Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION II.2.3. Ivanhoe-Worthington Coteau
DISCUSSION: This sub-subsection includes Altamont ground moraines and stagnation moraines and Bemis ground moraines. At the outer edge, where Sub-subsection II.2.3 meets Subsection II.1, the Altamont ground moraine forms a straight, steep escarpment with the Minnesota lowlands to the northeast. It drops 300 to 400 feet, from approximately 1,600 feet in the southwest to 1,200 feet in the northeast. Although the elevations are not as high as those of the Lake Benton-Adrian Coteau immediately to the south, most of the divide between the Missouri and Mississippi drainage is located within this sub-subsection (University of Minnesota et al. 1981a).
ELEVATION: 1,140 to 1,800 feet (347 to 549 m).
AREA: 2,555 square miles (6,617 sq km).
STATES: Minnesota.
CLIMATE: See subsection.
BEDROCK GEOLOGY: The bedrock is covered with 100 to 800 feet of glacial drift (Olsen and Mossler 1982). This drift is shallowest near the base of the escarpment that defines the northern boundary of the sub-subsection.
Immediately beneath the glacial drift, most of the sub-subsection has Cretaceous shale, sandstone, and clay. However, there are also extensive areas of upper Precambrian Sioux quartzite (Morey 1976). There are no rock outcrops within the sub-subsection.
LANDFORMS: Ground moraine and stagnation moraines. The Bemis ground moraines, located along the southern edge, are flat and contain large areas of poorly drained soils. In the southeast, these poorly drained soils cover broad expanses of flat land; in the southwest, the poorly drained lands occupy drainageways in the depressions between numerous low ridges.
LAKES AND STREAMS: Several large lakes formed along the boundary between the Bemis end moraine (in Sub-subsection II.2.2) and the Bemis ground moraine; these include Lake Ocheda, Okabena Lake, Lake Menton, Lake Shaokotan, and Lake Mindeshike.
The Altamont ground moraine, which forms the outer margin of the sub-subsection, is deeply eroded by many narrow, straight stream channels. As a result of the dissected topography, most of the soils are well drained.
The Altamont ice-stagnation moraines contain most of the lakes larger than 160 acres in the sub-subsection and many small lakes. Many streams originate in the stagnation moraine and flow into either the Missouri or the Mississippi drainage systems.
SOILS: Most of the sub-subsection is mapped as well-drained loamy soils. Most of the remaining soils are mapped as poorly drained loamy soils; these are concentrated on the Altamont ice-stagnation moraine and the Bemis ground moraine in the northwest and the Bemis ground moraine in the southeast (University of Minnesota et al. 1981a, Cummins and Grigal 1981).
PRESETTLEMENT VEGETATION: The entire sub-subsection was dominated by tallgrass prairie or wet prairie. Hill prairie, containing species more characteristic of the western midgrass prairies, also occurred. The steep scarp on the northern edge of the coteau supported oak, elm, ash, and basswood in its gullies, which are protected from the winds and fires of the Coteau and which also receive meltwaters from winter snow accumulations (Wright 1972).
NATURAL DISTURBANCE: Fire and drought maintained the prairie.
PRESENT VEGETATION AND LAND USE: Almost the entire sub-subsection is farmed.
RARE PLANTS: Botrychium campestre (prairie moonwort), Cypripedium candidum (a small white lady's-slipper), Desmodium illinoensis (Illinois tick-trefoil), Eleocharis parvula (a species of spike-rush), Lespedeza leptostachya (prairie bush clover), Opuntia macrorhiza (plains prickley pear), Rhynchospora capillacea (hair-like beak-rush), Sanicula canadensis (Canadian black snakeroot), Schedonnardus paniculatus (tumblegrass), Scleria verticillata (whorled nut-rush), Triglochin palustris (marsh arrow-grass), Trillium nivale (snow trillium).
RARE ANIMALS: Birds: Calcarius mccownii (McCown's longspur (extirpated)), Numenius americanus (long-billed curlew (extirpated)).
NATURAL AREAS: See subsection.
PUBLIC LAND MANAGERS: See subsection.
CONSERVATION CONCERNS: Des Moines River Prairies have been identified as a critical landscape for biodiversity protection.
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