LOCATION FOSSILAKE               OR

Established Series
Rev. CWL-MPK-JVC-JBF
03/2011

FOSSILAKE SERIES

The Fossilake series consists of very deep, somewhat poorly drained soils that formed in eolian material and lacustrine deposits derived from volcanic rocks and volcanic ash. Fossilake soils are on depressions on lakebeds. Slopes are 0 to 1 percent. The mean annual precipitation is about 230 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Ashy, glassy, calcareous, frigid Aquandic Halaquepts

TYPICAL PEDON: Fossilake ashy fine sandy loam--on a nearly level depression at an elevation of 1,310 meters--rangeland. (Colors are for dry soil unless otherwise noted.)

Anz1--0 to 3 cm; light gray (10YR 7/2) ashy fine sandy loam, dark grayish brown (10YR 4/2) moist; weak thin platy structure parting to moderate very fine granular; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine interstitial pores; soluble sodium salts as many fine crystals throughout and as a 2 mm thick white (10YR 8/1) crust on the soil surface; violently effervescent; very strongly alkaline (pH 9.6); abrupt smooth boundary. (0.5 to 5 cm thick)

Anz2--3 to 8 cm; light brownish gray (10YR 6/2) ashy very fine sandy loam, dark grayish brown (10YR 4/2) moist; weak very thick platy structure parting to moderate thick platy; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine interstitial pores; soluble sodium salts as few fine crystals throughout; strongly effervescent; very strongly alkaline (pH 9.6); clear smooth boundary. (10 to 23 cm thick)

Bn1--8 to 18 cm; light gray (10YR 7/1) ashy very fine sandy loam, dark grayish brown (10YR 4/2) moist; weak coarse subangular blocky structure parting to moderate medium subangular blocky; soft, very friable, slightly sticky and slightly plastic; few very fine, few fine and common medium roots; few very fine tubular pores; strongly effervescent; very strongly alkaline (pH 9.6); clear smooth boundary. (10 to 20 cm thick)

Bn2--18 to 38 cm; light gray (10YR 7/2) ashy silt loam, brown (10YR 4/3) and dark grayish brown (10YR 4/2) moist; weak thick platy structure parting to moderate medium subangular blocky; soft, very friable, slightly sticky and moderately plastic; few very fine, common fine, and few medium roots; few very fine tubular pores; strongly effervescent; very strongly alkaline (pH 9.6); clear smooth boundary. (20 to 30 cm thick)

Cn--38 to 79 cm; light gray (10YR 7/1) stratified ashy loam to ashy loamy sand, dark grayish brown (10YR 4/2) moist; massive; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine interstitial pores; stratification of materials is evident; slightly effervescent; very strongly alkaline (pH 9.6); abrupt smooth boundary. (20 to 40 cm thick)

Bknb--79 to 109 cm; pale yellow (2.5Y 7/3) ashy loam, olive brown (2.5Y 4/3) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine and few fine tubular pores; common fine faint brown (7.5YR 4/3) moist masses of iron accumulation and common medium distinct brown (7.5YR 4/4) moist masses of iron accumulation throughout; secondary carbonates segregated as few fine irregular coats on faces of peds; strongly effervescent; strongly alkaline (pH 9.0); clear smooth boundary. (15 to 50 cm thick)

BCb--109 to 127 cm; pale yellow (2.5Y 7/3) ashy loam, olive brown (2.5Y 4/3) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine and few fine tubular pores; common fine faint brown (7.5YR 4/3) moist masses of iron accumulation and common medium distinct brown (7.5YR 4/4) moist masses of iron accumulation throughout; strongly effervescent; strongly alkaline (pH 9.0); abrupt smooth boundary. (13 to 25 cm thick)

BCgb--127 to 168 cm; white (5Y 8/1) ashy silt loam, pale olive (5Y 6/4) moist; weak coarse subangular blocky structure parting to moderate fine angular blocky; soft, very friable, slightly sticky and slightly plastic; few very fine and few fine roots; few very fine and few fine tubular pores; common medium prominent brown (7.5YR 4/4) moist masses of iron accumulation and few medium prominent greenish gray (5G 6/1) moist zones of iron depletion; strongly effervescent; strongly alkaline (pH 8.8).

TYPE LOCATION: Lake County, Oregon; about 17 miles northeast of the village of Christmas Valley and east of Sucker Flat; approximately 1,500 feet south and 2,800 feet east of the northwest corner of section 3, T. 26 S., R. 19 E.; USGS Fossil Lake 7.5 minute topographic quadrangle; latitude 43 degrees 21 minutes 06 seconds N and longitude 120 degrees 26 minutes 55 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in the moisture control section during winter, spring, and early summer, dry late summer and fall; xeric soil moisture regime.
Mean annual soil temperature: 7 to 8 degrees C.
Depth to base of cambic horizon: 30 to 56 cm.
Depth to aquic conditions: 76 to 127 cm.
Depth to buried horizons: 76 to 100 cm.

Particle-size control section - Clay content: Averages 8 to 18 percent.
Volcanic glass content - 30 to 95 percent in coarse silt through fine sand fractions.

Anz horizons
Value: 6 or 7 dry, 4 or 5 moist.
Calcium carbonate equivalent: 2 to 6 percent
Salinity (EC): 16 to 30 mmhos/cm.
Sodicity (SAR): 30 to 100.
Effervescence: Strongly effervescent or violently effervescent.
Organic matter content: 0.1 to 0.5 percent

Bn horizons
Value: 4 or 5 moist.
Chroma: 1 or 2 dry, 2 or 3 moist.
Texture: Ashy very fine sandy loam, ashy silt loam, or ashy sandy clay loam.
Clay content: 10 to 26 percent.
Calcium carbonate equivalent: 2 to 4 percent
Salinity (EC): 16 to 30 mmhos/cm.
Sodicity (SAR): 30 to 100.
Effervescence: Strongly effervescent or violently effervescent.

Cn horizon
Texture: Stratified ashy loamy sand to ashy loam.
Clay content: 8 to 24 percent.
Calcium carbonate equivalent: 1 to 3 percent
Salinity (EC): 8 to 16 mmhos/cm.
Sodicity (SAR): 13 to 60.
Effervescence: Slightly effervescent or strongly effervescent.

Bknb horizon
Hue: 10YR or 2.5Y.
Value: 4 or 5 moist.
Texture: Ashy loam or ashy clay loam.
Clay content: 24 to 35 percent.
Redoximorphic features: Redox concentrations occur as masses of iron accumulation.
Salinity (EC): 8 to 16 mmhos/cm.
Sodicity (SAR): 13 to 30.
Identifiable secondary carbonates: Occurs as few fine or medium coats on faces of peds.
Calcium carbonate equivalent: 2 to 10 percent.

BCb and BCgb horizons
Hue: 2.5Y or 5Y.
Texture: Ashy loam or ashy silt loam.
Clay content: 18 to 27 percent.
Redoximorphic features: Redox concentrations occur as masses of iron accumulation, redox depletions occur in some horizons as zones of iron depletion or as a reduced matrix.
Calcium carbonate equivalent: 2 to 4 percent
Salinity (EC): 4 to 8 mmhos/cm.
Sodicity (SAR): 5 to 13.

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

GEOGRAPHIC SETTING: Fossilake soils are on depressions on lakebeds. These soils formed in eolian material and lacustrine deposits derived from volcanic rocks and volcanic ash. Slopes are 0 to 1 percent. Elevations range from 1,306 to 1,326 meters. The climate is semiarid and characterized by cold, moist winters and warm, dry summers. The mean annual precipitation is 200 to 250 mm, the mean annual temperature is 6 to 7 degrees C, and the frost-free period is 50 to 80 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Salhouse and Thornlake soils. Salhouse soils have ashy sandy textures in the particle-size control section, do not have endosaturation within 150 cm of the soil surface, and are on stable dunes. Thornlake soils are ashy, have cambic horizons, do not have endosaturation within 150 cm of the soil surface, and occur on lake terraces.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat poorly drained; negligible surface runoff; moderate to moderately slow permeability; moderately high saturated hydraulic conductivity. Endosaturation is present with an apparent seasonal high water table within 76 cm of the soil surface (moderately deep free water occurrence class) from April through June. Cumulative annual duration class is Transitory. The water table drops after June, but remains within about 122 cm of the soil surface year-round. These soils are susceptible to frequent ponding for long duration from February through June with water less than 15 cm deep.

USE AND VEGETATION: Fossilake soils are used for livestock grazing and wildlife habitat. The potential vegetation is mainly inland saltgrass, Carex sp., and Rush sp.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive with about 1,100 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 - The zone from the soil surface to 18 cm (Anz1, Anz2, and Bn1 horizons).
Cambic horizon - The zone from 5 to 38 cm (Bn1 and Bn2 horizons).
Buried cambic horizon - The zone from 79 to 168 cm (Bknb, BCb, and BCgb horizons).
Aquic conditions - The conditions of endosaturation, reduction, and redoximorphic features between 76 and 150 cm at certain times during normal years (parts of the Bknb, BCb, and BCgb horizons).
Particle-size control section and ashy substitute class with glassy mineralogy - The zone from 25 to 100 cm (Cn horizon and parts of the Bn2 and Bknb horizons).

Note: This series is the first Aquandic Halaquept recognized in the U.S.A. The 2nd edition of Soil Taxonomy (NRCS,1999) mentions that this subgroup is not known to occur in the United States.

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

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National Cooperative Soil Survey
U.S.A.