Northwest- and northeast-trending faults characterize the structural grain of the pre-Paleozoic basement in the Midcontinent. Northwest-trending faults associated with the Central Plains Orogen and the younger granite-rhyolite terrane to the south predate the northeast-trending set of faults related to the development of the 1.1 Ma Midcontinent Rift System.
Precambrian compound vertical displacement of at least several thousand feet is evident from the preservation of younger rocks in grabens or fault-bounded basins in older terranes. Several periods of reactivation can be demonstrated to have occurred in the Paleozoic. Subtle changes in morphology across linear trends known to coincide with tectonic zones mapped in the subsurface are believed to reflect neotectonic activity. The same is true for linear trends of rivers and streams, as well as contacts between geologic formations.
Much of this activity can be related to periodic stress buildup associated with orogenic activity along the margins of the craton. The loci for the release of horizontal, vertical and shear stresses are likely to be preexisting faults. Recurrent activity, coupled with changes in direction of the stress fields tend to give rise to complex fault systems, more properly referred to as tectonic zones. Interpretation of recurrent activity is a difficult task, because present-day fault configurations exhibit compound movement over time.
Kansas Geological Survey
Updated April 17, 1997
URL="http://www.kgs.ku.edu/Conferences/GSA96/berendsen.html"
Send comments and/or suggestions to
webadmin@kgs.ku.edu