New data, chiefly from drilling and palynology, refine age determinations of thick sequences of uppermost Cretaceous, Paleocene, and lower Eocene sedimentary rocks, and indicate types of Laramide crustal movements that occurred in and around the margins of structural basins in central Wyoming. The movements began with extensive downfolding of the basins, which continued to be tectonically active through early Eocene time. Subsidence of large segments of some basins equalled, or exceeded, the uplift of bordering mountains. Vertical movements of adjoining crustal blocks in central Wyoming during Laramide time (latest Cretaceous through early Eocene) are: Subsidence: Wind River basin, 16,000 ft (N.-central); Wind River basin, 14,000 ft (E.-central); and Great Divide basin, 12,000 ft (N.). Uplift: Owl Creek mountains, 17,500 ft; Casper Arch, 7500 ft; and Granite Mountains, 20,000 ft. These relations suggest that Laramide tectonic movements in this region were more vertical than horizontal, despite observed low dips on the shallow parts of many marginal reverse faults.

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