Project CRATON: A Multi-Discipline Study of the U.S. Continental Interior

Ernest C. Hauser

COCORP, Lithoprobe, and other deep reflection profiles over the past several years have explored significant parts of the Cordillerian and Appalachian orogenic belts of North America, and have made important contributions to understanding crustal evolution and the architecture of these Phanerozoic orogens. In contrast, large parts of the U.S. midcontinent basement remain unexplored beneath the masking veneer of Phanerozoic strata. Some features of the midcontinent have locally been studied intently, such as the Keweenawan Rift beneath Lake Superior as revealed on GLIMPCE profiles; however, the basement structures associated with accretion and stabilization of Precambrian continental crust, as well as the structural underpinnings of the Phanerozoic intra-cratonic basins an their fundamental mechanisms of formation, are not known. The role of basement reactivation, if any, in the formation and evolution of intracratonic basins and other structures in the Phanerozoic rocks is commonly debated; but, without substantive in formation about the structure and evolution of the continental crust beneath, such debate is largely pedantic. Project CRATON addresses this fundamental lack of knowledge by both compiling/reanalyzing existing data sets and collecting new geological and geophysical data along strategic transects of the U.S. midcontinent, cored by new deep seismic profiles.

COCORP profiles, together with reprocessed industrial reflection data, already have begun to reveal important structural features that lie hidden beneath the midcontinent. 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 represent unexplored sedimentary/volcanic sequences. The extent, nature, and correlation of these sequences, however, remains to be resolved. Also, existing data reveal the clear potential for identifying and mapping major crustal structures and tectonic boundaries across the region. The Grenville Front and its characteristic deeply penetrating zone of dipping reflections can be correlated over 100's of kilometers on COCORP and GLIMPCE dat . COCORP profiles in eastern Montana and North Dakota across the Williston Basin and the underlying early Proterozoic Trans-Hudson orogen reveal a crustal-scale structure that is remarkably similar to that observed across this orogen farther north in Canada on LITHOPROBE profiles.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995