This project was designed to test existing proposals for the ages of two prominent granitic gneisses in the southern Appalachian Piedmont Province, typically referred to as the Zana granite and Kowaliga gneiss.  The project was developed as a collaborative effort between the University of Florida and Columbus State University (GA) and funded via RUI awards (Research in Undergraduate Institutions) to each institution.   Students from Columbus State (CSU) worked primarily on field and petrographic aspects of the project.  This work entailed mapping of outcrops, sampling of outcrops for petrographic and geochemical analyses, and presenting results at professional scientific meetings.  The samples collected for geochemical, including geochronologic, analyses were then transferred to the University of Florida (UFL) for processing.  Once sample processing and analyses were underway, students from CSU visited the UFL labs and were able to assist with, and participate in, various aspects of sample preparation and analysis.  One CSU student from the first year was sufficiently interested in the geochemical side of the project that he enrolled in the graduate program at UFL and graduated with an MS degree.  The project met its goals of involvement and training of CSU undergraduate geology students in geochemical methods not available to them at CSU.

Scientifically, the project was successful. We completed elemental, isotopic, and geochronologic analyses of all samples collected from the mapped exposures of the Kowaliga gneiss and Zana granite, including sites most commonly used for field trips by a range of organizations.  We also tested correlations of nearby Piedmont granitoids also proposed as Ordovician to enhance our understanding of the tectonic regime in which the Kowaliga and Zana were generated.  Elemental (major and trace), isotopic (Nd, Pb, Hf), and geochronologic (U-Pb zircon) analyses were carried out on these samples as well.  U-Pb analyses of zircon for all samples were carried out using the laser ablation ICP-MS technique to analyze specific domains within each zircon.  Even with this level of detailed sampling, many zircons yielded discordant data (the two U-Pb ages from a single analysis differed by more than analytical error).  This discordance hindered determination of highly precise ages for some samples.  Nonetheless, it is clear that the Zana and Kowaliga map units were emplaced in the Ordovician Period in a narrow window of time ~450 million years ago during the Taconic orogeny.  In addition, we also sampled and studied nearby granitoids proposed to be of Ordovician age (Camp Hill and Chattasofka Creek granitoids of the adjacent Dadeville complex) and the Elkahatchee quartz diorite (the largest batholith in the southern Appalachians), both having been proposed as correlative with the Zana and Kowaliga.  The Dadeville granitoids were added to the study because they are intimately associated with a large volume of potential mafic source-rocks, whereas no mafic rocks are associated with the Zana or Kowaliga units.  The Elkahatchee was chosen based on past proposals for it age and because it is largely undeformed in many locations, making it an important time marker in the evolution of the southern Appalachians and a perplexing correlative to the gneissic rocks of the Zana and Kowaliga. Although the Camp Hill and Chattasofka Creek gneisses were shown to have ages indistinguishable from the age-range established for the Zana and Kowaliga, isotopic data clearly show that neither suite of plutons is related to the extensive mafic rocks exposed in the Dadeville complex.  U-Pb analyses of zircons from the Elkahatchee batholith showed that it is Devonian rather than Ordovician.  Collectively, geochemical data from the Zana, Kowaliga, Camp Hill, and Chattasofka Creek granitoids strongly suggest that Ordovician magmatism in the southern Appalachians was widespread. The new data from this study support previous suggestions that these granitoids were anatectic melts of Mesoproterozoic (Grenville-age, ~1000 m.y.) lower crust.

In terms of broader impacts, the project met its goals of providing advanced training and educational opportunities to undergraduate students from CSU.  Both graduate and undergraduate students from the UFL were involved in introducing the CSU students to the geochemical sample preparation and analysis procedures used at the UFL.  Acting as instructors and providing oversight for the CSU students was also an important aspect of the professional growth of the UFL students. In addition, collaboration with students from Florida State University (FSU) who were working in the Dadeville under an EdMap project provided for both efficient sampling and an introduction to zircon geochronology for the FSU students. In terms of outreach, the best exposures of the Zana and Kowaliga are along the Horseshoe Bend stretch of the Tallapoosa River in Horseshoe Bend National Military Park.  Our findings, therefore, enhance understanding of the natural history of the park.  Economically, the new age data for rocks in Dadeville will impact base metal and platinum group exploration projects currently underway in the Dadeville.

Last Modified: 08/28/2017
Modified by: Paul A Mueller