Stratigraphy, eruption, and evolution of the Columbia River Basalt Group

Abstract

The Miocene Columbia River Basalt Group (CRBG) is world famous and the best studied continental flood basalt province on Earth. Decades of field and laboratory study have resulted in a detailed stratigraphy, consisting of seven formations containing more than 350 flows, a well-constrained chronology, and a large geochemical database. Petrogenesis of the flood basalts is constrained by many thousands of major element, trace element, and isotopic analyses of whole rocks and their constituent minerals. There is broad consensus that the province is the product of a deep mantle plume, although the details of plume interaction with North American lithosphere, and the generation, storage, transport, and eruption of flood basalt magma, are the subjects of continuing research. This field trip focuses on basalt flow sequences, dikes, vents, evolution of basaltic magmas through the lifetime of flood lava activity, and their relation to the larger Yellowstone Hotspot Province. The formations to be examined include the Imnaha, Grande Ronde, Wanapum, and Saddle Mountain Basalts. Trip stops are primarily along the Snake and Grande Ronde Rivers located in and adjacent to the canyon country of southeast Washington, western Idaho, and northeast Oregon.