Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associatedwith the Midcontinent Rift System. Strategic and Critical Minerals in the Midcontinent Region, United States (Chapter E)

摘要

Rocks from exposures in the Lake Superior region and from core and cuttings ofexploration drill holes in Iowa, Nebraska, and Kansas were analyzed to correlate the subsurface clastic sedimentary rocks in the southern extension of the Midcontinent Rift System with rocks of the established Keweenawan stratigraphy in the Lake Superior region. Petrographic properties and heavy minerals were used to characterize the various formations. Rocks similar in character to those of the Oronto Group and the Bayfield Group are recognized in the subsurface in Iowa, Nebraska, and Kansas.