LOCATION TOLFORK OR

Established Series
Rev. MHF/CDJ/RWL
06/2011

TOLFORK SERIES

The Tolfork series consists of deep, well drained soils formed in colluvium and residuum from metasedimentary or metavolcanic rock types. Tolfork soils are on north-facing side slopes of mountains. Slopes are 30 to 90 percent. The mean annual precipitation is about 140 inches and the mean annual temperature is about 43 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Pachic Humudepts

TYPICAL PEDON: Tolfork very gravelly coarse sandy loam - woodland, on a 55 percent north-facing slope at 3,920 feet elevation. (When described on October 3, 1989 the soil was moist throughout. Colors are for moist soil unless otherwise noted.)

Oi--0 to 2 inches; slightly decomposed needles, leaves, twigs, and woody materials.

A--2 to 11 inches; very dark brown (10YR 2/2) very gravelly coarse sandy loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; many very fine and fine, and few medium roots; common very fine tubular pores; 45 percent gravel and 10 percent cobbles; strongly acid (pH 5.2); clear wavy boundary. (6 to 10 inches thick)

Bw1--11 to 25 inches; very dark grayish brown (10YR 3/2) extremely gravelly sandy loam, grayish brown (10YR 5/2) dry; moderate medium subangular blocky structure parting to weak fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine, and few medium and coarse roots; many very fine tubular pores; 50 percent gravel and 15 percent cobbles; strongly acid (pH 5.2); clear wavy boundary.

Bw2--25 to 32 inches; very dark grayish brown (10YR 3/2) extremely gravelly sandy loam, grayish brown (10YR 5/2) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, and few medium roots; many very fine tubular pores; 40 percent gravel and 20 percent cobbles; strongly acid (pH 5.2); clear wavy boundary. (Combined thickness of the Bw horizon is 18 to 26 inches)

C1--32 to 38 inches; dark grayish brown (2.5Y 4/2) extremely gravelly sandy loam, light brownish gray (2.5Y 6/2) dry; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine, and few medium roots; many fine and medium tubular pores; 45 percent gravel and 20 cobbles; strongly acid (pH 5.2); clear wavy boundary.

C2--38 to 52 inches; dark grayish brown (2.5Y 4/2) extremely cobbly sandy loam, light brownish gray (2.5Y 6/2) dry; massive; soft, very friable, nonsticky and nonplastic; common fine, and few medium roots; many fine tubular pores; 35 percent gravel and 40 percent cobbles; strongly acid (pH 5.2); abrupt wavy boundary. (Combined thickness of the C horizon is 14 to 24 inches)

R--52 inches; fractured sandstone.

TYPE LOCATION: Curry County, Oregon; located about 990 feet south and 330 feet east of the northwest corner of section 34, T. 36 S., R. 12 W., W. M. (Latitude 42 degrees, 25 minutes, 20 seconds N.; Longitude 124 degrees, 06 minutes, 26 seconds W.)

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 41 to 46 degrees F. The soils are usually moist but are dry for less than 45 consecutive days between depths of 4 and 12 inches in the four months following the summer solstice. The particle-size control section averages 10 to 20 percent clay, more than 30 percent coarser than fine sand, and has 50 to 70 percent rock fragments. Depth to bedrock is 40 to 60 inches. The umbric epipedon is 20 to 30 inches thick and may include all or part of the Bw horizon. The solum is 25 to 35 inches thick. Soil reaction strongly acid throughout. Hue is 10YR or 7.5YR throughout the solum.

The A horizon has value of 2 or 3 moist, 3 or 4 dry and chroma of 2 or 3 moist and dry. It is very gravelly coarse sandy loam averaging 10 to 20 percent clay. It has 30 to 45 percent gravel and 5 to 15 percent cobbles.

The Bw horizon has value of 2 to 4 moist, 4 or 5 dry and chroma of 2 or 3 moist and dry. It is very gravelly loam, extremely gravelly loam, or extremely gravelly sandy loam averaging 10 to 20 percent clay. It has 40 to 50 percent gravel and 10 to 25 percent cobbles.

The C horizon has value of 4 to 6 moist, 5 to 7 dry and chroma of 2 or 3 moist and dry. It is very gravelly sandy loam, extremely gravelly sandy loam, or extremely cobbly sandy loam averaging 10 to 15 percent clay. It has 30 to 50 percent gravel and 20 to 40 percent cobbles.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: The Tolfork soils are on metastable to active north-facing side slopes of mountains. Slopes are 30 to 90 percent. The soils formed in colluvium and residuum derived from metasedimentary or metavolcanic rock types of the Dothan Formation. Elevations are 3,800 to 5,500 feet. The climate is characterized by cool wet winters and warm moist summers. The mean annual precipitation is 120 to 160 inches. The mean annual temperature is 40 to 45 degrees F. The frost-free period is 60 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gamelake and Tincup soils. Gamelake soils are on broad ridgetops and south-facing side slopes of mountains, are greater than 60 inches deep to bedrock, and have umbric epipedons 10 to 20 inches thick. Tincup soils are on broad ridgetops and side slopes of mountains and are 20 to 40 inches deep to bedrock.

DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.

USE AND VEGETATION: The soils are used for timber production, watershed, recreation, and wildlife habitat. The native vegetation is Douglas-fir, white fir, Shasta red fir, cascade Oregongrape, broadleaf starflower, big huckleberry, creeping snowberry, baldhip rose, western rattlesnake plantain, deerfoot vanillaleaf, evergreen violet, white insideout flower, Oregon fairybells, American trailplant, and western princes pine.

DISTRIBUTION AND EXTENT: Mountainous areas of southwestern Oregon; MLRA 1. The series is not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Curry County, Oregon, 1995.

REMARKS: Diagnostic horizons and features recognized in this pedon include:

Umbric epipedon - from 2 to 32 inches (A, Bw1, Bw2 horizons).

Pachic subgroup based on umbric epipedon greater than 20 inches thick.

Particle-size control section - from 12 to 42 inches (part of the Bwl, the Bw2, C1, and part of the C2 horizons) with a weighted average of 63 percent rock fragments.

ADDITIONAL DATA: Partial laboratory data available for pedon 90P 316, sample 90P1912 and pedon 90P300, sample 90P1859M from Curry County, Oregon sampled by NSSL at Lincoln, Nebraska - 3/90.

National Cooperative Soil Survey
U.S.A.