Barron, J., Larsen, B., et al., 1991Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 119

11. ANALYSIS OF SEDIMENTARY FACIES USING BULK MINERALOGICALCHARACTERISTICS OF CRETACEOUS TO QUATERNARY SEDIMENTS

FROM THE KERGUELEN PLATEAU: SITES 737, 738, and 7441

Gerhard Bohrmann2 and Werner U. Ehrmann2

ABSTRACT

Carbonate-free portions of Upper Cretaceous to Holocene sediment samples from the Kerguelen Plateau in thesouthern Indian Ocean were investigated by X-ray diffraction. Downhole variations in the content of opal-A, opal-CT,quartz, feldspar, barite, and clinoptilolite were studied at Site 737 on the northern Kerguelen Plateau and at Sites 744and 738 on the southern Kerguelen Plateau. The variation of these components reflects temporal changes in the deposi-tional history of the Kerguelen Plateau as well as major differences in the sedimentary evolution between the northernplateau and the southern plateau.

Carbonate is the dominant component in the pelagic sediments on the Kerguelen Plateau. In addition, biogenic opalsedimentation plays an important role throughout most of the sequence. A major increase in opal accumulation is doc-umented at all sites in late Miocene time, which is in accordance with the well-known increase in silica productivityprobably caused by a major cooling step. Because of its position near the Polar Frontal Zone, sediments from Site 737show a more extensive opal deposition than at Sites 744 and 738. An earlier productivity pulse is documented at Site 744on the southern plateau within the early Oligocene, following the initial phase of intense East Antarctic glaciation. Thiscooling event resulted in higher amounts of ice-rafted terrigenous quartz and, to a lesser extent, feldspar. With the ex-ception of the Site 744 sediments, opal deposition in Paleogene and older sediments can be reconstructed only from thediagenetic transformation products of opal-CT and probably clinoptilolite. In contrast to the southern sequence, on thenorthern Kerguelen Plateau higher amounts of clinoptilolite and no opal-CT were found. These major differences in thediagenetic environments may be due to extensive volcanism in the northern area. The volcanic influence at Site 737 iswell recorded by the higher feldspar content and higher amounts of volcanic glass shards.

INTRODUCTION

The Kerguelen Plateau is the worlcTs largest submarine pla-teau, about 2500 km in length and 200-600 km in width, stretch-ing from 46° to 64°S and 60° to 84°E in a generally northwest-southeast direction (Fig. 1). Cretaceous to Quaternary sedimentsfrom the Kerguelen Plateau were analyzed for bulk sedimentmineralogy of the carbonate-free fraction in order to investigatethe depositional and diagenetic history of the sediments. Site737 was used as the reference site on the northern KerguelenPlateau. Deposits from the southern tip of the Kerguelen Pla-teau were studied in a composite profile including sediments atSites 744 and 738. Our objective was to compare bulk mineral-ogical data from the sediment sequences of both the north andsouth parts of the submarine plateau, which are separated bymore than 10° latitude from each other.

Site 737 on the northern plateau is at 50°13.67'S, 73°01.95'E,in a water depth of 564 m (Fig. 1). Site 738 was drilled at62°42.54'S, 82°47.25'E, on the southern tip of the KerguelenPlateau in 2252 m water depth. In order to recover a more com-plete or more extended Eocene through Holocene section on thesouthern Kerguelen Plateau, Site 744 was cored in 2307 m waterdepth at 61°34.66'S, 80°35.46'E, 250 km north-northwest ofSite 738 (Fig. 1). Both sediment sequences are within the Ant-arctic Zone, which is bounded by the Polar Front to the northand the Continental Water Boundary to the south (Whitworth,1988). The northern Site 737 is close to the Polar Front, whichrepresents the southern limit of the Polar Frontal Zone. The Po-lar Frontal Zone marks the circumpolar current, which is the

1 Barron, J., Larsen, B., et al., 1991. Proc. ODP, Sci. Results, 119: CollegeStation, TX (Ocean Drilling Program).

2 Alfred-Wegener-Institut für Polar- und Meeresforschung, Columbusstraße,D-2850 Bremerhaven, FRG.

major oceanographic feature that separates the antarctic cold-water sphere from the warmer Subantarctic Zone. The southernsediment sequence documented at Sites 738 and 744 lies northof the Antarctic Divergence and thus may document changes ofthis oceanographic front through time.

MATERIAL AND METHODSBulk mineralogical data were obtained on selected samples

of the carbonate-free sediment fraction by X-ray diffraction(XRD). After freeze-drying, the samples were treated with hy-drogen peroxide and acetic acid to remove both organic matterand carbonate. Carbonate-free samples were mechanically groundand mixed with an internal standard of corundum (α-Al2O3) ata ratio of 2:1. Further grinding in an agate vial under acetoneenhanced homogenization. Randomly oriented, pressed-powdersüdes were X-rayed from 2° to 50° 20 with a speed of 0.005° 20/susing a Philips PW 1729 generator and CoKα radiation with anautomatic divergence slit and an automatic sample changer.

In order to quantify the quartz content of the sediments, theratio of the d(101) quartz peak height (at 3.343 Å) to the d(012)corundum peak height (at 3.479 A) was calculated. The abso-lute amount of quartz was then estimated from a standard curvebased on 11 mixtures of different amounts of quartz with amonomineralic matrix of smectite.

To measure the content of biogenic opal, we followed theXRD method of Eisma and van der Gaast (1971). Because bothbiogenic opal and volcanic glass show a broad, diffuse reflec-tion band as a result of their amorphous structure, some prob-lems of overlap exist. Therefore, we have not calculated opal-Avalues in samples containing noticeable amounts of volcanicglass.

Because a general calibration curve of clinoptilolite couldnot be established due to strong changes in d-spacing intensitiesby chemical variations (Boles, 1972), we give only the ratio ofthe intensity of the (020) clinoptilolite lattice to the intensity of

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G. BOHRMANN, W. U. EHRMANN

4050° 60

Crozet Island

4 0 0 0 ^Kerguelen Island

•African-

AntarcticBasin

Mean summer sea ice edge

Mean winter sea ice edge

Figure 1. Location of ODP Leg 119 Sites 737, 738, and 744 on the Kerguelen Plateau in the southern IndianOcean.

the internal standard. Semiquantitative estimates of feldspar,opal-CT, and barite are also given by peak height ratios to thatof the internal standard (d(012) corundum peak at 3.479 Å). Weused the feldspar reflection at 3.20 Å, the d(101) spacing ofopal-CT between 4.02 and 4.11 Å, and the d(121) lattice of bar-ite at 3.103 Å.

Carbonate data were taken from Ehrmann (this volume), in-cluding shipboard analyses (Barron, Larsen, et al., 1989).

LITHOLOGIC SEQUENCES AND STRATIGRAPHY

Site 737Six lithologic units were described at Site 737 (Barron, Lar-

sen, et al., 1989). The uppermost Unit I (0-1.5 m below seafloor

[mbsf]) consists of Quaternary mixed glauconitic sand and dia-tom ooze, overlying a 239-m-thick sequence of upper Mioceneto lower Pliocene diatom ooze (Unit II; 1.5-240 mbsf). In litho-logic Unit III (240-306 mbsf)> the carbonate content increasedas a result of the higher amounts of calcareous nannofossils,which changed the dominant sediment type to diatom-calcare-ous nannofossil ooze (Figs. 2 and 3). At 263 mbsf a hiatus cov-ering the time interval 8.2-10 Ma was found (Barron, Larsen, etal., 1989). Unit IV (306-321 mbsf) is a stratigraphically con-densed sequence in the middle Miocene consisting of a turbi-ditic sandy siltstone and calcareous nannofossil ooze with highamounts of volcanic components. The boundary of the under-lying unit is thought to be accompanied by a major hiatus cov-ering the interval from 15 to 23 Ma. Below this hiatus, a thick

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CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

Site 737564 mbsl

Site 7442307 mbsl

Site 7382252 mbsl

Legend

Diatom Ooze

Nannoiossil Ooze

Nannofossil Chalk

Chert

Sandy Siltstone

IΛ Λ ΛI

L». l Basement

Figure 2. General lithology and lithologic units of the stratigraphic record atODP Sites 737, 738, and 744.

calcareous claystone unit (Unit V; 321-668 mbsf) with variableamounts of carbonate (Fig. 3) was cored. This hemipelagic up-per Eocene to upper Oligocene sequence shows a lot of redepo-sition, although coarse-grained particles were not found in higheramounts (Barron, Larsen, et al., 1989). The lowest lithologicUnit VI, from 668 to 711 mbsf, is composed of middle Eocenepelagic clayey limestone containing some chert layers.

Sites 744 and 738

On the southern Kerguelen Plateau the Oligocene-Holocenesequence is best documented at Site 744; however, the sectionolder than Oligocene is well represented at Site 738. Sedimentsat Site 744 were subdivided into two lithologic units (Barron,Larsen, et al., 1989). The upper 23 m (Unit I) is an uppermostMiocene to Quaternary diatom ooze with variable amounts of

pelagic carbonate particles (Figs. 2 and 4). Below a hiatus thatspans the interval from 4.2 to 5.6 Ma (Baldauf and Barron, thisvolume), a thick pelagic unit of nannofossil ooze (Unit II; 23-176 mbsf) was cored, representing latest Eocene to late Miocenesedimentation. In comparison, the Oligocene to Quaternary sedi-ment sequence at Site 738 is quite incomplete. Quaternary touppermost Miocene diatom ooze (Unit I; 0-16.8 mbsf) and up-per Miocene nannofossil ooze (Unit II; 16.8-17.7 mbsf) overliea thick (17.7-120 mbsf) sequence of lower Oligocene to middleEocene homogeneous nannofossil ooze (lithologic Unit III). Theunderlying Unit IV at Site 738 (121-254 mbsf) is composed ofmiddle and lower Eocene nannofossil chalk and ooze contain-ing nodular cherts (Figs. 2 and 5). The lower Eocene to Maes-trichtian section is composed of chalk containing chert nodules(Unit V; 254-418 mbsf) Silicified Campanian to Turonian lime-

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G. BOHRMANN, W. U. EHRMANN

Site 737Clinoptilolite/Standard

1100(Carbonate-free)

200 400

F ldspar/Standard1100

(Carbonate- free

100 200I • I . I .

Figure 3. Lithology, age, carbonate content, and results from XRD investigations at Site 737. The semiquantita-tive patterns of the mineralogical data were calculated on a carbonate-free basis. Quartz contents were calculatedusing calibration curves. Feldspar is given by the ratio of the 3.2 Å peak to the (012) corundum peak × 100. Theciinoptiioiite pattern is based on the ratio of I(020) ciinoptiioiite t o kom corundum × 1 0 0

stone (Figs. 2 and 5; Unit VI; 418-480 mbsf) follows downcore.Intercalated between this pelagic unit and the volcaniclastic rocksand altered basalts of the basement (Unit VIII) is a thin clasticlimestone unit (Unit VII; 480-495 mbsf; Barron, Larsen, et al.,1989).

RESULTSClay minerals and carbonates and in some intervals opal-A

are the dominant components of the sediment analyzed. Basedon the XRD analyses we identified quartz, feldspar, opal-A,opal-CT, ciinoptiioiite, barite, and sporadic pyrite. Absolutecontents of quartz and opal-A and relative abundances of the

other minerals were obtained (Figs. 3 through 5 and AppendixTables 1 through 3).

Site 737

At Site 737 quartz, feldspar, opal-A, and ciinoptiioiite weredetected in higher amounts (Appendix Table 1) in the carbon-ate-free sediment fraction (Fig. 3). Barite reflections, which wereobserved in the sediments from Sites 744 and 738, were not de-tected.

The small amounts of opal-CT found in two intervals (119-737B-45R-1, 15-19 cm, and 119-737B-51R-1, 50-52 cm) are re-lated to the Eocene chert layers (Fig. 3). These chert samples are

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CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

SITE 744Feldspar/Standard

X100(Carbonate-free)

2 0 4 0 6 0 8 0

• • • • • • ' • '

Barite/Standardx 100

(Carbonate-free)

10 20 30 40

I i I i I i I i I

Opal-A (%)

(Carbonate-free)20 40 60 SO 100

Figure 4. Lithology, age, carbonate content, and results from XRD investigations at Site 744. The semiquantita-tive patterns of the mineralogical data were calculated on a carbonate-free basis. Opal-A and quartz contentswere calculated using calibration curves. Feldspar is given by the ratio of the 3.2 A peak to the (012) corundumpeak × 100. Barite was calculated by the ratio of I(121) barite

t o I<oi2) corundum × 1 0 ° .

also characterized by quartz contents of 12.5% and 24.9%, re-spectively (Fig. 3). Apart from these diagenetic beds, quartzcontents are consistently lower than 1% of the carbonate-freesediment. Higher quartz contents occur in variable amountsfrom 550 mbsf downcore (lowermost Oligocene through Eo-cene), between 250 and 320 mbsf (middle Miocene), and withinthe uppermost 70 m (Fig. 3).

Feldspar reflections were observed throughout the sedimen-tary column (Fig. 3). Higher intensity ratios (Ifeidspa/Icorundum)reflecting higher amounts of feldspar are present between Cores119-737A-27X and 119-737B-13R (247-324 mbsf; Appendix Ta-ble 1). This interval correlates well with the middle Miocene in-terval of enhanced quartz content (Fig. 3).

More than 50% biogenic opal (opal-A) in the carbonate-freeportion was usually detected in the uppermost 290 m. In someintervals contents up to 90% were measured (Fig. 3). From amaximum content at 160 mbsf, biogenic opal decreases down-hole to 20%-30% of the carbonate-free fraction. This decreasein the opal content is even more striking, if the opal content ofthe bulk sample is considered, because of the downhole dilutionby biogenic carbonate, which starts at 230 mbsf (Fig. 3). BelowCore 119-737B-9R we cannot estimate the opal-A content be-cause volcanic glass is present in higher amounts. Deeper than300 mbsf biogenic silica was found by microscopic examinationonly in small amounts (Barren, Larsen, et al., 1989). The highbiogenic opal contents and high amounts of volcanic glass are

also reflected by high dissolved silica concentrations in the porewater at Site 737 (Barron, Larsen, et al., 1989).

Clinoptilolite reflections are present in nearly all XRD sam-ples from lithologic Units V and VI from deeper than 380 mbsf.Average intensity ratios (Icimoptiioüte/̂ orundum) a re about 100 andmaximum values up to 330 were sporadically encountered. Cli-noptilolite was also found in Sample 119-737B-11R-2, 48-50cm, from Unit IV (Fig. 3).

Sites 744 and 738At Sites 744 and 738, quartz, feldspar, and barite were found

throughout the Upper Cretaceous to Holocene sediment se-quence, whereas opal-A, opal-CT, and clinoptilolite were foundonly in some intervals of the sediment sequence. With some ex-ceptions within the upper Miocene section (Site 744; Fig. 4),quartz contents are consistently higher than 2% in the carbon-ate-free fraction. At Site 738, the lowermost 250 m of sedimentsoverlying basement rocks contains enhanced amounts of quartz.The maxima of up to 28.7% (Fig. 5) are related to chert layers.The high concentration of 19.5% quartz in Sample 119-738B-3H-1, 125-129 cm, occurs in a section with a low sedimentationrate, above the hiatus at 18 mbsf, which separates lower Oligo-cene from upper Miocene sediments.

At Site 744, the carbonate-free sediment is characterized byhigher but more strongly fluctuating quartz contents than thoseanalyzed at Site 738 (Fig. 4). Maxima of up to about 10% quartz

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G. BOHRMANN, W. U. EHRMANN

SITE 738Opal-CT/

Feldspar/ Barite/ Standard% Quartz Standard Standard x 100;

% Carbonate x 100 x 100 Opal-A (%)(Carbonate-free) (Carbonalθ-free) (Carbonate-free) (Carbonate-free)

0 2 4 6 8 20 40 60 20 60 0 40 80

Clinoptilolite/Standard

X100(Carbonatθ-frθθ)

I 40 80

J I • I • I • I • I • I

Figure 5. Lithology, age, carbonate content, and results from XRD investigations at Site 738. The semiquantita-

tive patterns of the mineralogical data were calculated on a carbonate-free basis. Opal-A and quartz contents

were calculated using calibration curves. Opal-CT is given by the ratio of the opal-CT d(101) peak to the (012)

corundum peak × 100. Barite was calculated by the ratio of I(12i) bariteto 1(012) corundum × 1^0- The clinoptilolitepattern is based on the ratio of I(020) clinoptilolite t o !(0i2) corundum × 1 0 0

occur in the Oligocene, middle Miocene, and Pliocene. Thehighest quartz content (16.4%) was recorded in Sample 119-744A-16H-7, 47-49 cm, in lower Oligocene sediments.

The variation of feldspar content in the sediments at Sites744 and 738 is similar to the quartz pattern. With the exceptionof the Paleocene, the sediments older than early Oligocene showaverage intensity ratios (Ifeidspa/Icomndum) of about 1000 (Site 738;Fig. 5). In the younger sediments at Site 744, the feldspar inten-

sities increase slightly. Maxima with values of up to 8000 wereobserved in the middle Miocene and Pliocene, and minima withinthe upper Miocene (Fig. 4).

Barite was identified in all samples at Sites 738 and 744. Therelative downhole variation is shown by the I(121) bante^ou) corundumratio (Figs. 4 and 5). Average values of about 3000 are recordedfrom the Upper Cretaceous to the Paleocene at Site 738 (Fig. 5).Within the lower and middle Eocene, barite concentrations

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CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

reach values between 5000 and 6000 (Fig. 5) and are 3000-4000within the upper Eocene to middle Miocene, with interruptionswithin the lower Oligocene (Figs. 4 and 5). The lowest values arefound in the late Miocene record (below 500; Fig. 4) and withinthe post-Miocene sediments (1000-2000; Fig. 4).

Opal-A was not detected by XRD analyses in sediments olderthan late Eocene (Fig. 5). The small amounts of biogenic opal,less than 20% on a carbonate-free basis, in the upper Eocenesediments at Site 744 were not recorded at Site 738. Opal-A con-tents reach an early maximum of 60% in Cores 119-744A-15Hand 119-744A-16H within the lower Oligocene. This maximumis also documented by higher contents of dissolved silica in thepore water (Cranston, this volume). Between 50 and 120 mbsf(upper Oligocene to middle Miocene; Fig. 4) opal contents re-main low (0%-30%) and shift to high amounts (>90%) withinthe upper Miocene. In the post-Miocene section, the sedimentsare still biogenic silica-bearing, and with the exception a valueof approximately 20% in Sample 119-744A-3H-1, 49-51 cm,opal contents reach about 80%.

At Site 738, opal-CT reflections were documented below 100mbsf, and fluctuating concentrations in the semiquantitative dis-tribution pattern are shown in Figure 5. The highest values arereached within measurements of four chert nodules, which alsoshow high quartz contents (Fig. 5). Clinoptilolite was found atSite 738 in Cretaceous to upper Eocene sediments (40-480 mbsf;Fig. 5) and shows maximum intensity ratios (Iciinoptiioiite/Icorundum)of 300-1000 (Fig. 5) between 270 and 370 mbsf (Paleocene tolower Eocene) and between 100 and 120 mbsf (within the middleEocene).

DISCUSSIONThe detailed mineral composition and semiquantitative esti-

mates of some mineral components obtained by XRD analysesshould provide additional information about the evolution ofthe depositional environment and sedimentary processes. Be-cause calcareous skeletons, such as foraminifers and calcareousnannofossils, were usually found, with the exception of the up-per Miocene to lower Pliocene diatom ooze, the sediments weredeposited in a well-oxygenated environment above the calcitecompensation depth, which lies today at 5200 m below sea level(Van Andel et al., 1975). Biogenic silica (opal-A) and most ofthe biogenic carbonate are of pelagic origin.

Quartz and FeldsparThe sharp and short-lived quartz peak in the lower Oligocene

sediments at Site 744 correlates with a weak maximum of feld-spar (Fig. 4), enhanced concentrations of nonbiogenic matter,and a maximum in the gravel and terrigenous sand content(>63 µm) of the sediments (Ehrmann, this volume). It furthercoincides with a minimum in the carbonate concentrations andthe onset of opal-A accumulation. This event is interpreted asthe initial phase of intense East Antarctic glaciation, which re-sulted in an influx of large amounts of ice-rafted debris and dis-solution of carbonate, probably due to the generation of coldand aggressive bottom waters (Ehrmann, this volume).

From the early Oligocene to Holocene time, ice rafting hasinfluenced sedimentation on the southern Kerguelen Plateau.The ice-rafted gravel and sand component on the southern Ker-guelen Plateau is composed mainly of gneissic and, in minoramounts, of granitic material derived from the East Antarcticcontinent (Ehrmann, this volume). A strong correlation betweenquartz and feldspar concentrations, therefore, can be expected.Maxima in the quartz and feldspar concentrations at Site 744occur in the upper lower Oligocene to lower Miocene, middleMiocene, and Pliocene (Fig. 4). They correlate with maxima inthe grain-size distribution of terrigenous sand and silt (Ehrmann,

this volume) and therefore may reflect phases of enhanced sedi-ment input by ice rafting rather than pure dilution effects by en-hanced influx of biogenic opal.

In contrast, no clear correlation between quartz and feldsparcan be observed in sediments older than early Oligocene, andtheir concentrations in the carbonate-free sediment fraction aregenerally lower than in younger sediments (Fig. 5). An input byice rafting plays no or only a very minor role down to middleEocene sediments and can be excluded in the remaining sequence(Barron, Larsen, et al., 1989; Ehrmann, this volume). Instead,at least some of the quartz in the deeper part of Site 738 is ofauthigenic origin. Authigenic quartz becomes most obvious inthe chert nodules occurring at Site 738 between 120 and 480mbsf (Fig. 5). The enhanced quartz concentrations below 250mbsf may be due in part to sand- and silt-sized chert fragments,which were generated during rotary drilling and smeared alongthe core liner during coring and along the cut surface duringsplitting of the cores (Ehrmann, this volume). However, thepresence of opal-CT at this level is an indicator for the diage-netic formation of siliceous minerals and favors an authigenicquartz component.

At Site 737 on the northern Kerguelen Plateau, the back-ground level of feldspar concentrations is about twice as high ason the southern plateau (Fig. 3). Quartz, in contrast, generallyoccurs in much lower minor concentrations than at Sites 738and 744. A different source or different transport mechanismscould be responsible for this. Ice rafting from Antarctica shouldplay only a minor role in this distal setting. The proximity to thevolcanic rocks of Kerguelen Island implies an input of volcano-genie material and can explain the enhanced feldspar and re-duced quartz background concentrations. Maximum feldsparconcentrations occur at 240-330 mbsf (Fig. 3), in middle andlowermost upper Miocene sediments, which are characterizedby a high amount of volcanic rock fragments (Barron, Larsen,et al., 1989) and volcanic glass. The co-occurrence of sand-sizedquartz grains, however, also could imply an ice-rafted origin forthis material. For the quartz maximum at 550-710 mbsf, an as-sumed authigenic origin of the quartz is supported by the factthat the sediment is highly altered by diagenesis; most of the mi-cro fossils are silicified, and some chert nodules occur from 697mbsf downhole (Barron, Larsen, et al., 1989). However, the oc-currence of some sand-sized quartz grains makes this originquestionable. The lack of a related feldspar maximum contra-dicts the idea of an ice-rafted origin.

BariteBarite, most common mineral of barium, is widespread in

deep-sea sediments (Arrhenius and Bonatti, 1965; Church, 1979;Schmitz, 1987). The source of barium in deep-sea sediments isstill under discussion. Barite is associated with hydrothermal ac-tivity (Boström et al., 1973; Church, 1979) and also with higherbiological productivity in equatorial regions (e.g., Schmitz, 1987).The observations of Bishop (1988) support the hypothesis thatbarite precipitation occurs partly within the water column in mi-croenvironments that are enriched in sulfate from decaying or-ganic matter, such as fecal pellets and diatom frustules. This in-vestigation may partly explain the commonly reported correla-tion of biogenic silica and barite in deep-sea sediments (Schmitz,1987; Bishop, 1988).

The barium cycle in the ocean, however, is even more com-plex (e.g., barite can be dissolved as well as precipitated duringdiagenesis; Bishop, 1988). Barite dissolution was reported fromsediments rich in organic carbon in the Gulf of California byBrumsack (1989). There, the marked increase in Ba concentra-tions in the pore water below the sulfate reduction zone indi-cates barite dissolution. However, this barite dissolution seemsto occur in very low sulfate pore-water concentrations.

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G. BOHRMANN, W. U. EHRMANN

At Site 737, sulfate concentration in the interstitial watersgradually decreases from 27 mmol/L at the top of the section to15 mmol/L at the base. At Site 738, interstitial water analysesreveal sulfate concentrations between 23 and 26 mmol/L (Bar-ron, Larsen, et al., 1989). The sulfate concentrations of the in-terstitial waters throughout the sediments at Site 744 are essen-tially the same as in seawater (Barron, Larsen, et al., 1989). Theamount of reactive organic matter incorporated into the sedi-ments was sufficient to produce anaerobic conditions and a smallsulfate reduction that is taking place over a large depth range,but is too small to exhaust the available sulfate supply. There-fore, sulfate concentrations in the sediments studied here shouldbe high enough throughout to prevent the dissolution of barite.

Barite was not found on the northern Kerguelen Plateau atSite 737, however, and seems to be restricted to the southernarea, where it was found in higher amounts at both Sites 738and 744 (Figs. 5 and 6). Because we may exclude barite dissolu-tion at Site 737, as discussed previously, we have to explain theorigin of barite on the southern Kerguelen Plateau in anotherway. At Site 744, the records of barite and biogenic opal areanticorrelated (Fig. 4), which argues against a biogenic input ofbarite, as is well known from the Central Indian Ocean (Schmitz,1987). Other explanations include either diagenetic precipitationor a terrigenous source close to the Antarctic continent, whichreached only the southern Kerguelen Plateau. On land, the prin-cipal sources for barite are hydrothermal veins, cavity fillings,and concretions in sediments. Because detailed electron micro-scopic examinations were not performed on the barite fraction,we were unable to distinguish between terrigenous barite anddiagenetic barite.

Biogenic OpalBelow Core 119-737B-9R we cannot estimate the opal-A con-

tents at Site 737 because higher amounts of volcanic glass arepresent. The occurrence of volcanic glass is well documented bya distinct change in morphology and the maximum height ofthe silica bulge. In the uppermost 290 mbsf the maximum of thebulge lies between 4.0 and 4.04 Å. Within the sediment sectionfrom 302 to 371 mbsf a reflection bulge formed at about 3.6 to3.7 Å is also characterized by a much lower intensity. The abruptchange in bulge type from one sample to the other correlateswith a change in the sediment from high amounts of opal-Aabove to high amounts of volcanic glass below. This interpreta-tion cannot be concluded from the position of the silica bulgealone, because van Bennekom et al. (1988) have described re-flection bulges of opal-A that shifted from 4.0 to 3.7 Å as a re-sult of the incorporation of aluminum into the opaline struc-ture. But the intensity values of the silica bulge in relationshipto the other reflections observed in the samples between 302 and371 mbsf indicate the nature of volcanic glass, which is also inaccordance with the smear slide observations of Barron, Lar-sen, et al. (1989).

Despite these difficulties in opal-A determination, two ma-jor steps in biogenic silica increase are best documented at Site744. A short but distinct interval of high biogenic silica well de-fined in the lower Oligocene at Site 744 (Fig. 4) is less developedat Site 738 (Fig. 5), probably because of diagenetic alteration(e.g., clinoptilolite formation). The increase of biogenic silicaoccurred just after the initial phase of intense East Antarcticglaciation (Ehrmann, this volume). This distinct cooling event isrecorded at Site 744 by different parameters, such as a decreasein carbonate content (Ehrmann, this volume) and a sharp in-crease of quartz content (Fig. 4), as discussed previously. In re-sponse to this climatic change during the reorganization of ant-arctic oceanography, the high productivity of opaline phyto-plankton resulted in a higher opal-A accumulation.

A much stronger late Miocene shift to higher opal contents isrecorded in the sequences on both the northern (Fig. 3) and

southern (Fig. 4) Kerguelen Plateau. This increase also marks amajor change in the paleoceanographic pattern during the Ce-nozoic. High opal-accumulation rates are well recorded at Site737 (Fig. 3) near the Polar Frontal Zone, which today is thedominant oceanographic feature responsible for high silica sedi-mentation in the Southern Ocean.

Authigenic Silicate Formation

ClinoptiloliteClinoptilolite is a K-rich zeolite of the heulandite family, and

is commonly reported, in addition to phillipsite (Kastner andStonecipher, 1978), in deep-sea sediments (McCoy et al., 1977;Kastner and Stonecipher, 1978; Riech and von Rad, 1979; Theinand von Rad 1987; Bohrmann et al., 1989). Such zeolites aregenerally of diagenetic origin, although a common diageneticevolution for zeolites is not generally accepted. Based on thedistribution pattern of phillipsite and clinoptilolite through time,Kastner and Stonecipher (1978) assumed that phillipsite in theyounger sediments of the Pacific Ocean is the precursor of theclinoptilolite found in older sediments. There are numerous ob-servations of the relationship of clinoptilolite formation and bi-ogenic silica diagenesis in the Atlantic Ocean (Berger and vonRad, 1972; Riech and von Rad, 1979; Fenner, 1981; Thein andvon Rad, 1987; Bohrmann et al., 1989).

Clinoptilolite precipitates from pore water in the presence ofalkalines and earth alkalines if sufficient Al is combined with ahigh level of dissolved silica. Clinoptilolite precipitation occursat Site 738 in sediments older than Oligocene and at Site 737 inthe Oligocene and Eocene, which is in close accordance withother occurrences of clinoptilolite in deep-sea sediments (Kast-ner and Stonecipher, 1978).

Below 372 mbsf at Site 737, there is a sharp decrease in inter-stitial silica concentrations from more than 1000 µmol/L in theoverlying sediments to values of about 300 µmol/L (Barron,Larsen, et al., 1989), which corresponds well with the beginningof the downhole occurrence of clinoptilolite (Fig. 3). The con-centrations of dissolved silica seem to be depleted by clinoptilo-lite formation below this depth at Site 737. Similar correlationsof silica concentrations in interstitial waters and clinoptilolitecontent are documented at Site 738 (Fig. 5), although they areless obvious as a result of the generally high carbonate concen-trations at Site 738.

According to Stonecipher (1978), clinoptilolite formationshould be enhanced in carbonate-rich sediments. In contrast,our results show that clinoptilolite contents are distinctly higherin the sediments at Site 737 (Fig. 3) than at Site 738 (Fig. 5),where carbonate contents are clearly higher. Beside clinoptilo-lite, opal-CT was precipitated from pore water as a further silicaphase in the sediments at Site 737. This precipitation, with theexception of two samples (Fig. 5), was not observed at Site 738.Opal-CT precipitation in sediments clearly requires elevated Si/Alratios in interstitial water composition (Williams and Crerar,1985). Thus, an opal-CT precipitation simultaneously leads tolower Si/Al, which could favor clinoptilolite formation afteropal-CT precipitation at Site 738. We assume that the increasedavailability of Al, K, and Ca to the pore water at Site 737 causedextensive clinoptilolite growth. This abundance of Al, earth al-kalines, and alkalines in the interstitial water could be due to thedissolution of volcanic components. Volcanogenic detritus ismore abundant at this site from the northern Kerguelen Pla-teau, as documented by the higher feldspar contents (Fig. 5).

Opal-CTOpal-CT was found in higher amounts only at Site 738, and

maximum values are documented in cherts, which clearly are fa-vored sites for silica precipitation. Opal-CT is well establishedas an intermediate silica phase within the maturation sequence

218

CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

from opal-A to quartz (Williams and Crerar, 1985). The trans-formation of opal-A to opal-CT and then to quartz has beenrecognized in numerous sediment sections of the Atlantic Ocean(Riech and von Rad, 1979; Thein and von Rad, 1987; Bohr-mann and Stein, 1989), the Indian Ocean (Hempel and Bohr-mann, in press), and the Pacific Ocean (Keene, 1975; Hein etal., 1978), as well as in onshore sections (Iijima and Tada, 1981;Tada and Iijima, 1983; Murata and Randall, 1975; Pisciotto,1981). Experimental investigations also support this transfor-mation sequence (Mizutani, 1977; Kastner et al., 1977). Besidehost rock lithology and interstitial water chemistry, time andtemperature are the most important factors controlling the trans-formation of silica phases (Murata and Randall, 1975; Hein etal., 1978; Tada, in press). The transformation of silica phasesoccurs at lower temperatures in older sediments, whereas lesstime is required for transformation at higher temperatures (Heinet al., 1978). From the Southern Ocean Bohrmann et al. (1990)reported opal-CT-cemented rocks of young age and low burialrate where higher temperatures were not observed.

Opal-CT formation at Site 738 is in accordance with the gen-erally accepted concepts of opal-CT as a maturation process(Williams and Crerar, 1985). This is further supported by thegeneral downhole decrease of opal-CT d(101) spacing from 4.10to about 4.05 Å (Fig. 6). Although some deviations occur, prob-ably due to different host rock lithologies (Isaacs, 1982) and dif-ferent generations in diagenetic evolution (Iijima and Tada, 1981),the general trend to lower values is quite obvious. This trendshows an increased ordering of opal-CT during diagenesis, whichis also well supported by the hydrothermal experiments con-ducted by Mizutani (1977).

Because the formation of opal-CT is possible only when con-siderable amounts of biogenic opal have been deposited, we canassume that higher amounts of biogenic silica skeletons musthave been deposited during most of the interval between theLate Cretaceous and Eocene. Because dissolved silica may mi-grate with pore water vertically and opal-CT precipitation oc-curs preferentially at favored sites, the productivity of biogenicopal cannot be deduced to correspond to opal-CT precipitation.

ACKNOWLEDGMENTS

We appreciate the help in sampling by the shipboard scien-tific party and ODP technical staff aboard JOIDES Resolution.Financial support was provided by the "Deutsche Forschungs-gemeinschaft" (Grant No. Fu 119/15). Anke Hienen, Rita Fröhlk-ing, Imke Engelbrecht, and Helga Rhodes are appreciated fortheir technical assistance. This is Contribution No. 323 of theAlfred Wegener Institute for Polar and Marine Research.

REFERENCES

Arrhenius, G., and Bonatti, E., 1965. Neptunism and vulcanism in theocean. In Sears, M. (Ed.), Progress in Oceanography: London (Perga-mon Press), 3:7-22.

Barron, J., Larsen, B., et al., 1989. Proc. ODP, Init. Repts., 119: Col-lege Station, TX (Ocean Drilling Program).

Berger, W. H., and von Rad, U., 1972. Cretaceous and Cenozoic sedi-ments from the Atlantic Ocean. In Hayes, D. E., Pimm, A. C , etal., Init. Repts. DSDP, 14: Washington (U.S. Govt. Printing Of-fice), 787-954.

Bishop, J.K.B., 1988. The barite-opal organic carbon association inoceanic paniculate matter. Nature, 332:341-343.

Bohrmann, G., Kuhn, G., Abelmann, A., Gersonde, R., and Fütterer,D., 1990. A young porcellanite occurrence from the Southwest In-dian Ridge. Mar. Geol., 92:155-163.

Bohrmann, G., and Stein, R., 1989. Biogenic silica at ODP Site 647 inthe southern Labrador Sea: occurrence, diagenesis, and paleoceano-graphic implications. In Srivastava, S. P., Arthur, M., Clement, B.,et al., Proc. ODP, Sci. Results, 105: College Station, TX (OceanDrilling Program), 155-170.

Bohrmann, G., Stein, R., and Faugères, J.-C, (1989). Authigenic zeo-lites and their relation to silica diagenesis in ODP Site 661 sediments(Leg 108, eastern equatorial Atlantic). Geol. Rundsch., 78:779-792.

Boles, J. R., 1972. Composition, optical properties, cell dimension, andthermal stability of some heulandite group zeolites. Am. Mineral,57:1463-1493.

Boström, K., Joensuu, D., Moore, C , Boström, B., Dalziel, M., andHorowitz, A., 1973. Geochemistry of barium in pelagic sediments.Lithos, 6:159-174.

Brumsack, H. J., 1989. Geochemistry of recent TOC-rich sedimentsfrom the Gulf of California and the Black Sea. Geol. Rundsch., 78:851-882.

Church, T. M., 1979. Marine barite. In Burns, R. G. (Ed.), Reviews inMineralogy (vol. 6): Mineral Soc. Am., 175-209.

Eisma, D., and Van der Gaast, S. J., 1971. Determination of opal inmarine sediments by X-ray diffraction. Neth. J. Sea Res., 5:382-389.

Fenner, J., 1981. Diatoms in the Eocene and Oligocene sediments offNW Africa, their stratigraphic and paleogeographic occurrences[Ph.D. dissert.]. Univ. Kiel, FRG.

Hein, J. R., Scholl, D. W., Barron, J. A., Jones, M. G., and Miller, J.,1978. Diagenesis of late Cenozoic diatomaceous deposits and for-mation of the bottom simulating reflector in the southern BeringSea. Sedimentology, 25:155-181.

Hempel, P., and Bohrmann, G., in press. Carbonate-free sediment com-ponents and aspects of silica diagenesis at Sites 707, 709, and 711(Leg 115, western Indian Ocean). In Backman, J., Duncan, R. A., etal., Proc. ODP, Sci. Results, 115: College Station, TX (Ocean Drill-ing Program).

Iijima, A., and Tada, R., 1981. Silica diagenesis of Neogene diatoma-ceous and volcaniclastic sediments in northern Japan. Sedimentol-ogy, 28:185-200.

Isaacs, C. M., 1982. Influence of rock compositions on kinetics of silicaphase changes in the Monterey Formation, Santa Barbara area, Cali-fornia. Geology, 10:304-308.

Kastner, M., Keene, J. B., and Gieskes, J. M., 1977. Diagenesis of sili-ceous oozes. I. Chemical controls on the rate of opal-A to opal-CTtransformation—an experimental study. Geochim. Cosmochim. Acta,41:1041-1059.

Kastner, M., and Stonecipher, S.A., 1978. Zeolites in pelagic sedimentsof the Atlantic, Pacific, and Indian oceans. In Sand, L. B., andMumpton, F. A. (Eds.), Natural Zeolite: Occurrence, Properties,Use: New York (Pergamon Press), 199-218.

Keene, J. B., 1975. Cherts and porcellanites from the North Pacific,DSDP Leg 32. In Larsen, R. L., Moberly, R., et al., Init. Repts.DSDP, 32: Washington (U.S. Govt. Printing Office), 429-507.

McCoy, F., Zimmerman, H., and Krinsley, D., 1977. Zeolites in SouthAtlantic deep-sea sediments. In Supko, P. R., Perch-Nielsen, K., etal., Init. Repts. DSDP, 39: Washington (U.S. Govt. Printing Of-fice), 423-443.

Mizutani, S., 1977. Progressive ordering of cristobalitic silica in theearly stage of diagenesis. Contrib. Mineral. Petrol., 61:129-140.

Murata, K. J., and Randall, R. G., 1975. Silica mineralogy and struc-ture of the Monterey Shale, Temblor Range, California. J. Res. U.S.Geol Survey, 3:567-572.

Pisciotto, K. A., 1981. Distribution, thermal histories, isotopic compo-sitions, and reflection characteristics of siliceous rocks recovered bythe Deep Sea Drilling Project. In Warme, J. E., Douglas, R. G., andWinterer, E. L. (Eds.), The Deep Sea Drilling Project: A Decade ofProgress. SEPM Spec. Publ., 32:129-148.

Riech, V., and von Rad, U., 1979. Silica diagenesis in the Atlantic Ocean:diagenetic potential and transformations. In Talwani, M., Hay, W,and Ryan, W.B.F. (Eds.), Deep Drilling Results in the Atlantic Ocean:Continental Margins and Paleoenvironment: Am. Geophys. Union,Maurice Ewing Ser., 3:315-340.

Schmitz, B., 1987. Barium, equatorial high productivity, and the north-ward wandering of the Indian continent. Paleoceanography, 2:63-77.

Stonecipher, S. A., 1978. Geochemistry and deep-sea phillipsite, clinop-tilolite, and host sediments. In Sand, L. B., and Mumpton, F. A.(Eds.), Natural Zeolite: Occurrence, Properties, Use: New York(Pergamon Press), 221-234.

Tada, R., in press. Compaction and cementation in siliceous rocks andtheir possible effects on bedding enhancement. In Cycles and Eventsin Stratigraphy: (Springer).

219

G. BOHRMANN, W. U. EHRMANN

Tada, R., and Iijima, A., 1983. Petrology and diagenetic changes of Ne-ogene siliceous rocks in northern Japan. J. Sediment. Petrol., 53:911-930.

Thein, J., and von Rad, U, 1987. Silica diagenesis in continental riseand slope sediments off eastern North America (Sites 603 and 605,Leg 93; Sites 612 and 614, Leg 95). In Poag, C. W., Watts, A. B., etal.( Init. Repts. DSDP, 95: Washington (U.S. Govt. Printing Of-fice), 501-525.

Van Andel, T. H., 1975. Mesozoic/Cenozoic calcite compensation depthand the global distribution of calcareous sediments. Earth Planet.Sci. Lett., 26:187-194.

van Bennekom, A. J., Jansen, J.H.F., van der Gaast, S. J., van Iperen,Y. M., and Pieters, J., 1988. Aluminium-rich opal: an intermediatein the preservation of biogenic silica in the Zaire (Congo) deep-seafan. Deep-Sea Res., Part A, 36:173-190.

Whitworth, T., Ill, 1988. The Antarctic Circumpolar Current. Oceanus,31:53-58.

Williams, L. A., and Crerar, D. A., 1985. Silica diagenesis, II. Generalmechanisms. J. Sediment. Petrol., 55:313-321.

Date of initial receipt: 6 February 1990Date of acceptance: 22 June 1990Ms 119B-122

Site 738

Opal-CT d(101) spacing (A)

4.02 4 • 0 6 4 • 1 0

100

200

300 -

α.

a4 0 0 •i

500

Figure 6. Variation of opal-CT d(101) spacing with depth in sedimentsfrom ODP Site 738.

220

CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

Appendix Table 1. Results from X-ray-diffraction analyses (based on the carbonate-free sample) ofsediments from Site 737.

Core, section,interval (cm)

119-737A-

1H-2, 48-502H-7, 36-403H-7, 48-524H-7, 48-525H-2, 48-506H-2, 56-606H-4, 60-647H-2, 48-509H-2, 48-509H-7, 48-5210H-2, 48-5211H-2, 48-5011H-7, 12-1612H-7, 10-1413H-5, 48-5015H-5, 24-2816H-6, 78-8217H-3, 48-5218H-2, 48-5218H-7, 30-3419X-1, 48-5023X-1, 48-5225X-3, 10-1426X-2, 4-827X-3, 46-5028X-1, 100-102

119-737B-

6R-1, 126-1306R-5, 10-127R-1, 48-528R-1, 58-629R-1, 38-4210R-1, 38-4211R-2, 48-5012R-3, 58-6013R-1, 48-5014R-4, 56-5815R-4, 50-5216R-3, 50-5217R-2, 50-5218R-1, 48-5019R-2, 48-5020R-4, 52-5421R-2, 50-5222R-7, 48-5024R-3, 49-5125R-2, 44-4826R-4, 50-5227R-2, 70-7229R-4, 60-6230R-4, 58-6031R-4, 50-5233R-1, 37-3934R-1, 51-5334R-5, 48-5235R-3, 48-5036R-2, 134-13837R-3, 50-5238R-4, 44-4639R-4, 56-5840R-1, 77-7941R-4, 54-5642R-3, 51-5344R-4, 49-5145R-1, 15-1946R-1, 100-10247R-2, 100-10248R-2, 100-10249R-4, 95-975OR-3, 52-5451R-1, 50-5252R-3, 50-52

Depth(mbsf)

1.9814.0923.5232.9335.4845.0648.1054.4873.4880.6282.9892.4899.44

108.67115.98134.74146.04150.91158.98166.12166.98205.78227.80235.94247.56254.80

264.46269.30273.38283.08292.58302.18313.48324.68331.28345.46355.10363.30371.40379.58390.68403.42410.10427.09440.49448.64460.40468.20490.40500.08509.60524.37534.11540.08546.78555.74566.00577.14586.81592.27606.14614.21634.99639.75650.30661.10670.40683.05690.02696.70709.40

Carbonate

0.162.141.130.092.501.950.290.030.596.632.360.340.260.470.170.890.700.150.390.24

10.010.00

0.138.01

16.76

77.6778.3496.7179.7762.6044.2683.2331.8919.3239.77

8.1625.7626.0020.8720.8810.2111.3621.8839.7434.1849.4218.7526.6543.4054.3757.5624.96

18.4123.3712.2436.6055.4739.3435.4938.9851.9983.8773.096.84

84.4170.5451.6989.4383.80

Quartz(%)

1.900.100.970.200.100.440.100.320.100.094.350.070.050.100.050.230.050.080.100.030.020.080.530.102.320.56

0.300.721.170.350.051.003.070.090.520.050.060.040.030.270.010.010.020.010.010.350.020.030.000.010.010.010.020.020.010.810.012.592.760.832.540.910.98

12.463.190.011.861.421.39

24.962.21

Feldspar/standard(× 100)

35.123.926.425.740.129.627.031.035.224.043.115.617.115.815.526.214.536.710.415.416.117.525.110.5

695.849.0

15.427.745.633.816.952.044.2

164.8102.6

15.114.811.713.625.111.312.313.630.621.718.626.717.912.17.4

18.37.8

19.715.129.619.823.822.524.620.824.015.823.023.028.0

6.07.05.99.0

14.410.4

Clinoptilolite/standard(× 100)

0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

0.00.00.00.00.00.0

83.50.00.00.00.00.00.0

54.182.2

132.0215.1130.8116.653.288.7

180.845.617.441.8

100.07.1

95.556.8

108.9244.8175.7110.9145.492.5

194.097.3

102.3331.340.049.652.760.032.6

117.2

Opal-A(%)

07183665548584545702485677380567160928184506051

45

3457222780

Remarks

Volcanic glass?

Volcanic glassVolcanic glassVolcanic glassVolcanic glassVolcanic glassVolcanic glassVolcanic glassVolcanic glass

Chert (opal-CT)

Chert (opal-CT)

221

G. BOHRMANN, W. U. EHRMANN

Appendix Table 2. Results from X-ray-diffraction analyses (based on the carbonate-free sample) of sediments from Site 738.

Core, section,interval (cm)

119-738B-

3H-1, 125-1293H-5, 48-524H-3, 48-524H-5, 78-824H-7, 30-345H-1, 100-1045H-3, 48-525H-7, 30-347H-5, 48-528H-5, 48-529H-3, 48-5210H-3, 48-5211H-3, 48-5211H-5, 48-5212H-3, 48-5213H-1, 48-5213H-3, 48-5214X-3, 48-5215X-3, 48-5217X-1, 60-6418X-1, 48-5218X-3, 48-522OX-3, 48-5221X-1, 48-5222X-1, 48-5222X-3, 48-5224X-2, 48-52

119-738C-

4R-3, 48-525R-1, 46-507R-2, 74-767R-2, 90-9210R-2, 8-1010R-2, 36-3811R-3, 10-1216R-1, 48-5216R-5, 42-4416R-5, 54-5817R-1, 58-6018R-1, 70-7418R-6, 48-5219R-2, 70-7420R-1, 20-2420R-2, 50-5422R-2, 62-6522R-5, 51-5323R-2, 47-4924R-2, 60-6224R-3, 50-5225R-1, 64-6625R-3, 56-6025R-3, 72-7426R-2, 54-5627R-1, 49-5128R-1, 55-5728R-3, 48-5029R-2, 48-5030R-2, 48-50

Depth(mbsf)

14.7519.9826.3529.5231.9433.4635.8541.4457.7967.2973.9883.4888.4891.4897.98

104.47107.17111.68121.28137.80147.28150.28169.68176.28185.88188.88206.58

219.38226.06247.04247.20275.38275.66286.50332.08338.02338.14341.86351.60358.88362.70370.40372.20391.72396.40401.17411.00412.40419.24422.16422.32430.24438.39448.15451.08459.18468.58

Carbonate(%)

0.087.392.292.790.489.889.294.090.693.494.095.3

93.394.293.692.091.293.191.594.593.396.795.894.994.995.3

93.194.293.6

92.292.492.591.1

92.897.199.298.394.796.194.294.990.786.483.185.2

88.587.789.792.986.684.684.6

Quartz( « )

19.55.02.02.22.52.81.52.32.31.71.31.42.21.81.22.01.61.51.41.00.91.11.41.41.51.41.1

1.11.21.3

12.012.42.82.84.12.5

23.22.01.72.42.01.72.32.73.53.12.03.02.8

28.72.72.52.12.02.01.61.2

Feldspar/standard(× 100)

0.014.60.00.05.9

22.04.5

11.710.814.014.616.212.010.110.90.0

15.212.60.09.1

14.40.00.07.90.08.70.0

0.00.00.00.00.0

18.321.610.913.10.0

116.011.514.70.0

12.911.812.00.0

13.00.08.6

10.90.0

10.010.710.90.00.00.00.0

Barite/standard(× 100)

11.825.545.936.734.837.226.739.531.738.439.461.754.452.644.938.646.054.241.731.831.533.345.638.834.929.446.8

57.677.234.40.00.0

28.423.328.935.00.0

23.423.668.833.934.532.923.841.026.617.825.525.00.0

21.431.833.330.830.447.524.7

Opal-A(%)

333015

1324

0

Opal-CT/standard(× 100)

0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

34.636.90.0

43.10.00.00.00.00.00.00.0

29.1

30.18.8

19.897.0

116.815.716.928.330.080.651.034.227.228.136.30.0

57.418.111.273.459.731.587.223.013.528.69.5

11.732.90.0

Opal-CTd(101)

(Å)

4.1014.099

4.108

4.091

4.0874.1054.0894.1114.1044.1034.1054.1014.0724.0984.0804.0894.0924.0904.089

4.0924.0614.0504.0974.0804.0624.0744.0714.0724.0724.0554.0334.082

Clinoptilolite/standard(× 100)

0.00.00.00.00.00.00.0

16.421.131.433.621.615.714.238.360.847.653.334.50.00.0

13.49.66.80.00.0

12.8

8.722.4

6.70.00.0

100.070.937.740.6

0.037.764.168.879.432.434.40.07.6

33.76.49.60.00.06.5

47.26.3

11.57.0

17.643.8

Remarks

SmectitesChertChert

Chert

Chert

222

CRETACEOUS TO QUATERNARY SEDIMENTS: SITES 737, 738, AND 744

Appendix Table 3. Results from X-ray-diffraction analyses (based on the car-bonate-free sample) of sediments from Site 744.

Core, section,interval (cm)

119-744A-

1H-1, 49-511H-3, 49-512H-1, 49-512H-4, 49-513H-1, 49-513H-4, 49-514H-2, 46-504H-3, 40-445H-2, 40-445H-4, 12-156H-2, 60-646H-4, 49-517H-2, 46-507H-3, 46-507H-4, 49-518H-2, 46-508H-3, 46-508H-4, 49-519H-1, 49-5110H-2, 46-5010H-7, 48-5211H-3, 48-5211H-6, 48-5212H-3, 48-5212H-6, 46-5013H-6, 46-5014H-6, 46-5015H-3, 46-5015H-6, 46-5016H-2, 46-5016H-5, 46-5016H-7, 47-4918H-1, 49-5119H-1, 49-5119H-6, 46-5020H-1, 42-4620H-5, 46-50

Depth(mbsf)

0.493.494.699.19

14.1918.6925.1626.6034.6037.3244.3045.6653.6655.1659.4063.1664.6666.1971.1981.6089.3293.1897.68

102.55106.85116.58126.16131.06135.43139.09143.41146.31148.08157.59165.06167.00172.81

Carbonate(%)

29.8260.9662.6932.5729.01

3.9189.8691.0181.6073.4386.4491.3882.8779.7377.4778.3282.2484.0093.4590.1590.5289.0383.1889.7689.4791.1988.6587.7488.9687.1482.0161.2691.8293.7890.7888.6094.61

Quartz(%)

2.74.02.53.8

10.85.41.73.32.01.10.41.87.87.49.26.1

10.65.83.22.85.06.06.86.96.78.48.43.53.44.21.8

16.42.02.12.02.02.1

Feldspar/standard(× 100)

4.215.69.3

39.882.016.04.16.02.6

8.924.920.810.522.532.125.133.914.617.715.822.619.628.524.715.55.67.34.32.3

17.512.56.54.65.11.0

Barite/standard(× 100)

19.514.47.7

14.813.816.010.311.22.63.04.0

19.930.134.927.636.749.327.728.635.528.926.827.022.027.024.016.010.022.014.08.0

30.032.033.035.032.0

Opal-A(%)

8474878022608278799495

1113152515100

3013316

26134

22616960851500

1980

223