Victoria Univ., Wellington, Res. Sch. Earth Sci., New Zealand

Twenty-nine species of foraminifera were recovered from the upper Oligocene (115-223 m interval sub-bottom) of the MSSTS-1 drillhole. The total fauna consists of 14, 13, and 2 species of agglutinated, calcareous benthic, and planktonic species, respectively. This part of the MSSTS-1 succession is correlated by foraminifera with late Oligocene assemblages in the basal sediments (Units 4 and 2J) of DSDP Site 270, south-central Ross Sea. Three informal assemblage zones are recognised, but the utility of these subdivisions is not as yet tested beyond the immediate drill-site. Foraminiferal distribution patterns within and between the three zones are closely correlated with grain size and other variations in the enveloping sediments. The entire succession was deposited on southwest margins of the Victoria Land Basin, in a complex of relatively shallow water glacial and glaciomarine environments. Data derived from diversity fluctuations, faunal associations and the stratigraphic distribution of minimum diversity intervals are interpreted in terms of bathymetric trends and glacial/interglacial history. Seismic reflector and polarity changes commonly coincide with low diversity very shallow water assemblages or barren intervals, perhaps implying that there is an ice-loading effect on the paleomagnetic record.