United States Department of Agriculture
Natural Resources Conservation Service		 Southeast Coastal Plain and Caribbean Soil Survey Region #15 Go to Accessibility Information
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Alligator Series

  • Depth class: Very deep
  • Drainage class: Poorly drained
  • Permeability: Very slow
  • Parent material: Clayey alluvium
  • Landscape: Southern Mississippi River Valley
  • Landform: Flood plains
  • Landform position: Backswamps, brakes, sloughs, depressions, and lower positions on natural levees
  • Slope: 0 to 3 percent
  • Taxonomic class: Very fine, smectitic, thermic Chromic Dystraquerts

Commonly Associated Soils

The Alligator series in Leflore County is commonly associated on the landscape with Dowling and Tensas soils.

  • The very poorly drained Dowling soils are in depressions.
  • The somewhat poorly drained Tensas soils are in slightly higher positions than the Alligator soils.

Typical Pedon

Alligator clay, 0 to 1 percent slopes; about 7 miles west of Itta Bena; 1 mile north of U.S. Highway 82; SW1/4NE1/4 sec. 30, T. 19 N., R. 2 W.

  • Ap—0 to 4 inches; dark grayish brown (10YR 4/2) clay; weak and moderate medium granular structure; firm, sticky and plastic; common fine and medium roots; strongly acid; abrupt wavy boundary.
  • Apd—4 to 7 inches; dark grayish brown (10YR 4/2) clay; massive in place, parts to moderate medium angular blocky structure; very firm, very sticky and very plastic; common medium distinct yellowish brown (10YR 5/6) iron accumulations; common fine roots in concentrated masses in cracks; 1/4- to 1/2-inch-wide pockets and old cracks filled with soil material from the Ap horizon; yellowish brown stains along cracks; slightly acid; abrupt wavy boundary.
  • Bg—7 to 19 inches; light brownish gray (10YR 6/2) clay; moderate fine and medium angular blocky structure; very firm, very sticky and very plastic; many medium and coarse distinct yellowish brown (10YR 5/6) iron accumulations; common fine roots; few fine black concretions; very strongly acid; gradual wavy boundary.
  • Bssg1—19 to 29 inches; light brownish gray (10YR 6/2) clay; wedge-shaped aggregates that part to weak and moderate medium angular blocky structure; very firm, very sticky and very plastic; common medium distinct yellowish brown (10YR 5/6) iron accumulations; few fine roots; cracks intersecting slickensides; very strongly acid; gradual wavy boundary.
  • Bssg2—29 to 52 inches; grayish brown (2.5Y 5/2) clay; wedge-shaped aggregates that part to moderate fine and medium angular blocky structure; very firm, very sticky and very plastic; few fine roots; common coarse intersecting slickensides; common fine faint light brownish gray (2.5Y 6/2) iron depletions and common medium distinct dark yellowish brown (10YR 4/4) iron accumulations; strongly acid; gradual wavy boundary.
  • Bssyg1—52 to 65 inches; grayish brown (2.5Y 5/2) clay; wedge-shaped aggregates that part to moderate fine and medium angular blocky structure; very firm, very sticky and very plastic; few fine prominent strong brown (7.5YR 4/6) and many medium distinct dark yellowish brown (10YR 4/4) iron accumulations; many fine roots; common intersecting slickensides; common fine and medium gypsum crystals in seams; slightly alkaline; gradual wavy boundary.
  • Bssyg2—65 to 76 inches; grayish brown (2.5Y 5/2) clay; weak coarse prismatic structure parting to weak medium subangular blocky; firm, very sticky and very plastic; few medium slickensides; common fine gypsum crystals; many medium distinct yellowish brown (10YR 5/4) and few strong brown (7.5YR 5/6) iron accumulations; slightly alkaline; gradual wavy boundary.
  • Cg—76 to 84 inches; grayish brown (2.5Y 5/2) clay loam; massive; common medium distinct yellowish brown (10YR 5/6) and common medium prominent yellowish red (5YR 4/6) iron accumulations; slightly alkaline.

Range in Characteristics

  • Thickness of the solum: More than 60 inches
  • Reaction: Very strongly acid or strongly acid in the A horizon and the upper part of the B horizon, except where lime has been applied; very strongly acid to moderately alkaline in the lower part of the Bss horizon and in the BC horizon, where present; neutral to moderately alkaline in the C horizon
  • Control section: Averages 60 to 85 percent clay
  • Other distinctive features: When dry, the soils have deep, wide cracks that are 2 to more than 3 feet in depth and that form a roughly polygonal pattern on the surface. The polyhedrons formed by the cracks range from 1 foot to more than 2 feet across. Intersecting slickensides are within a depth of 40 inches.
  • A horizon:
    • Color—hue of 10YR to 5Y, value of 4 or 5, and chroma of 2 or 3
    • Texture—clay
  • Bg horizon:
    • Color—hue of 10YR to 5Y, value of 4 to 7, and chroma of 1 or 2
    • Texture—clay
    • Redoximorphic features—few to many iron accumulations in shades of brown or yellow
    • Other distinctive features—few pressure faces and slickensides in some pedons
  • Bssg and Bssyg horizons and, where present, BCss horizon:
    • Color—hue of 10YR to 5Y, value of 4 to 7, and chroma of 2 or less
    • Texture—silty clay or clay
    • Redoximorphic features—few to many iron depletions and accumulations in shades of gray, brown, and yellow
    • Other distinctive features—few to many pressure faces and slickensides; and, in some pedons, few or common pockets and veins of gypsum crystals and few or common concentrations of calcium carbonate
  • Cg horizon:
    • Color—hue of 10YR to 5Y, value of 4 to 7, and chroma of 1 or 2
    • Texture—silty clay loam, clay loam, or loam
    • Redoximorphic features—few to many iron depletions and accumulations in shades of gray, brown, yellow, and red


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