Abstract: COCORP Studies of Continental Evolution: Project CRATON

Ernest C. Hauser

COCORP deep-reflection profiles over the past several years have explored significant parts of the Cordilleran and Appalachian orogenic belts, and have made important contributions to understanding crustal evolution and the architecture of these Phanerozoic orogens. In recent years, however, COCORP profiles have increasingly addressed the structure and evolution of the continental crust hidden beneath the Phanerozoic platform cover of the U.S. midcontinent, both to identify the structures associated with accretion and stabilization of Precambrian continental crust and to explore the structural underpinnings of the Phanerozoic intra-cratonic basins and their fundamental mechanisms of formation.

Although large parts of the U.S. midcontinent basement are still unexplored, COCORP profiles, together with reprocessed industrial reflection data, already have begun to reveal important aspects of the hidden structural elements. It is clear that large parts of the midcontinent (i.e., southern Indiana and Illinois, southwestern Ohio, and southwest Oklahoma and adjacent Texas) are underlain by layered Precambrian rocks that may represent essentially unexplored sedimentary/volcanic sequences; however, the extent, nature, and correlation of these sequences remains to be resolved. In addition, major crustal structures and tectonic boundaries are increasingly recognized on deep reflection data and traceable for great distances beneath the midcontinent. For example, in the eastern U.S. the renville Front and its characteristic deeply penetrating zone of dipping reflections can be correlated over 100s of kilometers on COCORP and GLIMPCE data. Also, new COCORP profiles across the Williston basin and early Proterozoic Trans-Hudson orogen beneath eastern Montana and North Dakota reveal an arched zone of crustal-scale reflections that dip beneath the Archean Wyoming and Superior provinces to the west and east, a pattern that is remarkably similar to that observed across the Trans-Hudson orogen farther north in Canada on new LITHOPROBE profiles.

Large parts of the continental interior, however, remain unexplored. To provide a basis for understanding crustal evolution and resource potential a systematic and multidisciplinary program of regional crustal transects, Project CRATON, cored by deep reflection profiles, is needed to identify, characterize, and map the principle crustal components beneath the midcontinent.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994