LOCATION MARSHNECK               RI+CT

Established Series
Rev. MKP-JDT-DCP
07/2018

MARSHNECK SERIES


The Marshneck series consists of very deep, subaqueous soils permanently submerged beneath up to 250 cm of tidal estuarine water on flood tidal delta slopes and shoals in coastal lagoons and bays. Marshneck soils are formed in coarse loamy marine and estuarine sediments transported by flood tidal currents and estuarine silts settling in low energy areas. Slope ranges from 2 through 5 percent, mean annual air temperature is about 10 degrees C, and mean annual precipitation is about 1295 mm.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, nonacid, mesic Haplic Sulfiwassents

TYPICAL PEDON: Marshneck very fine sandy loam on a north facing, 2 percent slope on a flood tidal delta slope under 2.0 meters of tidal estuarine water. Tidal range is 100 cm. (Colors are for moist soil).

Ase--0 to 19 cm; black (N 2.5/) very fine sandy loam, gray (N 5/) dry; massive; moderately fluid; few fine shell fragments; strongly saline; coarse tubular pores; color change with addition of hydrogen peroxide; slightly alkaline (pH 7.5); strongly acid (pH 5.1) after 8 weeks; abrupt boundary. (8 to 26 cm thick.)

CAse--19 to 41 cm; very dark gray (5Y 3/1) loamy fine sand, massive; nonfluid; strongly saline; few macroalgal fragments; neutral (pH 7.2); ultra acid (pH 3.3) after 8 weeks; clear boundary. (11 to 36 cm thick.)

Cse--41 to 56 cm; dark gray (5Y 4/1) fine sand, massive; nonfluid; moderately saline; neutral (pH 6.7); ultra acid (pH 3.3) after 8 weeks; clear boundary. (15 to 180 cm thick.)

CA'se--56 to 81 cm; very dark gray (5Y 3/1) very fine sandy loam, massive; nonfluid; moderately saline; few fine and medium shell fragments; slightly alkaline (pH 7.7); ultra acid (pH 3.2) after 8 weeks; clear boundary. (0 to 25 cm thick.)

C'se--81 to 97 cm; dark gray (5Y 4/1) loamy fine sand, massive; nonfluid; moderately saline; slightly alkaline (pH 7.8); ultra acid (pH 3.0) after 8 weeks; clear boundary.

Cg--97 to 152 cm; gray (2.5Y 5/1) fine sand, massive; nonfluid; moderately saline; few fine and medium shell fragments; common fine macroalgal fragments throughout; moderately alkaline (pH 8.0); neutral (pH 7.3) after 8 weeks; clear boundary.

C1--152 to 223 cm; very dark gray (5Y 3/1) loamy fine sand, massive; nonfluid; moderately saline; few fine shell fragments; moderately alkaline (pH 8.1); neutral (pH 7.1) after 8 weeks; clear boundary. (Combined thickness of C'g horizons is 0 to 60 cm.)

2C2--223 to 276 cm; very dark gray (5Y 3/1) very fine sandy loam, massive; nonfluid; moderately saline; few fine shell fragments; strongly alkaline (pH 8.5); slightly alkaline (pH 7.4) after 8 weeks; clear boundary.

2C3--276 to 303 cm; very dark gray (5Y 3/1) very fine sandy loam, massive; slightly fluid; moderately saline; few fine shell fragments; strongly alkaline (pH 8.5); extremely acid (pH 4.3) after 8 weeks.

TYPE LOCATION: Washington County, Rhode Island; located in Point Judith Pond, Bluff Hill Cove about 1100 feet southeast of intersection of East Shore Road and Goose Island Road, and about 850 feet southwest of end of Knowlesway Ext. USGS Narragansett Pier, RI topographic quadrangle, Latitude 41 degrees, 23 minutes, 19 seconds N. and Longitude 71 degrees, 29 minutes, 49 seconds W., NAD 1983.

RANGE IN CHARACTERISTICS: The soils are permanently submerged. Reaction is neutral through strongly alkaline throughout the profile. One or more horizons within 50 cm of the soil surface has an oxidized pH of 4.0 or less. Soil has a 5:1 salinity greater than 0.6 dS/m throughout the profile. Structure is massive or single grain throughout. Gravel content is 0 through 5 percent throughout the profile. The weighted average for shell content is 0 through 34 percent within the particle size control section. Individual horizons may contain up to 50 percent shells.

The A or Ase horizon has a hue of 5Y, or is neutral, value of 2.5 through 4, and chroma of 0 through 2. Texture is loam, silt loam, or fine sandy loam, sandy loam, fine sand and their mucky analogs. Oxidized pH is extremely acid through slightly alkaline.

The CAse or ACse horizons where present have a hue of 5Y or 2.5Y, value of 2.5 or 3, and chroma of 1 or 2. Texture is silt loam, very fine sandy loam through loamy fine sand. Oxidized pH is ultra acid through very strongly acid.

The C or Cse horizons have hue of 2.5Y, 5Y, or is neutral, value of 3 through 5, and chroma of 0 or 1. Texture is loam, very fine sandy loam, loamy very fine sand through fine sand. Consistence is nonfluid or slightly fluid. Oxidized pH is ultra acid through moderately alkaline.

The 2C or 2Cse horizons, where present, has hue of 5Y, value of 3 or 4, and chroma of 1. Texture is silt loam, very fine sandy loam, loamy very fine sand, or sand. Oxidized pH is extremely acid through slightly alkaline.

Some pedons contain one or multiple buried A or Ase horizons.

COMPETING SERIES: This is the Fort Neck series. Fort Neck soils are found on lagoon bottoms and contain a lithologic discontinuity with a submerged and buried subaerial soil.

The Saltpond series are in closely related families. Saltpond soils are on coastal plains and barrier islands and do not have a positive water potential at the soil surface for 90 percent of each day.

GEOGRAPHIC SETTING: Marshneck soils are permanently submerged with up to 2.5 meters of salt or brackish water on flood tidal delta slopes and shoals in coastal lagoons and bays. The soils formed in loamy and fine sandy estuarine and marine sediments. Slope ranges from 2 through 5 percent.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anguilla, Massapog, Pishagqua, Nagunt, and Napatree soils. Massapog soils are found on flood tidal delta flats in coastal lagoons and have a sandy particle size control section. Pishagqua soils are found on low energy lagoon bottoms and have greater than 100 cm of highly fluid, sulfidic, silt loam at the soil surface. Nagunt soils are found on washover fan flats and slopes in coastal lagoons and contain sulfidic materials within 100 cm of the soil surface. Napatree and Anguilla soils are on submerged headlands and submerged mainland beaches and have a lithologic discontinuity within 100 cm of the soil surface.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Subaqueous, peraquic moisture regime, moderately high or high saturated hydraulic conductivity. Soil is permanently submerged with salt or brackish water.

USE AND VEGETATION: This soil supports submerged aquatic vegetation and aquatic habitats. The area is important habitat for with native rooted eelgrass (Zostera marina). Vegetative cover ranges from 0 through 90 percent.

DISTRIBUTION AND EXTENT: New London County, Connecticut, and Rhode Island. MLRA 144A and 149B. The soils of this series are not extensive (total extent is about 100 acres (40 hectares)).

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Amherst, Massachusetts.

SERIES ESTABLISHED: Washington County, Rhode Island, 2010.

REMARKS: This subaqueous series is being proposed in areas previously mapped as water in the Rhode Island and Connecticut Soil Surveys.

Diagnostic horizons and features in this pedon include:
1. Peraquic feature - positive soil water potential (permanently submerged) at the soil surface (under 0.6 m of water at the time of coring).
2. Ochric epipedon - the zone from 0 to 19 cm (A horizon).
3. Sulfidic materials - the zone from 19 to 97 cm (CAse, Cse, CA'se, and C'se horizons).
4. High n-value - the zone from 0 to 19 cm (A horizon) has an n-value greater than 0.7, as surmised by the moderately fluid manner of failure.
5. Haplic Feature - the zone from 19 to 303 has an n-value of 0.7 or less.
6. Particle size control section - the zone from 25 to 100 cm (part of the CAse, Cse, CA'se, C'se, and part of the Cg horizons).

ADDITIONAL DATA: Pedon sample RI009-2007-014-PJ in Washington County, Rhode Island, by University of Rhode Island. Additional pedons used to determine ranges include RI009-2000-002-NP, RI009-2007-012-PJ, RI009-2007-005-PJ, and RI009-2006-015-QP (Sampled by the University of Rhode Island).


National Cooperative Soil Survey
U.S.A.