GeoDigital Information's study of the Muddy Sandstone in the Wind River Basin examines the stratigraphy, sedimentology, petrography, and oil and gas potential of the Muddy Sandstone in the Wind River, southern Big Horn, northern Shirley, northern Hanna, and northern Red Desert basins. This area covers approximately 497 townships and 18,000 square miles (figure 1). The study, representing six man-years of geologic research, provides the explorationist with a chronostratigraphic framework for the lower Cretaceous Thermopolis, Muddy, Shell Creek, and Mowry formations. Also included in the study is a sedimentologic and reservoir characterization analysis of valley-fill deposits along the Grieve Oil Field trend in the southeastern Wind River Basin.

Lower Cretaceous Statigraphic Framework - The Lower Cretaceous stratigraphy of the Wind River Basin consists of, in ascending order, the Cloverly and Lakota formations, Thermopolis Shale, Muddy Sandstone, Shell Creek Shale, and Mowry Shale. Eleven formation tops or bentonite marker beds and seven member of the Muddy Sandstone were correlated and mapped throughout the study area. Regional cross sections tie stratigraphic intervals from the study area to the Powder River and Greater Green River basins.

Although rarely greater than 100 feet thick throughout most of eastern and central Wyoming, GDI subdivided the Muddy Sandstone into seven mappable, chronostratigraphic members, which are bounded by bentonite beds or unconformities. This chronostratigraphic methodology facilitated mapping of time-bounded lithofacies sequences and reconstruction of paleogeography through time. Of greatest importance was the recognition and mapping of a complex paleovalley system and marine shoreline trends within the Wind River Basin.

Grieve Oil Field Trend - Exploration interest in the Wind River Basin was generated by discoveries along the Grieve Oil Field trend, which includes the prolific Grieve, North Grieve, and Sun Ranch fields. The play consists of fluvial/estuarine valley-fill deposits. GDI's analysis of the stratigraphy, sedimentology, and petrographic characteristics of the Grieve Oil Field trend is designed to assist exploration and production geologists in understanding the complex stratigraphic relationships, fluvial/estuarine valley-fill geometries, diagenetic history, and hydrocarbon production within the trend. The study discusses the potential for other valley-fill and marine shoreline trends throughout the Wind River Basin.