Geology And Mineral Deposits Of The 0zark Region

LOCATION THE Ozark region occupies a large part of the southern half, of Missouri, the northern portion of Arkansas and comparatively small areas in northeast Oklahoma, southwest Kansas, and southern Illinois. . It is a roughly elliptical plateau which has been deeply dissected by stream erosion, and which slopes imperceptibly into the prairie regions to the north, east, and west, but which terminates rather abruptly along the Arkansas River on the south and Tertiary lowland to the southeast. The-Boston Mountains extending for a distance of some 200 miles (321 -km.) along the Arkansas River rise to an elevation of 2000 ft. (609 m.), forming the most prominent topographic feature of the region. The so-called St. Francois Mountains in St. Francois, Madison, and adjoining counties in southeast Missouri, form a prominent but more restricted topographic feature, the highest point rising to an elevation of 1800 ft. (548 m.).. The remainder of the region is largely a plateau area varying from 800 to 1500 ft. (243 to 457 m.) in elevation. STRATIGRAPHY The region is underlain chiefly by sedimentary formations, which outcrop in roughly concentric bands around a comparatively restricted area of igneous rocks in the St. Francois Mountain district. Although located geographically near the eastern edge of the Ozarks, the St. Francois Mountains have apparently suffered the greatest orogenic movement and the lowest formations of the succession are exposed in their immediate vicinity. The various sedimentary formations of the region do not show any considerable metamorphism and have suffered little change since consolidation. With the exception of a few basic intrusions in Ste. Genevieve County and a pegmatite dike in Camden County, Missouri, there is no evidence of igneous-action, since the first sedimentary beds were deposited.