New Geospatial Techniques and Methods Applied to Structural Geology in East-Central Kansas

Abstract

The wealth of previous geological work done in central and eastern Kansas is of immense help in interpreting newly available data such as high-resolution imagery and LiDAR. The surficial geology (easily defined marker beds of white limestone), land cover (grasses), typical land use (mostly untilled), and difficulty in gaining physical access in the Flint Hills of Kansas make this region particularly well suited to investigation through remote means. The study area overlies a complex collection of basement faults. These basement faults have been activated and reactivated in the past due to a variety of tectonic events. The Nemaha Fault Zone is thought to be the result of spreading at the Midcontinent Rift farther to the west. This collection of rhombic basement blocks was reactivated later as terranes collided with the now eastern and southeastern margin of the craton. Forces transmitted across the North American craton by these and other collisions exploited preexisting basement faults. Some of these are extensions of transverse fracture zones extending all the way to the Atlantic Mid-Ocean Ridge. These structures are inferred to account for the Fall River, Chesapeake, Bolivar-Mansfield, and Central Missouri Tectonic Zones among others. The structural anomaly that is Elmdale Dome and its adjacent structures were recognized early in the 20th century. It has been the focus of further study in the time since then. The application of new technology and data to the study of this region in this research has uncovered additional information concerning the bedrock structure of the region. The dipping strata and associated landforms overlying the Humboldt Fault may be easily traced from north-central Oklahoma to the glaciated region of northeastern Kansas. Moderately dipping strata associated with the eastern boundary of the Nemaha Fault, found when mapping strike and dip, or analyzing hillshaded LiDAR, generally match previously mapped subsurface faults. Areas with localized anomalous dips generally overlie recognized structural features. Newly mapped fault trends and lineaments sometimes match recognized basement faults and structures, while some do not. These likely overlie unrecognized basement structures. Oblique movement is recorded in various Riedel trends and associated dipping strata in Chase and surrounding counties. Other fault trends found near basement fault zones appear to be normal in nature. Linear fault zones west of the Humboldt front parallel the orientation of the Humboldt Fault (south-southwest to north-northeast). These are possibly the result of adjustments along backthrusts or reverse faults created by the main thrust of the Nemaha Fault Zone during the active period of the Midcontinent Rift ending ~1.1 Ga. These and other structures were reactivated later during Paleozoic and more recent Laurentian orogenies. It is also likely that displacement along transverse faults associated with seafloor spreading in the Atlantic was transmitted into the cratonic interior during the Mesozoic and Cenozoic. Adjustments along basement structures were broadcast upwards through the sedimentary column. New technology allows for new methods of data collection and visualization in this realm. This trend of improving geospatial data and the accompanying improved possibility for analysis is likely to continue to advance our knowledge of past tectonic events and resulting geologic structures.