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Organic maturation of strata in the Western Canada Sedimentary Basin has been investigated in numerous studies using petrological, chemical and physical methods. Compilation of existing data has facilitated a regional analysis of the maturation patterns and maturation history. Variation in maturation patterns occurs on three levels: basin wide (1st order), regional (2nd order) and local (3rd order). First order variations are manifest by an overall increase in maturity of strata of the same age from east to west, from the Plains to the Rocky Mountain Foothills and Front Ranges, in response to progressively deeper burial and higher paleo-geothermal gradients. Superimposed on this first order (basinal scale) variation in maturity are second and third order variations, which are interpreted as reflecting local differences in depth of burial, conductive and advective heat transport or affects of thrust faulting. The main component of maturation for most Phanerozoic strata occurred during deep burial by Late Cretaceous and/or Paleogene molasse in foredeeps developed in response to crustal loading associated with the easterly migration of the foreland fold and thrust belt. As a result of the west-to-east propagation of deformation during the Laramide Orogeny, deep burial, maturation, hydrocarbon generation and uplift occurred earlier in the foreland belt (Late Cretaceous) than in the Plains to the east, where the main component of maturation and hydrocarbon generation occurred as late as Eocene. A thick succession of strata currently are within the oil window in the Plains because of the low maturation gradients. In the deformed belt however, because of the higher maturation gradients, the thickness of strata within the oil window is corresponding less. In response to higher paleo-geothermal gradients, strata in the deformed belt matured more quickly, leading to more rapid hydrocarbon generation and migration than in areas to the east.
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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
1 University of British Columbia, Vancouver, British Columbia V6T 2B4
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