Pleistocene reversal of the Fraser River, British Columbia

Andrews, Graham; Russell, James K.; Brown, Sarah; Enkin, Randolph J.

doi:10.1130/g32488.1

Cited by 20 publications

(20 citation statements)

References 23 publications

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“…East of the NFZ individual canyons have fed sediments to the abyssal plain, but no channels are evident in the bathymetry. Distal flow from the Nitinat fan (Andrews et al, ; Underwood et al, ) may have reached this far west after its initiation at 0.76 Ma.…”

Section: Regional Geologic and Tectonic Settingmentioning

confidence: 99%

Initiation of Strike‐Slip Faults, Serpentinization, and Methane: The Nootka Fault Zone, the Juan de Fuca‐Explorer Plate Boundary

Rohr

Furlong

Riedel

2018

Geochem Geophys Geosyst

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The Nootka fault zone is a ridge‐trench‐trench transform fault that was initiated ~4 Ma when the Explorer ridge became independent of the Juan de Fuca ridge. Multibeam data around the fault zone and a compilation of several seismic reflection surveys provide insight into initiation of strike‐slip faults. Previous interpretations assumed that the two faults seen cutting the seafloor are subparallel to shear between the Explorer and Juan de Fuca plates and formed instantaneously at 4 Ma. Increased data density shows that these faults are subparallel to seafloor magnetic anomalies and appear to have utilized extensional faults formed at the ridge. They are surrounded by numerous buried steeply dipping, small‐offset growth faults; at least some of which are likely still active. Our observations corroborate analogue models of strike‐slip fault initiation that predict formation of Riedel‐like shears within a zone of faulting and that displacement localizes over time. The existence of several long subparallel faults and a very wide zone of faulting has been predicted by models of distributed shear at depth. Along the Nootka fault zone basement has risen by several hundred meters and bright reversed‐polarity reflectors some of which are interpreted to be methane hydrate reflectors are common. Hydration, likely as serpentinization, of the upper mantle could explain both sets of observations: Serpentinization can result in a 30–50% volume expansion and methane is observed in vents driven by this process. Biogenic sources of methane are likely to be present and concentrated by currently active fluid flow in the faulted sediments.

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Section: Regional Geologic and Tectonic Settingmentioning

confidence: 99%

Initiation of Strike‐Slip Faults, Serpentinization, and Methane: The Nootka Fault Zone, the Juan de Fuca‐Explorer Plate Boundary

Rohr

Furlong

Riedel

2018

Geochem Geophys Geosyst

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“…A number of meandering channels originate from the apex of Nitinat fan. The fan was initiated 0.76 Ma ago (Andrews et al, 2012) when the previous northward flow of the Fraser river was reversed and diverted to the Pacific Ocean.…”

Section: Regional Geologymentioning

confidence: 99%

“…Su et al (2000) identified 11 biostratigraphic events in the Pleistocene by appearance or disappearance of key microfossils and computed average deposition rates for each interval between those events. In Site 1027 the 0.76 Ma horizon, onset of Nitinat fan deposition (Andrews et al, 2012), lies within subunit IB. Above it silty turbidites were deposited more frequently (Shipboard Scientific Party, 1997b); earlier silty turbidites could be distal flows from the Astoria fan, which is thought to have been active throughout the Quaternary (Prytulak et al, 2006).…”

Section: Regional Geologymentioning

confidence: 99%

“…Between 0.9 and 0.76 Ma the deposition rate accelerated to 740 m/Ma; no explanation has been offered for this anomaly (Su et al, 2000). The oldest possible age of initiation of the Nitinat fan is 1.06 Ma based on a date of volcanic dams across the Fraser River (Andrews et al, 2012). As the new river excavated a new bed, if not established an equilibrium profile, it may have resulted in such very high deposition rates on the seafloor.…”

Section: Sediment Thickness and Deposition Ratesmentioning

confidence: 99%

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From mid-plate to subduction zone: stratigraphy of the northeast Juan de Fuca Plate, offshore British Columbia

Rohr

King

Riedel

et al. 2019

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“…This pulse of erosion is also propagated upstream through both the captured and original river basins. Few studies have quantified the rates and magnitudes of fluvial erosion associated with river capture events [e.g., Gunnell and Harbor, 2010;Schlunegger and Mosar, 2011;Prince et al, 2011;Andrews et al, 2012;Brocard et al, 2012], and we are not aware of studies that have explored the implications of drainage capture for landscape evolution with a numerical model.…”

Section: Introductionmentioning

confidence: 99%

High magnitude and rapid incision from river capture: Rhine River, Switzerland

et al. 2013

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[1] Landscape evolution is controlled by the development and organization of drainage basins. As a landscape evolves, drainage reorganization events can occur via river capture or piracy, whereby one river basin grows at the expense of another. The river downstream of a capture location will generate a transient topographic response as the added water discharge increases sediment transport and erosion efficiency. This erosional response will propagate upstream through both the captured and original river basins. Here we focus on quantifying the impact of drainage reorganization along the Rhine/Aare River system (~45,000 km 2 ) during the late Pliocene/early Pleistocene, where gravel remnants indicate total incision of~650 m during the last~4.2 Myr in the region of the recent Aare-Rhine confluence. We develop a numerical model of drainage capture to quantify the range of possible magnitudes of erosion and the transient river response resulting from the reorganization of the Rhine River. The model accounts for both fluvial incision and sediment transport. Our model estimates 400-800 m of river elevation change (lowering profiles) during the last~4 Myr due to river capture events, providing an important component to the recent exhumation budget of the Swiss Alpine Foreland. The model indicates a rapid response to capture events (re-equilibration timescale of~1 Myr). The predicted incision magnitudes are consistent with incision measured from the elevation of Pliocene and early Pleistocene river gravels, suggesting that across northern Switzerland, a significant amount of incision can be explained by drainage reorganization.

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Pleistocene reversal of the Fraser River, British Columbia

Cited by 20 publications

References 23 publications

Initiation of Strike‐Slip Faults, Serpentinization, and Methane: The Nootka Fault Zone, the Juan de Fuca‐Explorer Plate Boundary

Initiation of Strike‐Slip Faults, Serpentinization, and Methane: The Nootka Fault Zone, the Juan de Fuca‐Explorer Plate Boundary

From mid-plate to subduction zone: stratigraphy of the northeast Juan de Fuca Plate, offshore British Columbia

High magnitude and rapid incision from river capture: Rhine River, Switzerland

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