LOCATION EPITAPH AZEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Petrocalcic Calcitorrerts
TYPICAL PEDON: Epitaph very cobbly clay loam - rangeland. (Colors are for dry soil unless otherwise noted.) 40 to 50 percent of the surface is covered with gravel and cobble.
A--0 to 1 inch; dark brown (7.5YR 3/2) very cobbly clay loam, very dark brown (7.5YR 2/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and moderately plastic; few fine roots; few very fine tubular pores; common vertical cracks .25 to 1 inch wide; 15 percent gravel and 30 percent cobble; noneffervescent; slightly alkaline (pH 7.6); abrupt smooth boundary. (1 to 3 inches thick)
Bt--1 to 6 inches; dark reddish brown (5YR 3/2) clay, dark reddish brown (5YR 2.5/2) moist; weak medium wedge shaped peds parting to strong medium angular blocky structure; very hard, firm, very sticky and very plastic; common very fine and fine roots and few medium roots; few very fine tubular pores; common vertical cracks .25 to 1 inch wide; common distinct clay films on ped faces and lining pores; noneffervescent; slightly alkaline (pH 7.6); clear smooth boundary. (4 to 10 inches thick)
Btss--6 to 27 inches; dark reddish brown (5YR 3/2) clay, dark reddish brown (5YR 2.5/2) moist; weak medium wedge shaped peds parting to strong medium angular blocky structure; very hard, firm, very sticky and very plastic; common very fine and fine roots; few very fine tubular pores; common distinct clay films on ped faces and lining pores; few intersecting slickensides; slightly effervescent; moderately alkaline (pH 8.0); abrupt wavy boundary. (10 to 30 inches thick)
2Bkm--27 to 38 inches; indurated hardpan; extremely hard, cemented by calcium carbonate; violently effervescent; abrupt wavy boundary. (5 to 15 inches thick)
3R--38 inches; basalt.
TYPE LOCATION: Walnut Gulch Experimental Watershed, Cochise County, Arizona; located at a latitude of 31 degrees, 54 minutes, 35 seconds North and longitude of 110 degrees, 42 minutes, 16 seconds West; 510 feet north and 990 feet east of the southwest corner of section 9, T. 20 S., R. 23 E.
RANGE IN CHARACTERISTICS:
Soil moisture: Intermittently moist in the soil moisture control section during July-September and December-February. Driest during May and June. Ustic aridic soil moisture regime.
Soil temperature: 65 to 69 degrees F.
Surface rock fragments: 40 to 50 percent gravel and cobble
Reaction: slightly to moderately alkaline
Depth to petrocalcic horizon: 20 to 40 inches
Depth to bedrock: 25 to 40 inches
Clay content: more than 35 percent
Organic matter: 1 to 2 percent
Soil cracks: common vertical cracks .25 to 1.5 inches wide
A horizon
Hue: 5YR, 7.5YR
Value: 2.5 or 3, dry or moist
Chroma: 2 or 3, dry or moist
Texture: clay loam, silt loam, loam, silty clay loam
B horizon
Hue: 2.5YR, 5YR
Value: 2.5 or 3 dry, 2.5 through 4 moist
Chroma: 2 or 3 dry, 2.5 through 4 moist
Texture: clay, clay loam, silty clay
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Epitaph soils are on hills and volcanic flows at elevations of 3,800 to 4,900 feet. Slopes range from 0 to 15 percent. The soils formed in slope alluvium and residuum from basalt, cinders, bombs and volcanic rock. The mean annual precipitation ranges from 12 to 16 inches. The mean annual air temperature ranges from 60 to 67 degrees F. The frost-free period is 180 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lampshire and Graham soils. These soils are shallow or very shallow to bedrock.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; very slow permeability.
USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation consists of sideoats grama, plains lovegrass, blue and black grama, curlymesquite, cane beardgrass, and shrubby buckwheat.
DISTRIBUTION AND EXTENT: Southern Arizona. The soils are of limited extent. MLRA is 41. Name derived from the historical Tombstone Epitaph newspaper.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona; Soil survey of Cochise County, Arizona, Douglas-Tombstone Part; 1996.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 1 inch (A horizon)
Vertisol feature - The presence of intersecting slickensides from 6 to 27 inches (Bss horizon)
Petrocalcic horizon - The zone from 27 to 38 inches (2Bkm horizon)
Lithic content - The boundary at 38 inches (3R horizon)
Soil Taxonomy Second Edition, 1999