LOCATION SUNKEN                  MD+DE

Established Series
SYD-RBT/Rev. ATD
02/2025

SUNKEN SERIES

MLRAs--149A, 153C, and 153D
Depth class--Very deep
Drainage class--Very poorly drained
Flooding--Occasional, for very brief durations (tidal)
Parent material--Silty eolian deposits over loamy or sandy fluviomarine deposits
Slope--0 to 2 percent
Elevation--0 to 1 meter
Mean annual air temperature--13 degrees C (56 degrees F)
Mean annual precipitation--1144 millimeters (45 inches)

TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Typic Endoaqualfs

TYPICAL PEDON: Sunken mucky silt loam on a smooth 0 percent slope in a submerging upland. (Colors are for a moist soil.)

Oi--0 to 5 centimeters; dark reddish brown (5YR 2.5/2) peat; fiber content is 75 percent of the soil volume after rubbing; von Post value H2; many fine, medium, and coarse roots throughout; neutral (pH 7.0); clear smooth boundary. (thickness range is 3 to 10 centimeters)

Oa--5 to 10 centimeters; very dark brown (10YR 2/2) muck; fiber content is 10 percent of the soil volume after rubbing; von Post value H8; common fine and medium roots throughout; neutral (pH 7.0); clear smooth boundary. (thickness range is 0 to 15 centimeters)

Ag--10 to 15 centimeters; grayish brown (10YR 5/2) silt loam; massive; friable, slightly sticky, slightly plastic; common very fine and fine, few medium roots throughout; common fine and few medium pores; neutral (pH 7.0); clear smooth boundary. (thickness range is 5 to 20 centimeters)

Eg--15 to 46 centimeters; gray (10YR 6/1) silt loam, massive; friable, moderately sticky, moderately plastic; common very fine, fine, and medium roots throughout; common fine and few medium and very fine pores; common medium prominent noncoherent cemented yellowish red (5YR 5/8) iron-manganese concentrations; neutral (pH 7.0); gradual wavy boundary. (thickness range is 20 to 36 centimeters)

Btg1--46 to 97 centimeters; gray (10YR 6/1) silty clay loam; massive; firm, moderately sticky, moderately plastic; few medium and fine roots throughout; common fine and few medium pores; few faint clay films on faces of peds; common medium prominent strong brown (7.5YR 5/8) and common medium prominent brownish yellow (10YR 6/8) iron concentrations; slightly acid (pH 6.3); gradual wavy boundary. (38 to 74 centimeters thick)

2Btg2--97 to 165 centimeters; gray (5Y 6/1) very fine sandy loam, massive; firm, slightly sticky, moderately plastic; common fine and very fine pores; few faint clay films on faces of peds; common medium prominent brownish yellow (10YR 6/8) iron concentrations; moderately acid (pH 5.8); gradual smooth boundary. (43 to 76 centimeters thick)

2Cg--165 to 200 centimeters; light olive gray (5Y 6/2) fine sand, massive; common coarse prominent yellowish brown (10YR 5/6) iron concentrations; slightly acid (pH 6.3).

TYPE LOCATION:
Dorchester County, Maryland; in Blackwater National Wildlife Refuge - Area M2 Moneystump Swamp, approximately 486 meters northeast of the Smithville Bridge boat ramp, approximately 205 meters east-southeast of the intersection of Smithville Road and an unnamed dirt wildlife refuge access road (signed Area M2 Moneystump Swamp) on the south side of the access road and approximately 87 meters south from the dirt road edge. USGS Topographic Quadrangle--Golden Hill, Maryland

Latitude--38.4316667
Longitude-- -76.2327778
Datum--WGS84
Coordinate source--Manually entered from GPS

RANGE IN CHARACTERISTICS:
Depth to bedrock--Greater than 200 centimeters
Depth to top of the argillic--38 to 61 centimeters
Depth to base of the argillic--142 to 178 centimeters
Solum Thickness--102 to 205 centimeters
Thickness of organic soil material--0 to less than 20 centimeters (some pedons do not have an organic surface)
Reaction--Moderately acid to neutral (pH 5.6 to 7.3) below 46 centimeters, strongly acid to neutral (pH 5.1 to 7.3) above 46 centimeters
Electrical conductivity--2 to 8 ds/m in the mineral horizons and greater than 8 dS/m (5.6 ppt) in the organic horizons
Total sulfur content, organic horizons--0.50 percent to 1.5 percent
Total sulfur content, mineral horizons--0.05 percent to 0.50 percent
Fluidity--Nonfluid but some mineral horizons could be slightly fluid
Organic carbon stock 0 to 100 centimeters--14 to 27 kg m-2
Organic carbon stock 0 to 200 centimeters--19 to 33 kg m-2
Other Soil Features--Structure and clay films are faint or not visible in the subsoil horizons because of clay dispersion due to the presence of soluble salts.

Oa, Oe, or Oi horizons (where present):
Hue--5YR to 5Y
Value--2 or 3
Chroma--2 to 4
Texture--peat or muck, or less commonly mucky peat
Von Post--H2 to H8
Organic carbon density--19 to 122 kg m-3

Ag horizon:
Hue--10YR to 5Y
Value--3 to 6
Chroma--1 or 2
Texture--loam or silt loam
Organic carbon density--4 to 61 kg m-3

Eg horizon:
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--1 to 3
Texture--loam or silt loam
Redoximorphic features (where present)--iron concentrations in shades of red, yellow, or brown and iron depletions in shades of brown, yellow, olive, or gray
Organic carbon density--4 to 21 kg m-3

Btg horizon:
Hue--10YR or 2.5Y
Value--5 or 6
Chroma--1 or 2
Texture--silt loam or silty clay loam
Redoximorphic features (where present)--iron concentrations in shades of red, yellow, or brown and iron depletions in shades of brown, yellow, olive, or gray
Organic carbon density--1 to 14 kg m-3

2Btg horizon:
Hue--10YR to 5Y
Value--5 to 7
Chroma--1 or 2
Texture--fine sandy loam to very fine sandy loam
Redoximorphic features (where present)--iron masses in shades of red, yellow, or brown and iron depletions in shades of brown, yellow, olive, or gray
Organic carbon density--1 to 14 kg m-3

2Cg horizon:
Hue--10YR to 5Y
Value--5 to 7
Chroma--1 or 2
Texture--fine sand to loamy sand
Redoximorphic features (where present)--iron masses in shades of red, yellow, or brown and iron depletions in shades of brown, yellow, olive, or gray
Organic carbon density-0.5 to 14 kg m-3

COMPETING SERIES:
These are the Baylock, Ginat, and Laconia Soils.
Baylock soils--formed in loess or silty alluvium over silty and loamy alluvium, occur on stream terraces and do not receive tidal flooding
Ginat soils--formed in silty alluvium over silty, loamy, and clayey alluvium along the Ohio River and have a shallower argillic horizon
Laconia soils--have a 2Btg horizon with a higher content of clay; occur in depressions on karst landscapes and do not have tidal flooding

GEOGRAPHIC SETTING:
Parent material--Silty eolian deposits over loamy or sandy fluviomarine deposits
Landscape--Coastal plain
Landform--Submerged upland tidal marshes, ghost forests
Slope range--0 to 2 percent
Elevation--0 to 1 meter
Mean annual air temperature--11 to 15 degrees C (52 to 59 degrees F)
Mean annual precipitation--1052 to 1240 millimeters (41 to 49 inches)
Frost free period--190 to 260 days

GEOGRAPHICALLY ASSOCIATED SOILS:
These are the Bestpitch, Elkton, Honga, Othello, Tangier, and Transquaking soils.
Bestpitch soils--have 40 to 130 centimeters of organic soil materials and 35 percent or greater clay content (clayey) in the underlying mineral soil materials, on slightly lower tidal marsh landforms
Elkton and Othello soils--are poorly drained, not tidally flooded, not saline or brackish, and are on slightly higher landforms
Honga soils--have 40 to 130 centimeters of organic soil materials and loamy underlying mineral materials, on slightly lower positions on similar landforms
Tangier soils--have higher salt content (EC greater than 8 dS/m throughout), on slightly lower positions on similar landforms
Transquaking soils--have greater than 130 centimeters of organic soil materials, on slightly lower tidal marsh landforms

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage Class--Very poorly drained
Saturated Hydraulic Conductivity--Moderately low to moderately high
Soil Moisture Regime--Peraquic (continuously saturated throughout)
Flooding--Occasional, very brief durations (tidal)

USE AND VEGETATION:
Major Uses--Sunken soils are mainly used for their important ecological and environmental benefits as wetland wildlife habitat. Sunken soil mapunit areas are experiencing tidal salt marsh ecosystem conversion as the marsh is slowly migrating to these low-lying upland forested areas. Sunken soils provide essential plant and animal habitat, water quality benefits, and coastal protection from storms and sea level rise.
Natural Vegetation--Typically consist of stunted loblolly pine (Pinus taeda), saltmeadow cordgrass (Spartina patens), saltgrass (Distichlis spicata), marsh-elder (Iva frutescens), poison ivy (Rhus radicans), and groundsel-tree (Baccharis halimifolia).

DISTRIBUTION AND EXTENT:
General area--Coastal plain of Maryland and Delaware
Land Resource Regions (LRR)-- S - Northern Atlantic Slope Diversified Farming Region and T - Atlantic and Gulf Coast Lowland Forest and Crop Region
MLRA(s)--149A, 153C, 153D
Extent--Moderate

MLRA SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: SPECIAL PROJECTS OFFICE

SERIES ESTABLISHED: Dorchester County, Maryland, 1992. The name is coined from the Sunken Island Marsh.

REMARKS:
Sunken soils were previously mapped as Tidal Marsh and Swamp miscellaneous areas and with the Elkton and Othello soil series as inclusions in the low phase map units. These soils may become extremely acid if drained. Sunken soils are classified as Alfisols due to elevated base saturation (35 percent or greater) resulting from saturation with base-rich saline water (sum of base saturation analysis conducted at the University of Maryland in 1988 on samples averaged 63 percent).

Diagnostic horizons and features recognized in this pedon (Keys to Soil Taxonomy, Thirteenth Edition):
Aquic conditions--the zone from 0 to 200 centimeters is continuously saturated (endosaturation)
Fibric soil materials--the zone from 0 and 5 centimeters has a fiber content after rubbing that is three-fourths, by volume
Sapric soil materials--the zone from 5 to 10 centimeters has a fiber content after rubbing that is less than one-sixth, by volume
Ochric epipedon--the zone from 0 to 46 centimeters (Oi, Oa, Ag, Eg horizons)
Argillic horizon--the zone from 46 to 165 centimeters (Btg1 and 2Btg2 horizons)
Lithologic discontinuity--97 to 200 centimeters
Particle size control section--46 to 96 centimeters (Btg1 horizon)

ADDITIONAL DATA:

NASIS site and pedon ID for typical pedon: 2007MD019001

Refer to publication "Tidal Marsh Soils of Maryland", Darmody, R.G. and Foss, J.E., Maryland Agricultural Experiment Station Publication MP 930, October 1978.
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National Cooperative Soil Survey
U.S.A.