Interpretation of Bivalve Trace Fossils in Fluvial Beds of the Basal Catskill Formation (Late Devonian), Eastern U.S.A

Structures attributed to the upward escape from anastrophic burial of specimens of Archanodon catskillensis (Vanuxem) (Archanodontidae) in the basal sandstone member of the Late Devonian Catskill Formation in northeastern Pennsylvania and equivalent beds in southern New York and northern New Jersey exhibit the following vectorial features: (1) preferential curvature (in vertical section), (2) ellipse parallelism (in bedding plane cross sections), and (3) internal crescent asymmetry (also seen in vertical section). The utility of these vectorial features in the reconstruction of past sedimentary environments depends upon the discovery and understanding of a suitable Holocene analogue Populations of Margaritifera margaritifera (Linné) have been observed from the lower Siletz River, Oregon in both the field and the laboratory. These observations indicate preferential orientation by M. margaritifera in response to unidirectional current flow and ability to burrow quickly upward following anastrophic burial Morphologic features of M. margaritifera point to its capability of producing primary biogenic sedimentary structures similar to those in the Catskill Formation. Comparison with similar though smaller burrows in the British Upper Carboniferous reinforces the interpretation that the Catskill burrows are the product of the upward escape activities of Archanodon catskillensis living in an environment of unidirectional flow regime withrapidly accreting sediments.