Collaborative Research: Development of a Suite of Proxies to Detect Past Collapse of the West Antarctic Ice Sheet
Development of a Suite of Proxies to Detect Past Collapse of the West Antarctic Ice Sheet
This project developed sediment provenance proxies to trace the sources of sediment discharged by the WAIS to the continental rise. The WAIS erodes sediments from various West Antarctic geologic terranes that are deposited in adjacent drift sites. The geochemistry and magnetic properties of drift sediments reflect the tectono-metamorphic history of their source terranes. Deglaciation of a terrane during WAIS collapse should be detectable by the loss of the terrane’s geochemical and magnetic signature in continental-rise detrital sediments. Continental shelf late-Holocene sediments from near the current WAIS groundling line were analyzed for silt- and claysize Sr-Nd-Pb isotopes and major-trace elements. The suite of cores spans from the eastern Ross Sea to the northern tip of the Antarctic Peninsula and established the provenance signatures of the Ross and Amundsen Provinces of Marie Byrd Land, Pine Island Bay, Thurston Island/Eight Coast Block, Ellsworth-Whitmore Crustal Block, and Antarctic Peninsula terranes. Many of these terranes have similar tectono-metamorphic histories but Sr-Nd isotope data from detrital sediments suggest at least 3 distinct provenance signatures. This comprehensive grain-size-specific provenance data adds to on-going collection of glacial till mineral and bulk provenance data. An initial down core study of Ocean Drilling Program Site 1096 in the Bellingshausen Sea was used to assess the utility of these new grain-size-specific provenance proxies in documenting WAIS collapse. We found the presence of both the WAIS and APIS over the last 115,000 years, but absence of the WAIS before 115,000 years ago. This means that the WAIS was gone during the last interglacial period, an interval when sea level was at least 6 meters above present.
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