LOCATION Napatree CT RI
Tentative series
Rev. DAS/SJM
1/07

NAPATREE SERIES
The Napatree series consists of very deep, subaqueous soils in bouldery, mainland coves adjacent to glaciated uplands with numerous boulders and stones. The Napatree soils are formed in sandy marine deposits overlying submerged terrestrial till deposits. Slope ranges from 0 to 2 percent, mean annual air temperature is about 10 degrees C., and mean annual precipitation is about 1142 mm.

TAXONOMIC CLASS: Coarse-loamy, mixed, active, nonacid, mesic Aeric Endoaquents.

TYPICAL PEDON: Napatree sand on a south facing, bouldery 2 percent slope in a submerged headland under 1.6 m of estuarine water (Colors are for moist soil).

Ag—0 to 20 cm; black (N 2.5/) sand; single grain; nonfluid; many fine distinct olive brown (2.5Y 4/4) iron accumulations; 10 percent gravels; 5 percent shell fragments; sulphurous odor; strongly saline (28ppt); neutral (pH 6.9); very strongly acid (pH 5.0) after 8 weeks; clear boundary. (15 to 30 cm thick)

C1—20 to 32 cm; olive brown (2.5Y 4/3) loamy sand; single grain; nonfluid; 10 percent gravels; strongly saline; neutral (pH 6.9); moderately acid (pH 6.0) after 8 weeks; clear boundary.

C2—32 to 45 cm; olive brown (2.5Y 4/3) gravelly sandy loam; massive; nonfluid; common fine faint olive brown (2.5Y 4/4) masses of iron accumulation; 18 percent gravels; strongly saline; neutral (pH 7.2); very strongly acid (pH 6.2) after 8 weeks; abrupt boundary. (Combined thickness of the C horizons is 20 to 35 cm thick).

2Cgb1—45 to 58 cm; dark grayish brown (2.5Y 4/2) silt loam; massive; nonfluid; many fine distinct gray (5Y 5/1) iron depletions; strongly saline; slightly alkaline (pH 7.4); neutral (pH 6.8) after 8 weeks; clear boundary.

2Cgb2—58 to 65 cm; gray (5Y 5/1) silt loam; massive; nonfluid; common fine distinct light olive brown (5Y 5/4) iron accumulations; strongly saline; slightly alkaline (pH 7.4); neutral (pH 6.8) after 8 weeks; abrupt boundary. (Combined thickness of the 2Cg horizons is 10 to 50 cm thick).

3Cgb1—65 to 120 cm; dark grayish brown (2.5Y 4/2) very gravelly loamy sand; single grain; nonfluid; 40 percent gravels; strongly saline; neutral (pH 7.2); neutral (pH 6.9) after 8 weeks.

TYPE LOCATION: New London County, Connecticut; located about 4910 feet southeast of the Barn Island boat launch and 7260 feet southwest of the intersection of Green Haven Road and Osbrook Point Road, just south of Perch Island, USGS Watch Hill topographic quadrangle; lat. 41 degrees 19 minutes 59 seconds N. and long. 71 degrees 51 minutes 90 seconds W., NAD 83.

RANGE IN CHARACTERISTICS: The soils are permanently submerged except for some of the surface boulders that are exposed to the air during low tides. All horizons have a pH of neutral through slightly alkaline and a pH of very strongly acid through neutral after 8 weeks incubation. Electrical conductivity is >16 mmhos/cm and salinity is >20 ppt (strongly saline) throughout the profile.

The Ag and ACg horizons, when present, have hues of N, 5GY, or 10YR, value of 2.5 or 3, and chroma of 0 through 2. It is sandy loam, loamy coarse sand, sand, or coarse sand. Organic matter is 0 to 2 percent. Consistence is nonfluid. Gravel content is 0 to 10 percent. Shell fragment content is 0 to 10 percent. Redoximorphic features may be present.

The C horizon has hue of 2.5Y or 5Y, value of 4, and chroma of 3 or 4. It is sandy loam or loamy sand along with gravelly analogs. Consistence is nonfluid. Gravel content is 0 to 20 percent.

The 2Cgb horizon has hue of 10YR, 10Y, 2.5Y or 5Y, value of 4 or 5, and chroma of 1 through 2. It is silt loam, fine sandy loam, loamy fine sand, and loamy sand. Consistence is nonfluid. Gravel content is 0 to 10 percent. Redoximorphic features may be present.

The 3Cgb horizon, when present, has hue of 10YR, 10Y, 2.5Y or 5Y, value of 4 or 5, and chroma of 1 through 2. It is very fine sandy loam and loamy sand along with gravelly or very gravelly analogs. Consistence is nonfluid. Gravel content is 0 to 40 percent. Redoximorphic features may be present.

The 2Cb horizon, when present, has hue of 10YR, 2.5Y or 5Y, value of 3 or 4, and chroma of 3 or 4. It is loamy sand, loamy coarse sand, loamy very coarse sand, sand, or coarse sand. Consistence is nonfluid. Gravel content is 0 to 5 percent.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: The Napatree soils are permanently submerged with salt or brackish water in bouldery glacial deposits adjacent to glaciated uplands with numerous boulders and stones. The surface boulders are often exposed to the air at low tides. Slope ranges from 0 to 2 percent. The soils formed in submerged terrestrial soils with a capping of sandy marine deposits and can be found up to 2.5 meters deep under water. The potential for submarine fresh ground water discharge zones are high given the geomorphic position and high to very high saturated hydraulic conductivity.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anguilla (T) and Quanaduck (T) soils. The Anguilla soils are on mainland cove landforms, have a contrasting particle-size class family of sandy and sulfidic materials in the soil profile. Quanaduck soils are on submerged inland bay coves and have sulfidic materials in the soil profile.

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

USE AND VEGETATION: These soils are used for recreation and wildlife habitat. Shellfish cultivation, which includes lobsters, hard-clams, and oysters, is very important in these soils. Aquaculture in Connecticut has for the last 150 years traditionally harvested native set shellfish from the bottom. Connecticut's oysters are among the most valued oysters reared in the United States. In addition fishing is commonplace and the species found in the area are smelt, small cod, flounder, scup, menhaden, and white perch. Some areas are vegetated with native rooted and floating algae and eelgrass (Zostera marina). Vegetative cover ranges from 0 to 15 percent.

DISTRIBUTION AND EXTENT: Permanently submerged terrestrial soils with a capping of marine deposits in MLRA 144A. The soils of this series are of small extent, approximately 90 hectares mapped in Little Narragansett Bay.

MLRA OFFICE RESPONSIBLE: Amherst, Massachusetts.

SERIES PROPOSED: New London County, Connecticut, 2006. The name is taken from Napatree Point, located in Rhode Island.

REMARKS: The Keys to Soil Taxonomy, Tenth Edition, 2006 states that the horizontal boundaries of soil are areas where the soil grades into deep water (typically less than 2.5 m). This subaqueous series is being proposed in areas previously mapped as water in the Connecticut Soil Survey.

Using the proposed taxonomy for subaqueous soils, the series classifies as a coarse-loamy, mixed, active, nonacid, mesic Aeric Haplowassents.

Diagnostic horizons and features in this pedon include:

1. Peraquic feature - positive soil water potential (permanently submerged) at the soil surface. (under 1.6 m of water at the time of coring).

2. Particle-size control section – the zone from 25 to 100 cm (part of C1, C2, 2Cgb1, 2Cgb2, and part of 3Cgb1 horizons).

3. Ochric epipedon – the zone from 0 to 20 cm (Ag horizon).

3. Aeric feature – chroma of 3 in the zone from 20 to 45 cm (C1 and C2 horizons).

4. Lithologic discontinuity – Contrasting soil materials at 45 cm and 65 cm (the 2Cgb1 and 3Cgb1 horizons).

National Cooperative Soil Survey
U.S.A.