Chronolithologic units and unconformities in mid-Cretaceous formations of the central Rocky Mountains region indicate widespread marine transgressions and regressions as well as recurrent deformation of the foreland in the Western Interior during Cenomanian, Turonian, and Coniacian time (88-96 m.y. ago). The stratigraphic record of the widely recognized Cenomanian-early Turonian transgression, middle Turonian regression, and late Turonian-Coniacian transgression was modified in several areas by episodes of slight uplift and attendant erosion. The most evident tectonism was in western Montana during middle to late Cenomanian time (93-94 m.y. ago); in western Wyoming and adjoining areas during the early Turonian-earliest middle Turonian (90-91 m.y. ago); in north-central Co orado, eastern Wyoming, and northwestern Wyoming in the early late Turonian (89.8 m.y. ago); and in northeastern Colorado, Wyoming, and southwestern Montana in the late late Turonian (89.3 m.y. ago). Crestlines of most of the swells trend generally either northwest or northeast. The tectonism of the mid-Cretaceous foreland corresponds in age to displacements of thrusts in the Sevier orogenic belt of southwestern Wyoming and southeastern Idaho. Furthermore, much of the foreland deformation probably reflects episodes of eastward thrusting in the thrust belt.