2. site 44

2. SITE 44

The Shipboard Scientific Party1

MAIN RESULTS

Penetrated two thirds of sedimentary cover-carbonateooze with chert beds or lenses; recovered cores throughLower Oligocene, Upper Eocene, and most of MiddleEocene; established age and character of acoustic re-flector as a Mid-Eocene chert.

BACKGROUND

Site 44 was chosen to contribute to the knowledge ofthe Mid-Pacific Mountains and thereby to the generalhistory of the mid-Pacific area. These mountains are ofvolcanic material ranging in age from at least as old asMiddle Cretaceous to Recent (Hamilton, 1956; Menard,1964). Some mountains are peaked seamounts, othersare flat-topped guyots. The Horizon feature, commonlycalled a guyot, is really neither, being a narrow ridgetrending NE-SW for a distance of 170 miles with a flat-tish top that is 10 to 20 miles wide in the area drilled;it has sharply defined shoulders at depths of 1850 to2050 meters (Figures 1,2). Gentle hills along the ridgeaxis rise to depths of about 1400 meters in the regionof Site 44. Bottom soundings in area of Site 44 aregiven in Figure 4. Dredging near the southwestern endyielded Eocene limestones, partly silicified and phos-phatized, and recovered olivine basalt from depths ofabout 1800 meters (Hamilton, 1956). A dredge haul by

1B. C. Heezen, Lamont-Doherty Geological Observatory; A. G.Fischer, Princeton University; R. E. Boyce, Scripps Institutionof Oceanography; D. Bukry, U.S.G.S. La Jolla; R. G. Douglas,Case Western Reserve University; R. E. Garrison, Universityof California, Santa Cruz; S. A. Kling, Cities Service Oil Com-pany ;V. Krasheninnikov, Academy of Sciences of theU.S.S.R.;A. P. Lisitzin, Academy of Sciences of the U.S.S.R.; A. C.Pimm, Scripps Institution of Oceanography.

Newman (personal communication) recovered Eocenelimestone and chert from the northern shoulder.

A site survey by the Argo is discussed in Chapter 19.It showed the presence of a sedimentary cap, thickestunder the hills along the axis of the ridge (up to 100meters thick). A prominent reflector lies at a maximumdepth of about 60 meters and outcrops locally alongthe northern edge where it forms a small terrace. Evi-dence from dredging tentatively suggested that this isan Eocene chert bed. The sedimentary cap is underlainby an acoustically distinct, opaque mass largely devoidof coherent reflections with seismic velocities of 3 to3.5 km/sec; this was interpreted by Shor as either vol-canics or limestone. This material seems to crop out inplaces along the northern'edge of the ridge, and formsin such places a terrace below that of the sedimentaryreflector.

The magnetic survey (Figures 2,3) revealed a prominentpattern of anomalies, roughly parallel to the topography,with major lows corresponding to the flanks of theridge.

Bottom photographs showed rippled sand on the crest,and a rocky bottom with patches of sand along thenorthern edge.

Objectives

The specific objectives, in order of importance, were(1) to sample the oldest sediments and the underlyingmaterial (presumably basalt), in order to determine theage of the mountain and the date of its initial sub-mergence; and (2) to sample the sedimentary sequence,in order to shed some light on the history of submer-gence, and to provide biostratigraphic and sedimen-tologic data.

Only a limited amount of time was judged allowablefor this second priority site.

Strategy

Two drill sites were considered: the crest of the featureor its extreme northern shoulder.

A hole in the crest would provide suitable soft sedimentfor spudding in, and would allow sampling of the upperpart of the sedimentary section. The risk in such a holewas posed by the reflector, interpreted as Eocene chert,which might prove to be impenetrable.

17

Figure 1. Argo profile at Site 44.

The northern shoulder appeared to offer areas notunderlain by this chert, but seemingly underlain by themassive opaque material below the sedimentary cap-material which might be either Cretaceous reef lime-stone (by comparison with some of the guyots) orbasalt (more likely, to judge from the dredging). Therisk here lay in not being able to spud in. The hardrocky appearance of the bottom photographs was notencouraging.

Therefore, the first alternative—a crest location—waschosen. With only two massively set diamond bits onboard, a lightly set diamond bit was run. And it wasdecided to make this a one-hole site barring unusualgeological discoveries, even if the reflector might proveimpenetrable.

OPERATIONS

Site 44 was occupied at 2245 hours June 13. The holewas drilled to 40 meters, and mainly cored beyond this

to a total depth of 76 meters (Table 1). Chert encoun-tered at 62 meters damaged the bit, and that encoun-tered at 76 meters proved impenetrable. On starting outof the hole, the bottom assembly parted at the top ofthe sixth drill collar, bending the pin. Failure may haveresulted either from insufficient torque in making upthe string, or from stresses induced by encounteringchert at such shallow depth below the sea floor. Thesediment recovered was so water-saturated that thecore sections were largely left unsplit.

The site was abandoned at 0100 hours on June 15.

NATURE OF THE SEDIMENTS

The 24 meters of sediment recovered at this site con-sist of yellowish-white nannoplankton-foraminiferalchalk ooze and small amounts of chert. At the time ofrecovery the sediment varied from a water-rich slurry topasty, incoherent material; consequently, none of the

18

TAU

1000

1500

2000

2500

16 18 20HRS

\ -

GAMMAS

34500

34400

Figure 2. Bathymetric and magnetic profile at Site 44.

19

169°W

19°30'N

19°20'N

19°10'N

DEPTH CONTOURS,FATHOMS

MAGNETIC COUNTOURSGAMMAS

'ACOUSTIC PROFILES,SCAN III

X DRILL SITE 44

Figure 3. Challenger bathymetric and magnetic contour map at Site 44.

20

169°

19°

•S T-. c*

19° N

169°W

Figure 4. Bottom soundings in area of Site 44.

21

TABLE 1

Summary of Coring at Site 44

Core No.

44.0-1

44.0-2

44.0-3

44.0-4

44.0-5

Interval Cored(Below Mudline)

(ft)

131-161

161-191

191-206

217-245

245-248

(m)

39.9-49.1

49.1-58.2

58.2-62.8

66.1-74.7

74.7-75.6

Recovery

(ft)

17

30

15

28

3

(m)

5.2

9.1

4.6

8.5

0.9

Water depth: 1478.3 meters (4850 feet)

core sections were split open, and the sections weresampled only at the ends.

The chalk ooze at this site is very uniform (Chapter 38).Nannofossils (coccoliths, discoasters and Thoracos-phaera) compose 80 per cent to 90 per cent ofthis sediment, and foraminifera, chiefly planktonics,constitute most of the remainder. Small amounts ofanhedral carbonate crystals, in the 5 to 20 micron sizerange, occur throughout the sediment recovered, but itis uncertain whether this material is of authigenic originor represents broken fragments of molluscan or for-aminiferal shells.

The only other lithology noted is chert which is usuallybrown, fine-grained and vitreous. Chert first appears assmall angular fragments in Core 1 at a depth of 41meters below mudline; this may represent penetrationof a thin chert stringer or a small nodule. Below thispoint most samples contain small amounts of chertwhich could likewise represent thin stringers, or alter-natively, might be cavings from uphole.

The main chert body encountered occurs at 63 metersbelow mudline, at the base of Core 3, where severalangular fragments of brown chert were recovered in thecore catcher. These fragments have thin white crusts ofhard, partially silicified limestone on one side. Theyresemble pieces of the nodular cherts seen in theBritish and other chalks. Within the outer crusts aretests of foraminifera that have been replaced by micro-crystalline or chalcedonic quartz, but the test outlinesremain distinct and sharply bounded against the sur-rounding fine-grained matrix of microcrystalline quartzand calcite (Chapter 38). This crust grades into themain body of the chert which is very fine-grained,uniform microcrystalline quartz containing only scat-tered and very faint outlines of silicified foraminifera.

Similar chert fragments were recovered from the corecatcher of Core 5, at a subbottom depth of 76 meters.These may be from another chert body, or they mayrepresent cavings from the body at 63 meters.

The chert recovered at this site appears to be of second-ary origin, formed through local replacement of chalkooze. Noteworthy is the fact that no siliceous micro-fossils were noted either in the cherts themselves or inthe associated chalk oozes. Possibly their total obliter-ation by diagenetic solution supplied the silica for thechert bodies.

PHYSICAL PROPERTIES

Methods used in the physical property determinations,the effects of coring disturbance, and a general discus-sion are given in the Appendix.

During drilling operations at Site 44 the sediments weredisturbed and thus all physical property measurementsmay not represent in situ values.

Natural Gamma Radiation

Twenty-eight meters of Eocene-Oligocene white foram-iniferal-nannoplankton chalk ooze were cored within40 to 76 meters beneath the sediment surface fromHole 44.0. Emissions of natural gamma radiation variedfrom 0 to 250 counts per 7.6-centimeters (3 inches)core segment during a 1.25 minute scanning period,with an average of 100. Such a low gamma count istypical for nannoplankton chalk ooze which containsvery little clay, zeolite, or other radionuclide-bearingsubstances. There is no significant variation in radia-tion with depth in this hole (see hole and core plots).

Porosity, Wet-Bulk and Water Content

Porosities of the Eocene-Oligocene white foraminiferalnannoplankton chalk ooze recovered within 40 to 76meters in Hole 44.0 spanned from 48 to 90 per centwith a typical value of about 58 per cent. Wet-bulkdensities ranged from 1.23 to 1.87 g/cc with a mode ofabout 1.76 g/cc. These values do not exhibit a sys-tematic variation with depth (see hole and core plots).The maximum porosity and minimum wet-bulk densityvalues probably represent artifically disturbed sediment.Individual samples were not taken, thus water contentwas not measured.

Sound Velocity

Sediment sound velocities through 23 meters of Eocenewhite nannoplankton ooze recovered at a depth of 49to 75 meters from Hole 44.0 ranged from 1.46 to 1.61km/sec with a norm of 1.57 km/sec. No systematicvariation with depth is apparent and the statisticalpopulation is too small to make correlations with otherphysical properties with a high degree of confidence.

22

However, core averages of sound velocity and wet-bulkdensity have an apparent indirect variation (see holeand core plots). See porosity section for a discussionof this relationship.

````````````````````````

As the cores were too soft to split, no penetrometermeasurements were made.

Thermal Conductivity

Heat conductivity values in the Eocene white forami-niferal-nannoplankton ooze from 50 to 75 meters atHole 44.0 were 3.62 and 3.61 × I0"3 cal^C"1 cm'1 sec'1.

CONCLUSIONS

The sediments on this mountain are, as expected,mainly foraminiferal-nannoplankton oozes. While theNeogene was penetrated without recovery of samples,a good sequence of cores was obtained through theLower Oligocene, the Upper Eocene, and most of the

Middle Eocene. The sediment is so soft and watery thatit was badly disturbed inside the core barrel.

Traces of brown chert were encountered in the Oligo-cene and Upper Eocene, and more massive vitreousbrown layers in the Middle Eocene; the latter may beconfidently identified with the prominent acousticreflecting horizon shown on the profiles, and termin-ated the drilling here.

No new light was shed on the sediments below thisreflector, nor on the composition of the underlying,"opaque" material. It seems likely that Eocene sedi-ments here rest on basalt.

REFERENCES

Hamilton, E. L., 1956. Sunken islands of the mid-Pacific mountains. Geol. Soc. Amer. Mem. 64, 97 p.

Menard, H. W., 1964. Marine geology of the Pacific.New York (McGraw-Hill).

23

HOLE 44.0

100

LITHOLOGIC DESCRIPTION

NANNOPLANKTON CHALK OOZE, very pale orange, with rare angular, darkchert fragments

NANNOPLANKTON CHALK OOZE, white

NANNOPLANKTON CHALK OOZE, white, with common chert fragments

NANNOPLANKTON CHALK OOZE, white

NANNOPLANKTON CHALK OOZE and CHERT, Core Catcher sample only

AGE

SERIES-SUBSERIES

EARLY OLIGOCENE

LATE EOCENE

MIDDLE EOCENE

MIDDLE EOCENE

Figure 5. Summary oflithology in Hole 44.0.

24

HOLE: 44.0

DEPTH NATURAL GAMMA WET-BULK WATER CONTENT SOUND THERMAL PENETROMETERIN RADIATION DENSITY AND VELOCITY CONDUCTIVITY

HOLE POROSITY

COUNTS/7.6cm/1.25n

8 0 -

vm-3 vm-1X10 Λ I U mm

9/cc % wt % vol km/sec cal/(°C cm seel c p

5000 1.4 1.8 2.2 20 40 60 80 100 1.6 1.8 2.0 2.2 2.0 3.0 4.0 0 100 200 300

i i r I I I T

*O = LABORATORY- ATMOSPHERIC BACKGROUND COUNT.

Figure 6. Summary of physical properties in Hole 44.0.

25

erLLJCD

COLu

CL

UJ

LEG 6

CORE i

H O L E 44.0

D E P T H 39.9-49.1 m

LU < Zo o

O LITHOLOGIC DESCRIPTION CO CO a

LUO

O

> -

- I

-2

-3

-4

5

-6

-8

-9

• I I

-I2

4 J 1 3

-I4

—: -15

: • i 6

5:-i7: i8

6 " :20

;-22

7-23

24

cc

Core not s p l i t as sediment very watery

Angular dark chert fragments - rare

NANNO CHALK OOZEVery pale orange (10YR 8/2)Nanno DForam C

59 37 94

94

56

59

39

36

93

91

Figure 7. Summary oflithology in Hole 44.0 Core 1.

26

CORE: 44.0-1


CORE POROSITY

COUNTS/7,6cm/1.25min % wt % vol

×10•

km/sec cal/(°C en

5000 1.4 1.8 2.2 20 40 60 80 100 1.6 1.8 2.0 2.2 2.0 3.0 4.0 0 100 200 300

2 -

i i i i i i r i i i I i i r i i i I r i i i i I i i

•O = LABORATORY- ATMOSPHERIC BACKGROUND COUNT.

Figure 8. Summary of physical properties in Hole 44.0 Core 1.

27

erLUCD

Lu

ON

LJ_ l<uCO

δo

LUU0

UJ

<CO

§ 1α: to

LEGCORE *

HOLEDEPTH

44.0

49.1 58.2 m

LITHOLOGIC DESCRIPTION CO CJ>o cc

o

1

803

-2

h' 3

-4

5

J-6

3 : •ic

4 : 1 3

-14

5:16

-17

: • i 8

6" :20

;•22

7-23

-24

-25

-26

-27

28

29

cc

Core not split as sediment very watery

NANNO CHALK OOZEWhite (2.5YR 8/2)Nanno DForam RPellets of non-skeletal c a l c i t e RChert fragments R (Section 2)

Trace of glauconite

63 36

61 38

59 40

58 41

60 39

63 37

94

95

91

89

92

9197


28

CORE: 44.0-2


CORE POROSITY

COUNTS/7.6cm/1.25min I wt % volX10° X10''mrr

cal/(°C cm sec)

5000 1.4 1.8 2.2 20 40 60 80 100 1.6 1.8 2.0 2.2 2.0 3.0 4.0 0 100 200 300

2-

i i i i i I I I I I I I i I i I I i I I | I r i I I I I l l

I I 1 I I

*O = LABORATORY-ATMOSPHERIC BACKGROUND COUNT.


29

erUJGD

LU

LU

0_

<

LEGCORE

44.0HOLED E P T H 58.2-62.8 m

LU <

O r-N E

3oLUCO LITHOLOGIC DESCRIPTION c^ CO

oo

-6

2-i-8

-9

- - I0

II

12

13

14

5-

20

--2I

22

7-21

24

CC

Core not s p l i t as sediment very watery;strongly deformed by d r i l l ing .

Few dark grains of Mn/fe oxide and chertat top of Section 1

NANNO CHALK OOZEWhite (2.5YR 8/2)Nanno DForam RPellets of non-skeletal ca l c i t e R

Several small dark chert fragments

Core CatcherPieces of brown chert, vitreouswith hard limestone crust; chertf inely crystall ine quartz; mosaic;no siliceous microfossils; tracesof foram

65 34

73 27

59 40

54 38

22 45 33

97

94

96

84

85

Figure 11. Summary oflithology Hole 44.0 Core 3.

30

CORE: 44.0-3DEPTH NATURAL GAMMA WET-BULK WATER CONTENT SOUND THERMAL PENETROMETER

IN RADIATION DENSITY AND VELOCITY CONDUCTIVITYCORE POROSITY

µ COUNTS/7.6cm/1.25min g/cc % wt % vol

M <n o 5000 1,4 1.8 2.Z 20 40 60 80 100

X10J X10"cal/l°C cm seel

2.0 2.2 20 3.0 4.0 0 100 200 300

2 -

5 -

i i i r i i I r i i

*O - LABORATORY-ATMOSPHERIC BACKGROUND COUNT.


31

enLUαo

LU

Q-

LU

LEGCORE 4

HOLE 44.0

DEPTH βe.1-74.7 m

AGE

LU

LU

OLU

LU

QQ

as:

UJINO

Z

1ilI i

•Q + *CO

CO 0505 K

O O

-&+*N 05Oft;

<j

OCO

1-

2-

0

4:

5:

6:•

7-

-

cx>

1 l•

l 1

-

-1

-2

-3

-4

cD

-6

- 7

-8

-9

I Λ

-IU

-II

-19

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

25

26

27

28

29

o

SECT

I11

2

3

4

5

6

cc

OGY

LITH

OL

" " *

', \ \ *

" * *' ' 'T <

* *

, , ,

* * ' , *

* ' '

' ' *

* *

w n "

* * * ' '

, ' , " ,

, ' , ' ,

' * '

(

1—

PA

LEO

SM

EA

R

*

*

*

*

*

*

LITHOLOGIC DESCRIPTIONCore not

NANNOWhiteNannoForam

s p l i t as sediment very watery

CHALK OOZE(2.5YR 8/2)DC

Pellets (both calcareous and

AL . 1 1

ShellChert

non-calcareous) R

RR

%Sα

nd

4

2

3

1

13

7

CO

57

56

61

61

52

57

>-o

39

42

36

38

35

36

o s3

91

95

95

94

93

96

o


32

CORE: 44.0-4

DEPTH NATURAL GAMMAIN RADIATION

CORE

WET-BULK WATER CONTENT SOUND THERMAL PENETROMETERDENSITY AND VELOCITY CONDUCTIVITY

POROSITY

COUNTS/7.6cm/1.25min g/cc % wt % vol km/sec cal/(°C cm sec)CP

1.8 2.2 20 40 60 80 100 1.6 1.8 2.0 2.2 2.0 3.0 4.0 0 100 200 300

i i i i i i i i i i i i n i i i i i i i i iI

*O = LABORATORY-ATMOSPHERIC BACKGROUND COUNT.


33

Lu

SE

LU_ l<OCO

erLUOG

CO

> -

COLU

2 CO

LEGCORE

HOLEDEPTH

44.0

74.7-75.6 m

LITHOLOGIC DESCRIPTION

O Os

Ott;

-2

-3

-4

5

-6

-9

y -

4 :

5:

-12

•-13

-14

-15

1-19

--20

I -21: -22

-23

24

cc

Core CatcherNANNO CHALK OOZE and CHERTChert - angular pieces up to 6 cmacross; banded; occasionally withchalky crust; contain few foram -probably si 1 i c i f i ed limestone

97


34

LEGCORE '

44.0HOLEDEPTH 399491

FORAMINIFERA

Assemblages of foraminifers

throughout the core are

rather similar and belong to

the Globigerina ampliapertura

Zone (the lower part of

Oligocene).

They include numerous

Globigerina ampliapertura, G.

selliii G. pseudovenezuelana,

G. praebulloides3 G. offiaina-

lisy G. angustiurribilicata> G.

tripartita, G. tapuriensis,

G. ouachitaensis> Globorotalia

postaretacea3 Cassigerinella

ahipolensis, Pseudohastigerina

barbadoensis, Chiloguembelina

aubensis together with rare

Globigerina aiperoensis and

G. gortanii.

NANNOPLANKTON

lannofossil assemblages

throughout the core are

similar and represent the

ower Oligocene lower

Sphenolithus predistentus

Zone. The spines of S.

predistentus are very long

and abundant in this core and

appear as long rods when

broken from their base.

RADIOLARIA

None.

Figure 16. Summary of biostratigraphy in Hole 44.0 Core 1.

35

LEGCORE

HOLE " °DEPTH 491582

FORAMINIFERAPlanktonic Foraminifera

indicate the Upper Eocene age

of sediments (the Globigevina

oorpulenta Zone).

Throughout the core are

developed Globigerina

oorpulenta, G. pseudo-

venesuelana, Globigerapsis

tropiaalis, Hantkenina

suprasuturalis3 Cribro-

hantkenina inflata,

Pseudohastigerina miara.

The lower part of the core

(sections 6 - 4) with

Globigerapsis semi-involuta

and G. index belongs to the

G. semi-involuta Subzone; the

upper part (sections 3-1)

with Globorotalia cervo-

azulensis, Globigerina

gortanii and rare G.

ampliapertura and G.

offiainalis - to the

Globorotalia aerro-

azulensis Subzone.

NANNOPLANKTONAssemblages of the upper

Eocene Discoaster

barbadiensis Zone are present

throughout the core. The

surficial character of the

discoasters is obscured by

excess calcification. Rare

specimens of middle Eocene

species such as Chiasmolithus

grandis and Thoraaosphaera

prolata occur in the lower

part of the core.

RADIOLARIANone.

Figure 17. Summary of bio stratigraphy in Hole 44.0 Core 2.

36

LEGCORE

HOLE ""DEPTH 2628

FORAMINIFERA

Planktonic foraminifers

determine the age of sediments

as the upper part of the

Middle Eocene.

Sections 1 - 4 belong to the

Trunoorotaloides Zone and are

characterized by T. rohri,

Aaarinina rugosoaouleata.

Hantkenina longispina,

Pseudohastigerina miora,

Globigerina praebulloides, G.

inaretaoeat G. turβmenioa, G.

azerbaidjaniaa^ G.

pseudovenezuelana, Globi-

gevinita howei, Globorotalia

aentvalis and rare G.

spinulosa and G. venzi.

Sections 5 - 6 with

Globorotalia armenioa, G.

aentralis, G. spinulosa3 G.

renzi, Hantkenina alabamensis,

Trunaorotaloides topilensis,

T. rohri, Globiger>apsis

kugleri correspond to the

Orbulinoides beckmanni Zone.

NANNOPLANKTON

Only upper middle Eocene

assemblages of the

Retioulofenestra umbilica

Zone are present. Heavily

calcified Disaoaster

barbadiensis and D. tani

nodifera dominate the

discoasters; D. tani tani is

rare and small.

RADIOLARIA

None.

Figure 18. Summary of bio stratigraphy in Hole 44.0 Core 3.

37

LEGCORE

HOLE «°D E P T H 66.174.5

FORAMINIFERA

Throughout the core chalk

oozes contain abundant

foraminifers of the

Orbulinoides beckmanni Zone

(upper Middle Eocene), 0.

beokmanni, Hantkenina

alabamensis, Glogorotalia

oentralis, G. armenioa, G.

venzi, G. spinulosa3 G.

golivariana, Globigerinatheea

barrij Globigerapsis index.

G. kuglevi, Trunaorotaloides

topilensisj T. Tohri3

Globigerina pseudoeaaena

aompacta> G. fz>ontoscij

Globiger>inita eahinata, and

infrequent Globorotalia

tehneri and Aβarinina

votundimarginata near the

base of the core.

NANNOPLANKTON

Upper middle Eocene

assemblages of the

Retioulofenestva vmbilioa

Zone are present throughout

the core. Species present

include Chiasmolithus gx>andis

and Thoraeosphaer>a pvolata.

RADIOLARIA

None.

Figure 19. Summary of biostratigraphy in Hole 44.0 Core 4.

38

LEGCORE

HOLE ««D E P T H 74.7-75.6 m

FORAMINIFERA NANNOPLANKTON RADIOLARIA

Core 5 comtains mixture of

abundant Pliocene - Lower

Pleistocene Foraminifer with

rare specimens of

Ovbulinoides beakmanni,

Hantkenina alabamensis,

Globorotalia aentr>alis,

Globigevapsis kuglevi,

Trunaor>otálo•ides topilensis

(the Orbulinoides beakmanni

Zone of Middle Eocene), as a

result of contamination of

microfossils in the process

of drilling.

Upper middle Eocene

assemblages of the

Retioulofenestra wnbiliaa

Zone are present in both top

and core-catcher samples.

Species present include

Bramletteius serraouloides,

Thor>acosphaer>a prolata, and

Triquetrorhabdulus inoevsus.

None.

Figure 20. Summary ofbio stratigraphy in Hole 44.0 Core 5.

39

2. site 44

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