Revised exhumation history of the Wind River Range, WY, and implications for Laramide tectonics

Title of Publication: 
Revised exhumation history of the Wind River Range, WY, and implications for Laramide tectonics
Stevens, Andrea L., Balgord, Elizabeth A., Carrapa, Barbara
Publication Info: 
Tectonics, June 16

A reanalysis of apatite fission track (AFT) thermochronology coupled with thermal-kinetic modeling of samples from the Wind River Range document Late Cretaceous to early Eocene episodic cooling and exhumation of one of the largest basement-cored ranges in the western United States. Three vertical transects taken at different latitudes along the length of the 145 km Wind River Range reveal that exhumation is uniform along strike suggesting steady displacement along the Wind River Fault, and significant exhumation and relief in the Wind River Range by the early Eocene. Thermal modeling of AFT ages, lengths, and compositional proxies document rapid exhumation from ~65 to 50 Ma. This rapid exhumation episode matches a period of accelerated subsidence in the adjacent Green River and Wind River basins. At ~50 Ma, exhumation dramatically slowed by an order of magnitude coincident with decreasing subsidence in the adjacent basins. No signal of Oligocene cooling is apparent in either AFT cooling ages or thermal modeling suggesting that a possible later phase of reactivation of structures and uplift, as previously suggested, was limited to less than approximately 1 km of exhumation.

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Figure 2. Cross sections showing the age of samples along the Middle Fork Lake and Temple Peak traverses with sample ages from Cerveny and Steidtmann [1993] for comparison along with interpreted thicknesses of sedimentary cover along the Wind River Range. Cross sections are modified from Yonkee and Weil [2015], with stratigraphic relations from Winterfeld and Conard [1983], Seeland [1978], and Phillips [1983]. The detrital cobble with the Paleocene cooling signal is shown in A and was deposited in the Wind River Formation (deposition age 53–51 Ma).