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Seismic imaging of mid-crustal structure beneath central and eastern North America; possibly the elusive Grenville deformation?

Maureen D. Long, Margaret H. Benoit, John C. Aragon and Scott D. King
Seismic imaging of mid-crustal structure beneath central and eastern North America; possibly the elusive Grenville deformation?
Geology (Boulder) (February 2019) 47 (4): 371-374

Abstract

The ca. 1 Ga Grenville orogeny was a protracted mountain-building event that culminated in the collision of Laurentia and Amazonia and the formation of the Rodinia supercontinent. While the expression of Grenville orogenesis in present-day crustal structure has been extensively investigated in eastern Canada, evidence for contemporaneous crustal deformation is less well established beneath the eastern United States. Furthermore, the interpretation of a geophysical lineament through the U.S. midcontinent, typically inferred to be the Grenville deformation front, has recently been called into question; an alternative hypothesis is that this feature actually corresponds to an eastern arm of the Midcontinent Rift. Here we present P-to-S receiver functions computed for stations of the Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) experiment, a dense array of broadband seismometers across the central Appalachians and midcontinent. We see evidence for a crustal negative velocity gradient that dips gently (dip angle <10 degrees ) to the southeast and extends east from a location near the putative Grenville front, terminating near the Appalachian Mountains. While we cannot date this feature, its location and characteristics are consistent with a shallowly dipping, seismically anisotropic intracrustal shear zone associated with collisional deformation, perhaps during Grenville orogenesis. The similarity between this feature and similar mid-crustal detachments in other orogens, both ancient (Appalachians) and modern (Himalayas), suggests that this style of crustal deformation has been common in continental collisional orogens.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 47
Serial Issue: 4
Title: Seismic imaging of mid-crustal structure beneath central and eastern North America; possibly the elusive Grenville deformation?
Affiliation: Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Pages: 371-374
Published: 20190228
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 22
Accession Number: 2019-024200
Categories: Solid-earth geophysicsApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019127
Illustration Description: illus. incl. geol. sketch maps
Secondary Affiliation: National Science Foundation, USA, United StatesVirginia Polytechnic Institute and State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201914
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