Patterns of Cretaceous shallow-marine sedimentation, Coalville and Rockport areas, Utah
Cretaceous strata exposed in the Coalville and Rockport areas of north-central Utah accumulated in alluvial-fan, fluvial, marginal-marine, nearshore-marine, and offshore-marine depositional environments. Marine sediments were deposited in this region during periods of peak inundation of the Aspen-Mowry, Greenhorn, and Niobrara marine invasions. Deposits of each marine invasion may be divided into a number of depositional sequences, each of which contains a basal disconformity and is bounded above by the disconformity associated with the next overlying sequence. Some of the basal disconformities are identified as ravinements. All depositional sequences are entirely progradational. Retrogradational shallow-marine deposits appear to be completely lacking. Absence of depositional sequences recording marine transgression is attributed primarily to the process of shoreface erosion and to marked reduction of the quantity of sediment introduced to shallow-marine environments by rivers during periods of rising relative sea level. Deposits of major marine cycles of deposition at the western margin of the Interior Cretaceous seaway in north-central Utah do not conform to the simple symmetric transgressive-regressive models of some authors, but they record many back-and-forth movements of the strand.