David E. Fastovsky, Robert H Dott, Jr.; Sedimentology, stratigraphy, and extinctions during the Cretaceous-Paleogene transition at Bug Creek, Montana. Geology ; 14 (4): 279–282. doi: https://doi.org/10.1130/0091-7613(1986)14<279:SSAEDT>2.0.CO;2
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Bug Creek Valley, the source of an unusual and controversial Cretaceous-Paleogene coincidence of mammals, dinosaurs, pollen, and indium, exemplifies the importance of depositional process in the reconstruction of evolutionary events. Five sedimentary facies are recognized at Bug Creek: a cross-stratified sandstone, a green and purple siltstone, a lateral accretionary sandstone, a coal, and a variegated siltstone. Repeated fluvial channeling restricts the accuracy of lateral correlations, and the relationship of the fossil assemblage to the presumed Cretaceous-Paleogene boundary cannot be established. Sedimentologically, the Cretaceous-Paleogene transition is represented here by Cretaceous meandering channels that gave way initially to Paleogene swamp deposition.