Geologic map of the Alder Creek Quadrangle, Malheur County, Oregon

Evans, James George; Binger, G. Benjamin

doi:10.3133/ofr98494

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…Clinoptilolite nearly completely replaces ash, and forms euhedral crystals in void space. Brooks and O'Brien (1992), Ferns and O'Brien (1992), Lees (1994), Binger (1997), Evans and Binger (1998a;, Johnson et al (1998), Evans and Binger (1999a;, Camp et al (2003), Nash and Perkins (2012), Ferns and McClaughry (2013), Coble and Mahood, in press, this study (see Appendix A for analyses and description of analytical technique).…”

Section: Fig 1 Regional Map Highlighting Mid-miocene (~17-15 Ma) Volcanic Rocks In the Pacificmentioning

confidence: 95%

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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Section: Fig 1 Regional Map Highlighting Mid-miocene (~17-15 Ma) Volcanic Rocks In the Pacificmentioning

confidence: 95%

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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“…Close relationships in terms of time and space of lavas of Hunter Creek Basalt (i.e., upper Grand Ronde Basalt) with the Dinner Creek Tuff have been found ~20 km southeast of the proposed source area from where Evans (1990) and Evans and Binger (1998) reported a mafi c vitrophyric lense with Hunter Creek Basalt composition in Dinner Creek Tuff; they suggested that these two magmas may have erupted contemporaneously. We investigate this further and use our compositional glass data obtained on shards, pumice shards, mafi c globules , and pumices that we found in one of the two 15.5 Ma cooling units (unit 2) and in the 14.9 Ma ignimbrite (unit 4).…”

Section: Mafi C Dinner Creek Tuff: Records Of Grande Ronde Basalt Magmasmentioning

confidence: 96%

Large, persistent rhyolitic magma reservoirs above Columbia River Basalt storage sites: The Dinner Creek Tuff Eruptive Center, eastern Oregon

2015

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Our understanding of the Yellowstone hotspot and its connection to fl ood basalts of the Columbia River Basalt province (western and northwestern USA) has grown tremendously over the past decades since the model was fi rst proposed in 1972. Despite strong support for a plume origin of the entire Yellowstone-Columbia River Basalt magmatic province, new non-plume models have emerged to explain early fl ood basalt volcanism. Unresolved issues of the early fl ood basalt stage include the location of crustal magma reservoirs feeding these voluminous eruptions and to what extent these were associated with contemporaneous silicic reservoirs. This study focuses on the newly defi ned ca. 16-15 Ma Dinner Creek Tuff Eruptive Center that overlaps in time and space with fl ood basalt volcanism of the Columbia River Basalt Group. New work on distribution, lithologic variations, geochemical compositions, and eruption ages indicate that the extensive Dinner Creek Welded Tuff (herein Dinner Creek Tuff) and associated mapped and unmapped ignimbrites include a minimum of 4 discrete cooling units that spread out over an area of ~25,000 km 2 . Widespread fallout deposits in northeast Oregon and the neighboring states of Nevada, Idaho, and Washington have now been compositionally correlated with the redefi ned Dinner Creek Tuff. Compositional coherence between the ignimbrite sheets and fallout deposits indicate a common source, herein referred to as the Dinner Creek Tuff eruptive center (DITEC). Cognate mafi c components (glass shards, pumice shards, and mafi c globules) that range from dacite (~68 wt% SiO 2 ) to Fe-rich basaltic andesite (~56 wt% SiO 2 ) in composition are found in two of the cooling units. Major and trace element compositions of the more mafi c components match the compositions of nearby Grande Ronde Basalt flows and dikes. Compositional similarities between cognate mafi c components and Grande Ronde Basalt fl ows are direct evidence for coeval mafi c and silicic magmatism linking DITEC and Grande Ronde Basalt eruptions. Furthermore, finding Grande Ronde Basalt magmas as coeruptive component in Dinner Creek Tuff suggests that Grande Ronde Basalt magmas were stored beneath Dinner Creek Tuff rhyolites, thereby providing the fi rst direct evidence for the location of a storage site of Columbia River Basalt magmas. Shallow crustal rhyolitic reservoirs active during ca. 16-15 Ma that yielded tuffs of the DITEC and other surrounding contemporaneous and widespread rhyolites of the area likely imposed control on timing and place of eruption of Columbia River Basalt Group lava fl ows.

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“…2) Kittleman et al (1965Kittleman et al ( , 1967, a 15.5 Ma rhyolite-dacite tuff (Sales et al, 2017). The icelandite of Alder Creek occupies the same stratigraphic position as the Hunter Creek Basalt (Kittleman et al, 1965(Kittleman et al, , 1967Evans and Binger, 1999c) and seemingly provides evidence of mixing of upper Littlefield Rhyolite and Hunter Creek Basalt magmas (see below and cf. Figs.…”

Section: Southern Stratigraphic Transect In Alder Creek Canyonmentioning

confidence: 98%

The Littlefield Rhyolite and associated mafic lavas: Bimodal volcanism of the Columbia River magmatic province, with constraints on age and storage sites of Grande Ronde Basalt magmas

et al. 2018

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We present data that distinguishes the long-known Littlefield Rhyolite of eastern Oregon (northwestern United States) into two distinct, voluminous, Snake River-type, high-temperature rhyolite lava packages that erupted in short sequence over <100 k.y., with minimum volumes of 100 and 150 km 3 respectively, contemporaneous with flood basalt volcanism of the Grande Ronde Basalt phase of the Columbia River Basalt Group. Contemporaneity of rhyolites with flood basalts is exceptionally demonstrated within the Malheur Gorge by intercalated mafic units belonging to the Grande Ronde Basalt that are stratigraphically constrained by underlying and overlying Littlefield Rhyolite flows, and the underlying Dinner Creek Tuff (unit 1). Our new ages of 16.11 Ma and 16.02 Ma for the lower and upper Littlefield Rhyolite, respectively, provide a narrow age constraint on the controversial lower age of Grande Ronde Basalt volcanism. Petrological data on local, intercalated Fe-rich andesitic (icelanditic) lavas provide further evidence for coeval existence of rhyolitic and mafic magmas, and additionally provide location evidence for storage sites of Grande Ronde Basalt magmas. Based on these data in addition to similar data on the nearby Dinner Creek Tuff rhyolite center, as well as the locations of other rhyolite centers that fall within the same period of intense rhyolite volcanism of ca. 16.1 Ma, we infer that Grande Ronde Basalt crustal magma reservoirs were widespread in this area of eastern Oregon. We further infer that the main eruptions of stored flood basalt magmas followed the magmas' lateral transport from these reservoirs to the well-known dike swarms located at the periphery of the rhyolite distribution area where local eruptions of rhyolites are notably absent. Our study highlights the interplay of mafic and crustally derived rhyolite magmas, with implications for other continental flood basalt provinces that are less well preserved than the Columbia River Basalt province.

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Geologic map of the Alder Creek Quadrangle, Malheur County, Oregon

Abstract: rural and stratigraphic transition zone is located about 2 km west of the eastern boundary of the Alder Creek quadrangle.

Cited by 5 publications

References 7 publications

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

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

Large, persistent rhyolitic magma reservoirs above Columbia River Basalt storage sites: The Dinner Creek Tuff Eruptive Center, eastern Oregon

The Littlefield Rhyolite and associated mafic lavas: Bimodal volcanism of the Columbia River magmatic province, with constraints on age and storage sites of Grande Ronde Basalt magmas

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