Print this pageABSTRACT: Cretaceous Strata of the Gunnison and Wasatch Plateaus, Central Utah
T. F. Lawton, K. J. Franczyk, P. Schwans, M. P. Weiss
Cretaceous strata of the Gunnison and Wasatch plateaus preserve a record of foreland sedimentation in response to thrust tectonism. Thrust deformation of the most proximal part of the foreland basin and thick wedges of nonmarine sediment render correlations within the region somewhat uncertain. In general, Aptian(?) through upper Campanian foreland-basin strata thin and fine eastward; an increase in the number of marine intervals eastward within the Wasatch Plateau demonstrates the westward extent of the Late Cretaceous sea. Upper Campanian and Maastrichtian strata were deposited in intermontane basins created by thrust-induced uplifts and the San Rafael uplift; units in these basins lack systematic regional geographic trends.
Strata of the western part of the foreland basin include the Aptian-Albian Cedar Mountain (or lower member of Pigeon Creek) Formation and Cenomanian-Campanian(?) Indianola Group (which includes the upper member of the Pigeon Creek Formation). This concordant section is in excess of 3000 m thick. Equivalents in the Wasatch Plateau include the Cedar Mountain Formation and the Indianola Group, which grades eastward into the Dakota Sandstone, Mancos Shale, and Mesaverde Group, in ascending order. The section in the Wasatch Plateau is about 3000 m thick.
The North Horn Formation unconformably overlies Indianola and Mesaverde strata, but occupies localized depocenters bounded by ramp anticlines and duplex structures. The age of the basal North Horn in the Wasatch Plateau is Maastrichtian; basal North Horn Strata in the Gunnison Plateau may include rocks of late Campanian age. The basal
contact of the North Horn is locally concordant in basin centers, but discordant at the margins of the intermontane basins. North Horn strata range from 0 to 700 m thick in the region.
AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990