November GEOLOGY and GSA TODAY Media ...(proxy for the source of methane accumula...)

Date:11/5/2007

proxy for the source of methane accumulated in the gas hydrate deposits. While iodine ages of as much as 50 million years are found in the landward basin area, those in the seaward ridge area are less than 32 million years old, with significant variation of less than 10 million years. This age contrast reflects methane accumulation from different source formations to an extensive gas hydrate filed; iodine and, by association, methane are derived from old Eocene subducted sediments in the landward region, while those in the seaward region originate preferentially from younger Miocene to Pliocene sediments. Iodine and methane are transported from the depths to the shallow gas hydrate through the active faults constrained by the subduction system.

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'Vertically transferred' overpressures in Brunei: Evidence for a new mechanism for the formation of high-magnitude overpressure
Mark R.P. Tingay et al., University of Adelaide, School of Earth & Environmental Sciences, University of Adelaide, South Australia 5005, Australia. Pages 1023-1026.

Abnormally high fluid pressures (overpressures) are a very common phenomenon in sedimentary basins and are the primary cause of oil-field blowouts, such as the May 2006 East Java mud eruption. Overpressures are generally thought to be observed close to where they are generated. However, Tingay et al. use data from petroleum wells in Brunei to suggest that overpressures can migrate from their source to shallow depths. This new concept of overpressure transfer may explain the presence of anomalous overpressures in many other sedimentary basins worldwide.

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New seismological constraints on growth of continental crust in the Izu-Bonin intra-oceanic arc
Shuichi Kodaira et al., Japan Marine Science and Technology Center, Institute for Frontier Research on Earth Evolution, Yokohama 236-0001 Japan. Pages 1031-1034.

Kodaira et al. present three new constraints on the process of continental c
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Contact: Ann Cairns acairns@geosociety.org 303-357-1056 Geological Society of America Source:Eurekalert

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