DATING THE CENOZOIC INCISION HISTORY OF THE TENNESSEE AND SHENANDOAH RIVERS WITH COSMOGENIC NUCLIDES AND 40Ar/39Ar IN MANGANESE OXIDES

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While most accounts hold that the Appalachian Mountains should have eroded away long ago, they remain standing more than 200 million years after they were formed. There are two possible explanations to this classic problem: either they eroded extremely slowly, or they were uplifted again in the geologically recent past. Granger and his colleagues propose to test these two scenarios by using state-of-the-art methods to date scattered remnants of an ancient landscape preserved throughout the southern Appalachians, from manganese ores mined during World War I to a fossil-rich sinkhole uncovered during road construction in East Tennessee.This project will use 40Ar/39Ar to date the formation of potassium-bearing manganese ores that form in the weathering zone near the ground surface, traditionally identified as relicts of an ancient landscape. Cosmogenic 26Al and 10Be will be used to date terraces along the Tennessee and Shenandoah Rivers to determine river incision rates, and also to date fossil-bearing deposits at a sinkhole deposit at Gray, Tennessee. This work represents new collaborations between Granger and graduate student Odom at Purdue University with researchers at East Tennessee State University and dating specialists at the U.S. Geological Survey and the University of Queensland, Australia, and directly involves a STEM teacher to bring geoscience to the classroom.