LOCATION BRIDGEWELL              OR

Established Series
Rev. MPK-JVC-JBF
12/2010

BRIDGEWELL SERIES

The Bridgewell series consists of very deep, poorly drained soils that formed in lacustrine deposits derived from volcanic ash. Bridgewell 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, calcareous, frigid Aquandic Endoaquolls

TYPICAL PEDON: Bridgewell ashy loam--on a one percent slope at an elevation of 1,310 meters--rangeland. (When described on October 15, 1998 the soil was very moist to wet with an apparent water table at 90 cm. Colors are for moist soil unless otherwise noted.)

A1--0 to 8 cm; very dark gray (10YR 3/1) ashy loam, grayish brown (10YR 5/2) dry; weak thin platy structure; hard, friable, moderately sticky and slightly plastic; many very fine, common fine, and common medium roots; many very fine and fine interstitial pores; moderately alkaline (pH 8.4); clear smooth boundary.

A2--8 to 15 cm; very dark gray (10YR 3/1) ashy clay loam, grayish brown (10YR 5/2) dry; weak fine and very fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine, many fine, and many medium roots; common very fine and fine interstitial and tubular pores; slightly effervescent; moderately alkaline (pH 8.4); clear smooth boundary.

A3--15 to 36 cm; very dark gray (10YR 3/1) ashy mucky loam, gray (10YR 5/1) dry; weak medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine, fine and medium roots; common very fine and fine tubular pores; slightly effervescent; many visible pumiceous ash grains; moderately alkaline (pH 8.4); gradual smooth boundary. (Combined thickness of the A horizons is 30 to 50 cm)

AC--36 to 58 cm; very dark gray (10YR 3/1) ashy clay loam, gray (10YR 6/1) dry; weak medium platy structure; hard, friable, moderately sticky and moderately plastic; common very fine, common fine, and common medium roots; many very fine and common fine tubular pores; slightly effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (0 to 25 cm thick)

C--58 to 91 cm; brown (10YR 5/3) ashy silt loam, light gray (10YR 7/2) dry; strong very fine angular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, common fine, and common medium roots; many very fine and common fine tubular pores; slightly effervescent; common visible pumiceous ash grains; few fine prominent light gray (5Y 7/1) and light gray (N 7/0) zones of iron depletion near pores; moderately alkaline (pH 8.4); clear smooth boundary. (15 to 33 cm thick)

Ck1--91 to 127 cm; brown (10YR 5/3) ashy silty clay loam, very pale brown (10YR 8/2) dry; massive; hard, firm, moderately sticky and moderately plastic; common very fine, common fine, and common medium roots; common very fine and few fine tubular pores; few fine prominent light gray (5Y 7/1) and light gray (N 7/0) zones of iron depletion near pores; slightly effervescent in matrix and strongly effervescent in secondary masses; strongly effervescent, moderately alkaline (pH 8.4); clear smooth boundary. (20 to 40 cm thick)

Ck2--127 to 152 cm; brown (10YR 5/3) ashy loam, very pale brown (10YR 8/2) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine, common fine, and common medium roots; common very fine and few fine tubular pores; light gray (5Y 7/1) and light gray (N 7/0) zones of iron depletion near pores; slightly effervescent in matrix and strongly effervescent in secondary masses; moderately alkaline (pH 8.4).

TYPE LOCATION: Lake County, Oregon; in Silver Lake; approximately 800 feet north and 2,600 feet west of the southeast corner of section 32, T. 28 S., R. 16 E.; USGS Egli Rim 7.5 minute topographic quadrangle; latitude 43 degrees 5 minutes 43.3 seconds N and longitude 121 degrees 50 minutes 55.1 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Wet in winter and spring; moist to wet in summer and fall; aquic moisture regime.
Mean annual soil temperature: 7 to 8 degrees C.
Mollic epipedon thickness: 30 to 50 cm.
Depth to aquic conditions: 0 to 25 cm.
Depth to redoximorphic features: 50 to 64 cm.
Other features: It is assumed that enough active ferrous iron occurs in the A and AC horizons, when aquic conditions are present, to give positive reactions to alpha,alpha-dipyridyl.

Particle-size control section - Clay content: 18 to 35 percent.
Volcanic glass content: 75 to about 100 percent in coarse silt through fine sand fractions.

A1 horizon
Hue: 10YR or 2.5Y.
Value: 4 or 5 dry.
Chroma: 1 or 2, moist or dry
Organic matter content: 4 to 8 percent.

A2 and A3 horizons
Hue: 10YR or 2.5Y.
Value: 4 or 5 dry.
Chroma: 1 or 2, moist or dry.
Texture: Ashy loam, ashy clay loam, or ashy mucky loam.
Clay content: 18 to 35 percent.
Organic matter content: 4 to 12 percent.
Effervescence: Very slightly effervescent or slightly effervescent.
Calcium carbonate equivalent: 1 to 3 percent.

C and Ck horizons
Hue: 10YR or 2.5Y.
Value: 4 or 5 moist, 6 through 8 dry.
Chroma: 2 through 4, moist or dry.
Texture: Ashy loam, ashy silt loam, or ashy silty clay loam.
Clay content: 18 to 35 percent.
Effervescence: Slightly effervescent or strongly effervescent.
Calcium carbonate equivalent: 1 to 3 percent.
Other features: Uncoated medium sand through very coarse sand-sized pumiceous ash grains are present in at least one subhorizon.

COMPETING SERIES: These are the Cummings and Hussa series.
Cummings soils do not have horizons with visible pumiceous ash grains and have horizons with secondary gypsum. Hussa soils do not have horizons with visible pumiceous ash grains.

GEOGRAPHIC SETTING: Bridgewell soils are on lakebeds. These soils formed in lacustrine deposits derived from volcanic ash. Slopes are 0 to 2 percent. Elevations range from 1,310 to 1,620 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: This is the Picturerock soil. Picturerock soils lack aquic conditions within 25 cm of the soil surface, have cambic horizons, and are located on lake terraces.

DRAINAGE AND PERMEABILITY: Poorly drained; negligible surface runoff; moderately slow permeability; moderately high saturated hydraulic conductivity. Endosaturation is present with an apparent seasonal high water table between the soil surface and 75 cm (very shallow to moderately deep free water occurrence classes) from December to July. Cumulative annual duration class is Persistent. These soils are susceptible to occasional ponding for very long duration from December through July with water up to 90 cm deep.

USE AND VEGETATION: Bridgewell soils are used for livestock grazing and wildlife habitat. The present vegetation is mainly bulrush and meadow foxtail.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive with about 7,300 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. The name is coined.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 36 cm (A1, A2, and A3 horizons).
Vitrandic intergrade feature - The zone from the soil surface to 76 cm (A1, A2, A3, and AC horizons and part of the C horizon).
Aquic conditions - The conditions of endosaturation, reduction, and redoximorphic features between the soil surface 150 cm at certain times during normal years (parts of the A1, A2, A3, AC, C, and Ck1 horizons).
Identifiable secondary carbonates - The zone from 91 to 152 cm (Ck1 and Ck2 horizons).
Particle-size control section and ashy substitute class with glassy mineralogy - The zone from 25 to 100 cm (AC and C horizons and parts of the A3 and Ck1 horizons).

ADDITIONAL DATA: Volcanic glass in the A3 and C horizons determined locally by optical grain count using a polarizing petrographic microscope.

---

National Cooperative Soil Survey
U.S.A.