LOCATION FAIRFAX                 VA+KY MD

Established Series
Rev. JHE-DDR
02/2022

FAIRFAX SERIES

Soils of the Fairfax series are deep and well drained. The upper part of the solum is formed in a silty fluvial mantle. The lower part of the solum is formed in materials weathered from schist and gneiss. They are nearly level to moderately sloping soils on the Piedmont uplands. Slope ranges from 0 to 15 percent. Mean annual precipitation is about 107 cm and mean annual temperature is about
13 degrees C.

TAXONOMIC CLASS: Fine, mixed, subactive, mesic Typic Hapludults

TYPICAL PEDON: Fairfax silt loam - forested
(Colors are for moist soil.)

O1---0 to 3 cm; very dark grayish brown (10YR 3/2) partly decayed leaves and twigs, laced with very fine and fine roots.

A1---3 to 6 cm; dark grayish brown (10YR 4/2) silt loam; strong fine granular structure; very friable; many fine and medium roots; very strongly acid; clear smooth boundary. (0 to 8 cm thick)

A2---6 to 26 cm; brown (10YR 5/3) silt loam; moderate fine granular structure; friable; many fine and medium roots; few fine pores; few very fine flakes of mica; 1 percent subangular rounded quartz pebbles less than 3 cm across; very strongly acid; clear smooth boundary. (0 to 20 cm thick)

B1t--26 to 36 cm; yellowish brown (10YR 5/6) silty clay loam; weak medium subangular blocky structure; firm, sticky, plastic; common fine and medium roots; few fine pores; few very fine flakes of
mica; 1 percent fine subangular rounded quartz pebbles less than 3 cm across; few thin patchy clay films on faces of peds; very strongly acid; clear smooth boundary. (10 to 15 cm thick)

B21t--36 to 51 cm; strong brown (7.5YR 5/6) silty clay loam; moderate fine subangular blocky structure; firm, sticky, plastic; common fine and medium roots; few fine pores; few very fine flakes of mica; 2 percent fine subangular rounded quartz pebbles less than 3 cm across; thin patchy clay films on faces of peds; very strongly acid; clear smooth boundary. (15 to 25 cm thick)

IIB22t--51 to 64 cm; strong brown (7.5YR 5/6) gravelly silty clay loam; few fine faint pale brown (10YR 6/3) mottles; moderate fine subangular blocky structure; firm, sticky, plastic; slightly compact, slightly brittle; few fine and medium roots; few fine pores; few very fine flakes of mica; 20 percent rounded quartz pebbles less than 8 cm across; thin patchy clay films on faces of peds; very strongly acid; clear smooth boundary. (10 to 20 cm thick)

IIIB23t--64 to 94 cm; yellowish red (5YR 5/6) silty clay loam; few fine distinct reddish yellow (7.5YR 6/6) mottles; strong fine angular blocky structure; firm, sticky, plastic; few fine and medium roots; few fine pores; common very fine flakes of mica; thin continuous clay films on faces of peds; very strongly acid; clear smooth boundary. (25 to 36 cm thick)

IIIB3t--94 to 103 cm; yellowish red (5YR 5/6) silty clay loam; common medium distinct strong brown (7.5YR 5/6) mottles; moderate fine angular blocky structure; firm, sticky, plastic; few fine pores; common very fine flakes of mica; thin patchy clay films on faces of peds; very strongly acid; gradual smooth boundary. (5 to 15 cm thick)

IIIC--103 to 200 cm; strong brown (7.5YR 5/6), yellowish red (5YR 5/6) and weak red (10YR 5/3) silt or silt loam; very strongly weathered schist; structureless; friable; many very fine flakes of mica; very strongly acid.

TYPE LOCATION: Fairfax County, Virginia, 20 m south of Braddock Road, 490 m east of Route 123.

RANGE IN CHARACTERISTICS: Solum thickness ranges from 80 to 160
cm. Depth to B horizons developed in unconforming materials range from 30 to 90 cm. Depth to bedrock is more than 150 cm. The A horizon and upper part of the Bt horizon range from less than 1 percent to 6 percent of subangular rounded quartz pebbles and
range from 15 to 30 percent at the contact of the unconforming material. The lower part of the Bt horizon is commonly free of pebbles. Some pedons have flakes of mica throughout the soil.
These soils are very strongly acid or strongly acid throughout, unless limed.

The A horizon has hue of 10YR, value of 3 through 6 and chroma of
2 through 6. The A2 horizon, when present, includes chroma of 8. The A horizon is sandy loam, fine sandy loam, loam or silt loam.

The Bt horizon, above the unconforming materials, has hue of 7.5YR
or 10YR, value of 5 or 6 and chroma of 6 or 8. It is silty clay loam, clay loam, or clay.

The IIB horizon has hue of 5YR, 7.5YR or 10YR, value of 4 through
6, and chroma of 6 or 8. Some pedons have high chroma mottles.
It is silty clay loam, clay loam, clay or silt loam in the
fine-earth fraction.

The IIIB horizon has hue of 2.5YR or 5YR, value of 4 or 5 and
chroma of 6 or 8. It has high chroma mottles and is silty clay
loam or clay loam.

The C horizon is multicolored, very strongly weathered schist or gneiss. It is sandy loam, silt loam, loam or clay loam.

COMPETING SERIES: These are the Agnos, Appling, Boden, Braddock, Gassville, Groseclose, Howell, Monmouth, Muse, Pervinia, Sequoia, Trappist, and Unison. Agnos, Boden, Gassville, Groseclose, Muse, Pervinia, Sequoia, and Trappist soils have coarse fragments of sedimentary rocks. Appling soils do not have a lithologic discontinuity in the control section. Braddock soils have red B2 horizons. Howell and Monmouth soils have hue of 2.5Y or 5Y in the lower part of the B horizon. Unison soils have coarse fragments
of dominantly rounded and subrounded greenstone and granodiorate.

GEOGRAPHIC SETTING: Fairfax soils are on nearly level to
moderately sloping Piedmont uplands. Slopes range from 0 to 12 percent. The upper part of the solum is formed in a silty fluvial mantle and the lower part is formed in residuum weathered from
schist and gneiss. The mean annual temperature is 13 degrees C and mean annual precipitation is about 107 cm.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beltsville,
Elioak, Glenelg, Glenville and Manor soils. In addition, the Appling, Nason and Tatum soils are associated with Fairfax near
the southern limit of its range. Beltsville and Glenville soils
have fragipans. Elioak and Tatum soils have red clayey Bt
horizons. Appling and Nason soils have yellowish red or strong
brown Bt horizons. Manor soils have thin silt loam cambic
horizons.

DRAINAGE AND PERMEABILITY: Well drained. Runoff is medium. Permeability is moderate.

USE AND VEGETATION: Fairfax soils are used primarily for growing corn, small grains, hays and pasture. Many of the soils are under urban development. Wooded areas are in oak, hickory, Virginia
pine and poplar.

DISTRIBUTION AND EXTENT: Northern Virginia and possibly Maryland. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia

SERIES ESTABLISHED: Fairfax County, Virginia; Northern Virginia
Soil Conservation District, 1956.

REMARKS: Reclassified in 1981, from fine-loamy to clayey. Basedo n lab data from the typical pedon of the established series and five satellite pedons.

2/2022 revision: Oi had 3 to 0 centimeter depths, corrected to be 0 to 3 cm horizon depths then added 3 cm to all horizon depths throughout the typical pedon.wjn

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National Cooperative Soil Survey
U.S.A.