deep sea drilling project initial reports volume 75chn analyses of sediments and rocks sampled...

29. GEOCHEMISTRY OF ORGANIC CARBON IN SOUTH ATLANTIC SEDIMENTS FROMDEEP SEA DRILLING PROJECT LEG 751

Philip A. Meyers, Oceanography Program, Department of Atmospheric and Oceanic Science, The University ofMichigan, Ann Arbor, Michigan

Simon C. Brassell, Organic Geochemistry Unit, School of Chemistry, University of Bristol,Bristol, BS8 ITS, England

andAlain Y. Huc,2 Laboratoire de Géologique Appliquée, Université D'Orlėans, 45046 Orleans, France

ABSTRACT

CHN analyses of sediments and rocks sampled during DSDP Leg 75 in the South Atlantic have provided concentra-tions of organic carbon and atomic C/N ratios of organic matter from two sites. High values of organic carbon weremeasured in sediments deposited during Neogene and Cretaceous times at Site 530 in the Angola Basin; sediments de-posited at other times contain less than 0.5% organic carbon. Development of the Benguela Current and associatedupwelling-supported biological productivity is recorded in late Miocene to Holocene sediments which contain 1 to 7%organic carbon. These sediments include debris flows and turbidites composed of predominantly biogenic materials ori-ginally deposited on the Walvis Ridge and on the African continental margin. Organic-carbon-rich black shales contain-ing up to 17% organic carbon occur in late Albian to Coniacian turbidite sequences. These Cretaceous black shale layersare commonly several centimeters thick and are separated by bioturbated fine-grained organic-carbon-poor turbiditeswhich are usually much thicker. At Site 532 on the Walvis Ridge, biogenic sediments deposited between late Mioceneand Holocene times contain 1 to 9% organic carbon. Fluctuations in the intensity of high biological productivity associ-ated with the Benguela Current are preserved in alternating light and dark layers of sediments. C/N ratios of organicmatter in sediments from both sites are typical of marine sources.

INTRODUCTION

The composition of organic matter in marine sedi-ments is determined largely by the biological productiv-ity of overlying waters, the oxygen content of bottomwaters, and the extent of diagenesis in sediments. A fun-damental parameter of organic geochemical investiga-tions of sediments is the organic carbon content, whichis directly related to the amount of organic matter pres-ent. This quantity reflects the depositional environmentof the sediment because the degree of preservation oforganic matter is determined by interrelated physical,chemical, and biological factors. Availability of marine-and land-derived organic matter, oxicity/anoxicity ofthe depositional environment, and the sedimentationrate are major factors affecting the quantity of organiccarbon that is incorporated into sediments. These factorsdo not, however, completely determine the ultimate or-ganic carbon content of a sediment because diageneticmodification and degradation of organic matter takesplace after burial.

Although the factors governing the organic nitrogencontent of sediments are less well understood than thosecontrolling the amount of organic carbon present, gen-erally similar criteria apply. A useful relative measure ofthe nitrogen content of sediment organic matter is theC/N atomic ratio. Values between 14 and 30 are charac-

1 Hay, W. W., Sibuet, J.-C, et al., Init. Repts. DSDP, 75: Washington (U.S. Govt.Printing Office).

2 Present address: Department de Physico-Chimie, Institut Français du Pétrole, 92506Rueil-Malmaison, France.

teristic of terrigenous material, whereas those between 4and 8 typify marine organic matter (Goodell, 1972; Mul-ler, 1977). Changes during diagenesis significantly af-fect the precise value of the C/N ratio and thereforemay limit its utility (Muller, 1977; Waples and Sloan,1980).

During Deep Sea Drilling Project (DSDP), Leg 75,measurements of organic carbon content and of organicC/N ratios were done on sediment samples from two lo-cations in the southeastern Atlantic Ocean (Fig. 1). Site530 is in 4629 m water depth at the eastern margin of theAngola Basin, not far from the northern flank of theWalvis Ridge. Site 532 is on the Walvis Ridge at a waterdepth of 1331 m and close to Site 362 of Leg 40.

At Site 530, sediments were obtained from 115 msub-bottom to basement at 1103 m by rotary drilling inHole 53OA and from the water/sediment interface to181 m sub-bottom by hydraulic piston coring (HPC) inHole 53OB. Two HPC holes, 532 and 532B, providedsediments to a total sub-bottom depth of 291 m at Site532. Samples for organic analysis were taken routinelythroughout these sediment sequences. We report herethe results of organic carbon and organic C/N ratio de-terminations done onboard D/V Glomar Challenger andaugmented by later analyses done at the University ofMichigan.

ANALYSIS

Determination of Calcium Carbonate Content

The CaCO3 contents of sediment samples were determined on-board ship by the "karbonate bomb" technique (Muller and Gastner,1971). In this procedure, a dried sample is powdered, and a weighed

967

P. A. MEYERS, S. C. BRASSELL, A. Y. HUC

18° S

2 f

13° E

Figure 1. Locations of Site 530 (rotary drilling and hydraulic piston coring) and Site 532 (hydraulic pistoncoring). (Depth contours in m.)

aliquot is reacted with HCl in a closed pressure bomb. Any resultingCO2 pressure is proportional to the CaCO3 content of the sample. Ap-plication of a calibration factor to the manometer reading yields per-cent CaCO3. Percent error can be as low as 1% for sediments high inCaCO3, and in general an accuracy of ±2 to 5% can be obtained.

Shorebased CaCO3 determinations were done by measuring the to-tal carbon content of sediments before and after acid treatment withHCl. A Hewlett-Packard 185B CHN analyzer was used for the carbonmeasurements, and the percent CaCO3 was calculated from the differ-ence between initial and residual carbon contents.

Determination of Organic Carbon and Nitrogen Content

Shipboard organic carbon analyses were done using a Hewlett-Packard 185B CHN analyzer with He carrier gas at 60 psi (120ml/min.). Portions of dried and ground samples selected from eachcore for CaCO3 analysis were treated with dilute HCl to remove car-bonate, washed with deionized water, and dried at 110°C. A Cahnelectrobalance, mounted on a gimbal, was used to weigh 20 mg sam-ples of sediment for CHN analysis. The balance has an estimated ac-curacy of ±0.2 mg, depending upon sea conditions. Samples werecombusted at 1050°C with preconditioned oxidant (25 mg), and thevolumes of the evolved gases determined by gas chromatography asmeasures of the C, H, and N contents of sedimentary organic matter.Areas of gas peaks were determined with a Columbia Scientific In-dustries (CSI) mini-lab integrator and compared to those of standardsof known organic carbon content (Table 1). Concentrations of H andN are not known in most of these standards. For USGS SDO-1, Lev-enthal et al. (1978) report total N of 0.34% and organic N of 0.21%.These values were used to standardize instrument response so thatC/N atomic ratios could be reported. This approach differs from ear-lier shipboard procedures which used a synthetic CHN standard to de-termine nitrogen response factors. Values for hydrogen contents ob-tained by this CHN method are untrustworthy because of variableamounts of clay minerals and their hydrates and are not reported here.

Organic carbon analyses were repeated on shore for a number ofthe samples analyzed onboard D/V Glomar Challenger. In addition,many of the shipboard CaCO3 samples were analyzed for organic car-

Table 1. Standards used during Leg 75 for organic carbon determina-tions.

Standard

AWMAVB2725166-488-1663-467-58-3SDO-1

Total C(%)

0.450.572.682.978.90

10.40

Organic C(%)

0.270.452.482.504.31

10.06

Source

Phillips Petroleum CompanyPhillips Petroleum CompanyInstitut Français du PétroleDSDPDSDPU.S. Geological Survey

bon and nitrogen to provide new data. Sample preparation and instru-mentation were essentially the same as those used onboard ship.

Organic carbon determinations done on the same samples onboardD/V Glomar Challenger and at The University of Michigan agreewell. The mean difference between the shipboard and shorebased or-ganic carbon percentages is ±0.32 absolute percent. The overall rela-tive deviation from the mean of each shipboard-shorebased compari-son is ±8.87%, but this indicator of analytical precision improves to±4.37% for organic carbon concentrations above 1% dry sedimentweight. Problems with determination of organic nitrogen at The Uni-versity of Michigan appear as poor agreement in atomic C/N ratios.The greater consistency of C/N ratios calculated from shipboardanalyses suggests that these values are more reliable then the shore-based nitrogen analyses, hence discussion of C/N ratios will be basedupon the shipboard data.

LITHOLOGIC SETTINGS

Site 530—Angola Basin

A nearly continuous record of sedimentation in theAngola basin was obtained by drilling in Hole 53OA and

968

GEOCHEMISTRY OF ORGANIC CARBON

hydraulic piston coring in Hole 53OB. The sequences oflithologies encountered in Holes 53OA and 53OB areshown in Figure 2 and are fully described in the Site 530summary (this volume).

Unit 1 consists of Pleistocene sediments with varyingproportions of nannofossils, diatoms, and clay. Colorsof all sediments are shades of olive and olive gray;darker sediments are generally more diatom-rich andlighter sediments are generally more nannofossil-rich.Unit 1 is subdivided into two subunits on the basis ofrelative abundances of diatoms and nannofossils. Thedistinction between Subunits la and lb is the decrease inabundance of nannofossils to nil and the increase inrelative abundance of diatoms to more than 40% inmost of Subunit lb. Debris-flow deposits and turbiditesare abundant throughout Unit 1.

Unit 2, Pleistocene to late Miocene in age, consistsmainly of calcareous biogenic sediments interbeddedwith thick debris-flow deposits and thin mud turbidites.Colors of the sediments range from light greenish grayto olive to olive gray; the darker colors reflect an in-creasing clay content. The biogenic sediments are com-posed dominantly of nannofossils, with variable con-tents of foraminifers and clay and rare siliceous mate-rial.

Unit 3 consists of very soft, interbedded red andgreen middle Miocene to Oligocene muds, with rare,thin layers of dark greenish black turbidite silts andmuds, some scattered layers of volcanic ash, and rareforaminifer-nannofossil ooze. There is little composi-tional difference between green and red muds. Bothcontain a high proportion of clay-sized material, andthe green coloration appears often to be the result ofreduction of iron in the red mud (Sibuet, Hay et al., thisvolume).

Unit 4, Eocene to Maestrichtian in age, is made up ofmudstone, calcareous mudstone, and marlstone, com-monly with interbeds of nannofossil chalk and clasticlimestone. Green-colored components are dominant, butcolors grade into red. The colors vary with the propor-tions of carbonate present—white and bluish white lime-stone; yellowish gray chalk; greenish and olive graymudstone; dark greenish gray mudstone. The rock lay-ers in Unit 4 tend to occur as turbidites with a sharpbases and bioturbated tops.

The dominant lithologies of Unit 5 are Maestrichtianto Campanian green mudstone and marlstone, reflect-ing varying proportions of silt, clay, and carbonate. In-terbeds of clastic limestone are present in the upper partof the unit but become less common downward as car-bonate clastic debris is replaced by dark-colored si-liciclastics. Unit 5 is divided into three subunits on thebasis of abundance and composition of coarse elastics.In Subunit 5A, well-cemented clastic turbidites are com-monly interbedded with greenish-gray mudstone. Theconcentration of carbonate is somewhat lower in Sub-unit 5b than in Subunit 5a because of the introductionof sandstone beds and a decrease in number and thick-ness of clastic limestone beds downward within the sub-unit. In Subunit 5c, sand replaces clastic carbonate in

medium-bedded, well-defined turbidites of calcareoussandstone. Bioturbation is common throughout Unit 5.

The dominant lithology of Unit 6 is carbonate-ce-mented, greenish black volcanogenic sandstone depos-ited as graded turbidites. The dark green mudstone topsof these turbidites are commonly overlain by beds oflighter green, bioturbated, calcareous mudstone or marl-stone. This unit is Campanian in age.

Unit 7 is Campanian to Santonian in age and consistsof red claystone with interbeds of green, red, and purplesiltstone and claystone and green sandstone in num-erous repeated turbidite sequences. As sandstone be-comes less abundant, the thickness of individual tur-bidites decreases downward to the base of this unit,where most of the turbidites consist only of reddish pur-ple and red siltstone and claystone.

Unit 8 is composed of Coniacian to Albian red andgreen claystones like those at the base of Unit 7 with theaddition of thin layers of black shale. The claystonebeds occasionally contain thin green siltstone turbiditelayers and are usually bioturbated, although many ofthe red claystone beds appear to be massive. Pyrite iscommonly associated with both green claystone andblack shale as disseminated crystals and as large aggre-gates.

Unit 9 consists of medium gray, fine-grained Albianbasalt. The contact between the basalt and red mud-stone of Unit 8 occurs in the core catcher of Core 530A-105.

From Early Cretaceous (Albian) to Eocene time, thedominant sediments supplied to the southern AngolaBasin were fine-grained distal turbidities derived fromthe African continental margin. Beginning in the LateCretaceous (Coniacian), a small amount of coarser tur-bidites of varying composition were also supplied. Thesesediments contain a variable, mostly minor carbonatecomponent from both pelagic and continental marginsources, which indicates that the site was generally abovethe calcite compensation depth (CCD).

Mud turbidites deposited from the late Oligocenethrough the late Miocene indicate that turbidity currentswere still supplying fine-grained material from the Afri-can continental margin although the supply of coarse-clastic debris had stopped. The almost complete lack ofcarbonate suggests that during this time (30 to 10 m.y.ago) the site was below the CCD.

A marked increase in carbonate accumulation, seenas nannofossil marl and ooze, began in the late Mio-cene. This probably records the rapid deepening of theCCD resulting from increased productivity. Turbiditycurrents still supplied fine-grained elastics that formedpart of the clay-marl-ooze cycles, but most of the sedi-ment that accumulated was nannofossil debris. The firstindication of sediment supplied from Walvis Ridge isrecorded by the debris-flow deposits that began to ac-cumulate during the late Miocene. Increased diatomproductivity during the Pliocene resulted in the accumu-lation of diatom-rich, carbonate-poor sediments inter-bedded with ridge-derived debris-flow deposits. An in-crease in nannofossil abundance followed by an increase

969


Hole 530A

250-1

250

300-

350-

400

450-

500J

-T.'i~.'-T.\LT. — 1 5 m . y .

— 24 m.y.

37 m.y.40 m.y.

— 49 m.y.

750J

53.5 m.y.

70 m.y.

Figure 2. Lithologic units comprising the sediments and rocks encountered in Holes 53OA and 53OB in the Angola Basin. (Revisionsof stratigraphic ages are given in Steinmetz et al., this volume.)

in foraminifer abundance records deepening of the CCDduring the Quaternary. Pleistocene and Holocene sedi-ments rich in both diatoms and calcareous microfossilsare interbedded with debris-flow deposits and diatom-rich mud turbidites, both largely derived from WalvisRidge.

Site 532—Walvis Ridge

Site 532 is located on the eastern part of the WalvisRidge close to Site 362 in a trough with relatively thicksediment fill and near the Walvis Bay zone of upwellingand high productivity. The sediments are made up ofcalcareous and siliceous biogenic materials with variableamounts of terrigenous clay and are extensively biotur-bated. They accumulated very rapidly at rates of be-tween 25 and 60 m/m.y. The sequences at Holes 532 and532B are summarized in Figure 3 and are detailed in theSite 532 summary (this volume). Clearly defined fluctu-ations of light and dark sediment occur often over 1 to 3m intervals representing time spans of 30,000 to 50,000years. There is little evidence that the light-dark cycleswere caused by carbonate dissolution within the sedi-ment.

Only one lithologic unit was found in Holes 532 and532B; this consists of diatom and nannofossil ooze,marl, and clay. The unit is subdivided into three sub-units based on the relative proportions of biogenic com-ponents and clay. Site 532 sediments are Pleistocene tolate Miocene in age.

The dominant lithologies in Subunit la are nanno-foraminiferal and foram-nannofossil ooze and marl.Some of these have a significant diatom component.The colors are various hues of yellowish-brown andgreenish-olive. The darker layers are richer in organiccarbon, clay, and pyrite, but do not appear to be sys-tematically related to any particular biogenic compo-nent. All of the sediments are thoroughly bioturbated,and the gradational contacts between light and dark lay-ers are usually extensively burrowed.

Subunit lb is more siliceous than Subunit la. Thedominant lithologies are nannofossil diatom smarl andsari (see Site 530 summary). There are also minor sili-ceous ooze and nannofossil ooze and marl. The colorsare the same hues of yellowish-brown and greenish-oliveas found in Subunit la. Lighter and darker layers alter-nate. The dark layers tend to be more clay and organic-rich and to contain less carbonate than the lighter lay-ers. Sediments are highly bioturbated and burrowed.

Subunit lc comprises a thick monotonous sequenceof nannofossil marl. The colors are as for the overlyingsubunits, although in the bottom two-thirds the yellow-ish-brown colors disappear, and the dominant colors arepale and dark greenish-olive. In the bottom few cores,the colors are very light, with a slight bluish-gray tint.The dark-light interbedding is now more clearly a resultof a more clay and organic-rich (dark) and a more nan-nofossil-rich (light) composition. There is an overalltendency toward less frequent and less intense dark lay-ers with depth.

970


Hole 530B

750

1000J

— 78 m.y.

— 82 m.y.

1000-

1050-

1100-

86 m.y.

< 92 m.y.> 92 m.y.

— 1 0 0 m.y.

Major components

l~h^z*"! Forams and nannos \^= |Siliceous debris

| -*-!-*-1 Nannos [ΛVΛ ΛI Sandstone

j r ^ r ^ r j Clay IS3«^3 Debris -flow deposit

[ r r r n r j S i l t and clay (mud) j ' . '"! ' . ' . 1 . ' ! Clastic limestone ( =silicified)

| 1 Black shale ISvV>l Basalt

l~^^r-l Diatoms 1 ' ' ' '1 Chalk

Minor components

| ( v ) ^ | Volcanic breccia ^^o Volcanic ash

U A A| Chert | © | Pyrite

100-

150-

Figure 2. (Continued).

RESULTS


Through most of the sedimentary succession, organicmatter content was generally low, with the importantexceptions of mid-Cretaceous and Neogene deposits.The overall pattern of sediment total organic carbon(TOC) concentrations is shown in Figure 4. The differ-ent lithologic units are also indicated. TOC values of in-dividual samples are listed in Table 2, along with theirages, sub-bottom depths, and lithologic descriptions,their atomic C/N ratios, and their calcium carbonatecontents.

Black shales within the Albian to Santonian sequencesin the lower 200 m of Hole 53OA contain up to 16.5%TOC. These organic-carbon-rich layers were generallythin and were interbedded with thicker green and redclay stones generally containing less than 0.5% TOC.

Organic-carbon-rich sediments in the upper 250 m atSite 530 have a TOC range of 1 to 7%, which is smallerthan in the Cretaceous sequences. These sediments arelate Miocene to Holocene in age and consist of biogenicdebris flows and turbidites apparently derived from

shallower-water deposits on the Walvis Ridge, where sim-ilar organic-rich sediments of the same age were recov-ered at Sites 362 (Foresman, 1978) and 532.


The content of organic matter of these sediments ishigh, ranging up to 9.75% dry sediment weight (Table3). Organic carbon contents are consistently higher thanthe average of 0.2% of most pelagic sediments (Degensand Mopper, 1976), which is surprising in view of theextensive bioturbation evident in cores from these holes.The increase in TOC from about 2% in late Miocenesediments to values between 3 and 6% in Pliocene andPleistocene oozes parallels that reported for Site 362 byErdman and Schorno (1978) and also that found at Site530 (Table 2 and Fig. 4).

DISCUSSION


Contents of organic carbon in sediments from the up-per 300 m and rocks from the bottom 200 m at Site 530are much higher than typical marine deposits. Waples

971


Hole 532

100-

150-

200

250

Lithology

_L J_

1a

1b

Hole 532B

250

Figure 3. Lithologic subunits comprising the biogenic sediments found in Holes 532 and 532B on the Wal-vis Ridge. (Revisions of stratigraphic ages are given in Steinmetz et al., this volume.)

972


100

300

500

700

900

1100

•

•;.V

••

-

i •••

i i i i i i i i i i i

-

-

-

-

••

i i i i i i i i i i i -

1a

1b

2

3

4

5a

5b

5c

6

7

8

6 8 10 12 14Total organic carbon (%)

16 Lithologicunit

Figure 4. Total organic carbon contents expressed as percent of drysediment weight from Site 530 in the Angola Basin. (Lithologicunits are shown in Fig. 2 and described briefly in the text and fullyin Site 530 summary, this volume.)

and Sloan (1980) present data from DSDP Leg 58 show-ing that, under uniform conditions of organic matterproduction and sedimentation, postdepositional degra-dation will decrease organic carbon concentrations toca. 0.1% in 2 to 5 m.y. This occurs regardless of burialdepth, although higher sedimentation rates appear to re-tard degradation.

The existence of the organic-rich zones in Holes 53OAand 53OB indicates significant changes in those factorsimportant to organic matter accumulation in sediments.Table 4 summarizes average organic carbon concentra-tions and C/N ratios of the samples listed in Table 2 andgroups these data according to Site 530 lithologic units.The phytoplankton paleoproductivity of each unit isestimated from sedimentation rates and organic carboncontents using the expression derived by Muller andSuess (1979):

Paleoproductivity, R =- Φ)

(O.OO3O)S° 30

where C = weight percent organic carbon, Ps = sedi-ment density (2.6 g/cm3 assumed here), <j> = sedimentporosity (0.9 assumed here), and S = linear sedimenta-tion rate.

Unit 8 consists of Late Cretaceous (Albian to Conia-cian) black shales and red and green claystones. The av-erage sedimentation rate of this unit is 9 m/106y., whichis five to ten times greater than the average rate for clays

in deep ocean basins (Heezen and Hollister, 1971, p.118) and reflects downslope input of material from thecontinental margin. Red and green claystones are low inorganic carbon, averaging 0.42%, whereas the blackshales are rich in organic carbon. The estimated primaryproduction rate which formed the organic matter con-tained within the red and green layers is 38 g C/mVy.According to Menzel (1974), this value is midway be-tween the mean productivities of oligotrophic open-ocean subtropical areas and open-ocean edges of equa-torial convergences. However, Site 530 has always beenclose to the African continental margin and was be-tween 30° to 35°S during the Late Cretaceous (First-brook et al., 1979). Furthermore, the method developedby Muller and Suess (1979) to estimate paleoproduc-tivity is based upon measurements from young sedi-ments and does not provide for the diagenetic losses oforganic matter documented by Waples and Sloan (1980).For these reasons, the value of 38 g C/m2/y. for the redand green claystones is probably low, since it is cal-culated from some unknown fraction of the organic mat-ter deposited originally.

The estimated paleoproductivity leading to the or-ganic-carbon-rich black layers is 480 g C/mVy. (Table4). This is quite high and is greater than the present-dayrates in up welling areas off Mauritania (250 g C7m2/y.)and off Peru (300 g C/m2/y.), which are among thosecited by Muller and Suess (1979) to derive their relation-ship between primary productivity, surface sediment or-ganic content, and sedimentation rates. The high organ-ic content in the black shales may have resulted from ex-ceptional preservation of organic matter, and so thisproductivity estimate may be high.

Sediment accumulation rates have a profound effectupon organic matter preservation. Muller and Suess(1979) determined that only 0.01% of the primary or-ganic matter production avoids destruction in sedimentsaccumulating at 2 to 6 mm/103y. The amount increasesto 0.1 to 2% at accumulation rates of 2 to 13 cm/103y.and jumps to 11 to 18% at 66 to 140 cm/103y. Althoughthe mean sedimentation rate in Unit 8 is 9 m/lO<>y. (9mm/103y.), this unit consists of a mixture of pelagic andturbiditic sediments, so organic-carbon-rich layers mayrepresent times of rapid sedimentation as a result of tur-bidite deposition in addition to periods of high produc-tivity. Alternatively, the black shales may consist of or-ganic-carbon-rich sediments originally deposited upslopeand transported into the Angola Basin by turbidity flowand slumping.

An additional factor which would lead to increasedpreservation of organic carbon is anoxic near-bottomwaters in the Angola Basin during the Late Cretaceous.Tissot et al. (1979) and Arthur and Natland (1979) pro-pose that, because the North and the South Atlanticwere not interconnected until the Turonian (87-91 m.y.ago) and because of the shallow Walvis Ridge-RioGrande Rise sill depth, deep-water circulation was slug-gish in the Angola Basin, resulting in widespread anoxicconditions. Such conditions could have been similar tothose in the modern-day Black Sea, or they could havetaken the form of an expanded and intensified midwater

973


Table 2. Description and organic content of sediment samples from DSDP Site 530 in the Angola Basin.Shore-based determinations are distinguished by parentheses from those done aboard ship.

Sample(interval in cm)

53OB-1-1, 46-47530B-1-2, 52-53530B-2-1, 70-7153OB-2-2, 55-5853OB-2-3, 70-7153OB-3-1, 85-8653OB-3-2, 85-8653OB^*-1, 75-8053OB-4-1, 85-8653OB-1-3, 110-111530B-6-1, 105-10653OB-7-2, 50-51530B-7-3, 20-21530B-8-2, 71-72530B-9-1, 66-67530B-9-2, 110-12053OB-9-3, 14-1553OB-1O-1, 87-8853OB-1O-1, 117-12453OB-1O-3, 74-7553OB-11-1, 70-7153OB-11-2, 61-6253OB-11-3, 30-3153OB-12-2, 78-8053OB-12-3, 29-3153OB-14-3, 27-2953OB-18-1, 100-10153OB-2O-2, 4-553OB-21-2, 9-1053OB-23-1, 103-10453OB-25-1, 95-96530B-26-2, 126-128530B-27-2, 46-49530-2-2, 52-5453OA-1-1, 92-9453OB-33-2, 118-120530B-43-2, 112-114530B-44-2, 145-148530B-44.CC (27-30)530A-5-5, 27-29530A-6-2, 128-13053OA-7-1, 117-120530A-7-2, 5-8530A-7-2, 131-13353OA-7-3, 30-32530A-7-6, 54-5653OA-8-5, 12-14530A-9-1, 102-10453OA-1O-1, 27-2953OA-11-5, 95-9753OA-12-5, 52-5453OA-13-2, 67-69530A-14-1, 91-93530A-14-3, 91-93530A-15-4, 45-4753OA-18-3, 42-4453OA-19A 30-32530A-21-4, 24-26530A-22-6, 81-83530A-24-3, 75-7753OA-25-3, 87-89530A-26-3, 48-50530A-27-7, 35-37530A-28-1, 90-92530A-30-4, 124-12653OA-31-2, 76-78530A-33-2, 5-7530A-34-2, 49-51530A-34-2, 90-9253OA-35-1, 7-9530A-37-3, 67-69530A-40-1, 42-43530A-41-1, 100-101530A-42.CC530A-44-2, 44-45530A-47-1, 103-105530A-48-2, 19-20530A-49-1, 49-5053OA-5O-2, 12-1453OA-5O-2, 55-57530A-50-4, 21-2253OA-51-5, 119-121530A-52-1, 60-6153OA-53-2, 70-7153OA-55-3, 26-2753OA-57-2, 84-8553OA-58-1, 89-90530A-59-2, 24-2553OA-6O-2, 112-11453OA-61-1, 87-8853OA-63-3, 62-64

Geologicage

PleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePlioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneMiddle MioceneMiddle MioceneMiddle MioceneMiddle MioceneMiddle MioceneEarly MioceneEarly MioceneEarly MioceneEarly MioceneEarly MioceneEarly MioceneOligoceneOligoceneOligoceneOligoceneLate EoceneEarly EoceneEarly EoceneLate PaleoceneLate PaleoceneLate PaleoceneLate PaleoceneEarly PaleoceneEarly PaleoceneMaestrichtianMaestrichtianMaestrichtianMaestrichtianMaestrichtianMaestrichtianMaestrichtianMaestrichtianMaestrichtianCampanianCampanianCampanian

Sub-bottomdepth

(m)

0.52.03.14.56.17.79.2

12.012.115.321.125.026.630.032.934.835.337.537.840.341.743.144.347.748.757.572.882.186.193.4

100.8105.6109.2117.2125.9129.7162.6164.5167.4169.3175.3183.2183.6184.8185.3190.0197.5202.0210.8227.0236.0241.0249.5252.5263.0290.0301.0320.0333.0347.0357.0366.0381.5382.5406.2412.0430.5440.5441.0448.0470.5496.0506.0524.0535.5563.0573.0581.5592.0592.6595.0607.0610.0621.0641.0659.5667.5678.0688.1696.0717.5

Lithologicdescription

Diatom nannofossil oozeDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil oozeDiatom nannofossil oozeDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil oozeDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil marlDiatom nannofossil oozeDiatom nannofossil marlDiatom nannofossil oozeDiatom nannofossil marlOlive diatom nannofossil marlOlive diatom nannofossil marlDark olive diatom clayOlive diatom clayDark olive diatom oozeDark olive diatom oozeOlive diatom oozeOlive diatom oozeLight brown diatom nannofossil marlClayey diatom oozeDark olive clayey diatom oozeClayey nannofossil diatom oozeClayey nannofossil diatom oozeDark olive diatom oozeDark olive diatom oozeDark green nannofossil diatom oozeGreen diatom clayOlive diatom nannofossil oozeDebris flow matrixDark olive silt-clayDark olive silt-clayLight olive silt nannofossil clayOlive nannofossil silty clayNannofossil clayey diatom oozeLight green foram nannofossil oozeGreen clayOlive nannofossil clayOlive nannofossil clayOlive nannofossil clayOlive silty clayOlive nannofossil marlLight green nannofossil oozeOlive nannofossil clayOlive silty clayOlive nannofossil oozeGreen foram nannofossil marlLight green foram nannofossil oozeGreen mudGreen mudDark green clayGreen clayOlive black clayGreen clayGreen mudGreen mudBrown mudBrown mudGreen mudGreen mudLight olive mudBlack mudGreen black mudGreen mudGreen mudstoneDark green mudstoneBrown mudstoneBlack mudstoneBlack mudstoneWhite clastic limestoneGreenish black mudstoneGreenish black mudstoneOlive mudstoneOlive mudstoneLight olive marlstoneDark green mudstoneGreen mudstoneOlive mudstoneDark green marlstoneDark green mudstoneGreen mudstoneDark green mudstoneDark green marlstoneGreen mudstoneGreen mudstone

CaCO3

(wt.%)

623631(4)552434(6)14322320311139

(15)2421

(45)6

13747

1153

< l< l12

< l< l< l

35

47431359

155

(50)1

(15)(14)166

222895

343446

1< l< l< l< l< l< l< l< l< l< l< l< l< l< l< l< l

9< l

21

115

12134457

81

1229943

266

11

TOC(wt.%)

1.332.413.78

(5.64)1.99

1.64

2.773.103.270.793.313.212.51

(1.79)3.853.43

(1.51)3.823.974.543.694.534.811.673.40 (3.54)4.48 (4.95)2.106.21 (6.57)2.86 (3.35)2.623.392.242.081.621.801.511.301.951.98

(0.42)0.84

(2.18)(0.98)2.631.761.022.290.921.101.230.300.360.460.270.260.190.490.070.210.250.230.220.530.260.120.790.220.300.250.430.360.270.500.280.280.250.190.070.090.350.300.320.140.420.160.180.240.240.11

AtomicC/N

15.210.411.7

(14.3)17.5

12.0(15.6)13.113.813.713.714.414.413.3(7.8)13.413.6(8.3)13.913.913.813.813.913.612.913.9 (4.4)13.9 (6.0)11.814.0 (5.8)12.4 (3.8)12.113.712.324.113.412.711.49.8

10.913.4(9.0)11.1(8.9)(5.6)13.29.5

11.813.49.6

10.312.88.28.05.84.44.34.27.02.16.14.84.34.5

10.45.53.1

11.34.86.47.7

10.212.48.17.77.8

10.17.77.45.37.76.0

14.49.17.6

15.010.813.215.15.48.2

974

Table 2. (Continued).



Geologicage

Sub-bottomdepth

(m)Lithologicdescription

CaCO3

(wt.%)TOC

(wt.%)Atomic

C/N

530A-64-1, 53-54530A-68-2, 95-9653OA-71-2, 50-5253OA-75-4, 22-2353OA-76-1, 70-7153OA-77-3, 134-135530A-84-2, 117-11853OA-85-2, 6-7530A-86-4, 145-14753OA-86-5, 31-3253OA-86-5, 33-34530A-86-5, 36-37530A-87-1, 37-3853OA-87-1, 83-8453OA-87-3, 83-85530A-87-4, 105-10653OA-87^», 118-119530A-88-1, 65-6653OA-88-3, 33-3453OA-88-3, 90-91530A-89-1, 34-3553OA-9O-3, 86-8753OA-9O-3, 99-100530A-91-4, 45-4653OA-93-1, 40-4153OA-93-2, 35-3653OA-93-3, 45-4653OA-93-3, 83-84530A-94-1, 42-43530A-94-2, 11-12530A-95-4, 101-10253OA-95-5, 0-2153OA-95-5, 38-50530A-96-2, 118-119530A-96-3, 97-98530A-96A 29-3053OA-%-4, 40-41530A-96-4, 61-62530A-96-6, 88-89530A-97-1, 27-29530A-97-1, 87-91530A-97-1, 91-95530A-97-1, 99-105530A-97-1, 105-110530A-97-3, 59-6053OA-97-3, 83-84530A-97-4, 56-57530A-97-4, 87-88530A-97.CC —530A-98-2, 60-61530A-98-2, 69-7053OA-98.3, 92-9353OA-98-3, 110-111530A-99-1, 107-108530A-99-2, 67-6953OA-99-3, 118-120530A-99-5, 70-7153OA-99-5, 86-8753OA-1OO-1, 85-8653OA-1OO-1, 99-100530A-100-2, 120-12153OA-1OO-3, 142-14353OA-10O-4, 114-11553OA-1OO-5, 38-3953OA-1O1-1, 16-1753OA-1O1-2, 8-9530A-101-2, 17-18530A-101-2, 21-2253OA-1O1-4, 36-37530A-101-4, 55-56530A-101-6, 86-8753OA-1O1-7, 49-5053OA-1O2-1, 149-15053OA-1O2-3, 120-12153OA-1O2-3, 130-13153OA-1O2-3, 145-146530A-103-4, 85-8653OA-1O3-6, 22-23530A-104-1, 124-12553OA-1O4-2, 141-14253OA-1O4-3, 0-153OA-1O4-4, 91-92530A-104-4, 123-12453OA-1O4-5, 61-6253OA-1O5-1, 23-2453OA-1O5-2, 139-14053OA-1O5-3, 18-2053OA-1O5-4, 9-10530A-105-4, 35-3653OA-1O5.CC 3-4

CampanianCampanianCampanianCampanianCampanianCampanianSantonianSantonianSantonianSantonianSantonianSantonianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianConiacianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianCenomanianAlbianAlbianAlbianAlbianAlbianAlbianAlbianAlbianAlbianAlbianAlbianAlbian

724.0764.0792.0829.5838.0851.5915.5923.5937.0937.5937.5937.6940.5941.0944.0945.6945.7949.7952.3952.9958.3970.9971.0981.0990.4991.8993.5993.8999.4

1000.61013.51014.11014.41019.71021.01021.81021.91022.11025.41026.31026.91026.91027.01027.11029.61029.81031.11031.41035.01037.11037.21038.91039.11045.11046.21048.21050.71050.91053.91054.01055.71057.41058.61059.41062.21063.61063.71063.71066.91067.11070.41071.51072.51075.21075.31075.51083.41085.71086.21087.91088.01090.41090.71091.61094.21096.91097.21098.61098.91103.0

Light olive marlstoneDark olive mudstoneGreenish gray mudstoneGreen claystoneBlue claystonePurple claystoneGreen dolomiteDark red claystoneGreen claystoneBlack claystoneBlack claystoneGreen claystoneBlack shaleBlack claystoneDark red claystoneBlack shaleGreen claystoneLight brown limestoneBlack shaleBlack shaleBlack shaleBlack shaleGray marlstoneGreen claystoneGreen claystoneGreen shaleRed claystoneGreen claystoneBlack shaleDark green shaleGreen claystoneGreen claystoneBlack shaleDark red claystoneLight brown marlstoneBlack shaleGreen shaleBlack shaleBlack shaleLight green limestoneGreen claystoneBlack shaleBlack shaleGreen claystoneBlack shaleGreen claystoneBlack shaleGreen claystoneBlack shaleDark green claystoneBlack shaleBlack shaleDark green claystoneGreen shaleLight green limestoneLight green marlstoneBlack shaleGreen shaleDark green shaleBlack shaleLight green marlstoneLight green marlstoneDark green marlstoneDark red claystoneGreen claystoneBlack shaleLight green marlstoneBlack shaleDark green claystoneLight green marlstoneLight green marlstoneLight green claystoneDark green claystoneBlack shaleDark green claystoneLight green marlstoneOlive black mudstoneGreen claystoneLight green marlstoneDark green claystoneBlack claystoneGreen claystoneDark green claystoneBlack claystoneDark green claystoneBlack shaleLight green limestoneBlack shaleDark green claystoneRed claystone

24< l1911

2341

84

< l< l< l< l< l< l< l< l78

< l< l153

11< l< l< l< l

4< l< l< l< l< l3410

< l9

< l< l82

< l< l< l< l< l< l< l< l< l< l< l

2< l< l7615

< l< l< l< l143529

< l< l< l26

< l2140165

< l< l1134

< l< l553

< l< l< l

3< l< l646

< l< l

0.220.260.150.370.150.240.190.210.281.282.020.255.371.310.256.220.160.119.702.849.60

16.500.621.190.950.180.110.83

12.27 (12.66)0.350.22

(0.20)(12.95)

0.11(0.76)1.790.39 (0.41)5.82 (5.70)2.10

(0.15)(0.58)(4.89)

(10.01)(0.80)7.29 (7.33)

(1.20)8.040.177.660.281.448.57 (7.71)0.470.230.08

(1.04)1.730.380.281.92

(0.41)(0.45)

(0.38)(0.70)0.930.485.081.310.08

(0.38)(0.30)1.161.730.45

(0.49)7.700.16(0.33)

(0.71)0.415.210.470.180.570.235.28

(0.44)3.600.16(0.36)0.15

9.115.215.521.215.317.313.79.0

14.620.621.315.924.020.2

9.423.2

7.313.424.724.928.936.518.615.914.110.17.0

32.534.5 (27.8)18.66.0

(4.5)(36.0)10.8(6.5)25.928.4 (27.0)26.4 (10.5)27.9

(23.8)(6.8)

(38.1)(40.3)(5.7)32.1 (32.3)(6.5)31.6

8.730.910.724.130.2 (25.6)18.013.010.6

(17.0)23.310.211.323.1(6.9)(8.2)

(0.9)(1.6)14.217.228.537.110.4(0.7)(0.8)18.522.820.4(9.6)30.210.5 (2.8)(7.4)11.729.017.111.323.112.428.2(8.1)30.09.4(3.1)8.3

975


Table 3. Descriptions and organic contents of sediment samples from DSDP Site 532 on the Walvis Ridge.Shore-based determinations are distinguished by parentheses from those done aboard ship.


532-1-2, 7-9532-2-2, 80-90532-2-3, 6-8532-2-3, 60-62532-3-2, 29-31532-3-3, 106-108532-4-2, 17-19532-4.CC532-5-1, 96-98532-5-2, 100-110532-5-3, 96-98532-6-2, 55-56532-6-2, 144-145532-7-1, 75-76532-8-2, 70-71532-8-2, 100-101532-8-2, 145-146532-8-3, 20-30532-9-1, 16-18532-9-2, 108-110532-9-3, 123-124532-10-2, 64-66532-10-2, 105-107532-10-3, 44-45532-10,CC(9-ll)532-11-2, 69-70532-11-3, 10-20532-11-3, 53-54532-11-3, 149-150532-12-1, 79-80532-12-2, 79-80532-13-1, 69-71532-13-2, 53-56532-13-3, 89-92532-13.CC (13-15)532-14-2, 38-39532-14-2, 55-65532-14-3, 38-39532-15-2, 34-35532-15-3, 34-35532-16-1, 118-120532-16-2, 122-124532-16-3, 40-42532-17-1, 81-83532-17-2, 81-83532-17-3, 91-93532-18-1, 91-93532-18-2, 91-93532-19-2, 82-84532-19-3, 20-30532-19-3, 81-83532-20-1, 70-72532-20-3, 71-73532-21-2, 29-30532-21-3, 88-90532-22-1, 136-139532-22-2, 136-139532-22-3, 130-133532-23-1, 59-61532-23-3, 34-36532-24-1, 109-112532-24-2, 127-130532-24-3, 93-96532-25-1, 51-52532-25-2, 51-52532-25-2, 80-90532-26-1, 49-50532-26-2, 5-6532-27-1, 86-88532-27-2, 66-68532-27-2, 86-88532-28-2, 18-20532-29-2, 10-13532-29-3, 10-13532-31-1, 144-145532-31-2, 64-65532-31-2, 65-75532-31-3, 18-19532-32-1, 11-13532-32-2, 46-49532-32-2, 147-149532-33-2, 61-62532-33-3, 41-43532-34-1, 121-122532-34-2, 49-51532-34-2, 71-72532-35-2, 94-96532-35-3, 70-72532-36-1, 71-72532-37-2,45-55532-38-1, 65-68

Geologicage

PleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePleistocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocene

Sub-bottomdepth(m)

1.66.37.17.6

10.211.414.517.218.219.721.223.724.526.832.632.933.433.635.037.439.041.341.842.643.645.846.747.148.048.850.353.154.456.356.858.758.960.263.064.566.868.369.070.872.373.975.376.881.182.082.683.986.989.491.593.494.996.397.099.7

101.9103.6104.7105.7107.2107.5110.1111.2114.9116.2116.4119.1122.4123.9128.8129.5129.6130.6131.9133.8134.8137.3138.6140.4141.2141.4145.0146.3147.3152.6154.5

Lithologicdescription

CaCO3

(wt.Vo)TOC

(wt.%)Atomic

C/N

Light olive nannofossil foram oozeOlive nannofossil foram marlDark olive nannofossil foram marlLight olive nannofossil foram oozeLight olive nannofossil foram oozeOlive nannofossil foram oozeLight olive nannofossil foram oozeOlive nannofossil foram oozeOlive nannofossil foram oozeDark olive smarlLight olive diatom foram oozeDark olive foram nannofossil marlLight olive foram nannofossil oozelight olive diatom foram marlLight olive diatom foram marllight olive diatom foram marlOlive foram nannofossil marlDark olive foram nannofossil marlDark olive foram nannofossil oozeLight olive foram nannofossil marlLight olive foram nannofossil oozeLight olive nannofossil oozelight olive nannofossil marlOlive foram nannofossil marlDark olive nannofossil diatom oozeLight olive foram nannofossil oozeDark olive diatom nannofossil marllight olive diatom foram oozeDark olive foram nannofossil oozelight olive diatom foram oozeDark olive diatom nannofossil marlDark olive diatom nannofossil marlDark olive diatom nannofossil marllight olive diatom nannofossil marlLight olive diatom nannofossil marlDark olive diatom nannofossil marlDark olive diatom nannofossil marlLight olive diatom nannofossil marlLight olive diatom nannofossil marllight olive diatom nannofossil marlLight olive nannofossil diatom oozeDark olive nannofossil diatom oozeMedium olive diatom nannofossil marllight green-gray diatom nannofossil oozeDark olive diatom nannofossil oozeLight olive nannofossil diatom marlDark olive nannofossil diatom marlLight olive nannofossil diatom marlOlive diatom nannofossil marlDark olive diatom nannofossil marlLight olive diatom nannofossil marlDark olive nannofossil clay oozeLight olive nannofossil diatom oozeDark olive smarlLight olive smarlLight olive smarlDark olive smarlLight olive smarlLight olive dolomitic smarlLight olive dolomitic smarlLight olive nannofossil marlLight olive nannofossil marlDark olive diatom nannofossil oozeDark olive nannofossil clayLight olive nannofossil clayDark olive nannofossil clayLight olive diatom nannofossil oozeLight olive diatom nannofossil oozeOlive diatom nannofossil marlDark olive diatom nannofossil marlLight olive foram nannofossil marlOlive diatom nannofossil marlLight olive diatom nannofossil marlDark olive diatom nannofossil marlDark olive clayDark olive clayDark olive clayLight olive nannofossil marlDark olive silty clayLight olive diatom nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlLight olive siliceous nannofossil marlDark olive siliceous nannofossil marlLight olive siliceous nannofossil marlLight olive siliceous nannofossil oozeDark olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marl

68(38)38627358684041(4)70346240473941

(12)6242585850502353

(11)415542332527414315(9)442742481925433232212039

(11)2831318

4840413245585550231131

(16)40453213342745252112

(36)462026623959533325554353

(39)57

3.66(3.74)(2.70)(1.42)(0.99)3.28

(1.83)4.80 (4.88)

(5.64)(9.75)1.98

(6.06)(2.26) (2.78)(2.53)1.702.933.64

(5.41)2.013.571.161.26

(2.20)(3.11)4.30

(1.80)(6.51)5.521.88

(2.95)(5.04)3.482.74

(2.65)(1.52)5.91

(6.18)2.68

(3.45)(2.01)(2.46)(2.65)(2.97)(3.15)3.20

(3.06)(4.12)4.30

(4.02)(5.02)(3.37)(3.15)(4.91)6.35 (5.90)

(1.36)(2.56)4.12(4.18)

(2.76)

(4.05)(2.31)2.653.406.043.03

(6.41)2.47

(1.56)3.874.48

(1.99)(2.26)(2.51)4.44

(3.86)5.87

(3.71)(2.26)5.86

(1.80)

(2.98)(0.80)(0.91)(2.13)5.47 (5.62)

(2-17)3.27

(2.47)(2.31)(0.94)

12.1(14.3)

———

14.7—

14.8 (5.3)(17.0)(26.3)15.2(7.4)

(14.8)(20.4)13.214.715.0

(15.9)13.514.912.012.4(4.8)

(12.0)14.9

—(20.0)15.913.3

(11.9)(13.9)14.813.5(4.7)

—15.5

(15.2)14.8

——

(12.7)(12.5)(14.9)(11.4)14.6

—(19.2)15.3

(13.7)(15.2)(12.4)(15.6)(13.2)15.5 (8.6)

(21.7)(12.4)21.4(21.3)(5.6)

(13.2)(8.6)17.115.016.413.9

(15.9)15.4

—16.214.8

(12.4)(13.2)(11.8)15.2(8.4)16.5

(16.1)—

16.5—

——

(11.4)—

16.1 (9.8)(9.9)14.9

(13.2)(14.5)

—

976


Table 3. (Continued).


Geologicage

Sub-bottomdepth

(m)Lithologicdescription

532-38-2, 50-53532-39-2, 60-62532-39-3, 60-62532-40-1, 75-76532-41-2, 80-82532-41-3, 4-5532-42-2, 71-72532-42-2, 79-80532-42-2, 140-141532-43-1, 71-72532-43-1, 117-118532-43-1, 130-140532-44-3, 36-37532-44-3, 110-111532-45-1, 116-119532-45-2, 42-45532-46-2, 100-101532-46-3, 96-99532-47-3, 110-112532-48-1, 64-67532-48-2, 142-145532-49-1, 70-71532-49-2, 86-92532-49.CC (3-4)532-50-1, 82-83532-51-1, 144-150532-51-2, 75-78532-52-1, 64-70532-52-2, 141-147532-54-1, 81-87532-56-1, 100-104532-56-2, 34-39532-57-1, 109-110532-58-2, 67-68532B-58-2, 80-90532B-58-3, 0-6532B-59-1, 80-86532B-59-2, 80-90532B-59-2, 106-112532-60-2, 42-48532B-61-3, 5-11532B-61.CC (20-21)532B-62-2, 124-130532B-63.CC (4-5)532B-64-1, 80-81532B-65-1, 51-54532B-65-2, 80-90532B-65-2, 109-111532B-66.CC (7-13)532B-67-2, 54-55532B-67-3, 54-55532B-68-1, 54-55532B-68-2, 54-55532B-69-2, 19-20532B-69-2, 89-90532B-70-2, 70-71532B-71-2, 76-82532B-72-1, 34-36532B-72-2, 34-36532B-73-2, 14-20532B-74.CC —

PliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePliocenePlioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate MioceneLate Miocene

155.8158.9159.4161.6167.5168.2171.8171.9172.5174.7175.2175.3180.8182.5184.0184.7189.3190.8195.3196.3198.5200.3202.0203.6204.8209.1209.9212.3214.5220.8229.0229.9232.5237.0237.2238.8240.6242.1242.3244.8250.3250.8254.0257.7258.5260.2262.0262.3267.1269.1270.6272.0273.5277.2277.9281.5284.6285.6287.1290.0291.3

Dark olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil clayDark olive nannofossil clayLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlDark olive nannofossil marlDark olive nannofossil clayLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil clayLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marlDark olive nannofossil marlDark olive nannofossil clayDark olive nannofossil clayLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil marllight olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlDark olive nannofossil clayLight olive nannofossil oozeDark olive nannofossil marlDark olive nannofossil marlLight olive nannofossil marlDark olive nannofossil clayLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marllight olive nannofossil marllight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marllight olive nannofossil marllight olive nannofossil marlLight olive nannofossil marlLight olive nannofossil marl

CaCθ3(wt.%)

TOC(wt.%)

AtomicC/N

2945603745275854345038

(24)30535568445541623455553746616344724765474932

(44)5145

(35)3748465064296044

(51)5938496947685761737478726371

3.12(1.31)(3.56)2.99

(2.37)4.11

(1.91)1.542.90

(1.30) (1.03)(3.22)(3.92)(4.24)1.69

(2.20)(0.55)2.44 (2.04)

(1.75)(2.59)(0.96) (0.90)(3.75)(1.65)(0.45)2.022.242.021.032.862.243.950.681.992.203.11

(2.06)2.041.02

(1.69)2.661.231.661.43 (1.43)0.572.17

(2.92)1.84

(1.44)(0.21)3.272.15

(2.61)(0.68)(0.38)2.11

(2.85)(0.14)(0.50)(0.98)(0.10)1.51 (2.11)

(0.50)

15.5—

(14.1)15.4(9.6)16.C(6.0)14.214.4

(18.5) (11.2)(12.8)(13.7)(12.7)13.8

(13.0)—

14.7 (14.7)(16.1)

—(13.3)(15.4)(43.5)

(9.3)13.914.824.714.026.217.530.114.214.715.015.0

(16.1)15.013.0(8.9)17.613.918.913.6 (13.6)10.813.9

—14.9

(12.2)(10.1)14.514.3

——

(17.9)20.1

—(10.3)(52.6)(22.7)

—15.6 (5.9)

(47.6)

oxygen minimum zone. These situations would result inenhanced preservation of organic matter, both duringsinking through the water column and after incorpora-tion into surface sediments. However, Förster (1978)concludes from fossil ammonite distributions that theinterconnection between the North and the South Atlan-tic oceans became established in the late Albian (ca. 102m.y. ago), thus providing a northern source of oxygen-containing water to the Angola Basin and lessening thelikelihood of strongly developed anoxic conditions dur-ing the Late Cretaceous.

Two features present in Unit 8 argue against the ex-istence of a Black Sea type of strongly anoxic condition.First, burrowing by benthic animals is plainly present inmost parts of the unit (Hay et al., 1982; Site 530 sum-mary, this volume). Second, black shales are interbed-ded among green and red claystones (Table 2, Fig. 5).

The red layers make up about 44% of the unit and evi-dently were deposited under oxygenated bottom waters.These two observations preclude the existence of per-manently anoxic bottom waters in the Late CretaceousAngola Basin, but do not rule out short periods of bot-tom water anoxia or the presence of a midwater oxygen-depleted layer.

Layers of green claystones make up about 47% ofUnit 8 and are the type of organic-carbon-rich sedimentmost commonly interbedded with black shale layers.The contrast in the organic carbon contents of these dif-ferent lithologies is striking (Tables 2 and 4, Fig. 5).There are two possible interpretations for the green col-oration: either it is the result of diagenetic reduction ofiron in red muds deposited next to layers rich in organicmatter, or it is from iron reduction during deposition ofsediments in poorly oxygenated bottom waters. These

977


Table 4. Summary of organic matter contents and paleoproductivities of Site 530 sediments and rocks.

LithologicUnita

la

lb2

34

5a

5b

5c

67

8

Depth(m)

0-58

58-110110-277

277-467467-600

600-647

647-704

704-790

790-831831-940

940-1103

Aue(m.y. ago)

<1.7

< 1.71.7-10

10-3737-66

66-69

69-70.5

70.5-77.5

77.5-80.580.5-84

84-102.5

Description

Diatom nannofossil marl and ooze anddebris-flow deposits

Diatom ooze and debris-flow depositsNannofossil clay, marl, and ooze and

debris-flow depositsRed and green mudMulticolored mudstone, marlstone,

chalk, and clastic limestoneDark green mudstone, marlstone, and

clastic limestoneDark green mudstone, marlstone,

clastic limestone, and siliciclasticsandstone

Dark green mudstone, marlstone, andcalcareous siliciclastic sandstone

Glauconitic sandstoneVariegated red and green claystone,

siltstone, and sandstoneRed and green claystone and marlstone

with interbedded black shale

Sedimen-tationrate

(m/m.y.)

65

6520

95

16

38

11

2031

9

«S

Mean

3.04

3.681.41

0.290.27

0.28

0.25

0.20

0.260.58

0.42

5.37

'o C o r g

Range

0.79-4.81

2.10-6.400.30-2.63

0.07-0.530.07-0.50

0.14-0.35

0.16-0.42

0.11-0.26

0.15-0.370.15-2.02

0.08-1.31

0.57-16.5

Atomic C/N

Mean

13.3

13.111.1

5.58.4

9.3

11.9

10.8

18.316.0

12.4

25.8

Range

7.8-17.5

11.8-14.05.6-24.1

2.1-11.35.3-12.4

6.0-14.4

5.4-15.1

8.2-15.2

15.5-21.29.0-21.3

6.0-27.7

No. ofsamples

25

722

1511

4

5

3

28

43(red and green

11.3-36.5(

claystones)25

black shales)

Paleopro-ductivity

(g C/πfl/y.)

150

18299

2629

21

14

17

1836

38

480

a Fully described in the Site 530 summary (this volume).b Estimated from equation 7 of Muller and Suess (1979) (see text).

960 -

980

1 1000

E 1020

£ 1040CO

1060

1080 -

1100 °

6 8 10 12Total organic carbon (%)

14 16

Figure 5. Comparison of concentrations of total organic carbon ofblack shales, green claystones, and red claystones from Unit 8,Hole 53OA. (Black shale values are denoted as solid circles; red andgreen claystones as open circles.)

two interpretations are not mutually exclusive, and bothprocesses may have operated. The frequent interbed-ding of red, green, and black layers, and the commonbioturbation of much of the sediment but not in parts ofthe black shales, suggest that there was a delicate bal-ance between oxidizing and reducing conditions in thesediments and waters of the Angola Basin during theLate Cretaceous.

It appears that the Angola Basin was sufficiently oxy-genated during most of the Late Cretaceous to supportan active benthic infauna. There were periods of shorterand longer duration when bottom-water conditions fluc-tuated between oxic and anoxic. Pelagic, hemipelagic,and turbiditic sedimentation processes continued duringthe anoxic periods, but deposits contained and pre-served a higher concentration of organic matter, wererelatively unbioturbated, and subsequently formed theblack, organic-carbon-rich shales.

Lithologic Units 3 through 7 contain low amounts oforganic matter (Table 4, Fig. 4), with mean organic car-bon concentrations near the value of 0.2% typical ofpelagic marine sediments (Degens and Mopper, 1976),and ranges similar to the range of 0.1 to 0.5 % in DSDPLeg 58 sediments (Waples and Sloan, 1980). In Unit 7,the mean organic carbon value is elevated and the rangeis expanded by two samples of a Santonian black shalelayer (Samples 530A-86-5, 31-32 cm and 33-34 cm);other samples in this unit average 0.22% organic car-bon. These low concentrations are similar to the meanorganic carbon value of 0.3% compiled by Mclver(1975) from measurements done during DSDP Legs 1through 31 and reflect a combination of low productionand poor preservation of organic matter at Site 530from the Santonian (84 m.y. ago) through the middleMiocene (10.5 m.y. ago).

Beginning in Unit 2, concentrations of organic car-bon increase to a mean value of 3.68% in Unit lb beforedecreasing slightly to average 3.04% in Unit la (Table4). Sediments of these Neogene units contain more bio-genous components than do those deeper in the section,and their sedimentation rates increase to 65 m/106 y.in Pleistocene Units la and lb. Paleoproductivity esti-mates increase from 99 g C/m2/y., typical of coastalareas (Ryther, 1969) in Unit 2 to 150 to 182 g C/m2/y. in

978


Unit 1. These higher rates are similar to those for up-welling areas off northwest Africa (Muller and Suess,1979). Higher sedimentation rates in the uppermost unitmay have contributed to better preservation of organicmatter, resulting in erroneously high estimates of paleo-productivity, but the increase in siliceous biogenic sedi-ment components which accompanies the higher organ-ic carbon values (Hay et al., 1982; Site 530 summary,this volume) indicates that the higher concentrations oforganic carbon result from increased productivity sincethe mid to late Miocene.

Debris-flow deposits make up much of the thickness-es of Units 1 and 2 and represent downslope transportof biogenic sediments originally deposited on the WalvisRidge south of Site 530 (Fig. 1). There are many similar-ities in organic carbon content, C/N ratios, and litho-logic composition between Neogene sediments from Site530 (Table 2) and those from Site 532 (Table 3). Becausethe sediments at Site 530 appear to have had the sameorigin and history as sediments at Site 532, further dis-cussion of them will be incorporated into the discussionof Site 532.


The similarities in organic matter content of Neogenesediments from Sites 530 and 532 are shown in Figure 6.Values of organic carbon above the middle Miocene aresubstantially higher than the average DSDP value of0.3% (Mclver, 1975). Throughout these organic-car-bon-rich layers, atomic C/N ratios of organic matter re-main ca. 15 despite variations in carbon concentration.Because changes in the degree of organic matter preser-vation would probably cause alterations of C/N ratios(Muller, 1977; Waples and Sloan, 1980), the lack of suchvariability suggests that the fluctuations in amount oforganic carbon result from changes in rate of input.These organic matter patterns may therefore record thehistory of biological productivity off southwest Africa,even though neither DSDP site is located under the pres-ent up welling areas, which are generally closer to shore(Bishop et al., 1978).

Sedimentation rates and organic carbon contents ofthe Site 532 lithologic units can be used to estimatepaleoproductivity rates since late Miocene times in wa-ters overlying Walvis Ridge. Characteristics of the threelithologic sub-units recovered at Site 532 and their es-timated paleoproductivities are given in Table 5. Thehighest paleoproductivity (192 g C/m2/y.) occurs inUnit la (Pleistocene) and not in Unit lb (Pleistocene-Pliocene), contrary to what would be expected fromsimple examination of organic carbon content, sedimentlithology, and sedimentation rate. This discrepancy mayarise because the expression developed by Muller andSuess (1979) adjusts for larger fractions of organic mat-ter formed in surface waters becoming incorporated in-to the bottom under zones of greater productivity, butdoes not account for the later diagenetic losses describedby Waples and Sloan (1980). The disagreement betweenactual sediment biogenic character and calculated ratesof organic matter production suggests that the originallevel of organic carbon in Unit lb (and probably Unit

100 -

-9 200 -

300

V " ^ Site 530J Angola Basin

— 2 —

— 5 —

••.•:.<•t .

•••t

•

2 3 4 5

Organic carbon (%)

6 10 20Age (Ma) Atomic C/N

300

Site 532Walvis Ridge

— 2 —

— 5 —

2 3 4

Organic carbon

10 20Age (Ma) Atomic C/N

Figure 6. Organic carbon concentrations and atomic C/N ratios ofNeogene biogenic sediments from Sites 530 and 532. (Sedimentages are indicated in millions of years ago.)

lc) has been diminished by postdepositional degrada-tion. Indeed, microbial activity to depths as great as ca.200 m is indicated by copious amounts of biogenic gasesin these sediments (Site 532 summary, this volume).

Siesser (1980) presents evidence from Site 362 adja-cent to Site 532 on the Walvis Ridge that South Atlanticplankton changed from warm- to cold-water types inmiddle to late Miocene times. He interprets this as indi-cating the establishment of the modern Benguela Cur-rent system. As surface water temperatures decreased,surface productivity evidently increased in response tonutrient upwellings associated with the Benguela sys-tem. Information from Sites 530 and 532 supports theconclusions that the onset of the Benguela upwellingsystem occurred in the late Miocene (Diester-Haass andSchrader, 1979; Siesser, 1980). Because soft-sedimentsampling at both sites was done by hydraulic piston cor-er, much of the sediment disturbance that accompaniedthe rotary drilling at Site 362 was avoided, and a moredetailed sedimentary record of the history of this cur-rent system is available.

The strong similarity in patterns of biogenic sedimentcomponents between Sites 530 and 532 (Fig. 6) indicatesa late Miocene onset and a late Pliocene maximum ofupwelling off southwest Africa. At Site 530, turbidites

979


Table 5. Summary of organic matter contents and paleoproductivities of Site 532 sediments.

Lithologicunita

la

lb

lc

Depth(m)

0-50

50-114

114-291

Age

Pleistocene

Pleistocene-Pliocene

Pliocene-late Miocene

Description

Diatom nanno-foramooze and marl

Nannofossil diatomsmarl and marl

Nannofossil marl

Sedimen-tation

(m/m.y.)

40

62

25

% C o r g

Mean

3.36

3.54

2.25

Range

0.99-9.75

1.36-6.41

0.10-5.87

Atomic C/NMean

14.5

14.2

14.7

Range

4.8-26.3

4.7-21.7

5.9-30.1

No. ofsamples

30

37

84

Paleopro-ductivity"

(g C/m2/y.)

192

177

148

Fully described in the Site 532 summary (this volume).Estimated from equation 7 of Muller and Suess (1979) (see text).

and debris-flow deposits rich in organic matter and indiatoms began to accumulate in the late Miocene andbecame more extensive through the Pliocene. Thesedeposits are poor in carbonate because of proximity tothe calcite compensation depth, yet otherwise closelyresemble the sediments found at Site 532 on the WalvisRidge. The fact that they did not begin to accumulate inthe Angola Basin until late Miocene times means thatabundant amounts of biogenic sediments subject toslumping were not being formed before that time. Be-cause of the steep northern slope of the Walvis Ridge(see Fig. 1), downslope transport to the Angola Basinand subsequent reburial must have been rapid; other-wise organic matter would not be so well preserved.

Sediments from Sites 530 and 532 contain consider-able variability in organic carbon concentrations (Fig.6), with periodicities of 30,000 to 50,000 years (Hay etal., 1982; Site 532 summary). Other cyclic patterns havebeen observed in marine sediments. Dean et al. (1981)report 44,000-year periodicities in Oligocene-Miocenebiogenic sediments from the Sierra Leone Rise offnorthwest Africa. Rea (1982) infers 42,000-year cyclesin the intensity of Pleistocene tradewinds over the east-ern equatorial Pacific from variations in grain size ofthe eolian sedimentary component. This periodicity cor-responds to the tilt cycle of the Earth, which affects theglobal distribution of incident solar radiation. Wind in-tensities shift in response to changes in latitudinal tem-perature gradient and may cause a similar periodicity inmarine productivity (Rea, 1982). The cyclicity in bio-genic sediment composition which is best preserved atSite 532 may reflect episodes of stronger winds and en-hanced up welling.

SUMMARY

A series of thin black shale layers containing up to16.5% organic carbon are interbedded in Albian toConiacian organic-carbon-lean red and green claystonesat Site 530 in the Angola Basin. The conditions whichled to formation of the black shales required a combina-tion of high biological productivity and enhanced pres-ervation of organic matter. Presence of closely associ-ated red claystones and evidence of burrowing argueagainst long periods of bottom-water anoxia in the LateCretaceous Angola Basin, but do not preclude shortperiods of mildly anoxic conditions nor an expandedand intensified midwater oxygen minimum zone. Thesame set of conditions need not have prevailed through-

out the sediments deposited at Site 530 nor throughoutthe Cretaceous Atlantic Ocean.

Neogene biogenic ooze recovered by hydraulic pistoncoring at Sites 530 and 532 contains high concentrationsof high organic carbon which began to accumulate dur-ing the late Miocene and records the onset of upwellingoff southwest Africa. Productivity increased to a maxi-mum in the late Pliocene and has declined somewhat sincethat time. Cycles of lower and higher productivity haveperiodicities of 30,000 to 50,000 years and may reflectvariations in global wind intensities related to the tilt cy-cle of the Earth.

ACKNOWLEDGMENTS

We thank W. E. Dean, D. K. Rea, and C. P. Summerhayes fortheir thoughtful and helpful reviews of this paper. Analysis of thelarge number of samples was possible only with the help of W. Meyerand M. Nohara onboard D/V Glomar Challenger and of R. M.Glover, P. A. Pulver, M. S. Williams, M. J. Leenheer, and O. E.Kawka at The University of Michigan.

REFERENCES

Arthur, M. A., and Natland, J. H., 1979. Carbonaceous sediments inthe North and South Atlantic: The role of salinity in stable stratifi-cation of Early Cretaceous basins. In Talwani, M., Hay, W., andRyan, W. B. F., (Eds.), Deep Drilling Results in the AtlanticOcean: Continental Margins and Paleoenvironment: Washington(Am. Geophys. Union), pp. 375-401.

Bishop, J. K. B., Ketten, D. R., and Edmond, J. M., 1978. The chem-istry, biology, and vertical flux of particulate matter from the up-per 400 m of the Cape Basin in the southeast Atlantic Ocean.Deep-SeaRes., 25:1121-1161.

Dean, W. E., Gardner, J. V., and Cepek, P., 1981. Tertiary carbon-ate-dissolution cycles on the Sierra Leone Rise, eastern equatorialAtlantic Ocean. Mar. Geol., 39:81-101.

Degens, E. T., and Mopper, K., 1976. Factors controlling the distri-bution and early diagenesis of organic material in marine sedi-ments. In Riley, J. P., and Chester, R. (Eds.), Chemical Oceanog-raphy (Vol. 6): New York (Academic Press), 59-113.

Diester-Haass, L., and Schrader, H.-J., 1979. Neogene coastal upwell-ing history off northwest and southwest Africa. Mar. Geol., 29:39-53.

Erdman, J. G., and Schorno, K. S., 1978. Geochemistry of carbon:Deep Sea Drilling Project Leg 40. In Bolli, H. M., Ryan, W. B. F.,et al., Init. Repts. DSDP, 40: Washington (U.S. Govt. PrintingOffice), 651-658.

Firstbrook, P. L., Funnell, B. M., Hurley, A. M., and Smith, A. G.,1979. Paleoceanic Reconstructions: Washington (National ScienceFoundation).

Förster, R., 1978. Evidence for an open seaway between northern andsouthern proto-Atlantic in Albian times. Nature, 272:158-159.

Foresman, J. B., 1978. Organic geochemistry, DSDP Leg 40, conti-nental rise of Southwest Africa. In Bolli, H. M., Ryan, W. B. F.,et al., Init. Repts. DSDP, 40: Washington (U.S. Govt. PrintingOffice), 557-567.

980


Goodell, H. G., 1972. Carbon/nitrogen ratio. In Fairbridge, R. W.(Ed.), Encyclopedia of Geochemistry and Environmental Science:New York (Van Nostrand Reinhold), pp. 136-142.

Hay, W. W., Sibuet, J.-C, and Leg 75 Shipboard Scientific Party,1982. Sedimentation and accumulation of organic carbon in theAngola Basin and on Walvis Ridge: Preliminary results of DeepSea Drilling Project Leg 75. Geol. Soc. Am. Bull., 93:1038-1058.

Heezen, B. C , and Hollister, C. D., 1971. The Face of the Deep:New York (Oxford University Press).

Leventhal, J. S., Crock, J. G., Mountjoy, W., Thomas, J. A., Shale,V. E., Briggs, P. H., Wahlberg, J. S., and Malcom, M. J., 1978.Preliminary analytical results for a new US Geological Survey De-vonian shale standard, SDO-1. USGS Open File Report, 78-447.

Mclver, R., 1975. Hydrocarbon occurrences from JOIDES Deep SeaDrilling Project. Proc. Ninth World Pet. Congr., Tokyo: London(Applied Science Publ.), 2:269-280.

Menzel, D. W., 1974. Primary productivity, dissolved and particulateorganic matter, and the sites of oxidation of organic matter. InGoldberg, E. D. (Ed.), The Sea (Vol. 5): New York (Elsevier),659-678.

Muller, G., and Gastner, M., 1971. The "karbonate bomb," a simpledevice for determination of the carbonate content in sediments,soils, and other materials. N. Jahrb. Mineral. Mh., 10:466-469.

Muller, P. J., 1977. C/N ratios in Pacific deep-sea sediments: Ef-fect of inorganic ammonium and organic nitrogen compoundssorbed by clays. Geochim. Cosmochim. Acta, 41:765-776.

Muller, P. J., and Suess, E., 1979. Productivity, sedimentation rate,and sedimentary organic matter in the oceans—I. Organic carbonpreservation. Deep-Sea Res., 26A: 1347-1362.

Rea, D. K., 1982. Fluctuation in eolian sedimentation during the pastfive glacial-interglacial cycles: A preliminary examination of datafrom Deep Sea Drilling Project Hole 5O3B, eastern equatorial Pa-cific. In Prell, W. L., Gardner, J. V., et al., Init. Repts. DSDP,68: Washington (U.S. Govt. Printing Office).

Ryther, J. H., 1969. Photosynthesis and fish production in the sea.Science, 166:72-76.

Siesser, W. G., 1980. Late Miocene origin of the Benguela upwellingsystem off northern Namibia. Science, 208:283-285.

Tissot, B., Deroo, G., and Herbin, J. P., 1979. Organic matter inCretaceous sediments of the North Atlantic: Contributions to sed-imentology and paleogeography. In Talwani, M., Hay, W., andRyan, W. B. F. (Eds.), Deep Drilling Results in the Atlantic Ocean:Continental Margins and Paleoenvironment: Washington (Am.Geophys. Union), pp. 362-374.

Waples, D. W., and Sloan, J. R., 1980. Carbon and nitrogen dia-genesis in deep sea sediments. Geochim. Cosmochim. Acta, 44:1463-1470.

Date of Initial Receipt: May 19, 1982

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deep sea drilling project initial reports volume 75chn analyses of sediments and rocks sampled...

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