Abstract

The late Paleocene to early Eocene (ca. 61–56 Ma) was a period of long-term global warming, perhaps the warmest in the Cenozoic. Recent modeling suggests that methane loading of the atmosphere, and related development of polar stratospheric clouds, could have been an important forcing mechanism for this period of warm climate. The Gulf of Alaska accretionary prism contained ∼6 × 106 km3 of siliciclastic sediments deposited in trench and slope settings along Alaska's Maastrichtian and Paleogene continental margin. These sediments underwent complex deformation, accretion, and unusual high heat flow soon after deposition. Accretion processes thermally overmatured the sediments during a time that overlaps the 61–56 Ma period of long-term global warming. Assuming a modest average organic carbon content of 0.3 wt% in these sediments, an estimated 8.35 × 1015 kg of methane were generated in the accretionary prism over an ∼5 m.y. period. This methane was not effectively trapped, and migration pathways to the atmosphere were developed through complexly deformed and emergent continental borderlands. The Gulf of Alaska accretionary prism is a possible source of the atmospheric methane needed to force Paleocene and early Eocene global warming and an example of how tectonic processes can significantly recycle carbon from the geosphere.

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