The research studied a subterranean sediment deposit in an abandoned underground passage and soils from a sinkhole within the Scott Hollow drainage basin, Monroe County, southeast West Virginia. The purpose was to decipher how the lake formed, and the origin of the deposited sediment.
Two excavations in the sinkhole overlying the eastern portion of the cave and a total of 11 samples were collected for study. 174 m of cave passage was mapped to delineate the morphology, calculate passage volume, volume initially covered by sediment and the current volume of sediment in place. Five profiles were made from the cave, and 32 sediment layers sampled. Grain size and environmental magnetic analyses were conducted. A composite stratigraphic column of the subterranean sediments was constructed to establish depositional sequence.
The results indicated that the overlying soils form part of Teas-Calvin-Litz and Frederick-Duffield-Dunmore soil associations. The survey showed that lake was formed from partial conduit blockage by damming of the stream when the ceiling of the cave collapsed. 517 m3 of fluvial sediment was then deposited, of which 64% has since been eroded. There is currently 1398 m3 of open passage volume. The deposition was from two major hydrologic ” depositional cut and fill phases resulting to the four sediment terraces. The lower terraces are younger than the upper terraces, as evidenced by the lower sediments lapping onto the upper terrace. Channel and wall irregularities and the breaching of the dam resulted in irregular deposition and erosion of the sediment.
The environmental magnetic studies showed high magnetic mineral concentrations, abundant superparamagnetic grain fractions, and both low and high magnetic coercivity minerals. Correlation of the magnetic mineralogy, however, showed the subterranean sediment to be composed of high coercivity minerals (goethite) and the soils composed of low coercivity minerals such as magnetite. Although correlation of soils and cave sediment was not possible based on magnetic mineralogy, there existed a general correlation between the layers of sediment found within the stratigraphic column constructed from the cave sediment.
The morphology of the cave and the sediment present substantiate that sediments were deposited due to partial conduit blockage from damming of stream. Grain size analyses indicate that samples are mainly of clay, silt, sand, pebbles and some cobble size fractions. Gravel mineralogy is shale and chert. Shales in the sediment and the cave wall are both fine grained and smooth in texture, with light ” dark gray to greenish gray coloration. This is different from shales found in the soils which have light-gray color. Based on these findings, it can therefore be argued that gravels found in the cave sediment did not originate solely from outside the cave. The color of the samples was determined in-situ. This may have led to apparent differences in color due to variable moisture conditions. The hypothesis that cave sediments were derived from a sinkhole overlying the eastern environs could not be substantiated because of the imprecise correlation established between cave sediment and sinkhole soils. The cave sediments are likely autochthonous at least in part.