A THICK-SKINNED BASIN INVERSION MODEL FOR THE TECTONIC EVOLUTION OF SANTAQUIN AND PAYSON LAKES QUADRANGLES, SOUTHERN WASATCH RANGE, UTAH

A thick-skinned, basin inversion model explains the structural geometry and thermal maturation patterns of the southern Wasatch Range. Detailed field mapping of the Santaquin and Payson Lakes quadrangles provides evidence for a large wavelength fold containing at least 18 km of measured Proterozoic to Mesozoic rock within the thrust fault’s allochthon. This feature is most likely linked to the asymmetry of the Oquirrh Basin wherein the thickness of the Oquirrh Group and time-correlated sediments abruptly changes westward from 1400 m to 9300 m near Orem. The geometry of the basin indicates it was most likely bounded to the east by a large listric normal fault with associated growth strata. The geometry of contractional structures indicates that the hanging wall of the Oquirrh basin was most likely inverted along reactivated faults to form the Charleston-Nebo thrust sheet. Tmax and TOC (total organic carbon) analysis of the Manning Canyon Shale, Oquirrh Group, and Deseret Limestone within the Santaquin and Payson Lakes quadrangles indicates that all of the samples reached temperatures in excess of the oil window (higher than 120°C), but less than 225°C (where carbon alters to graphite). These data, along with thermochonology data from the Santaquin metamorphic complex yield paleotemperatures for hanging wall units that indicate a burial than could only be reconciled with deposition as growth strata against a listric fault.