CRUSTAL ARCHITECTURE AND TIMING OF AN ACCRETIONARY OROGEN: SALMON RIVER SUTURE ZONE AND WESTERN IDAHO SHEAR ZONE

In western Idaho and eastern Oregon two crustal scale features, the Salmon River suture zone and the Western Idaho shear zone record Cretaceous, subduction-related mountain building processes. Recent work has suggested that these two features may temporally and spatially overlap or be a single, continuous event. In preparation for 1:24,000 scale geologic mapping to investigate the genetic relationship between the Salmon River suture and Western Idaho shear zones (scheduled for Summer 2017), we have (1) constructed regional cross sections through the area of interest, (2) compiled regional gravity and magnetic data and constructed residual anomaly maps, (3) generated preliminary gravity models, (4) created a general tectonic timeline from available geochronologic data, and (5) conducted reconnaissance microstructural analyses on garnet porphyroblasts. Gravity modeling will be used to “calibrate” regional cross sections to the available gravity data, which might give insight into the steepness of major fault boundaries. The tectonic timeline will illustrate the available age controls and be used to compare the timing and pace of orogenic events in the Salmon River area to other Cordilleran accretionary orogens, while microstructural data will yield insight into the deformation style and evolution of the regional stress field. We hope this work will provide insight into the tectonic relationships between deformation events ahead of our future work.