Stratigraphic and structural evolution of the middle Miocene synvolcanic Oregon-Idaho graben

Cummings, Michael L.; Evans, James George; Ferns, Mark L.; Lees, K.R.

doi:10.1130/0016-7606(2000)112<668:saseot>2.0.co;2

Cited by 70 publications

(40 citation statements)

References 24 publications

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“…At its maximum highstand of about 1,150 m, the lake may have covered nearly 20,000 km 2 , about the same area as modern Lake Ontario in eastern North America. Lake Idaho's initiation has been inferred by some workers to post-date the rhyolitic volcanism in the central Snake River Plain (Wood and Clemens 2002) but there is increasing evidence that it existed during the emplacement of many western Snake River rhyolitic units in the 11.7-10.0 Ma interval (McCurry et al 1997;Bonnichsen et al 2007;Bonnichsen and Godchaux 2002;Godchaux and Bonnichsen 2002), and it may have been a continuation of older Miocene lakes such as those in the Oregon-Idaho graben (Cummings et al 2000) and Goose Creek Basin (Fig. 1).…”

Section: Aqueously Deposited Volcaniclastic Sedimentsmentioning

confidence: 95%

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

et al. 2007

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A new category of large-scale volcanism, here termed Snake River (SR)-type volcanism, is defined with reference to a distinctive volcanic facies association displayed by Miocene rocks in the central Snake River Plain area of southern Idaho and northern Nevada, USA. The facies association contrasts with those typical of silicic volcanism elsewhere and records unusual, voluminous and particularly environmentally devastating styles of eruption that remain poorly understood. It includes: (1) largevolume, lithic-poor rhyolitic ignimbrites with scarce pumice lapilli; (2) extensive, parallel-laminated, medium to coarsegrained ashfall deposits with large cuspate shards, crystals and a paucity of pumice lapilli; many are fused to black vitrophyre; (3) unusually extensive, large-volume rhyolite lavas; (4) unusually intense welding, rheomorphism, and widespread development of lava-like facies in the ignimbrites; (5) extensive, fines-rich ash deposits with abundant ash aggregates (pellets and accretionary lapilli); (6) the ashfall layers and ignimbrites contain abundant clasts of dense obsidian and vitrophyre; (7) a bimodal association between the rhyolitic rocks and numerous, coalescing lowprofile basalt lava shields; and (8) widespread evidence of emplacement in lacustrine-alluvial environments, as revealed by intercalated lake sediments, ignimbrite peperites, rhyolitic and basaltic hyaloclastites, basalt pillow-lava deltas, rhyolitic and basaltic phreatomagmatic tuffs, alluvial sands and palaeosols. Many rhyolitic eruptions were high mass-flux, large volume and explosive (VEI 6-8), and involved H 2 O-poor, low-δ 18 O, metaluminous rhyolite magmas with unusually low viscosities, partly due to high magmatic temperatures (900-1,050°C). SR-type volcanism contrasts with silicic volcanism at many other volcanic fields, where the fall deposits are typically Plinian with pumice lapilli, the ignimbrites are low to medium grade (non-welded to eutaxitic) with abundant pumice lapilli or fiamme, and the rhyolite extrusions are small volume silicic domes and coulées. SR-type volcanism seems to have occurred at numerous times in Earth history, because elements of the facies association occur within some other volcanic fields, including Trans-Pecos Texas, EtendekaParaná, Lebombo, the English Lake District, the Proterozoic Keewanawan volcanics of Minnesota and the Yardea Dacite of Australia.

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Section: Aqueously Deposited Volcaniclastic Sedimentsmentioning

confidence: 95%

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

et al. 2007

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“…The regional geology consists primarily of volcanic and volcaniclastic rocks of Tertiary and Quaternary age. Thick sequences of fluviolacustrine sediments have accumulated since the Miocene in tectonically controlled, largely extensional basins (Cummings, 1991;Christiansen and Yeats, 1992;Cummings et al, 2000). Igneous deposits ranging in composition from rhyolitic ash flow tuffs and calderas to basaltic lava flows form lowgradient plateau tops punctuated by higher-standing peaks.…”

Section: Study Area and Dam Sitesmentioning

confidence: 99%

Plugs or flood-makers? The unstable landslide dams of eastern Oregon

et al. 2015

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Landslides into valley bottoms can affect longitudinal profiles of rivers, thereby influencing landscape evolution through base-level changes. Large landslides can hinder river incision by temporarily damming rivers, but catastrophic failure of landslide dams may generate large floods that could promote incision. Dam stability therefore strongly modulates the effects of landslide dams and might be expected to vary among geologic settings. Here, we investigate the morphometry, stability, and effects on adjacent channel profiles of 17 former and current landslide dams in eastern Oregon. Data on landslide dam dimensions, former impoundment size, and longitudinal profile form were obtained from digital elevation data constrained by field observations and aerial imagery; while evidence for catastrophic dam breaching was assessed in the field. The dry, primarily extensional terrain of low-gradient volcanic tablelands and basins contrasts with the tectonically active, mountainous landscapes more commonly associated with large landslides. All but one of the eastern Oregon landslide dams are ancient (likely of order 10 3 to 10 4 years old), and all but one has been breached. The portions of the Oregon landslide dams blocking channels are small relative to the area of their source landslide complexes (0.4-33.6 km 2 ). The multipronged landslides in eastern Oregon produce marginally smaller volume dams but affect much larger channels and impound more water than do landslide dams in mountainous settings. As a result, at least 14 of the 17 (82%) large landslide dams in our study area appear to have failed cataclysmically, producing large downstream floods now marked by boulder outwash, compared to a 40-70% failure rate for landslide dams in steep mountain environments. Morphometric indices of landslide dam stability calibrated in other environments were applied to the Oregon dams. Threshold values of the Blockage and Dimensionless Blockage Indices calibrated to worldwide data sets successfully separate dam sites in eastern Oregon that failed catastrophically from those that did not. Accumulated sediments upstream of about 50% of the dam sites indicate at least short-term persistence of landslide dams prior to eventual failure. Nevertheless, only three landslide dam remnants and one extant dam significantly elevate the modern river profile. We conclude that eastern Oregon's landslide dams are indeed floodmakers, but we lack clear evidence that they form lasting plugs.

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“…Shaded region is the approximate extent of mid-Miocene flood basalt volcanism (after Hart and Carlson 1985;Camp and Ross 2004). Also shown are major flood basalt dike swarms/eruptive loci (black lines), Oregon-Idaho graben and magnetic anomalies in Nevada corresponding to zones of lithospheric extension/mafic magma emplacement (black dotted-dashed lines; Cummings et al 2000;Glen and Ponce 2002), major volcanic fields of the Yellowstone-Snake River plain province (dashed circles); BJ, Bruneau-Jarbidge (∼12.5-<11 Ma); TF, Twin Falls (∼10-8.6 Ma); PC, Picabo (∼10 Ma); HS, Heise (∼6.7-4.3 Ma); and YS, Yellowstone (<2.5 Ma), and age isochrons (dashed black lines, ages in Ma) of Oregon High Lava Plains silicic volcanism (N Newberry Volcano; after Jordan et al 2004). The SC lies between the initial 87 Sr/ 86 Sr 0.706 and 0.704 isopleths (after Armstrong et al 1977;Kistler and Peterman 1978;Leeman et al 1992;Crafford and Grauch 2002).…”

Section: Introductionmentioning

confidence: 98%

“…Recent studies dealing with mid-Miocene northwestern United States volcanism have focused on the Steens and Columbia River flood basalts, their relationship to younger regional Cenozoic volcanism, and its relationship to mid-Miocene mineralization and rift-development ( Fig. 1a; Zoback et al 1994;Wallace and John 1998;Cummings et al 2000;John 2001;Camp et al 2003;Wallace 2003;Camp and Ross 2004;Jordan et al 2004). While these studies have focused attention on regional mafic volcanism and silicic volcanism peripheral to the loci of mid-Miocene activity (the Oregon Plateau), the details of mid-Miocene Oregon Plateau silicic activity remain poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Diverse mid-Miocene silicic volcanism associated with the Yellowstone–Newberry thermal anomaly

Brueseke

Heizler

2007

Bull Volcanol

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The Santa Rosa-Calico volcanic field (SC) of northern Nevada is a complex, multi-vent mid-Miocene eruptive complex that formed in response to regional lithospheric extension and flood basalt volcanism. Santa Rosa-Calico volcanism initiated at ∼16.7 Ma, concurrent with regional Steens-Columbia River flood basalt activity and is characterized by a complete compositional spectrum of basalt through high-silica rhyolite. To better understand the relationships between upwelling mafic magmatism, coeval extension, and magmatic system development on the Oregon Plateau we have conducted the first comprehensive study of Santa Rosa-Calico silicic volcanism. Detailed stratigraphic-based field sampling and mapping illustrate that silicic activity in this volcanic field was primarily focused along its eastern and western margins. At least five texturally distinct silicic units are found in the western Santa Rosa-Calico volcanic field, including abundant lava flows, near vent deposits, and shallow intrusive bodies. Similar physical features are found in the eastern portion of the volcanic field where four physically distinct units are present. The western and eastern Santa RosaCalico units are characterized by abundant macro-and microscopic disequilibrium textures, reflecting a complex petrogenetic history. Additionally, unlike other mid-Miocene Oregon Plateau volcanic fields (e.g. McDermitt), the Santa Rosa-Calico volcanic field is characterized by a paucity of caldera-forming volcanism. Only the Cold Springs tuff, which crops out across the central portion of the volcanic field, was caldera-derived. Major and trace element geochemical variations are present within and between eastern and western Santa Rosa-Calico silicic units and these chemical differences, coupled with the observed disequilibrium textures, illustrate the action of open-system petrogenetic processes and melt derivation from heterogeneous source materials. The processes and styles of Santa Rosa-Calico silicic magmatism are linked to three primary factors, local focusing of and thermal and material contributions from the regional flood basalt event, lithospheric extension within the northern portion of the Northern Nevada rift, and interaction of mid-Miocene silicic magmas with pre-Santa Rosa-Calico lithosphere. Similar processes and styles of mid-Miocene silicic volcanism likely occurred across the Oregon Plateau in regions characterized by both focused lithospheric extension and localized mafic magmatism. Editorial responsibility: M. McCurry This paper constitutes part of a special issue dedicated to Bill Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites. Electronic supplementary material The online version of this article (

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Stratigraphic and structural evolution of the middle Miocene synvolcanic Oregon-Idaho graben

Cited by 70 publications

References 24 publications

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

Plugs or flood-makers? The unstable landslide dams of eastern Oregon

Diverse mid-Miocene silicic volcanism associated with the Yellowstone–Newberry thermal anomaly

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