Established Series


The Briones series consists of somewhat excessively drained, moderately deep soils over sandstone. Briones soils are on uplands and are strongly sloping to steep. The mean annual precipitation is about 17 inches and the mean annual air temperature is about 59 degrees F.

TAXONOMIC CLASS: Mixed, thermic Typic Xeropsamments

TYPICAL PEDON: Briones loamy sand, annual grass range. (Colors are for dry soil unless otherwise noted.)

A11--0 to 2 inches; grayish brown (10YR 5/2) loamy sand, dark brown (7.5YR 3/2) moist; single grained; loose; many very fine vertical roots; many medium interstitial and many very fine tubular pores; slightly acid (pH 6.5); abrupt smooth boundary. (1 to 3 inches thick)

A12--2 to 13 inches; light brownish gray (10YR 6/2) loamy sand, dark brown (7.5YR 4/2) moist; single grained; loose; common very fine roots; many medium interstitial and few fine tubular pores; strongly acid (pH 5.5); clear smooth boundary. (8 to 11 inches thick)

A13--13 to 23 inches; brown (10YR 5/3) loamy sand, dark brown (7.5YR 4/4) moist; single grained; loose; common very fine roots; few fine tubular pores and many interstitial pores; strongly acid (pH 5.5); abrupt smooth boundary. (8 to 12 inches thick)

C1--23 to 32 inches; dark brown (7.5YR 4/4 dry and moist) heavy loamy sand; common fine faint light brown (7.5YR 6/4) mottles; massive; slightly hard, friable, slightly sticky and nonplastic; few very fine roots; many very fine tubular and common fine interstitial pores; slightly acid (pH 6.5); clear smooth boundary. (3 to 10 inches thick)

C2r--32 to 50 inches; yellowish brown (10YR 5/4) soft coarse grained sandstone; medium acid (pH 6.0).

TYPE LOCATION: Contra Costa County, California; approximately 2.5 miles southwest of town of Brentwood, NE1/4 SW1/4 SE1/4 section 22, T. 1 N., R. 2 E., projected.

RANGE IN CHARACTERISTICS: Depth to a paralithic contact to firm to soft sandstone is 20 to 40 inches. The mean annual soil temperature at a depth of 20 inches is about 61 degrees F. and the soil temperature is above 47 degrees F. at all times. The soil between the depths of 12 and 35 inches or to a paralithic contact, whichever is shallow, is continuously moist in some or all parts from about mid-November until about mid-May. The soil usually is dry all the rest of the time. The soil profile is sand or loamy sand throughout and usually has a little more clay in the lower part.

The A11 horizon is slightly or medium acid and the remainder of the profile is slightly to strongly acid. The A11 horizon is grayish brown or brown and the remainder of the profile is slightly to strongly acid. The A11 horizon is grayish brown or brown and the remainder of the profile is light brownish gray, and gray, pale brown, brown or dark brown.

The C1 horizon lacks mottles in some pedons. The dominant chroma of both th matrix and mottles is more than 2, usually 3 or 4.

COMPETING SERIES: These are Arnold, Calhi, Corralitos, Delhi, and Tujunga series. Arnold soils have a paralithic contact at depths of 40 to 50 inches. Calhi, Corralitos, Delhi, and Tujunga soils lack a paralithic contact.

GEOGRAPHIC SETTING: Briones soils are on hills and uplands at elevations of 500 to 1,000 feet and are underlain by soft to firm coarse grained sandstone. The climate is subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is 14 to 20 inches. Mean January temperature is about 47 degrees F., mean July temperature is about 72 degrees F., and mean annual temperature is about 59 degrees F. The average frost-free season is about 250 to 300 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alo, Lodo, Los Osos, and Millsholm soils. Alo soils are silty clay or clay in all parts. Lodo and Millsholm soils have a lithic contact at depths of less than 20 inches. Los Osos soil have an argillic horizon.

DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium to rapid runoff; rapid permeability of the soil, but slow or very slow permeability in the sandstone.

USE AND VEGETATION: Used for range. Vegetation is grasses, forbs, and scattered oak.

DISTRIBUTION AND EXTENT: Foothills of the Coast Range in central California. The series is inextensive.


SERIES ESTABLISHED: Contra Costa County, California, 1973.

REMARKS: This series is the moderately deep equivalent of the ARnold series.

National Cooperative Soil Survey
U. S. A.