Late to Post-Appalachian Strain Partitioning and Extension in the Blue Ridge of Alabama and Georgia
Late to post-Appalachian strain partitioning and extension in the Blue Ridge of Alabama and Georgia Mark G. Steltenpohl1, Joshua J. Schwartz2, and B.V. Miller3 1Department of Geology and Geography, Auburn University, Auburn, Alabama 36849, USA 2Department of Geological Sciences, California State University, Northridge, Northridge, California, 91330, USA 3Department of Geology & Geophysics, Texas A&M University, College Station, Texas 77843-3115, USA ABSTRACT margin, possibly refl ecting its reactivation its position far toward the foreland. Loose during Mesozoic rifting of Pangea. timing constraints for this extensional event Structural observations and U-Pb and The Alexander City fault zone is a middle (late Carboniferous to Early Jurassic) leave 40Ar/39Ar isotopic age dates are reported greenschist facies, dextral strike-slip fault room for several tectonic explanations, but for shear zones and metamorphic rocks in rather than a west-vergent thrust fault, as we favor the following. (1) Late Pennsyl- the southernmost Appalachian Blue Ridge. was previously thought. This fault zone is vanian to Early Permian crustal thickening Two major mylonite zones, the Goodwater- obliquely cut and extended by more east- created a wedge of Blue Ridge rocks bound Enitachopco and Alexander City fault zones, trending, subvertical, cataclastic faults above by the Good water-Enitachopco, have retrograded peak amphibolite facies fab- (Mesozoic?) characterized by intense quartz below by the décollement, and to the north- rics and assemblages in rocks of the ancient veining. These brittle faults resemble those west (present-day direction) by a topograph- Laurentian margin. Both faults are within in other parts of the Blue Ridge, Inner ically steep mountain front.
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