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Correlation, Sedimentology, Structural Setting, Chemical Composition, and Provenance of Selected Formations in Mesoproterozoic Lemhi Group, Central Idaho

By Russell G. Tysdal, David A. Lindsey, and Joseph E. Taggart, Jr.

U.S. Geological Survey Professional Paper 1668–A–B

Version 1.0
The middle subunit of the Mesoproterozoic Yellowjacket Formation in the Salmon River Mountains is renamed the banded siltite unit and is assigned to the Apple Creek Formation. The overlying sandstone is assigned to the Gunsight Formation. These strata are part of the Poison Creek thrust sheet, which is extended westward from the Lemhi Range into the Salmon River Mountains. Major-oxide ratios, statistical analysis of covariance among major oxides and trace elements, and analysis of variance among stratigraphic units are used to determine relationships between provenance and chemical composition of the Mesoproterozoic Big Creek, Apple Creek, and Gunsight Formations.

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