LAUSR

We establish a comprehensive three-dimensional geometric and kinematic description of the Front Ranges in the Bow Valley−Kananaskis region of the Southern Canadian Rocky Mountains to rigorously evaluate and expand upon fundamental paradigms that define our understanding of thin-skinned fold-and-thrust belts. We employ a modern strike and dip data collection method based on high-resolution imagery and digital elevation models, verified by direct field observations, to analyze the structures and construct balanced and retrodeformable cross sections. This approach yields >10,000 new attitude measurements of bedding and faults that represent a more than tenfold increase in previously published maps of the region. These observations and our analysis support many of the fundamental conclusions of previous work, namely the imbricate structural style and general break-forward progression of thrusting. However, our analysis suggests a pervasive, multi-modal distribution of bed dips separated by axial surfaces or hinge zones in the backlimbs of thrust sheets as opposed to the previous hypothesis of listric backlimb geometries. Our data also show bedding and fault dips that are generally parallel. These observations, coupled with the geologic map patterns, motivate refinements to the interpretation of structural styles, geometry, and faulting sequence of the region, including the presence of multiple regional basal detachments over an ∼950 m zone. Through sequentially restoring our sections, we calculate a total shortening of 67 (±17%) km and derive a kinematic history of the Front Ranges that involves a complex, episodic sequence of thrusting. Overall, these insights, coupled with applying our semi-automated geologic data collection methods have applications for investigating exposed fold-and-thrust belts worldwide.