The quantitative lithofacies analysis of the Potomac Formation in a small area west of Delaware City revealed that the deposition of these sediments was continuous throughout the time of their formation. The uppermost part of the Potomac sequence appears to have been removed, probably by erosion, prior to the deposition of the younger Upper Cretaceous marine sediments. The sand bodies contained in Potomac deposits have a shoestring channel form and were most probably deposited by unidirectional currents. The direction of the flows, however, cannot be determined on the basis of the available subsurface data.