., Bull. 128, 108 pp.

Van Vliet, A., 1978, Early Tertiary deep-water fans of Guipuzcoa,

Northern Spain.

In: D.J. Stanley & G. Kelling (eds.), Sedimentation in

submarine canyons, fans and trenches.

Dowden, Hutchinson and Ross, Stroudsburg, Pennsylvania,

pp. 190-209.

Von Hillebrandt, A., 1965, Poraminiferen-Stratigraphie im

Alttertiär von Zumaya (Provinz Guipuzcoa, NW Spanien) und

ein Vergleich mit anderen Tethys-Gebieten.

Bayr. Akad. Wiss., Math. Nat. Kl. Abh., N.P., 123, 62 pp.

Walker, R.G., 1966, Shale Grit and Grindslow Shales, transition

from turbidite to shallow water sediments in the Upper

Carboniferous of northern England.

J. Sed. Petrol., vol. 36, pp. 90-114.

, 1967, Turbidite sedimentary structures and their

relationship to proximal and distal depositional

environments.

J. Sed. Petrol., vol. 37, pp. 25-43.

, 1978, Deep-water sandstone facies and ancient

submarine fans: models for exploration for stratigraphie

traps.

Amer. Assoc. Petr. Geol. Bull., vol. 62, pp. 932-966.

, 1980, Modern and ancient submarine fans: Reply.

Amer. Assoc. Petr. Geol. Bull., vol. 64, pp. 1101-1108.

- 45 -

& Mutti, E., 1973, Turbidite facies and facies

associations.

In: G.V. Middleton & A.H. Bouma (eds.), Turbidites and

deep-water sedimentation.

Soc. Econ. Paleont. Mineral., Pacific Section, Short

Course, Anaheim, pp. 119-157.

Winnock, E., Pried, E. & Kieken, M., 1973, Les charactéristiques

des sillons aquitains.

Bull. Soc. Géol Prance, vol. 15, pp. 51-60.

CURRICULUM VITAE

Arthur van Vliet werd geboren op 30 september 19^9 te Haarlem.

Na de lagere school bezocht hij het Lorentz Lyceum aldaar en

behaalde In 1967 het diploma Gymnasium B. In datzelfde jaar begon

hij zijn studie geologie aan de Rijksuniversiteit te Leiden waar

hij in 1973 het doctoraal examen geologie, met bijvakken

sedimentologie en micropaleontologie, aflegde. Na korte tijd als

wetenschappelijk medewerker werkzaam te zijn geweest bij de

Rijksuniversiteit te Leiden is hij sinds september 197^ als

sedimentoloog in dienst van het Koninklijke/Shell Exploratie en

Produktie Laboratorium te Rijswijk.

Het veldwerk voor dit proefschrift werd verricht in de jaren 1974

en 1975-

Post Eocene

Poleocene/ Eocene

Upper Cretaceous x y X X A

I X X

Jurassic / Lower Cretaceous (including Cenomanian)

Permo/Triassic

Hercynicum

REGIONAL GEOLOGICAL MAP (Partly after Choukroune and Seguret, 1975)

Fig. 1

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Fig. 2

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D. sublodoensis zone NP 14

D. lodoensis zone NP 13

-i—t-

T. orthostylus zone NP 12

! iotf.'

D. binodosus zone NP 11

T. contortus zone NP 10

D. multiradiatus zone NP 9 S o

D. mohleri / H. riedelii zones NP 7 / 8

zone defining species shown with heavy bars

Fig. 4 Stratigraphie distribution of the selected nannoplankton species in the' upper­most Paleocene and Lower Eocene.

PLANKTONIC FORAMINIFERA

(after POSTUMA, 1 9 7 l )

NANNOPLANKTON

(after MARTINI, 197 l )

o c o N » upper part » c o c o 0) «

"*Jj* '!TOP. Globorotalia rex/gracilis

o lower part E o _ * * 'TOP.'C/u'/oçu»mà0/iM mktwayeasis

ö ' lowermost part'

Gr. rex zone

D.

D.

T.

D.

T.

sublodoensis zone

lodoensis zone

orthostytus zone

binodosus zone

contortus zone

NP

NP

NP

NP

NP

14

13

12

11

10

LU

Z

LU

O o LU

DC

LU

O

Fig. 5 Correlations between foraminiferal plankton and nannoplankton zonations in the Lower Eocene.

Fig. 6 Depositional model (plan view) of a submarine fan. IF: Inner Fan, MF: Middle Fan, OF: Outer Fan, FF: Fan Fringe, C: Canyon, FV: Fan-Valley, DC: Distributary Channel, IC: Interchannel Area, S: Suprafan, L: Depositional Lobe, IL: Inter-lobe Area.

INNER FAN MI DOLE FAN

ïaö^jil'iïiwiïiïiïi'j »

$&&#&?&!&&!&

,,,.!|..-.»...J.-.U.i.'-.-.',.!'

r OUTER FAN

-ZJ

tamt*itwfc*a

I.XV/CXIIIi •L

X » i w * f

^*!l**SJ*yf.*l^.^*^|•'* "A,m

IMIIMIIIMaeW*»**»**

ZZ3 • ..Aw.;.'."»"

I l l l> l l l l l l l»M, l I . I 111 III IIII irr 11 1 ill! I

FAN FRINGE

^'•'•'»"•V"''*';'"''!1' i »

UOiÀfeïW

" l , I I I a i i

i " i ' •"> \ , i na=

BASIN PLAIN

Fig. 7 Idealised depositional megasequences in a submarine fan.

w _o "o» _o Q) Q.

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Fig. 8

IO

(O z o < O o

I-o UI (O LL o Û. <

Fig. 9

I Scale is given in meters at the left.

Note differences in scale!

Scales used are i : 2 5 , 1 : 1 0 0 , 1 1 2 0 0 .

2 Groinsize is indicated by relief of the column " S E D I M E N T A R Y S T R U C T U R E S '

The size of intraformational clasts is not taken in account.

— fc «>;c c o o

3 Litholoov l ime-mudstone

marl (often silty) & & & •

s a n d - S siltstone

conglomerate

« • • » intraformational clasts (mostly marl and f ine sandstone)

In "thin bedded" intervals (depending on the scale) a vertical division according to the bulk composition

of the interval is used.

4 Transport directions.

— • Direction of transport (e.g. from f lutes, cros» lamination).

—•— Sense of transport (e.g. from parting l ineation,grooves).

5 Sedimentary structure» (drawn in section)

structureless

| i J l l

ty ix/

dish structures

vertical f luidescape tracks

homogenized by bwturoation

cross lamination (ripple migration)

paralel lamination

parallel lamination with pillar structures

weakly deformed parallel lamination

convolute lamination

tow-angle mega crossbedding

mega cross-bedding (mega-ripple migration)

deformed mega cross-bedding (recumbent foresetting)

6 Additional remarks (in symbols)

s parallel lamination

Ü . cross lamination

_ n _ convolute lamination

**-*- dish structures

is- flutes

gr grooves

obs obstacle scours

£ ^ frondescent casts

pL porting lineation

<£ plant remains

" of loc locally

maximum size ibles

KEY TO DETAIL-SECTIONS

Fig. 10

Fig. 11 Basin plain deposits. Pelagic limestones alternating with red marls. Note bioturbation. Lower Paleocene, Zumaya.

Fig. 12 Basin plain deposits. Decimetre-scale bedded pelagic limestones alternating with grey hemipelagic marls and (rarely) thin turbidites. Upper Paleocene, Playa de San Telmo, Zumaya. (See also detail-section 1).

Author : VVL Drawn . M R S

Dr.nr. 30742 Fig. 11,12

Fig. 13 Basin plain deposits. Thin-bedded distal turbidites alternating with pelagic limestones. Note excellent continuity of bedding. D. binodosus zone, megacycle 1, Playa de San Telmo, Zumaya. (See also bed-thickness-log 1).

Fig. 14 Detail of figure 13. Stratigraphie top is to the left. T: Turbidite, L: Pelagic Limestone. (See also detail-section 2).

Author : VVL Drawn . M R S

Dr.nr. 30743 Fig. 13,14

• - * . - ^ T ^ . ' ^ , " * . ' * * • • -""•*•- ~~ "

Fig. 17 Fan fringe deposits. Proximal turbidites in a matrix of thin-bedded distal turbidites. Bed-thickness distribution is bimodal. Stratigraphie top is to the left. T. orthostylus zone, megacyle 1, tunnel near Punta Arranaiz. (See also detail-section 4 and bed-thickness-log 3)

* ^ <

~'yj*ï-

Fig. 18 Detail of figure 1 7. Proximal turbidite with a concentration of intraformational clasts on top of its massive division. Stratigraphie top is to the left.

Author : VVL Dr.nr. 30745 Drawn : M R S Fig. 17,18

o IxJ

o E

E o

S S r -g O 3 O S CL S O. <D

\ m }> * I

"> T

-) E

<

< oc cc < o N s Li. O 0) h; 35 O 0 . LU O

< LL

LU

O O

Fig. 23

Fig. 24 Post-abandonment channel-fill (C) in middle fan deposits at Bizcarrapia. (See also figure 23 and detail-section 6).

I ' «

Fig. 25 Depositional bank of channel shown in figure 24. Inclined accretionary units (A) rest on a lag of intraformational clasts (U. C is the post-abandonment fill of an older channel. (See also figure 23).

Author : VVL Drawn . M R S

Dr.nr. 30748

Fig. 24,25

F7 2T yi & T. ra"

L : ^ " ' - . . : > - : 3 — • • * - ' ^ „ . - * - • • •_ V w f * - - T i ' -" • • • ' - • • - ^ * ^

Flg. 26 Middle fan deposits at Iratequi, general view on the exposure. Non-channelised concentration of generally thick-bedded turbidites. Note inclined bedding in the top part. D. sublodoensis zone, megacycle 2. (See also detail-section 7).

Fig. 27 Detail of figure 26. The inclined bedding is interpreted as a lateral accretion deposit of a small (few metres deep) migrating channel. Final filling of the channel was by a thick turbidite visible in the upper left corner of the photograph.

Author : VVL Dr.nr. 30749 Drawn . M R S Fig. 26,27

Fig. 28 Fill of a scour in the middle fan deposits at Irategui. Note that the scoured surface was first covered with a mud drape (arrow).

>&s Fig. 29 Middle fan deposits at Irategui. Note pinching-out of turbidite beds and the scoured surfaces

(arrows) covered with a mud drape. Maximum bed-thickness in this photograph is ca. 3 metres.

Author : VVL Dr.nr. 30750 Drawn . M R S Fig. 28,29

\

• ''Muf" J

^slMfcîfr"«*

: '^*s&* Fig- 30 View from SW on Orio. The 1

*„.„,„„ b„„„„ lhe - - - Äta^rcrE o c , n ' , m *p°'»-- ™-«P.? J !

Fig. 31 Basin pia.n deposits. Distal turbidit.« « - - '.

Author : VVL D r a w n : MRS

Dr.nr. 30751

Fig. 30,31

Author : VVL Dr.nr. 30752 Drawn . M R S

Fig. 32,33

w . •' T - « *

Fig. 3 8 1 ) Depositional bank of a migrating channel in middle fan deposits. A is the last accretionary unit and shows a primary dip of ca. 8 degrees. C is the post-abandonment channel f i l l .

2) and 3) Wi th in the accretionary units an up-dip f ining and disappearance of intraformational clasts can be observed.

D. binodosus zone, megacycle 1 , Chimistarri.

Author : VVL Dr.nr. 3 0 7 5 5 Drawn . M R S Fig. 38

-/ t i • ' • • - £ * • . • • . " . - « - V W . , '

^"•^rf.lS-

* f'ïar'ïf*

Fig. 39 Coset of decimetre-scale cross-bedded sets in middle fan deposits at Chimistarri. The foreset laminae are deformed by penecontemporaneous flowage. (See also detail-section 17).

Fig. 40 Turbidites (T) alternating with pelagic limestones (L). The turbidites are very well sorted, do not show grading and largely consist of B-divisions. Note that turbidite-mud is practically absent. Stratigraphie top is to the right. D. binodosus zone, megacycle 1, San Sebastian W, end of boulevard at the foot of Monte Igueldo. (See also detail-section 16).

Author : VVL Drawn . M R S

Dr.nr. 30756

Fig. 39,40

Fig. 41 Flutes, obstacle scours and Granularia burrows on the sole of a turbidite. D. binodosus zone, megacycle 1, San Sebastian E.

Fig. 42 Gastropod trail (Taphrhelmintopsis) and Granularia burrows on the sole of a turbidite. Same location as figure 4 1 .

Author : VVL Drawn . M R S

Dr.nr. 30757 Fig. 41,42

Fig- 43 Parting lineation in the B-division of a turbidite. Same location as figure 4 1 .

Fia 44 Outer fan deposits on the E-side of Ensefiada Murguita. Note the non-channelised body of very thick-bedded turbidites, which is interpreted as a proximal depositional lobe deposit. T. orthostylus zone, megacycle 1.

Author : VVL Drawn . M R S

Dr.nr. 30758 Fig. 43,44

Fig. 45 General view towards E on the upper part of the Pasajes section consisting of middle and outer fan deposits. The ridges in the morphology are formed by suprafan and proximal depositional lobe deposits. The depressions correspond with inter-lobe deposits. The boundary between the D. binodosus and T. orthostylus zones follows the most pronounced depression on this photograph. Megacycle 1.

Fig. 46 Middle fan deposits. Thickening and coarsening-upward megasequence of turbidites. The inclined bedding (arrow) at the top of the megasequence is interpreted as a depositional bank deposit of a migrating channel. The largely vegetation covered depression (C) corresponds with the post-abandonment channel-fill. D. binodosus zone, megacycle 1, lower part of Pasajes section.

Author : VVL Drawn . M R S

Dr.nr. 30759

Fig. 45,46

r * gat*** Fig. 47 Outer fan deposits in the top of the Pasajes section. The thickening and coarsening-upward

megasequence has a rather abrupt base and is interpreted as a proximal depositional lobe deposit. T. orthostylus zone, megacycle 1. (See also detail-section 20 and bed-thickness-log 18).

• v.. •-•*•. • •'*•• *." -." "• *• •

I* * ""»-• - w j j V tijVfisjs-'ji * i ; • ?w

Fig. 48 Dish structures with well developed vertical fluid escape tracks in a conglomeratic sandstone in the megasequence of figure 47.

Author : VVL Dr.nr. 30760 Drawn . M R S Fig. 47,48

Fig. 51 Detail from the relatively thin-bedded succession of figure 49. Crest and leeside of a megaripple formset.

Fig. 52 Middle fan deposits near Punta Turrila. Note the basal scouring (arrow) of the very thick sandstone bed. The relatively thin-bedded part of this succession is similar to the succession at Leznobar. Megacycle 1. (See figures 50 and 51).

Author : VVL Dr.nr. 30762 Drawn . M R S Fig. 51,52

Fig. 59

- 1-1 -

APPENDIX I

NANNOPLANKTON ANALYSES

This appendix presents the results of the nannoplankton

analyses carried out for biostratigraphic correlation purposes.

The results are summarised in the form of distribution charts

(Appendices Ia-g). The following points, concerning the location

of the samples cited in these charts, should be noted:

App. Ia, Zumaya-Guetarla section; Locations of samples indicated

on enclosure 1.

App. lb, Zarauz-Guetarla section; Locations of samples indicated

on enclosure 2.

App. I c , Orio area; Samples taken in motorway-cuts, their

position projected along strike into the Orio section is

indicated on enclosure 3«

App. Id, Orio section; Locations of samples indicated on

enclosure 3>

App. Ie, San Sebastian area; Samples under the heading 'Urgull'

cover the entire succession exposed along the eastern boulevard

at the foot of the Monte Urgull in San Sebastian. Samples under

the heading 'Gros' cover the first 80 metres of the succession

exposed along the eastern extremity of the Playa de Gros,

San Sebastian-East.

App. If, Pasajes section; Locations of samples indicated on

enclosure 4. Samples under the heading 'Lezo' (not indicated on

enclosure 4) were taken in roadside exposures from

Pasajes de San Juan to the entrance of the village of Lezo.

App. Ig, Puenterrabia-Cabo Higuer; Samples cover the succession

from the fishing port of Puenterrabia (~ 20 m below the first

- 1-2 -

megacycle 1 quartz-arenites) up to the highest stratigraphie

levels exposed near the lighthouse of Cabo Higuer.

The samples investigated cover the NP-zones 7/8 to 14.

NP 7/8 and, in particular NP 9, are relatively poorly represented

in the sample material. Sedimentation rates of these largely

pelagic zones were too slow with respect to the sampling density.

The following criteria were applied (largely conform to

Martini 1971) for the zonal determinations as shown in

enclosures 1-4 and 9:

NP 7/8, Di3coaster mohleri and Heliolithus rledelli zones; from

the first occurrence of Discoaster mohleri to the first

occurrence of Discoaster multlradlatus. Owing to the apparent

absence of H. riedelil, NP 7 and NP 8 could not be distinguished

separately.

NP 9, Dlscoaster multiradlatus zone; from the first occurrence of

Dlscoaster multiradiatus to the first occurrence of Trlbrachiatus

bramlettei.

NP 10, Tribrachiatus contortu3 zone; from the first occurrence of

Trlbrachiatus bramlettei to the first occurrence of Trlbrachiatus

orthostylus. The official NP-definition of the top as »the last

occurrence of Trlbrachiatus contortus' is difficult to apply in

view of the usual scarceness of T. contortus. The difference in

practice caused by the alternative top definition is probably

very small as T. contortus and T. orthostylus seem to have little

overlap (see Hay and Mohler 1967 and Hay et al. 1967).

NP 11, Discoaster binodosus zone; from the first occurrence of

Trlbrachiatus orthostylus to the first occurrence of Discoaster

lodoensis.

NP 12, Tribrachiatus orthostylus zone; from the first occurrence

of Discoaster lodoensis to the last occurrence of Tribrachiatus

- 1-3 -

orthostylus. The top definition could cause problems as a result

of reworking. In the present study, however, a well definable

last occurrence of T. orthostylus was observed.

NP 13, Discoaster lodoensis zone; from the last occurrence of

Tribrachiatus orthostylus to the first occurrence of Discoaster

sublodoensis.

NP 14, Discoaster sublodoensis zone; from the first occurrence of

Discoaster sublodoensis to the first occurrence of

Chiphragmalithus alatus. C. alatus has not been recognised in the

sample material.

Intra-Tertiary reworking shows up clearly on most

distribution charts as a 'dilute cloud' of rarely and

discontinuously appearing species on the left side of the chart.

Very few samples (e.g. App. Ic, sample vVl 87) consist

predominantly of reworked species. This is due to the sampling of

turbidite muds instead of hemipelagic muds. The stratigraphie

distribution of selected nannoplankton species is summarised in

Pig. 4.

Z U M A Y A - G U E T A R I A SECTION

• rare

O infrequent

• common

0 abundant

s * S ^ î : « ^

NP 14

EC 42

vVI 174

vVI 173

»VI 172

Km« 749

»VI 171

Krup 1431

»VI 170

«VI 169

EC 39

NP13

»VI 168

EC 46

«VI 166

»VI 159

Krup 1429

»VI 188

»VI 16»

»VI 164

»VI 166

«VI 153

»VI 161

»VI 160

EC 4 9

Krup 1428

»VI 152

»VI 124

»V1122

»VI 123

»VI 137

»VI 121

Np |2 *V"*0

»VI 148

»VI 147

«VI 146

Krup 747

»VI 3 0 4

«VI 303

«VI 162

»VI 301

«VI 300

»VI 299

NPH

»VI 305

«VI 306

«VI 308

»VI 309

Krup 1387

Krup 1388

Krup 1389

NP 9/10 »Vl«13

«VI 412

I . Q Q >-

• • • • • o • • • • •

• • • • • • • • • • • o • • • • • • • • • • • • # • • o • • • • • • • • o • • • • • • • • o o o o • o • •

• •

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o o • • o o

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o

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o aff.

• B H 9J •

Z aff

• • • • • o • • • aff. '

• • • o f f ' • O • • aff.

O • • •

• •

App. Ia

ZARAUZ-GUETARIA SECTION

• rare

O infrequent

• common

0 abundant

V V I 1 8 2

vVI 2 4 4

NP 13 vVI 2 4 3

vVI 2 4 2

vVI 241

wVI 2 4 0

NP 12 vVI**3 vVI 4 4 2

vVI 2 3 0

v V I 4 3 2

NP H VVI431

v V I 4 3 3

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to 18

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App. Ib

ORIO AREA

• rare

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• common

O abundant

'S

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I 8

BEASTEGUI

v V I 9 8

NP \\ WI98

vVI 9 4

vVI91

wVI89

vVI88

vVt87

vVI86

vVI8S

ZARICOLA

vVI39

vVI34

vVI33

NP10 vVI30 vVI28

VVI4S

vVI 43

VVI41

N.of USURBIL

Krup 1611

vVI 104

vVI 246

vVI 103

•

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vVI99

N P 7 / 8 WI98

vVI97

O O o

App. Ie

ORIO SECTION

• rare

O infrequent

• common

0 abundant

s

vVI 3 4 8

vVI 347

vVI 3 4 6

VV I345

V V I 1 7 8

NP !2 »VI 177

vVI 176

vVI 175

Krup 1170

EC 60

vVI 2 8 3

c:

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vVI 2 8 2

VV I281

WVI314

v V I 3 1 3

v V I 3 1 2

N P H WI311

vVI 293

vVI 294

vVf 296

vVI 278

vVI 2 7 7

O O

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aff.

• • •

O O Krup 1172

NP 10 KruP 1359

Krup 13S8

App. ld

SAN SEBASTIAN AREA

• rare

O infrequent

• common

0 abundant

5 c 1« I 3 €

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URGULL

vVI 273

vVI 272

VVI271

vVI 269

vVI 268

• VVI267

NP 11 G«°» v VI 410

VVI409

VVI408

v VI407

vVI406

VVI408

O O O O • O • • • • O • O O O O o o • •• O • • O

A pp. I e

PASAJES SECTION

• rare

O infrequent

• common

0 abundant

v V I 6 8

v V I 5 5

vV IB4

wVI52

v V I 4 8

v V I 4 7 NP 12

v V I 6 2

vVI 118

vVI 120

WVI117

vVI 116

vVI 115

WVI114

vVI 113

VV I112

vVI 111

WVI110

N P I I vvi 109

vVI 108

vVI 107

vVI 106

vVI 106

Krup 1133

NP 10 Krup 1129

Krup 1131

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App.If

FUENTERRABIA-CABO HIGUER

• rare

0 infrequent

# common

O abundant

e a

a •ç

a &

o -

5 5 S O <J u

I I

3 * "5 2 <0 (O

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u

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c «1

5

Q O U .0 Q ^

3 •g •ft •§ O

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3 .C

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5

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- » Q. O •> t l

2 I 3 Vi

VVI2B9

v V I 2 5 6

vVI 194

Knip 1152

Knip 1397

N P H Knip 1388

Knip 1399

Knip 1400

Knip 1401

Knip 1402

Knip 1149

O O •

O

o

o • o o o o o •

o o o o o

o o o o

App. I g