Geologic map of the West Fall Butte quadrangle, Malheur County, Oregon

Evans, James George; Binger, G. Benjamin

doi:10.3133/ofr97481

Cited by 7 publications

(27 citation statements)

References 2 publications

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“…Creek members are aphyric and have been geochemically correlated with the Imnaha and Grande Ronde Basalts, respectively (Evans and Binger, 1997). The Dinner Creek Tuff is the only LOVF unit within the study area.…”

Section: Mid-miocene Volcanicsmentioning

confidence: 99%

“…It consists of basaltic-andesite and icelandite lava flows (Ferns and McClaughery, 2013). The Hunter Creek basalt is geochemically indistinguishable from the Birch Creek member of the Basalt of Malheur Gorge, and from the Grande Ronde Basalt (Evans and Binger, 1997). 40 Ar/ 39 Ar ages overlap with the Dinner Creek Tuff (15.7 -15.4 Ma), and the exact relationship between the two units is unclear (Nash and Perkins, 2012).…”

Section: Volcanic Rocks Overlying the Dinner Creek Tuffmentioning

confidence: 99%

“…Isostatic gravity data shows a gravity low immediately northwest of Westfall Butte, 20 km east of Castle Rock (Griscom and Halvorson, 1994;Evans and Binger, 1997). This low could indicate buried low density intra-caldera tuffs and caldera floor deposits, beneath overlying Hunter Creek basalt (Evans and Binger, 1997).…”

Section: Caldera Marginmentioning

confidence: 99%

“…Phenocrysts are mostly euhedral to subhedral plagioclase, which can reach lengths of 3 mm. Less common are titanomagnetite, and clinopyroxene phenocrysts (Haddock, 1967;Evans and Binger, 1997;Streck et al, 2015). Lithic fragments are also minor constituents of the tuff.…”

Section: Dinner Creek Tuffmentioning

confidence: 99%

“…It could be DIT3, based on the feldspar data, or it could be part of the Westfall Butte volcanic center, about 12 km southeast of the outcrop. This volcanic center consists of rhyolite lava flows and tuffs that are late Miocene in age (Evans and Binger, 1997).…”

mentioning

confidence: 99%

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Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon

Cruz¹

2000

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The Dinner Creek Tuff is a mid-Miocene rhyolitic to dacitic ignimbrite, consisting of four cooling units with 40 Two volcanic centers related to the Dinner Creek Tuff were identified. The southern volcanic center, centered at Castle Rock, is a caldera and source of the Dinner Creek Tuff unit 1 (DIT1). Rheomorphic, densely welded DIT1 is over 300 m thick along the east side of Castle Rock. The northwestern margin of the caldera has been uplifted along faults, showing vertically foliated tuff dikes and associated mega-breccia deposits.Up to 200 m of incipiently welded tuffs, and fluvial volcaniclastic sediments were deposited on the caldera floor, which has been uplifted due to resurgence and regional extension, creating the complex structural relationships between the volcanic units.The northern volcanic center is located at Ironside Mountain, where densely welded rheomorphic Dinner Creek Tuff unit 2 (DIT2) is exposed in outcrops over 600 m thick.

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Section: Mid-miocene Volcanicsmentioning

confidence: 99%

Section: Volcanic Rocks Overlying the Dinner Creek Tuffmentioning

confidence: 99%

Section: Caldera Marginmentioning

confidence: 99%

Section: Dinner Creek Tuffmentioning

confidence: 99%

mentioning

confidence: 99%

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Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon

Cruz¹

2000

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Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

Benson

Mahood

2016

Journal of Volcanology and Geothermal Research

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The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at ~15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of lowtemperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre-and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single ~20 x 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins ~300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are contemporaneous with the latest stages of eruptions nearby. High Rock and McDermitt rhyolites are associated with propagation of Steens Basalt dikes to the south, and LOVF rhyolites with later propagation of Grande Ronde Basalt dikes to the north and north-northwest.

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Genesis of flood basalts and Basin and Range volcanic rocks from Steens Mountain to the Malheur River Gorge, Oregon

Camp

Ross

Hanson

2003

Geological Society of America Bulletin

119

136

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The middle and south forks of the Malheur River provide a unique mapping corridor connecting two flood-basalt successions-Steens basalt to the south and the basalt of Malheur Gorge to the north. Each contains chemically defined subtypes, which merge stratigraphically across the north-south length of the map area. The lowermost flows of Steens basalt are stratigraphically equivalent to the lowermost flows of the basalt of Malheur Gorge. The uppermost flows of Steens basalt pinch out in the map area, but are partly interbedded with the middle and uppermost flows of the basalt of Malheur Gorge, which continue to thicken northward. The upper part of the tholeiitic succession is interbedded with a group of previously unrecognized lavasthe Venator Ranch basalt flows. Tholeiitic volcanism ceased at ca. 15.3 Ma; the last tholeiitic unit erupted is the Hunter Creek basalt, which also thickens northward. Subsequent (younger than 15.3 Ma), more localized eruptions were dominated by calc-alkaline to mildly alkaline lavas associated with Basin and Range extension. Local uplift generated deep canyons, which were filled by andesitic lavas of the Keeney sequence (ca. 13-10 Ma). The final eruptive products include the Devine Canyon tuff (ca. 9.7 Ma), the Drinkwater basalt (ca. 6.9 Ma), and the Voltage flow (older than 32,000 yr B.P.). Major and trace element analyses demonstrate that (1) crystal fractionation was a universal process in the derivation of the

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Geologic map of the West Fall Butte quadrangle, Malheur County, Oregon

Cited by 7 publications

References 2 publications

Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon

Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon

Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

Genesis of flood basalts and Basin and Range volcanic rocks from Steens Mountain to the Malheur River Gorge, Oregon

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