Abrupt chemical weathering increase across the Permian-Triassic boundary

Previous studies have suggested a variety of causes for the end-Permian extinction event including a bolide impact, flood basalt volcanism, methane clathrate dissociation, or some combination of catastrophic processes. One common feature of these hypotheses is the prediction of an enhanced earliest Triassic greenhouse. New high-resolution geochemical results from Graphite Peak, Antarctica support an abrupt increase in chemical weathering in the earliest Triassic among otherwise genetically similar paleosols of similar provenance. Relative to the latest Permian paleosols, the earliest Triassic paleosol exhibits greater leaching, greater accumulation of immobile REEs, and evidence of lower soil pO(2). With no evidence of an erosional unconformity between the paleosols, which are separated by < 15 cm stratigraphically, these results support a rapid shift (perhaps < 10,000 years) to an earliest Triassic greenhouse and a role for methane release in the extinction event and its aftermath. (c) 2005 Elsevier B.V. All rights reserved.