Publication Date:
2010-11-14
Description:
Continental rifting creates narrow ocean basins, where coastal ocean upwelling results in high biological productivity and organic-rich sedimentation. In addition, topographic gradients promote silicate weathering, which consumes atmospheric CO2 (ref. 1). The carbon flux associated with these processes has led to the suggestion that rifting may cool the atmosphere, leading in some cases to glaciation2 and even a snowball Earth scenario3. Guaymas basin, within the Gulf of California, is a young spreading system where new igneous crust is formed beneath a layer of organic-rich sediment that is 1-2 kmthick. Here we present seismic data from Guaymas basin that image recent, basin-wide magmatic intrusions into sediments; sonar backscatter and seafloor photographs that indicate numerous, broadly distributed chemosynthetic seafloor biological communities, and geochemical analyses of water samples suggesting that the methane that supports these communities is derived from magma-driven thermogenic alteration of sediments. Our results suggest that active shallow magmatism releases carbon from sediments up to 50 km away from the plate boundary. This is a much larger area than the less than 5 km found at unsedimented mid-ocean ridges4, and than previously recognized. We conclude that thick sediments may promote broad magmatism, reducing the efficiency of natural carbon sequestration within young sedimented rifts. © 2011 Macmillan Publishers Limited. All rights reserved.
Print ISSN:
1752-0894
Electronic ISSN:
1752-0908
Topics:
Geosciences
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