HR: 09:45h
AN: OS31D-07    [Abstracts]
TI: An Electromagnetic Survey of the JIP Drill Sites in Atwater Valley
AU: Ellis, M
EM: mhe1@noc.soton.ac.uk
AF: School of Ocean and Earth Science, National Oceanography Center, University of Southampton, Euopean Way, Southampton, S014 3ZH United Kingdom
AU: * Evans, R L
EM: revans@whoi.edu
AF: Dept of Geology and Geophysics, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543
AU: Hutchinson, D
EM: dhutchinson@usgs.gov
AF: USGS, 384 Woods Hole Rd, Woods Hole, MA 02543
AU: Hart, P
EM: hart@usgs.gov
AF: USGS, 345 Middlefield Rd, Menlo Park, CA 94019
AB: A seafloor electromagnetic (EM) survey was conducted across the Atwater Valley sites of JIP drilling, in 1300m water depth. The towed EM system used for the survey was pulled along the seafloor and measured electrical conductivity profiles to a sub-bottom depth of 20~m along ~17~km of tow line. The survey included data across 2 mounds, both of which have a relief of around 10~m and are thought to contain gas hydrate. The EM data collected are used to map the physical properties of the sediments in the area, and respond to changes in porosity, temperature and pore-water salinity. Hydrate bearing sediment is expected to reduce bulk electrical conductivity. Contrary to expectations, the EM data showed raised electrical conductivity across both mounds compared to the surrounding area. This response is indicative of raised temperatures and/or raised chlorinity in the subsurface, a result which is confirmed by JIP drilling and other data from the mounds.
DE: 3004 Gas and hydrate systems
DE: 3006 Marine electromagnetics
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005