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

虽然大多数人认为阿巴拉契亚山脉应该在很久以前就已经被侵蚀了，但它们在形成2亿多年后仍然屹立不倒。对这一经典问题有两种可能的解释：要么是它们被侵蚀得极其缓慢，要么是它们在最近的地质历史中再次抬升。Granger和他的同事们建议使用最先进的方法来测试这两种情况，以确定阿巴拉契亚山脉南部保存下来的古代景观的零星残留物，从第一次世界大战期间开采的锰矿到田纳西州东部修建道路时发现的一个化石丰富的天坑。该项目将使用40Ar/39Ar来确定在地表附近风化带形成的含钾锰矿的形成日期，传统上被认为是古代景观的遗迹。宇宙成因的26Al和10Be将被用于测定田纳西河和谢南多阿河沿线梯田的年代，以确定河流切割率，也将用于测定田纳西州格雷天坑沉积物中含有化石的沉积物的年代。这项工作代表了普渡大学的格兰杰和研究生奥多姆与东田纳西州立大学的研究人员以及美国地质调查局和澳大利亚昆士兰大学的测年专家之间的新合作，并直接涉及一名STEM教师将地球科学带入课堂。

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.