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Sedimentology of a Paleovalley Fill: Pennsylvanian Kyrock Sandstone in Central Kentucky, U.S.A.: Abstract
What are the characteristics of the fill of a basal Pennsylvanian paleovalley in central Kentucky, how homogenous is it, what was its depositional environment, and how was it connected, if at all, with the Appalachian Basin to the east?
The paleovalley is about 200 feet (66 m) deep, about 3 miles (5 km) wide and has several sharply defined benches along its sides. Its fill is almost entirely sandstone and consists of two major sandstone bodies: a lower medium to coarse grained, crossbedded body and an upper, fine to medium grained crossbedded, but less homogenous body that contains some shale. The lower sandstone is interpreted to have been deposited by a low sinuosity braided stream; the upper unit was deposited by a series of small high sinuosity meandering streams 20 to 30 feet (6 to 10 m) deep. The upper unit has more variable paleocurrents and extends somewhat beyond the limits of the erosional valley.
The internal facies of the sandstone fill suggest deposition by a stream of perhaps about the size of the Wabash River (in southwestern Indiana) on an alluvial plain in a tropical climate. The change from braided to meandering pattern is probably related to lower gradients as alluviation encroached up paleoslope into the Illinois Basin in early Pennsylvanian time. There are several different ways to connect this paleovalley to the Appalachian Basin, none of which can be well established. East of the study area the sandstone becomes totally decemented and only scattered quartz pebbles and cobbles mark its former presence.
Acknowledgments and Associated Footnotes
1 Geology Department, University of Cincinnati, Cincinnati, Ohio 45221
Copyright © 2009 by the Canadian Society of Petroleum Geologists