Detachment folding in lower Cretaceous coal-bearing strata of the Luscar Group as exposed by mining in the AN pit of the Cardinal River Coal Mine near Hinton, Alberta, Canada. The dragline at the bottom of the pit provides a scale. The Jewel Coal Seam, which has a stratigraphic thickness of 10 m, is structurally thickened in the cores of chevron-type folds, providing enhanced mining situations. There are various detachment horizons. The one visible in the picture is at the contact of the Jewel Coal Seam (black in the centre of the picture) and the underlying sandstone of the Torrens Member. On a larger scale there is detachment along the underlying Folding Mountain/Mystery Lake Thrust, which in places follows shale horizons in the Nikanassin and Fernie formations. These folds form part of the Cadomin Syncline, which is a footwall syncline of the Nikanassin/Drinnan Thrust.
Lebel, D., Langenberg, C.W. and Mountjoy, E.W. (1996). Bulletin of Canadian Petroleum Geology 44, 282-298
This is a Journal of Structural Geology Photograph of the Month (JSG 30, 547). Photo ID 201