--> ABSTRACT: Transporting Coarse-Grained Material Long Distances Over Low Gradients: Cretaceous Conglomerates Filling Incised Valleys on the Cratonic Margin of the Western Interior Foreland Basin, by R. L. Brenner, G. A. Ludvigson, B. J. Witzke, P. L. Phillips, T. S. White, D. F. Ufnar, and R. M. Joeckel; #90906(2001)

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R. L. Brenner1, G. A. Ludvigson2, B. J. Witzke2, P. L. Phillips1, T. S. White1, D. F. Ufnar1, and R. M. Joeckel3

1Dept. of Geoscience, University of Iowa, Iowa City, IA
2Iowa Dept. of Natural Resources, Geological Survey Bureau, Iowa City, IA
3Nebraska Conservation and Survey Division, Lincoln, NE

ABSTRACT: Transporting Coarse-Grained Material Long Distances Over Low Gradients: Cretaceous Conglomerates Filling Incised Valleys on the Cratonic Margin of the Western Interior Foreland Basin

Conglomerates are widely distributed around the mid-Cretaceous margin of the eastern subcontinent of North America. One of these conglomeratic accumulations is the Albian Nishnabotna Member of the Dakota Formation  that was deposited within incised valleys cut into Paleozoic strata in Iowa and eastern Nebraska. An age of incision of 160-105 Ma for these paleovalleys is suggested based on the presence of Late Jurassic (Oxfordian Fort Dodge Formation) deposits preserved on interfluves in western Iowa (Anderson and McKay, 1999). The incised valleys terminate in estuarine settings in present-day eastern Nebraska.

Conglomerates are exposed in quarries in Sarpy and Cass counties, Nebraska and correlate to marine fossil-bearing mudrocks to the west (Brenner et al., 2000).

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado