Southern River Breaks 42i. Glaciated Dark Brown Prairie T he Northwestern Glaciated Plains ecoregion marks the westernmost extent of continental glaciation. The youthful morainal landscape has significant surface irregularity and high concentrations of wetlands. The rise in elevation along the eastern boundary defines the beginning of the Great Plains. Pronghorn antelope coexist with cattle on rangeland in the western Dakotas.
Cattle graze on the steeper land that occurs along drainages.
Level to gently rolling plain sloping to Missouri River. Geology Surficial Material and Bedrock Wisconsinan glacial till over Tertiary sandstone and shale in Cretaceous Pierre Shale. Potential Natural Vegetation Western wheatgrass, needleandthread, prairie junegrass, green needlegrass. Land Use and Land Cover Mainly tilled agriculture of spring wheat, barley, alfalfa, silage corn. Some grazing on steep and saline or wet areas.