Abstract

We analyzed drainage-basin geometry in part of the southeastern Mississippi Embayment near the New Madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism. Toward this goal, a field of drainage-basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure, lithofacies, seismicity, remotely sensed lineaments, and major drainage divides.

Transverse topographical drainage-basin asymmetry (T-index) results define geomorphic domains in northern Mississippi (33° to 35°N, 88.5° to 90.25°W) that may reflect deep crustal blocks bounded by active faults or flexures. T-index measurements (a proxy for lateral stream migration) of more than 4500 second-order drainage basins produced a two-dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains. Some domain boundaries correspond to mapped faults of two Paleozoic fault systems in our study area, the northeast-striking Mississippi Valley graben system and the northwest-striking Ouachita thrust belt and foreland faults. Several other prominent domain boundaries may be previously unmapped faults (flexures?) parallel to these systems. This interpretation is supported by satellite image analysis of the northeastern study area, which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain.

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