An introduction to the stratigraphy, structural geology, and hydrogeology of the Columbia River Flood-Basalt Province

Abstract

The Miocene Columbia River Basalt Group (CRBG) covers a large part of Oregon, Washington, and Idaho and is one of the youngest and perhaps the best studied flood-basalt province on Earth. Decades of study have established a regional strati-graphic framework for the CRBG, have demonstrated the CBRG flows can be correlated with dikes and vents, have documented a wide variety of physical features within the CRBG flows, and have demonstrated that many characteristics of the CRBG are recognizable throughout its extent. Detailed studies of individual flows and their feeder dikes have allowed the development of models for the emplacement of voluminous basaltic lava flows. The interplay between the regional structure, contemporaneous deformation, preexisting topography, and paleodrainage systems helped to control the emplacement of individual CRBG flows. These features have also affected the nature of late Neogene sedimentation in the region covered by basalt flows. Finally, the distribution of sediments within the CRBG and the character of the intraflow and interflow structures have played a significant role in the development of aquifers within the CRBG. In this paper we present an overview of the regional aspects of the stratigraphy, structural geology, tectonics, and hydrogeology of the CRBG.

Alteration, mass analysis, and magmatic compositions of the Sentinel Bluffs Member, Columbia River flood basalt province

“…CRBG lavas generally have been considered to be chemically homogeneous (e.g., Wright et al, 1973;Hooper, 1984Hooper, , 1988Hooper, , 2000Reidel et al, 1989;Tolan et al, 2009), although a few exceptions have been reported (Reidel and Fecht, 1987;Reidel, 1998Reidel, , 2005Vye-Brown et al, 2013a;. Chemical variations within a flow or package of flows are also observed.…”

Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, Washington

“…CRBG flood basalts erupted from vents and fissures in southeastern Washington and northeastern Oregon 17.5 Ma to 6.0 Ma (Figure 4). Together they filled a volume of 174,000 km 3 , covered an area of about 163,700 km 2 [Tolan et al, , 2009, and in some cases flowed all the way to the Pacific Ocean Wells et al, 2009]. By far the greatest pulse of CRBG extrusion occurred 17.0 to 15.6 Ma, with eruption of the Grande Ronde Basalt: approximately 120 individual flows that together comprise 148,600 km 3 of basaltic lava [Reidel et al, 1989b].…”

Igneous Rock Associations 15. The Columbia River Basalt Group: A Flood Basalt Province in the Pacific Northwest, USA

“…A combination of lithology, paleomagnetic properties, and geochemical composition with regard to superposition have proved the most useful features to describe and characterize the stratigraphy (e.g. Swanson et al 1979;Camp 1981;Reidel 1983Reidel , 1998Reidel , 2005Beeson et al 1985Beeson et al , 1989Martin 1989;Reidel et al 1989a;Wells et al 1989;Hooper et al 2007;Tolan et al 2009). The current stratigraphic framework of the CRBG is discussed by and shown in Figure 2.…”