Crustal Structure at the southern Terminus of the Blytheville Arch, Eastern Arkansas

Cao, J. and Langston, C. A, VanArsdale, R., Center for Earthquake Research and Information, Department of Earth Science, University of Memphis, 3876 Central Ave., Suite 1, Memphis, TN 38152, juancao@memphis.edu

Line 61W from reflection vibroseis data acquired in the Mississippi Embayment in the early 1980’s by the Dow Chemical Company has been reprocessed to reveal crustal reflectivity in the upper and lower crust near the southern terminus of the Blytheville Arch. All of the data are 24-fold vibroseis deep seismic reflection data collected by a 48-channel recording system. The 2D common midpoint stacking technique is used in this work. Seismic Unix developed by Colorado School of Mines is applied for data processing. A velocity log of Dow Wilson well #1 was combined with the refraction velocity model developed by Mooney et al. (1982) to conduct velocity analysis to yield the final stack. The stratigraphic units were correlated with seismic reflections and prominent reflectors include: the contact of the upper Cretaceous in the unconsolidated sediments with more indurated Paleozoic sediments; the presumed base of the Paleozoic and crystalline basement contact; a “transparent” upper crustal zone from 3-9 second two-way travel time; and a highly reflective lower crust from 9-14 seconds two-way travel time (to the end of available record). The highly reflective lower crust starts near 24 kilometers in depth corresponding to the high-velocity region imaged by Mooney and others (Mooney et al. 1982).