Southeastern Section–56th Annual Meeting (29–30 March 2007)

Paper No. 2
Presentation Time: 8:00 AM-12:00 PM


MCDONALD, W.M., HAMES, W.E., MARZEN, L.J. and STELTENPOHL, M.G., Geology and Geography, Auburn University, Auburn, AL 36849,

Innovations in laser analytical techniques for 40Ar/39Ar dating enable researchers to make up to ~ 100 age determinations in a single day, dramatically increasing the amount of data that can be generated and the types of problems that geochronology can address. Furthermore, it is now clear from many published studies that systematic age variations are to be expected for crystals separated from a single rock, and that different generations of a mineral within a given sample – such as muscovite in a schist – can be expected to yield different ages. Thus, managing large amounts of single crystal geochronologic data, placing that data in a structural or petrologic context, and interpreting it in the context of previous work is a formidable task that requires the use of advanced tools. We constructed a GIS database (with ARCGIS 9.1 desktop by ESRI) in order to manage, interpret and present 40Ar/39Ar ages that we determine for rocks from the southwestern Blue Ridge province. The database permits sample locations, regional and local geologic information, and sample-specific characteristics (including outcrop photos, representative photomicrographs of thin sections, and information regarding crystal grain size and shape) to be retrieved and examined in the context of age results obtained. The database is web-enabled (using EasySVG by Adobe and FrontPage by Microsoft) to provide open-access via the World Wide Web. For our geochronologic study, we used laser 40Ar/39Ar dating techniques in the Auburn Noble Isotope Mass Analysis Laboratory (ANIMAL) to determine the ages of single crystals from about thirty samples in the study region. These samples were collected along the frontal Blue Ridge province, near the Talladega-Cartersville and Great Smoky Thrusts in Georgia, and in the central Western Blue Ridge of North Carolina (along U.S. Hwy 64 between Ducktown, TN and Murphy, NC). Many of our samples yield an age of ca. 335-330 Ma, that we interpret to indicate significant Mississippian cooling and/or recrystallization in this part of the frontal Blue Ridge. This interpretation will be tested by further age determinations, and the GIS database we have constructed can be expanded to include our future work in the region, as well as radiometric data from other studies.