LOCATION OVERALLFLAT             OR

Established Series
Rev. MPK-JVC-JBF
05/2011

OVERALLFLAT SERIES

The Overallflat series consists of very deep, moderately well drained soils that formed in lacustrine deposits derived from volcanic ash. Overallflat soils are on lakebeds. Slopes are 0 to 2 percent. The mean annual precipitation is about 230 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Ashy, glassy, frigid Aquic Paleargids

TYPICAL PEDON: Overallflat ashy very fine sandy loam--on a nearly level lakebed with slightly hummocky microrelief at an elevation of 1,390 meters--rangeland. (Colors are for dry soil unless otherwise noted. When described on August 18, 2000 the soil was dry from the surface to 66 cm and slightly moist from 66 to 150 cm.)

AE1--0 to 10 cm; light gray (10YR 7/1) ashy very fine sandy loam, dark grayish brown (2.5Y 4/2) moist; weak thick platy structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine and many fine vesicular pores; rapid dilatency; common (4 percent) fine faint brown (10YR 4/3) masses of iron accumulation; slightly alkaline (pH 7.8); clear smooth boundary. (8 or 10 cm thick)

AE2--10 to 18 cm; light gray (10YR 7/1) ashy silt loam, dark grayish brown (2.5Y 4/2) moist; moderate thin platy structure; hard, friable, moderately sticky and slightly plastic; common very fine and common fine roots; many very fine tubular, many very fine irregular roots; rapid dilatency; few (1 percent) fine prominent strong brown (7.5YR 5/6) and few fine faint brown (10YR 4/3) masses of iron accumulation; common (5 percent) fine faint very pale brown (10YR 8/2) silt coats (skeletans) on faces of peds; slightly alkaline (pH 7.8); abrupt smooth boundary. (8 to 13 cm thick)

Bt--18 to 36 cm; brown (10YR 4/3) ashy silty clay loam, olive brown (2.5Y 4/3) moist; strong fine and very fine angular blocky structure; hard, firm, very sticky and very plastic; common very fine and common fine roots; common very fine tubular pores; common very pale brown (10YR 8/2) silt coats (skeletans) on faces of peds; many distinct clay films on faces of peds and lining pores; slightly alkaline (pH 7.8); clear smooth boundary. (10 to 25 cm thick)

Bkq--36 to 66 cm; olive brown (2.5Y 4/3) ashy sandy clay loam, dark olive brown (2.5Y 3/3) moist; moderate medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; few very fine roots; many very fine interstitial and common very fine tubular pores; 25 percent very hard and brittle durinodes that do not slake; secondary carbonates segregated as white (10YR 8/1) filaments on faces of peds; strongly effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (30 to 66 cm thick)

Cq1--66 to 99 cm; light yellowish brown (2.5Y 6/3) ashy fine sandy loam, olive brown (2.5Y 4/3) moist; massive; soft, very friable, slightly sticky and nonplastic; 20 percent of horizon is firm and brittle; few very fine roots; many very fine interstitial and few very fine tubular pores; common fine distinct light brown (7.5YR 6/4) relict masses of iron accumulation in the matrix; moderately alkaline (pH 8.0); gradual smooth boundary. (23 to 46 cm thick)

Cq2--99 to 152 cm; light yellowish brown (2.5Y 6/3) ashy loamy fine sand, olive brown (2.5Y 4/3) moist; massive; soft, very friable, nonsticky and nonplastic; 20 percent of horizon is firm and brittle; common very fine and common fine roots; few very fine tubular pores; common fine distinct light brown (7.5YR 6/4) relict masses of iron accumulation in the matrix; moderately alkaline (pH 8.0).

TYPE LOCATION: Lake County, Oregon; about 2 miles east of the Stauffer Rim in Overall Flat; approximately 100 feet west and 10 feet north of the southeast corner of section 21, T. 24 S., R. 22 E.; USGS Tired Horse Butte 7.5 minute topographic quadrangle; latitude 43 degrees 28 minutes 9.5 seconds N and longitude 120 degrees 04 minutes 34.5 seconds W; ,NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Moist in winter and early spring, dry from late spring through early fall; aridic moisture regime that borders on xeric.
Mean annual soil temperature: 7 to 8 degrees C.
Ochric epipedon thickness: 15 to 23 cm.
Aquic conditions: Occurs seasonally from the soil surface to a maximum depth of about 25 cm.
Depth to base of argillic horizon: 25 to 48 cm.

Particle-size control section - Clay content: 30 to 45 percent.
Volcanic glass content - 30 to 95 percent in coarse silt through fine sand fractions.

AE or E horizons
Hue: 10YR or 2.5Y.
Value: 6 or 7 dry.
Chroma: 1 or 2 dry.
Redoximorphic features: Occur as few or common redox concentrations of iron along with zones of clay or iron depletion (skeletans).
Other features: These horizons are Albic materials and qualify as Albic horizons.

Bt horizon
Hue: 10YR or 2.5Y.
Value: 4 through 6 dry, 4 or 5 moist.
Chroma: 2 or 3 moist.
Texture: Ashy silty clay loam, ashy clay loam, or ashy clay.
Clay content: 30 to 45 percent.
Redoximorphic features: Occur in some pedons as few or common zones of iron or clay depletion (skeletans) which may be superimposed on clay films.

Bkq horizon
Hue: 10YR or 2.5Y.
Value: 4 through 7 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Durinodes: 20 to 35 percent weakly to strongly cemented durinodes.
Reaction: Slightly alkaline or moderately alkaline.
Identifiable secondary carbonates: Occurs as few filaments or coats on faces of peds.
Calcium carbonate equivalent: 1 to 3 percent.

Cq horizons
Hue: 10YR or 2.5Y.
Value: 4 through 6 dry, 3 through 6 moist.
Chroma: 2 or 3, dry or moist.
Texture: Ashy fine sandy loam, ashy loamy fine sand, ashy loamy sand, or very gravelly ashy sand.
Reaction: Slightly alkaline or moderately alkaline.
Redoximorphic features: Occur as few or common relict masses of iron accumulation.
Other features: 10 to 30 percent of matrix is firm and brittle moist and slakes in water.

COMPETING SERIES: There are currently no other series in this family.

GEOGRAPHIC SETTING: Overallflat soils are on lakebeds. These soils formed in lacustrine deposits derived from volcanic ash. Slopes are 0 to 2 percent. Elevations range from 1,345 to 1,424 meters. The climate is semiarid and characterized by cool, moist winters and warm, dry summers. The mean annual precipitation is 200 to 300 mm, the mean annual temperature is 6 to 7 degrees C, and the frost-free period is 50 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Borobey and Silverash soils. Borobey soils are ashy with ashy sandy loam texture, have mollic epipedons, and occur on valley floors. Silverash soils are fine, have smectitic mineralogy, a xeric moisture regime, and occur on small depressions.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained; medium surface runoff; slow permeability; moderately low saturated hydraulic conductivity. These soils are susceptible to occasional ponding for brief duration from January through March with water up to 15 cm deep. Episaturation is present in upper horizons during ponding.

USE AND VEGETATION: Overallflat soils are used for livestock grazing. The vegetation is basin big sagebrush, Thurber's needlegrass, and Sandberg's bluegrass.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive with about 6,900 acres of the series mapped to date. MLRA 23.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Lake County (Northern Part), Oregon, 2006.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon and albic horizon - The zone from the soil surface to 18 cm (AE1 and AE2 horizons).
Aquic conditions - The conditions of episaturation, reduction, and redoximorphic features between the soil surface and 18 cm at certain times during normal years (AE1 and AE2 horizons).
Argillic horizon - The zone from 18 to 36 cm (Bt horizon).
Paleargid great group feature - The abrupt clay increase of more than 15 percent at 18 cm. (between the AE2 and Bt horizons).
Identifiable secondary carbonates and durinodes - The zone from 36 to 66 cm (Bkq horizon).
Particle-size control section and ashy substitute class with glassy mineralogy - The zone from 18 to 36 cm (Bt horizon).

ADDITIONAL DATA: Volcanic glass content determined locally by optical grain counts using a polarizing petrographic microscope.

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National Cooperative Soil Survey
U.S.A.