Abstract

This study describes an area in the inner Foothills along the Smoky River near Grande Cache, Alberta. Lower Cretaceous clastic rocks are exposed in the Mason and Muskeg Thrust sheets. The sedimentology of these rocks is characterized by shallow marine, coastal plain, alluvial flood plain and alluvial channel environments.

A computer package for storing, retrieving and displaying geological data from outcrops and drill-holes forms the data base for this study. The data can be displayed on maps of any scale. Cylindrical domains are established and geological cross-sections obtained by down-plunge projection.

Folds of the area are chevron folds caused by layer-parallel shortening. Chevron folds are expected in the multilayered sequence of alternating competent and incompetent strata. Disharmonious folding of shale and coal horizons between sandstones results in tectonic thickening of coal in the fold hinges. These areas form major exploration targets for open pit coal mines. The folds are cylindrical, except at their tapering ends, where they are conical. Most faults are southwest-dipping thrust faults. They display flats and ramps that cut up stratigraphic section. The total shortening accomplished by folding and thrusting is 33 percent.