Abstract:
Located on the Wilkes Land Margin continental shelf IODP Expedition 318 Site U1358B is positioned offshore a subglacial basin making it an ideal location to study East Antarctic ice sheet (EAIS) dynamics due to the sensitivity of marine-based ice to warmer ocean currents and surface tempteratures. This research investigates dynamics of EAIS during the Pliocene Epoch due to its characteristically warm climates and similar geological configuration of continents to that of present day. Through analysis of composition and provenance of diamicts using heavy mineral, bulk geochemical, and particle size distribution analysis of 23 samples, this investigation will contribute to the knowledge of EAIS behavior in past warm conditions to understand its behavior in future warming climates. Malvern Mastersizer 2000 analyzed grain size distributions and assessed the diamict forming process of the ice sheet. Samples were prepared for fine-grained sediment particle analysis and revealed a fractal distribution indicative of subglacial basal deformation by grain slippage and sediment mixing. Hitachi SEM-EDS determined mineralogical variety present in 18 samples from depths of 0.17 to 28.56 mbsf from Pleistocene, mid-Pliocene and early Pliocene which would determine variations in sediment provenance, identifying minerals by comparing spectra from Reed, 2005 and the use of thin sections, analysis indicated a low-grade metamorphic comosition. Amphibole and pyroxene weight percent of Ca, Mg, and Fe were plotted on ternary plots to determine compositional change between samples. Data were briefly compared with that of the nearby Ross Sea revealing a different mineral assemblage. ICP-OES geochemical data revealed Al:Ti ratios supporting an intermediate to felsic provenance and A-CN-K and A-CNK-FM diagrams revealed an un-weathered provenance with supporting CIA. Current interpretation suggests a grounded ice sheet with an un-weathered Wilkes Land Margin signature composed of low-grade metamorphic basement rocks with felsic properties unaffected by chemical weathering during the Pliocene. Samples from early Pliocene still require further investigation with bulk geochemical and mineral analysis; however, no variations in mineral assemblage between Pleistocene and mid-Pliocene were observed.