Abstract:
This report is an integrated biostratigraphic study of foraminifera, calcareous nannofossils, radiolarians and palynomorphs from the Paleogene sequence at DSDP Site 277, SW Campbell Plateau. At 52 degrees S, this site is the southernmost record of pelagic sedimentation from Late Paleocene to Early Oligocene in the Pacific Ocean, including apparently continuous records across both the Paleocene-Eocene and Eocene-Oligocene boundaries. Studies of foraminifera and calcareous nannofossils incorporate new work with reviews of data presented in the initial report (Kennett, et al. 1975). Studies of radiolarians and palynomorphs are the first to be made of these groups at Site 277. Calcareous microfossils continue to provide the most reliable age control. Although radiolarians are considerably more abundant and diverse than indicated in the initial report, the ranges of key species in high-latitudes are not well-constrained. The locations of several epoch or stage boundaries have been shifted slightly to accommodate either new data or updated criteria. The base of the sequence is no older than Late Paleocene, while the top of the Paleogene part is no younger than Early Oligocene and is capped by 4.5 m of Pleistocene sediment. Major biohorizons are located as follows: base Waipawan = 460.5-453.5 m (based on foraminifera); base Eocene = 446.4m (nannofossils); base Mangaorapan = 435.6-434.5 m (nannofossils, foraminifera); base Porangan = 379.2-377.5 m (foraminifera); base Bortonian = 351.5-350.7 m (foraminifera); base Late Eocene (= base Kaiatan) = 263.8-263.5 m (nannofossils, radiolarians); base Whaingaroan = 189.6-187.5 m (foraminifera and nannofossils). The Eocene/Oligocene boundary cannot be precisely located by biostratigraphy. However, it can be indirectly located in the early Whaingaroan (186.8-171.4 m) based on a positive deviation in oxygen isotopes. This earliest Oligocene isotope event appears to be globally isochronous and is related to cooling of the world's oceans. Stable isotopes and biotic paleotemperature proxies suggest that cooling progressed in three distinct phases in the region of Site 277: (1) increased siliceous plankton productivity in mid-late Kaiatan; (2) marked decline in Discoaster abundance in mid Runangan, and (3) a 1 per thousand increase in both planktic and benthic delta (super 18) O in the earliest Whaingaroan. Systematic descriptions of radiolarian species encountered in this study, seven illustrative plates and a full table of occurrence, are presented in an Appendix.