Regional Cretaceous Stratigraphic Relationships across the Southern Segment of the Western Interior Basin, Arizona, New Mexico, and Southern Colorado

MOLENAAR, C. M., W. A. COBBAN, K. J. FRANCZYK, C. L. PILLMORE, and R. S. ZECH, U.S. Geological Survey, Denver, CO, E. G. KAUFFMAN, University of Colorado, Boulder, CO, J. M. HOLBROOK, Indiana University, Bloomington, IN, and D. G. WOLFE, San Jose, CA

Cretaceous strata in Arizona, New Mexico, and southern Colorado were deposited in the southern part of the asymmetric Western Interior basin and consist of east- and northeastward-prograding clastic wedges of shoreface sandstones and coastal-plain deposits separated by thick tongues of west- and southwestward-extending marine shale and, on the eastern shelf, by limestone. The interlayering of the two primary facies (sandstone and shale) is the result of either regional subsidence,

eustasy, sediment supply, or a combination of these. Constructing and comparing regional cross sections will aid in accomplishing one of the goals of the Western Interior Cretaceous (WIK) project of the International Union of Geological Science's Global Sedimentary Geology Program, which is to identify the global effects of eustasy.

Preserved Cretaceous strata in this part of the Western Interior basin range from a few hundred feet thick on the east to about 7000 ft on the west. A cross section across this area reveals facies relations, major sequence boundaries, unconformities, and available biostratigraphic and chronostratigraphic data for the sections preserved in the present Laramide basins. Sequence boundaries occur in the middle late Albian, at the base of the late Turonian, and within the latest Turonian. Younger sequence boundaries, if present, are less obvious, and their associated unconformities have not been identified.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)