ABSTRACT A 3 ton (2.7 metric tonnes [t]), granitoid lonestone with Appalachian provenance was found in situ in offshore Devonian black shale in northeastern Kentucky, United States, and is denoted herein as the Robinson boulder, or lonestone, after its discoverer, Michael J. Robinson. This large boulder appears to have been displaced nearly 500 km from its source on the opposite margin of the Acadian/Neoacadian Appalachian foreland basin. While previous identifications of possible lonestones have been attributed to Pleistocene glacial events, scrutiny of this lonestone’s origin suggests that the boulder, which was embedded in the Upper Devonian Cleveland Shale Member of the Ohio Shale in northeastern Kentucky, is most likely a Devonian ice-rafted glacial dropstone. Notably, palynologic correlation with reported glacial diamictites elsewhere in the basin indicates such a source. Together, the dropstone and diamictites, separated by ~500 km, provide evidence for alpine glaciation in the ancient Acadian/Neoacadian orogen and for tidewater glaciers in the adjacent, eastern margin of the foreland basin. The latest Devonian marine transgression and Neoacadian foreland subsidence are interpreted to have been associated with tidewater glacial connections to the open sea. Importantly, the existence of this dropstone and its likely glacial precursor events require new considerations about contemporary black-shale sedimentation and the influence of tectonics on the delivery of glacial sediments to foreland basins.

ABSTRACT This trip explores three different occurrences of a diamictite-bearing unit in the transition between Upper Devonian redbeds of the Hampshire Formation (alluvial and fluvial deposits) and Mississippian sandstones and mudstones of the Price/Pocono Formations (deltaic deposits). Palynology indicates that all the diamictites examined are in the LE and LN miospore biozones, and are therefore of Late Devonian, but not latest Devonian, age. Their occurrence in these biozones indicates correlation with the Cleveland Member of the Ohio Shale, Oswayo Member of the Price Formation, and Finzel tongue of the Rockwell Formation in the central Appalachian Basin and with a large dropstone (the Robinson boulder) in the Cleveland Member of the Ohio Shale in northeastern Kentucky. Although several lines of evidence already support a glaciogenic origin for the diamictites, the coeval occurrence of the dropstone in open-marine strata provides even more convincing evidence of a glacial origin. The diamictites are all coeval and occur as parts of a shallow-marine incursion that ended Hampshire/Catskill alluvial-plain accumulation in most areas; however, at least locally, alluvial redbed accumulation continued after diamictite deposition ended. The diamictites are parts of nearshore, marginal-marine strata that accumulated during the Cleveland-Oswayo-Finzel transgression, which is related to global eustasy and to foreland deformational loading during the late Acadian orogeny. Detrital zircon data from clasts in a diamictite at Stop 3 (Bismarck, West Virginia) indicate likely Inner Piedmont, Ordovician plutonic sources and suggest major Acadian uplift of Inner Piedmont sources during convergence of the exotic Carolina terrane with the New York and Virginia promontories. Hence, the Acadian orogeny not only generated high mountain source areas capable of supporting glaciation in a subtropical setting, but also through deformational foreland loading, abetted regional subsidence and the incursion of shallow seas that allowed mountain glaciers access to the open sea.