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2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 63
Presentation Time: 8:00 AM-12:00 PM

A NEW VIEW OF UPPER CRUSTAL STRUCTURE AT THE CORNER OF THE ALABAMA PROMONTORY BASED ON DIGITALLY ENHANCED REGIONAL MAGNETIC AND GRAVITY DATA


STELTENPOHL, Mark G.1, DANIELS, David L.2, HATCHER Jr, Robert D.3, HIGGINS, Michael W.4, HORTON, J. Wright5, ZIETZ, Isidore2 and SAVRDA, Amanda M.1, (1)Department of Geology and Geography, Auburn Univ, Petrie Hall, Auburn, AL 36849, (2)U.S. Geological Survey, 954 National Center, Reston, VA 20192, (3)Earth and Planetary Sciences, University of Tennessee, 1412 Circle Park Dr, Knoxville, TN 37996, (4)The Geologic Mapping Institute, 1752 Timber Bluff Drive, Clayton, GA 30525-6011, (5)U.S. Geological Survey, 926A National Center, Reston, VA 20192, steltmg@auburn.edu

Digital compilation, filtering, and innovative map displays of regional magnetic and gravity data reveal crustal structure at the corner of the Alabama promontory in ways not possible before. Aeromagnetic and gravity data were merged and digitally filtered to enhance anomalies caused by upper crustal features. Contours, shaded relief, and color are used to accentuate regional patterns of highs, lows, gradients, and lineaments simultaneously. Broad deep-crustal anomalies of the continental interior, possibly including the Grenville front, occur in NW Alabama. The New York-Alabama lineament is the eastern boundary of a buried crustal block with NE-trending magnetic highs and gravity lows that trace into central Alabama. Broad magnetic anomalies underlie regions covered by Paleozoic and Coastal Plain sedimentary rocks, and by thinner parts of the Blue Ridge-Piedmont megathrust sheet. High-frequency magnetic anomalies superposed on broad, low-amplitude anomalies result from magnetic amphibolites and mylonites exposed in the Piedmont, outlining terranes and structures of the Appalachian orogen (AO). Clear magnetic distinction exists between AO crust and strongly linear, high-frequency magnetic highs of the peri-Gondwanan (pG) Uchee terrane. These anomalies correspond to the Bartletts Ferry/Goat Rock fault zones, interpreted as the ‘suture' between the AO and the collage of pG terranes of the Carolina superterrane. Magnetic and gravity signatures for the Laurentian margin and the AO are sharply truncated by the subsurface, east-west trending Altamaha magnetic low anomaly associated with the Suwannee suture. Along the southern boundary of the AO, high-frequency linear magnetic anomalies of the pG rocks are swept asymptotically (dextrally) into parallelism with the Altmaha anomaly. The Gondwanan Suwannee terrane contains distinct, parallel, arcuate, 045, linear magnetic anomalies that reflect internal lithologic structure and superposed Mesozoic failed-rift trends.

Session No. 83--Booth# 103

Structural Geology and Tectonics (Posters)
Monday, 29 October 2007: 8:00 AM-12:00 PM
Geological Society of America Abstracts with Programs. Vol. 39, No. 6, p.233
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