Dynamics of the late Plio-Pleistocene West Antarctic Ice She

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TitleDynamics of the late Plio-Pleistocene West Antarctic Ice Sheet documented in subglacial diamictites, AND-1B drill coreAbstractGeologic studies of sediment deposited by glaciers can provide crucial insights into the subglacial environment. We studied muddy diamictites in the ANtarctic geological DRILLing (ANDRILL) AND-1B drill core, acquired from beneath the Ross Ice Shelf in McMurdo Sound, with the aim of identifying paleo-ice stream activity in the Plio-Pleistocene. Glacial advances were identified from glacial surfaces of erosion (GSEs) and subglacial diamictites within three complete sequences were investigated using lithofacies associations, micromorphology, and quartz sand grain microtextures. Whereas conditions in the Late Pliocene resemble the modern Greenland Ice Sheet where fast flowing glaciers lubricated by surface meltwater terminate directly in the sea (interval 201-212. mbsl) conditions in the Late Pleistocene are similar to modern West Antarctic Ice Sheet (WAIS) ice streams (38-49. mbsl). We identify the latter from ductile deformation and high pore-water pressure, which resulted in pervasive rotation and formation of till pellets and low relief, rounded sand grains dominated by abrasion. In the transitional period during the Mid-Pleistocene (55-68. mbsf), a slow moving inland ice sheet deposited tills with brittle deformation, producing lineations and bi-masepic and unistrial plasma fabric, along with high relief, conchoidally fractured quartz grains. Changes in the provenance of gravel to cobble-size clasts support a distant source area of Byrd Glacier for fast-flowing paleo-ice streams and a proximal area between Darwin and Skelton Glaciers for the slow-moving inland ice sheet. This difference in till provenance documents a shift in direction of glacial flow at the core site, which indirectly reflects changes in the size and thickness of the WAIS. Hence, we found that fast ice streaming motion is a consequence of a thicker WAIS pushing flow lines to the west and introducing clasts from the Byrd Glacier source area to the drill site. The detailed analysis of diamictites in AND-1B demonstrates that Pliocene glacial intervals were warmer than in the Pleistocene when polar ice sheets grew from local inland ice to regional ice streams. â"' 2014 Elsevier B.V.AcknowledgementsThe ANDRILL project is a multinational collaboration among the Antarctic programs of Germany, Italy, New Zealand (AntNZ), and the United States. Scientific studies are jointly supported by the U.S. National Science Foundation, the New Zealand Foundation for Research, the Royal Society of New Zealand Marsden Fund, the Italian Antarctic Research Program, the German Science Foundation, and the Alfred-Wegener Institute for Polar and Marine Research. We wish to acknowledge the contributions of the on-ice MIS core description team, as well as Matt Ake, who collected the SEM photomicrographs at Appalachian State University. We appreciate the comments of two anonymous reviewers.

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1st AuthorCowan, E.AuthorCowan, E.Christoffersen, P.Powell, R.Talarico, F.Year2014JournalGlobal and Planetary ChangeVolume119Pages56-70DOI10.1016/j.gloplacha.2014.05.011URLhttps://www.scopus.com/inward/recor.....0a93a74643977e18e30513838KeywordsCore drillingDeformationGlaciersMorphologyQuartzSalinity measurementSea ice, Deformable bedIce streamsMicromorphologiesPleistoceneRoss SeaSubglacial till, Glacial geology, erosiongeomorphologyglacial environmentice thicknesslithofaciesmeltwaterPliocene-Pleistocene boundaryporewater, Antarctic Ice SheetAntarcticaArcticByrd GlacierEast AntarcticaGreenlandGreenland Ice SheetRoss SeaSouthern OceanWest Antarctic Ice SheetWest Antarctica, rank5Author KeywordsDeformable bedIce streamMicromorphologyPleistoceneRoss SeaSubglacial till

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TypeArticleCitationCowan, E., Christoffersen, P., Powell, R. and Talarico, F. (2014). Dynamics of the late Plio-Pleistocene West Antarctic Ice Sheet documented in subglacial diamictites, AND-1B drill core. Global and Planetary Change, 119: 56-70 IdentifierCowan2014Relevancerank5