LOCATION OAGAMATI COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Natrigypsids
TYPICAL PEDON: Oagamati silty clay loam, on a north facing, 3 percent slope in rangeland at an elevation of 4,940 feet. (Colors are for dry soil unless otherwise noted.) The surface is covered by 1 percent gravel
A--0 to 1 inches; light yellowish brown (10YR 6/4) silty clay loam, yellowish brown (10YR 5/4) moist; moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots throughout; 14 percent calcium carbonate equivalent; 1 percent gravel; violently effervescent; moderately alkaline (pH 8.2); abrupt wavy boundary.
BA--1 to 5 inches; yellowish brown (10YR 5/6) clay, yellowish brown (10YR 5/6) moist; moderate thick platy structure parting to weak very fine granular; moderately hard, firm, very sticky and very plastic; common very fine and few fine roots throughout; common very fine dendritic tubular pores; few faint pressure faces on faces of peds; 16 percent calcium carbonate equivalent; EC 6 mmhos/cm; violently effervescent; strongly alkaline (pH 8.6); clear wavy boundary.
Btn--5 to 13 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; hard, very firm, very sticky and very plastic; common very fine and few fine roots throughout; common very fine dendritic tubular pores; few distinct clay films on faces of peds; common very fine irregular gypsum crystals; 12 percent calcium carbonate equivalent; 2 percent gypsum; EC 6 mmhos/cm; violently effervescent; strongly alkaline (pH 8.6); gradual wavy boundary.
Btny--13 to 23 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; hard, very firm, very sticky and very plastic; few very fine roots throughout; few very fine dendritic tubular pores; few distinct clay films on faces of peds; common very fine irregular gypsum crystals; 16 percent calcium carbonate equivalent; 8 percent gypsum; EC 12 mmhos/cm; strongly effervescent; strongly alkaline (pH 9.0); gradual wavy boundary.
C--23 to 35 inches; light olive brown (2.5Y 5/4) very parachannery clay, light olive brown (2.5Y 5/4) moist; weak fine subangular blocky structure; soft, very friable, very sticky and very plastic; few very fine roots throughout; few very fine dendritic tubular pores; common very fine gypsum crystals in the form of horizontal bands; 15 percent calcium carbonate equivalent; 2 percent gypsum; EC 14 mmhos/cm; 50 percent parachanners; strongly effervescent; strongly alkaline (pH 8.8); gradual wavy boundary.
Cr--35 to 62 inches; soft Mancos Shale with bands and seams of gypsum and salts more soluble than gypsum.
TYPE LOCATION: Montezuma County, Colorado; about 15 miles southwest of Towaoc, Colorado; Sentinel Peak Southwest, Colorado USGS quad; lat. 37 degrees 06 minutes 10 seconds N. and long. 108 degrees 59 minutes 18 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture regime: Typic aridic
Mean annual soil temperature: 54 to 58 degrees F
Depth to paralithic contact: 20 to 40 inches to soft Mancos Shale
Depth to gypsic horizon: 10 to 20 inches
Depth to natric horizon: 5 to 10 inches
Depth to salt accumulations: 5 to more than 60 inches
Vertic features: 1/2 to 3/4 inch wide cracks from surface to a depth of 1 foot, 1 to 3 feet apart
Particle-size control section (weighted average):
Clay content: 50 to 60 percent
Rock fragments: 0 to 5 percent
A horizon: (Thickness 1-6 inches)
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: silty clay loam
Clay content: 27 to 35 percent
Rock fragments: 0 to 5 percent gravel-sized limestone, sandstone, and gypsum fragments
Calcium carbonate equivalent: 5 to 15 percent
EC (mmhos/cm): 2 to 4
Gypsum: 1 to 3 percent
Reaction: moderately alkaline
Btn horizon: (Thickness 4 - 12 inches)
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay
Clay content: 40 to 55 percent
Pararock fragments: 0 to 15 percent shale chips
Calcium carbonate equivalent: 5 to 15 percent
EC (mmhos/cm): 8 to 16
Gypsum: 1 to 3 percent
SAR: 13 to 40
Reaction: strongly alkaline
Btny horizon: (Thickness 6 - 16 inches)
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay
Clay content: 40 to 60 percent
Pararock fragments: 0 to 15 percent shale chips
Calcium carbonate equivalent: 10 to 20 percent
EC (mmhos/cm): 8 to 16
Gypsum: 5 to 10 percent
SAR: 13 to 40
Reaction: strongly alkaline
C horizon: (Thickness 6 - 16 inches)
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay
Clay content: 40 to 50 percent
Pararock fragments: 35 to 50 percent shale chips
Calcium carbonate equivalent: 10 to 20 percent
EC (mmhos/cm): 8 to 16
Gypsum: 2 to 5 percent
SAR: 13 to 40
COMPETING SERIES: This is the Tohona (UT) series. Tohona soils have horizons redder than 10YR.
GEOGRAPHIC SETTING:
Parent material: residuum derived from Mancos Shale
Landform: pediments
Slopes: 1 to 6 percent
Elevation: 4,800 to 5,700 feet
Mean annual temperature: 52 to 56 degrees F
Mean annual precipitation: 7 to 10 inches
Precipitation pattern: uniform with slight dip in May and June and slight increase in July and August
Frost-free period: 135 to 160 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Uzona, Gypsey, and Chipeta series. Uzona soils are very deep, Chipeta soils are shallow to shale, and Gypsey soils are not sodic; all are on hills.
DRAINAGE AND PERMEABILITY: Well drained, high or very high runoff, slow permeability.
USE AND VEGETATION: The Oagamati soils are used for rangeland. Native vegetation is mat saltbush and sparse Indian ricegrass, bud sagebrush, and bottlebrush squirreltail.
DISTRIBUTION AND EXTENT: Montezuma County, Colorado, Ute Mountain Indian Reservation. MLRA 35. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona.
SERIES ESTABLISHED: Montezuma County, Colorado, Ute Mountain Area, Colorado and New Mexico, 2005.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 45 inches.
Particle-size control section: The zone from 5 to 25 inches. (Btn and Btny horizons)
Ochric epipedon: The zone from 0 to 5 inches. (A and BA horizons)
Gypsic horizon: The zone from 13 to 23 inches. (Btny horizon)
Natric horizon: The zone from 5 to 23 inches. (Btn and Btny horizons)
Paralithic contact: The contact with Mancos Shale at 35 inches. (Cr horizon)
Vertic features: The presence of cracks to the surface at 0 to 12 inches. (A, BA, and Btn horizons)
ADDITIONAL DATA: Calcium carbonate equivalence was determined using a field calcimeter. Gypsum content and SAR were determined using a HACH kit. EC was measured using a portable EC meter.
Classified according to Keys to Soil Taxonomy Ninth Edition, 2003