region M Area 113 larger picture

Central Claypan Areas

Till Plains Section of the Central Lowland Province of the Interior Plains of Illinois area.
The part in Missouri is in the Dissected Till Plains Section of the same province and division.

69% of this are within Illinois.
31% of this area within Missouri.

Total Land Area 12,790 square miles (33,150 square kilometers).

Towns/cities include:
Carbondale, Centralia, Effingham, Herrin, Marion and Mount Vernon, Illinois.
Mexico and Moberly, Missouri

Parts of the Shawnee National Forest, Crab Orchard National Wildlife Refuge are within this MLRA.


Pennsylvanian limestone and shale bedrock underlies the glacial till in both Missouri and Illinois.

It is an area of gently sloping to rolling, dissected plains. The northern part of the area has a thin mantle of loess.

Loess overlies old (pre-Wisconsin) glacial drift that has a high content of clay in this MLRA. This area consists of nearly level to gently sloping, old till plains. Stream valleys are shallow and generally are narrow.

Topography -

Elevation is 660 to 980 feet (200 to 300 meters) in Missouri and about 660 feet (200 meters) in Illinois, increasing gradually from south to north in both States. Local relief is generally 5 to 10 feet (1.5 to 3 meters).


The average annual precipitation in this area is 36 to 46 inches (915 to 1,170 millimeters).
Most of the rainfall occurs as convective thunderstorms during the growing season.
The average annual temperature is 51 to 57 degrees F (11 to 14 degrees C).
The freeze-free period averages about 205 days and ranges from 190 to 225 days.

Major Hydrologic Unit Areas

Name Code Extent*
Wabash (0512) 36%
Upper Mississippi-Kaskaskia-Meramec (0714) 28%
Upper Mississippi-Salt (0711) 26%
Lower Ohio (0514) 6%
Lower Missouri (1030) 4%

* this is the percent of area drained by each named hydrologic unit

The Kaskaskia, Little Muddy, Little Wabash, Embarras, and Saline Rivers are in the part of this area in Illinois.

Mark Twain Lake, a major reservoir on the Salt River, and the North and West Forks of the Cuivre River are in the part of the area in Missouri.


Estimated withdrawls in this MLRA:
Public supply surface water 26.5% ground water 4.1%
Livestock surface water 0.2% ground water 0.2%
Irrigation surface water 0% ground water 2.1%
Other surface water 62.5% ground water 4.3%

Total daily withdrawls average 450 million gallons per day (1.705 million liters).
11% Ground water sources
89% Surface water sources

Reservoirs have been built on the larger rivers in this area to provide drinking water and water for industries and is generally of good quality.

Small to moderate quantities of ground water are available in this area. The supply of ground water from glacial drift in Missouri is small, undependable, and of poor quality (because of high concentrations of naturally occurring salts). Wells in the Pennsylvanian-Mississippian sediments in the part of this area in Illinois produce low yields. Little is known about the quality of the water in this aquifer.


  • Mesic soil temperature regime.
  • Aquic or udic soil moisture regime.
  • Mixed or smectitic mineralogy
  • The soils are very deep, loamy or clayey, and can range from well drained to poorly drained.

    Dominant Soils:

  • Alfisols
  • Great Group Series Location
    Hapludalfs Armstrong, Hoyleton, and Keswick seriesformed in loess and/or pedisediment over till on uplands
    Hapludalfs Hickory seriesformed in till on till plains
    Fragiudalfs Ava seriesformed in loess and/or pedisediment over till on uplands
    Epiaqualfs Bluford and Mexico series formed in loess over pedisediment
    Epiaqualfs Leonard seriesformed in loess over till on uplands.
    Albaqualfs Putnam seriesformed in loess
    Albaqualfs Cisne seriesloess over pedisediment
    Albaqualfs Wynoose seriesloess and/or pedisediment over till on uplands.

    Fauna and Flora

    When this area was settled, most of the level soils on uplands supported tall prairie grasses, mainly big bluestem, Indiangrass, prairie dropseed, and switchgrass. The present potential for natural vegetation on these soils is unknown.

    Forests of post oak, swamp white oak, blackjack oak, and pin oak grow on poorly drained soils. White oak, shingle oak, black oak, hickory, white ash, basswood, sugar maple, elm, and walnut grow on the better drained soils. Silver maple, willows, cottonwood, sycamore, elm, pin oak, white oak, hickory, and ash grow on flood plains.

    Some of the major wildlife species include whitetailed deer, coyote, turkey, and bobwhite quail.

    Land Use

    67% - Cropland - private
    10% - Grassland - private
    1% - - Federal
    13% - Forest - private
    5% - Urban development - private
    2% - Water - private
    2% - Other - private

    Corn, soybeans, other feed grains, and hay are the principal crops. Some cotton is grown in Oklahoma. More than 2/5ths of the area supports pasture grasses and legumes. The grassland in the area supports introduced and native grasses. The forested areas are mainly on the steeper slopes and on wet bottom land.

    The major resource concerns include wetness, water erosion, flooding, limited available water capacity and maintenance of the content of organic matter in the soils and productivity of the soils, particulary those with high sodium content.

    Conservation practices on cropland generally include surface and subsurface drainage systems, crop residue management, filter strips, cover crops, and nutrient and pest management.

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