Title

A Shallow High-Resolution Seismic Reflection Study of Dudley Ridge, South-East Missouri

Abstract

Dudley Ridge is an arcuate, north-trending terrace remnant of Wisconsinan (late Quaternary) outwash in the Western Lowlands of southeast Missouri. The ridge, an elongate topographic bulge, is approximately 12 km long and 2 km wide with up to 5 m of relief. Previous workers have attributed the ridge to fluvial erosion, or to a combination of fluvial erosion and tectonic deformation during the late Quaternary. The Commerce geophysical lineament, which is a major northeast-trending basement feature, is located a few kilometers to the southeast, and swarms of paleoliquefaction and possible neotectonic deformations have been reported in nearby areas of the Western Lowlands. To test the tectonic hypothesis, in 1994 and 1995 we acquired two west-east high-resolution seismic reflection profiles along the crest and western flank of Dudley Ridge to determine whether Paleozoic, Cretaceous and shallow Quaternary strata are faulted or folded. Profile SPB-1 shows several near-vertical faults indicative of at least three periods of movement: Paleozoic to middle Mesozoic; late Cretaceous to Tertiary; and early to late Wisconsinan (late Quaternary). Profile SPB-2 shows three ambiguous fault-like features which cut Cretaceous and Quaternary reflectors, but cannot be interpreted unequivocally to extend down into the Paleozoic section. These new seismic reflection data are interpreted to show that at least three major periods of faulting have disrupted Paleozoic, Cretaceous and Quaternary strata beneath Dudley Ridge, with the most recent faulting being early to late Wisconsinan in age and producing about 6-8 m (8-10 ms) of near-vertical displacement. Because Quaternary reflectors cannot be resolved above about 30-40 ms, the seismic data alone do not reveal whether or not the Wisconsinan deformation affected the surface of Dudley Ridge or whether the faults may have died out as they propagated up through the soft, saturated Wisconsinan outwash. However, the presence of the Farmdale Geosol beneath lower terraces adjacent to Dudley Ridge and the geosol's apparent absence, or near-total truncation, beneath modern soils on Dudley Ridge suggest that one or more periods of tectonic bulging and accelerated erosion may have occurred between the Farmdale Interstadial and the Holocene about 25,000-10,000 years before present.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

New Madrid; Quaternary; Reflection Seismic; Neotectonics; Seismic Survey; USA, Missouri

Geographic Coverage

Southeast Missouri

International Standard Serial Number (ISSN)

983004

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1997 Elsevier Limited, All rights reserved.

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