Abstract: Change of Structural Style and Hydrocarbon Systems Along the Strike of the Canadian and U.S. Cordilleran Thrust Belt

KLUTH, CHARLES F

The style and geometry of thrust related structures varies along the strike of the Canadian and U.S. parts of the Cordillera in western North America. The variation in style may be due to a number of factors, but is directly correlatable with changes in the stratigraphic section being deformed.

In northern British Columbia, Canada, the thick Mesozoic shale section was involved in the thrusting. The structural style in that region includes detachment folds and blind thrusts. The source rocks in the lower Triassic shales within the deformed package charge complex traps in the Triassic carbonates.

In southern Alberta, and in northern Montana, shortening increases and the Paleozoic carbonates are involved as large thrust sheets. The Mesozoic clastics are highly imbricated in the foothills belt to the foreland of the carbonate sheets. Traps include hanging wall folds in the Cretaceous sandstones and horses in duplexes where the carbonates are involved. They also include structures associated with a well developed triangle zone at the front edge of the belt. The source rocks in the Paleozoic and Mesozoic charge the relatively simple structures, and faults contribute to the traps.

In Wyoming, the Paleozoic and Mesozoic sections includes thick strong rocks. The thrust belt is formed by four major thrust sheets. The traps include relatively simple hanging wall folds charged by a relatively thin Cretaceous foreland basin section directly in the footwall. Faults limit the hydrocarbon columns, and there is no well developed triangle zone at the foreland edge of the belt.

In Utah, the belt is still made up of relatively few large sheets. The thrust structures are relatively simple hanging wall folds, although the presence of Jurassic evaporites causes local complexities. The foreland section is thin, and generally lacks adequate source rocks.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria