Volcanic signature of Basin and Range extension on the shrinking Cascade arc, Klamath Falls‐Keno area, Oregon

Priest, George R.; Hladky, Frank R.; Mertzman, Stanley A.; Murray, Robert B.; Wiley, Thomas J.

doi:10.1002/jgrb.50290

Cited by 9 publications

(12 citation statements)

References 43 publications

(123 reference statements)

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“…These model ages overlap with a spatial shift in volcanism from 7 to 4 Ma in the Crater Lake region (du Bray and John, 2011; Priest, 1990), possibly related to the inception of Basin and Range extension (Priest et al, 2013). Basin and Range extension is associated with more voluminous mafic volcanism in this portion of the Cascade arc, as well as eruption of a higher proportion of HAOT magmas relative to calc-alkaline basalts (Priest et al, 2013;Schmidt et al, 2008). We propose that a more abundant mafic input into the lower crust occurred during extension, which would have added a component that had a less radiogenic Os isotope composition and shifted the bulk lower crust towards more mantle-like Os compositions.…”

Section: Determining the Age Of The Lower And Upper Crust Beneath Mtmentioning

confidence: 86%

“…The radiogenic Os growth model of Hart et al (2002) suggests that Os isotope compositions for the low-γ Os group (magnetite analyses) are consistent with ages of ~7 to 2.5 Ma for the crustal component ( Figure 4; see Appendix 2 for calculation details). These model ages overlap with a spatial shift in volcanism from 7 to 4 Ma in the Crater Lake region (du Bray and John, 2011; Priest, 1990), possibly related to the inception of Basin and Range extension (Priest et al, 2013). Basin and Range extension is associated with more voluminous mafic volcanism in this portion of the Cascade arc, as well as eruption of a higher proportion of HAOT magmas relative to calc-alkaline basalts (Priest et al, 2013;Schmidt et al, 2008).…”

Section: Determining the Age Of The Lower And Upper Crust Beneath Mtmentioning

confidence: 86%

See 1 more Smart Citation

Os and U–Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

Ankney

Shirey

Hart

et al. 2016

Earth and Planetary Science Letters

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Interaction of mantle melts with the continental crust can have significant effects on the composition of the resulting melts as well as on the crust itself, and tracing this interaction is key to our understanding of arc magmatism. Lava flows and pyroclastic deposits erupted from ~50 to 7.7 ka at Mt. Mazama (Crater Lake, Oregon) were analyzed for their Re/Os and U-Th isotopic compositions. Mafic lavas from monogenetic vents around Mt. Mazama that erupted during the buildup to its climactic eruption have lower 187 Os/ 188 Os ratios (0.1394 to 0.1956) and high 230 Th excess ((230 Th/ 238 U) 0 of 1.18 to 1.302), whereas dacites and rhyodacites tend to have higher 187 Os/ 188 Os ratios (0.2292 to 0.2788) and significant 238 U excess ((230 Th/ 238 U) 0 of 0.941 to

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Section: Determining the Age Of The Lower And Upper Crust Beneath Mtmentioning

confidence: 86%

Section: Determining the Age Of The Lower And Upper Crust Beneath Mtmentioning

confidence: 86%

Os and U–Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

Ankney

Shirey

Hart

et al. 2016

Earth and Planetary Science Letters

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“…12 Ma (Figure 1) (Colgan et al, 2004; Dilles & Gans, 1995; Surpless et al, 2002; Trench et al, 2012; Wells & McCaffrey, 2013). Extensional faults in the Cascade Range represent the western limit of extensional deformation that initiated after 7 Ma (Priest et al, 2013; Sherrod & Pickthorn, 1992; Sherrod et al, 2004; Smith et al, 1987).…”

Section: Geologic Backgroundmentioning

confidence: 99%

Exhumation Timing in the Oregon Cascade Range Decoupled From Deformation, Magmatic, and Climate Patterns

et al. 2020

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The Cascade Range in the Pacific Northwest, USA, developed as an Eocene to recent volcanic arc along the Pacific/North American ocean-continent subduction zone. The volcanic arc is characterized by temporally and spatially variable magmatism. Crustal deformation that accompanied development of the arc transitions from N-S transpression in the Yakima Fold Belt and Puget lowland (western Washington, northern Oregon) to generally E-W transtension in the south (central and southern Oregon). Orography focuses precipitation along the western flank of the Cascade Range, whereas the eastern flank is relatively arid. We use the unique spatial variation in deformation, magmatic history, and orographic precipitation to investigate the contributions from tectonic and surface processes to rock uplift. We reconstruct the exhumation pathway of plutonic rocks throughout the Cascade Range by exploiting the unique juxtaposition of basalt-capped ridges above valleys exposing exhumed Cenozoic plutons. Multiple bedrock geochronometers and thermochronometers constrain the thermal history in six catchments along the Cascade arc from southern Oregon to southern Washington. U-Pb geochronology defines circa 10-24 Ma pluton crystallization ages. Apatite and zircon (U-Th)/He thermochronology ages range from circa 8-23 Ma. 40 Ar/ 39 Ar geochronology defines circa 5-8 Ma basalt emplacement. Our results reveal spatially and temporally variable shallow exhumation in the southern Washington and Oregon Cascades and that the timing of exhumation is earlier than circa 6-12 Ma exhumation previously reported in the Washington Cascades. Spatially and temporally variable exhumation highlights that crustal deformation plays a significant role in rock uplift in addition to erosional mass removal in concert with orographic precipitation. Plain Language Summary Geoscientists have long wondered whether slow, incremental plate tectonics that shapes our planet have direct impacts on Earth surface processes (like precipitation or erosion). More provocatively, could surface processes actually impact tectonics? Existing studies have provided a range of interpretations but often focus on places where intense precipitation (like the Indian monsoon) and deformation (the Himalaya) change spatially together. This makes it challenging to determine whether tectonics or climate is the main driver. We wanted to investigate this problem along the Cascade Range in Oregon and Washington, where precipitation and deformation patterns do not vary together, allowing us to disentangle the influence of surface and tectonic processes. We use geochronology and thermochronology to determine when rocks were exhumed from deep to shallow levels in the earth. This gave us clues on the timing of rock uplift. We hypothesized that if climate was the main driver, which is similar in the Cascades from north to south, the timing would be synchronized north to south. However, we found that the timing is variable along the Cascades. We conclude that the combination and interaction between tecto...

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“…2). Active faulting in the southern backarc region has been variably interpreted as the northern termination of the Walker Lane belt (Pease, 1969;Faulds and Henry, 2008), backarc extension (McKee et al, 1983), or the western margin of the Basin and Range Province (Pezzopane and Weldon, 1993;Priest et al, 2013). Analysis of gravity anomalies suggests that the orientation of active faults in the region is controlled by preexisting basement structures buried beneath the Neogene volcanic cover (Blakely et al, 1997;Langenheim et al, 2016).…”

Section: ■ Introductionmentioning

confidence: 99%

“…2A). N-striking normal faults and volcanic centers overlap in the southern and central Cascade arc from the Klamath graben northward and thus mark the western limit of active extension in the backarc (Sherrod and Pickthorn, 1992;Priest et al, 2013;Figs. 1 and 2).…”

Section: ■ Introductionmentioning

confidence: 99%

Active dextral strike-slip faulting records termination of the Walker Lane belt at the southern Cascade arc in the Klamath graben, Oregon, USA

2019

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Whether or not northward growth of the Walker Lane belt relates to northward motion of the Mendocino triple junction remains an open question in the study of western North American plate deformation. Uncertainty about the potential linkage arises from an incomplete understanding of how and where dextral transtension in the Walker Lane belt terminates on its northern end. To address this issue, we used bare-earth airborne light detection and ranging (LiDAR) topographic data to reveal the geomorphic record of active dextral transtensional deformation in the Klamath graben in the backarc of the southern Cascade arc, south-central Oregon, USA. Fault scarps in late Pleistocene glacial deposits indicate that at least 0.3 mm/yr of NW-SE dextral shear characterizes slip on the NW-striking Howard Bay fault system within the Klamath graben. Dextral slip on the Howard Bay fault is transferred northwestward into extension on N-striking normal faults within the Cascade arc. Thus, active faults in the Klamath graben mark the northern terminus of a dextral transtensional fault system spanning the southern Cascadia backarc from Crater Lake southward to the northern Sierra Nevada. A review of published geologic slip rates throughout the region of the southern Cascade arc suggests that dextral slip from the Walker Lane belt is transferred both into contractional structures in the northern Sacramento Valley and transtensional structures in the southern ~200 km section of the Cascadia backarc. Termination of transtensional deformation into the southern Cascade arc suggests that the Walker Lane belt propagates independently of the Mendocino triple junction and that, instead, expansion of the Basin and Range Province plays a central role in development of the Walker Lane belt.

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Volcanic signature of Basin and Range extension on the shrinking Cascade arc, Klamath Falls‐Keno area, Oregon

Cited by 9 publications

References 43 publications

Os and U–Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

Os and U–Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

Exhumation Timing in the Oregon Cascade Range Decoupled From Deformation, Magmatic, and Climate Patterns

Active dextral strike-slip faulting records termination of the Walker Lane belt at the southern Cascade arc in the Klamath graben, Oregon, USA

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