--> Abstract: Analysis of Subsidence Patterns in the Cretaceous Western Interior Basin, USA, by M. Pang; #90987 (1993).

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PANG, MING, Louisiana State University, Baton Rouge, LA

ABSTRACT: Analysis of Subsidence Patterns in the Cretaceous Western Interior Basin, USA

In the past decade, several studies on the subsidence of the Cretaceous Western Interior Basin have revealed that the subsidence patterns deviate substantially from the simple lithospheric flexure under the loading of Sevier thrust belts. Mechanisms proposed to account for the deviations include basement faulting; subcrustal loading and cooling; continental tilting resulting from mantle convection etc.. Because previous works were essentially based on gross lithologic isopach maps, a more precise data base that combines subsurface well logs and the outcrop biostratigraphic data is needed to improve subsidence documentation and to test existing models. This study applies flexural backstripping technique to four regional biostratigraphicaly calibrated cross-sections, located in Montana nd North Dakota, Wyoming, Utah and Colorado, Arizona and New Mexico respectively. Initial results indicate that basin subsidence is the result of superposition of multiple mechanisms and displays great spatial and temporal variability. During the Greenhorn-Carlile cycle (94-90 Ma), subsidence to a great extent was dictated by a flexural pattern attributable to surfacial crustal loading. Thereafter (90-80 Ma), two major anomalous subsidence patterns appeared. One is the long wave-length (600-800 km) flexural pattern. Its broad dimension precludes surfacial crustal loading mechanism, but is compatible with predictions of the continental tilting model. The other is the localized, rapid subsiding loci, or sub-basins, lying beyond the flexural effect of surfacial crustal loading and growing a precursors of Laramide basins, such as Piceance basin and San Juan basin. Coinciding with the areal extent of the later Laramide tectonics, the latter pattern tends to be concentrated in the southern part of the basin, and maybe related with an episode of pre-Laramide faulting.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.