HR: 17:00h
AN: C44A-05    [Abstracts]
TI: Early Pliocene evolution of an overdeepened Antarctic Peninsula continental shelf: onset of modern glacial dynamics
AU: * Bart, P J
EM: pbart@geol.lsu.edu
AF: Louisiana State University Department of Geology and Geophysics, E-235 Howe Russell Complex, Baton Rouge, LA 70803, United States
AU: Iwai, M
EM: iwaim@cc.kochi-u.ac.jp
AF: Kochi University Department of Natural Environmental Science, Akebono-Cho 2-5-1, Kochi, 7808520, Japan
AB: Seismic stratigraphic information and high abundances of Paralia sulcata, a neritic diatom, show that grounding events in the late Miocene occurred on a relatively shallow continental shelf. The absence of P. sulcata and the presence of Stephanopyxis spp., a deeper-water indicator, within the overlying lower Pliocene strata show that the shelf underwent a transition to a deeper continental shelf at ~5.2 Ma. This transition was probably coincident with the evolution of entrenched glacial troughs on the inner shelf. The development of trough mouth fans (TMFs) show that robust ice streams were a major feature of APIS grounding events during the early Pliocene. The cessation of TMF outbuilding corresponds to an upsection percentage increase in the deeper-water species (Stephanopyxis spp.). Diatom biozones suggests that this feature of the modern foredeepened shelf with overdeepened troughs and banks may have only been in existence since ~4.25 Ma. The modern physiography evolved during a relatively brief (~1-Ma) interval of enhanced sub-glacial erosion of the continental shelf. Thus, despite a much earlier onset of glacial conditions on the Antarctic Peninsula, some of the ways that the APIS and the Antarctic continental shelf participates and responds to the current climate system are geologically recent.
DE: 0700 CRYOSPHERE (4540)
DE: 0730 Ice streams
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 3002 Continental shelf and slope processes (4219)
SC: Cryosphere [C]
MN: 2007 Fall Meeting