Abstract

The Morrison formation in and adjacent to the Colorado Plateau currently includes diverse lithic units, many of which cannot properly be included if the limitations of the type section and relationships to other formations are considered. The Todilto limestone, Bluff sandstone, Wanakah marl, Pony Express limestone, and Bilk Creek sandstone can be correlated with the San Rafael group and dated as Upper Jurassic by the marine beds in the group. The Salt Wash sandstone, Brushy Basin shale, Recapture Creek sandstone, and Westwater Creek sandstone are considered equivalent to the type Morrison and have yielded vertebrate remains and are almost certainly Jurassic. Succeeding these are two new formations, the Buckhorn conglomerate and Cedar Mountain shale, which have yielded no fossils but are tentatively classed as Lower Cretaceous, mainly by analogy with similar deposits in adjacent areas.

Lithology, distribution, and paleogeography of all units are discussed, and changes in nomenclature and correlation are recommended.

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