Continental slope records indicate a grounded ice sheet margin during past glacials, South Shetland Trench, Antarctica

• Main Authors: Stewart, Heather, Jamieson, Alan, O Cofaigh, Colm, Stewart, Margaret, Bradwell, Tom
• Format: Text
• Language: English
• Published: 2016
• Subjects: Earth Sciences; Glaciology; Marine Sciences; Antarctic; The Antarctic; Barents Sea; Antarctic Peninsula; Ross Sea; South Shetland Islands; Bransfield Strait; Canada; South Orkney Islands; Elephant Island; South Shetland Trench; Antarc*; Antarctica; Ice Sheet
• Online Access: http://nora.nerc.ac.uk/id/eprint/515528/; https://nora.nerc.ac.uk/id/eprint/515528/1/GlaciatedMargins_SST_HASTPoster_FINAL.pdf; http://www.geolsoc.org.uk/wsmith16

The South Shetland Trench (SST) is located around 100 km northwest, and parallel to, the South Shetland Islands, located between the Antarctic Peninsula and South America. Although a number of studies examining glacial history have been undertaken in the Bransfield Strait located between the South Shetland Islands and the Antarctic Peninsula to the south, the authors believe this is the first study of the seafloor glacial geomorphology, and recent glacial history of the SST. This paper presents the results from a Eurofleets2 expedition to the SST that took place in December 2015. There is evidence from other sub-Antarctic islands such as the South Orkney Islands and Elephant Island for glaciations that extended well onto their continental shelves although a lack of age constraint from marine cores means it cannot be tied to a specific glaciation. Multibeam echosounder data reveal the study area on the southern flank of the South Shetland Trench to host a system of linear downslope gullies and glacigenic debris flows. Downslope gullies have been observed on other glaciated margins such as the Scotian slope offshore Canada, Ross Sea Antarctica, north-western Barents Sea and West Shetland Margin offshore north-western UK. The gullies are inferred as being eroded by turbidity currents comprising cold, dense, sediment-rich meltwater released from an ice front located at or near the continental shelf break. Glacigenic debris flows are found to extend from the continental shelf break to the lower continental slope. Sub-bottom profiler data penetrated up to 150ms below seafloor in places and reveal a stacked sequence of debris flows suggestive of a fluctuating ice front that was grounded to, and retreated from, the shelf break on several occasions. The trench floor appears to be devoid of major geomorphological features as revealed by the multibeam echosounder data and comprise a relatively well layered sequence imaged by the sub-bottom profiler. In addition 3 gravity cores up to 2.79 m in length and one core catcher ...