Preliminary analysis of the Baranof Fan system, Gulf of Alaska, based on 2D seismic reflection and multibeam bathymetry data
Abstract
The Baranof Fan is a large marine sedimentary system in the eastern Gulf of Alaska, straddling the border between the U.S. and Canada. The volume of the Fan is estimated to be > 200,000 km3. Little is known about the depositional timing, the tectonic and morphologic processes influencing its development, or the role of channel aggradation and avulsion in its progression. Both tectonic and climatic transitions likely influenced the formation and evolution of the Fan, with events including the onset of northern hemisphere glaciation, the Mid-Pleistocene transition, the transport of the Yakutat Terrane along the southeast Alaskan margin, and the uplift of the Coast Mountains. 2D seismic reflection and multibeam bathymetry data were collected in the Gulf of Alaska in June 2011 aboard the R/V Marcus G. Langseth as a part of the U.S. Extended Continental Shelf (ECS) program assessing potential opportunities under the United Nations Law of the Sea Convention. The purpose of the 2011 survey was to determine sediment thickness, velocity structure, stratigraphic architecture, and crustal structure on of the Gulf of Alaska seafloor in support of U.S. continental shelf maritime zone definition. The surveyed geologic features include the Surveyor and Baranof sedimentary systems, which control active sediment distribution in the Gulf of Alaska. Preliminary analysis of these data show four distinct buried channels throughout the mid to distal Baranof Fan, ranging in width from 5 - 9 km, which may have evolved into modern surface channels (ranging in width from 2 - 7 km) visible in both the seismic data and multibeam bathymetry. The location and trajectory of these buried channels, however, appears distinct from the modern Horizon and Mukluk Channels; the buried channels may have avulsed into the modern channel systems, or could possibly be older and now abandoned branches instrumental in building the westward part of the Fan. All of the imaged channels appear to be depositional, and consistently have thicker levees on their western banks, possibly due to effects of the Alaska Gyre at depth and/or the Coriolis. Preliminary velocity analysis from sonobuoy refraction data indicates that the thalwegs of buried channels do not exceed an 800 m depth within the 2 km thick Fan; we will seek to map a prominent reflector located beneath these channels from the Baranof system into the Surveyor system. New age dates from ashes sampled at DSDP Site 178 within the Surveyor Fan may thus provide constraints on the timing of deposition of the western Baranof Fan.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T33A2372L
- Keywords:
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- 3022 MARINE GEOLOGY AND GEOPHYSICS / Marine sediments: processes and transport