Steens Mountain is a major horst block near the northern terminus of the Basin and Range geomorphic province of southeastern Oregon. A section of Miocene volcanic rocks totaling 5000 feet in thickness are exposed in a fault escarpment on the eastern side of Steens Nountain. These include: the Pike Creek...
The Juniper Ridge volcanic complex is located in the High Lava Plains Province of
southeastern Oregon, a wide zone of bimodal volcanism and faulting that marks the northern
limit of widespread Basin and Range-style faulting in the northern Great Basin Province. Rhyolite
dome complexes are progressively younger to the northwest...
Volcanic and sedimentary deposits of the Mount Jefferson area (MJA) record a fourmillion-year history of arc-related volcanism related to the subduction of the Juan de Fuca plate beneath North America. 171 mapped stratigraphic units over an area of 150 km² reveal four periods of volcanic activity resulting in diverse composition...
Oregon’s High Lava Plains Province (HLP) has strongly bimodal basalt and rhyolitic volcanism. The Province caps the northern margin of the Basin and Range Province and serves as a transitional region between westward extension of the Basin and Range Province and unextended crust to the north . The High Lava...
Normal faults characterizing extensional provinces may terminate along-strike at regions of zero extension, at zones of transform faults, or at triple junctions. Termination of the Basin and Range extensional province in southeastern Oregon is thought to occur by right-lateral transform motion distributed across the Brothers Fault zone (BFZ) in central...
The northwestern corner of the Basin and Range Province (NWBR) lies in southeast Oregon where extensive Late Miocene, mafic to bimodal basalt-rhyolite volcanism and extensional faults dominate a stark and arid landscape. Near Lake Abert, the Late Miocene volcanic section abuts Early Miocene, dominantly intermediate composition volcanoes at the Coleman...
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 northern part of the Southeast Three Sisters quadrangle straddles
the crest of the central High Cascades of Oregon. The area is
covered by Pleistocene and Holocene volcanic and volcaniclastic rocks
that were extruded from a number of composite cones, shield volcanoes,
and cinder cones. The principal eruptive centers include...