The integrated use of seismic reflection data and conventional well logs allows a time stratigraphic reconstruction of lithofacies in the Fort Union Formation in the western part of the Wind River basin, a sedimentary and a structural basin formed during the Laramide deformation. During latest Cretaceous through early Eocene time, the basin was infilled with a continuous sequence of alluvial, fluvial, and lacustrine sediments. The Paleocene Fort Union Formation can be divided into two general lithologic units: a lower fluvial unit of sandstone, conglomerate, shale, and carbonaceous shale and an upper unit of fine-grained clastics deposited in and adjacent to Waltman Lake.

Lithofacies in the Fort Union Formation can be recognized on seismic reflection data as lateral variations in the reflection amplitude and continuity. Three major unconformities are recognized within the Fort Union Formation. Two unconformities are indicated by strong reflectors with widespread continuity at the top of the lower Fort Union and about 300 ft (91 m) below the top of the lower Fort Union. A third unconformity is present at about the middle of the upper Fort Union Formation. Mapping of seismic facies with the aid of scattered well control allows the reconstruction of regional depositional settings and lithofacies.

Analysis of the stratigraphic framework of the Fort Union Formation is useful in providing a rationale for future hydrocarbon exploration. Gas production from the Fort Union Formation at Pavillion, Fuller Reservoir, and Frenchie Draw fields is a combination of structural and stratigraphic trapping.

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