Ecological reinterpretation of the dysaerobic Leiorhynchus fauna: Upper Devonian Geneseo Black Shale, Central New York ( USA) .

The anomalous Leiorhynchus brachiopod fauna of the Upper Devonian Geneseo Shale is here reinterpreted as a gregarious and opportunistic epifaunal suspension-feeding assemblage that inhabited dysaerobic environments within the Appalachian Basin. This reinterpretation is based on detailed paleoecology, petrography, x-radiography, SEM, and organic analyses of the upper portion of the Geneseo Shale. Available evidence indicates a reclining mode of life for Leiorhynchus quadracostatus, with the brachial valve oriented up. Abundant Leiorhynchus occur in aggregates or clumps with a mean density of 14/m². The zone of abundant Leiorhynchus also correlates with the highest measured weight percent of organics (6.0%) within the section. The Leiorhynchus are also strongly aligned to a weak current within the basin; mean direction of Leiorhynchus beaks is 42o, mean hinge direction is 122o. The presence of a weak current is also supported by small-scale cross-laminations and small starved ripples in silty layers. - from Authors brachiopod Appalachian Basin paleoecology petrography x radiography Dept of Geology, Syracuse Univ, Syracuse, NY 13244, USA.