Magnetic susceptibility measurements and sample locations of granitic rocks from along a transect of the coast mountains near Juneau, Alaska

Model of evolution of the Bella Coola – Ocean Falls Region, Coast Mountains, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e68-142 ◽

1968 ◽

Vol 5 (6) ◽

pp. 1429-1441 ◽

Cited By ~ 3

Author(s):

A. J. Baer

Keyword(s):

British Columbia ◽

Granitic Rocks ◽

Coast Mountains ◽

Early Tertiary ◽

Upper Paleozoic ◽

Late Tertiary ◽

Bella Coola

Granitic rocks and metavolcanics underlie most of the Coast Mountains of British Columbia between the fifty-second and the fifty-third parallel, about half-way between Vancouver and Prince Rupert. The age of most rocks is unknown. The area has been involved in at least two orogenic cycles. The oldest known supracrustal rocks (Upper Paleozoic?) have been metamorphosed to gneisses, deformed along northeasterly trends, and intruded by granitic plutons, probably early in the Mesozoic Era. These rocks formed the basement of disconformable Mesozoic sediments and volcanics. The basement and its Mesozoic cover were metamorphosed and deformed along northwesterly trends in the early Tertiary. In the late Tertiary (Pliocene?) post-kinematic granites were emplaced and basalts were extruded for a period extending to postglacial times. The model is possibly applicable to all of the Coast Mountains in Canada.

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A northern Cordilleran ocean–continent transect: Sitka Sound, Alaska, to Atlin Lake, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e91-077 ◽

1991 ◽

Vol 28 (6) ◽

pp. 840-853 ◽

Cited By ~ 6

Author(s):

David A. Brew ◽

Susan M. Karl ◽

David F. Barnes ◽

Robert C. Jachens ◽

Arthur B. Ford ◽

...

Keyword(s):

Late Cretaceous ◽

High Rate ◽

Granitic Rocks ◽

Coast Mountains ◽

Glacier Bay ◽

Denali Fault ◽

Queen Charlotte Islands ◽

Sitka Sound ◽

Almost All ◽

Alexander Terrane

The 155 km wide, 310 km long Sitka Sound – Atlin Lake continent–ocean transect includes almost all the geologic, geophysical, and geotectonic elements of the Canadian Cordillera. It crosses the Chugach, Wrangellia, Alexander, Stikine, and Cache Creek terranes, the Gravina and Laberge overlap assemblages, intrusive and metamorphic belts, and neotectonic faults that bound major blocks. Linear belts of magnetic highs are associated with Jurassic and Cretaceous granitic belts in Wrangellia and the western and central parts of the Alexander terrane and with the granitic rocks of the Coast plutonic–metamorphic complex (CPMC). The Border Ranges fault may be expressed at depth on either side of the Peril Strait fault. An enigmatic northeast-trending gradient in the CPMC and adjacent rocks separates a regional magnetic low to the northwest from a 300 nT high field to the southeast. The Bouguer gravity field decreases in broad steps from Pacific crust high values to lows at the international boundary, with pronounced gradients at the east edge of Chugach terrane and west edge of of CPMC. It indicates that the crust thickens from about 20 to 40 km from southwest to northeast. Ultramafic bodies in the Chugach, Alexander, and Wrangellia terranes and Gravina assemblage underlie local highs. Most of the accumulated seismic strain is released by large earthquakes on the Fairweather – Queen Charlotte Islands plate-margin fault, but the northern part of the Glacier Bay region, the Denali fault zone, and the Coast Mountains also have significant seismicity. Part of the Glacier Bay region is being uplifted at a high rate. Most of these features are related to the joining of (i) Wrangellia to Alexander terrane (Carboniferous), (ii) Stikine to Cache Creek terrane (Early Jurassic), (iii) Alexander terrane and Gravina assemblage to Stikine (Late Cretaceous), and (iv) Chugach to Wrangellia and Alexander terrane (Late Cretaceous or Paleogene).

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