Southeastern Section - 60th Annual Meeting (23–25 March 2011)

Paper No. 3
Presentation Time: 8:00 AM-12:00 PM


SAYERS, Jordan E., Department of Geology and Geography, Auburn University, 210 Petrie Hall, Auburn, AL 36849, UDDIN, Ashraf, Department of Geosciences, Auburn University, 210 Petrie Hall, Auburn, AL 36849 and SITAULA, Raju P., Geology and Geological Engineering, Colorado School of Mines, Golden, CO 80401,

The Tuscaloosa Formation (8 to 80m) is composed primarily of poorly sorted, fine to coarse grained, and massive to cross-bedded sandstones. Sands of the Tuscaloosa Formation are primarily sublitharenite but can range between subarkose and lithic subarkose, and plot in the “recycled orogenic” provenance field of Dickinson (1985). This study deals with whole-rock chemical analysis of the Tuscaloosa sands in order to trace their provenance.

Geochemical studies comprising eight major elements, sixteen trace elements, and fifteen rare earth elements have been carried out on the sandstones. Concentrations normalized to Post Archean Australian Shale (PAAS) show that the sediments studied are depleted in Ca, Na, Sr, Cs, and Cu and enriched in Nb and Al­2O3. PAAS-normalized values for all 8 samples are very similar, probably because this relatively small study area had common felsic source areas.

Several discrimination diagrams such as log(SiO2/ Al­2O3) vs log(Na2O/K2O), Zr (ppm) vs TiO2 (wt%), Zr/Sc vs Th/Sc, and La/Th vs Hf indicate a felsic source rock. The Hf vs La/Th pattern indicates a felsic island arc to passive margin environment, while the abundance of SiO2 to K2O/Na2O indicates a passive margin setup.

The chemical index of alteration (CIA) has been used to quantify the degree of weathering. CIA values range between 81 and 97 on a scale of 50-100, indicating a high degree of alteration. On an A-CN-K diagram, the data fall closer to the compositional fields of highly weathered minerals. A high degree of weathering is also indicated by the K2O-Fe2O3-Al2O3 plot.

This study, along with ongoing petrographic analyses, suggests that the source area was geographically close and was likely the upper-grade metamorphic, felsic plutonic, and meta-sedimentary sequences of the Inner Piedmont of the southern Appalachians.