The Neoproterozoic succession of the central Rocky Mountains, Canada

McMechan, M E

doi:10.2113/gscpgbull.63.3.243

Cited by 11 publications

(2 citation statements)

References 46 publications

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“…The Windermere Supergroup (WSG) is an unconformity‐bounded, 2 to 9 km thick Neoproterozoic (740·0 to 569·9 Ma) succession of syn‐rift and post‐rift sedimentary rocks associated with the break‐up of Rodinia (McMechan, ). In outcrop, the WSG extends for over 4000 km from the Yukon–Alaska border to north‐western Mexico (Ross & Arnott, ).…”

Section: Geological Settingmentioning

confidence: 99%

Lateral and vertical juxtaposition of matrix‐rich and matrix‐poor lithologies caused by particle settling in mixed mud–sand deep‐marine sediment suspensions

2018

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Sandy sedimentary rocks rich in detrital matrix (>10% silt/clay) have long been recognized in the ancient sedimentary record, and nowhere more commonly than in deep-marine turbidite systems. Despite this, their depositional mechanisms remain poorly understood, in part because these rocks, which are enriched in fine-grained sediment, are often poorly exposed in outcrop or are confined to observation in core. Matrix-rich strata in the Neoproterozoic Windermere Supergroup, in contrast, are very well-exposed and show systematic changes in lithofacies over distances of several tens to a few hundreds of metres along-strike. Notably, these strata are observed in both basin floor and continental slope deposits, suggesting that their occurrence and systematic lithological arrangement is related to mechanistic, rather than palaeogeographic, controls. Specifically, the facies transect consists of structureless, clayey sandstone that transforms along-strike to a two-layer deposit with the development of an upper, planar-based, markedly more matrix-rich layer. Further along-strike, the basal clayey sandstone thins and eventually pinches out, leaving only the (upper) sandy claystone layer, which in turn thins along-strike and then pinches out. These systematic changes in lithology, but more specifically the distribution of clay, is interpreted to form a depositional continuum related to particle settling in a horizontally advecting, high concentration particle suspension formed along the margins of an avulsion-related high-energy turbulent suspension.Keywords Deep-marine, deposit stratification, flow avulsion, greywacke, hybrid bed, matrix-rich sandstone, particle settling. Hise (1892), and later advanced by several authors, the matrix has been interpreted to be the authigenic alteration of labile detrital grains, 940

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Section: Geological Settingmentioning

confidence: 99%

Lateral and vertical juxtaposition of matrix‐rich and matrix‐poor lithologies caused by particle settling in mixed mud–sand deep‐marine sediment suspensions

2018

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“…Transverse faults that are coeval with deposition of the Windermere Supergroup are recognized in the SCC, such as the St Mary-Moyie fault zone near the Canada-U.S. border that demarcates the southern limit of the deep marine outcrop belt [45]. Moreover, profound facies changes within the Windermere Supergroup occur across other transverse faults in the SCC providing further evidence of syndepositional fault activity [46,47]. At a continental scale, the SW-NE faults are interpreted as initial rift and then continental margin segments with transform boundaries that separated upper and lower divergent plate boundaries (e.g., [1]).…”

Section: Introductionmentioning

confidence: 99%

Provenance of the Incipient Passive Margin of NW Laurentia (Neoproterozoic): Detrital Zircon from Continental Slope and Basin Floor Deposits of the Windermere Supergroup, Southern Canadian Cordillera

et al. 2021

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The origin of the passive margin forming the paleo-Pacific western edge of the ancestral North American continent (Laurentia) constrains the breakup of Rodinia and sets the stage for the Phanerozoic evolution of Laurentia. The Windermere Supergroup in the southern Canadian Cordillera records rift-to-drift sedimentation in the form of a prograding continental margin deposited between ~730 and 570 Ma. New U-Pb detrital zircon analysis from samples of the post-rift deposits shows that the ultimate source area was the shield of NW Laurentia and the near uniformity of age spectra are consistent with a stable continental drainage system. No western sediment source area was detected. Detrital zircon from postrift continental slope deposits are a proxy for ca. 676-656 Ma igneous activity in the Windermere basin, likely related to continental breakup, and set a maximum depositional age for slope deposits on the eastern side of the basin at 652±9 Ma. These results are consistent with previous interpretations. The St. Mary-Moyie fault zone near the Canada-U.S. border was most likely a major transform boundary separating a rifted continental margin to the north from intracratonic rift basins to the south, resolving north-south variations along western Laurentia in the late Neoproterozoic at approximately 650-600 Ma. For Rodinia reconstructions, the conjugate margin to the southern Canadian Cordillera would have a record of rifting between ~730 and 650 Ma followed by passive margin sedimentation.

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The origin of planar lamination in fine‐grained sediment deposited by subaqueous sediment gravity flows

Al‐Mufti,

Arnott

2023

The Depositional Record

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Planar lamination is a ubiquitous component of modern and ancient fine‐grained sediments deposited by subaqueous sediment gravity flows. These sediments commonly exhibit alternating sub‐millimetre‐thick, sharply bounded silt‐rich and clay‐rich layers that change little in thickness or sediment texture over lateral distances that range up to at least several tens of metres. Silt‐rich layers are moderately to well‐sorted and a few tens to hundreds of microns to a single silt‐grain thick. In contrast, clay‐rich layers are more poorly sorted, and a few tens to hundreds of microns thick. The thickness and regular alternation of these texturally differentiated interlayers, in addition to the absence of features suggesting transport bypass or deposition by migrating rugged bed forms, suggest alternating physical processes and related modes of deposition in the near‐bed region immediately above the bed. Previous interpretations have focussed on clay flocculation, which is difficult to reconcile with the high fluid shear conditions in the near‐bed region. Here it is suggested that in the millimetre to sub‐millimetre‐thick viscous sublayer at the base of a hydraulically smooth turbulent flow, a combination of high fluid shear and sediment concentration initially leads to shear thinning and enhanced mobility in the lower part of the flow, and for silt to continue settling to the bed forming a well‐sorted silt lamina. As silt settles and clay‐size sediment increases in concentration, hydrodynamic lubrication forces strengthen and reduce mobility of the near‐bed part of the flow. This condition is then perturbed by a bedward‐directed outer flow disturbance that dramatically increases frictional stresses and effective fluid viscosity and ultimately shear jamming that causes gelling and deposition of a poorly sorted clay‐rich layer. This process is then repeated multiple times to build up a deposit composed of alternating silt‐rich and clay‐rich laminae overlain by structureless mud deposited directly from suspension.

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The Neoproterozoic succession of the central Rocky Mountains, Canada

Cited by 11 publications

References 46 publications

Lateral and vertical juxtaposition of matrix‐rich and matrix‐poor lithologies caused by particle settling in mixed mud–sand deep‐marine sediment suspensions

Lateral and vertical juxtaposition of matrix‐rich and matrix‐poor lithologies caused by particle settling in mixed mud–sand deep‐marine sediment suspensions

Provenance of the Incipient Passive Margin of NW Laurentia (Neoproterozoic): Detrital Zircon from Continental Slope and Basin Floor Deposits of the Windermere Supergroup, Southern Canadian Cordillera

The origin of planar lamination in fine‐grained sediment deposited by subaqueous sediment gravity flows

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