25 Coastal Sedimentology, Stratigraphy, and General Sedimentology (Posters)

Tuesday, 15 March 2005
1:00 PM - 5:00 PM

PRELIMINARY OBSERVATIONS OF AN UPPER DEVONIAN HAMPSHIRE PALEOSOL SEQUENCE IN THE CATSKILL CLASTIC WEDGE OF WEST VIRGINIA

Paper number: 25-11
Program: Technical Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

New exposures of Upper Devonian Hampshire strata in roadcuts near Elkins, West Virginia reveal a series of vertically stacked paleosols deposited during the late regressive stages of the Catskill Clastic Wedge. This paleosol sequence is truncated and overlain by fluvial deposits with a basal lag containing locally-derived rip-up clasts. Pedogenesis occurred during periods of landscape stability that geochemically and morphologically altered non-marine alluvial facies of the Hampshire Formation. Support for a nonmarine setting includes fluvial channel deposits and lags, coalified fossil plant debris, and a lack of marine invertebrate and trace fossils. Pedogenic features include a variety of calcareous nodules, relict soil structure and horizonation (stratification), preserved root impressions, carbonized roots, redoxomorphic features and colors, clay skins, weak small-scale vertic features and a pronounced weathering front. Pedogenic characteristics at this locality suggest a significant duration of landscape stability and pedogenesis in floodplain and overbank alluvial sediments and may be of paleo-Inceptisol and paleo-Vertisol soil orders.

Inceptisols may form in floodplain-alluvial settings due to the episodic deposition of sediment and disruption of established environments during flooding. However, Vertisols suggest a significant duration of pedogenesis under a semi-arid to wet-dry seasonal climates. If these are truly Vertisols, did they develop under a hot-dry or cool-dry environment? Geochemical and mineralogical investigation of individual paleosol horizons is underway to confirm these interpretations.

Sedimentary features observed in both slightly older (Upper Devonian Foreknobs Formation near Elkins, WV) and younger (Upper Devonian-Lower Mississippian Spechty Kopf Formation in Pennsylvania) late Catskill regressive strata suggest that extreme climatic conditions related to the beginning of Late Paleozoic global cooling had a recognizable role in the depositional process.