HR: 0800h
AN: PP11A-0231    [Abstracts]
TI: Composition of Eocene Ice-Rafted Debris, Central Arctic Ocean
AU: * Ramstad, C
EM: ramstacp@jmu.edu
AF: James Madison University, Department of Geology and Environmental Science, MSC 6903, Harrisonburg, VA 22807, United States
AU: St. John, K
EM: stjohnke@jmu.edu
AF: James Madison University, Department of Geology and Environmental Science, MSC 6903, Harrisonburg, VA 22807, United States
AB: IODP Expedition 302 drilled a 400-m sediment record which contains physical evidence of ice-rafting in the Eocene and Neogene in the Arctic (Backman et al., 2006; Moran et al., 2006, St. John, in press). An increase in the terrigenous sand abundance occurs above 246 mcd (~46 Ma), with a flux similar to that in the Neogene. Higher resolution sampling in an interval of good recovery from 246-236 mcd shows evidence of cyclic input of IRD and biogenic components that fits with Milankovitch forcing at the obliquity period (Sangiorgi et al., in press). The question remains – what areas of the Arctic were ice-covered at this early stage in the Cenozoic? To address this provenance issue the composition of the terrigenous sands (250 micron fraction) in cores 55-56X is being quantified. Grains in 75 samples are being point-counted and their compositions categorized. Quartz grains are the dominant component (greater than 10,000 grains per gram), with some being hematite-stained, and there are lesser amounts of mafic minerals. No carbonate grains are identified so far in this study. Possible sources areas for Eocene IRD are the Eastern European and Russian Arctic margins. Tracking compositional variations of the IRD over the interval of cyclic deposition, should indicate whether the cyclic IRD deposition was consistently derived from one source region or multiple regions during this time.
DE: 0732 Icebergs
DE: 3022 Marine sediments: processes and transport
DE: 3036 Ocean drilling
DE: 9315 Arctic region (0718, 4207)
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting