The Role of Recurrent Tectonics in the Formation of the Nemaha Uplift and Cherokee-Forest City Basins and Adjacent Structural Features in Eastern Kansas and Contiguous States, USA

Abstract

We elaborate on an old hypothesis suggesting that once the early-formed crust of the Earth attained sufficient buoyancy, thickness, and strength to react in brittle fashion, it was broken into semi-rectangular blocks by tensional stresses, perhaps associated with development of its equatorial oblateness. The roughly orthogonal fractures bounding the crustal blocks are spaced more or less evenly by dissipation of stresses between adjacent megafractures, depending upon the strength of the local crust. We further propose that once the primordial crust was broken, the fractures became the loci of stress relief for whatever combinations of horizontal, vertical, and shear stresses acting on them throughout geologic time. Because the through-crustal fractures (including the outlines of meteorite impact craters of whatever age) continue to be active, they propagate upwards to the present surface through succeeding layers and are manifested by stream patterns which reflect faults, flexures, and joints; outcrop anomalies; and even subtle tonal changes on remotely-sensed images. Examples are the Chesapeake, Bolivar-Mansfield faults, (Wilson and McCauley, 1989) which have been mapped in Missouri and are traced on trend into the Kansas subsurface by means of major stream lineaments or divides and other more subtle features. Other northwest- and northeast-trending structural zones are likewise recognized (Blair and others, 1992). The pattern or mapped faults and the interpretation of stream patterns suggests that many are wrench faults, and reversed movement at various times depending on the direction of applied horizontal compressive stresses and the orientation of the resisting or passive blocks. We postulate that the stresses originated at the eastern margins of the North American craton during continent-continent collisions beginning during Grenvillian or earlier times, and continued during the Taconian, Acadian, Appalachian-Alleghenian. Major episodes affected the midcontinent during the Ouachitan-Wichitan-Marathon orogenies, and with somewhat lesser effects during later geologic times to the present. The stresses are assumed to have been transmitted primarily via Precambrian basement rocks and the overlying Cambro-Ordovician through Mississippian carbonate rocks.