Effects of Lateral Lithologic Changes on the Development of Structures and Fractures in the Grande Cache Area, West-Central Alberta

Foothills structures within Mesozoic strata of the Grande Cache area in west-central Alberta illustrate the following four relationships between lateral lithology changes in fluvial systems and the development of folds and fractures.;(1) Channels with a strong mechanical interface or a change in sandstone package thickness act as barriers during deformation that alter the position, orientation, and geometry of folding.;(2) Changes in stratigraphy and fold geometry modify the local stress field, affecting local fracture orientations and densities.;(3) Fracture relationships include: the highest density and more through-going fractures develop on fold crests; stress concentrates at channels; fracture density deceases with increasing grain size and/or decreasing fracture length; and fractures occur as discrete planes with numerous fracturing episodes and fills.;(4) The relationships observed can be applied to other fluvial systems throughout the Rockies.;These four conclusions can be summarized as: stratigraphic architecture controls deformation at different scales.