Background

The aim of the CIROS project was to obtain a record of the Cenozoic history of the southwest corner of the Ross Sea by coring sedimentary strata offshore (Barrett 1982). Early Cenozoic strata are of particular interest because there are no strata of this age exposed on the Antarctic continent, and it is a period that is supposed to have seen the beginnings of Antarctic glaciation (Kennett 1977) and the rise of the Transantarctic Mountains (Fitzgerald et al. in press).

Previous drilling in the Ross Sea at DSDP-270 (Hayes, Frakes et al. 1975) and MSSTS-1 (Barrett 1986) had shown that Antarctic glaciation went back at least 25 and 30 million years respectively. The CIROS-1 drillhole was designed to core even older strata beneath the floor of McMurdo Sound (Fig. 1) to record the major glacial advances and retreats and to find out when they began. The core was also expected to show evidence of the uplift history of the Transantarctic Mountains.