Cretaceous and Paleogene cores from the Kerguelen Plateau

E 38-8 SILICOFLAGELLATES

WATER MASSES

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Figure 2. Lithology and paleomagnetic stratigraphy of Eltanirt core 38-8, showing abundances of selected radiolarians and silicoflagellates, Dictyocha/Disfephanus ratios and a silicoflagellate temperature curve. Two different varieties of Distephanus speculum forma varians, described by Gran and Braarud (1935), are distinguished from one another in the figure by subscripts 1 and 2, which refer respectively to figures 68B and 68A of Gran and Braarud (1935, p. 390).

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8 8

SILICOFLASELLATE TEMPERATURE CURVEINC IAFTERMANDRA19721

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RADIOLARIANS

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0 25 50 75 10 5 10 15 20

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SILICEOUS OOZE MUD EI SAND MOTTLED SPECIES ABUNDANCES >0-2% 2-5% 5-10T', 1>106

gene planktonic zonation, magnetic reversals, and radiometric dates, Antarctic to the tropics. Antarctic Research Series, 15: 1-26. Gran, H. H., and T. Braarud. 1935. A quantitative study of the phytoplankton in the Bay of Fundy and the Gulf of Maine (including observations of hydrography, chemistry, and turbidity). Journal of the Biological Board of Canada, 1(5): 279.467. Hays, J . D.. and N. D. Opdyke. 1967. Antarctic radiolaria, magnetic reversals, and climate change. Science, 158: 10011011. Jendrzejewski, J . P., and G. A. Zarillo. 1971. Late Pleistocene paleotemperatures: si I icoflagel late and foraminiferal frequency changes in a subantarctic deep sea core. Antarctic Journal of the U.S, VT(S): 178-179. Kennett, J . P. 1972. The climatic and glacial record in Cenozoic sediments of the southern ocean. In: Palaeoecology of Africa. the surrounding islands and Antarctic (E. M. van Zinderen Bakker Sr., ed.). Cape Town, Balkema. VI: 59-78. Kennett, J . P., and C. A. Brunner. 1973. Antarctic Late Cenozoic glaciation: evidence for initiation of ice rafting and inferred bottom water activity. Geological Society of America. Bulletin, 84(6): 2043-2052. Mandra, Y. T., and H. Mandra. 1969. Silicoflagellates: a new tool for the study of antarctic Tertiary climates. Antarctic Journal of the U.S., TV(S): 172-174. Weaver, F. M. 1973. Pliocene paleoclimatic and paleoglacial history of East Antarctica recorded in deep sea piston cores. Sedimentology Research Laboratory, Department of Geology, Florida Stale University. Contribution, 36. 142 p. September-October 1973

Cretaceous and Paleogene cores from the Kerguelen Plateau, southern ocean F. AMRISAR KAI-IAROEDDIN, FRED M. WEAVER, SHERWOOD W. WISE, JR.

and

Department of Geology Florida State University, Tallahassee Although Pilo/Pleistocene sediments have been recovered from over 3,000 Eltanin cores, cores penetrating southern ocean sediments older than Miocene are so rare that they can be labeled 'flukes." The consistent recovery of older cores from the eastern flank of the Kerguelen Plateau, during the last phase of the Eltanin coring program, therefore is a noteworthy technical achievement and a subject of scientific interest. Cores taken on Eltanin Cruise 47, under the supervision of Weaver, include one containing Eocene chalk ooze. This core's age is in agreement with the presumed minimum age of the Plateau that is bounded on its eastern flank by magnetic anomaly 17 (McKenzie and Sclater, 1971). A primary 297

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I

Cretaceous coccoliths recovered in E!tanin

core 54-7 from the Kerguelen Plateau. On the left is Broinsonia bevieri Bukry (enlarged x10,000), and on the right is Lithastrinus f?oratis Stradner (enlarged x8,900).

objective of the next Eltanin cruise to the area (Cruise 54) was the recovery of still older cores at sites selected from seismic profiles by Weaver, L. A. Frakes, and F. A. Kaharoeddin. Of 10 cores obtained at the Cruise 54 sites, under Kaharoeddin's supervision, 3 recovered older sediment, including a 5-meter core that contains Cretaceous chalk ooze of Cenomanian age. The recovery of Cretaceous sediment was a marked surprise because it indicates that deep ocean sediments of the Kerguelen Plateau are considerably older than the minimum age suggested by magnetic anomaly patterns. A seaway of the incipient Indian Ocean was obviously well established by mid-Cretaceous time, in the area represented by these sediments. The microfossil content of the cores is being studied intensively. Patrick G. Quilty, West Australian Petroleum Party, Limited, is investigating the planktonic foraminifera, we are studying the calcareous nannofossils, and D. W. McCollum, P. M. Ciesielski, and Weaver are analyzing the siliceous microflora and fauna. Coccoliths from the Cretaceous core fall within the interval spanned by the Chiastozygus cuneatus and Eiffellithus turriseiffeli zones of Cepek and Hay (1969) and Thierstein (1971), as indicated by the presence of Broinsonia bevieri Bukry (fig.) and the absence of Micula staurophora decussata (Vekshina). The Cretaceous coccolith assemblages greatly are restricted in diversity with no more than 12 species represented, an indication of a high latitude paleo-site of deposition. The fact that the Cretaceous material consists of open marine carbonate ooze indicates that basement was not reached by the core, and older sediments may well be recovered from the area by further coring. Further recoveries of older material from this area significantly would help to determine the date and manner 298

of opening of this portion of the Indian Ocean. Participation in the Eltanin coring program was supported by National Science Foundation grant GV-27549, to Frakes. References Cepek, P., and W. W. Hay. 1969. Calcareous nannoplankton and biostratigraphic subdivision of the Upper Cretaceous. Gulf Coast Association of Geological Societies. Transactions, 19: 323-336. McKenzie, D., and J . G. Sciater. 1971. The evolution of the Indian Ocean since the Late Cretaceous. Geophysical Journal of the Royal Astronomical Society, 25: 437-528. Thierstein, H. R. 1971. Tentative Lower Cretaceous calcareous nannoplankton zonation. Eclogae Geologicae Helvetiae, 64: 459-488.

Early diagenesis of a deep sea bedded chert FRED M. WEAVER

and

SHERWOOD W. WISE, JR.

Department of Geology Florida State University, Tallahassee A primary research goal at the Antarctic Marine Geology Research Facility during the past year was the elucidation of early phases of diagenesis of deep sea bedded chert. Both volcanic (Gibson and Towe, 1971; Mattson and Pessagno, 1971) and biogenous origins (Ramsay, 1971) are currently postulated for such rock. Davies and Supko (1973) categorically state that the ANTARCTIC JOURNAL