Cambrian and Mississippian deposits of sandstone and limestone represent marine transgressions from the west. The Uncompahgre Mountain was uplifted in Pennsylvann time, and conglomerate near the uplift grades northward into finer clastics and limestones. Permian through Jurassic deposits represent four marine transgressions from the west and intertongue eastward into thinner non-marine strata. During Cretaceous time the area received 6,000-12,000 feet of Mancos shale and Mesaverde sandstones. Tertiary regional uplift created the Uinta basin, which contains up to 18,000 feet of lower Tertiary fluviatile and lacustrine deposits.

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