The Mountain Geologist · 1967 · 46 citations · 0 references
ABSTRACT: The Phosphoria Formation of western Wyoming consists primarily of chert and phosphatic black shale that is believed to be the source of most of the oil in Permian and Pennsylvanian rocks of central Wyoming.* The Phosphoria Formation intertongues eastward with the Park City Formation and is underlain by the Tensleep Sandstone. Both of these units contain many porous and permeable beds that are suitable conduit and reservoir rocks. The Phosphoria and Park City Formation are overlain by the Dinwoody Formation and the Park City Formation intertongues eastward with the Goose Egg Formation. Both the Dinwoody and Goose Egg Formations are non-permeable sealing beds. Hydrocarbon fluids squeezed out of the Phosphoria Formation into the adjacent conduit beds migrated eastward into structural and stratigraphic traps in the intertonguing sequence and into structural traps in the underlying rocks. Trace elements exhibit similar distribution patterns in the Phosphoria black shale beds and in accumulations of crude oil farther to the east, thus providing support for this hypothesis. The driving force for the eastward fluid migration is believed to be the differential loading of the sedimentary rocks during development of the Cordilleran miogeosyncline and the craton, as well as tectonism in the miogeosyncline,