Variations in the reflectivity of the moho transition zone beneath the Midcontinent Rift System of North America: results from true amplitude analysis of GLIMPCE data

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

True amplitude processing of The Great Lakes International Multidisciplinary Program on Crustal Evolution seismic reflection data from the Midcontinent Rift System of North America shows large differences in the reflectivity of the Moho transition zone beneath the axial rift, beneath the rift flanks, and outside of the rift. The Moho reflection from the axial rift has a discontinuous, diffractive character marginally stronger (several decibels) than an otherwise transparent lower crust and upper mantle. Beneath the axial rift, Moho is interpreted to be a synrift igneous feature. Beneath the rift flanks, the reflectivity of the Moho transition is generally well developed with two identifiable boundaries, although in places it is weakly reflective to nonreflective, similar to Moho outside the rift. The two boundaries are interpreted as the base of essentially intact, although stretched, prerift Archean crust (upper boundary) and new synrift Moho 1-2 s (6-7 km) deeper (lower boundary). Beneath the rift flanks, the layered reflection Moho transition results from the preexisting crustal composition and fabric modified by synrift igneous processes and extensional tectonic/metamorphic processes. The geologic evidence for extensive basaltic magmatism in the rift is the basis for interpreting the Moho signature as a Keweenawan structure that has been preserved for 1.1 b.y. Extension and magmatism appear to enhance reflectivity in the lower crust and Moho transition zone only where stretching factors are moderate (rift flanks) and not where they are extreme (axial rift). This leads to the prediction that the reflectivity across analogous volcanic passive continental margins should be greatest beneath the moderately stretched continental shelves and should decrease towards the ocean-continent boundary.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Variations in the reflectivity of the moho transition zone beneath the Midcontinent Rift System of North America: results from true amplitude analysis of GLIMPCE data
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/91JB02572
Volume 97
Issue B4
Year Published 1992
Language English
Publisher American Geophysical Union
Publisher location Richmond, VA
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 17 p.
First page 4721
Last page 4737
Country United States
Online Only (Y/N) N
Additional Online Files (Y/N) N