Fracture orientations in Kansas and relations to mountain building

Abstract

In efforts to discern the space-time relationships between fracture formation [low-strain brittle deformation in the Earth's upper crust] and other geologic structures [folds and faults] in the mid-Continent region, field studies were carried out in upper Paleozoic to late Mesozoic deep-marine sedimentary rocks exposed across portions of western, south-central, and northeastern Kansas. Fracture orientations were measured, plotted stereographically, and analyzed for 30 different locations. Two subvertical, systematic fracture sets emerged from our data: NE and NW striking joints or extensional fractures. Fracture orientations are oblique to major subsurface deformation belts such as the Central Kansas uplift, Nemaha uplift, Humboldt Fault system, as well as the Augusta North anticline. If tectonic in origin, then fracture sets across much of Kansas may relate to formation of the Rocky Mountains [Laramide orogeny].