Regional subsurface correlation of the ＇＇Basil Belly River＇＇ sandstones throughout southern Alberta and Saskatchewn suggests the unit can be divided into a series of at least seven stacked, composite, primarily regressive cycles (fourth-order subunits). Each cycle has continental/coaly deposits in the west, a central belt composed of stacked shoreline-related sandstones, and thins to the east. Within lower cycles, laterally-distinct depositional lobes probably relate to long-lived sediment input points around the active margins of the foreland basin. Input form the west and northwest was consistently more dominant than that from the south and southwest. Mapping reveals that the locus of sandy deposition of each successive cycle is located eastward of, and stratigraphically higher than, the preceding one. This indicates that the imbalance between sediment supply from the west and subsidence of the Campanian foreland basin allowed overall eastward, but noncontinuous, progradation of the elastic wedge over more than 500 km across southern Alberta and southwestern Saskatchewan during deposition of the ＇＇Basil Belly River＇＇ (2-5 m.y.). More pronounced vertical stacking of cycles, and thicker development of backshore coal zones, to the east reflects increasing aggradation through time related to an increase in rate of base level rise, probably due to more rapid basin subsidence. Each composite cycle, as mapped here, included several to many individual (fifth-order) subunits bounded by localized transgressive surfaces, which are both stratigraphically and geographically limited. In addition, each cycle encloses a specific set of gas pools and represents a specific exploration trend. Within each, production is obtained from both shoreface-related and channelized facies.