A study of the McCourt Sandstone Tongue and the Glades coal bed of the Upper Cretaceous Rock Springs Formation in the Rock Springs coal field has provided valuable data for reconstructing an ancient coal-forming depositional environment. The sandstone and coal were deposited on a strand plain along the western shores of the Late Cretaceous interior seaway of North America. The McCourt Sandstone Tongue consists of a sequence of lenticular, eastward offtapping, north-northeast-trending, quartzose sandstone shoreline deposits. Lithofacies include lower and middle shoreface, surf, and forebeach, which are well preserved and are identifiable by their color, stratigraphic position, and sedimentary structures....