Mesozoic and Cenozoic thermal history of the Canyon Range, Pavant Range, and vicinity, central Utah

Apatite fission-track analyses and modeling results from the Canyon Range, Pavant Range, and vicinity, west-central Utah demonstrate that the area experienced a complex thermal evolution during Mesozoic and Cenozoic time. The thermal evolution was controlled to varying degrees by Late-Jurassic to Eocene contractile deformation of the Sevier orogenic belt and by Cenozoic Basin and Range extensional tectonism. The Canyon Range allochthon in the Canyon Range cooled by 150 Ma during its emplacement, initial cooling of the allochthon in the House Range may have occurred later. Cooling of the Pavant allochthon occurred by 110 Ma during its emplacement. Subsequently, the Pavant allochthon was reheated to between 120{dollar}spcirc{dollar}C and 150{dollar}spcirc{dollar}C during Late Cretaceous and Paleocene time, probably due to burial by synorogenic debris. The allochthon experienced temperatures between at this time. Fission-track data from synorogenic conglomerates in the Canyon Range, Pavant Range, and Gunnison Plateau show little correlation with stratigraphic age. However, the data agree with recent studies suggesting that most of the exposed synorogenic debris was derived from a large structural culmination that developed in the area during Late Cretaceous time.; Fission-track ages in the Canyon Range and Pavant Range decrease from east to west. In the Canyon Range, this is explained by rotational uplift of the footwall of the Sevier Desert detachment fault. Rocks exposed along the western part of the range had experienced temperatures in excess of 150-160{dollar}spcirc{dollar}C prior to extension, implying at least 5-6 km of uplift during extension. The rocks cooled at a rate of at least 20{dollar}spcirc{dollar}C/Ma about 20 Ma. Surface evidence for crustal-scale extension is lacking in the Pavant Range, although fission-track data suggest that Cenozoic rotational uplift of the range was similar to that in the Canyon Range. The precise timing of this event is unclear, and modeling of the fission-track data suggests possible cooling by erosional unroofing. Whether or not Cenozoic cooling of the House Range and Cricket Mountains is related to extensional tectonism or erosional unroofing is unresolved by current fission-track data.