Devonian Stratigraphy in East-Central Idaho: New Perspectives from the Lemhi Range and Bayhorse Area

Shelf-to-basin stratigraphic studies of Devonian rocks in the Lemhi Range and Bayhorse area reveal new paleogeographic reso-lution of depositional environments across E-W and NNW-SSE transects. Lower and Middle Devonian mixed carbonate and siliciclastic strata (<600 m thick) include restricted shallow-ma-rine deposits of the Carey Dolomite, unnamed marginal-marine deposits, and discontinuous paleovalley deposits of the Beartooth Butte Formation. Estuarine and inner shelf lithofacies with mi-cro- and macrovertebrate faunal assemblages including thelodonts, pteraspids, acanthodians, osteostracans and placoderms allow basinward correlation with conodont-bearing deposits of the Carey Dolomite and associated unnamed strata. Fluvio-karst deposits and filled incised valleys in the Lemhi Range suggest that the exposed lower Paleozoic shelf had moderate topography an