Few calcareous nannofossil-bearing sections of Neogene age have been recovered in the extreme high latitudes of the Southern Ocean, particularly along the Antarctic margin. Haq (1976, 1980) noted the presence of coccoliths from high austral latitudes near the Antarctic margin, and Neogene nannofossils were recovered during Legs 113, 119, 120, 178, and 183 (Wise, 1983; Wei and Wise, 1990, 1992a, 1992b; Wei and Thierstein, 1991; Beaufort and Aubry, 1992; Barker, Camerlenghi, Acton, et al., 1999; Persico et al., 2003). The paucity of nannofossils in deposits of this age generally reflects cooling associated with the increased thermal isolation of the Southern Ocean around the Antarctic continent consequent to the establishment of the Antarctic Circumpolar Current (e.g., Kennett, 1977).
During Ocean Drilling Program (ODP) Leg 188, three sites were drilled along a shelf-slope-rise transect in Prydz Bay, Antarctica (Fig. F1). The objectives were to (1) date the earliest evidence of glacial activity in Prydz Bay and investigate the Antarctic Paleogene environment; (2) compare paleoceanographic changes reflected in continental rise sediments (Site 1165) to the sediment record of the shelf (1166) and slope (1167), which indicate changes in the East Antarctic Ice Sheet; and (3) study Lambert Glacier-Amery Ice Shelf advance and retreat recorded in upper Miocene and younger trough mouth fan sediments of the Antarctic continental slope.
Calcareous nannofossils were most common, although sporadic, at continental rise Site 1165 (water depth = 3537 m; 64°22´S). Here, a thick Neogene section composed predominantly of fine-grained terrigenous and diatom-bearing hemipelagic sediments (sediment drift deposits) was collected (O'Brien, Cooper, Richter, et al., 2001). In addition to nannofossils, diatoms, radiolarians, and planktonic foraminifers indicate a relatively continuous, nearly 1000-m lower Miocene to upper Pliocene section that underlies a thin Quaternary cover. Data from Site 1165 indicate that at various times during the Neogene and Quaternary conditions near the Antarctic margin were favorable for surface water nannoplankton productivity and subsequent preservation of nannofossils in bottom sediments.