Stratigraphy and Sedimentology of the Decie Ranch Member of the Skinner Ranch Formation, Lenox Hills, West Texas

The coarse-grained Decie Ranch member of the Skinner Ranch Formation in the Lenox Hills, West Texas, is comprised of five deeply incised channels. These channels range in thickness from 70 to 110 feet and their thicknesses suggest they formed on a relatively steep gradient. Each successively younger channel is laterally offset to the southwest suggested an organized and not random stacking of channels. Filling these channels are thick-bedded, structureless sandstones with common cobble to bolder sized bioclasts and mudstone rip-up clasts. These lithofacies are interpreted as a mixture of bed-load and suspension fallout sediments from gravity flows. The lack of wave related structures suggests deposition below storm wave base. These beds are interpreted to have been formed in a confined deepwater channel system in an upper slope to outer shelf setting based on the interpreted high gradient related to channel thicknesses, and the abundance of gravity flow deposits. The apparent organized stacking of the channels suggests a leveed system with the levees influencing the stacking of the channels. Overall, the Decie Ranch member is interpreted as a lowstand deposit associated with a relative fall in sea level when coarse sediments were delivered directly to the upper slope and basin. This is further supported by the overlying Polar Tank Member, which is interpreted as a transgressive/highstand deposit related to a shift in deposition in a more landward direction and a lack of the course sediment being delivered to the basin.