Buffalo Ridge - Geology

Geology

Buffalo Ridge is commonly considered the elevated land extending through Lincoln, Lyon, Pipestone, Murray, Rock, and Nobles counties. It is a drainage divide separating the watersheds of the Mississippi and Missouri Rivers.

Buffalo Ridge is part of the inner coteau and is the highest point of the Coteau des Prairies in Minnesota. Its bedrock is formed of Cretaceous shale, sandstone and clay that lie above the pinkish-red Upper Precambrian Sioux Quartzite. These units are covered in most areas by thick deposits of glacial drift, which consist of up to 800 feet (244 m) of pre-Wisconsin age glacial till (generally considered Kansas drift) left after the glaciers receded. The inner coteau is made up of extremely stream-eroded glacial deposits of pre-Wisconsin glacial drift, which is then covered by a 6 to 15 foot (1.8 to 4.6 m) thick deposit of a wind-blown silt called loess. This covering results in the creation of an area with long, gently sloping hills. Loess is an easily eroded material, and because of this there are few lakes and wetlands in the inner coteau area. Loess however promotes well established dendritic drainage networks, the majority of which flow into the Missouri River and Minnesota River systems. Loamy, well-drained soils like Mollisols-Aquolls and Udolls containing Borolls and Ustolls dominate the soils of the inner coteau. On the areas of eroded glacial deposits, dry prairie and moist prairie soils like Cummins and Grigal are present. These soil types, along with the temperate climate, combine to make perfect growing conditions for tallgrass prairie, which once covered almost the entire inner coteau.