Abstract

A suite of orange-peel grab sediment samples collected during Deep Freeze II from the Antarctic continental shelf of the Weddell Sea contained several well-sorted sand samples. These were collected in 1957 from Berkner Bank in water depths of 282 to 300 m. Samples from greater and lesser depths show poorer sorting as well as differences in other size parameters (Fig. 1). The well-sorted sands include both striated and fractured quartz grains with a considerable degree of polish.

Photographs and electron micrographs of grain surfaces and replicas suggest that entire grain surfaces of both the fractured surface morphology and the polished surface have undergone quartz dissolution suggesting an extensive period of exposure to seawater. Detailed studies show features characteristic of both beach and dune sand abrasion overlying glacial features.

A variable amount of rock flour is present in all samples, but is least abundant in the 290 ± 10m depth samples. The samples from depths both greater and less than 290 ± 10 m appear to be typical of periglacial marine sediments with a poorly sorted heterogeneous assortment of minerals and rock fragments. The 290 ± 10 m samples appear strikingly different and strongly resemble quartz dune or beach sands. The very good sorting, size, and surface features suggest that these are dune sands.

These data indicate that Berkner Bank may have been exposed at the surface during an interglacial period when the Antarctic land surface stood approximately 300 m higher with respect to sea level than it does today.

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