Deep-crustal metasedimentary rocks support Late Cretaceous “Mojave-BC” translation

Sauer, Kirsten; Gordon, Stacia M.; Miller, Robert B.; Jacobson, Carl E.; Grove, Marty; Vervoort, Jeffrey D.; Fisher, Colleen

doi:10.1130/g45554.1

Cited by 11 publications

(37 citation statements)

References 31 publications

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“…In the Mojave-Salinia region, these schists, referred to as the Pelona-Orocopia-Rand-Salinas schists (Grove et al, 2003), have the same time-dependent provenance signature as coeval sediment that was supplied to the southern California forearc margin (Jacobson et al, 2011). Sauer et al (2019) measured the detrital zircon U-Pb and Hf isotopic properties of a suite of Pelona-Orocopia-Rand-Salinas schist samples from the Mojave-Salinian margin and concluded that the schists' detrital zircon U-Pb ages and Hf isotopic properties were indistinguishable from equivalent schists (Swakane Gneiss) that were underthrust beneath the North Cascades arc during the Late Cretaceous. Sauer et al (2019) further correlated sediment entrained within the western mélange belt beneath the western Cascades thrust system (Sauer et al, 2017) with both the Swakane Gneiss and the extraregional sediment contained within the Nanaimo basin.…”

Section: Relationship To the Source Of The Extraregional Sediment In The Nanaimo Basinmentioning

confidence: 99%

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

et al. 2021

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Detrital K-feldspar 40Ar/39Ar thermochronology was conducted on clastic sedimentary rock samples collected from northern exposures of the Upper Cretaceous Nanaimo Group on Vancouver Island and adjacent Gulf Islands of British Columbia to constrain the denudation history of the local Coast Mountains batholith source region and determine the origin of extraregional sediment supplied to the basin. Strata of the northern Nanaimo Group deposited between 86 and 83 Ma (Comox and Extension formations) exhibit a 130–85 Ma age distribution of detrital K-feldspar 40Ar/39Ar ages that lack age maxima. These are interpreted to have been sourced from the southwestern Coast Mountains batholith. Younger strata deposited between 83 and 72 Ma (Cedar District and De Courcy formations) yield a broader age range (150–85 Ma) with an age maximum near the depositional age. These results indicate focused denudation of deeper-seated rocks east of the Harrison Lake fault. The youngest units deposited after 72 Ma (Geoffrey, Spray, and Gabriola formations) primarily yield younger than 75 Ma detrital K-feldspar ages with pronounced age maxima near the depositional age. This sediment was sourced extraregionally relative to the Coast Mountains batholith. We sought to constrain the origin of the extraregional sediment by measuring the thermal histories of 74 samples of basement rocks from throughout the Pacific Northwest, and by compiling a database of over 2400 biotite 40Ar/39Ar and K/Ar cooling ages from predominantly Cretaceous batholiths along the western North American margin. This analysis focused upon two previously proposed source regions: the Idaho batholith and the Mojave-Salina margin of southern California. The Nanaimo detrital K-feldspar 40Ar/39Ar age distributions favor the peraluminous Late Cretaceous Idaho batholith and its Proterozoic Belt-Purcell Supergroup sedimentary wall rock as the more likely source of the extraregional sediment and disfavor the Baja–British Columbia hypothesis for 2000–4000-km-scale translation of rocks along the margin during the Late Cretaceous.

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Section: Relationship To the Source Of The Extraregional Sediment In The Nanaimo Basinmentioning

confidence: 99%

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

et al. 2021

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“…The mechanism for burial of the Swakane Gneiss to lower-crustal depths (~40 km) (Valley et al, 2003;Matzel et al, 2004) is uncertain, and both underplating of trench sediments to the base of the CCC and underthrusting of a forearc region under or into the CCC have been proposed (Matzel et al, 2004;Sauer et al, 2018). Sauer et al (2019) demonstrated that the Swakane Gneiss had very similar isotopic properties (e.g., U-Pb and Lu-Hf) to well-studied underplated schists exposed in California, suggesting that underplating may have occurred. However, clockwise P-T pathways (Valley et al, 2003;Matzel et al, 2004), and ongoing local magmatism (Miller et al, 2009), neither of which are found in the Californian schists, support an underthrusting mechanism.…”

Section: Stratigraphic Record Of Sediment Underplatingmentioning

confidence: 99%

“…The Kula-Farallon ridge is interpreted to have formed south of the Nanaimo basin (Woods and Davies, 1982;Engebretson et al, 1985;Doubrovine and Tarduno, 2008;Seton et al, 2012). However, if the Nanaimo basin, as a part of the Baja-BC Block, was located at the latitude California during the Late Cretaceous (e.g., Housen and Beck, 1999;Sauer et al, 2019), then the Kula-Farallon ridge was located in southern California or northern Mexico at 85 Ma. This position of the ridge is consistent with oceanic plate reconstructions proposed by Engebretson et al (1985); however, this is inconsistent with paleogeographic models for the southwestern North America during the Late Cretaceous (Jacobson et al, 2011;Sharman et al, 2015;Yonkee and Weil, 2015), which generally favors a higher latitude for both the Baja-BC block and the Kula-Farallon ridge north of California in the latest Cretaceous.…”

Section: Paleogeography Of the Southern Insular Superterrane During Tmentioning

confidence: 99%

Along-strike variations in sediment provenance within the Nanaimo basin reveal mechanisms of forearc basin sediment influx events

et al. 2020

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The along-strike variability in sediment provenance within the Nanaimo basin is important for understanding the tectonic evolution of North America’s Late Cretaceous Pacific margin, providing context for paleogeographic reconstructions. Here, we provide 35 point-counted sandstone samples and 22 new detrital zircon samples from the Nanaimo basin. These new detrital zircon samples compose a portion of a basin-wide data set (N = 49, n = 10,942) that is leveraged to discern spatio-temporal changes in sediment provenance. Provenance data demonstrates that the majority of Nanaimo basin strata were sourced from regions within and east of the Coast Mountains Batholith, while only the southernmost Nanaimo basin, exposed in the San Juan Islands, was supplied sediment from the North Cascade thrust system. Additionally, near-identical age modes and synchronous changes in detrital zircon facies are used to hypothesize a correlation between the Nanaimo Group and the protolith of the Swakane Gneiss. These observations, along with previously identified events in the Cordillera, are used to define two basin-wide events that affected the Nanaimo basin: the first at 84 Ma and the second at 72 Ma. The first event is correlated to the onset of Kula-Farallon spreading, which affected basin subsidence, introduced Proterozoic detrital zircon to the central and southern Nanaimo basin, and uplifted the North Cascade thrust system. The second basin-wide event, which is speculated to have been driven by increased rates of subduction and obliquity, resulted in localized high-flux events in the arc, increased exhumation of the Cascade Crystalline Core, underplating of the Swakane Gneiss, and coarse-grained sedimentation across the basin. The data presented here provides added context for the evolution of the basin and provides insight into the protracted geodynamics of forearc basins undergoing oblique subduction.

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“…Its location relative to other segments of the Cretaceous arc in North America is debated. It has been proposed that it comprises a back-arc segment of the Coast Mountains batholith; however, a recent study by Sauer et al (2019) indicates that the Cascades Core (or at least sedimentary units of it) comprises a fore-arc segment of the Sierra Nevada arc translated northward by margin-parallel displacement (Baja-BC hypothesis). Present-day exposure of the Cascades Core comprises a corridor of~90-km width and exposes intrusive rocks emplaced from~5-to 35-km depth.…”

Section: Cascades Crystalline Core Washington State Usamentioning

confidence: 99%

Spatial and Depth‐Dependent Variations in Magma Volume Addition and Addition Rates to Continental Arcs: Application to Global CO₂ Fluxes since 750 Ma

Ratschbacher

Paterson

Fischer

2019

Geochem Geophys Geosyst

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Magma transfer from the mantle to the crust in arcs is an important step in the global cycling of elements and volatiles from Earth's interior to the atmosphere. Arc intrusive rocks dominate the total magma mass budget over extrusive rocks. However, their total volume and rate of addition is still poorly constrained, especially in continental arcs. We present lateral (forearc to backarc) and depth‐dependent (volcanics to deep crust) magma volume additions and arc‐wide magma addition rates (MARs) calculated from three continental arc crustal sections preserving magma flare‐up periods. We observe an increase in volume addition with depth and less magma added in the forearc (~15%) and backarc (~10% to 30%) compared to the main arc. Crustal‐wide MARs for each section are remarkably similar and around 0.7–0.9 km3/km2/Ma. MARs can be used to estimate CO2 fluxes from continental arcs. With initial magma CO2 contents of 1.5 wt.%, global continental arc lengths, and MARs, we calculate changes in C (Mt/year) released from continental arcs since 750 Ma. Calculated present‐day global C fluxes are similar to values constrained by other methods. Throughout the Phanerozoic, assuming equal durations of flare‐up and lull magmatism, calculated continental CO2 flux rates vary between 4 and 18 Mt C/year with highest values in the Mesozoic. These fluxes are considered minima since the intake of mantle and/or crustal carbon is not considered. Magmatic episodicity in continental arcs and changes in arc thickness and width are critical to consider when calculating MARs through time.

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Deep-crustal metasedimentary rocks support Late Cretaceous “Mojave-BC” translation

Cited by 11 publications

References 31 publications

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

Along-strike variations in sediment provenance within the Nanaimo basin reveal mechanisms of forearc basin sediment influx events

Spatial and Depth‐Dependent Variations in Magma Volume Addition and Addition Rates to Continental Arcs: Application to Global CO₂ Fluxes since 750 Ma

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Deep-crustal metasedimentary rocks support Late Cretaceous “Mojave-BC” translation

Cited by 11 publications

References 31 publications

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

Along-strike variations in sediment provenance within the Nanaimo basin reveal mechanisms of forearc basin sediment influx events

Spatial and Depth‐Dependent Variations in Magma Volume Addition and Addition Rates to Continental Arcs: Application to Global CO2 Fluxes since 750 Ma

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Spatial and Depth‐Dependent Variations in Magma Volume Addition and Addition Rates to Continental Arcs: Application to Global CO₂ Fluxes since 750 Ma