The lower Blackhawk Formation and the Star Point Sandstone of the southern Wasatch Plateau are the lower deltaic and nearshore facies, respectively, of an Upper Cretaceous regressive deltaic sequence. Economic coal beds are associated with peat-forming environments in both the lower delta plain and the accretionary ridge-distributary mouth bar subfacies of the delta.
Discontinuities (rolls, splits, and pinch-outs) within the coal beds of the accretionary ridge subfacies are controlled primarily by: (1) proximity of the peat marsh to the high-energy shoreline environment, (2) relative compaction ratios of channel sands and finer detritus over which the peat marsh developed, and (3) topographic expression of the paleodrainage network incised within the top of the underlying Star Point sediments. Discontinuities (rolls, splits, pinch-outs, and washouts) within the coal beds of the lower delta plain subfacies are controlled primarily by: (1) proximity of the peat swamp to laterally contemporaneous distributary channels, (2) relative compaction ratios of underlying sands and finer detritus, and (3) erosion of the heat beds by basal scouring of overriding distributary channels.
Detailed outcrop measurements and drill hole data are used to develop accurate, site-specific, paleoenvironmental models to define the areas of potential coal-bed discontinuities and to aid in local exploration and mine planning.