The Arbuckle series consists of very deep, well drained soils on low terraces. These soils formed in alluvium derived from conglomerate and metasedimentary rocks. Slope ranges from 1 to 5 percent. The mean annual precipitation is 14 to 21 inches, and the mean annual air temperature is 57 to 63 degrees F.

Taxonomic class: Fine-loamy, mixed, superactive, thermic Typic Haploxeralfs

Arbuckle sandy loam, 1 to 5 percent slopes, under annual grasses and forbs. When described on September 15, 1992, the soil was dry to 34 inches and slightly moist below.

A1—0 to 4 inches; light yellowish brown (10YR 6/4) sandy loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky parting to moderate medium granular structure; slightly hard, very friable, slightly sticky and nonplastic; many very fine roots; many very fine interstitial and few very fine tubular pores; 10 percent gravel; slightly acid (pH 6.2); abrupt smooth boundary.

A2—4 to 10 inches; light yellowish brown (10YR 6/4) sandy loam, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine interstitial and few very fine tubular pores; 10 percent gravel; slightly acid (pH 6.2); clear smooth boundary.

A3—10 to 17 inches; light yellowish brown (10YR 6/4) sandy loam, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine interstitial and few very fine tubular pores; 10 percent gravel; slightly acid (pH 6.1); clear smooth boundary.

Bt1—17 to 26 inches; yellowish brown (10YR 5/4) gravelly sandy loam, dark yellowish brown (10YR 3/4) moist; moderate medium angular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular pores; common thin clay films on ped faces; 25 percent gravel; slightly acid (pH 6.2); clear smooth boundary.

Bt2—26 to 34 inches; yellowish brown (10YR 5/4) gravelly sandy clay loam, dark yellowish brown (10YR 3/4) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular pores; few thin clay films on ped faces; 30 percent gravel; slightly acid (pH 6.3); clear smooth boundary.

Bt3—34 to 44 inches; yellowish brown (10YR 5/4) gravelly loam, dark yellowish brown (10YR 4/4) moist; moderate fine subangular blocky structure; slightly hard, firm, sticky and slightly plastic; few very fine roots; common very fine tubular pores; many thin clay films on ped faces; 30 percent gravel; carbonate pendants on lower side of gravel; slightly acid (pH 6.3); clear smooth boundary.

BC—44 to 68 inches; yellowish brown (10YR 5/4) very gravelly sandy clay loam, dark yellowish brown (10YR 4/4) moist; massive; loose, loose, non sticky and non plastic; many very fine interstitial pores; 50 percent gravel; carbonate pendants on lower side of gravel; slightly acid (pH 6.5).

Type location: Colusa County, California; located about 6 miles west of Arbuckle, California 2100 feet west and 1200 feet north of the southeast corner of section 35, T. 13 N., R. 3 W., MDB&M; 39 degrees, 00 minutes, 55 seconds north latitude and 122 degrees, 09 minutes, 32 seconds west longitude; USGS Cortina Creek, California topographic quadrangle.

The mean annual soil temperature is 60 to 65 degrees F and the soil temperature is above 47 degrees F all year. Soil moisture control section of 8 to 26 inches is dry in all parts from May 15 to October 31 and moist in some or all parts from November 1 to May 15. Organic matter is assumed to be less than 1 percent from data of similar soils on similar geomorphic positions. The solum thickness is more than 40 inches.

The A horizons are 10YR 6/4, 6/3, 5/4; 7.5YR 6/4, 6/3, 5/4 and moist colors of 10YR 4/4, 4/3; 7.5YR 6/4, 5/4, 4/4. Texture is sandy loam or gravelly loam. Coarse fragments range from 3 to 35 percent. Reaction ranges from slightly acid to neutral.

The Bt horizons are 10YR 6/4, 5/4; 7.5YR 6/4, 5/4 and moist colors of 10YR 4/4, 3/4; 7.5YR 4/4, 3/4. Texture is gravelly loam, gravelly sandy loam, gravelly sandy clay loam, gravelly clay loam, sandy clay loam or loam. Coarse fragments range from 3 to 35 percent gravel. Clay content ranges from 18 to 32 percent with less than 20 percent coarse and very coarse sand. Reaction is slightly acid to slightly alkaline and the horizons are not calcareous.

The BC horizon is 10YR 6/4, 6/3, 5/4, 5/3 and moist colors of 10YR 5/4, 5/3, 4/4, 4/3. Texture is stratified gravelly sandy clay loam to very gravelly clay loam. Reaction is slightly acid to slightly alkaline.