The 60m thick, Upper Cretaceous (Campanian - Maastrichtian) Bearpaw - Horseshoe Canyon transition zone is exposed in three-dimensions along the Red Deer Valley and its tributary Willow Creek, near Drumheller, Alberta. These clastic marine to marginal marine deposits represent shoreface, fluvio-estuarine, lagoonal and coastal plain environments. These deposits are divided into seven, informal allomembers (A to G), each of which contains a transgressive and regressive phase. Allomembers are defined by marine and brackish flooding surfaces which commonly occur above thin (0.3 to 2 m) coal seams. Erosional relief along these surfaces is minimal. During regressive phases prograding sharp-based shorefaces (sometimes indicative of forced regressions) are deposited in the marine realm while nonmarine settings are characterized by non-deposition. Fluvial incision is associated with shoreline regression in allomembers A, C and D. Depositional records of transgressions in the marine realm are thin or absent. In nonmarine settings, however, transgressive deposits may attain substantial thicknesses where marine-influenced deposits infill some incisions and initially coals and then back-barrier/lagoonal deposits accumulate behind retreating barrier systems. The sharp, basal contacts of the coals with the underlying shoreface or back-barrier deposits represent the turnaround points from regressive to transgressive conditions. The overall succession represents a seaward-stepping or regressive system. Estimated amounts of sea level change within each allomember range from approximately 4 to 12 m. Transgressive/regressive units have an estimated fourth order periodicity of 140,000 years. Sequence analysis of the succession suggests that in terms of Exxon sequence stratigraphy, it may be subdivided in two ways depending upon the degree of resolvable detail applied. Application of high resolution sequence stratigraphic techniques suggest that the succession can be divided into three discrete, high frequency (4th order) sequences which constitute part of a third order composite sequence. Within these high frequency sequences, transgressive, highstand and a newly-proposed ＇Falling-stage Systems Tract＇ (FST) are recognised. Alternatively, if high resolution details are ignored (e.g., in a seismic study), the succession may be regarded as part of one, third order sequence exhibiting transgressive and highstand systems tracts. However, because of the problems involved with applying Exxon sequence stratigraphy, Genetic sequence stratigraphy and T-R sequence stratigraphy on such a high resolution scale, allostratigraphic subdivision of the strata is preferred due to its simple application and flexibility.