HR: 14:55h
AN: PP53C-06    [Abstracts]
TI: Evidence of Active Warm Based Neogene Glaciation in the Transantarctic Mountains
AU: * Roof, S R
EM: sroof@hampshire.edu
AF: School of Natural Science, Hampshire College , Amherst, MA 01002-3359 United States
AU: Ashworth, A C
EM: allan.ashworth@ndsu.nodak.edu
AF: Department of Geosciences, North Dakota State University, Fargo, ND 58105-5517 United States
AU: Cantrill, D J
EM: David.Cantrill@nrm.se
AF: Department of Palaeobotany, Swedish Museum of Natural History, Stockholm, SE-104 05 Sweden
AU: Francis, J E
EM: j.francis@earth.leeds.ac.uk
AF: School of Earth Sciences, University of Leeds, Leeds, LS2 9JT United Kingdom
AB: Interbedded diamictites, conglomerates, sandstones, and siltstones in the Meyer Desert Formation of the Transantarctic Mountains record a dynamic history of warm-based glacier advances and retreats during Neogene time. The Oliver Bluffs (85\deg 80'S, 166\deg 83'E) consist of near-vertical bluffs up to 85 m high that extend for 2 km along the flank of the Beardmore Glacier and reveal at least four diamictites separated by stratified sands and gravels. Bedding dips gently to the northwest ($<$ 5\deg ) and appears to continue under the Meyer Desert Plateau to the southeast. The lower three diamictites consist of light gray to bluish gray fine matrix and boulder clasts up to 5 m diameter. The uppermost diamictites are distinctly bluish-gray in color, contain smaller boulder clasts (0.5 m diameter), and contain previously identified soil horizons. The diamictite beds, which are up to 30 m thick, are interpreted as lodgment tills based on degree of compaction, internal glaciotectonic deformation, and medium to strong pebble fabrics, although a few thin diamictite beds may be of melt-out till or debris flow origin. Diamictites are laterally continuous over tens to hundreds of meters and the lower contacts often truncate underlying beds. Water-worked sediments include laminated silt and sand beds, cross-bedded sands and gravels, and boulder lag deposits. Several finely laminated lacustrine deposits testify to the existence of small lakes or ponds between glacial advances. Wood and leaf imprint fossils, including {\it in situ} rooting systems of {\it Nothofagus} shrubs and cushion plants, further demonstrate the presence of a wet landscape during interglacial intervals. Taken together, this facies sequence is interpreted to represent at least four warm-based glacial advances with a spatially-variable vegetated terrestrial outwash environment superimposed on a landscape with relief inherited from each previous glacial advance. This contrasts markedly with the polar desert landscape of the present day. Research supported by NSF grant OPP 0230696.
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting