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Detailed Mapping and Stratigraphic Studies of the Mancos Shale

Task Objectives

Our objective is to characterize and geologically map the Mancos Shale in the Gunnison Gorge National Conservation Area (GGNCA), and to determine this detailed stratigraphic framework throughout the Montrose-Delta County area. Ultimately, the geologic mapping may be extended to the Book Cliffs and the Grand Valley in western Colorado, and to the Uinta Basin and other Mancos Shale Landscapes in eastern Utah, depending on the final scope and goals of the Mancos Shale Landscapes project.

Highlights & Key Findings

Mancos Shale in the southeast Uinta-Piceance basin is 3800-4300 feet thick, and includes time-correlative shale equivalent to most of the Pierre Shale in the Denver Basin. Lithologies temporally equivalent to the Graneros, Greenhorn, Carlile, and Niobrara in the type section of the Mancos Shale in the San Juan Basin comprise the lowest 1700-2200 feet of the Mancos Shale in the Delta area. The Mancos Shale in the Gunnison Gorge National Conservation Area largely consists of the lower half of the full Mancos thickness. Calcareous shale equivalent to the Niobrara Formation, Smoky Hill Chalk Member is present in the uppermost exposures of the Mancos in the Elephant Skins area where detailed geochemical and mineralogic sampling was conducted. Detailed sampling was also conducted in Niobrara equivalents of the Mancos.

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