--> Differential Subsidence as a Depositional Control, Frontier Formation, South-Central Wyoming, by B. L. Mieras; #90986 (1994).

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Abstract: Differential Subsidence as a Depositional Control, Frontier Formation, South-Central Wyoming

Barbara L. Mieras

Facies typical of incised valley fill occur at several stratigraphic levels within the mid-Cretaceous Frontier Formation of south-central Wyoming. In many cases, however, subsurface and outcrop data fail to define incised valleys associated with these facies. Although such depositional units are sharp-based and commonly represent significant basinward shifts in depositional environment, they do not appear to be associated with events which produced lateral differences in incision of underlying strata. Instead, their emplacement and preservation appear to be related to lateral differences in subsidence, accompanied by preferential movement of sand-sized clastic material into more rapidly subsiding areas. Strandline and typical valley fill facies detached from older shorelines may be as ociated with relative sea level fall resulting from laterally differential subsidence as well as with regressions forced by eustatic variation. The absence of well-defined valley margins and the absence of differential incision at the base of valley fill facies suggest sequence development associated with laterally differential subsidence. Subsidence-controlled facies development occurs at intra-basinal to regional scales, and valley fill facies controlled primarily by differential subsidence may develop in concert with or in opposition to concomitant variations in eustatic sea level.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994