Abstract

Five high resolution seismic reflection lines (24 channel Mini-Sosie data with 1 s record length) were acquired across the margins of Crowley’s Ridge in northeast Arkansas during the summer of 1990 to test the hypothesis that Crowley’s Ridge is fault bounded. Three of the lines traversed the margins of the northern segment of the ridge near Jonesboro, Arkansas, and the other two were located south of Jonesboro across the margins of the southern segment. All five lines revealed subsurface faulting of the Paleozoic through Eocene (Wilcox) sections beneath the ridge margins. The data did not resolve the uppermost 0.1 s of two way travel time so it is not possible to determine if the Pliocene and younger sediments have been faulted. Thus, we can not determine if the ridge truly owes its topographic relief to fault displacement or if Tertiary faulting controlled subsequent Quaternary river incision. At one site, however, it does appear that the ridge margin is a fault scarp because the ridge height is the same as the structural relief on the ridge-bounding fault and fault displacement can be traced into the shallowest reflectors (0.15 s).

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