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• 1. [Article] The stratigraphy and structure of the Columbia River basalt group in the Bull Run watershed, Multnomah and Clackamas Counties, Oregon

  Approximately 150 meters (500 feet) of Grande Ronde Basalt and 140 meters (450 feet) of Wanapum Basalt of the Columbia River Basalt Group are exposed in the Bull Run Watershed. In Bull Run, the Grande ...

  Citation × Citation Citation Abstract Copy Title: The stratigraphy and structure of the Columbia River basalt group in the Bull Run watershed, Multnomah and Clackamas Counties, Oregon Author: Vogt, Beverly Frobenius Year: 1981 Approximately 150 meters (500 feet) of Grande Ronde Basalt and 140 meters (450 feet) of Wanapum Basalt of the Columbia River Basalt Group are exposed in the Bull Run Watershed. In Bull Run, the Grande Ronde Basalt is divided into three mappable units: "low Mg" R2 (at least one flow), "low Mg" N2 (approximately four flows), and "high Mg" N2 (two to three flows}. The Wanapum Basalt is represented by two members: Frenchman Springs Member (six flows) and Priest Rapids Member (one flow). These units are identified by instrumental neutron activation analysis, paleomagnetism based on measurements with a fluxgate magnetometer, petrography, lithology, jointing, and stratigraphic position. Title: The stratigraphy and structure of the Columbia River basalt group in the Bull Run watershed, Multnomah and Clackamas Counties, Oregon Author: Vogt, Beverly Frobenius Year: 1981 Approximately 150 meters (500 feet) of Grande Ronde Basalt and 140 meters (450 feet) of Wanapum Basalt of the Columbia River Basalt Group are exposed in the Bull Run Watershed. In Bull Run, the Grande Ronde Basalt is divided into three mappable units: "low Mg" R2 (at least one flow), "low Mg" N2 (approximately four flows), and "high Mg" N2 (two to three flows}. The Wanapum Basalt is represented by two members: Frenchman Springs Member (six flows) and Priest Rapids Member (one flow). These units are identified by instrumental neutron activation analysis, paleomagnetism based on measurements with a fluxgate magnetometer, petrography, lithology, jointing, and stratigraphic position. Close

• 2. [Article] A preliminary investigation of the lithological characteristics of the Troutdale Formation in portions of the Camas, Sandy, Washougal, and Bridal Veil quadrangles

  The study area encompasses a region of about 80 square kilometers, centered about Corbett, Oregon. Sieve analyses suggest that the Troutdale Formation is composed of a conglomerate, a coarse-grained sandstone, ...

  Citation × Citation Citation Abstract Copy Title: A preliminary investigation of the lithological characteristics of the Troutdale Formation in portions of the Camas, Sandy, Washougal, and Bridal Veil quadrangles Author: Cole, David Lee Year: 1982 The study area encompasses a region of about 80 square kilometers, centered about Corbett, Oregon. Sieve analyses suggest that the Troutdale Formation is composed of a conglomerate, a coarse-grained sandstone, and a siltstone lithofacies. Measured sections data show that 56 to 60 percent of the Troutdale Formation's exposures are composed of the conglomerate lithofacies. The coarsegrained sandstone lithofacies makes up 34 to 38 percent, while the siltstone lithofacies makes up only 4 to 8 percent. Pebble count data show that the representation of basalt varies from 69 to 100 percent, with an average of 85 percent, while quartzite varies from 0 to 25 percent, with an average of 9 percent. Geochemical data show that at least one formal member and two informal members of the Columbia River Basalt Group (Frenchman Springs, Grande Ronde High Mg, and Grande Ronde Low Mg) compose part of the detritus. The geochemical data also show that rocks of the Boring Lavas or similar lavas are intercalated with the Troutdale Formation, high in the section. Grain mount petrographic data show that volcanic rock fragments are the dominant component in the coarse sand fraction of the Troutdale Formation. Many of the volcanic rock fragments contain brown glass with an index of refraction of 1.583 +/- 0.001, which indicates a mafic composition {silica content of 50 +/- 1 percent). The representation of volcanic rock fragments varies from 29 to 98 percent, with an average of 75 percent. Sedimentary rock fragments, such as chert, vary from 0 to 17 percent, with an average of 5 percent. Biotite ranges from 0 to 12 percent, with an average of 2 percent. Two-thirds of the samples which contain sedimentary rock fragments also contain biotite. Orthopyroxene varies from 0 to 18 percent, with an average of 5 percent. 2 The samples with the three greatest amounts of orthopyroxene do not contain sedimentary rock fragments or biotite. Title: A preliminary investigation of the lithological characteristics of the Troutdale Formation in portions of the Camas, Sandy, Washougal, and Bridal Veil quadrangles Author: Cole, David Lee Year: 1982 The study area encompasses a region of about 80 square kilometers, centered about Corbett, Oregon. Sieve analyses suggest that the Troutdale Formation is composed of a conglomerate, a coarse-grained sandstone, and a siltstone lithofacies. Measured sections data show that 56 to 60 percent of the Troutdale Formation's exposures are composed of the conglomerate lithofacies. The coarsegrained sandstone lithofacies makes up 34 to 38 percent, while the siltstone lithofacies makes up only 4 to 8 percent. Pebble count data show that the representation of basalt varies from 69 to 100 percent, with an average of 85 percent, while quartzite varies from 0 to 25 percent, with an average of 9 percent. Geochemical data show that at least one formal member and two informal members of the Columbia River Basalt Group (Frenchman Springs, Grande Ronde High Mg, and Grande Ronde Low Mg) compose part of the detritus. The geochemical data also show that rocks of the Boring Lavas or similar lavas are intercalated with the Troutdale Formation, high in the section. Grain mount petrographic data show that volcanic rock fragments are the dominant component in the coarse sand fraction of the Troutdale Formation. Many of the volcanic rock fragments contain brown glass with an index of refraction of 1.583 +/- 0.001, which indicates a mafic composition {silica content of 50 +/- 1 percent). The representation of volcanic rock fragments varies from 29 to 98 percent, with an average of 75 percent. Sedimentary rock fragments, such as chert, vary from 0 to 17 percent, with an average of 5 percent. Biotite ranges from 0 to 12 percent, with an average of 2 percent. Two-thirds of the samples which contain sedimentary rock fragments also contain biotite. Orthopyroxene varies from 0 to 18 percent, with an average of 5 percent. 2 The samples with the three greatest amounts of orthopyroxene do not contain sedimentary rock fragments or biotite. Close

• 3. [Article] The stratigraphy and structure of the Columbia River basalt in the Clackamas River drainage

  The Clackamas River drainage within the western Cascade Range is approximately aligned with a northwest trending lineation defined by the Portland Hills and the Brothers Fault zone. This area is occupied ...

  Citation × Citation Citation Abstract Copy Title: The stratigraphy and structure of the Columbia River basalt in the Clackamas River drainage Author: Anderson, James Lee Year: 1978 The Clackamas River drainage within the western Cascade Range is approximately aligned with a northwest trending lineation defined by the Portland Hills and the Brothers Fault zone. This area is occupied by an extensive Columbia River Basalt sequence that is deeply incised by the Clackamas River and its tributaries. Two major basalt units of the Yakima Basalt Subgroup, including the Grande Ronde Basalt and the Frenchman Springs Member of the Wanapurn Basalt, are distinguishable in a 515 meter to 550 meter accumulation. Of particular interest is the presence of five trending right-lateral strike-slip faults is consistent with a stress model of north-south compression and east-west extension. Title: The stratigraphy and structure of the Columbia River basalt in the Clackamas River drainage Author: Anderson, James Lee Year: 1978 The Clackamas River drainage within the western Cascade Range is approximately aligned with a northwest trending lineation defined by the Portland Hills and the Brothers Fault zone. This area is occupied by an extensive Columbia River Basalt sequence that is deeply incised by the Clackamas River and its tributaries. Two major basalt units of the Yakima Basalt Subgroup, including the Grande Ronde Basalt and the Frenchman Springs Member of the Wanapurn Basalt, are distinguishable in a 515 meter to 550 meter accumulation. Of particular interest is the presence of five trending right-lateral strike-slip faults is consistent with a stress model of north-south compression and east-west extension. Close