Model of the midcontinent rift system in northeastern Kansas

Recent drilling of the midcontinent rift system in northeastern Kansas reveals a transposed Keweenawan stratigraphy of mafic volcanic rocks overlying thick elastic sedimentary rocks. A reprocessed version of COCORP Kansas Line 1 indicates that the drillhole penetrated a series of west-dipping reflectors associated with a reverse fault bounding the east side of the rift basin. Reanalysis of the original COCORP line also reveals a west-bounding reverse fault and evidence of crustal thickening. This information is integrated with gravity and magnetic data to define a model of the rift in northeastern Kansas. The model, consisting of an asymmetric basin bounded by reverse faults with thickened crust beneath the rift, is similar to models proposed for northern segments of the rift system, and argues for homogeneity in the structural style and tectonic evolution along the length of the rift.