LOCATION TOMBSTONE AZ
Established Series
Rev. CLG
10/2013
TOMBSTONE SERIES
The Tombstone series consists of very deep, somewhat excessively drained soils that formed in fan alluvium. Tombstone soils are on fan remnant and stream terraces and have slopes of 1 to 65 percent. The mean annual precipitation is about 14 inches (356 mm) and the mean annual air temperature is about 63 degrees F (17 degrees C).
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Ustic Haplocalcids
TYPICAL PEDON: Tombstone very gravelly fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) Surface rocks - 50 to 65 percent of the surface is covered with gravel and cobble
A--0 to 1 inch (0 to 3 cm); grayish brown (10YR 5/2) very gravelly fine sandy loam, dark grayish brown (10YR 4/2) moist; weak thin platy structure; soft, very friable, nonsticky and nonplastic; few fine roots; few fine tubular pores; 52 percent gravel; strongly effervescent, 13 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); abrupt smooth boundary.
Bk1--1 to 5 inches (3 to 13 cm); dark grayish brown (10YR 4/2) gravelly fine sandy loam, very dark grayish brown (10YR 3/2) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine tubular pores; many distinct calcium carbonate coatings on rock fragments; 21 percent gravel; violently effervescent, 17 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); abrupt smooth boundary.
Bk2--5 to 13 inches (13 to 33 cm); pinkish white (7.5YR 8/2) gravelly sandy loam, pinkish gray (7.5YR 6/2) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common very fine and fine tubular pores; many distinct calcium carbonate coatings on rock fragments; 21 percent gravel; violently effervescent, 22 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear smooth boundary.
Bk3--13 to 27 inches (33 to 69 cm); pinkish gray (7.5YR 7/2) very gravelly sandy loam, pinkish gray (7.5YR 6/2) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; few very fine and fine tubular pores; many distinct calcium carbonate coatings on rock fragments; 47 percent gravel; violently effervescent, 19 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); gradual smooth boundary.
Bk4--27 to 60 inches (69 to 152 cm); pinkish gray (7.5YR 6/2) very gravelly loamy sand, brown (7.5YR 4/2) moist; massive; soft, very friable, nonsticky and nonplastic; few fine roots; common very fine and fine irregular and tubular pores; few prominent calcium carbonate coatings on rock fragments; 38 percent gravel; strongly effervescent, 6 percent calcium carbonate equivalent; moderately alkaline (pH 8.0).
TYPE LOCATION: Cochise County, Arizona; located at a latitude of 31 degrees, 44 minutes, 13 seconds north and a longitude of 109 degrees, 59 minutes, 50 seconds west; about 1,310 feet west and 2,275 feet north of the southeast corner of sec. 33, T. 19 S., R. 23 E.
RANGE IN CHARACTERISTICS:
Soil Moisture: Intermittently moist in some part of the soil moisture control section during July-September and December-February. Driest during May and June. The epipedon is moist in some part less than 90 days (cumulative) when the soil temperature is above 41 degrees F. in 7 out of 10 years. Ustic aridic soil moisture regime.
Soil Temperature: 59 to 70 degrees F (15 to 21.1 degrees C).
Surface rock fragments - 40 to 65 percent of the surface is covered with gravel and cobble
Rock Fragments: Averages 35 to 70 percent in the particle-size control section, but ranges from 15 to 90 percent in any one horizon
Depth to calcic horizon: 1 to 20 inches, weakly cemented in some pedons
Calcium carbonate equivalent: Averages 20 to 35 percent, but ranges from 5 to 40 percent in any one horizon
Reaction: moderately alkaline to strongly alkaline (pH 7.9 to 9.0)
A horizon
Hue: 7.5YR, 10YR
Value: 3 to 7 dry, 2 to 5 moist
Chroma: 2 to 4, dry or moist
Bk horizon
Hue: 7.5YR, 10YR
Value: 3 to 8, dry or moist
Chroma: 2 to 4 dry, 1 to 4 moist
Texture: sandy loam, loam, coarse sandy loam, fine sandy loam (5 to 18 percent clay); can range to include loamy sand and loamy coarse sand below 30 inches.
COMPETING SERIES: These are the
Chilicotal (TX),
Gallen (NM),
Gilland (NM),
Polar (TX), and
Powerline (AZ) series. Chilicotal soils have 15 to 27 percent clay in the control section. Gallen soils have gypsum accumulations. Polar soils are in the Great
Plains. In addition, Gallen and Polar soils are in the Great Plains and are more moist in the soil moisture control section in
May and June. Powerline and Gilland soils have bedrock at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Tombstone soils are in the Sonoran and Chihuahuan deserts on fan remnant and stream terraces and have slopes of 1 to 65 percent. These soils formed in fan alluvium from mixed sources. Elevations range from 3,000 to 5,540 feet (915 to 1689 meters). The mean annual precipitation is 12 to 16 inches (559 to 406 mm). The mean annual air temperature is 57 to 68 degrees F (14 to 20 degrees C). The frost-free period is 160 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Elgin,
Pedregosa and
Stronghold soils. Elgin soils have argillic horizons. Pedregosa soils are very shallow and shallow to a petrocalcic horizon. Stronghold soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; slow runoff; moderately rapid permeability.
USE AND VEGETATION: Tombstone soils are used for livestock grazing and wildlife habitat. Some areas are used for watershed research. The present vegetation is threeawn, black grama, sideoats grama, tarbush, whitethorn, and creosotebush.
DISTRIBUTION AND EXTENT: Central and Southeastern Arizona. This series is moderately extensive. LRR-D, MLRA is 38 and 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pima County, Arizona; Soil survey of Pima County, Arizona, Eastern Part; 1986.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 1 inch (A horizon)
Calcic horizon - the zone from 1 to 60 inches (Bk1, Bk2, Bk3, Bk4 horizons)
The type location was moved from Walnut Gulch to the Douglas-Tombstone Area in April 2000.
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010
Revised for the correlation of AZ661, 2/2009, WWJ
Revised for the correlation of AZ675, 5/2009, WWJ
Revised for the correlation of Graham County, AZ, Southwestern Part; March, 2011, WWJ
Revised for the correlation the SDJR - MLRA 38 - Tombstone-Eloma-Pedregosa complex, 5 to 65 percent slopes project, September 2013, LJG2
National Cooperative Soil Survey
U.S.A.