Ice shelf drill sites proposed to study Pre-Late Oligocene climate and tectonic history, Coulman High, Southwestern Ross Sea, Antarctica.
Abstract
New geophysical data were collected in front of the Ross Ice Shelf using the RVIB Nathaniel B. Palmer in January of 2003. The primary goal was to collect detailed grids of seismic data to select drill sites to investigate the climate and tectonic history of the Ross Sea region. The survey sites were located where large sections of the ice shelf have broken off, exposing previously inaccessible seafloor. A site survey at the C-19 iceberg calving site, located in 800-900 m of water adjacent to Ross Island and 120 km NE from McMurdo Station, was conducted under the premise that the ice sheet, advancing north at ~1 km/year, will in time cover the survey thereby allowing drilling into the seabed from the ice sheet. We propose an E-W transect of drill sites along the ice shelf front designed to target section where pre-Late Oligocene strata dips east allowing successively deeper stratigraphic sampling with a series of holes across strike. Cores from here may record the transition from warm climate in Eocene time to the cooler Oligocene and will test our hypothesis that extension between East and West Antarctica is recorded in sediments in this sector of the Ross Sea. Rifting in Cretaceous time resulted in widespread extension of the Ross Sea amounting to several hundred kilometers. Adare Trough seafloor spreading in Eocene-Oligocene time adjacent to the Ross Sea continental shelf resulted in about 180 km of spreading, and may project into the western Ross Sea. Syn-rift sediments of these ages may be present. The C-19 site on Coulman High is characterized by N-S trending basement half grabens filled with syn-rift sediments of unknown age truncated by an angular unconformity, and overlain by undeformed Late Oligocene and younger strata that we correlated to DSDP and Cape Roberts drill sites. We have divided the pre-Oligocene units into an upper (Early Oligocene?-Eocene?; ~ 680-1000 m below sea floor (bsf)) unit and lower (Eocene?-Late Cretaceous?; >1000 m bsf) unit, separated by an unconformity, all resting on top of acoustic basement at ~1400m bsf. We suggest that the pre-Oligocene strata are syn-rift units deposited and deformed during both Late Cretaceous and Early Eocene extension.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFM.T11A1244D
- Keywords:
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- 1744 Tectonophysics