Abstract

Distinctive sedimentary structures, textures, and extremely negative δ13Ccarb values from the Ediacaran Doushantuo cap carbonate (ca. 635 Ma) in south China were taken as evidence for a methane hydrate destabilization event, but existing data for a methane-derived δ13Ccarb signature were reported from a single locality in the Yangtze Gorges area. Here we report negative δ13Ccarb values as low as −48‰ (Vienna Peedee belemnite) from two additional sections ~6 km and 55 km from the original locality. These negative δ13Ccarb values were obtained from isopachous cements that fill stromatactis-like cavities, sheet cracks, and fractures, and from partially recrystallized carbonate crusts, consistent with carbonate precipitation at cold methane seeps. The new data support a widespread methane release event following the Nantuo glaciation in south China (ca. 635 Ma), which may have contributed to the origin of unusual sedimentary and isotope features of cap carbonates.

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