Abstract:
The record of Neogene marine stratigraphy and biostratigraphy in the Ross Sea region is based on three series of drillholes: along the southwestern margin of the Victoria Land Basin (DVDP 10, 11; MSST-1; and CIROS 1 and 2); within the Central Trough (DSDP 273); and along the western margin of the Eastern Basin (DSDP 270, 271, and 272). Shipborne geophysical surveys suggest that extensive areas of Neogene strata outcrop at the sea floor or just below a relatively thin Quaternary cover, and within reach of conventional gravity and piston corers. In 1993 and 1994, acoustic data were used to select sites and obtain Neogene sediment cores along a series of transects in the Eastern Basin, using facilities aboard the RVIB "Nathaniel B. Palmer". Forty-seven of the 205 cores collected were selected for study, and 110 samples were taken for detailed studies of Neogene foraminifera. Preliminary data indicates the presence of Miocene, Pliocene and Quaternary assemblages within the sampled sedimentary sequences. Samples from seven of the cores yielded foraminiferal assemblages closely resembling those documented previously in the lower and middle Miocene of DSDP Sites 270 and 272. The success of the shallow sampling procedure is dependent on an ability to establish the in situ assemblages and detect aqueous and grounded ice recycling of relict assemblages into younger sedimentary successions. Where lithofacies geometries and sediment derivation sources may be determined from acoustic data, age clustering in recycled assemblages provides a reconnaissance method for determining basin history, bathymetry, and glacial/deglacial cycle paleoecology. Results indicate that near seafloor sampling procedures provide a potentially useful and rapid reconnaissance technique for dating and tracing discrete Neogene sediment packages over wide areas of the Ross Sea continental shelf, for calibration of acoustic facies and reflectors, and for selecting future shallow and deep drilling targets in Neogene successions.