LOCATION MERMENTAU LA
Established Series
Rev. CM-WLC-CLN
10/2018
MERMENTAU SERIES
The Mermentau series consists of very deep, poorly drained, very slowly permeable soils that formed in clayey over loamy coastal sediments. These soils are on low ridges on broad coastal brackish marshes. Slope is less than 1 percent.
TAXONOMIC CLASS: Clayey over loamy, smectitic over mixed, superactive, nonacid, hyperthermic Typic Endoaquepts
TYPICAL PEDON: Mermentau clay--on level brackish marsh. (Colors are for moist soil)
A--0 to 6 inches; black (10YR 2/1) clay; moderate medium angular blocky structure; firm; many fine and medium roots; slightly alkaline; gradual wavy boundary. (4 to 12 inches thick)
Bg--6 to 19 inches; gray (5Y 5/1) clay; weak coarse prismatic structure parting to moderate medium angular blocky; firm; common fine roots; few fine pores; few fine faint dark yellowish brown (10YR 4/4) iron concentrations; dark gray (10YR 4/1) shiny ped surfaces; moderately alkaline; abrupt wavy boundary. (5 to 18 inches thick)
2Cg1--19 to 42 inches; grayish brown (10YR 5/2) very fine sandy loam; weak coarse subangular blocky structure; friable; few fine roots; many medium distinct yellowish brown (10YR 5/6) iron accumulations; few black accumulations; common crawfish channels; horizontal band of gray (10YR 5/1) silty clay loam 2 inches thick at a depth of 31 to 33 inches; moderately alkaline; gradual wavy boundary. (11 to 37 inches thick)
2Cg2--42 to 48 inches; gray (10YR 5/1) very fine sandy loam; massive; friable; few fine roots; common medium distinct dark yellowish brown (10YR 4/6) iron concentrations; many fine shell fragments; few black iron-manganese accumulations; common crawfish channels; moderately alkaline; gradual wavy boundary.
2Cg3--48 to 59 inches; gray (N 5/) very fine sandy loam; massive; friable; few fine faint yellowish brown iron concentrations; few fine shell fragments; common crawfish channels; moderately alkaline; clear smooth boundary. (0 to 22 inches thick)
3Cg4--59 to 69 inches; greenish gray (5GY 5/1) sandy clay; massive; very fluid, flows easily between fingers when squeezed leaving small residue; few fine roots; few fine faint yellowish brown (10YR 5/4) iron concentrations; few black iron-manganese accumulations; moderately alkaline.
TYPE LOCATION: Cameron Parish, Louisiana, 0.5 mile north of Grand Chenier; 250 feet northeast of Mermentau River; 75 feet northwest of REA pole number 25; SW1/4 SW1/4 sec. 2, T. 15 S., R. 6 W.
RANGE IN CHARACTERISTICS: Thickness of solum ranges from 10 to 30 inches. Reaction ranges from neutral to moderately alkaline throughout. The electrical conductivity of the saturation extract (dS/m) ranges from 7 to 23.
The A horizon has hue of 10YR to 5Y, value of 2 to 4, and chroma of 1 or 2. A horizons with a color value of 2 or 3 are 4 to 7 inches thick. Texture is silty clay or clay.
The Bwg horizon has hue of 10YR to 5Y, value of 4 or 5, and chroma of 1 or it is neutral. Texture is silty clay or clay.
Dominant subhorizons of the 2Cg horizon have hue of 10YR to 5Y, value of 4 to 6, and chroma of 1 or 2, or they are N/4 - N/6. The 2Cg horizon is very fine sandy loam, fine sandy loam, or loam. Sand size shell fragments range from none to common.
The 3Cg horizon, where present, has hue of 10YR to 5GY, value of 5 or 6, and chroma of 1 or it is neutral. It is sandy clay, silty clay, or clay. N-values range from 0.7 to more than 1. Sand size shell fragments range from none to few.
COMPETING SERIES: There are no other series in this family.
Alligator,
Perry,
Sharkey,
Solier and
Tunica are in similar families. Alligator, Perry, and Sharkey soils have more than 60 percent clay in the 10-to 40-inch control section and develop cracks to a depth of 20 inches or more in most years. Solier soils have Bw2 horizons with dominant hue of 5YR and clayey over fine-silty particle-size control sections.
GEOGRAPHIC SETTING: Mermentau soils are on low ridges in the Gulf coast marshes at elevations of 2 to 4 feet above sea level. They are flooded with brackish water during storms and high tides. They are also flooded with fresh water during heavy rains. They formed in clayey over loamy sediments. Slopes range less than 1 percent. The mean air temperature is 68 degrees F, and the mean annual rainfall is about 53 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Creole,
Hackberry,
Peveto, and
Scatlake series. Creole soils are on lower positions and have a fine particle-size control section. Hackberry soils are on higher positions and have a sandy particle-size control section. Peveto soils are on higher ridges and are sandy throughout. Scatlake soils have more than 60 percent clay in the 10-to 40-inch control section and have an n-value of more than 1 in all horizons.
DRAINAGE AND PERMEABILITY: Mermentau soils are poorly drained; runoff is negligible; permeability is very slow. The water level fluctuates between a depth of 0 to 3.5 feet below the surface throughout the year.
USE AND VEGETATION: Used mainly for rangeland and wildlife habitat. The vegetation consists dominantly of gulf cordgrass, marshhay cordgrass, seashore saltgrass, and seashore paspalum.
DISTRIBUTION AND EXTENT: Along the Gulf coast brackish marshes of Louisiana and Texas (MLRA 151). The soils of this series are not extensive.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: AUBURN, ALABAMA
SERIES ESTABLISHED: Cameron Parish, Louisiana; 1983.
REMARKS: Mermentau soils were formerly included with the Harris series. The 2 chroma colors in the 2Cg horizon are interpreted to be inherited from a drier moisture regime prior to subsidence. The exchangeable sodium exceeds 15 percent in the A and Bg horizons. The exchangeable sodium decreases with depth to 48 inches, then increases. This pedon fails the criteria for Halaquepts because of the increase. In this pedon the exchangeable sodium ranges from 10 to 33 percent and the exchangeable magnesium ranges from 27 to 50 percent. Some data indicate that these soils may marginally classify in a Fluvaquentic subgroup.
Diagnostic Horizons and Features:
Ochric Epipedon - 0 to 6 inches
Cambic horizon - 6 to 19 inches
ADDITIONAL DATA: LSU data from Cameron Parish, LA (S81LA-23-1).
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.
National Cooperative Soil Survey
U.S.A.