THE ORIGIN OF CROWLEYS-RIDGE, NORTHEASTERN ARKANSAS - EROSIONAL REMNANT OR TECTONIC UPLIFT

The geomorphology of Crowley's Ridge, apparent Quaternary reactivation of the ridge-bounding faults, and orientation of the faults to the pr esent stress field suggest that the faults bounding Crowley's Ridge an d the western margin of the Reelfoot rift may be seismogenic. Fifteen high-resolution seismic reflection lines were acquired across and adja cent to the margins of Crowley's Ridge to test the hypothesis that Cro wley's Ridge is fault bounded. Eleven of the reflection lines were 24- channel Mini-Sosie data with 1-sec record length and four lines were 2 4-channel shotgun-source data with 0.25-sec record length. Nine lines traversed the margins and adjacent areas of the northern segment of th e ridge near Jonesboro, Arkansas, and the other six were located south of Jonesboro on the southern segment. The reflection data show that P aleozoic through Eocene Wilcox sections have been uplifted beneath Cro wley's Ridge from 60 to 30 m across ridge-bounding faults. However, Eo cene or Pliocene-Pleistocene near-surface strata appear to be displace d a maximum of 7.5 m. Based on reflection and geomorphologic data, we believe that reactivation of the bounding faults of Crowley's Ridge oc curred concurrently with and strongly influenced Wisconsin denudation of the Mississippi valley.