Structural configuration of the Early Cretaceous Cordilleran foreland-basin system and Sevier thrust belt, Utah and Colorado

Stratigraphic and provenance data from Lower Cretaceous rocks in Utah and Colorado and structural evidence from the Sevier belt in west-central Utah allow recognition of the ties between early thrust-belt evolution and foreland-basin system development. Regional isopach patterns of Lower Cretaceous strata define foreland-basin system depozones. Lower Cretaceous strata in west-central Utah that thicken westward from similar to100 mto similar to1.2 km were deposited within the flexurally subsiding foredeep depozone. Correlative units in eastern Utah and western Colorado <100 m thick were deposited in the forebulge depozone while Lower Cretaceous rocks in central Colorado >similar to100 m thick were deposited in the back-bulge depozone. These thickness trends indicate the Lower Cretaceous foreland-basin system consisted of a foredeep similar to100-180 km wide and forebulge similar to260-460 km wide. A computer-generated flexural model of the foreland-basin system produces a reasonable match of the observed basin geometry using a 400-km-wide load with a maximum elevation of 2.5 km located in western Utah. The load used in the model is similar to restored, balanced structural cross sections of the Sevier thrust belt that indicate thrust loads associated with the Canyon Range and Pavant thrusts were at the same location and of similar magnitude during Early Cretaceous time.