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Coastal and Marine Geology Program
USGS Woods Hole Science Center

Open-File Report 96-272, Offshore Gas Hydrate Sample Database with an Overview and Preliminary Analysis
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3. Profile of Gas Hydrate Sample Data

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         3.1   Geographic Locations
         3.2    Water Depth and Subseabed Depth
         3.3    Physiographic Provinces and Tectonic Settings
         3.4    Habit or Mode of Occurrence
         3.5    Associated Sediment Textures
         3.6    Thickness of Hydrate Zones and Dimensions of Pure Hydrates
         3.7    Origin: Biogenic vs. Thermogenic

3.3  Physiographic Provinces and Tectonic Settings

The data set includes many types of physiographic provinces. Second order landforms such as continental margins and deep-sea trenches are represented, as are third order forms such as submarine canyons, continental slopes, continental margin ridges and intraslope basins (see Appendix). Three samples were recovered from the axes of trenches. Tectonically, both active (9 occurrences) and passive (6 occurrences) regions are well-represented among the 15 sites. There is a clear association between fault zones and other manifestations of tectonic-related processes, and gas hydrates. [4] About 75% of the hydrate samples were found within or proximal to such features. Fault zones are widespread on margins and may provide preferential pathways for migration of gas-rich fluids. Additionally, vents show that fluids have locally breached the sea floor and deformation by compressional forces may augment the process of gas concentration and thus promote hydrate formation (Hyndman and Davis, 1992)

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