A model for recent plate interactions off Canada's west coast

1977 ◽  
Vol 14 (3) ◽  
pp. 384-396 ◽  
Author(s):  
R. P. Riddihough
Keyword(s):  
Fine Structure ◽  
Continental Margin ◽  
Vancouver Island ◽  
Geometrical Model ◽  
Crustal Shortening ◽  
Juan De Fuca ◽  
Lithospheric Plates ◽  
History Of ◽  
Northern Edge ◽  
Spreading Rates

Detailed re-examination of existing magnetic anomaly data reveals the fine structure of variations in spreading rates and directions at the Juan de Fuca and Explorer Ridges during the last 10 million years. A geometrical model using these variations delineates the theoretical history of the interactions between the lithospheric plates involved. These interactions demonstrate the independent movement of the Juan de Fuca and Explorer plates and the development of the Sovanco Fracture Zone. The latter was apparently initiated E–W at 7 Ma, rotated clockwise to 120° and may have been the site of up to 50 km of crustal shortening. The model demonstrates that subduction rates at the Canadian continental margin declined from 5 cm/yr to a present 1.5 cm/yr and that recent relative movements are compatible with the N–S compression observed from earthquakes. It also suggests that the existence of both E–W and NE trending faults in the downgoing lithosphere beneath Vancouver Island, shows that a triple junction remained static near the northern end of Vancouver Island from 10–4 Ma, and predicts a buried northern edge of subducted material striking NE in this area.

Tectonics and Depositional History of the Continental Margin Off Vancouver Island, British Columbia

1972 ◽  
Vol 9 (3) ◽  
pp. 280-296 ◽  
Author(s):  
D. L. Tiffin ◽  
B. E. B. Cameron ◽  
J. W. Murray
Keyword(s):  
Continental Margin ◽  
Deep Water ◽  
Depositional Environment ◽  
Marked Change ◽  
Vancouver Island ◽  
Late Eocene ◽  
Transform Faults ◽  
Depositional History ◽  
Seismic Profiling ◽  
History Of

Sampling and seismic profiling in the Tofino Basin west of Vancouver Island show there is a thick sequence of Tertiary rocks ranging in age from late Eocene to Pliocene. The rocks are mainly mudstones containing abundant foraminifera indicating a bathyal depositional environment throughout most of the Tertiary. Subsequent uplift has exposed the deep water sediments on the shelf over much of the area. Eocene-Oligocene sediments occur in a belt along the inner shelf, while Miocene and Pliocene rocks lie seaward of this. Pliocene rocks form a regressive sequence overlapping the older Tertiary, with the greatest thickness in the south.At least two major periods of deformation resulted in faulting, folding, and diapirism on the continental shelf. Deformational patterns show a marked change from north to south. North of Brooks Peninsula sediments are undeformed by folding but are truncated by faulting along the steep continental slope. The Kyuquot Uplift south of Brooks Peninsula exposes Eocene-Oligocene sediments across the shelf. Farther south Mio-Pliocene sediments unconformably overlie the uplift. Folding increases southward culminating in an area of diapirism off Nootka Sound. Elongate diapirs trend parallel or subparallel to the coastline.Tectonic features on the shelf and slope appear to be related to present and earlier configurations of nearby offshore spreading centers, plates, and transform faults. Crustal plate movements may have been responsible for the observed shelf and slope deformations.

scholarly journals Marine multichannel seismic reflection, gravity and magnetic profiles, Vancouver Island, continental margin and Juan de Fuca Ridge

1987 ◽  
Author(s):  
C J Yorath ◽  
R M Clowes ◽  
R D Macdonald ◽  
C Spencer ◽  
E E Davis ◽  
...  
Keyword(s):  
Continental Margin ◽  
Seismic Reflection ◽  
Vancouver Island ◽  
Juan De Fuca Ridge ◽  
Fuca Ridge ◽  
Gravity And Magnetic ◽  
Multichannel Seismic Reflection ◽  
Juan De Fuca

Seismicity of western Canada

1978 ◽  
Vol 15 (7) ◽  
pp. 1170-1193 ◽  
Author(s):  
W. G. Milne ◽  
G. C. Rogers ◽  
R. P. Riddihough ◽  
G. A. McMechan ◽  
R. D. Hyndman
Keyword(s):  
Puget Sound ◽  
Seismic Energy ◽  
Vancouver Island ◽  
Fault System ◽  
Western Canada ◽  
Juan De Fuca ◽  
Lithospheric Plates ◽  
Strain Release ◽  
Tectonic Features

The seismicity of western Canada has been studied for the period 1899–1975. The quality of the data collected improved through this period as the number of recording stations increased and the location and analysis methods developed, but significant uncertainties and biases remain. Although these restrictions limit detailed correlation of seismic events with specific tectonic features, in general the most active earthquake areas correspond to the boundaries between the major lithospheric plates. These are the Queen Charlotte – Fairweather fault system (Pacific–America plates), the offshore ridge-fracture zone system (Pacific – Juan de Fuca plates), and the Vancouver Island – Puget Sound region (Juan de Fuca – America plates). Strain release calculations show that most seismic energy is released along the Queen Charlotte – Fairweather fault system and that at present a significant accumulation of strain may be available for release as earthquakes in the Vancouver Island – Puget Sound area. Except for the absence of thrust earthquakes along the apparently converging margin, focal mechanisms are in good agreement with the postulated plate motions. The b values in the frequency–magnitude recurrence relation for different areas within the region range from 0.65 to 0.82.

The Vendian-Early Paleozoic History of the Continental Margin of Eastern Paleogondwana, Paleoasian Ocean, and Central Asian Foldbelt

2003 ◽  
Vol 5 (3) ◽  
pp. 165-184 ◽  
Author(s):  
T. N. Kheraskova ◽  
Yu. A. Volozh ◽  
A. N. Didenko ◽  
V. A. Bush
Keyword(s):  
Continental Margin ◽  
Early Paleozoic ◽  
Paleoasian Ocean ◽  
Central Asian ◽  
History Of

Late quaternary sedimentation and glacial history of the western Svalbard continental margin

1996 ◽  
Vol 133 (3-4) ◽  
pp. 123-156 ◽  
Author(s):  
Espen S. Andersen ◽  
Trond M. Dokken ◽  
Anders Elverhøi ◽  
Anders Solheim ◽  
Ingrid Fossen
Keyword(s):  
Continental Margin ◽  
Late Quaternary ◽  
Glacial History ◽  
History Of

A preliminary model for the erosional history of the onshore continental margin of S.E. Brazil

1993 ◽  
Vol 21 (4) ◽  
pp. 588
Author(s):  
Kerry Gallagher ◽  
Chris Hawkesworth ◽  
Cherry Lewis ◽  
Marta Mantovani
Keyword(s):  
Continental Margin ◽  
Preliminary Model ◽  
History Of

Paleozoic formations of the Northeast margin of the European platform

2006 ◽  
Author(s):  
A. I. Eliseev ◽  
◽  
A. I. Antoshkina ◽  
V. A. Saldin ◽  
N. Yu. Nikulova ◽  
...  
Keyword(s):  
Continental Margin ◽  
Sedimentary Basins ◽  
Passive Continental Margin ◽  
European Continent ◽  
History Of ◽  
Geodynamic Reconstructions

Paleozoic sedimentary basins of the northeast European Platform is a component of large megabasin of the northeast passive continental margin of the European continent in the Paleozoic. The establishment of a connection between a paleodynamic history of a basin and its sedimentary formations types, which are the most reliable indicators of geodynamic conditions, is one of the primary problems of modern lithology. Reliable indicators at geodynamic reconstructions are genetically predetermined by laterial and vertical lines of the sedimentary formations. Formations and lithological complexes being the brightest indicators of the paleodynamic regimes change of the basin have been considered formations lines of the passive continental margin of the westuralian type during the Paleozoic.

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