EVIDENCE OF PALEO-GELISOLS SUBJACENT TO LATE DEVONIAN DIAMICTITES, APPALACHIAN BASIN, US

An extensive belt of Late Devonian diamictite stretches along the Appalachian Mountains from West Virginia to northeastern Pennsylvania. The diamictite is present in the Spechty Kopf and Rockwell Formations in Pennsylvania and Maryland, and the Catskill and Hampshire Formations in West Virginia. Contrasting interpretations on the diamictite’s origin vary from submarine debris flow, to tsunamiite, to tidewater outlet glaciers, to piedmont glaciers. The pervasive presence of striae on clasts, dropstones in laminites and polymictic, exotic far-traveled clasts within the diamictite suggest that these deposits formed in association with glaciers. Furthermore, we have found evidence of cryoturbation in paleosols stratigraphically beneath the diamictite layer at two localities; Witinski Villa (WV), Pennsylvania, and Bismark (BSM), West Virginia, as well as possible evidence of permafrost at several locations coeval with the glacigenic interval. A paleosol profile directly beneath the diamictite facies at WV preserves evidence of frost wedging in downward tapering sandy infills coarser than the host soil. These features are like those found in modern-day thermokarst landscapes from soils with permafrost (gelisols). Infills are visible across the entire outcrop. At BSM, ellipsoid-shaped sandy infills are found within a paleosol near the diamictite facies and are coarser than the surrounding paleosol. Collectively, we posit that these infills are evidence of terrestrial landscapes that contained permafrost. Thus, the diamictites and correlative cryoturbated paleosols indicate a broad area of periglacial climate that extended over much of the Appalachian Basin during the Late Devonian. Contemporaneous glacial deposits are found in the paleo-high-latitudes of Brazil, located closer to the south pole. These Appalachian glacial facies signify a transition from hothouse to icehouse conditions near the end of the Devonian Period.