Beginning of foreland subsidence in the Columbian-Sevier belts, southern Canada and Northwest Montana

Subsidence analysis and geometry of Jurassic-Cretaceous foreland strata in northwestern Montana and southern Alberta and British Columbia suggest that loading by the fold-thrust belt in Canada began as much as 40 m.y. earlier than in Montana. In Canada, early foreland basin deposits are Late Jurassi...

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Bibliographic Details
Published in:Geology (Boulder) 1995-08, Vol.23 (8), p.723-726
Main Authors: Gillespie, Janice M, Heller, Paul L
Format: Article
Language:English
Subjects:
Alberta
basins
British Columbia
Canada
Cascade County Montana
Columbian Orogeny
Cretaceous
erosional unconformities
faults
fold and thrust belts
foreland basins
forelands
Geology
geometry
Glacier County Montana
Jurassic
Mesozoic
Montana
North America
northwestern Montana
orogenic belts
Plate tectonics
Rocky Mountains
Rocky Mountains foreland
sed rocks, sediments
sedimentary basins
Sedimentary petrology
sedimentation
Sevier orogenic belt
southern Alberta
southern British Columbia
structural controls
Structural geology
subsidence
tectonics
Teton County Montana
thrust faults
unconformities
United States
Western Canada
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Summary:Subsidence analysis and geometry of Jurassic-Cretaceous foreland strata in northwestern Montana and southern Alberta and British Columbia suggest that loading by the fold-thrust belt in Canada began as much as 40 m.y. earlier than in Montana. In Canada, early foreland basin deposits are Late Jurassic age, thicken rapidly westward, and are restricted to a narrow belt within 30 km of the thrust belt. In western Montana, contemporaneous deposits are widespread and do not increase markedly in thickness toward the thrust belt. The unconformity overlying these deposits also changes from Canada, where it is angular, to a disconformity in western Montana near Great Falls. Between these two areas, foreland geometry is transitional over a distance of
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1995)023<0723:BOFSIT>2.3.CO;2