Abstract

The Sussex Sandstone was deposited as part of a series of extensive sediment sheets which prograded southward and eastward into the central part of the Late Cretaceous epicontinental seaway of western North America. Although surface exposures of these sandstone units are few, lithologic characteristics and lateral and vertical sequences studied in outcrop have been used with core data to interpret well-log signatures in terms of lithologic facies distributions. A depositional model has been developed to account for this sandstone by using modern continental shelf areas as partial analogs and then placing the Sussex sandstone interval within its proper stratigraphic setting. This model calls upon storm-generated and tidal currents to form and shape sand ridge complexes upon prograding sediment sheets. The eastern and southern termini of these sheets were probably marked by abrupt depositional slopes as indicated by lithostratigraphic, biostratigraphic and seismic studies. Petroleum accumulations appear to be localized along the updip edges of high porosity sandstones within the upper portions of the ridge complexes.