The Osan series are members of the coarse loamy, mixed, mesic family of Typic Dystrudepts [Haplic Cambisols (Alumic Humic Dystric Siltic Chromic) classified by WRB]. These soils have strong brown gravelly loam A horizons, yellowish red gravelly loam BA horizons, yellowish red gravelly loam Bw1 horizons, yellowish red gravelly loam Bw2 horizons, and reddish brown gravelly sandy loam BC horizons. They are developed in mountainous areas and are derived from residual granite gneiss, micaceous schist and schist rocks.

Typifying pedon: Osan gravelly loam-forest (Colors are for moist soil).

  Slope: 30-60%

  Soil moisture regime: Udic

  Siol temperature regime: Mesic

  Parent material: Residuum on granite gneiss

  Diagnostic features : An ochric epipedon from a depth of 0 to 17 cm and a cambic horizon from a depth of 34 to 102 cm (A cambic horizon from a depth of 34 to 102 cm by WRB).

  Described by: Song, K. C., S. J. Jung , and D. C. Noh,  24 Sep., 2009.

A  - 0 to 17 cm. Strong brown (10YR 5/4) gravelly loam; moderate fine to medium granular structure; firm, sticky and plastic; many fine to medium tree roots; common fine to medium pores; 10% gravels; clear smooth boundary.

BA - 17 to 34 cm. Yellowish red (5YR 4/6) gravelly loam; moderate medium to coarse subangular blocky structure; firm, sticky and plastic; many medium to coarse tree roots; common fine to medium pores; 15% gravels; gradual smooth boundary.

Bw1 - 34 to 60 cm. Yellowish red (5YR 4/6) gravelly loam; weak fine to medium subangular blocky structure; firm, sticky and plastic; common fine to medium roots; common fine to medium pores; 15% gravels; clear smooth boundary.

Bw2 - 60 to 102 cm. Yellowish red (5YR 5/6) gravelly loam; weak fine to medium subangular blocky structure; firm, sticky and plastic; common fine to medium roots; common fine to medium pores. 20% gravels; clear smooth boundary.

BC - 102 to 180 cm. Reddish brown (5YR 4/4) gravelly sandy loam; weak fine to medium subangular blocky structure; firm, sticky and plastic; few fine to medium roots; few fine pores. 20% gravels.

  The typifying pedon has an ochric epipedon from a depth of 0 to 17 cm and a cambic horizon from a depth of 34 to 102 cm. That can be classified as Inceptisol. It has an udic soil moisture regime and keys out as Udept. Also it meets the requirements of Typic Dystrudept. The typifying pedon has coarse loamy particle-size class and mesic soil temperature class. Therefore it can be classified as coarse loamy, mixed, mesic family of Typic Dystrudept.

Type Location: About 700 meters west of the Saam 7 Ri Maeulhoegwan, Saam Ri, Wonsam Myeon, Yongin city, Gyeonggi Do (127^o 17' 59.6'', 37^o 10' 56.9'').

Range in Characteristics: These soils have ochric epipedons and cambic horizons. The solum thickness ranges from 100 to 200 cm. Depth to hardrock is more than 2 meters. Common fine to medium white and yellow micas are throughout the profiles. Base saturation is less than 60 percent. Reaction is ver strongly to strongly acid. A horizons are strong brown gravelly loam, silt loam, or sandy loam. Cambic B horizons are yellowish red, reddish brown, or dark red gravelly loam or silt loam.

Competing Series and Their Differentiae: The Songsan, Daesan, and Ulsan series are similar. The Songsan soils are derived from metamorphic rocks such as biotite, granite-gneiss and schist. The Daesan soils are derived from phyllite or schist of Ogcheon system. The Ulsan soils are derived from porphyritic materials.

Setting: The Osan soils occur chiefly in moderately steep to steep mountainous areas underlain by granite gneiss, schist and micaceous schist. Dominant slopes are 15 to 60 percent and range from 7 to 100 percent.

Principal Associated Soils: The Wongog, Pogog and Seongsan soils are associated in local valley alluvial-colluvial and foot slope position. The Songjeong and Yesan soils are associated on similar and steeper slopes.

Drainage and Permeability: Well drained. Permeability is probably moderate and runoff is rapid.

Use and Vegetation: Most of these soils grow pine forest, shrub, wild grasses, and some mixed forest.

Distribution and Extent: The Osan soils are of moderate extent and distributed in mountainous areas with granitic gneiss geology throughout the country.

Series Established: Bucheon city, Gyeonggi Do, 1969. Revised, Yongin city, Gyeonggi Do, 2009.

Laboratory data sheets of typifying pedon.