HR: 1330h
AN: PP12A-0221    [PDF]
TI: Organic Matter Isotopic Analyses from Chukchi Sea Sediments: New Constraints on the Late Quaternary Sea Level History of Beringia
AU: * Lundeen, Z
EM: zlundeen@geo.umass.edu
AF: University of Massachusetts-Amherst, Department of Geosciences, Amherst, MA 01003 United States
AU: Brigham-Grette, J
EM: juliebg@geo.umass.edu
AF: University of Massachusetts-Amherst, Department of Geosciences, Amherst, MA 01003 United States
AU: Driscoll, N
EM: ndriscoll@ucsd.edu
AF: Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA 92093 United States
AU: Keigwin, L
EM: lkeigwin@whoi.edu
AF: Woods Hole Oceanographic Institution, 360 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Burns, S
EM: sburns@geo.umass.edu
AF: University of Massachusetts-Amherst, Department of Geosciences, Amherst, MA 01003 United States
AU: Petsch, S
EM: spetsch@geo.umass.edu
AF: University of Massachusetts-Amherst, Department of Geosciences, Amherst, MA 01003 United States
AB: Accurately defining the sea level history of Beringia since the Last Glacial Maximum has important implications for understanding local paleoclimate data, paleoceanography of the Arctic Basin, and the timing of human migration from Asia into North America. However, few constraints exist on the timing of post-glacial sea level transgression across the former land bridge. To address this data gap, a new investigation into the sea level history of Beringia and its effects on regional paleoclimate and paleoceanography was launched in the summer of 2002 during a cruise on the USCGC Healy in the Bering and Chukchi Seas. A transect of cores were collected across the continental shelf to record the flooding history associated with glacial termination after the LGM. Cores from $>$ 60m modern water depth lack lithologic changes expected from a marine transgressive sequence. Instead, these sediments consist primarily of clay and silt, with only minor amounts of coarser material, reflecting offshore marine burial. However, abrupt changes in downcore density suggest that disconformities may exist, with Holocene and Late-Glacial muds overlying older marine clays from an earlier sea level high-stand. To confirm this possibility, three cores were selected for elemental and isotopic analysis of bulk sedimentary organic matter. Downcore variations in $\delta ^{13}$C, $\delta ^{15}$N, TOC, and C/N are being used to determine the relative contributions of marine and terrigenous organic matter to the sediments. These geochemical data are useful as indicators of proximity to shoreline, riverine organic matter delivery and diagenetic alteration. Together with radiocarbon ages from fossil mollusks, these data place minimum limiting ages on the post-glacial transgression at multiple water depths on the Chukchi Shelf.
DE: 1040 Isotopic composition/chemistry
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting