UMR Journal -- V. H. McNutt Colloquium Series

UMR Journal -- V. H. McNutt Colloquium Series


Frank G. Snyder

Publication Date

01 Apr 1968


Metasediments of Middle Precambrian, and possibly some of earlier age, form an arcuate trending belt across Missouri, Kansas, and Nebraska. These were intruded by granites of several ages that appear to be part of a continuous wave of Late Precambrfan igneous activity. Late Precambrian events that can be delineated include, besides the igneous activity and formation of iron deposits, development of a Keweenawan basin that extended from Lake Superior into eastern Kansas; igneous activity and metamorphism of Grenville age in the eastern Midcontinent; development of a major fault lineament extending northeastward from northeast Arkansas into the Canadian shield outcrop area and separating basement rocks of two distinct ages; and a long period of uplift and erosion during which sediments were deposited in interior and fringing basins.

A belt of volcanic rock, partly preserved as an erosional remnant, extended from Ohio into New Mexico and formed a continental divide during Late Precambrian and Early and Middle Cambrian time. Higher peaks in this belt form the present St. Francois, Eminence, and Spavinaw outcrop areas. This area of high volcanic rock is termed the “Ancestral Ozarks.”

Paleozoic time was a transition from a positive to a negative to a stable area. It began with broad submergence followed by development of domes, arches, and basins. Continued development of lesser arches fragmented the Midcontinent into numerous small basins and highs. The final stage of activity, oscillation and accompanying cyclical sedimentation, was succeeded by stability.

Numerous cryptoexplosion structures are known in the Midcontinent. Some are associated with intrusive and extrusive igneous activity. Nearly all of them lie on a preexisting structural axis.

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