Structural Aspects of Mid-Continent Rift System in Kansas

Pieter Berendsen, K. David Newell, Kevin P. Blair

The Humboldt fault zone and the faulted Abilene anticline are among many prominent north-northeast to south-southwest-trending structures in northeastern Kansas that occur in Paleozoic rocks as a result of renewed movement of faults associated with the Mid-Continent rift system (MRS). The Humboldt fault zone consists of a number of anastomosing fault segments with high-angle, normal or reverse displacements of up to 600 m. Most of this movement occurred during the Late Mississippian to Early Pennsylvanian. Domal culminations, some of which bear oil, and rhomboid-shaped grabens, are recognized.

Igneous and sedimentary rocks typically associated with the MRS do not occur in a 50 km-wide area in southeastern Nebraska. This area, which also lacks the strong positive geophysical signature characteristic of the MRS, occurs at the intersection of the MRS and a prominent northwest-southeast-trending complex tectonic zone that extends for hundreds of kilometers in each direction. To the south, several other northwest-southeast-trending structures crosscut the MRS. Left-lateral motion affecting rocks as old as the Precambrian is implied. In contrast to the MRS in the northern Mid-Continent, the rift in Kansas displays no central horst composed mostly of mafic igneous rocks.

Stratigraphic information, obtained from three recently drilled wells that penetrate several thousand feet of MRS rocks, in addition to many more drill holes that make shallow penetrations into the basement, indicates that individual fault-bounded basins are probably small, i.e., on the order of tens rather than hundreds of square kilometers.

AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.