Map-scale dextral folds in the footwall of a far traveled crystalline thrust sheet, Alabama-Georgia Appalachians

Conference · Tue Mar 01 04:00:00 EST 1994 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6819380

Tull, J F ^[1]

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1. Florida State Univ., Tallahassee, FL (United States). Dept. of Geology

A series of dextral, map-scale folds occurs in the immediate footwall of both the roof and floor thrusts of the Hollins Line thrust duplex, the boundary between the eastern and western Blue Ridge in Alabama and west Georgia. Spaced between 20 and 60 km along a 150 km fault trace, these folds, which are decapitated by the overlying thrust, consist of anticline-syncline pairs within lower greenschist facies rocks of the structurally uppermost Talladega belt. Synclines occur to the SW of anticlines, generally are cored by Hillabee Greenstone Hillabee Greenstone, and are more open than the paired anticlines which are cored by quartzites of the Butting Ram and Cheah Quartzites and Jemison Chert, and die out structurally downward into the Lay Dam Formation. Short limbs are steep to overturned t the west or northwest and are highly oblique ([approx]90[degree]) to the thrust trace, whereas long limbs are upright and subparallel to the thrust trace. Half wavelengths are 1.5--2 km, and amplitudes are approximately 1 km. Four such fold pairs have been studied: near Wogufka, Chandler Springs, and Pyriton, Alabama and Tallapoosa, Georgia. Folds range from upright shallowly plunging to reclined, and plunge beneath the overlying thrust fault. Two of the fold pairs (Pyriton and Tallapoosa) occur at localities where the fault trace undergoes significant strike changes ([approx]40[degree]) from EW to NE, and these bends correspond to similar changes in strike of footwall stratigraphy. The previously metamorphosed and deformed Talladega belt footwall experienced map-scale dextral shear as the far traveled high-grade eastern Blue Ridge allochthon was emplaced upon it during the Alleghanian. The sole of the terrane boundary thrust is regionally within the Hillabee Greenstone, but heterogeneities caused by the large-scale folds resulted in decapitation of the folds during final nappe emplacement.

• OSTI ID: 6819380
• Report Number(s): CONF-9404221--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 26:4
• Country of Publication: United States
• Language: English

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