Radiolarian Paleogene Biostratigraphy in the Southern Indian Ocean, Leg 120

Abstract

During Ocean Drilling Program Leg 120, an almost complete Paleogene sediment section on the Kerguelen Plateau in the southern Indian Ocean was recovered. The biostratigraphy of radiolarians from these sediments at Sites 748 and 749 is studied. A biostratigraphic framework established in low and middle latitudes is not applicable because of the absence of most zonal marker species. Biogenic opal is present only in middle Eocene to Oligocene sediments, and three new zoncs-Lychnocanoma conica, Axoprunum{l) irregularis, and Eucyrtidium spinosum zones-are proposed. The Paleogene antarctic radiolarian fauna is different from that in low and middle latitudes. Three new species, Axoprunum{l) irregularis, Eucyrtidium cheni, and Eucyrtidium spinosum, are described. INTRODUCTIONDuring Ocean Drilling Program (ODP) Leg 120, scientists drilled five sites in the Central and Southern Kerguelen plateaus of the southern Indian Ocean. Although Paleogene radiolarians were obtained from four sites (Sites 747-750), two sites have either poorly preserved shells (Site 747) or insufficient recovery (Site 750). For this study, I performed Paleogene radiolarian biostratigraphic work for Sites 748 and 749.Paleogene radiolarians from Leg 120 range in age from the middle Eocene to the late Oligocene. Although the radiolarian zonation of this interval has already been established for lowlatitude areas (Sanfilippo et al., 1985), this scheme cannot be applied to Leg 120 samples because of the absence of almost all zonal markers recognized in tropical or subtropical areas. For instance, genera Podocyrtis and Thyrsocyrtis, both of which are the most important groups for defining the middle to late Eocene zones, were not observed in Leg 120 samples at all.Few previous studies of Paleogene radiolarians in the Antarctic Sea area exist. Petrushevskaya (1975) described many Paleogene forms from Deep Sea Drilling Project (DSDP) Leg 29. Chen (1975) treated Paleogene samples from Sites 264 and 274 of DSDP Leg 28, which have ages of Eocene and early Oligocene, respectively. He described radiolarians in these two assemblages, but no one has yet tried to zone a Paleogene interval in the Antarctic Sea. Weaver (1983) also reported on Paleogene radiolarians from the Falkland Plateau region in the southwest Atlantic. Although he studied middle Eocene to early Oligocene radiolarians and interpreted them from a paleoenvironmental perspective, he did not zone them, and no plates of Paleogene radiolarians appear in his study.ODP has conducted several cruises in the Antarctic Sea area (Legs 113, 114, 119, and 120). During Leg 113, scientists recovered radiolarian-bearing Paleogene cores at several sites in the Weddell Sea (Barker, Kennett, et al., 1988). Abelmann (1990) tic, and many Paleogene cores (Paleocene to Oligocene) that included radiolarians were obtained (Ciesielski, Kristoffersen, et al., 1988). During Leg 119, northernmost and southernmost Kerguelen Plateau and Prydz Bay sites were drilled (Barron, Larsen, et al., 1989). Eocene and Oligocene ra...

Paleoceanography and Biostratigraphy of Paleogene Radiolarians from the Norwegian-Greenland Sea

“…Similar forms have been described in the literature, including Lophoconus titanothericeraos Clark and Campbell (1942), a more robust 3-segmented form, and Lophophaena (Lophophaenula) auriculaleporis Clark and Campbell (1942). Both species are from the Eocene of California; the former also has been reported from the Kerguelen Plateau by Takemura (1992).…”

“…Botryostrobus Bj0rklund, 1976;Dzinoridze et al, 1978;Petrushevskaya, 1975Petrushevskaya, , 1979Petrushevskaya and Kozlova, 1972;Benson, 1972;Lazarus and Pallant, 1989;Chen, 1975;Abelmann, 1990;Caulet, 1991;Takemura, 1992;Campbell, 1942, 1945;Westberg-Smith and Riedel, 1984;Kozlova and Gorbovets, 1966;J.-P. Caulet, R. Goll, andA. Sanfilippo, pers.…”

Foraminiferal, radiolarian, and dinoflagellate biostratigraphy of Late Cretaceous to Middle Eocene pelagic sediments (Muzzle Group), Mead Stream, Marlborough, New Zealand

“…Lychnocanoma amphitrite occurs at the base of Middle Eocene Zone RP11 at Mead Stream but does not appear until latest Eocene in low latitudes (Riedel & Sanfilippo 1978). The species is also known from the Middle Eocene of the southern Indian Ocean (Takemura 1992). The occurrence of Cryptocarpium cf.…”

“…Upper Limestone and Upper Marl faunas closely resemble Eocene faunas in the mid-to high-latitude Indian Ocean (Chen 1975;Takemura 1992) by the abundance of polar-spined spumellarians, Calocyclas spp., Eucyrtidium spp., and large theoperids such as Lychnocanoma amphitrite, Sethocyrtisl spp., and Lophocyrtis spp. Several of these species and genera have good potential for high-latitude biostratigraphy.…”

Methods

“…F8). For sediments older than 23 Ma, the lower resolution zonation scheme of Takemura (1992) was used. These zones are (upper to lower) Lychnocanoma conica, Axoprunum (?)…”