LATE CRETACEOUS TO PALEOGENE TECTONO-STRATIGRAPHIC EVOLUTION OF THE SOUTHERN PROVO SALIENT: NEW INSIGHT FROM DETAILED MAPPING AND GROWTH STRATA ANALYSIS IN THISTLE, UT

New mapping and growth strata analysis of synorogenic deposits in Thistle, UT provide a high-resolution tectono-stratigraphic development for the southern Provo salient and help to disentangle the relative roles of tectonics, eustasy, climate and sediment supply. We present a 1:24,000 geologic map of the Thistle 7.5’ Quadrangle, a detailed (1:12,000) growth-strata map showing syntectonic unconformities, lithofacies and flooding surfaces, and four detailed stratigraphic profiles through growth strata in Dry Hollow area. The data delineate 11 phases of uplift from latest Santonian to Early Paleogene, the location of former uplifts and the response of fluvial, deltaic and alluvial fan depositional systems. The upper Indianola Group (Ki), lower Blackhawk Fm. (Kbh), and lowermost Price River conglomerate (Kpr) contain three syntectonic unconformities with >10° angular discordance and four syntectonic unconformities with 4-10° discordance. These syntectonic unconformities suggest 7 phases when local uplift exceeded sedimentation from the latest Santonian(?) to late Campanian. One major syntectonic unconformity with 30° discordance, and several (2-3) syntectonic unconformities with 2-5° discordance are present within conglomerates of the uppermost Kpr through lowermost North Horn Formation (TKn); this suggests at least four phases when uplift outpaced sedimentation from the latest Campanian to early Paleogene(?). Syntectonic unconformities become more laterally extensive and amalgamated up-section from +/-1 km in the Ki and Kbh to >5 km in the Kpr and lower TKn. The up-section increase in the extent and amalgamation of syntectonic unconformities suggests that thrust-belt structures began as small (< 2-6 km²), localized thrust-cored anticlines that focused fluvial and marine deltaic deposition (Ki, Kbh), and evolved into more expansive (>20 km²) structures that became source areas for proximal, fluvial and alluvial fan systems (Kpr, TKn). Our data support previous work suggesting two primary structural phases in the development of the Provo salient (i.e., incipient Charleston-Nebo thrust propagation followed by duplexing in the Santaquin Culmination), but provide additional detail about the location and kinematics of thrust-belt structures in the southern Provo salient.