POSSIBLE FAULTING WITHIN AND BOUNDING NORTHERN CROWLEY'S RIDGE, NORTHEAST ARKANSAS

Crowley’s Ridge is a topographic ridge composed of unconsolidated Eocene, Pliocene, and Pleistocene sediment that extends from Helena, Arkansas to Thebes, Illinois. The ridge has been described as an erosional divide separating the Eastern and Western Lowlands of the Mississippi River Valley in Arkansas. However, north-south trending faults have been proposed along the ridge margins based on seismic reflection lines. These previous studies suggest Quaternary uplift due to reactivation of Cambrian Reelfoot Rift faults and uplift of the ridge as a horst block. Based on changes in Pliocene Upland Complex gravel elevations, previous studies have also proposed east-west striking normal faults within Crowley’s Ridge. In this current study, lignite exploration electric and lithologic logs and water well logs were interpreted on and adjacent to the northern half of Crowley’s Ridge, north of Jonesboro, Arkansas. North-south trending cross sections in Greene and Craighead counties indicate east-west trending faults that displace the base of the Upland Complex and underlying Eocene strata. Additionally, east-west trending cross sections in Craighead County reveal displaced Eocene strata across the western ridge margin, which supports tectonic uplift of Crowley’s Ridge.