Paleoenvironmental and tectonic implications of an Upper Devonian glaciogenic succession from east-central West Virginia, USA

Abstract

ABSTRACT Glaciogenic rocks are rare in the Appalachian area and occur only locally as parts of Upper Precambrian and Upper Devonian successions. This trip examines a relatively recent exposure of Upper Devonian glaciogenic diamictites and laminites along Corridor H (U.S. Highway 48) in east-central West Virginia, USA. The diamictites occur in the Rockwell Member of the Price Formation, in transition with the underlying redbeds of the Upper Devonian Hampshire Formation. Palynology indicates that all parts of the Rockwell Member exposed at the locality are present in the Retispora lepidophyta – Verrucosisporites nitidus (LN) Miospore Biozone and are, therefore, of Late Devonian, but not latest Devonian, age. This biozone occurrence indicates correlation with parts of the Oswayo Member of the Price Formation, the Finzel tongue of the Rockwell Formation, and with dropstone-bearing parts of the Cleveland Shale Member of the Ohio Shale in northeastern Kentucky. Much previous work supports a glaciogenic origin for the diamictites and associated sediments, which occur as parts of a shallow-marine incursion that ended the Hampshire/Catskill alluvial-plain/deltaic complex across much of the Central Appalachian area. The glaciogenic succession is part of nearshore, marginal-marine strata that accumulated in an embayment during the Cleveland-Oswayo-Finzel transgression, which represents a global eustatic sea-level rise and foreland subsidence related to Acadian/Neoacadian deformational loading in the adjacent orogen. Detrital-zircon-provenance data from the diamictites indicate Ordovician plutonic sources as well as reworked Neoproterozoic to Ordovician sedimentary sources that can only have been derived from nearby Inner Piedmont sources like the Potomac terrane. This provenance suggests that Acadian/Neoacadian convergence of the exotic Carolina terrane with the New York and Virginia promontories along the southeastern margin of Laurussia not only uplifted Inner Piedmont source areas into a high mountain range capable of supporting glaciation in a subtropical setting, but also, through deformational loading, enhanced regional subsidence and the incursion of shallow seas that allowed alpine glaciers access to the open sea.