Patrick I. Mclaughlin and Carlton E. Brett
Widespread soft-sediment deformation horizons in Lower Silurian strata of the Appalachian basin: distal signature of orogeny

Keywords
Appalachian foreland basin, far-field tectonics, seismites, sequence stratigraphy, Lower Silurian

Abstract
Sedimentology and stratigraphic mapping of soft-sediment deformed beds (ball and pillow and convolute bedding) in the Lower Silurian of eastern North America demonstrate that these event beds are extremely widespread and that their component sediment layers were not deformed during initial deposition, but slightly later, during shallow burial. Successions of laminated arenaceous beds with interbedded shale in regressive (falling stage) systems tracts of third order depositional sequences appear to have been prone to deformation. Deformed zones are likely the result of shear-induced liquefaction of thixotropic muds and foundering of overlying (carbonate and siliciclastic) silts and sands during very large-scale earthquakes. The distribution of deformed beds, together with increased subsidence, clastic influx, and K-bentonite horizons, provides a meter of intensity and timing of pulses of Silurian orogenesis.

Author info
Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA; pimclau@hotmail.com, carlton.brett@uc.edu

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