NEW MICROPALEONTOLOGICAL DATA FROM THE WISSARD PROJECT, WHILLANS ICE STREAM, ANTARCTICA

The WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) recovered sediments from Subglacial Lake Whillans (SLW) in January, 2013 and the Ross Ice Shelf/Whillans ice stream grounding zone (WGZ) where the West Antarctic Ice Sheet (WAIS) flows into the Ross Ice Shelf, in January, 2015. We report the occurrence of microfossils in these sediments and compare them with sediments recovered earlier from beneath grounded ice at the upstream end of the Whillans Ice Stream (WIS-UpB), and the nearby Kamb (KIS) and Bindschadler ice streams (BIS). Fragmentation patterns in diatoms and sponge spicules in subglacial sediments provide insights into subglacial shearing, and taxonomic analyses provide evidence regarding the ages and provenance of strata being eroded by subglacial processes.

Previous analysis of WIS-UpB, SLW, KIS and BIS, provide background for this research. WIS-UpB shows high amounts of stratigraphic mixing, with a dominance of Upper Miocene diatoms. SLW contains a similar assemblage, with more extensive fragmentation in diatom frustules, indicating longer distance transport and higher cumulative subglacial shear strain. KIS shows a similar upper Miocene age with better preservation and little stratigraphic mixing, which suggests close proximity to source beds and less shear strain. BIS differs from the other ice streams in the region with a dominant Paleogene age of its fossils, suggesting local erosion of older strata.

These microfossils provide evidence of WAIS history and ice stream processes. With new data from WGZ sediments we will present absolute abundance counts (particles per gram) of identifiable diatoms and of diatom fragments, as well as diatom assemblage analysis, which provides biostratigraphic evidence of sediment mixing in this new field site. These studies contribute to an understanding of subglacial processes, including sediment flux, and WAIS history.