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Structural and stratigraphic setting of the Alto Allochthon, Northeast Georgia

Janet L. Hopson and Robert D. Hatcher
Structural and stratigraphic setting of the Alto Allochthon, Northeast Georgia
Geological Society of America Bulletin (March 1988) 100 (3): 339-350


The Alto allochthon is a postmetamorphic crystalline thrust sheet within the metamorphic core of the southern Appalachian orogen. The Toccoa Falls-Shorts Mill thrust fault separates structurally overlying migmatitic sillimanite- bearing Tallulah Falls Formation (?) rocks of the Alto allochthon from upper-greenschist/lower-amphibolite-facies rocks of the Chauga belt. Early D (sub 1) -D (sub 2) structures are truncated by the Toccoa Falls-Shorts Mill fault, suggesting emplacement of the allochthon subsequent to their formation. Later D (sub 4) -D (sub 5) structures appear to postdate thrusting, and the allochthon is preserved in an open F (sub 4) synform. Emplacement of the allochthon was probably coincident with the formation of D (sub 3) structures. Two distinct episodes of mylonitization have affected the rocks of the Alto allochthon. Early middle- to upper-greenschist-facies mylonites are locally developed along the Toccoa Falls-Shorts Mill fault. Along the northwestern margin,these early mylonites are overprinted by a more pervasive episode of lower temperature (lower-greenschist-facies) retrogressive mylonitization associated with deformation within the Brevard fault zone. Lithologic sequences within the Alto allochthon may be correlated with successions in both the eastern Blue Ridge (Tallulah Falls Formation) and the Inner Piedmont. Structural and stratigraphic data suggest that the allochthon is rooted to the southeast in the Inner Piedmont.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 100
Serial Issue: 3
Title: Structural and stratigraphic setting of the Alto Allochthon, Northeast Georgia
Affiliation: Univ. Tenn., Dep. Geol. Sci., Knoxville, TN, United States
Pages: 339-350
Published: 198803
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 55
Accession Number: 1988-019483
Categories: Structural geologyStratigraphyIgneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch maps
N34°15'00" - N34°45'00", W83°45'00" - W83°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1988
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