LOCATION LIBBY AZEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Petronodic Ustic Paleargids
TYPICAL PEDON: Libby very gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 1 inch; yellowish red (5YR 5/6) very gravelly sandy loam, dark red (2.5YR 3/6) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine and fine irregular pores; 40 percent gravel; noneffervescent; slightly alkaline (pH 7.6); abrupt smooth boundary. (1 to 5 inches thick)
Bt--1 to 13 inches; dark red (2.5YR 3/6) clay, dark reddish brown (2.5YR 3/4) moist; strong fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; common fine roots; few fine tubular pores; many distinct clay films on ped faces and in pores; common fine iron-manganese coatings on ped faces; noneffervescent; slightly alkaline (pH 7.4); clear smooth boundary. (5 to 12 inches thick)
2Btyc1--13 to 25 inches; red (2.5YR 4/6) and red (2.5YR 5/6) gravelly clay, dark reddish brown (2.5YR 3/4) and red (2.5YR 4/6) moist; moderate medium subangular blocky structure; slightly hard, firm, moderately sticky and moderately plastic; few fine roots; few fine tubular pores; many distinct clay films on ped faces, in pores and on rock fragments; few fine iron-manganese coatings on ped faces; 18 percent petronodes; few gypsum crystals; 10 percent gravel; strongly effervescent, 33 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); abrupt wavy boundary.
2Btyc2--25 to 60 inches; red (2.5YR 4/6) very gravelly clay loam, dark red (2.5YR 3/6) moist; moderate fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few fine roots; few fine tubular pores; common distinct clay films on rock fragments; 55 percent petronodes; few gypsum crystals; violently effervescent, 37 percent calcium carbonate equivalent; moderately alkaline (pH 8.2). (Combined thickness of the 2Btyc horizons is 30 to 47 inches)
TYPE LOCATION: Fort Huachuca, Arizona; located at a latitude of 31 degrees, 36 minutes, 32 seconds North and longitude of 110 degrees, 13 minutes, 54 seconds West.
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. Ustic aridic soil moisture regime.
Soil Temperature: 62 to 69 degrees F.
Petronodic feature: 18 to 55 percent petronodes. Thought to have formed from calcium and magnesium that precipitated out during fluctuating seasonal water tables under a climate much wetter than the present. Repeated wetting and extreme drying of the soil may have been a factor in nodule development. The petronodes have no internal organization and break down completely in HCL acid but not in water.
Rock fragments: less than 35 percent gravel and/or petronodes, but can range to 55 percent in any one horizon
Reaction: slightly or moderately alkaline
Clay content: greater 35 percent
Calcium carbonate equivalent: 5 to 40 percent
Depth to abrupt textural change: 1 to 15 inches
A horizon
Hue: 2.5YR, 5YR
Value: 3 through 5, dry or moist
Chroma: 4 or 6, dry or moist
Bt horizon
Hue: 2.5YR, 5YR
Value: 3 through 5, dry or moist
Chroma: 4 or 6, dry or moist
Texture: clay, sandy clay
Effervescence: noneffervescent or slightly
2Btyc horizon
Hue: 2.5YR, 5YR
Value: 3 through 5, dry or moist
Chroma: 4 or 6, dry or moist
Texture: clay, clay loam
Effervescence: strong or violent
Gypsum: 0 to 2 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Libby soils are on stream terraces, fan terraces, and relict basin floors at elevations of 3,900 to 4,600 feet. Slopes are 0 to 10 percent. These soils formed in alluvium from mixed sources. The mean annual precipitation is 12 to 16 inches and occurs as thunderstorms during July to September and as gentle rains during December to February. The mean annual air temperature is 60 to 67 degrees F. The frost-free period is 180 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gulch, Major, Courtland, Diaspar, Caralampi and Tombstone series. Gulch, Major and Courtland soils are fine-loamy. Diaspar soils are coarse-loamy. Caralampi and Tombstone soils are loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; slow permeability.
USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation includes mesquite, black grama, sideoats grama, tobosa, cane beardgrass, plains bristlegrass, Texas zinnia, tarbush and whitethorn.
DISTRIBUTION AND EXTENT: Southern Arizona. Libby soils are of moderate extent. MLRA is 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona; Soil survey of Cochise County, AZ, 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)
Argillic horizon - The zone from 1 to 60 inches (Bt, 2Btyc1, 2Btyc2 horizons)
Pale feature - The abrupt textural change at 1 inch
Soil Taxonomy Second Edition, 1999