British Antarctic Survey, United Kingdom

CRP-2/2A hole, drilled at 77.006 degrees S and 163.719 degrees E, about 14 km east of Cape Roberts, in the Ross Sea, reached 624 metres below sea floor and recovered a thick Miocene-Oligocene succession capped by a thin Pliocene-Quaternary cover. As many as 324 macrofossiliferous horizons have been identified in core CRP-2/2A, although the poor preservation state of most fossils prevents a full appreciation of their taxonomic identity. The macrofossils identified in core CRP-2/2A belong to Mollusca, Annelida, Cnidaria, Brachiopoda, Bryozoa, Echinodermata, Porifera and Vertebrata and represent an important source of palaeontological information on the former Antarctic biota. In particular, the CRP-2/2A drill core contains the most diverse Oligocene marine invertebrate macrofauna hitherto reported from East Antarctica. Early Miocene and Late Oligocene macrofossil assemblages are consistent with relatively cold (sub-polar) climatic conditions. One of the most significant findings in the drill core CRP-2/2A is the discovery of mussel assemblages dominated by modiolid bivalves within Early Oligocene sediments, suggestive of sea-bottom conditions characterized by high H (sub 2) S production. Modiolid bivalves are a strong indication of warmer-than-present climatic conditions. Many taxa are comparable to species recovered from coeval sediments drilled in the Ross Sea (DSDP Sites 270 and 272) and McMurdo Sound (CIROS-1).