Rocks rich in organic matter are widespread in the Lower Cretaceous Mowry Shale and its marine time equivalents throughout much of the northern part of the western interior of the United States. In contrast, true source beds in which petroleumlike hydrocarbons have been formed have a restricted distribution due, apparently, to variations in the thermal history of the strata. Only in samples from areas where the Mowry has been buried more deeply than approximately 7,000 ft have petroleumlike hydrocarbons been found. Depth-of-burial studies, therefore, provide a valuable means for anticipating source bed development.

All known oil fields in the Muddy, Frontier, and other sandstone reservoirs associated with the Mowry interval are either within or updip and adjacent to areas where source beds have been found. Thus, the regional distribution of oil accumulations in these reservoirs is predictable with knowledge of the source-bed distribution.

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