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Colgan, Joseph P.; Egger, Anne E.; John, David A.; Cousens, Brian; Fleck, Robert J.; Henry, Christopher D.

doi:10.1130/ges00650.1

Cited by 33 publications

(12 citation statements)

References 56 publications

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“…The volcanic rock fragments and young zircons in these two samples could have been sourced from either the basaltic to andesitic Oligocene Cascade arc (Du Bray and John 2011; see also Colgan et al 2011) or from the felsic Nevada ignimbrite flare-up (Henry and John 2013). Petrographic examination of our five Coastal terrane samples with the highest-Lv indicates that their volcanic rock fragments are basalts to andesites (Table 1), hence likely sourced from the Cascades.…”

Section: Type B Samples From the Coastal Terranementioning

confidence: 91%

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Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California

Dumitru

Ernst

Hourigan

et al. 2015

International Geology Review

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In northwestern California, the Franciscan subduction complex has been subdivided into seven major tectonostratigraphic units. We report U-Pb ages of ≈2400 detrital zircon grains from 26 sandstone samples from 5 of these units. Here, we tabulate each unit's interpreted predominant sediment source areas and depositional age range, ordered from the oldest to the youngest unit. (1) Yolla Bolly terrane: nearby Sierra Nevada batholith (SNB); ca. 118 to 98 Ma. Rare fossils had indicated that this unit was mostly 151-137 Ma, but it is mostly much younger. (2) Central Belt: SNB; ca. 103 to 53 Ma (but poorly constrained), again mostly younger than previously thought. (3) Yager terrane: distant Idaho batholith (IB); ca. 52 to 50 Ma. Much of the Yager's detritus was shed during major core complex extension and erosion in Idaho that started 53 Ma. An Eocene Princeton River-Princeton submarine canyon system transported this detritus to the Great Valley forearc basin and thence to the Franciscan trench. (4) Coastal terrane: mostly IB, ±SNB, ±nearby Cascade arc, ±Nevada Cenozoic ignimbrite belt; 52 to <32 Ma. (5) King Range terrane: dominated by IB and SNB zircons; parts 16-14 Ma based on microfossils. Overall, some Franciscan units are younger than previously thought, making them more compatible with models for the growth of subduction complexes by progressive accretion. From ca. 118 to 70 Ma, Franciscan sediments were sourced mainly from the nearby Sierra Nevada region and were isolated from southwestern US and Mexican sources. From 53 to 49 Ma, the Franciscan was sourced from both Idaho and the Sierra Nevada. By 37-32 Ma, input from Idaho had ceased. The influx from Idaho probably reflects major tectonism in Idaho, Oregon, and Washington, plus development of a through-going Princeton River to California, rather than radical changes in the subduction system at the Franciscan trench itself.

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Section: Type B Samples From the Coastal Terranementioning

confidence: 91%

“…After the Challis event, arc magmatism was established in the new Cascade arc to the west, becoming moderately voluminous by ca. 35 Ma and continuing to the present day (Du Bray and John 2011; see also Colgan et al 2011). Rocks of 35 to 26 Ma age were mainly basalt, basaltic andesite, and andesite.…”

Section: Franciscan Geology Of Northwestern Californiamentioning

confidence: 95%

Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California

Dumitru

Ernst

Hourigan

et al. 2015

International Geology Review

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“…That pattern is the primary evidence for relating magmatism to the removal (rollback?) of the formerly shallowly dipping Farallon slab, a mechanism proposed by many (Coney and Reynolds, 1977;Best and Christiansen, 1991;Christiansen and Yeats, 1992;Humphreys, 1995;Humphreys et al, 2003;Dickinson, 2006;Henry et al, 2009aColgan et al, 2011a). The dip of the subducting Farallon slab shallowed between ca.…”

Section: Rollback Origin Of Cenozoic Magmatismmentioning

confidence: 92%

Magmatism, ash-flow tuffs, and calderas of the ignimbrite flareup in the western Nevada volcanic field, Great Basin, USA

2013

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The western Nevada volcanic fi eld is the western third of a belt of calderas through Nevada and western Utah. Twenty-three calderas and their caldera-forming tuffs are reasonably well identifi ed in the western Nevada volcanic fi eld, and the presence of at least another 14 areally extensive, apparently voluminous ash-fl ow tuffs whose sources are unknown suggests a similar number of undiscovered calderas. Eruption and caldera collapse occurred between at least 34.4 and 23.3 Ma and clustered into fi ve ~0.5-2.7-Malong episodes separated by quiescent periods of ~1.4 Ma. One eruption and caldera collapse occurred at 19.5 Ma. Intermediate to silicic lavas or shallow intrusions commonly preceded caldera-forming eruptions by 1-6 Ma in any specifi c area. Caldera-related as well as other magmatism migrated from northeast Nevada to the southwest through time, probably resulting from rollback of the formerly shallow-dipping Farallon slab. Calderas are restricted to the area northeast of what was to become the Walker Lane, although intermediate and effusive magmatism continued to migrate to the southwest across the future Walker Lane. Most ash-fl ow tuffs in the western Nevada volcanic fi eld are rhyolites, with approximately equal numbers of sparsely porphyritic (≤15% phenocrysts) and abundantly porphyritic (~20-50% phenocrysts) tuffs. Both sparsely and abundantly porphyritic rhyolites commonly show compositional or petrographic evidence of zoning to trachydacites or dacites. At least four tuffs have volumes greater than 1000 km 3 , with one possibly as much as ~3000 km 3. However, the volumes of most tuffs are diffi cult to estimate, because many tuffs primarily fi lled their source calderas and/or fl owed and were deposited in paleovalleys, and thus are irregularly distributed.

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“…DuBray and John, 2011). Colgan et al (2011) inferred that this displacement was accommodated by a tear in the subducting Farallon slab (Fig. 3A).…”

Section: Extensional Arc (50-13 Ma)mentioning

confidence: 99%

Birth of a plate boundary at ca. 12 Ma in the Ancestral Cascades arc, Walker Lane belt of California and Nevada

Busby

2013

Geosphere

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The Walker Lane belt of eastern California and western Nevada is the northernmost extension of the Gulf of California transtensional rift, where the process of continental rupture has not yet been completed, and rift initiation can be studied on land. GPS and earthquake focal mechanism studies demonstrate that the Walker Lane belt currently accommodates NW-SE-directed movement between the Sierra Nevada microplate and the North American plate, but the timing and nature of rift initiation remains unclear. I present a model for plate-margin-scale initiation of the Gulf of California and Walker Lane transtensional rifts at ca. 12 Ma; localization of rifting in both was initiated by thermal weakening in the axis of a subduction-related arc undergoing extension due to slab rollback, and thermal weakening in the arc was enhanced by stalling of the trenchward-migrating precursor arc against a thick Cretaceous batholithic lithospheric profi le on its western margin. Rifting succeeded very quickly in the Gulf of California, due to stalling of Farallon slabs, but the Walker Lane transtensional rift has been unzipping northward along the axis of the Cascades arc, following the Mendocino triple junction. I infer that plate-margin-scale Walker Lane transtension was signaled by the development of an unusually large and voluminous transtensional arc volcanic center, the ca. 11.5-9 Ma Sierra Crest-Little Walker arc volcanic center. I show that the style of faulting in this large Miocene arc volcanic center closely matches that of Quaternary transtensional structures in the central Walker Lane, where it lies, and that it differs from southern and northern Walker Lane structures. This indicates that the temporal transition from E-W Basin and Range extension to NW-SEWalker Lane transtension occurred earlier than most workers have inferred. I also summarize new data which show that the central Sierra Nevada range front (from Long Valley to the Tahoe Basin) lies squarely within the Walker Lane belt, not to the west of it as previous workers have inferred.The leading tip of Walker Lane transtension is marked by large arc volcanic centers sited in transtensional stepovers; these include the ca. 11.5-9 Ma Sierra Crest-Little Walker volcanic center; north of that, the ca. 6.3-4.8 Ma Ebbetts Pass volcanic center; and north of that, the active Lassen volcanic center. In its wake, large rift volcanic centers are sited on transtensional stepovers or bends; these include the Long Valley and Coso volcanic fi elds. I predict that any <12 Ma large volcanic centers identifi ed by future workers in the Sierra Nevada-Walker Lane region, or in the Gulf of California, will prove to be sited at major releasing bends or stepovers.

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Cited by 33 publications

References 56 publications

Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California

Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California

Magmatism, ash-flow tuffs, and calderas of the ignimbrite flareup in the western Nevada volcanic field, Great Basin, USA

Birth of a plate boundary at ca. 12 Ma in the Ancestral Cascades arc, Walker Lane belt of California and Nevada

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