Westward Growth of Laurentia by Pre–Late Jurassic Terrane Accretion, Eastern Oregon and Western Idaho, United States: A Discussion

Abstract

Advances in the Blue Mountains province (BMP) and adjacent areas of the Pacific Northwest have required an occasional updating of terms used to express new concepts (“trans-Idaho discontinuity” [Yates 1968], “Sr-isotopic boundary” [Armstrong et al. 1977], “Salmon River suture zone” [Lund and Snee 1988], “western Idaho suture zone” [Strayer et al. 1989], “Bourne and Greenhorn subterranes” [Ferns and Brooks 1995], “western Idaho shear zone” [WISZ; McClelland et al. 2000], “Salmon River belt” [Gray and Oldow 2005], “Izee basin” [Dorsey and LaMaskin 2007], “Orofino shear zone” [McClelland and Oldow 2007], “Salmon River suture” [Lund et al. 2008], “arc-continent boundary” [Lewis et al. 2014]). As a consequence, tracking nomenclatural changes over time has presented periodic challenges to workers familiar with the regional geology; to the unfamiliar, this task is intensified by a literature fraught with tantalizing terminology understandable by few. Given the various tectonic elements (Helwig 1974) and etymological changes in the BMP, the probability of miscommunication is high. This discussion centers on a recent Journal of Geology article (LaMaskin et al. 2015) that misuses the Salmon River belt (SRB) terminology—and modifications thereof—when describing the geologic setting of west-central Idaho. Since the publication of Gray and Oldow (2005), various authors have referenced the SRB in tectonic models proposed to explain the outboard amalgamation, accretion, and/or truncation of volcanic-arc terranes comprising the BMP (e.g., Dorsey and LaMaskin 2007; McClelland and Oldow 2007; Giorgis et al. 2008; LaMaskin and Dorsey 2008; Blake et al. 2009;