The birth of a forearc: The basal Great Valley Group, California, USA

Orme, Devon A.; Surpless, Kathleen D.

doi:10.1130/g46283.1

Cited by 36 publications

(31 citation statements)

References 45 publications

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“…However, detrital zircons with Cretaceous U‐Pb ages in many of the near‐base sandstones previously assigned to the Jurassic in Northern California contradict this assignment (Figure 2a; Orme & Surpless, 2019; Surpless et al, 2006). Calculated maximum deposition ages range 153–135 Ma and imply a temporal gap between CRO formation and the beginning of Great Valley group deposition of up to 15–23 Ma in four studied sites (Orme & Surpless, 2019).…”

Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 97%

“…The basal age of sedimentation is a matter of recent debate: Biostratigraphic constraints based on Buchia zones indicate sedimentation in the late Kimmeridgian (~155 Ma) in northern California to late Tithonian (~145 Ma) in central California (Figure 2a; Hopson et al, 2008, and references therein). However, detrital zircons with Cretaceous U‐Pb ages in many of the near‐base sandstones previously assigned to the Jurassic in Northern California contradict this assignment (Figure 2a; Orme & Surpless, 2019; Surpless et al, 2006). Calculated maximum deposition ages range 153–135 Ma and imply a temporal gap between CRO formation and the beginning of Great Valley group deposition of up to 15–23 Ma in four studied sites (Orme & Surpless, 2019).…”

Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 97%

“…Localities are sorted from North to South based on their position prior to Cenozoic strike‐slip motion (reconstruction of Wakabayashi, 1999). Abbreviations: A2004 (Anczkiewicz et al, 2004); CS2007 (Catlos & Sorensen, 2003); C2011 (Cooper et al, 2011); D2010 (Dumitru et al, 2010); H2008 (Hopson et al, 2008); M2009 (Mulcahy et al, 2009); M2014 (Mulcahy et al, 2014); M2018 (Mulcahy et al, 2018); O2019 (Orme & Surpless, 2019); P2014 (Page et al, 2014); PD2015 (Paterson & Ducea, 2015); RS1988 (Ross & Sharp, 1988); S2010 (Snow et al, 2010); S2011 (Shervais et al, 2011); U2012 (Ukar et al, 2012); WD2007 (Wakabayashi & Dumitru, 2007).…”

Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 99%

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An Exhumation Pulse From the Nascent Franciscan Subduction Zone (California, USA)

et al. 2020

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We investigated a suite of metabasite blocks from serpentinite matrix and shale matrix mélanges of the California Coast Ranges. Our new data set consists of 40 Ar/ 39 Ar dates of amphibole and phengite and U-Pb dates of metamorphic zircon. Combined with published geochronology, including prograde Lu-Hf garnet ages from the same blocks, we can reconstruct the timing and time scales of prograde and retrograde metamorphism of individual blocks. In particular we find that exhumation from amphibole-eclogite facies conditions occurred as a single episode at 165-157 Ma, with an apparent southward younging trend. The rate and timing of exhumation were initially uniform (when comparing individual blocks) and fast (with cooling rates up to~140°C/Ma). In the cooler and shallower blueschist facies, exhumation slowed and became less uniform among blocks. Considering the subduction zone system, the high-grade exhumation temporally correlates with a magmatic arc pulse (Sierra Nevada) and the termination of forearc spreading (Coast Range Ophiolite). Our findings suggest that a geodynamic one-time event led to exhumation of amphibole-eclogite facies rocks. We propose that interaction of the Franciscan subduction zone with a spreading ridge led to extraction of the forearc mantle wedge from its position between forearc crust and subducting crust. The extraction led to fast and uniform exhumation of subducted rocks into the blueschist facies. We also show that the Franciscan subduction zone did not undergo significant cooling over time and that its initiation was not coeval with blueschist-facies metamorphism of the Red Ant schist of the Sierra Nevada foothills. Plain Language Summary A subduction zone is where oceanic crust of one tectonic plate dives under the crust of another plate. These zones are important drivers of the movement of the continental plates. Special rocks-blueschists and eclogites-form in subduction zones at high pressure and relatively low temperature. The Franciscan Complex forms most of the geology of western California. It consists of rocks that dived into a subduction zone and returned back to the surface. We investigated the history of some of these rocks by determining the age and conditions of their movement. We find that the rocks that subducted to depths of up to 80 km all came up at the same time around 160 million years before present. This suggests that a specific tectonic event occurred at that time; other regional data show that the effects of this event were felt elsewhere along the paleo-Pacific margin. We also investigate rocks in the Sierra Nevada foothills that other researchers suggested to have formed at about the same time and found that they are not correlated.

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Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 97%

Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 97%

Section: Geologic Setting: Franciscan Subduction Systemmentioning

confidence: 99%

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An Exhumation Pulse From the Nascent Franciscan Subduction Zone (California, USA)

et al. 2020

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“…Sedimentary strata along convergent margins provide a record of subductionrelated magmatism, oceanic plateau and arc collisional processes, and regional sediment transport pathways (e.g., Dickinson, 1974;Ingersoll, 1979;Plafker and Berg, 1994;Surpless et al, 2014;Stevens Goddard et al, 2018). Recent advances in techniques such as detrital zircon geochronology and Hf isotope analyses have proved insightful for studying the tectonic and sedimentary configuration of ancient convergent margins (Hampton et al, 2010;Yokelson et al, 2015;Reid et al, 2018;Orme and Surpless, 2019). In this study, we applied these techniques to better evaluate the Mesozoic geologic development of the Northern Cordillera.…”

Section: ■ Introductionmentioning

confidence: 99%

Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

2020

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The Jurassic–Cretaceous Nutzotin, Wrangell Mountains, and Wellesly basins provide an archive of subduction and collisional processes along the southern Alaska convergent margin. This study presents U-Pb ages from each of the three basins, and Hf isotope compositions of detrital zircons from the Nutzotin and Wellesly basins. U-Pb detrital zircon ages from the Upper Jurassic–Lower Cretaceous Nutzotin Mountains sequence in the Nutzotin basin have unimodal populations between 155 and 133 Ma and primarily juvenile Hf isotope compositions. Detrital zircon ages from the Wrangell Mountains basin document unimodal peak ages between 159 and 152 Ma in Upper Jurassic–Lower Cretaceous strata and multimodal peak ages between 196 and 76 Ma for Upper Cretaceous strata. Detrital zircon ages from the Wellesly basin display multimodal peak ages between 216 and 124 Ma and juvenile to evolved Hf compositions. Detrital zircon data from the Wellesly basin are inconsistent with a previous interpretation that suggested the Wellesly and Nutzotin basins are proximal-to-distal equivalents. Our results suggest that Wellesly basin strata are more akin to the Kahiltna basin, which requires that these basins may have been offset ~380 km along the Denali fault. Our findings from the Wrangell Mountains and Nutzotin basins are consistent with previous stratigraphic interpretations that suggest the two basins formed as a connected retroarc basin system. Integration of our data with previously published data documents a strong provenance and temporal link between depocenters along the southern Alaska convergent margin. Results of our study also have implications for the ongoing discussion concerning the polarity of subduction along the Mesozoic margin of western North America.

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“…This zonal succession is readily correlated with those found in other Boreal regions (Zakharov, 1981(Zakharov, , 1987, providing a solid biostratigraphic foundation for the age of the GVG. However, results from detrital zircon geochronology (Surpless et al, 2006;Dumitru et al, 2015;Orme and Surpless, 2019), suggest a later, Early Cretaceous, age for the basal GVG, attributing the presence of Tithonian fossils to imprecise correlation or re-deposition. Orme and Surpless (2019) emphasized that "the presence of Buchia, in the absence of other agediagnostic fossils, may not be a reliable age constraint.…”

mentioning

confidence: 99%