Journal of Cave and Karst Studies - ISSN 1090-6924
Volume 66 Number 2: August 2004

A publication of the National Speleological Society

A Late Tertiary origin for multilevel caves along the western escarpment of the Cumberland Plateau, Tennessee and Kentucky, established by cosmogenic 26Al and 10Be
Darlene M. Anthony and Darryl E. Granger

Abstract

Cosmogenic burial dating of quartzose cave sediments deposited in multilevel caves beneath the western margin of the Cumberland Plateau date ~5.7 Ma of cave development in step with episodic incision of the Upper Cumberland River. These particular cave systems are characterized by hydrologically abandoned, low-gradient passages concentrated at common levels above the modern water table. Previous studies recognized morphometric differences between the majority of smaller, hydrologically active “plateau-margin” caves and large, abandoned “fossil” or “Cumberland-style” caves. This study links the origin of multilevel caves on the western margin to a prolonged period of Late Tertiary water table stability, and the development of levels to distinct episodes of Plio-Pleistocene river incision. In this study, clastic sediments in multilevel cave passages are dated using cosmogenic 26Al and 10Be, and are shown to correspond with 1) deposition of upland (“Lafayette-type”) gravels between ~3.5 Ma and ~5 Ma; 2) initial incision of the Cumberland River into the Highland Rim after ~3.5 Ma; 3) development of the Parker strath between ~3.5 Ma and ~2 Ma; 4) incision of the Parker strath at ~2 Ma; 5) shorter cycles of incision after ~1.3 Ma associated with terraces above the modern flood plain; and 6) regional aggradation at ~0.8 Ma. Burial ages of cave sediments record more than five million years of incision history within the unglaciated Appalachian Plateaus and constrain the developmental history of multilevel caves associated with the Upper Cumberland River.

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