The Shipboard Scientific Party - Deep Sea Drilling · Subunit lc is a thin (13 m) red and reddish-brown semilithified detrital clay. Most of the sediment is mont-morillonite (57%)

10. SITE 257

The Shipboard Scientific Party1

SITE DATA

Locality: Southeastern Wharton Basin, northeast of Nat-uraliste Plateau

Position:lat3O°59.16'Slong 108°20.99'E

Dates Occupied: 20-23 October 1972Water Depth: 5278 meters

Penetration: 326.5 metersNumber of Cores: 17

Oldest Datable Sediment Cored:Depth (subbottom): 247.0-256.5 meters (Core 9)Nature: Brown detrital clayAge: Mid Albian

Basement:Depth encountered (subbottom): 262 metersNature: Olivine basaltPenetration: 64.5 meters

Principal Results: The basalt is overlain by 262 meters of mid Albian to Recent brown detrital clay. There is a section of graycoccolith clay from 199 to 247 meters subbottom. Contact with the basalt appears depositional. There is a probabledisconformity between Cretaceous and Tertiary or Recent sediments, but this cannot be proven due to the unfossiliferous natureof the sediments.

BACKGROUND AND OBJECTIVES

Site 257 is located in the southeastern Wharton Basin,northeast of the Naturaliste Plateau in 5278 meters ofwater (Figure 1). The Wharton Basin was formed byeither north-south or east-west spreading soon after thebreakup of Gondwanaland. In the case of eitherspreading direction, the oldest sea floor in the basin, andpossibly in the Indian Ocean, would be adjacent to thewestern edge of Australia, and basement age determina-

1 Thomas A. Davies, Scripps Institution of Oceanography, La Jolla,California; Bruce P. Luyendyk, Woods Hole Oceanographic Institu-tion, Woods Hole, Massachusetts (now at University of California atSanta Barbara); Kelvin S. Rodolfo, University of Illinois at ChicagoCircle, Chicago, Illinois; D. R. C. Kempe, British Museum (NaturalHistory), London, United Kingdom; Barrie C. McKelvey, TheUniversity of New England, Armidale, N. S. W., Australia; RosanneD. Leidy, Harvard University, Cambridge, Massachusetts; George J.Horvath, The Florida State University, Tallahassee, Florida (now atState of Florida Department of Pollution Control, Tallahassee,Florida); Roy D. Hyndman, Dalhousie University, Halifax, NovaScotia, Canada; Hans R. Thierstein, Geologisches Institut, Zurich,Switzerland; (now at Lamont-Doherty Geological Observatory,Palisades, New York); Rene C. Herb, University of Berne, Berne,Switzerland; Esteban Boltovskoy, Museo Argentino de CienciasNaturales, Buenos Aires, Argentina; Patricia Doyle, Scripps Institu-tion of Oceanography, La Jolla, California.

tion at Site 257 should give the date of the initiation ofthe breakup. Site 257, in conjunction with otherWharton Basin sites, was planned to help determine theage gradient in the basin. It was expected that if thegradient were north-south, then Site 257 would be olderthan Sites 212 and 256 in some reasonable proportion. Ifthe gradient were east-west, then Site 257 would bemuch older; for instance, four or five times the agedifference between Sites 212 and 256.

The seismic record approaching the site (Figure 2)shows abyssal hill topography covered by between 0.3and 0.6 sec DT of transparent sediments. The acousticbasement has a relief of about 0.3 sec. At the site about0.335 sec DT of sediment is present. A very weakinternal reflector can be seen near 0.15 sec DT which isnot conformable to the sediment surface or the acousticbasement. There are no significant topographic featuresseen in the vicinity of Site 257.

OPERATIONSGlomar Challenger approached Site 257 from the

northwest. After turning north onto the same track asthe Conrad-l 1 profile upon which the site had originallybeen selected, we followed our now well-establishedprocedure of passing over the site, identifying it, thenmaking a Williamson turn to come up on a reciprocalcourse, dropping the beacon while underway on the

327

BATHYMETRY

OF THE

EASTERN INDIAN OCEAN

Figure 1. Base chart and locality for Site 257. (Compiled and contoured by R. Markl, Lamont-Doherty Geological Observatory.)

SITE 257

SITE 257

— 6 SECDT

v •— 7

— 8

183-1 003

Figure 2. Seismic reflection profile approaching Site 257, taken from D/V Glomar Challenger.

134-*η

second crossing of the site. The beacon was dropped,while underway at 5 knots, at 1533, 20 October, in 5278meters of water. We then retrieved the underway surveygear and taking up position over the beacon,commenced lowering pipe.

The bottom was reached soon after midnight, and acore was taken at the mudline. This core was on deck at0236, 21 October. Drilling and intermittent coring thenproceeded uneventfully until we reached a subbottomdepth of 237.5 meters where we commenced continuouscoring. Basement was reached at 262 meters (Core 10)and we cut seven further cores into the basement beforeabandoning the site. Table 1 gives the vital statistics forcores cut at Site 257.

Three lowerings of the downhole temperatureinstrument were made immediately after cutting Cores5, 6, and 7. The instrument was operated in the locked-in mode, and no attempt was made to cut core at thesame time as a temperature measurement was made.This was done to try to avoid the problems encounteredat Site 256. The first lowering was successful. On thesecond lowering the tip of the stinger was bent through aright angle, and on the third lowering the stinger wasbent and broken off completely. It is suspected that thetool was hanging up in the bottom hole assembly some-where since the sediment we were sampling was quitesoft.

After the decision was made to abandon the site, thesidewall sampling tool was dropped in order to test theshear-pin assembly. No attempt was made to retrieve

the tool; it was simply left in the core barrel until thebottom hole assembly was recovered. The bit wasbrought onboard soon after 2300, 23 October when itwas seen that although the shear-pin assembly on thesidewall sampler had operated correctly, the pullnecessary to shear the pin had seriously damaged thetool and clearly a stronger design was required. Thesampler was cut free with a torch and the tools laiddown and secured. We got underway for Site 258 at2356, 23 October. A postsite survey was not considerednecessary.

LITHOLOGY

Total penetration into the sea floor at Site 257 was326 meters: 262 meters through sediment and 65 metersthrough basalt. Slightly less than half of the hole wascored, although coring was continuous below 237meters and 44 meters of sediment and 32 meters ofbasalt was recovered.

Two major lithologic units were distinguished in thematerial obtained: (1) detrital clay and (2) olivine basalt.

Uπitl

Subunit la is the major, 185-meter-thick portion ofthis unit. It is a dark brown, soft (stiff in Cores 5 and 6)zeolite-bearing and zeolite-rich detrital clay. Thepredominant clay mineral is montmorillonite, withlesser amounts of mica/illite and kaolinite. Core 3(between 48 and 57 m) is the only section containing nomore than rare traces of clinoptilolite which occurs in

329

SITE 257

TABLE 1Cores Cut at Site 257

Core

12

Drilled3

Drilled4

Drilled5

Drilled21

6Drilleda

7Drilleda

89

1011121314151617

Total

Date(Oct.1972)

2121

21

21

21

21

21

21222222222222232323

Time

02360411

0536

0714

0906

1228

1612

2135002002550655101615162155034307151138

DepthDrill Floor

(m)

5288.0-5297.55297.5-5307.05307.0-5335.55335.5-5345.05345.0-5373.55373.5-5383.05383.0-5411.55411.5-5421.05421.0-5449.55449.5-5459.05459.0-5487.55487.5-5497.05497.0-5525.55525.5-5535.05535.0-5544.55544.5-5551.05551.0-5560.55560.5-5570.05570.0-5578.05578.0-5586.05586.0-5595.55595.5-5605.05605.0-5614.5

aHeat flow measurement in this interval.

Unit/Subunit Core

Depth BelowSea Floor

(m)

0-9.59.5-19.0

47.5-57.0

85.5-95.0

123.5-133.0

161.5-171.0

199.5-209.0

237.5-247.0247.0-256.5256.5-263.0263.0-272.5272.5-282.0282.0-290.0290.0-298.0298.0-307.5307.5-317.0317.0-326.5

TABLE 2

Cored(m)

9.59.5

9.5

9.5

9.5

9.5

9.5

9.59.56.59.59.58.08.09.59.59.5

155.5

Lithologic Summary, Site 257

Depth BelowSea Floor Thickness

(m) (m) Description

LengthRecovered

(m)

9.56.0

4.0

4.8

3.1

1.3

8.3

2.43.61.53.34.05.06.03.54.06.4

76.7

Recovery(%)

10063

42

51

33

14

87

25382335426375374267

49

1 1-10 0-262.0 262 Dark brown detrital clay;reddish-brown-gray coccolithdetrital clay and clayey cocco-lith ooze.

la

lb

1-6

7-9

0-185.0

185.0-249.0

185

64

Dark reddish-brown detritalclay.

Reddish-brown-εray coccolidetrital clay, minor clayeycoccolith ooze and clayeycoccolith chalk

lc 9-10 249.0-262.0

2 10-17 262.0-326.5

13 Stiff and semilithified lamin-ated reddish-brown detritalclay.

64.5 Vesicular porphyritic olivinebasalt.

maximal quantities in Cores 4, 5, and 6. The dark browncolor of the sediment is due to the presence of clay-sizedtranslucent and opaque ferruginous aggregates whichcomprise an average of 2% of the material. Fish debris ispresent throughout the subunit in trace amounts,although a maximum concentration of 5% was observedin Core 1. Coccoliths are virtually absent. Siliceousfossils comprise 2%-10% of Core 1, but are absent in therest of the subunit.

An interesting feature of Subunit la is the occurrenceof black manganese micronodules in Core 3, at around50 meters. It has already been noted that theconcentration of zeolites is minimal in this same portionof the subunit. Similar manganese micronodulesappeared at about the same depth in sediments ofidentical lithology at Site 256.

In Cores 4 and 5 partially silicified mudstone, possiblyincipient chert, occurs. These cores are rich in clinop-

330

SITE 257

tilolite and cristobalite but with montmorillonite still thepredominant clay mineral; a trace of tridymite ispresent.

The boundary between Subunits la and lb was notcored and is arbitrarily placed 185 meters below the seafloor, at the middle of the uncored interval. Thesesubunits are probably lithologically gradational.

Subunit lb consists of red- and gray-colored cocco-lith detrital clay, with minor amounts of clayey cocco-lith ooze, and an 84-cm-thick clayey coccolith chalk atabout 240 meters. The consolidation of Subunit lbranges from stiff to semilithified. This is the only litho-logic unit at Site 257 where calcite is a significantcomponent of the sediment. The predominant claymineral is still montmorillonite. Ferruginous aggre-gates continue to be present in trace to 2%concentrations, but zeolites are entirely absent.

Subunit lc is a thin (13 m) red and reddish-brownsemilithified detrital clay. Most of the sediment is mont-morillonite (57%) and finely divided quartz (28%). Onlythe upper few centimeters are coccolith bearing, and therest of the subunit is barren. Core 10 is finely laminatedand contains a 5-cm-thick greenish-bluish gray layer.Ferruginous material (mostly hematite) occurs in con-centrations of up to 4%. Barite is present but the otherminor components characteristic of Unit 1 are absent orpresent only in trace amounts (Table 3).

The base of the red detrital clay is in sharp normalcontact with the underlying basalt. The contact at 262meters is based on drilling log information.

Unit 2

Basalt was reached at a depth of 262 meters and wasdrilled for a total of 64.5 meters, with a recovery of 32meters. The contact with the overlying red clay wasrecovered and is normal; there is considerable alterationof the uppermost half meter of basalt, but no indicationof deuteric or metasomatic alteration, or of baking, ofthe sediment. The sequence comprises medium- and

fine-grained olivine basalt, alternating approximately sothat a number of separate flows, on the order of seven oreight, can be distinguished. Several very shallow flowsmay be present, rendering an exact count impossible.The whole sequence is highly fractured, especially thecoarser intervals, there being many high-angle or evenvertical fractures. The majority are recemented withcalcite, which also occurs as spherulitic blebs, but thereare several horizontal veins, some 2 cm thick, ofserpentine chlorite; this material also forms films onsome of the open fracture surfaces. The upper (fine-grained) portions of several flows appear to have beenbrecciated, perhaps due to violent temperature changesresulting from contact with cold seawater, many of thefragments being recemented with red-stained calcite;this in turn may also be due to solution of carbonate inseawater heated by the extruded basalt and reprecipita-tion on cooling. Core 15 contains a short sedimentarysequence of graded sand and clay having a similarmineralogy to Subunit lb. This is detailed in CoreSummary 15, and may possibly be interpreted as aninterbasaltic sedimentation episode. There are also acertain number of short intervals (ca 10 cm) of redcarbonate. In each case, the micarb limestone, heavilystained with iron oxide (presumably derived from thebasalt), occurs at blank places in the basalt, at the top ofa core. This limestone may represent cavings, inasmuchas the drilling procedure in the basalt involves clearingthe bit face above the basalt. At least one vug containingwell-developed dog's tooth crystals of calcite, coatedwith hydrated oxide of manganese, was noted, as wereoccasional patches of botryoidal spherulitic calcite.

The basalt is vesicular, porphyritic, and subvariolitic;apart from Site 253, its porphyritic nature is unique tothis hole on Leg 26. Ten thin sections of the basalt werecut and are described below under two headings.

1) Medium-grained porphyritic and subvarioliticolivine basalt forms the coarser, lower, sections of eachflow. It exceeds the fine-grained rock in volume and is

TABLE 3Summary of Minor Components, Site 257

Core

Unit la123456

Unit lb78

Unit lc

910

Unit 2

10-17

Zeolite (%)

1-102-10

Tr (rare)12-204-158-50

00

00

Basalt

Ferroman- Ironganese (%) Oxides (%)

Tr-41

X 11-21-2

Tr-5

Tr-21-2

Tr-2Tr4

Quartz (%)

Tr-2Tr-2

Tr (rare)00

Tr (rare)

00

00

FishDebris (%)

Tr-5Tr

Tr-1Tr-1TrTr

TrTr (rare)

TrTr

Coccoliths (%)

TrTr (rare)

0Tr (rare)

00

10-3512-55

Tr-10

SiliceousFossils (%)

2-10Rare

0000

00

0Tr (rare)

331

SITE 257

on the whole slightly less fractured; it is considerablyfresher, probably partly due to the smaller amount ofglass it contains and to its having received less exposureto seawater.

The rocks are fresh and gray in color, subvariolitic tosubophitic, or hyaloophitic in texture. Two of the fiverocks sectioned are porphyritic. Olivine reaches 6% inone rock but is only present in traces in others; it issometimes euhedral, reaching 0.8 mm in size, but alwaystotally altered to dark bowlingite or smectite. In oneporphyritic rock, smectite patches reaching 2.5 mm mayrepresent olivine pseudomorphs.

Plagioclase forms laths reaching 0.8 mm or, in the caseof the more acicular crystals, 1 mm. There are occa-sional larger, chunky crystals, always zoned, and in theporphyritic rocks zoned phenocrysts reaching 4 mmoccur, often in groups and sometimes accompanied bysmaller (0.8 mm) phenocrysts of pyroxene. Clino-pyroxene otherwise reached 0.5 mm and occurs asgrains, ophitic plates, or in spherulitic, fan-like bunches.It may exceed plagioclase in abundance. Iron oxide,probably ilmenite, usually forms skeletal bars or rods,up to 0.4 mm, and grains. Dark or very dark pala-gonitic, mesostatic glass, between the groups of feld-spar and pyroxene crystals, completes the rocks.Vesicles are scarce compared with the fine-grainedrocks, but occasional palagonite-filled vesicles are pre-sent throughout and Sample 11-2, 27 cm contains veryabundant black, green, and colorless vesicles, filled withdark or pale palagonite, some of it vivid green in colorand vermicular in texture, with an inner filling of calcite.

2) Fine-grained or glassy vesicular porphyritic basaltvaries in texture from subophitic or subvariolitic toglassy. Olivine is present in very small quantities, thesubhedral crystals completely altered to bowlingite orpalagonite. One very euhedral crystal (0.5 mm) occurs in13-2, 80 cm, framed and cracked with iron oxide andreplaced, exceptionally, by chrysotile serpentine. Plagio-clase laths reach 0.8 mm or occur as zoned micropheno-crysts up to 1.2 mm. Pyroxene may also form small,zoned microphenocrysts up to 0.7 mm in length, butusually occurs as grains or spherulitic rosettes up to 0.5mm, from which the feldspar laths fan out. Iron oxide ispresent as grains up to 0.2 mm, but in the very fine-grained rocks it may not be exsolved from the glassymatrix. The glass itself is very dark to light brown incolor, varying from an interstitial mesostasis to a densematrix full of feathery devitrifying microlites, inter-spersed with the crystal groups. The vesicles are filledwith dark glass or bowlingite or palagonite; the lattermay be dark or bright vivid green. Some are filled withcalcite. In Sample 13-2, 80 cm the vesicles are black orgreen, filled with very dark opaque glass or vivid,fibrous celadonite, with a composite spherulitic texture.

SHIPBOARD GEOCHEMICAL MEASUREMENTSRoutine analysis for salinity, pH, and alkalinity were

conducted on interstitial water samples squeezed fromseven samples taken at depths in the hole from 8.0 to

oa

nut

tmHis

l a i

.s> s

1•3 a

r

olsiáė s s^

pq

13

*ü t~ VO VO m |

o o X

332

SITE 257

256.5 meters below the sea floor. In addition, pH wasalso measured on all but the deepest of the unsqueezedsamples by the punch-in method. The sampling and ana-lytical techniques are described in the report on Site 250,and the results for Site 257 are summarized in Table 5and presented in graphical form in Figure 3.

ResultsSalinity in the uppermost four samples was measured

as 35.4°/oo, or 0.7°/oo higher than the region's near-bottom water salinity of 34.7°/oo quoted by Wyrtki(1971). At a depth of 239 meters salinity was only34.4°/oo. Salinity again was measured as 35.2°/oo at 239meters; however, this value is suspect inasmuch as thesediment sample appeared badly disturbed and couldeasily have been contaminated. The deepest measure-ment, taken from a sample 256.5 meters below themudline, was also 34.4°/oo. The data are too scarce forthe apparent correlation between the decreased salinitywith depth to be interpreted or even evaluated.

AlkalinityAlkalinity decreases fluctuatingly and slightly with

depth in the hole, from a near-seabottom value of 2.00meq/kg to 1.66 in the lowermost sample. Again, theonly exception to this trend was measured in the suspectsample from 239 meters.

pHPunch-in and flow-through values differed by 0.07-

0.27 pH unit, four of the flow-through and two of thepunch-in values being the lower. All taken together, thepH values appear to increase irregularly and slightlydown the hole, from 7.0 to 7.25 in the uppermost sampleto between 7.22 and 7.52 in the sample taken from thegreatest depth.

PHYSICAL PROPERTIESThe physical properties measured at Site 257 were

porosity, acoustic velocity, bulk density, and thermalconductivity. The methods are described in the Ex-planatory Notes (Chapter 2). The results are shown inthe hole summary diagram.

Density, Porosity, and Water ContentDensity increases linearly with depth in the sediments

from 1.35 g/cc near the surface to 1.65 g/cc just abovethe basalt basement. The GRAPE densities are slightlyhigher than those from the syringe and section weight.Porosity and water content decrease very rapidly withdepth. Porosity ranges from 85% near the surface to 65%near basement. The rapid increase in consolidation withdepth, similar to Site 256, is to be expected with a slowsedimentation rate.

Acoustic Velocity and Acoustic ImpedanceThe acoustic velocity is very uniform with an average

of 1.50 km/sec for the upper part of the sedimentarysection, increasing to 1.60 km/sec near basement. Thereis no significant anisotropy in velocity. Vertical andhorizontal velocities were measured on 16 basaltsamples using the Hamilton Frame. There is no sys-tematic anisotropy but measurements in the two direc-tions differed by up to 4% which probably represents theextent of inhomogeneities in the samples. Obviousfractures, calcite-filled veins, and areas of pronouncedweathering were avoided.

Surprisingly, the velocities increase almost linearlywith depth from an average of 4.5 km/sec at the top ofthe basalt to an average of 6.2 km/sec 60 meters into thebasalt. These results are discussed in detail in thisvolume (Chapter 16).

CORRELATION OF SEISMIC REFLECTIONPROFILE WITH DRILLING RESULTS

An on-site profile was conducted with a 30-in.3 airgunand an SSQ41 sonobuoy (Figure 4). This profile showsabout 0.325 sec DT of sediments above acousticbasement with a time-intermittent (horizontally in-termittent considering the sonobuoy drift) intermediatereflector at 0.135 sec DT. No continuous, discretereflectors are seen below the acoustic basement. Thisbasement is the basalt reached by the drill at 262 meterssubbottom. The average sediment velocity is then 1.61km/sec. The intermediate reflector should then be near108 meters subbottom. Cores 4 and 5 bracket this depth

TABLE 5Summary of Shipboard Geochemical Measurements, Site 257

Sample(Interval in cm)

(Reference seawater)

1-5,144-1503-2,144-150\4, 144-1505-2,144-1507-5,144-1508-1,145-1509-3,140-150

Depth BelowSea Floor (m)

-

8.055.595.0

131.5207.5235.5256.5

LabTemp (°C)

-

22.322.522.822.622.622.222.8

pHPunch-in/Flow-through

-

7.26/7.037.03/6.856.99/7.067.19/6.927.42/7.537.52/7.35

/7.22a

Alkalinity(meq/kg)

-

2.001.811.862.001.790.881.66

Salinity(%°)

-

35.235.235.235.234.435.234.4

aToo stiff to measure punch-in.

333

SITE 257

0

50

150

2 0°

250

300

Punch-in

Flow-through

6.5 7.0 7.5 8.0pH

0.5 1.0 1.5 2.0Alkal inity (Meq/Kg)

34.0

Figure 3. Graphic summary of geochemical measurements taken at Site 257.

WHART0N BASIN-SITE 257

30°59'S 108°21'E5278 meters

— .135v

—.325 v \

\

\

m_

rtL_--t_--x_-:

• > Λ -. - «-

DETRITALCLAY

NANN0-DETRITALCLAY

DETRITALCLAY

OLIVINEBASALT

34.5 35.0 35.5Salinity (%,o)

1 0 0 -

2 0 0 -

3 0 0 -

4 0 0 -

500 J

Figure 4. Correlation of seismic profile and drilling results for Site 257.

334

SITE 257

and did not sample a change in lithology. However,Core 5 was more consolidated. A change in drilling ratewas not seen between Cores 4 and 5 that would indicatea change in lithology or induration.

PALEONTOLOGY

Biostratigraphic SummaryThe upper part of the sequence is devoid of cal-

careous microfossils and was therefore deposited belowthe carbonate compensation depth. Cretaceous radio-larians are present from 85 meters downwards. In a thinsection of a siliceous clay in Core 5 (125 m) a Globo-truncana of possible Campanian age has been found.Arenaceous foraminifera and calcispheres occur inCores 6 and 7. Calcareous nannoplankton of middleAlbian age are present in Cores 7, 8, and 9. In the lattertwo cores, arenaceous and calcareous benthonic fora-minifera, as well as planktonic foraminifera, arecommon.

A gradual increase in water depth, or shoaling of thelysocline, with time through Cores 8 to 6 can beinferred based upon the preservation distribution of cal-careous micro- and nannofossils. The lowermost part ofthe section, however, shows the reverse trend, and in ashort distance within Core 9 calcareous fossils aregradually eliminated.

Strongly recrystallized calcified radiolarians occur ina baked recrystallized limestone layer within the basaltsequence of Core 12, Section 1.

The restricted diversity of planktonic foraminiferaindicates a rather cold-water environment during theCretaceous.

Foraminifera

In Cores 1 to 4 (0-91 m) only rare and poorlypreserved arenaceous foraminifera were found, whichdid not allow any age determination. Cores 5 and 6 areequally devoid of calcareous microfossils except for asingle specimen of Globotruncana cf. elevata ssp., whichwas found in a thin section of a siliceous clay in Sample5-1, 140-142 cm, and which indicates a possible Cam-panian age for this level. A Cretaceous age for Cores 5and 6 is also supported by the scattered occurrence ofHaplophragmium cf. aequale (Roemer).

Calcareous benthonic foraminifera, includingOsangularia utaturensis (Sastri and Sastri), Gyroidi-noides cf. primitiva Hofker, and Gavelinella ex gr.intermedia (Berthelin) occur in Cores 7 to 9. They aremoderately preserved and etched in Core 7, but becomewell preserved, although nowhere abundant, in Core 8.At the same time, beginning with Core 7, Section 5, wefind an increasing number of planktonic fora-minifera: Hedbergella planispira, H. aff. infracretacea,and rare Ticinella. In Core 9 a rapid increase in thesolution effects can be noted from Section 1 down-wards. Planktonic foraminifera still occur in Section 1and a few specimens were found in Section 2; they aremissing, however, below this level. Few poorlypreserved calcareous benthonic foraminifera occurthroughout the lower part of Core 9, but none have beenfound in Core 10. The sediments immediately overlying

the basalt contain only few primitive arenaceous fora-minifera which are not suitable for dating this sediment.The planktonic foraminifera found in Cores 7 to 9support the Albian age determined by the nanno-plankton investigation. The restricted diversity prohibitsa precise age assignment and, as for Site 256, indicates acold-water environment at this site during the upper-most Lower Cretaceous.

Calcisphaerulidae

Calcispheres of the genus Pithonella occur betweenSample 7-1, 78-82 cm and 9-2, 18-22 cm. They havebeen described by Bolli, 1974.

Calcareous Nannoplankton

Stratigraphy: Calcareous nannofossils were foundonly in Cores 7, 8, and 9 and are all of middle Albian age(Prediscosphaera cretacea Zone).

Preservation: A continuous decrease of solutioneffects is observed from Sections 1 through 6 of Core 7.Samples 257-7, CC and 257-8-1, 139 cm contain onlyslightly etched assemblages. An increase of etching isobserved in Samples 257-8-2, 9 cm through 257-9-2, 37cm. The samples from the lower part of Core 9 andthose from Core 10 are barren. A shipboard study of 20smear slides from red, brown, gray, and pale greenpebbles and the grayish-brown matrix of the drillingbreccias in Core 8, Sections 2 and 6 showed no dif-ference in age between pebbles and matrix, but adecreasing abundance of coccoliths, due to etching,from pale green to gray to brown to red-brown-coloredpebbles.

Paleoecology: The middle Albian assemblages aresimilar to those from the Gault Section at Copt Point,Folkstone, England. They represent a non-Tethyan,temperate to cool-water paleoenvironment.

SEDIMENTATION RATESFrom 0 to 199.5 meters subbottom depth only a net

sedimentation rate of 2 m/m.y. can be calculated, due tothe absence of paleontological data. It is likely that therate for the Cenozoic is much below this.

The sedimentary sequence between 199.5 and 250.0meters belongs to the middle Albian and accumulated ata rate of at least 25 m/m.y., if we assume that the middleAlbian extended over a period of 2 m.y.

SUMMARY AND CONCLUSIONS

Summary of ResultsSite 257 is located in 5278 meters of water in the

southeastern Wharton Basin. Near the site seismicprofiles show about 0.3 sec DT of sediments with aghostly internal reflector near 0.10-0.15 sec DT. Onehole was drilled at this site through 262 meters ofsediments and 64.5 meters of basalt. The oldest sedimentdated is middle Albian, 13 meters above the contact.

One sedimentary unit and three subunits were recog-nized. From the surface down to between 170 and 200meters is a dark reddish-brown detrital clay, zeolite rich,or zeolite bearing. Below this and down to 249 meters isa reddish-brown to gray coccolith detrital clay to clayey

335

SITE 257

coccolith ooze and chalk. Between this unit and thebasement is 13 meters of barren reddish-brown detritalclay. The contact with the basalt is sharp and appearsconformable. The basalt is gray, vesicular and por-phyritic, highly fractured with veins of calcite and ser-pentine. Seven or eight flows were drilled. It is fresherdeeper into the hole which caused a decrease in drillingrate with depth. The acoustic velocity in the basaltincreases from about 4.5 km/sec at the contact to over 6km/sec 64 meters below, also indicating increasingfreshness. At the top of Core 15 (298-307.5 m) a claylayer plus consolidated graded sand with subroundedpebbles of basalt was recovered. We have notestablished whether this material was in situ or not.

The site is largely barren of microfossils. Cretaceousradiolarians were found at 85.5-95 meters and middleAlbian nannofossils and foraminifera were found below199.5 meters. Only one species of planktonic fora-minifera was seen suggesting a cold-water environmentfor the middle Albian. The middle Albian section is atleast 50 meters thick which implies a minimumsedimentation rate of about 25 m/m.y. for thissequence. Because Cretaceous radiolarians are foundnear 85 meters and Quaternary radiolarians at 10meters, the entire Tertiary and Upper Cretaceous isrestricted to 75 meters, or a sedimentation rate near 1m/m.y.

Preliminary Conclusions

As with Site 256, much of the section at Site 257 wasdeposited below the carbonate compensation depth(CCD). However, the barren layer below the Albiancoccolith clay at Site 257 indicates that, unlike Site 256,sedimentation began here below the CCD, rose above itfor a short period, then again took place below it. ACretaceous cold-water environment, and therefore amore southerly location, is indicated by the fauna hereas at Site 256. Also, both sites show a rather thick LowerCretaceous (Albian) sequence and a thin Upper Cre-taceous through Tertiary section. It is tempting to cor-relate this decrease in sedimentation rate and/or hiatusto changes in oceanic circulation associated with thebreakup of Australia-Antarctica in the Eocene, butlacking more precise dating, this is only speculation.

It was disappointing that the sediment-basalt contactproved barren. The crust might be significantly olderthan middle Albian, but the high sedimentation rate forthe lower section would argue against this. From tec-tonic arguments the crust here should be close to 120m.y. The apparently young age could be explained by adisconformity at the base of the section or the basaltsequence being younger than the true basement. We sawno obvious changes in the lithology of the basaltsequence to indicate a disconformity, but a clay layer at298-307.5 meters may indicate an unconformity. A final

explanation for the apparent young age is the possibilityof a north-south-trending right-lateral fracture zonebetween Sites 256 and 257. This would tend to moveyounger material south to where the older materialwould be expected.

REFERENCES

Bolli, H., 1974. Jurassic and Cretaceous Calcisphaerulideafrom DSDP Leg 27, Eastern Indian Ocean. In Veevers, J.J., Heirtzler, J. R., et al., Initial Reports of the Deep SeaDrilling Project, Volume 27: Washington (U.S. Govern-ment Printing Office).

Wyrtki, K., 1971. Oceanographic atlas of the internationalIndian Ocean expedition: Washington (U.S. GovernmentPrinting Office).

Core, SectionTop of

Interval (cm)

1-2, 901-5, 902-2, 1213-2, 904-2, 915-2, 906-1, 1317-2, 907-5, 918-2, 899-2, 9010-1,89

APPENDIX: AGrain-Size Determinations for Site 257

SubbottomDepth

(m)

2.46.9

12.249.987.9

125.9162.8201.9205.4239.9249.4257.4

Sand(%)

0.00.20.00.10.00.00.00.00.00.40.00.9

Silt(%)

18.321.115.912.019.315.611.5

5.86.5

16.63.83.1

Clay(%)

81.678.784.187.880.684.388.594.293.582.996.196.0

Classification

ClayClayClayClayClayClayClayClayClayClayClayClay

APPENDIX BCarbon-Carbonate Determinations for Site 257

Core, SectionTop of

Interval (cm)

1-2, 88.01-5, 88.02-2, 1203-2, 884-2, 895-2, 886-1, 1307-2, 887-5, 888-2, 889-2, 8810-1,88

SubbottomDepth(m)

2.386.88

12.2049.8887.89

125.88162.80201.88206.38239.88249.38257.38

TotalCarbon

(%)

0.10.10.10.10.10.00.21.71.22.10.10.4

OrganicCarbon

(%)

0.10.10.10.10.10.10.20.20.30.10.10.1

CaCCs(%)

0000000

127

1702

336

APPENDIX CX-Ray Analyses for Site 257

Core

CoredInterval

Below SeaFloor (m)

Sample DepthBelow SeaFloor (m)

Bulk Sample

123456789

10

0.0-9.59.5-19.0

47.5-57.085.5-95.0

123.5-133.0161.5-171.0199.5-209.0237.5-247.0247.0-256.5256.5-263.0

6.912.351.790.2

125.9162.8201.9239.9249.5257.4

88.4 81.9 - 21.2 5.4 10.2 5.8 21.3 36.184.383.284.187.184.581.381.478.276.9

75.473.875.179.975.770.770.966.063.9

9.6 -8.14.1 5.94.8 13.59.3 -

18.8 8.45.3 8.2

22.5- 34.5 -

4.12.93.05.8

11.110.09.14.82.7

1.8-1.22.02.1--1.5_

11.212.0

-4.6-4.87.0-

21.59.4

18.318.419.1

8.25.83.08.2

43.667.740.224.239.249.864.664.849.8

8.- -1.3 26.2.3 24.- 19.- -- -- -

2

032

2 _

3.44.7

2-20µ Fraction

123456789

10

0.0-9.59.5-19.0

47.5-57.085.5-95.0

123.5-133.0161.5-171.0199.5-209.0237.5-247.0247.0-256.5256.5-263.0

6.912.351.790.2

125.9162.8201.9239.9249.5257.4

81.171.570.859.965.666.377.076.274.068.3

70.455.554.537.446.247.364.162.859.450.5

- 42.3- 30.1- 31.2

10.29.9

12.917.219.226.956.6

8.55.4

— 7 93.79.1

19.037.7

- 40.016.310.8

15.33.72.92.91.62.32.3-

1.9_

3.28.9

14.8-4.03.97.6

10.6—

12.720.928.711.5

8.313.623.111.520.613.9

9.913.314.4

7.211.2

8.012.118.729.815.1

8.217.7

- -64.5

- 56.0- 40.4- -- -- -_ _

--------3.23.6

1.4

< 2µ Fraction

12345689

10

0.0-9.59.5-19.0

47.5-57.085.5-95.0

123.5-133.0161.5-171.0237.5-247.0247.0-256.5256.5-263.0

6.912.351". 790.2

125.9162.8239.9249.5257.4

87.086.182.080.281.182.084.775.175.3

79.8 -78.3 -71.9 -69.170.5 -71.8 -76.161.161.3 -

23.16.9

15.7 -5.2 18.77.1 14.59.5 -

11.6 -20.6 -52.2 -

4.31.78.25.67.0

12.110.3

2.62.9

9.92.63.4-

1.32.6-

_

-15.612.3

-

4.15.57.0__

11.48.6

10.27.6

10.04.36.4

25.42.6

42.444.132.236.920.741.453.7

35.131.7

- —1.0

- -11.2

2.0 17.413.5

- -_ __

- --- -

_- -- -- -

3.0 -3.7

8.819.518.014.615.910.810.9

13.36.9

^Narrow Peaks at 4.63Åand 9.33Å. P = present; T = trace.^ r o a d peaks at 3.00Å, 4.94Å, and 4.13Å among others. The peaks are similar in position, ratio, and shape to goethite and hematite. However, the unidentified

mineral has several peaks not represented by goethite's or hematite's peaks. P = present.cVery narrow peaks at 9.86Å, 2.492Å, and 1.700Å among others. A = abundant.

Cored Interval .-0.0-9.5 m Cored Interval:9.5-19.0 m

10YR 3/3 w/10YR 7/6 specks

LlOYR 5/4J stretched

layer

10YR 3/2

LITHOLOGIC DESCRIPTION

10YR 3/3 w/.minor 10YR 3/2[10YR 3/2 lump]

10YR 3/2 w/ -minor 10YR 7/6patches fewmm in size

Dark brown DETRITAL CLAY, coloredby trace quantities to 4% micro-scopic opaque or amorphous trans-lucent particles and aggregates.

TEXTURE: Sand 0.0-0.2%S i l t 18-21%Clay 79-82%

COMPOSITION:

85-94% detr i ta l clay1- 5% amorphous ferruginous

material1-10% zeol i te2-10% fragments of diatoms,

radiolar ia and spongespicules

Tr- 5% collophanous f ish debrisTr- 2% quartzTr- 2% feldsparRare traces of mica, glauconite,

authigenic carbonate, andcoccoüths.

Total Carbon: .1%Organic Carbon: .1%Calcium Carbonate: 0%

CONSOLIDATION: Soft.

2

FOSSILCHARACTER

t


JOYR 7/6stretched

10YR 3/3

10YR 3/2.5

DETRITAL CLAY, dark brown in upper portions,grading down to moderate yellowish brown inSec. 4, which is moderately mottled with darkyellowish brown mottles approximately 3 cmin diameter. Siliceous fossil remains arelargely missing, and the detrital clayparticles exhibit authigenic growth orreplacement rims which become extinct undercrossed nichols at angles which differ fromthe particle cores.

TEXTURE: Sand OJSSilt 16%Clay 84%

--10YR 4/6

i-[5 cm 10YR 3/2mottle]

H[3 cm 10YR 3/2(-mottles]

10YR 5/4

COMPOSITION:

87-98% detr i ta l clay2-10% zeolite

Tr- 2% quartzTr- 2% feldspar

1% ferruginous material as beforeTr collophanous f i sh debris

Rare traces of glauconite, coccoHths anddiatom fragments.



Explanatory notes in chapter 2


Cored Interval .-47.5-57.0 m Hole Core 4 Cored Interval:85.5-95.0 m

FOSSILCHARACTER

I


7.5YR 5/8 Dark orange DETRITAL CLAY, withapprox. 3% black 0.5-3 cm patches,many of which possess 1-2 mm blackmicronodular cores. Sec. 3 has 35-25 cm dark brown and very darkyellowish brown layers and 2 1-2cm red mottles. Zeolites are almostn i l .

TEXTURE: Sand 0.1%S i l t 12%Clay 88%

7.5YR w/LN1 streaks

"[2 mot t les ,10R 5/8]

-7.5YR 3/4>IOYR 3/2

7.5YR 4/4

1 cm

COMPOSITION:

98-99% d e t r i t a l clay1% black opaque ferromanganese

(?) c lay-s ized grainsTr- 1% collophanous f i s h debrisRare traces of z e o l i t e , quar tz ,

fe ldspar , mica andcoccol i ths .

Total Carbon: . 1%Organic Carbon: . 1 %Calcium Carbonate: 0%



FOSSILCHARACTER

t/)u_

CoreCatchei


5YR 6/8

"-"do-, W/5YR 3/1 & Nl

Mixed 5YR 6/8,5YR 3/1,5YR 2.5/1.5,5YR 3/4

5YR 6/8]

Zeol i te-r ich DETRITAL CLAY,predominantly reddish yellow withmixed dark brown chunks.

TEXTURE: Sand 0%Silt 19%Clay 81%

COMPOSITION:

85% clay12-20% zeol i te

1- 2% opaque and amorph. ferrug.material

Tr- 1% collophanous fish debrisTraces quartz and feldsparsOne observed trace of coccoliths



same, but5YR 3/2 &5YR 2.5/2pred.

7.5YR 5/8 w/mi nor7.5YR 4/0


Cored Interval: 123.5-133.0 m Cored Interval:161.5-171.0 m

FOSSILCHARACTER

CoreCatcher


Dark brown DETRITAL CLAY, z e o l i t e -bearing or zeolite-rich. In Sec. 1,at top, one 3 x 4 cm l i th i f ied(partially si l ic i f ied) piece ofdark gray mudstone with smallpinkish lenses. Sec. 1 alsocontains minor chunks of materialwhich are 100% zeolite.

,[3 x 4 cm 7.5YR 4/0partially s i l ic .mudstone w/ 7.5YR 6/8lenses]

TEXTURE: S a n d :Silt:Clay:

>[7.5YR 3/2 only]

[7.5YR 6/8 mottles]

COMPOSITION:

84-94% detr i ta l clay4-15% zeolite1- 2% amorphous and opaque ferrug.

materialTr collophanous f ish debrisTr quartz and feldspars

Total Carbon: 0%Organic Carbon: .1%Calcium Carbonate: 0%

CONSOLIDATION: Stiff whereundeformed.

10YR 3/2

FOSSILCHARACTER

CoreCatchei


2.5YR 5/8 &10R 5/8

} [ l - 2 cmchunks7.5YR 3/2]

1 [chunks ofJ5Y 5/1]

Red zeolite rich and zeolite bearingDETRITAL CLAY with scattered d r i l l i ngbiscuits of gray ZEOLITE DETRITAL CLAY.

TEXTURE: Sand 0%S i l t 12%Clay 88%

COMPOSITION:

ClayZeol i teAmorph. Fe oxidesQuartz, feldsparsColloph. f ish deb.

Red detr i ta l clay83-90%8-12%1- 5%

TrTr

Zeolite detr i ta l clay50-70%30-50%0-Tr

TrTr

Total Carbon: .2%Organic Carbon: .2Calcium Carbonate:

7.5YR 5/4 w/minor 2.5Y 6/0and 2.5YR 5/8



Core 7 Cored I n t e r v a l . -198.5-209.0 m S i t e 257 Hole Core 8 Cored I n t e r v a l : 2 3 7 . 5 - 2 4 7 . 0 m

FOSSILCHARACTER

CoreCatcher


All d r i l l i ngbreccia; pred.10R 5/8 w/stretched chunksand biscuits of5Y 5 / 1 , 2.5Y 5 / 1 ,2.5YR 5/0,2.5Y 4/0,5YR 4/0, and7.5YR 4/0.

[cocco. oozechunk]

[folded collapsed3-core liner]

5YR 4/2

Drilling breccia of red COCCOLITHDETRITAL CLAY with drillingbiscuits and chunks of grayCOCCOLITH DETRITAL CLAY and minorCLAYEY COCCOLITH OOZE in Sees 5and core catcher.

TEXTURE: Sand 0%Silt 6%Clay 943!

COMPOSITION:

61-87% detr i ta l clay (rarely 46-49%)

10-35% coccoliths (rarely 50-53%)Tr- 2% ferruginous materialTr- 2% authigenic carbonate

(?siderite)Traces of quartz and feldsparsTraces of collophanous f ish debris

Total Carbon: 1.2-1.7*Organic Carbon: .2-.3%Calcium Carbonate: 7-12%

CONSOLIDATION: S t i f f where lessdisturbed byd r i l l i n g .

Pred. 10R 4/6, 5/8& 4/8, w/ 3%5Y 6/1 chunks


Section 1 is d r i l l i n g breccia ofred and gray COCCOLITH-RICHDETRITAL CLAY. Rest of core is 2intervals of reddish brown andl igh t red COCCOLITH DETRITAL CLAYwith an intervening interval (16-100 cm, Sec. 2) of reddish brownCLAYEY COCCOLITH CHALK.

TEXTURE: Sand 0.4%S i l t 17%Clay 83%

ClayFerrug. matterQuartz and feldsparsCoccolithsAuth ig . carb.Fish debrisForams

Clayeycoccolithchalk

55%T r - 1%

Tota l Carbon: 2 . 1 *Organic Carbon: . 1 %Calcium Carbonate: 17%

CONSOLIDATION: S e m i - l i t h i f i e d whereless disturbed.


Site 257 Hole Core 9 Cored Interval: 247.0-256.5 m


FOSSILCHARACTER

CoreCatche


Red and dark reddish brown DETRITALCLAY, cocco l i th bearing only inSec. 1 ; wi th a 10-cm layer and a4-cm layer i n Sec. 3.

TEXTURE:

J.5YR 5/6

5YR 3/2

10YR 5/6,10YR 5/8

10R 4/4, 4/6

cm 5G 6/1 &5B 7/1]

• [ -do- , 4 cm]5YR 3/3

2.5YR 4/4, 4/6

Sand 0%Silt 4%Clay 96%

COMPOSITION:

94-100% detr i ta l clayTraces quartz and feldsparsTr- 2% amorphous and translucent

microscopic ferrug.material

Tr collophanous f ish debrisTr- 1% coccoliths, except for 5%

in Sec. 1.Rare traces of authigenic calcite

Total Carbon: 0.1%Organic Carbon: 0.1%Calcium Carbonate: 0.0%

CONSOLIDATION: Semi-l i thi f ied.


Core 10 Cored Interval : 256.5-263,0 m Core 11 Cored I n t e r v a l : 2 6 3 . 0 - 2 7 2 . 5 m

FOSSILCHARACTER

CoreCatcher


>,2.5YR 3/2.2.5YR 4/6 w/ 1 x 2 cm patch of 5G 6/12.5YR 3/2 w/ 1-2 mm Nl laminae 0.5 to 2 cm apart

s5G6/_l & 5B 7/1\2•5YR 4/610R 3/4 & 2.5YR 2.5/4 w/l ight pink & Nl laminae0.5-3 cm apart

Weath.basalt

TOP OF CORE:

Dusky red, red and dark red DETRITAL CLAY,finely laminated in part, with a 2 cm patchand a 5 cm layer which are greenish gray tolight bluish gray. The basal clays contain5% radiolarians and 4% finely disseminatedferruginous oxides and radiolarian fillings.

TEXTURE: Sand 0.9£S i l t 3.OSClay 962

COMPOSITION:

91-100% clayTraces quartz and feldsparsTr- 4% ferruginous materialTraces of collophanous f ish debrisRare traces of authigenie carbonateAbove the basal clays, only one rare

trace occurrence of radiolarians.

Total Carbon: 0.4%Organic Carbon: 0.1%Calcium Carbonate: 2%

CONSOLIDATION: Semi- l i thi f ied.

BASE OF CORE:

Weathered (limonitized) and fractured f ine-grained porphyritic BASALT, with calcite andchlorite or serpentine fracture f i l l i n g s .

FOSSILCHARACTER

CoreCatcher


Fine-grained,vesicular

^Arrows-•-indicate f i l led

.fractures

Few vesicles'[dark gn veins]Medium grained

BASALT, fine-grained and vesicularor medium-grained as indicated.Weathered and randomly fractured(less so in Sec. 2); 1-3 mm widefractures f i l led with calcite,lesser ?chlorite and/or serpentine,and even lesser reddish ironoxides. The vesicles are f i l ledwith the same material. The coreconsists of pieces 2 to 40 cm long,average length being 5 to 10 cm.

NOTE: DRILLING LOG PLACES THESEDIMENT-BASALT CONTACT AT262 m.

^"[Abundant ve ins , mostlyr w h i t e , 1-2 mm wide]

TVesicular[2-3 cm th i ckf i l l e d fracture]

Weathered, fine-grained vesicular BASALT with a0.5 cm carbonate-filled fracture.



Site

AGE

2b/

AMS ZO

NENO

S

2 i

Hole

FOSSILCHARACTER

AMS

FOR SO

L.EC

TS

t U_

8

NAN

B

AP

Core 12

o

1

2

3

METE

RS

-

ITI

1 .0 -

;

I 1

I I

I I

CoreCatcher

Cored I n t e r v a l :

LITHOLOGY

VOID

1 ' | ' i '

ION

IFOR

MAT

Q

PLE

THO.

SAM

TS

272.5-282.0 m


Separate piece, 2.5YR 6/2 & 4/2 pale to weak redl i t h i f i e d MICARB LIMESTONE.

Fine-grained, vesicular

"*~l cm fractures f i l l e d withcalc i te and red iron oxides

No vesicles

U. 5 cm indurated mass ofiron-stained carbonate

-, Vesicular[basalt in vert ical contact with carbonate-Iron oxidecemented breccia]

Few vesicles^ . [2 cm l i gh t red breccia cap on basalt piece]

^.Vesicles[4 cm piece of basalt with breccia as at top of Sec ]

Basalt, f ine-grained and vesicular, ormedium grained. Weathered, with abundantrandomly oriented fractures (not plottedindiv idual ly as in Core 11); the fracturesare 3 to 20 mm wide and are f i l l e d withcalc i te and green ?chlorite and/orserpentine. As indicated, several piecesare brecciated and recemented with carbonateand red iron oxides. The vesicles are f i l l e dwith calc i te and the green replacementminerals.

Entire core consists of pieces 2-43 cm long,averaging 5-10 cm long.


Site 257

ONE

FORA

MSZ

NANN

OS

Hole

FOSSILCHARACTER

FORA

MS

-H LL.

O LxJ NANN

OS

B

il

Core 13

on

:

</>

1

2

3

£5

0 . 5 -

I . U -

1 1 1

-

-

11

11

1

Mi

ll

MM

CoreCatcher

Cored In

LITHOLOGY

VOID

'*';';*'< \* *

terval:

ION

RMAT

DEFO

PLE

.SAM

LITH

O

*TS

»TS

*TS

282.0-290.0 m


-""[Fractures f i l l e d with iron oxide r ich carbonate]

-«-[5 cm wide calc i te fracture f i l l i n g ]

Medium grained, few vesic les, fresher than above orprevious cores.

[6 mm l igh t green vein]

No fracture f i l l i n g s , but coreis highly fractured.

Few fracture f i l l i n g s , several mm wide.

"•"[dark green vein]

Color pred. reddish-green""[2 dark green veins 5 mm wide]

Light brownish gray matr ix; white and reddish brecciatedand recemented fracture f i l l i n g s very abundant; wholerock is v i r t ua l l y a breccia. Vesicular from 125 cm down.

BASALT, predominantly medium grained andvesicular; re la t ive ly fresh from 37 cm inSec. 2 to 75 cm in Sec. 4. Variablyfractured and f rac tu re - f i l l ed with ca lc i te ,?chlori te and/or serpentine, and reddishiron oxides. In par t , the fracture f i l l i n g sare exceedingly abundant and the rock hasthe aspect of a breccia.


Cored Interval:290.0-298.0 m

FOSSILCHARACTER

CoreCatcher


Fine-grained, novesicles abund.calcite-fi l ied f r .

-[2 cm patch 1-3 mm"calcite crystals]

ARROWS INDICATE PRED.

FLIGHT GREEN FRACT.

rFILLLINGS UNLESS OTHER-

WISE INDICATED

^"£8 mm I t gn & w h i t e

Hracture f i l l i ng ]

.Vesicular ( f i l led) , w/pi-5 mm gn veins, fewerpwhite calcite veins

Larger vesicles; green-fract. f i l l ings as'indicated by arrows

Coarser; larger vesicles;_plag. phenocr. up to 5 mm

[1 nrn white fracturef i l l i ng ]

^Finer grained; onlyslightly vesicular;

[.only isolated phenocr.

-<-[2 cm dark red patch]-«-[red patch]

[1.5 cm patch w/massive coarse calcite]

Weathered BASALT, variably fineto medium grained, in part por-phyritic with phenocrysts up to 5mm long; variably vesicular, thevesicles up to 2 mm in diameterinvariably f i l led with calcite,palagonite, and ?serpentine and/orchlorite. Fractured, with 1-10 mmwide ?chlorite and serpentinefracture f i l l ings and lessercalcite fracture f i l l ings.

The entire core consists of pieces2 to 28 on long, the average lengthbeing 5-10 cm.


Site

IGE

o

257

ONE

FORA

MS ZNA

NNOS

Hole

FOSSIL

CHARACTER

1 FOR

AMS

DISS

OLEF

FECT

NANN

OS

RPE

RPE

RPE

CPE

FPEß

SILI

CEFO

SS.,

Core 15

CTIO

1

1

2

:TERS

—

1 . 0 -

--

-

--

-

--

—

Cored In terv

LITHOLOGY

•' .• S < : W v : : : •' •• : V

• r i *sy* »v

f * t. v * r >Λ*>L"'

Λ, > * < *• '^'V

^ 1 * ' 'VA*

iv<",",1,1,''.

RMAT

1 DE

FOI

al .-298.0-307.5 m

| L

ITHO

HO»KE*RFRFRF

KE


2.5YR 3/4 dark reddish brown DETRITAL CLAY; soupy d r i l l i n g—breccia to 25 cm, s t i f f from 25-33 cm, i n sharn contact with

S i l t y f ine ss grading down to crse ss, a—derived.

Pebbly gravel, max size 2.5 cm, ang-sub-r

1 fresh & basalt-

dd basalt andrarer red micarb 1st.BASALT, medium-grained, porphyr i t ic , s l i g h t l y vesicular,the vesicles up to 2 mm in diameter f i l l e d with calci te andgreen palagonite and/or ?serpentine and/or ?chlor i te ;fractured with very few thin calc i te fracture f i l l i n g s .8 mm widecalci te-f i l ledfracture

~ Vesicular; as indicated,±abund. calcite and iron-±oxide rich calc i te-f i l ledJfractures up to 1 cm wide

$ Fine-grained, badly* fractured, weathered,

yellowish-greenish gray^BASALT with few dark red

micarb patches and 2calc i te-f i l led fracts.

NOTES: The uppermost DETRITAL CLAY isobviously d r i l l cuttings. The lowermostDETRITAL CLAY is very s t i f f , the lowermostsingle chunk being 6 cm in length. This isin sharp v-shaped contact with a very wellsorted fine-grained sand composed of re-markably fresh l i t h i c fragments of basalt,including prominent pieces of fresh plagio-clase. 2 to 3 cm below the contact with theoverlying clay, the fine sand has gradation-al ly coarsened downward into a medium tocoarse sand of the same composition, witha 1 cm interval containing discrete 0.2 to0.8 mm pieces of the same very s t i f f redclay. However, the medium-coarse sandinterval is free of these clay chunks for8 cm below the 1 cm interval. Beneath themedium-coarse sand is a coarse sand, alsobasalt-derived and fresh, containing abundant0.2-0.8 cm chunks of redis a loose accumulation orounded granule-pebble gr<pebbles tending to occurinterval. Most of this gr

Jay. Below the sandangular to sub-

v e l , the coarsestt the base of the

avel is basalt, withseveral pieces of reddish micarb limestone.

The extremely well-sorted nature and com-paction of the fine sands in particular isvery noteworthy. In overall appearance, theentire sand-to-gravel interval looks l ike asingle graded sequence, possibly with somefines washed out of the gravels.

The basalt portion of the core consists of2-28 cm pieces, the average length beingabout 5 to 10 cm.


Site 257

AGE

!AMS ZONE

NOS

o -a:

Hole

FOSSILCHARACTER

ε

SOL.

ECTS

NOS IP.

Core 16

1

2

3

METERS

1 . 0 -

-

z

1 1

1 1

1 1

_

Cored I n t e r v a l :

LITHOLOGY

VOID

V"/ ^ "•i % " t ^IO

NEFORMAT

THO.SAM

- 1

KE

TS"

307.5-317.0 m


At t o p , 4 cm piece of 5YR 6/3 & -6/4 reddish brownMICARB LIMESTONE.

Light grayish green f ine-grained weathered BASALT.

—Same; l i g h t gray, coarser than above, porph. & vesicular.BASALT, coarser, ves icu lar , wi th few dark green & white

-•-fracture f i l l ings.[2-10 mm white calcitefracture f i l l i n g ]

BASALT, light gray, vesicular, porphyritic, with 1-3 nrniphenocrysts, with predominantly greenish gracture f i l l ings-*-3 mm to 1 cm wide, indicated by arrows.

•*"[2 mm black f i l led fracture]

BASALT, very vesicular, the vesicles about 1 mm in diameter,f i l led with caldte and green alteration minerals; withvery few carbonate-filled fractures as indicated.

"""Entire core consists of 25-2 cm long pieces, the averagelength being about 10 cm.

Core 17 Cored Interval: 317.0-326.5 m


FOSSILCHARACTER


10YR 4/3 & 2.5YR 4/4 yellowish brown and red MICARB—LIMESTONE with masses of greenish carbonate crystals.

BASALT, greenish gray, vesicular, the vesicles being1 mm in diameter and f i l led with calcite and greenalteration minerals as in previous cores; fracturedand the fractures f i l led predominantly with ?chlorite

^.and/or ?serpentine, and lesser calcite and iron oxiderich calcite 1-3 OT wide, indicated by short arrows.

l•Vertical f i l l e d fracture.

BASALT, light to dark gray, fine-grained, vesicular,f i l l e d fractures as above indicated by arrows.

"Y [Intensely fractured into 1-2 cm pieces]

[Light green massive vein]

[2 white calcite-fil led fractures 2-3 mm wide]

Dark gray, irregularly vesicular BASALT, medium-finegrained, fractured, but fractures not f i l led except for

-2 indicated.

Light gray fine-grained basalt, no fracture f i l l i n g s .

Entire core consists of pieces 1-36 cm long,with an average length of 5-10 cm.


SITE 257

•0 cm

25

50

75

—100

125

150257-1-1 257-1-2 257-1-3 257-1-4 257-1-5 257-1-6

346

SITE 257

257-2-1 257-2-2 257-2-3 257-2-4 257-2-5 257-2-6

347

SITE 257

0 cm

25

50

75

100

125

150257-3-1 257-3-2 257-3-3 257-4-1 257-4-2 257-4-3

348

SITE 257

0 cm

— 25

— 50

— 75

100

125

150257-4-4 257-5-2 257-5-3 257-6-1 257-7-1 257-7-2

349

SITE 257

0 cm

25

50

75

100

125

150257-7-3 257-7-4 257-7-5 257-7-6 257-8-1 257-8-2

350

SITE 257

0 cm

25

50

75

100

125

150257-9-1 257-9-2 257-9-3 257-10-1 257-11-1 257-11-2

351

SITE 257

0 cm

— 25

50

75

100

125

150257-11-3 257-12-1 257-12-2 257-12-3 257-13-1 257-13-2

352

SITE 257

0 cm

— 25

50

75

100

125

150257-13-3 257-13-4 257-14-1 257-14-2 257-14-3 257-14-4

353

SITE 257

0 cm

25

50

75

100

125

150257-14-5 257-15-1 257-15-2 257-15-3 257-16-1 257-16-2

354

SITE 257

•Ocm

1—25

50

I—75

I—100

I—125

150257-16-3 257-17-1 257-17-2 257-17-3 257-17-4 257-17-5

355

SUMMARY OF DRILLING RESULTS: SITE

BIOSTRATIGRAPHY

FORAMINIFERA

Barren

Rare arenaceousforaminifera

Globotruncana

sp.

Upper Cretaceousarenaceousforaminifera ,Pithonelia sp.

NANNOPLANKTON

Barren

Barren

RADIOLARIANSMACRO-FOSSILS

AGE

o-3

C

c e

Cam

pan

αi

°

αiX>cr

CORESNO/DEPTH

- π

2

-50 ~

4

-100

-150

6

: 257/0 - 200 m


i=z=z=S

Mn

_ _._ _

Mn

:-z-z=z

:

Tz-z

zz

zz

:

_—_—z~_

1.

Dark reddish brown

DETRITAL CLAY, predominantl>

zeolite-rich or zeolite-

bearing

[3 % black 0.5 - 3.0 cm

patches with 1 - 2 mm

ferromanganese

micronodular cores]

iD GRAPE

× SYRINGE

BULK DENSITY

00 2.50 1.i

!

ACOUST. VEL.KM/SEC

0 6.0

as

a

ffl

FORAMINIFERA

AFenacëöiJs Fn3calc. benth. foram.

Pithnneila

Commonplanktonicand benthonicforaminiferaPithonella

Arenaceousforaminifera

SUMMARY

BIOSTRATIGRAPHY

NANNOPLANKTON

PrediscosphaeracretaceaZone

RADIOLARIANS

.^RecrystallizA.."Wl Radio1ariar

1

•

OF DRILLING RESULTS: SITE

MACRO-FOSSILS

AGE

<

T3T3

Cret ?

CORESNO/DEPTH

7|

T8-250 π

10|

111

12f

_L1 3P

141

-300 J

i6r

171

-350

-

257/200 - 400 m

i TTMΠI ΠΠTP ΠF^PRTPTTΠN

- .-̂– -- -*---

>ZfZ^Z;

A v Λ^- <Λ Λ •T JΛ t_ < < Λ

n<<V«( V * > v

y 5 <- v <.A

i.

Reddish brown to gray

COCCOLITH DETRITAL CLAY,

CLAYEY COCCOLITH OOZE, and

CLAYEY COCCOLITH CHALK

Stiff and semi-lithified

laminated reddish-brown

DETRITAL CLAY

Vesicular fine to medium

grained locally porphyritic

OLIVINE BASALT

D GRAPE

× SYRINGEBULK DENSITY

00 2.50 1.

×

×

ACOUST. VEL.KM/SEC

0 6.0

ö

α

%

%

CD

o

9

CD

Documents

The Shipboard Scientific Party - Deep Sea Drilling · Subunit lc is a thin (13 m) red and reddish-brown semilithified detrital clay. Most of the sediment is mont-morillonite (57%)