NEW GEOLOGIC MAP AND GEOCHRONOLOGY OF THE GREAT SMOKY MOUNTAINS NATIONAL PARK REGION, TN/NC

From 1993 to 2003, a cooperative investigation between the U.S. Geological Survey and the National Park Service studied the geology of the Great Smoky Mountain National Park region of Tennessee and North Carolina. The investigation focused on mapping previously unstudied terrain and revising the geology in problem areas. Recently published work includes a 1:100,000-scale combined surficial and bedrock geologic map (http://pubs.usgs.gov/of/2005/1225/) derived from 1:24,000- and 1:62,500- scale mapping. The map augments an on-going soil survey of the park by the U.S. Natural Resource Conservation Service. Additionally, the geologic information provides a foundation for a variety of co-investigators in the park, including those of the All Taxa Biodiversity Inventory.

The new studies have revealed that the rocks of the region were affected by multiple tectonic events from the Mesoproterozoic through the Paleozoic. Geochronologic analyses of zircon, sphene, monazite, and xenotime using U-Pb SHRIMP, 40Ar/39Ar analysis of hornblende and muscovite, fission-track analysis of zircon and apatite, and 10Be techniques document the following tectonic history:

1) Mesoproterozoic plutonism and tectonism from ca. 1195 to 1030 Ma associated with Grenvillian orogenesis;

2) Neoproterozoic uplift, cooling, erosion, extension, and sedimentation from ca. 870 to 700 Ma;

3) metamorphism at lower greenschist-facies from 685 to 560 Ma, amphibolite-facies at ca. 440 Ma (Taconian), and greenschist-facies accompanied by deformation at ca. 350 to 340 Ma (Neoacadian) and ca. 280 Ma (Alleghanian); and

4) post-Triassic unroofing, uplift, and erosion at rates between 28 and 18 m/m.y.