HR: 08:40h
AN: OS41C-03 INVITED     [Abstracts]
TI: Tectonic Discrimination with Classification Trees
AU: * Riedel, M
EM: mriedel@NRCan.gc.ca
AF: Natural Resources Canada, Geological Survey of Canada - Pacific, 9860 West Saanich Road, Sidney, BC V8L 4B2 Canada
AU: Collett, T S
EM: tcollett@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center Box 25046, MS-939, Denver, CO 80225 United States
AU: Malone, M
EM: malone@iodp.tamu.edu
AF: Integrated Ocean Drilling Program, Texas A&M University, College Station, TX 77845 United States
AB: This presentation will report on the initial results of an Integrated Ocean Drilling Program (IODP) expedition to study the occurrence of gas hydrates along the Cascadia continental margin of North America. The abstract has been prepared in advance of the cruise and describes the primary objectives of this effort. IODP Expedition 311 (scheduled September 14 to October 29, 2005) has been designed to further constrain models for the formation of marine gas hydrate in subduction zone accretionary prisms. The objectives include characterizing the deep origin of the methane, its upward transport, its incorporation in gas hydrate, and its subsequent loss to the seafloor. The main attention of this expedition is on the widespread seafloor-parallel layer of dispersed gas hydrate located just above the base of the predicted stability field. In a gas hydrate formation model, methane is carried upward through regional sediment or small-scale fracture permeability, driven by the tectonic consolidation of the accretionary prism. The upward-moving methane is incorporated into the gas hydrate clathrate as it enters the methane hydrate stability zone. Also important is the focusing of a portion of the upward methane flux into localized plumes or channels to form concentrations of near-seafloor gas hydrate. The amount of gas hydrate in local concentrations near the seafloor is especially important for understanding the response of marine gas hydrate to climate change. The expedition includes coring and downhole measurements at a transect of five sites across the Northern Cascadia accretionary prism. The sites will track the history of methane in an accretionary prism from (1) its production by mainly microbiological processes over a thick sediment vertical extent, (2) its upward transport through regional or locally focused fluid flow, (3) its incorporation in the regional hydrate layer above the bottom-simulating reflector (BSR) or in local concentrations at or near the seafloor, (4) methane loss from the hydrate by upward diffusion, and (5) methane oxidation and incorporation in seafloor carbonate, or expulsion to the ocean.
UR: http://iodp.tamu.edu/scienceops/expeditions/exp311.html
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 3004 Gas and hydrate systems
DE: 3022 Marine sediments: processes and transport
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005