Abstract

Conglomerate and sandstone that unconformably overlie Proterozoic and Paleozoic strata in the Canyon Mountains of central Utah are herein formally designated the Canyon Range Conglomerate. These strata have previously been assigned to the Indianola(?) Group, Canyon Range fanglomerate, Canyon Range Formation, and Canyon Range Conglomerate. The name is extended to the Pahvant Range, where equivalent strata have previously been included in the Price River Formation, and to correlative strata in the subsurface of the Valley Mountains. The Canyon Range Conglomerate is also exposed locally in the northeasternmost Valley Mountains, where it has been previously included in the Indianola Group and Price River Formation. Surface and subsurface palynomorph data and regional correlation indicate that the Canyon Range Conglomerate is restricted to the Cretaceous, ranging in age from Albian(?) through latest Campanian to possibly Maastrichtian. It therefore correlates with much of the fill of the foreland basin to the east, although its base is probably somewhat younger than the oldest Lower Cretaceous strata, the Neocomian to middle Albian Cedar Mountain Formation, of the foredeep. As defined here, the youngest member of the Canyon Range Conglomerate in the Canyon Mountains probably correlates with the North Horn Formation exposed in ranges to the east.

Exposed thickness of the Canyon Range Conglomerate ranges from 280 m (920 ft) to approximately 1720 m (5640 ft) and increases eastward from the Canyon Mountains and Pahvant Range into the subsurface. The conglomerate was deposited predominantly in interfingering alluvial-fan and fluvial settings in a wedge-top basin that lay west of the Levan culmination. The oldest strata of the Canyon Range Conglomerate overlap the Canyon Range thrust, and thus postdate movement on the thrust. Prominent growth strata in alluvial-fan complexes record development of the Canyon Range syncline in the hanging wall of the thrust and attendant out-of-the-syncline flexural slip faulting as the thrust sheet was deformed by the Canyon Range culmination, exposed on the west flank of the Canyon Mountains. Growth strata also record deformation, beginning slightly later, of the Canyon Range thrust sheet above the rising Santaquin culmination to the north. Widespread deformation of the Pahvant and Canyon Range thrust sheets and development of the Levan culmination to the east took place synchronously in the central Utah thrust belt; this coeval deformation is interpreted to have resulted from displacement on the structurally subjacent, younger Paxton thrust.