SURPRISES FROM THE DEVONIAN FOREKNOBS FORMATION OF EASTERN WEST VIRGINIA

Unusual microfossils recently recovered from the Upper Devonian Foreknobs Formation (Greenland Gap Group) of eastern West Virginia suggest that the paleoenvironmental model for the unit may need revision or refinement. In 2012, during an investigation of fresh outcrop exposures of Devonian strata along the Corridor H highway construction project in Hardy County, east of Moorefield, WV, rock samples from lowermost Foreknobs containing a large number of spherical fossil voids resembling ooids were recovered. Because the Foreknobs is a siliciclastic unit with no associated carbonate, the discovery of ooids would be of significance. Consequently, a number of thin sections were made and examined. No ooids were present. However, the spherical objects were determined to be calcispheres, identifiable as the fossilized spore bodies of algae. Two types of calcispheres were present in equal number – Sycidium sp., attributed to fresh to brackish water green algae and Radiosphera sp., attributed to planktonic marine algae. In addition, a single oncoid coated with filaments of the calcified cyanobacteria Girvanella sp. was observed. The remainder of the grains composing the rock consisted of echinoderm fragments, small brachiopods, and detrital quartz. Taken as a whole, this combination of sedimentary material suggests paleoenvironments ranging from fluvial to brackish water lagoon to back-reef marine to normal marine shelf. While the assemblage probably represents a storm deposit, it indicates sedimentary “sampling” of Foreknobs depositional environments that are not preserved or not yet exposed in this part of the Appalachians.