--> Abstract: COCORP Studies of Crustal Evolution: The Return to the Midcontinent, by E. C. Hauser; #90987 (1993).

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HAUSER, ERNEST C., and the COCORP Research Group, Institute for the Study of the Continents, Cornell University, Ithaca, NY

ABSTRACT: COCORP Studies of Crustal Evolution: The Return to the Midcontinent

COCORP profiles of the Phanerozoic orogenic belts in the Cordilleria and Appalachians reveal major architectural elements such as thrust detachments and ramps, terrane sutures, extensional detachments, and regional variation in Moho depth and character. In recent years, however, COCORP profiles are increasingly addressing the structure and evolution of the craton 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 for the Phanerozoic intra-cratonic basins and their fundamental mechanisms of formation. COCORP profiles and reprocessed industrial reflection data indicate that large parts of the midcontinent (i.e., s uthern Indiana and Illinois, western Ohio, and southwest Oklahoma and adjacent Texas) are underlain by layered Precambrian rocks that may represent essentially unexplored sedimentary/volcanic sequences. The Grenville Front and its characteristic deeply penetrating zone of E-dipping reflections, as well as structures within the 1.1 Ga Grenville province like the Coshocton Zone, can be correlated over 100s of kilometers. 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 toward or beneath both 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 nort in Canada on new Lithoprobe profiles. It is increasingly clear that major crustal structures and tectonic boundaries are recognizable and traceable for great distances beneath the midcontinent.

Despite these efforts much of the craton remains unexplored. A systematic program of regional deep profiles is needed to identify, characterize, and map the principle crustal components beneath the midcontinent.

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