Global Controls, Coupled Kinematic and Thermal Modeling of the Lewis Transect, Southwest Alberta, Canada

Nicolaas J. Hardebol¹, Jean-Luc Faure¹, Jean-Paul Callot¹, Giovanni Bertotti², and Francois Roure^1
1 Institut Français du Pétrole, Rueil Malmaison, France
² Vrije Universiteit, Amsterdam, Netherlands

Subduction related processes such as corner flow and arc magmatism deeply affected the upper plate thermal regime and subsequent mountain building processes in the North American Cordillera. The present study aims at understanding the kinematic and thermal evolution of a regional transect, located in the SE Canadian Cordillera (Lewis transect). From west to east, the Lewis transect encompasses the Purcell anticlinorium, the Main and Front ranges, the Foothills and the foreland autochthon. Kinematic modelling includes (1) the pre-orogenic platform development, (2) the Cordillera and foreland basin development (middle Cretaceous to early Tertiary), and (3) the post orogenic extension since late Eocene, combined with a general uplift. The workflow is twofold: (1) a proper description of upper to middle crustal strain history and (2) a thermal-kinematic model from the Main Ranges to the foreland, constrained by the amount and timing of burial and exhumation. Although most effort is dedicated to the peak period of Foreland belt development, we also looked carefully at the long-lasting post-Laramian evolution, when the American plate still interacted with the subduction of the Pacific lithosphere. For instance, the Tertiary collapse is expressed by the formation of two graben systems (i.e., the Rocky Mountain Trench & Flathead Valley Graben) together with significant uplift of a few kilometres, decreasing progressively from the foothills toward the foreland. Forward modelling includes tests of reasonable kinematic scenarios of thrusting, published data on organic matter maturation constraining the thermal and burial history together with U-TH/He, as well as apatite fission track data delivering exhumation controls. The study enhanced insights in heat transfer facilitating the prediction of generation and migration of hydrocarbons. Finally, the Lewis transect is compared to another study already performed along the Banff-Calgary transect, allowing discussion on along strike 3D variability.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005