Physical Sciences and Mathematics Commons^™

Cenozoic Structural And Stratigraphic Evolution Of The Southeastern Salmon Basin, East-Central Idaho, James J. Blankenau

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The southeastern Salmon basin (SB) of east-central Idaho is a complex east-dipping half graben containing four unconformity-bounded sequences of Tertiary volcanic, alluvial fan, lacustrine, and fluvial deposits. From oldest to youngest these are the Challis volcanic group, sedimentary rocks of Tendoy (new name), sedimentary rocks of Sacajaweja (new name), and Quaternary-Tertiary deposits . The thick sequence of volcanic rocks was deposited in a southeast-trending paleovalley . New mapping, cross-cutting relationships, ⁴⁰Ar/³⁹Ar age determinations, and angular unconformities show that the SB has experienced at least four episodes of extension, and that it lies in the core of an …