EVALUATING AN UNUSUAL LIMESTONE-PEBBLE CONGLOMERATE IN THE UPPER HINTON FORMATION NEAR EADS MILL, WEST VIRGINIA

The Hinton Formation is the middle formation of the Mauch Chunk Group in southern West Virginia. It is composed of interbedded fine-grained sandstones, red mudstones, occasional limestones, and shale. The Upper Hinton formation, comprising all the strata between the Avis Limestone Member and the Princeton Sandstone, contains two sets of marine strata. At the Brush Creek Reserve, near Eads Mill, the upper set of marine strata appears to have been replaced by an unusual cross-bedded limestone-pebble conglomerate.

The conglomerate is a clast-supported limestone conglomerate with a matrix of quartz sand and clasts of coal, marcasite, pyrite, and some apparent marine fossil spines and fragments. The clasts are pebble sized, with a few slightly over the pebble-size boundary and one reaching 13 cm along the long axis, and primarily rounded to sub-rounded. Other exposures at this outcrop display well developed planar cross bed sets approximately 2 meters thick, suggesting a high energy water discharge, similar to a large stream, river, or storm rip-up. The storm rip-up would provide an environment to round the limestone, create cross beds, and preserve the iron sulfides through immediate burial.