Basalts of both Eocene and Miocene age from several groups
along the Oregon and Washington coasts have been analyzed for some
major, minor, and trace elements using instrumental neutron activation analysis (INAA). The rare earth element (REE) patterns observed
in these samples are used for comparisons within the groups studied...
Continental flood basalts represent short-lived but immense blasts of mafic magma to the continental crust. The youngest and smallest continental flood basalt worldwide, the Columbia River Basalt, initiated with the eruption of the most mafic member, the Steens Basalt (~16.9 Ma). The Steens Basalt is exposed in southeast Oregon, southwest...
The Columbia River Basalt consists of dozens of seemingly identical flows of basalt covering thousands of square miles of Oregon, Washington, and Idaho. For years, detailed mapping of the units relied almost entirely on subtle petrographic distinctions, the presence or absence of interbeds, and actual walking along contacts in the...
The Paleocene-lower Eocene volcanic rocks of the southern Oregon Coast Range
Roseburg Formation are the oldest remnant eruptive sequence of an oceanic islandseamount
province which is presently exposed along a north-south lineament that stretches
from Vancouver, B.C. into southwestern Oregon. This seamount terrane is thought to
have formed on the...
The High Lava Plains province (HLP) of southeastern Oregon is a Miocene to Recent volcanic upland characterized by widespread basaltic volcanism and west-migrating rhyolitic volcanism. New ⁴⁰Ar/³⁹Ar ages for HLP rhyolites demonstrate that the trend of migrating rhyolitic volcanism is robust, reflecting westward migration at a rate of -35 km/m.y....
The primary goal of this study is to assess the impact of a subduction component
added to the mantle wedge beneath the Oregon Cascades to the composition and fO2 of
primitive Cascade basalts. Olivine-hosted melt inclusions from compositionally diverse
basalts across the Cascade arc (~100 km) are utilized in an...
The Walla Walla Subbasin (WWSB) in Oregon is underlain by formations of the extensive Columbia River Basalt Group (CRBG) which have been deformed by post-Miocene folding and faulting. Extensive irrigation with groundwater from these basalt groups, as well as sedimentary aquifers and surface water diversions from the Walla Walla River,...