Trevor Williams1, Kathy Licht
2, Sidney R Hemming
3,4, Gerhard Kuhn
5, Tina van de Flierdt
6, Stefanie A Brachfeld
7, Adi Torfstein
8, James Smith
9, Claus-Dieter Hillenbrand
9, Michael J Flowerdew
10 and Peter Braddock
11, (1)Lamont-Doherty Earth Observ, Palisades, United States, (2)Indiana University Indianapolis, Department of Earth and Environmental Sciences, Indianapolis, United States, (3)Columbia University, Department of Earth and Environmental Sciences, New York, United States, (4)Lamont-Doherty Earth Observatory, Palisades, NY, United States, (5)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research (AWI), Bremerhaven, Germany, (6)Imperial College London, London, United Kingdom, (7)Montclair State University, Earth and Environmental Studies, Montclair, NJ, United States, (8)Hebrew University of Jerusalem, Institute of Earth Sciences, Jerusalem, Israel, (9)British Antarctic Survey, Cambridge, United Kingdom, (10)CASP, Cambridge, United Kingdom, (11)IUPUI, Indianapolis, IN, United States
Contact First Author: Trevor Williams; williams@iodp.tamu.edu
English Abstract:
The geochemical and geochronological fingerprint of rock debris eroded and carried by ice streams may be used to identify the provenance of iceberg-rafted debris (IRD) in the marine sediment record. During deglacial times it has been shown that there is an increase in IRD accumulation in marine sediments underlying the western limb of the Weddell Gyre. We seek to find the provenance of this IRD, identify the ice streams contributing to the IRD load, and interpret the sequence of ice sheet retreat in the Weddell Sea embayment for the last three deglaciations.
In December 2014 we conducted fieldwork to collect samples of rock and sediment debris carried by three of the major ice streams draining the Weddell Sea embayment: the Foundation Ice Stream, the Academy Glacier, and the Recovery Glacier. We sampled both modern moraines at the edges of the ice streams and older till on hillsides next to the ice streams. In addition to rocks representing the geology of local outcrops, we found that each of the three ice streams carries a characteristic set of erratic lithologies from further upstream. The erratics also give clues to the geology hidden under the ice sheet. Over the next year we will characterize the mineralogy, 40Ar/39Ar thermochronology, U-Pb geochronology, Nd isotopic signatures, and Fe-Ti oxide compositions of these tills and erratics. The same measurements will be made on subglacial till and proximal glaciomarine sediment from core sites located at the edge of the Filchner and Ronne Ice Shelves along ice flow lines extending from the ice streams, collected on past expeditions of the RV Polarstern.
We will present initial results from this study in the context of our previous work on IRD and sediment provenance offshore of Antarctica, and discuss the possibilities for using provenance to understand ice stream dynamics over the course of glacial cycles.
