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Blufflands and Coulees

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About the Blufflands and Coulees

The Blufflands and Coulees, in some documents called the Paleozoic Plateau / Coulee Section, make up the largest portion of the Driftless Area, covering a small area in far northwest Illinois, a larger region in northeast Iowa and southeast Minnesota, and the largest portion in southwestern Wisconsin. This region conspicuously stands out from its surroundings, with rugged topography unlike the glaciated landscapes found nearby. The Mississippi river cuts through the entire length of this region.

This region consists mostly of a dissected plateau, with terrain varying from flat uplands, rolling hills and valleys, to steep slopes and bluffs. The bedrock consists mostly of a mix of dolomite, shale, sandstone, and limestone; the Baraboo Range also has quartize, and has a distinct topography as a result. There are also broad, flat bottomlands along the Mississippi River and its larger tributaries, including the Chippewa River, Black River, Root River, and Wisconsin River. Atop the bedrock, throughout the region, is a thin layer of loess, and in a few areas, thin layers of glacial drift. There is some karst, with sinkholes, caves, and springs formed from the soluble limestone and dolomite; the karst here makes the groundwater prone to contamination. However, the insoluble layers of rock also lead there to be numerous rocky-bottomed surface streams as well. Soils here tend to be nutrient-rich, but vary considerably in texture by site. Soils on ridgetops and atop bluffs are mostly formed on loess, but steep side-slopes have rockier soils formed on the exposed bedrock, and some of the bottomlands have sandy alluvial soils.

The climate is humid and continental, with four well-defined seasons and severe winters. Summers are hot, but temperatures drop quickly in fall and rise quickly in spring. Precipitation is seasonal, but only because of reduced precipitation totals in winter; the climate tends to be humid year-round. Precipitation tends to decrease to the north and west.

The original vegetation here is not well-known, but was potentially a mosaic of prairie and hardwood forests, and some oak savanna, with forests more common and more diverse towards the south. Prairie was mostly dominated by little bluestem (Schizachyrium scoparium) and indiangrass (Sorghastrum nutans). Forests were primarily of bur oak (Quercus macrocarpa) and white oak (Quercus alba), which opened into savanna on drier sites. More mesic areas had American basswood (Tilia americana) and sugar maple (Acer saccharum).

Currently this region has a mosaic of land use, reflecting the varied topography and soil textures. The dominant land uses are livestock production and dairy farming, both of which pose problems for water quality in the area. Agriculture is found both on the flatter uplands and broader bottomlands. Steep side-slopes are nearly entirely forested, and there are also many small, local uplands that are forested due to being hard-to-access. The lack of good riparian buffers compounds water quality problems here. Although most of the region is rural and sparsely populated, this region contains the cities of La Crosse, WI, Dubuque, IA, and Winona, MN, the two largest cities in the Driftless Area, all three located along the Mississippi river.

Within the Driftless area, this region is bordered irregularly to the west by, and surrounds in places, the Rochester/Paleozoic Plateau Upland. In the southeast, it partly surrounds the Savanna Section. In the southwest, it borders the Eastern Iowa and Minnesota Drift Plains to the southwest, and south of that, the Rolling Loess Prairies. As the Mississippi River leaves the Driftless area and its floodplain broadens, this area borders the Upper Mississippi Alluvial Plain. East of that, in Illinois, this region borders the Rock River Hills to the southeast. The borders in Wisconsin are diverse, but all involve opening up onto flatter, glaciated areas. In the south, this region borders the Southeastern Wisconsin Savannah and Till Plain to the east. North of that there is a small border to the north with the Central Sand Ridges, and then a long border to the northeast with the Glacial Lake Wisconsin Sand Plain. The northernmost part of this region is bordered to the northeast and north by the Central Wisconsin Undulating Till Plain, and to the west and northwest by the Lower St. Croix and Vermillion Valleys.