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.

New conodont records of the Los Sombreros Formation (Cambrian–Ordovician) from the Western Precordillera, Argentina: biostratigraphic and palaeoenvironmental implications

2019 ◽  
Vol 157 (4) ◽  
pp. 539-550
Author(s):  
Gabriela Torre ◽  
Guillermo L. Albanesi
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
South American ◽  
The South ◽  
Depositional History ◽  
The Matrix ◽  
Minimum Age ◽  
History Of ◽  
Lower Palaeozoic ◽  
Early Palaeozoic

AbstractThe presence of a carbonate platform that interfingers towards the west with slope facies allows for the identification of an ancient lower Palaeozoic continental margin in the Western Precordillera of Argentina. The Los Sombreros Formation is essential for the interpretation of the continental slope of the Precordillera, which accreted to Gondwana as part of the Cuyania Terrane in the early Palaeozoic. The age of these slope deposits is controversial; therefore, a precise biostratigraphic scheme is critical to reveal the evolution of the South American continental margin of Gondwana. The study of lithic deposits of two sections of the Los Sombreros Formation, the El Salto and Los Túneles sections, provides important information for further understanding the depositional history of the slope. At El Salto section, the conodonts recovered from an allochthonous block refer to the Cordylodus proavus Zone (upper Furongian). The conodonts recovered from the matrix of a calclithite bed of the Los Sombreros Formation in the Los Túneles section are assigned to the Lenodus variabilis Zone (early Darriwilian), providing a minimum age for this stratigraphic unit. In addition, clasts from this sample yielded conodonts from the Paltodus deltifer − Macerodus dianae zones (upper Tremadocian). The contrasting conodont colour alterations and preservation states from the elements of two latter records, coming from the same sample, argue the reworked clasts originated in the carbonate platform and later transported to the slope during the accretion process of the Precordilleran Terrane to the South American Gondwanan margin during the Middle–Late Ordovician.

Seismostratigraphy and Neogene-Recent depositional history of the south central continental margin of Cyprus

1993 ◽  
Vol 10 (5) ◽  
pp. 426-438 ◽  
Author(s):  
Jean E. McCallum ◽  
Roger A. Scrutton ◽  
Alastair H.F. Robertson ◽  
William Ferrari
Keyword(s):  
Continental Margin ◽  
The South ◽  
Depositional History ◽  
South Central ◽  
History Of ◽  
History Of The South

Evolution of the Pacific Margin, Vancouver Island, and adjacent regions

1977 ◽  
Vol 14 (9) ◽  
pp. 2062-2085 ◽  
Author(s):  
J. E. Muller
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Upper Jurassic ◽  
Vancouver Island ◽  
Late Eocene ◽  
Volcanic Arc ◽  
Late Mesozoic ◽  
Clastic Sediments ◽  
The Pacific ◽  
Uplift And Erosion

The tectonic–stratigraphic evolution of Vancouver Island, a part of the Insular Belt, is reviewed as it relates to the other major tectonic belts recognized in the western Cordillera of Canada and the adjacent United States. The Pacific Belt, recognized south of the international border, is also identified in the west and south of the island. Oldest rocks of the Insular Belt are a late Paleozoic volcanic arc terrane and a crystalline 'basement' that is probably pre-Devonian. A thick Upper Triassic succession of tholeiitic pillow lavas and flows, overlain by carbonate–clastic sediments, rests in part on the Paleozoic. Elsewhere the tholeiite may represent oceanic floor, perhaps formed when the Insular Belt was fragmented and rifted off the continental margin far to the south. Above it the Early Jurassic volcanic arc with related batholiths may have been aligned with a similar terrane in the Intermontane Belt before the two belts assumed parallel positions in late Mesozoic time. An Upper Jurassic – Lower Cretaceous westward thickening clastic wedge indicates uplift and erosion of the volcanic arc in late Mesozoic time. Further west the 'inner Pacific Belt' of Jura-Cretaceous elastics and chert represent slope and trench deposits that have been deformed to mélange or converted to schist. They are coeval and homologous to Franciscan and Chugach Terranes and probably mark the late Mesozoic trench and subduction zone along the continental margin. The Coast Plutonic Belt represents the related volcanic arc, and pre-Cretaceous Insular Belt rocks, unconformably overlain by Cretaceous clastic sediments, represent the arc–trench gap and fore-arc basin. Until Late Cretaceous time convergence of the Insular and Pacific Belts occurred along San Juan Fault. In early Tertiary time Eocene oceanic basalt (Outer Pacific Belt) and Jura-Cretaceous metasediments (Inner Pacific Belt) converged by under-thrusting and (or) strike–slip faulting along Leech River Fault. In Late Eocene time the trench and subduction zone shifted westward to the present core zone of the Olympic Mountains and shifted again in Miocene time to its present position.

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.

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