scholarly journals Surficial geology of the Vancouver Island continental shelf, Nootka Sound to Strait of Juan de Fuca, offshore British Columbia

1992 ◽  
Author(s):  
K W Conway ◽  
J V Barrie ◽  
B D Bornhold
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Vancouver Island ◽  
Surficial Geology ◽  
Juan De Fuca

Late Pleistocene history and geomorphology, southwestern Vancouver Island, British Columbia

1979 ◽  
Vol 16 (9) ◽  
pp. 1645-1657 ◽  
Author(s):  
Neville F. Alley ◽  
Steven C. Chatwin
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Late Pleistocene ◽  
Vancouver Island ◽  
Glacial Lakes ◽  
Small Lakes ◽  
Strait Of Georgia ◽  
Coast Mountains ◽  
Juan De Fuca ◽  
Juan De Fuca Strait

The major Pleistocene deposits and landforms on southwestern Vancouver Island are the result of the Late Wisconsin (Fraser) Glaciation. Cordilleran glaciers formed in the Vancouver Island Mountains and in the Coast Mountains had advanced down Strait of Georgia to southeastern Vancouver Island after 19 000 years BP. The ice split into the Puget and Juan de Fuca lobes, the latter damming small lakes along the southwestern coastal slope of the island. During the maximum of the glaciation (Vashon Stade), southern Vancouver Island lay completely under the cover of an ice-sheet which flowed in a south-southwesterly direction across Juan de Fuca Strait, eventually terminating on the edge of the continental shelf. Deglaciation was by downwasting during which ice thinned into major valleys and the strait. Most upland areas were free of ice down to an elevation of 400 m by before 13 000 years BP. A possible glacier standstill and (or) resurgence occurred along Juan de Fuca Strait and in some interior upland valleys before deglaciation was complete. Glacial lakes occupied major valleys during later stages of deglaciation.

A Review of Geophysical Studies in the Canadian Cordillera

1971 ◽  
Vol 8 (7) ◽  
pp. 788-801 ◽  
Author(s):  
M. J. Berry ◽  
W. R. Jacoby ◽  
E. R. Niblett ◽  
R. A. Stacey
Keyword(s):  
British Columbia ◽  
Heat Flow ◽  
Rocky Mountain ◽  
The United States ◽  
Vancouver Island ◽  
Geophysical Data ◽  
Fault System ◽  
Canadian Cordillera ◽  
Crust And Upper Mantle ◽  
Juan De Fuca

Geophysical studies of the crust and upper mantle have been conducted in the Canadian Cordillera for over two decades, but only recently have sufficient data been collected to permit a synthesis and a correlation with the major geological units. The studies have included gravity, heat flow, and magnetotelluric observations, geomagnetic depth sounding, and high level aeromagnetics as well as both small and large scale refraction and reflection seismic surveys.It now appears that major crustal units may be recognized geophysically:(i) Seismic and gravity data suggest that the Plains and Rocky Mountains are underlain by two units of the North American craton with a crustal section 45–50 km thick. The northern unit appears to terminate at the Rocky Mountain Trench while the southern unit may extend to the Omineca Geanticline.(ii) The combined geological and geophysical data suggest that the Rocky Mountain Trench and possibly the Kootenay Arc near the 49th parallel mark the edge of the Precambrian continental margin and that the western Cordillera was formed by a complex succession of plate interactions with repeated reactivation of block boundaries.(iii) A combination of magnetic and heat flow data suggest that the region between the Rocky Mountain Trench and the Fraser Lineament is part of the Cordilleran Thermal Anomaly Zone recognized by Blackwell in the United States.(iv) Seismic data in Central British Columbia suggest that the Pinchi Fault system is a boundary between two crustal blocks.(v) The crustal thickness of the Coast Geanticline appears to increase gradually to the west to approximately 40 km and, at least in southern British Columbia, does not have a root zone below the mountains.(vi) The crustal section beneath Vancouver Island is abnormally thick and there is some paleomagnetic data which suggest that the Island may not have been formed in its present position, contiguous to the Cordillera. The crustal section for the northern part of the Insular Trough is significantly thinner.(vii) The active spreading of the Juan de Fuca Rise – Explorer Trench is now well documented. The geophysical data suggest active subduction of the Juan de Fuca plate beneath Oregon, Washing-ton, and southern Vancouver Island. However, further north there is no evidence for subduction.

Distribution of Nitzschia pungens in Coastal Waters of British Columbia

1991 ◽  
Vol 48 (6) ◽  
pp. 960-967 ◽  
Author(s):  
J. R. Forbes ◽  
K. L. Denman
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Coastal Waters ◽  
Domoic Acid ◽  
Pacific Coast ◽  
Minor Component ◽  
Vancouver Island ◽  
Large Diatom ◽  
A Minor ◽  
Nitzschia Pungens

Concern about the potential for contamination of Pacific coast molluscan shellfish by domoic acid prompted us to review the distribution of Nitzschia pungens in coastal waters of British Columbia. From 1980 to 1988, N. pungens occurred throughout waters of the continental shelf, most frequently as a minor component of the large diatom aggregations observed off southwest Vancouver Island during July and August. The species was less common in the Strait of Georgia and north of Vancouver Island, but interannual variability in distribution and abundance was considerable. Maximum concentrations recorded were 106 cells∙L−1 in Hecate Strait in July 1983 and 5 × 105 cells∙L−1 off southwest Vancouver Island in August 1986. Discrimination of presence or absence on the basis of existing environmental variables produced mixed results, but has potential. Scanning electron microscopy showed that both N. pungens f. pungens and N. pungens f. multiseries (the latter being implicated in the contamination of shellfish in Atlantic Canada) occur in British Columbia. It remains to be shown whether N. pungens produces domoic acid in Pacific coast waters and whether the high abundances observed over the continental shelf also occur near shore.

Surficial geology of Hecate Strait, British Columbia continental shelf

1989 ◽  
Vol 26 (6) ◽  
pp. 1241-1254 ◽  
Author(s):  
J. V. Barrie ◽  
B. D. Bornhold
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Glacial Till ◽  
Hydrodynamic Conditions ◽  
Surficial Geology ◽  
Sand Ridges ◽  
Late Tertiary ◽  
Drainage Channels ◽  
Late Wisconsinan ◽  
Geological Units

Four surficial geological units are defined geophysically for Hecate Strait on the northern British Columbia continental shelf. They consist of Tertiary bedrock (unit 1) unconformably overlain in much of the strait of glacial till (unit 2), which is in turn overlain below 200 m water depth by thick silts (unit 4) and above 200 m by Quaternary sands and gravels (unit 3), except in areas where till or Tertiary bedrock is at or near surface.Glacial ice covered most of the strait at some time in the Pleistocene, but evidence for a Late Wisconsinan advance is more prevalent in the principal troughs of the strait. Sea level was as low as the present-day 180 m isobath during the late Tertiary or early Quaternary and possibly as low as 100 m at the end of the Pleistocene, based on the presence of drainage channels, wave-cut terraces, and both shore-oblique and shore-parallel sand ridges. Sedimentary bedforms found ubiquitously above 100 m appear to be in equilibrium with the present hydrodynamic conditions, and their presence suggests that significant seabed erosion and transport occur within the strait.

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