STRATIGRAPHY OF UPPER HINTON FORMATION SANDSTONES IN THE BLUESTONE RIVER GORGE, SOUTHERN WEST VIRGINIA

This project’s objective is to characterize the geometry and distribution of sandstones between the Little Stone Gap Member and the base of the Princeton Sandstone. In doing this, several sections were measured, and the area was mapped at approximately 1:6900 by walking out contacts between beds in well exposed canyon outcrops. The sandstones can be divided into two lithologies. One is characterized by meter-scale trough and tangential crossbeds, local basal polymictic conglomerates containing intrabasinal clasts up to 34 cm across, and local rhythmic laminations. The other is characterized by 1 to 3 cm trough and tangential crossbeds with some herringbone sets, rhythmic laminations, flaser bedding, ripple bedding, and climbing ripple cross laminations. These are herein referred to as Tallery-type and Falls Mills-type on the basis of comparison with existing descriptions.

The geometry of these units is variable. There are three 5 to 14 m thick laterally extensive sandstone bodies. The lower two bodies are Tallery-type, and the upper body is of the Falls Mills-type. Sandwiched between these laterally extensive bodies is a series of overlapping lenses of both lithologies of up to 12 meters in thickness. Typically the laterally extensive Tallery-type bodies are overlain by local Falls Mills-type lenses, and the laterally extensive Falls Mills-type body is underlain by somewhat more extensive Tallery-type lenses. Isolated lenses of both lithologies can also be found, and lenses of both types are often in contact. There are, however, some exceptions to this pattern. Contacts between the two lithologies are abrupt and often marked by a thin scour with local rip-up clastes. In some cases, one lithology will be incised into another. The geometry of these units coupled with the nature of the contacts suggests a lateral interfingering of tidal and fluvial depositional environments with punctuated periods of deposition in a broad singular environment that is either predominantly tidal or fluvial.