Tuesday, October 22, 2013

Highlights—Getting to the Permian Source

Many terrestrial deposits record paleoclimate information. In Lower to mid-Permian deposits of the Midcontinent (USA), for example, a marked and long-recognized aridification has been interpreted based on a change more humid facies (e.g., coal, organic shale) of Pennsylvanian strata to widespread redbeds, semi-arid to seasonal paleosols (Calcisols, Vertisols), and evaporites by the mid-Permian. However, the provenance, transport and depositional processes of the voluminous Permian redbeds of the Midcontinent remain largely undefined. This paper by Giles et al. suggests that the facies of the Artinskian (Permian) Wellington Formation in Oklahoma record deposition in ephemeral to perennial lakes during a time of increasing aridity and seasonality, the latter indicated by abundant mudcracks, vertic-type paleosols, conchostracans, and lungfish burrows. The fine and uniform grain size and the geochemistry of the siliciclastic component suggest far-travelled and likely eolian transport that ultimately accumulated in both subaqueous and subaerial environments. Provenance analysis indicates the siliciclastic component was sourced primarily from the southeastern Ouachita–Appalachian orogen and the Ancestral Rocky Mountains or derivative sediment. The results provide additional constraints on atmospheric circulation in this area during late Paleozoic climatic transition.

Lakes, loess, and paleosols in the Permian Wellington Formation of Oklahoma, U.S.A.: implications for paleoclimate and paleogeography of the midcontinent by Jessica M. Giles, Michael J. Soreghan, Kathleen C. Benison, Gerilyn S. Soreghan, and Stephen T. Hasiotis

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