HR: 0800h
AN: OS41C-0490    [Abstracts]
TI: Thermal Measurements Over Hydrate Mounds in Atwater Valley, Gulf of Mexico
AU: * Hagen, R A
EM: rhagen@qur.nrl.navy.mil
AF: Naval Research Laboratory, Marine Physics Branch - Code 7420, Washington, DC 20375 United States
AU: Gardner, J M
EM: gardner@qur.nrl.navy.mil
AF: Naval Research Laboratory, Marine Physics Branch - Code 7420, Washington, DC 20375 United States
AU: Wood, W T
EM: warren.wood@nrlssc.navy.mil
AF: Naval Research Laboratory, Seafloor Sciences Branch - Code 7432, Stennis Space Center, MS 39529 United States
AB: Heat flow measurements and cores were collected in May 2004 across two mound structures in an area designated as the Atwater Valley, a shallow trough near the distal end of the Mississippi Canyon in the northern Gulf of Mexico. The measurements were made along a NW-SE-trending U. S. Geological Survey seismic line that crossed both of the mound structures (mounds D and F). The mounds are thought to result from sediment diapirism caused by dissociation of methane hydrate at depth. A bottom-simulating reflector is visible in the seismic line near the mounds. The data show clear anomalies in sediment temperature and heat flow associated with the mounds. Measurements collected on the top of mound F show sediment temperatures elevated by 0.3$^o$C relative to the surrounding seafloor, and heat flow values of around 160 mW/m$^{2}$. Sediment temperatures decrease away from the summit of the mound, and heat flow values drop to a background level of 40 to 50 mW/m$^{2}$. Sediment temperatures at the summit of Mound D are similar to what was observed at Mound F, and heat flow values are slightly lower at around 132 mW/m$^{2}$, partly as a result of the slightly higher bottom water temperature and thus reduced thermal gradient. These thermal data are modeled to constrain the depth to the gas hydrate layer beneath the mounds and the fluid (and therefore methane) flux from the vent sites.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3094 Instruments and techniques
DE: 3099 General or miscellaneous
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting