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Impact breccias in carbonate rocks, Sierra Madera, Texas

H. G. Wilshire, Keith A. Howard and T. W. Offield
Impact breccias in carbonate rocks, Sierra Madera, Texas
Geological Society of America Bulletin (1971) 82 (4): 1009-1017


Two main types of deformational breccia occur in the Sierra Madera cryptoexplosion structure: monolithologic breccias composed of shattered rock of a single lithology and mixed breccias composed of rocks of several lithologies. Monolithologic breccias generally show no mineralogic signs of shock deformation, but a few samples are shatter-coned in a manner suggesting simultaneous formation of breccias and shatter cones. Mixed breccias, forming irregular, cross-cutting bodies, consistently contain moderately to highly shocked material, with mineralogic evidence of shock pressures of 50 kb to more than 200 kb, which, with evidence from the structural geometry of Sierra Madera and orientation of shatter cones, indicate an impact origin of the breccias.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 82
Serial Issue: 4
Title: Impact breccias in carbonate rocks, Sierra Madera, Texas
Pages: 1009-1017
Published: 1971
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1971-017265
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. (incl. sketch maps)
N29°40'00" - N30°45'00", W102°34'60" - W100°19'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 1971
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