LOCATION OLEQUA WAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Xeric Palehumults
TYPICAL PEDON: Olequa silt loam, forest. (Colors are for moist soil unless otherwise stated.)
Oe--2 inches to 0; needles, moderately decomposed leaves and twigs.
Ac1--0 to 3 inches; very dark brown (10YR 2/2) silt loam, gray (10YR 5/1) dry; moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; common 1 to 3 mm shot; neutral (pH 6.7); clear wavy boundary. (2 to 5 inches thick)
Ac2--3 to 10 inches; dark brown (10YR 3/3) silt loam, brown (10YR 5/3) dry; strong very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; common 1 to 3 mm shot; slightly acid (PH 6.4); gradual wavy boundary. (6 to 10 inches thick)
BA--10 to 20 inches; dark brown (7.5YR 3/4) heavy silt loam, pale brown (10YR 6/3) dry; strong fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; few 1 to 3 mm shot; many fine tubular pores; moderately acid (pH 5.8); clear wavy boundary. (8 to 12 inches thick)
Bt1--20 to 36 inches; dark brown (10YR 4/3) silty clay loam, light yellowish brown (10YR 6/4) dry; moderate medium and fine subangular blocky structure; hard, firm, sticky and plastic; common roots; many fine tubular pores; common faint patchy clay films on faces of peds and in pores; moderately acid (pH 5.6); clear wavy boundary. (14 to 17 inches thick)
Bt2--36 to 51 inches; dark yellowish brown (10YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry, few fine faint dark brown (7.5YR 3/4) mottles; moderate medium prismatic parting to moderate medium angular blocky structure; very hard, firm to very firm and brittle, slightly sticky and plastic; common fine roots along prism surfaces; many fine pores; many thin clay films in pores and common faint clay films on some faces of peds; very strongly acid (pH 5.0); gradual wavy boundary. (13 to 18 inches thick)
BCt--51 to 65 inches; dark brown (10YR 4/3) silt loam, very pale brown (10YR 7/3) dry, many medium distinct dark brown (7.5YR 3/4) mottles; massive or weak fine laminated structure; very hard, firm, slightly sticky and plastic; few roots; many fine tubular pores; common faint clay films in pores and root channels; strongly acid (pH 5.1).
TYPE LOCATION: Lewis County, Washington; about 1 mile north of Vader; 200 feet east, 700 feet north of SW corner section 20, T.11N., R.2W., WM.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 48 to more than 60 inches. Olequa soils are usually moist but are dry in all parts between depths of 4 and 12 inches for 45 to 60 consecutive days. Average annual soil temperature at depth of 20 inches ranges from 47 to 52 degrees F. The argillic horizon ranges from 20 to 35 percent clay and is silt loam or silty clay loam. The umbric epipedon is 10 to 15 inches thick.
The A horizon has value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 through 3 moist or dry. It has moderate to strong granular structure. This horizon is neutral or slightly acid.
The BA and Bt horizons have hue of 7.5YR or 10YR, value of 3 or 4 moist, 6 or 7 dry, and chroma of 3 or 4 moist or dry. It is silt loam or silty clay loam. Texture is silt loam or silty clay loam. This horizon has strong or moderate subangular blocky to prismatic or angular structure. It is moderately acid to very strongly acid.
The BCt horizon, when present, has value of 3 or 4 moist, 6 or 7 dry, and chroma of 3 or 4 moist or dry. It is silt loam or silty clay loam. Reaction is strongly acid or very strongly acid.
COMPETING SERIES: This is the Buckpeak series in a similar family. Buckpeak soils are fine-loamy.
GEOGRAPHIC SETTING: The Olequa soils occur at elevations of 40 to 300 feet and are on nearly level to moderately steep high terraces and on steep hillsides and terrace escarpments. These soils formed in old alluvium. They are in a humid marine climate with 40 to 60 inches annual precipitation occurring mostly as rain during the winter. The mean January temperature is 36 degrees F; the mean July temperature is 64 degrees F; and the mean temperature is 51 degrees F. The frost free season is 150 to 200 days. The growing season (28F) is 175 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Klaber, Newberg, Prather, Reed, Salkum, and Winston soils. Klaber and Reed soils have an aquic moisture regime. Newberg soils have a mollic epipedon and an irregular decrease in organic carbon. Prather soils are in a fine family and are moderately well drained. Salkum soils are in a clayey family. Winston soils have a spodic horizon and are coarse-loamy over sandy or sandy skeletal.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.
USE AND VEGETATION: Olequa soils are used for timber production, and where cleared they are used for for pasture, hay, small grains, and corn for silage. Native vegetation is Douglas fir, red alder, bigleaf maple, and western hemlock, with an understory of trailing blackberry, Oregongrape, violet, longtube twinflower, western swordfern, and western.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lewis County, Washington, 1941.
REMARKS: The classification is based on laboratory data on the associated Centralia soils (Lab number S84WA-15-005). Diagnostic horizons and features recognized in this pedon are an umbric epipedon from the mineral surface to 10 inches and an argillic horizon from 20 to 65 inches. The base saturation (by sum) is assumed to be less than 35 percent throughout the argillic horizon. These soils were previously classified fine-silty, mixed, mesic Xeric Haplohumults. Classification change based on National Soil Taxonomy Handbook, Issue No. 12, re- establishing Palehumults.