DIGITAL COMPILATION OF INLAND-NORTHWEST TECTONIC AND IGNEOUS FEATURES

We present maps of Inland-Northwest tectonic and igneous features, derived from a digital database, compiled from 43 geologic maps, originally made at scales of 1:100 k and 1:250 k by USGS and geological agencies of Washington, Idaho, and Montana. The compiled maps, supplemented by information from the literature, indicate important tectonic and igneous features, such as: 1) Archean gneiss, intruded by the Stillwater layered intrusive complex in the Beartooth Range; 2) the NE-trending Great Falls Tectonic Zone (GFTZ), initiated as an Early Proterozoic collisional orogen between the Archean Wyoming and Hearn Provinces; 3) the Middle Proterozoic Belt Basin, including sub-basins, early-rift and late-sag strata, axial intrusions, and WNW-trending growth faults, regarded as early manifestations of the Lewis and Clark Tectonic Zone (LCTZ); 4) Late Proterozoic Windermere strata; 5) Early Paleozoic shelf, slope and deep-water strata of southeastern Idaho and the Kootenai arc; 6a) a suture zone in northern Washington, between the Kootenai arc and the accreted Quesnellia micro-continent; 6b) a suture zone in west-central Idaho, between the North American craton and oceanic island-arcs of the Blue Mountains accreted terrane; 7a) a major NW jog in (or sinstral offset of) the Blue Mountains suture zone, along the NW projection of the Trans-Idaho Discontinuity; 7b) veins of the Coeur d’Alene Ag-Pb-Zn mining region, within the LCTZ, and possibly formed during tectonism associated with docking of accreted terranes; 8a) Cordilleran compressional folds, thrust sheets, basement-cored uplifts, and Cretaceous intermontane basin-fill deposits; 8b) the Late Cretaceous Kaniksu, Idaho, and Boulder composite batholiths, and other plutons of the Cordilleran magmatic arc; 9a) Eocene metamorphic core complexes, bounded by detachment faults, and connected by Eocene dextral faults within and parallel to the LCTZ; 9b) Eocene volcanic fields and plutons of the Challis magmatic belt, with volcano-tectonic grabens and dike swarms along the GFTZ; 10) the Rocky Mountain trench north of the LCTZ, and block-faulted basins and ranges within and south of the GFTZ; 11) Miocene flood basalts of the Columbia River basin, and 12) tectonic and bimodal volcanic features of the Snake River Plain and Yellowstone caldera.