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Hamilton College, Clinton, New York 13323, USA
Although laminites from the continental slope and rise are known from a number of regions in Antarctica, laminated muds on the continental shelf have not been widely recognized. During USAP-88 cruise III of the RV Polar Duke, a number of piston cores were collected from bays and fjords along the Danco Coast of the Antarctic Peninsula. A fine-grained sedimentary sequence of thin-bedded to randomly laminated mud and sand with dropstones is underlain by a rhythmically laminated sequence of silt and clay. The deposits were collected within a submarine valley (450 m deep) which appears to extend beneath the terminus of a tidewater glacier (Cayley Glacier). The glacial regime of the area today is polar to sub-polar with restricted ice surface melting. Fine-scale horizontal layers are observed in the water column and these transport fine-grained sediment at mid-water depths. Such features are not related to surface meltwater processes, but may be caused by tidal pumping of the basal cavity. The random bedding thickness of the sediments is related to the present depositional environment which includes iceberg rafting, bioturbation, pelagic settling of biogenic detritus, and sediment gravity flows. The rhythmic units likely represent subglacial marine deposition within the valley; possibly under the influence of tidal processes.
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