Tectonic and Depositional Controls on Selected Upper Cretaceous Shoreline

Morphologies in the Greater Green River and Wind River Basins, Wyoming and the Sand Wash Basin, Colorado

By

Michael L. Hendricks

Hendricks and Associates, Inc, Englewood, CO

Mapping of ancient shoreline trends in central and southwestern Wyoming and northwestern Colorado can delineate petroleum reservoir trends. Controls on shoreline trends include rates of deposition and subsidence, prominence of wave or tidal energy, and paleostructure. The Rock Springs Formation shoreline trends were wave dominated, and microtidal energies produced minor tidal inlets and associated tidal and coastal plain deposits. Marine Almond sandstones and parts of the Fox Hills Sandstone were deposited in embayments. Increased tidal energy produced prominent tidal inlets and associated mesotidal deposits.

The embayment near the western limits of the marine Almond sandstone had a structural control. Detailed mapping of Mesaverde strata along the east flank of the Rock Springs Uplift shows the ancient Wamsutter Arch, or faults associated with the arch, controlled thickness and facies distributions. This arch has numerous east-west trending faults. Several of these faults had recurrent movement that exerted control on depositional trends.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming