Basement Tectonic Configuration in Kansas
Abstract
The structure of the Precambrian basement of Kansas, midcontinent USA, is dominated by conjugate north-northeast- and northwest-trending wrench fault zones. North-northeast-trending faults of the Midcontinent Rift System (MRS) extend from Lake Superior across Kansas and into north-central Oklahoma. The fault zone widens from about 100 km (60 mi) in northeast Kansas to more than 160 km (96 mi) in south-central Kansas in a series of horsetail splays. North-northeast-trending structures of the MRS are displaced by about 80 km (48 mi) of dextral offset by the northwest-trending strike-slip fault zone.
Apparently penecontemporaneous northwest-trending wrench faults of the Bourbon ArchCentral Kansas uplift cross the state from southeast to northwest, offsetting MRS structures. The two conjugate wrench fault zones are complexly interrelated in central Kansas, where internal synthetic shears complicate axial horsts and grabens of the MRS. The Bourbon Arch is offset approximately 100 km (60 mi) by sinistral slip from the Central Kansas uplift along the MRS. The Humboldt fault zone at the eastern margin of the MRS was not offset significantly by northwest-trending faults, suggesting that the present-day expression of the southward-weakening fault zone was created during Pennsylvanian (Upper Carboniferous) rejuvenation of the basement fabric. Stratigraphic relationships record a history of repeated reactivation in Paleozoic time that strongly affected petroleum entrapment, with an especially strong pulse of uplift during Pennsylvanian time.
These rift zones are segments of continental-scale basement lineaments that are fundamental to the structural fabric of the North American basement. The Bourbon Arch-Central Kansas structural lane lies sub-parallel to the Olympic-Wichita lane that extends from southern Oklahoma to the northwest through the Paradox basin of eastern Utah, and the MRS lies sub-parallel to the Colorado Lineament which extends from the Grand Canyon in Arizona to the Lake Superior region. Thus, the basement of the western midcontinent and southern Rocky Mountains consists of large-scale fault zones that delineate suborthogonal basement blocks.
