HR: 0800h
AN: PP51A-0184    [Abstracts]
TI: Late Pleistocene sediment provenance on the Mendeleev Ridge, Arctic Ocean, from XRF Elemental Analysis and Diffuse Spectral Reflectance measurements
AU: * Ortiz, J D
EM: jortiz@kent.edu
AF: Department of Geology, Kent State University, Kent, OH 44242, United States
AU: Polyak, L
EM: polyak.1@osu.edu
AF: Byrd Polar Research Center, Ohio State Univ., Columbus, OH 43210, United States
AU: Adler, R
EM: adler.66@osu.edu
AF: Byrd Polar Research Center, Ohio State Univ., Columbus, OH 43210, United States
AU: Jakobsson, M
EM: martin.jakobsson@geo.su.se
AF: Department of Geology and Geochemistry, Stockholm University, Stockholm, 106 91, Sweden
AU: Darby, D
EM: ddarby@odu.edu
AF: Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, United States
AB: During the 2005 Healy-Oden Trans-Arctic Expedition (HOTRAX), core HLY0503-JPC08 was raised from the Mendeleev Ridge at the modern junction of the Beaufort Gyre and the Transpolar Drift. This core with sedimentation rates estimated on the order of 2 cm/ka is well situated to sample variations in sedimentation, and thus circulation patterns during the Quaternary. Some characteristic features such as a distinctive change in lithology and prominent IRD layers provide the basis for correlation with previously developed stratigraphies. This overall correlation is confirmed by 1 cm post-cruise diffuse spectral reflectance measurements generated using a Minolta CM-2600d spectrophotometer. Downcore analysis of principle components extracted from the DSR data indicate an inverse correlation between smectite-chlorite which reaches maxima during interglacial/interstadial intervals when sediment Mn is also high, and illite and goethite which reach maxima during glacial intervals when sediment Mn is low. These glacial-interglacial cycles are also evident in elemental composition measured using a handheld, Innov-X Alpha series XRF analyzer which we employ on Arctic sediment for the first time. Estimates of sediment Mn content inferred by diffuse spectral reflectance agree well with XRF based measurements. We observe three distinct end-members based on physical properties and elemental composition. Low density, fine- grained, glacial sediment exhibit low Mn, low Sr, and high Rb values, and thus a high Rb/Sr ratio. Moderately sandy interglacial sediment exhibits high Mn, high Sr, and low Rb values, while sediment from the transitions in to and out of glacial periods are marked by prominent spikes in density, coarse grains, and Zr concentration. Elevated Rb/Sr ratios during glacial periods may result from the re-suspension of fine-grained sediment previously deposited on the outer shelf during higher sea level, and/or by discharge from proglacial lakes. The increase in grain-size accompanied by lows in the Rb/Sr ratio during interglacial/interstadial conditions provides a proxy for fluvial sediment transport and sea-ice rafting from inner shelf environments. Zr spikes mark IRD events corresponding to ice-sheet instabilities. Because the Zr spikes are generally not associated with elevated Ca, a proxy for detrital carbonate, we infer that these spikes represent predominantly iceberg-rafted sediment of Eurasian origin, whereas three distinct Ca maxima indicate prominent iceberg events originating from the Laurentide ice sheet.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4910 Astronomical forcing
DE: 4926 Glacial
DE: 4936 Interglacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting