LOCATION TOPOCOBA AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic, shallow Petrocalcic Paleustalfs
TYPICAL PEDON: Topocoba gravelly very fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 1 inch; brown (7.5YR 5/4) gravelly very fine sandy loam, brown (7.5YR 4/4) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine roots; common very fine irregular pores; surface lag layer of 20 percent fine gravel; very slightly effervescent; neutral; abrupt smooth boundary. (1 to 3 inches thick)
Bt--1 to 6 inches; reddish brown (5YR 4/4) gravelly sandy clay loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; common very fine tubular pores; 15 percent gravel and 5 percent cobble; few faint clay films lining pores; slightly effervescent; neutral; abrupt smooth boundary. (4 to 6 inches thick)
Bk1--6 to 12 inches; reddish brown (5YR 4/4) extremely cobbly sandy clay loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; few very fine tubular pores; 30 percent gravel and 30 percent cobble, predominantly hardpan fragments; strongly effervescent; slightly alkaline; abrupt wavy boundary. (3 to 7 inches thick)
Bk2--12 to 17 inches; reddish brown (5YR 5/4) extremely cobbly sandy clay loam, reddish brown (5YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; 60 percent cobble, 10 percent stones, and 10 percent gravel, predominantly hardpan fragments; violently effervescent; moderately alkaline; abrupt wavy boundary. (5 to 6 inches thick)
2Bkm--17 to 22 inches; indurated, calcium carbonate-cemented hardpan.
3R--22 inches; limestone.
TYPE LOCATION: Coconino County, Arizona; on the Havasupai Indian Reservation; in an unsectionized area projected to be 1200 feet south and 1600 feet west of the northeast corner of section 8, T. 32 N., R. 2 W.
RANGE IN CHARACTERISTICS:
Soil Moisture: Moist in some part of the soil moisture control section during December - March and intermittently moist during July - September. Driest during May and June. Aridic ustic soil moisture regime.
Soil Temperature: 54 to 57 degrees F.
Rock fragments: Ranges from 20 to 70 percent, averages 35 to 70 percent in the control section. A gravelly to extremely gravelly surface lag layer is common.
Depth to petrocalcic horizon: 10 to 20 inches
Depth to bedrock: 15 to 40 inches
Calcium carbonate equivalent: Less than 30 percent above the hardpan
Organic matter: Averages more than 1 percent in the surface
A horizon
Hue: 5YR, 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Bt horizon
Hue: 5YR, 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4 moist
Texture: sandy clay loam, loam, clay loam
Bk horizon
Hue: 5YR, 7.5YR
Value: 4 or 5, dry or moist
Chroma: 3 or 4, dry or moist
Texture: sandy clay loam, loam, clay loam
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Topocoba soils are on plateaus and mesas at elevations of 4600 to 6200 feet. They formed in alluvium derived from limestone and sandstone. Slopes range from 2 to 8 percent. The mean annual precipitation is 14 to 18 inches. The mean annual air temperature is 52 to 55 degrees F. The frost-free period is 130 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Natank, Orlie, Toqui, Winona, and Yumtheska soils. Natank soils are moderately deep to bedrock. Orlie soils are very deep. Toqui, Winona, and Yumtheska soils are shallow to bedrock and do not have a petrocalcic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Topocoba soils are used for wildlife habitat, recreation, and limited livestock grazing. Present vegetation is big sagebrush, blue grama, and muttongrass.
DISTRIBUTION AND EXTENT: Northwestern Arizona. This series is of moderate extent. MLRA 35.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Coconino County, Arizona; Soil Survey of Hualapai-Havasupai Area, AZ, Parts of Coconino, Mohave and Yavapai Counties; 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 1 inch (A horizon)
Argillic horizon - The zone from 1 to 6 inches (Bt horizon)
Petrocalcic horizon - The zone from 17 to 22 inches (Bkm horizon)
Lithic contact - The boundary at 22 inches (R horizon)
Classified according to Soil Taxonomy Second Edition, 1999; Keys to Soil Taxonomy Tenth Edition, 2006.
ADDITIONAL DATA: Laboratory analysis by BIA Natural Resources Laboratory in Gallup, New Mexico