LOCATION DIPSEA CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, isomesic Mollic Hapludalfs
TYPICAL PEDON: Dipsea very gravelly loam, on a southwest facing slope of 60 degrees under redwoods, tanoak, huckleberry, swordfern, and some annual grasses at 600 feet elevation. (Colors are for dry soil unless otherwise stated. When described (8/27/76) the soil was moist throughout).
O1 & 02--9 inches to 0; leaves and duff.
A11--0 to 4 inches; dark brown (7.5YR 3/2) very gravelly loam, dark reddish brown (5YR 5/2) moist; strong very fine and fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial pores; 35 percent gravel; slightly acid (pH 6.5); clear smooth boundary. (2 to 6 inches thick)
A12--4 to 8 inches; dark brown (7.5YR 4/4) very gravelly loam, dark reddish brown (5YR 3/2) moist; strong very fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine and fine interstitial, vesicular and tubular pores; 35 percent pebbles; moderately acid (pH 6.0); clear smooth boundary. (4 to 6 inches thick)
B21t--8 to 12 inches; brown (7.5YR 5/4) very gravelly heavy loam, dark reddish brown (5YR 3/3) moist; moderate fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine, fine, medium and coarse roots; many very fine and fine interstitial vesicular and tubular pores; few thin clay films on peds and in pores; 45 percent pebbles; moderately acid (pH 6.0); gradual wavy boundary. (4 to 6 inches thick)
B22t--12 to 25 inches; brown (7.5YR 5/4) very gravelly clay loam, reddish brown (5YR 4/4) moist; moderate fine and medium subangular blocky structure; hard, firm, sticky and plastic; many very fine, fine, medium and coarse roots; many very fine and fine interstitial, vesicular and tubular pores; few thin clay films on peds and in pores; 50 percent pebbles; strongly acid (pH 5.5); gradual wavy boundary. (12 to 14 inches thick)
B3--25 to 48 inches; light brown (7.5YR 6/4) very gravelly loam, reddish brown (5YR 4/4) moist; moderate fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, fine and medium roots; many very fine and fine interstitial vesicular and tubular pores; 55 percent pebbles; strongly acid (pH 5.5); clear irregular boundary. (22 to 28 inches thick)
Cr--48 to 55 inches; fractured sandstone.
TYPE LOCATION: Marin County, California; San Geronimo area, 1.2 miles NW of peak of Pine Mountain, 2 miles SE of the spillway of Peter's Dam on Kent Lake.
RANGE IN CHARACTERISTICS: Depth to a paralithic or lithic contact is 40 to 60 inches. The mean annual soil temperature is 50 degrees to 56 degrees F. and the soil temperature is usually not below 47 degrees F. The difference between mean winter and mean summer temperature is 5 degrees to 8 degrees F. The soil moisture control section is moist in all parts for about 290 to 300 days. Reaction is slightly acid to strongly acid with acidity increasing with increasing depth. Base saturation is less than 50 percent in some part of the A horizon but ranges from 35 to 60 percent (ammonium acetate). In the lower part of the B horizon the base saturation ranges from 55 to 70 percent but is more than 60 percent at the paralithic contact. Rock fragments are present in all horizons and average 15 to 80 percent. The control section is 25 to 70 percent.
The A horizon is 7.5YR 3/2, 4/2, 4/4, 5/2, 5/4; 5YR 4/3, 4/4, 5/3, 5/4 or 10YR 5/3 and moist color of 5YR 2/2, 3/2, 3/3, 3/4; 7.5YR 3/2, 4/2 or 4/4. It is gravelly loam, or very gravelly loam and has 15 to 55 percent rock fragments.
The B2t horizon has dry color of 5YR 4/3, 4/4, 4/6, 5/3, 5/4, 5/6, 5/8, 6/4, 6/6, 6/8, 7/6, 7/8; 7.5YR 5/2, 5/4 or 6/4 and moist color of 5YR 3/2, 3/3, 3/4, 4/3, 4/4; 7.5YR 4/2 or 4/4. It is very gravelly heavy loam, very gravelly sandy clay loam, or very gravelly clay loam.
Some pedons have a C horizon above the paralithic contact.
COMPETING SERIES: This is the Centissima series in another family. Centissima soils lack an argillic horizon and have a fine-loamy particle-size control section.
GEOGRAPHIC SETTING: Dipsea soils are on hills and mountain slopes. Slopes are from 15 to 75 percent. The soils formed in material weathered from sandstone and shale. Elevations are from 10 to 1,700 feet. The climate is subhumid mesothermal with cool foggy summers and cool moist winters. The mean annual precipitation is 40 to 70 inches. The average January temperature is about 49 degrees F.; average July temperature is about 57 degrees F. The mean annual temperature is about 54 degrees F. The frost-free season is 290 to 365 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Barnabe and Centissima soils. Barnabe soils are less than 20 inches deep to a paralithic contact. Centissima soils have a fine-loamy particle-size control section and a cambic horizon.
DRAINAGE AND PERMEABILITY: Well drained; rapid to very rapid runoff; moderate permeability.
USE AND VEGETATION: Used for Woodland, wildlife habitat, and watershed. Native vegetation is Douglas-fir, madrone, huckleberry, redwood, ferns, clover, moss, dogwood and tanoak.
DISTRIBUTION AND EXTENT: Central and northern coastal California. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Marin County, California, 1979.
REMARKS: The activity class was added to the classification in January of 2003. Competing series were not checked at that time. - ET