Paper No. 6
Presentation Time: 10:00 AM
PROVENANCE OF THE CORBIN SANDSTONE MEMBER OF THE GRUNDY FORMATION (LOWER PENNSYLVANIAN) IN EAST-CENTRAL KENTUCKY
The Corbin Sandstone is a member of the Pennsylvanian age Grundy Formation in eastern Kentucky. It is a fine- to medium-grained, buff to reddish colored, quartz arenite to sublitharenite. In addition the Corbin is cross-bedded and contains concentrations of rounded quartz pebbles. This study is an attempt to determine the provenance of the Corbin Sandstone Member. Provenance refers to the origin of sedimentary particles. It is a determination of the location and composition of the parent rocks from which sediments were derived. Eighty eight samples were collected from nine localities across east-central Kentucky. Thin-sections were cut and point counts made of the various types of quartz present in each sample. Quartz was grouped into a number of distinct classes according to the scheme suggested by Basu, et al (1975). Two types of quartz grains dominate the assemblage: (1) monocrystalline quartz showing undulose extinction and (2) polycrystalline grains composed of more than three subunits. The larger, quartz pebbles were mainly milky quartz. This assemblage suggests a low-rank metamorphic source area for most of the quartz in the Corbin. The quartz pebbles are believed to be derived from hydrothermal quartz veins that must have also been present in the source area. A heavy-mineral separation was also conducted on these samples to further aid in the determination of their provenance. The assemblage was dominated by rounded grains of zircon, rutile, and tourmaline. Angular grains of pale brown tourmaline were also observed. The presence of pale brown, angular tourmaline grains also supports a low-rank metamorphic origin for these sediments. In addition, rounded grains of zircon, rutile and tourmaline hint at a source area that also included a considerable amount of reworking.