von Rad, U., Haq, B. U., et al., 1992Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 122

56. DATA REPORT: CARBON ISOTOPE STRATIGRAPHY OF PALEOGENE BULK SEDIMENTS,HOLE 762C (EXMOUTH PLATEAU, EASTERN INDIAN OCEAN)1

E. Thomas,2 N. J. Shackleton,3 and M. A. Hall3

ABSTRACT

Carbon isotope measurements were made on bulk sediments from the Paleogene calcareous sequence recoveredat Ocean Drilling Program Site 762 (Hole 762C) on the central Exmouth Plateau, eastern Indian Ocean. The verypositive δ13C values that characterize the early/late Paleocene boundary and the very rapid trend toward lightervalues in the latest Paleocene, as observed at other sites worldwide, are clearly present in the record from Hole762C, as is the short excursion to extremely light values close to the Paleocene/Eocene boundary. The highestvalues in the upper Paleocene maximum at Site 762 are close to those at mid-latitude South Atlantic sites on WalvisRidge, but slightly lower than those from the high latitude Sites 689 and 690 (65°S; Maud Rise, Weddell Sea). These513C events will be of value in long-distance stratigraphic correlations; especially the short, but extreme excursionat the end of the Paleocene may be useful in clearing up the stratigraphic correlation problems for that interval. Site762 values for the upper Eocene resemble the pattern at Walvis Ridge more closely than do the values for Sites 689and 690 (Maud Rise); the latter showed a positive excursion in that interval. The bulk carbon isotopic record seemsto be more similar between low- and mid-latitude sites, even in different ocean basins, than between low and highlatitudes.

INTRODUCTION

Site 762 (19°53.23'S, 112°15.24'E) was drilled in about 1360m water on the western flank of the central Exmouth Plateau.Well-preserved Cenozoic nannofossil oozes and chalks wererecovered, and recovery with the extended core barrel (XCB)was reasonably good but not excellent (66.8% for the Paleo-gene chalk interval studied). The microfossils studied indicatea low-latitude, open-ocean environment of deposition throughthe Cenozoic (Haq, von Rad, O'Connell, et al., 1990). Despitethe great burial depth of the Paleogene section (Table 1), thesediments appear to have preserved a reliable carbon isotopesignal.

For most purposes stable isotope analyses of bulk sedi-ments are of very little value, and one has to analyze mono-specific or at least monogeneric assemblages of benthic fora-minifers and size-controlled, monospecific samples of plank-tonic foraminifers (e.g., Berger et al., 1978). It is useful,however, to analyze bulk sediment to obtain appropriate datato contribute to our understanding of the history of theoceanic carbon budget (e.g., Shackleton, 1987). In this reportwe present a data set from Site 762, at low latitudes in theeastern Indian Ocean, to add to and compare with data setsfrom low latitudes in the Pacific (Shackleton et al., 1985), themid-latitudes in the southern Atlantic (Renard et al., 1983;Shackleton and Hall, 1984; Shackleton, 1986), and high lati-tudes (Shackleton and Hall, 1990).

There are significant spatial variations in δ13C in oceansurface waters today (Kroopnick et al., 1977), but the spatialvariability in the δ13C content of surface sediments is smallcompared with the range of values observed for the Cenozoic(Shackleton, 1987), which suggests that the bulk sedimentrecord of δ13C may be useful in stratigraphic correlations. This

1 von Rad, U., Haq, B. U., et al., 1992. Proc. ODP, Sci. Results, 122:College Station, TX (Ocean Drilling Program).

2 University of Cambridge, Department of Earth Sciences, Downing Street,Cambridge CB2 3EQ, United Kingdom.

3 University of Cambridge, Subdepartment of Quaternary Research, God-win Laboratory, Free School Lane, Cambridge CB2 3RS, United Kingdom.

additional data set can help evaluate the stratigraphic use ofbulk δ13C data.

ANALYTICAL DATA AND CONCEPTSSamples from Hole 762C, weighing a few milligrams, were

taken from Cores 122-762C-2X through -41X (171 to 540 mbsf,corresponding to about 35-65 Ma), then dried and vacuumroasted at 400°C to remove any organic contaminants. Thesamples were then reacted with 100% phosphoric acid at 90°Cusing a VG Isotech Isocarb common acid bath system. Theevolved carbon dioxide was analyzed in a VG Isotech SIRAseries II mass spectrometer. The results were calibrated toPDB by repeated analysis of a carbonate standard. Analyticalaccuracy is better than 0.08%o.

Measurements are listed in Table 1. As an aid to prelimi-nary evaluation of the data and comparison with records fromother sites, each sample is assigned an age based on themagnetostratigraphic record in Galbrun (this volume, chapter42) and the calcareous nannofossil record in Siesser andBralower (this volume). The numerical ages follow Berggrenet al. (1985), with the nannofossil zone boundary correctionsin Aubry et al. (1988). The age tie-points are listed in Table 2.

DISCUSSION

Figure 1 shows the δ13C record for Hole 762C plotted vs.depth, and on the time scale obtained from Table 2. Thepronounced upper Paleocene peak in δ13C values around 60Ma (time scale of Berggren et al., 1985) is clearly present, asis the rapid decline in values at around the Paleocene/Eoceneboundary. The peak values of δ13C at around 60 Ma are verysimilar to those at mid-latitude Deep Sea Drilling Project(DSDP) Sites 525,527, and 528 (Walvis Ridge; Shackleton andHall, 1984), but lower than those at high-latitude Sites 689 and690 (Shackleton and Hall, 1990). It has been demonstrated fordata from the Maud Rise on planktonic and benthic foramin-ifers (Stott et al., 1990; Kennett and Stott, 1990, 1991), as wellas in bulk values (Shackleton and Hall, 1990), that there is ashort "overshoot" to very light δ13C values at the end of thislong-term decline in δ13C values. A coeval negative excursionwas observed in sediments from Site 738 (Antarctic Indian

897

Table 1. Stable isotope analyses, Hole 762C.

Sample(Hole762C)

2X-1,128-1302X-4, 85- 873X-1, 23- 253X-4, 72- 744X-1, 27- 294X-4, 72- 745X-1,128-1306X-1,132-1346X-4, 77- 797X-1, 22- 247X-4, 72- 748X-1, 48- 508X-4, 71- 739X-1, 73- 75

10X-1, 79- 8110X-4, 72- 7411X-1,132-13411X-4, 71- 7312X-1,131-13312X-4, 72- 7413X-1,129-13114X-1,130-13214X-4, 70- 72i *v 1 19^ 1 9^1 JA" l,l-J"li»J

15X-CC,13- 1516X-1,121-12316X-3, 79- 8117X-2, 32- 3417X-5,131-13318X-1, 77- 7918X-2, 79- 8118X-3, 79- 8118X-4, 71- 7318X-5, 80- 8218X-6, 79- 8119X-1, 82- 8419X-2, 71- 7319X-4, 72- 7420X-1, 82- 8420X-2, 71-7320X-3, 78- 8020X-4, 51- 5321X-1, 78- 8021X-2, 67- 6922X-1, 72- 7422X-2, 71-7322X-3, 60- 6222X-4, 66- 6822X-5, 67- 6922X-6, 72- 7423X-1, 67- 6923X-2, 66- 6823X-3, 54- 5624X-1, 57- 5924X-CC, 8- 1025X-1, 70- 7225X-2, 78- 80

Depth(mbsf)

171.28175.35179.73184.72189.27194.22199.78209.32213.27217.72222.72227.48232.21237.23246.79251.22256.82260.71266.31270.22275.79285.30289.20

297.50304.21306.79314.32319.81322.77324.29325.79327.21328.80330.29332.32333.71336.72341.82343.21344.78346.01351.28352.67360.72362.21363.60365.16366.67368.22370.17371.66373.04379.57380.50389.20390.78

Age(Ma)

35.38335.57635.78436.02136.23636.47136.73537.18737.37437.58537.83038.13838.44338.76839.38639.89840.83041.47842.41043.06144.02045.51846.13146.74047.04047.76548.04348.85749.45049.71649.93450.09650.24950.44550.65450.93951.13451.55652.07452.14952.23452.30152.58652.70553.59853.76353.91754.09054.25854.43054.66354.81154.96455.59355.66255.95756.011

type

bulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulk

δ 1 8 θ

1.090.670.630.220.070.08

-0.120.140.06

-0.19-0.59-0.48-0.01-0.070.100.31

-0.01-0.050.280.14

-0.210.450.08n i<U.Jo

0.210.360.050.09

-0.22-0.40-0.23-0.23-0.32-0.44-0.51-0.61-0.62-0.73-0.83-1.23-1.03-0.93-0.94-0.86-0.99-0.74-0.90-0.71-1.15-1.08-0.90-1.03-1.01-1.03-1.02-0.73-0.90

δ 1 3 c

1.831.942.252.011.731.301.501.781.851.721.771.891.621.631.811.862.012.411.871.971.881.881.861 *7~71.1/

1.541.811.901.791.701.611.831.851.921.321.801.771.791.480.771.630.731.141.071.161.121.240.931.110.831.071.040.990.760.961.251.201.46

Table 1 (continued)

Sample

(Hole762C)

25X-3, 70- 7225X-4, 80- 82

25X-5, 35- 3726X-1, 15- 1626X-1, 75- 7726X-2, 15-1626X-2, 68- 7026X-3, 15-1626X-3, 67- 6926X-4, 15-1627X-1, 15- 1627X-1, 63- 6526X-4, 65- 6726X-5, 15-1627X-2, 15- 1627X-2, 61-6326X-5, 68- 7027X-3, 15-1626X-CC, 6- 827X-3, 65- 6727X-4, 15-1627X-4, 55- 5727X-CC.15- 1628X-1, 15- 1628X-1.65-6728X-CC15- 1628X-CC,23- 2529X-1, 15- 1629X-1, 64- 6629X-2, 16-1729X-2, 65- 6729X-3, 15- 1629X-3, 77- 7929X-CC,15- 1630X-1, 15- 1630X-1, 63- 6530X-2, 15- 1630X-2, 57- 5930X-3, 15- 1630X-3, 66- 6830X-4, 15- 1630X-4, 57- 5930X-CC,15- 1631X-1, 74- 7631X-2, 72- 7431X-3, 74- 7631X-4, 76- 7831X-5, 75- 7731X-6, 74- 7632X-1, 75- 7732X-2, 68- 7032X-CC,34- 3633X-1, 74- 7633X-2, 71- 7333X-3, 66- 6833X-4, 68- 7033X-5, 70- 72

Depth

(mbsf)

392.20393.80

394.85398.15398.75399.65400.18401.16401.67402.65402.66403.13403.15404.15404.16404.61404.68405.66405.86406.15407.16407.55408.79412.16412.65413.88413.95421.65422.14423.16423.65424.65425.27426.10431.15431.63432.65433.07434.15434.66435.65436.07436.67441.24442.72444.24445.76447.25448.74450.75452.18453.75460.24461.71463.16464.68466.20

Age

(Ma)

56.05956.114

56.16456.43756.51456.59556.64256.73056.77656.86356.86456.90756.90856.99856.99957.03957.04657.13457.15157.17757.26757.30357.41457.71657.76057.868

57.87758.56758.61158.84858.99959.24959.27559.31159.52759.54759.51059.60959.65559.67759.71959.73759.76359.95960.02260.08760.15260.21660.28060.36660.42760.49460.77260.83560.89760.96261.027

type

bulkbulk

bulkfinebulkfinebulkfinebulkfinefinebulkbulkfinefinebulkbulkfinebulkbulkfinebulkfinefinebulkfinebulkfinebulkfinebulkfinebulkfinefinebulkfinebulkfinebulkfinebulkfinebulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulk

Note: *End Paleocene benthic foraminiferal

δ 1 8 θ 5 1 3 C

-0.78 1.53-0.92 1.48

-0.78 0.64-0.88 1.26-0.85 1.15-1.13 1.22-0.84 1.16-0.95 1.26-0.81 1.40-0.52 1.47-0.89 1.30-0.93 1.25-0.81 1.37-0.55 1.37-0.82 1.33-0.78 1.51-0.79 1.34-0.89 1.69-0.88 1.41-1.04 1.41-1.01 1.73-0.87 1.49-1.09 1.84-0.92 1.80-1.20 1.02*-1.28 1.29

-0.81 2.33-0.94 2.67-1.03 2.05-0.92 3.43-0.76 2.81-0.83 3.07-0.68 2.80-0.83 3.28-0.74 2.99-0.47 3.11-0.63 3.19-0.51 3.01-0.65 3.28-0.35 2.94-0.61 3.15-0.49 2.88-0.45 3.23-0.69 2.56-0.07 3.11-0.33 3.11-0.61 3.06-0.55 3.07-0.46 2.67-0.44 2.69-0.25 2.80-0.59 2.42-0.70 2.72-0.52 2.45-0.80 2.60-0.75 2.39-0.61 2.18

extinction

898

DATA REPORT

Table 1 (continued).

Sample(Hole762C)

33X-6, 76-34X-1, 73-34X-2, 69-34X-3, 75-34X-4, 79-34X-5, 70-35X-1, 61-35X-2, 63-

7875717781726365

36X-CC,34- 3637X-1, 78- 8037X-4, 77-7938X-1, 73-38X-4, 76-39X-1, 76-39X-4, 69-40X-1, 73-40X-4, 73-41X-1, 77-41X-4, 73-

7578787175757975

Depth(mbsf)

467.76469.73471.19472.75474.29475.70479.11480.63488.60498.28502.77507.73512.26517.26521.69526.73531.23536.27540.73

Age(Ma)

61.09461.17861.24161.30861.37461.43461.58061.64561.98662.40162.59362.80562.99963.41064.37464.58764.76664.95665.146

type

bulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulkbulk

δ 1 8 θ

-0.62-0.74-0.83-0.60-0.60-0.42-0.73-0.51-0.74-0.62-0.80-0.56-0.87-0.75-1.10-1.00-0.98-1.11-1.07

2.402.472.222.082.132.171.931.891.671.671.921.911.691.491.291.131.431.341.44

Note: Age estimates after Galbrun (this volume, chapter 42) andSiesser and Bralower (this volume); Table 2.

Table 2. Age tie-points used to determine the ages of samples, as shownin Table 1.

Datum

NP20/NP21NP20/NP19C16R/C17NC19N/C19RC19R/C20NC20N/C20RC20R/C21NC21N/C21RC21R/C22NC22N/C22RC24N-1/C24R-1C24R-1/C24N-2C24N-2/C24R-2C24R-2/C25NC25N/C25RC26R/C27NC27N/C27RC27R/C28NC28R/C29N

Depth,mbsf

199.05222.25249.01273.46276.01289.45310.22328.05339.53351.90376.70380.44394.58422.46424.45512.98518.73519.59540.39

Age,Ma

36.737.839.5343.6044.0646.1748.7550.3451.9552.6255.3755.6656.1458.6459.2463.0363.5464.2966.50

Ocean; Barrera and Keller, 1991) and from the Walvis Ridge(Thomas and Shackleton, unpubl. data). This short negativepeak occurs at the same level as the extinction of manyspecies of deep-sea benthic foraminifers, including Gave-linella beccariiformis (Thomas, 1990; Kennett and Stott,1991). At Site 762 there is a similar but less extreme drop inδ13C values of bulk carbonate at the extinction of G. beccari-iformis (Fig. 2). This short-lived event could thus be avaluable tool for high-precision stratigraphic correlation in theinterval around the Paleocene/Eocene boundary, where

stratigraphy is extremely difficult because of the brackishcharacter of the type sections of the Paleocene (Aubry et al.,1986, 1988).

At high-latitude Sites 689 and 690 there is an interval ofhighly positive δ13C values in the uppermost Eocene (around37-39 Ma). This interval is not present at Site 762 and islikewise absent at the mid-latitude Walvis Ridge sites(Shackleton and Hall, 1984; 1990). Thus it appears that thebulk carbon isotope record can be very useful in some partsof the geological record, but it needs to be interpreted withcare.

ACKNOWLEDGMENTS

We are grateful to Dr. S. 0'Connell, the ODP shipboardscientist for Leg 122, for help in obtaining samples, in gettingthis report presented in Volume 122, and in assisting inobtaining the information needed to document the age-modelfor Site 762. We thank one anonymous reviewer for commentson the manuscript. This is University of Cambridge DEScontribution no. 2069.

REFERENCES

Aubry, M.-P., Berggren, W. A., Kent, D. V., Flynn, J. J., Klitgord,K. D., Obradovich, J. D., and Prothero, D. R., 1988. Paleogenegeochronology: an integrated approach. Paleoceanography,3:707-742.

Aubry, M.-P., Hailwood, E., and Townsend, 1986. Magnetic andcalcareous nannofossil stratigraphy of the lower Palaeogene for-mations of the Hampshire and London Basins. J. Geol. Soc.143:729-735.

Barrera, E., and Keller, G., 1991. Late Paleocene to early Eoceneclimatic and oceanographic events in the Antarctic Indian Ocean.GSA Progr. Abstr.,

Berger, W. H., Killingley, J. S., and Vincent, E., 1978. Stableisotopes in deep-sea carbonates: Box-Core ERDC-92, West Equa-torial Pacific. Oceanologica Acta 1:203-216.

Berggren, W. A., Kent, D. V., Flynn, J. J., and Van Couvering, J. A.,1985. Cenozoic geochronology. Geol. Soc. Am. Bull., 96:1407-1418.

Haq, B. U., von Rad, U., 0'Connell, S., et al., 1990. Proc. ODP, Init.Repts., 122: College Station, TX (Ocean Drilling Program)

Kennett, J. P., and Stott, L. D., 1990. Proteus and Proto-Oceanus:ancestral Paleogene oceans as revealed from Antarctic stableisotopic results. In Barker, P. F., Kennett, J. P., et al., Proc.ODP, Sci. Results, 113: College Station, TX (Ocean DrillingProgram), 865-880

Kennett, J. P., and Stott, L. D., 1991. Terminal Paleocene deep-seabenthic crisis: sharp deep-sea warming and paleoceanographicchanges in Antarctica. Nature,

Kroopnick, P. M., Margolis, S. V., and Wong, C. S., 1977. 513Cvariations in marine carbonate sediments as indicators of the CO2

balance between the atmosphere and oceans. In Andersen, N. R.,and Malahoff, A. (Eds.), The Fate of Fossil Fuel CO2 in theOceans: New York (Plenum), 295-321.

Renard, M., Richebois, G., and Letolle, R., 1983. Trace element andstable isotope geochemistry of Paleocene to Coniacian carbonatesamples from Hole 516F, comparison with North Atlantic andTethys sites. In Barker, P. F., Carlson, Johnson, D. A., et al., Init.Repts. DSDP, 72: Washington (U.S. Govt. Printing Office), 399-420.

Shackleton, N. J., 1986. Palaeogene stable isotope events. Palaeo-geogr., Palaeoclimatol., Palaeoecol., 57:91-102.

Shackleton, N. J., 1987. Carbon isotope record of the Cenozoic. InBrooks, J., and Fleet, A. J. (Eds.), Marine Petroleum SourceRocks: Oxford (Blackwell), 427-438.

Shackleton, N. J., and Hall, M. A., 1984. Carbon isotope data from Leg74 sediments. In Moore, T. C, Rabinowitz, P. D., et &L,Init. Repts.DSDP, 74: Washington (U.S. Govt. Printing Office), 613-619.

Shackleton, N. J., and Hall, M. A., 1990. Carbon isotope stratigraphyof bulk sediments, ODP Sites 689 and 690, Maud Rise, Antarctica.In Barker, P. F., Kennett, J. P., et al., Proc. ODP. Sci. Results,113: College Station, TX (Ocean Drilling Program), 985-989.

899

DATA REPORT

Shackleton, N. J., Hall, M. A., and Bleil, U., 1985. Carbon isotopestratigraphy, Site 577. In Heath, G. R., Burckle, L. D., et al, Init.Repts. DSDP, 86: Washington (U.S. Govt. Printing Office), 503-511.

Stott, L. D., Kennett, J. P., Shackleton, N. J., and Corfield, R. M.,1990. The evolution of Antarctic surface waters during the Paleo-gene: inferences from the stable isotopic composition of plank-tonic foraminifers, ODP Leg 113. In Barker, P. F., Kennett, J. P.,et al., Proc. ODP, Sci. Results, 113: College Station, TX (OceanDrilling Program), 849-864

Thomas, E., 1990. Late Cretaceous through Neogene deep-seabenthic foraminifers (Maud Rise, Weddell Sea, Antarctica). InBarker, P. F., Kennett, J. P., et al., Proc. ODP, Sci. Results, 113:College Station, TX (Ocean Drilling Program), 571-594

Date of initial receipt: 19 July 1991Date of acceptance: 15 August 1991Ms 122B-195

0,5

delta 13C to PDB

1.5 2.5150

delta i3CtoPDB

1.5 2.5 3.5

550

Figure 1. δ13C data for bulk sediment in Hole 762C. A. Data plotted against depth in meters below seafloor(mbsf). B. Data plotted against numerical age. Time scale after Siesser and Bralower (this volume) and Galbrun(this volume, chapter 42).

900

DATA REPORT

delta 13Cto PDB

0.5 1.0 15 2.0 2.5 3.056.0

56.5-

57.0-

57.5"

58.0-

58.5

Figure 2. δ13C data for bulk sediment in Hole 762C, for the intervalbetween 56.0 and 58.5 Ma. The level of last appearance (LA) ofGavelinella beccariiformis is indicated.

901