LOCATION LAROSE LA

Established Series
Rev. WLC-SDM-CLN
10/2018

LAROSE SERIES

The Larose series consists of very deep, very poorly drained, very slowly permeable soils that formed in fluid clayey sediments in fresh water coastal marshes. The sediments were deposited under water and have never air-dried and consolidated. Slope ranges from 0 to 0.2 percent. These soils are subject to flooding by runoff and tides.

TAXONOMIC CLASS: Very-fine, smectitic, nonacid, hyperthermic Typic Hydraquents

TYPICAL PEDON: Larose muck--freshwater marsh. (Colors are for wet soil.)

Oa--0 to 5 inches; very dark gray (10YR 3/1) muck; massive; 20 percent fiber, 5 percent rubbed; 70 percent mineral; massive, flows easily between fingers when squeezed leaving only roots and fiber in hand; many fine roots; moderately acid; clear smooth boundary. (0 to 15 inches thick)

A--5 to 15 inches; dark gray (5Y 4/1) clay; massive; very fluid, flows easily between fingers when squeezed leaving hand empty; many fine roots; few fine prominent yellowish brown (10YR 5/6) masses of iron accumulation with clear sharp boundaries in matrix; slightly acid; clear wavy boundary. (4 to 12 inches thick)

Cg1--15 to 36 inches; gray (5Y 5/1) clay; massive; very fluid, flows easily between fingers when squeezed leaving hand empty; few fine roots; few medium prominent strong brown (7.5YR 5/6) masses of iron accumulation along root channels; neutral; abrupt smooth boundary.

Cg2--36 to 47 inches; dark gray (N 4/0) clay; massive; very fluid, flows easily between fingers when squeezed leaving hand empty; 10 percent fine fiber evenly distributed throughout the matrix; common fine distinct olive (5Y 4/4) masses of iron accumulation with diffuse and clear boundaries; slightly alkaline; clear wavy boundary.

Cg3--47 to 60 inches; greenish gray (5GY 5/1) clay; massive; very fluid, flows easily between fingers when squeezed leaving hand empty; few fine faint olive (5Y 4/4) masses of iron accumulation with diffuse and clear boundaries; moderately alkaline; clear wavy boundary.

Cg4--60 to 80 inches; gray (5Y 5/1) clay; massive; very fluid, flows easily between fingers when squeezed leaving hand empty; moderately alkaline. (Combined thickness of the Cg horizons is 35 to more than 60 inches.)

TYPE LOCATION: Lafourche Parish, Louisiana; 2 miles west of Raceland; 0.75 miles north of old U.S. Highway 90 on west side of McMahon Canal.

RANGE IN CHARACTERISTICS: Larose soils are continuously saturated with fresh water. All of the mineral horizons above a depth of 60 inches have an n-value of 0.7 to 1 or more. The reaction ranges from strongly acid to slightly alkaline in the O and A horizons and slightly acid to moderately alkaline in the Cg horizons. Electrical conductivity (EC) is less than 2 dS/m throughout. Weighted average clay content of the particle-size control section is more than 60 percent.

The Oa horizon, where present, has hue of 7.5YR or 10YR, value of 2 or 4, and chroma of 1 or 2. Texture is muck or mucky peat.

The A horizon has hue of 10YR to 5Y, value of 2 to 4, and chroma of 2 or less. Texture is clay, silty clay, or mucky clay.

The Cg horizon has hue of 10YR to 5BG, or neutral, value of 3 to 5, and chroma of 2 or less. Texture is clay, silty clay, or mucky clay. Iron and iron-manganese accumulations range from none to few in shades of brown. Iron depletions, in various stages of reduction, range from none to few in shades of gray. Some pedons have thin organic layers within the C horizon. Also, some pedons have fine sand or loamy sand Cg horizons below a depth of 40 inches.

COMPETING SERIES: These are the Bancker, Barbary, Gentilly, and Scatlake series in the same family. Similar soils are the Allemands, Arat, Capers, Fausse, Harris, Ijam, Placedo, and Tatlum series. Bancker soils have 4 to 8 ds/m in upper 40 inches and are continuously saturated with brackish water. Barbary soils have logs and wood in the lower layers. Gentilly soils have lower horizons with n-value of less than 0.7. Scatlake soils have more than 20 percent extractable sodium in some part of the 10 to 40 inch particle-size control section. Allemands soils have an organic surface layer thicker than 16 inches. Arat and Tatlum soils have a fine-silty particle-size control section. Capers soils have 0.6 to 2.0 percent sulfides in the upper 20 inches of the solum. Fausse, Harris, Ijam, and Placedo soils have n-value less that 0.7 in all horizons.

GEOGRAPHIC SETTING: Larose soils are on the fringes of level fresh water marshes adjacent to distributary natural levees of rivers. Elevation is less than 3 feet. These soils are nearly continuously flooded. Slopes range from 0 to 0.2 percent. Near the type location the average annual rainfall is about 67 inches and the mean annual temperature is 70 to 72 F.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Allemands and Barbary series, and the Fausse, Kenner and Sharkey series. Fausse and Sharkey soils are at higher elevations and have n-value of less than 0.7 in all horizons. Kenner soils have organic layers more than 51 inches thick.

DRAINAGE AND PERMEABILITY: Very poorly drained. Runoff is negligible. Permeability is very slow. During tropical storms that produce high amounts of rainfall, floodwater covers the soil 4 feet or more with fresh water. Water level fluctuates between 1 feet above and 0.5 foot below the soil surface throughout the year. These soils have never air-dried and consolidated, therefore remain fluid.

USE AND VEGETATION: Used mainly for wildlife and recreation. Vegetation is fresh water plants including maidencane, bulltongue, alligatorweed, cattail, giant cutgrass, pickerelweed, swamp smartweed, and common rush.

DISTRIBUTION AND EXTENT: Gulf Coast Marshes (MLRA 151) along upper boundary of the freshwater marsh area of Louisiana, Texas and possibly in Mississippi. This series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: AUBURN, ALABAMA

SERIES ESTABLISHED: Lafourche Parish, Louisiana; 1981.

REMARKS: These soils have been mapped as miscellaneous land types of the freshwater marshes in previous surveys and as Allemands Variant in soil surveys of the New Orleans area.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon--0 to 15 inches (Oa and A horizons).

Ecological Site: Fresh Fluid Mineral Marsh.

ADDITIONAL DATA: Louisiana State University lab data (S94LA-109-021,025,032) from Terrebonne Parish.

TAXONOMIC VESION: Soil Taxonomy, Second Edition, 1999.

National Cooperative Soil Survey
U.S.A.