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Glacial recession from the Antarctic continental shelf is recorded by glacial-marine diamictons, sands, and overlying siliceous oozes. In order to clarify the chronology for this sequence, use was made of the University of Arizona tandem accelerator mass-spectrometer (TAMS) for 14C dating. Small samples of benthic and planktonic foraminifera were selectively removed from diamictons, graded sands, and surface sediments which were recovered from the Wilkes Land continental shelf and slope, East Antarctica. Organic carbon was also utilized as a source for TAMS dating of the siliceous oozes and muds. Uncorrected ages varied from 14,260 ± 140 to 3230 ± 200 yr B.P. Carbon fixed by phytoplankton and foraminifera is strongly influenced by old, glacial-derived CO2. Thus, reservoir corrections of up to 5500 yr are needed for the 14C dates. Iceberg turbation reworks foraminifera so that dates from resulting deposits (diamictons) are interpreted as maximum ages. The consistency of corrected ages from the shelf, along with the sedimentologic interpretation, suggests a rather recent recession, perhaps mid-Holocene for this portion of the East Antarctic ice sheet. Further application of the TAMS method should help clarify other problems concerning the late Quaternary glacial history of Antarctica.

As part of a program to investigate modem processes of sedimentation along the Antarctic Peninsula, several glaciated fjords were examined with respect to their physical oceanographic and bottom sediment characteristics. Measurements in the ice proximal (less than 1 km) environment of three fjords show unique characteristics of salinity, temperature, and light transmissivity versus depth. Fine-scale layering (5 to 25 m thick) occurs as relatively cold and turbid water alternates with relatively warm and clear water. The cold, turbid waters are neutrally buoyant, with respect to the ambient water, and are best developed close to glacier termini, at depths of between 100 and 400 m. The data are interpreted as an indication of horizontally flattened tongues or plumes which are generated by tidal-driven circulation, cooling, and ice melting within subglacial marine cavities. Tidal flushing of near-surface crevasses also adds to the complexity of circulation. Significant quantities of suspended sediment (concentrations of up to 7 mg/l) are transported by the horizontal layers into open bays or outer reaches of the fjord system. This represents a new mechanism for the transport of sediment within fjord environments, one which may be characteristic of polar settings. INTRODUCTION Antarctic fjord environments are critical settings with respect to prospects for future development of the Antarctic landmass, yet little is known concerning characteristics of circulation and sedimentation in these heavily glaciated embayments. Because of this, the potential impact of marine pollutants and contamination are difficult to assess. Most studies on fjords recognize the importance of estuarine-type circulation which is driven by fluvial discharge and/or glacial meltwater at the fjord head [Syvitski, 1989]. In these settings, surface outflows of low-salin,:ty, turbid water are important for the dispersal of suspended sediment and, thus, exert a strong control upon resulting facies patterns and the fate of contaminants [Syvitski et al., 1987]. In the absence of significant meltwater input, particularly that which is derived by surface heating and precipitation, other processes could be expected to dominate. However, observaaNow at Department of Geophysics, Stanford University, Stanford, California 94305. tions of such processes are limited by the seasonal bias of field studies and by the traditional emphasis upon deepwater and shelf oceanography in the Antarctic [Jacobs, 1989]. Theoretical considerations, laboratory observations, and limited field observations suggest that winddriven currents, diffusive convection, and tidal pumping may be important aspects of ice proximal circulation within polar fjords (van Heijst [1987], Horne [1985],Josberger and Martin [1981J, Jacobs et al. [1981], MacAyeaf[1985], and others). However, the relative importance of these mechanisms and their role in sediment transport has not been addressed. The results presented in this paper represent some of the first observations made on water characteristics wi...

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