James R. Steidtmann1
(1) University of Wyoming, Laramie, WY
Abstract: Stratigraphy and sedimentology of a proximal, aggradational shoreface system: the Bacon Ridge Sandstone, Teton County, Wyoming
The Late Coniacian through Santonian(?) Bacon Ridge Sandstone is a 200-350 m thick succession of aggradational to slightly progradational marginal marine sediments deposited in relatively close proximity (<100km) to the Sevier thrust front.
Lithofacies include numerous storm-wave dominated shoreface sandstones, silty lagoonal mudstones, and relatively small proportions of offshore marine shales and non-marine carbonaceous shales and coals. Sedimentary packages are grouped into regressive-transgressive couplets that are separated from one another by transgressive surfaces of erosion (TSE). The typical vertical sequence within a regressive-transgressive package consist of a basal TSE, followed by a regressive portion consisting of 2-3 stacked shoreface sandstones, a flooding surface, and an upper transgressive portion of lagoonal mudstones interfingering with thin carbonaceous shales and coals. The stacked shorefaces are up to 25 m of continuous sandstone with individual parasequences delineated by bioturbated, well cemented horizons, and slight changes in grain size and sedimentary structures. The transgressive lagoonal mudstones have internal sequences consisting of biotubated silty mudstones at the base grading upward into carbonaceous shales and coals.
The Bacon Ridge Sandstone is the product of a northeast-southwest trending, vertically aggrading coastline deposited in an area with high rates of subsidence and sediment supply. Within the overall aggradational succession, numerous transgressions and regressions are recorded. The shoreline advanced basinward during regressions as a storm-wave dominated shoreline system. During transgressions the shoreline and coastal plain were flooded, changing the storm-wave dominated shoreline into a barrier island/lagoonal system.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana