121 Classification of the Soils – Oatman Series

Classification of the Soils
Oatman Series

Depth class: Deep to a duripan (fig. 13)

Drainage class: Well drained

Permeability: Moderate

Position on landscape: Glaciated volcanic uplands

Parent material: Glacial deposits derived from andesite mixed with ash

Slope range: 5 to 60 percent

Elevation: 4,300 to 6,000 feet

Average annual precipitation: 30 to 50 inches

Average annual air temperature: 38 to 42 degrees F

Frost-free period: 10 to 50 days

Taxonomic class: Medial-skeletal, amorphic Xeric Haplocryands

Typical Pedon

Oi—0 to 1 inch; slightly decomposed needles and twigs.

Oe—1 inch to 2 inches; moderately decomposed needles and twigs.

A—2 to 3 inches; very dark brown (7.5YR 2.5/3) gravelly medial sandy loam, brown (10YR 4/3) dry; weak very fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine roots and few fine and medium roots; many very fine irregular pores; 20 percent andesite gravel, 5 percent subrounded andesite cobbles, and 1 percent subrounded andesite stones; moderately acid (pH 5.6); clear wavy boundary.

AB—3 to 12 inches; dark brown (7.5YR 3/3) very cobbly medial sandy loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and slightly plastic; many very fine and fine roots, common medium roots, and few coarse roots; roots and few coarse roots; many very fine tubular pores; 30 percent andesite gravel, 20 percent subrounded andesite cobbles, and 5 percent subrounded andesite stones; neutral (pH 6.6); gradual wavy boundary.

Bw2—31 to 45 inches; brown (10YR 4/3) very gravelly medial sandy loam, yellowish brown (10YR 5/4) dry; weak coarse subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common very fine and fine roots and few medium roots; common very fine tubular pores; 25 percent andesite gravel, 10 percent subrounded andesite cobbles, and 1 percent subrounded andesite stones; moderately acid (pH 5.8); clear smooth boundary.

Bw3—45 to 51 inches; brown (7.5YR 4/4) extremely gravelly medial fine sandy loam, light brown

(7.5YR 6/4) dry; massive; hard, friable, nonsticky and nonplastic; common very fine and fine roots; common very fine tubular pores; 50 percent andesite gravel, 10 percent andesite subrounded cobbles, and 1 percent subrounded andesite stones; moderately acid (pH 5.6); abrupt smooth boundary.

Bqm—51 to 61 inches; brown (10YR 4/3) indurated duripan, yellowish brown (10YR 5/4) dry; 10 percent andesite cobbles and 1 percent andesite stones; many very fine and few fine irregular pores.

Typical Pedon Location

Outside Crater Lake National Park, about 2 miles south of the boundary, in Winema National Forest, Klamath County, Oregon; 574064 meters easting and 4733737 meters northing, UTM Zone 10T, NAD 27

Range in Characteristics

Profile:

Depth to indurated duripan—40 to 60 inches

Depth to bedrock—more than 60 inches

Hue—10YR, 7.5YR, or 5YR

Content of clay—15 to 27 percent

Average content of rock fragments in particle-size

control section—35 to 65 percent

Reaction—slightly acid or neutral

Bulk density—0.90 to 1.00 gram per cubic centimeter

A and AB horizons:

Value—3 or 4 moist, 3 to 5 dry

Chroma—2 to 4 moist, 3 or 4 dry

Texture—gravelly medial loam, gravelly medial sandy loam, very cobbly medial loam, or very cobbly medial sandy loam

index.19

Figure 13.—Typical profile of an Oatman soil. A duripan is at a depth of about 140 centimeters. Measurements on tape are in centimeters.

Many very fine irregular pores; 20 percent andesite gravel, 20 percent subrounded andesite cobbles, and 5 percent subrounded andesite stones; moderately acid (pH 5.8); gradual wavy boundary.

Bw1—12 to 31 inches; dark brown (10YR 3/3) very gravelly medial fine sandy loam, yellowish brown (10YR 5/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine, fine, and medium

Content of rock fragments—20 to 65 percent

Content of gravel—20 to 50 percent

Content of cobbles—0 to 20 percent

Content of stones—0 to 10 percent

B horizon:

Value—3 or 4 moist, 4 to 6 dry

Chroma—3 or 4 moist or dry

Texture—loam or sandy loam

Content of gravel—25 to 50 percent

Content of cobbles—10 to 20 percent

Content of stones—0 to 10 percent

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