The Cedar Hills, an area of about 320 square miles in central Utah between the northern end of the Wasatch Plateau and the southern end of the Wasatch Mountains, form the boundary zone between the Colorado plateaus and the Great Basin. The oldest exposed rocks are Carboniferous, but most of the area is underlain by Upper Cretaceous and Tertiary continental sediments many thousands of feet thick. The Indianola group, about 15,000 feet thick, consists principally of coarse conglomerates and sandstones indicative of near-by orogeny and contains a tongue of fossiliferous marine sandstones showing that it is of Colorado age. This group is overlain unconformably by thick fluviatile and lacustrine deposits ranging from Montana to Eocene in age (Price River, North Horn, Flagstaff, Colton, and Green River formations), which in turn are overlain unconformably by probably late Tertiary pyroclastics. The area was subjected to come pressive orogenic disturbances in middle Cretaceous, upper Cretaceous (Montana), and probably middle Tertiary time, and to the normal faulting of the Basin-Range disturbance in late Tertiary time.