Monday, 27 August 2007
1.PS-17
Petrographic analyses of lonestones from ODP Drill Sites Leg 188, Prydz Bay, Antarctica
Karel L. Detterman1, Detlef Warnke1, and Carl Richter2. (1) Department of Geological Sciences, California State University, East Bay, 25800 Carlos Bee Blvd., Hayward, CA 94542, (2) Geology, University of Louisiana at Lafayette, 131 Rex St, Madison Hall, Room 236, Lafayette, LA 70503
Summary ODP Leg 188, drilled in 2000, sampled the first advances of the Antarctic ice sheet. Continental shelf Site 1166 documented early glaciation during the Eocene-Oligocene; continental slope Site 1167 documented the Pliocene-Pleistocene debris flow deposition, and continental rise Site 1165 documented the transition of wet- to dry-based glaciers between the lower to upper Miocene. One-hundred and seventeen thin sections were prepared from Site 1166, 1167, and 116 lonestones. The results of this study support a hypothesis proposed in 2001 that as time elapsed, the source area for Site 1167 lonestones shifted from a sandstone to a granitic source. We hypothesize that easily eroded sandstone outcrops were planed off first while ubiquitous gneiss and granite outcrops provided the source material for the younger debris flows at Site 1167 in the Pliocene-Pleistocene. None of the available lonestones suggest sources other than the drainage area of the Lambert Glacier-Amery Ice Shelf complex.