Plains-type Folds: Their Origin and Development

Small in areal extent, plains-type folds in Paleozoic sediments of the Midcontinent of the United States form by as the result of draping sediments over highs in underlying Precambrian crystalline basement rocks. Fracture systems in underlying Precambrian rocks may propagate upward through overlying sedimentary rocks. Movement on the basement structures occur when there is an adjustment in the basement, which results in an adjustment of the overlying units and a draping over the tilted fault blocks. The incidence of earthquakes, which result from this adjustment, are recorded in the overlying sediment as convolute features known as seismites