The Drumheller Badlands are built by the deposition and erosion of paleo sediments. Stratigraphic layers include a bentonite clay layer and black coal layers, seen in A-1', A-3' and A-4'. Bentonite clay is an aluminum phyllosilicate deposited by volcanic ash containing montmorillonite. The black coal layers are composed of bituminous coal and lithified peat. The coulees are split by meandering streams that form point bars, cut banks and oxbow lakes as seen in A-2'. Plants that thrive in dry climates and erratic's are present in the base of the coulees as seen in A-3'. Varying sedimentation and erosion rates lead to the formation of window and hoodoo like structures prone to frost wedging and organic weathering from plants taking root in the sediments like shown in A-1'. The badlands are composed of rocks from the Cretaceous period and several dinosaur fossils have been discovered in these areas.