Paleoenvironmental Interpretation of Bandera Sandstone (Marmaton Group, Desmoinesian), Labette County, Kansas

Zach Koch and C. D. Burke. Department of Geology, Wichita State University, Wichita, KS  67260-0027  [email protected]

The Bandera sandstone in Labette County is well exposed in the Deer Creek. The exposure ranges in thickness from 1 to 7.5 m and consists of well-sorted quartz, abundant plant remains, carbon films, and interbedded mudrock. The unit is characterized by stratification that ranges from cross stratified to thin-medium beds upsection. The uppermost 5 ft (1.5 m) contains thin- to medium-bedded sandstones and mudrocks that are underlain by sandstone containing large fossilized logs of the lycopod Lepidodendrum. Several of these exposed branches or trunks average 20 cm in diameter and 95 cm in length. Total length could not be accurately measured as they extended into the hillside. Lower in the unit, sandstone are cross stratified and abundant ripple marks exist on bedding planes.

Sedimentary structure, texture, and fossils suggest that the Bandera sandstone was deposited in a siliciclastic environment that changed through time. The lowermost portion of the unit was probably deposited in a dominantly fluvial environment, whereas the upper unit was deposited under dominantly marine (or estuarine) conditions. Evidence also exists that the upper unit contains storm deposits. Data from these exposures support the interpretation that the Bandera Shale/Bandera Quarry Sandstone Member is a siliciclastic complex that prograded during a sea-level fall. The sandstones were re-worked as sea level rose during middle Marmaton time.