LOCATION RITOAZUL COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aridic Haplusterts
TYPICAL PEDON: Ritoazul silty clay, on a northeast facing, 4 percent slope in grass at an elevation of 5930 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; grayish brown (2.5Y 5/2) silty clay , dark grayish brown (2.5Y 4/2) moist; weak fine granular and weak fine subangular blocky structure; soft, very friable, sticky and plastic; few very fine roots; 1 percent gravel; 20 percent calcium carbonate equivalent; violently effervescent; slightly alkaline (pH 7.7); clear smooth boundary. (2 to 5 inches thick)
Bss1--3 to 18 inches; grayish brown (10YR 5/2) clay, dark grayish brown (10YR 4/2) moist; moderate fine and medium subangular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; common fine wedge shaped aggregates; few distinct slickensides; 22 percent calcium carbonate equivalent; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary.
Bss2--18 to 29 inches; 80 percent light olive brown (2.5Y 5/3) and 20 percent dark grayish brown (2.5Y 4/2) clay, grayish brown (2.5Y 5/2) moist and crushed; weak medium subangular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots in cracks; common fine wedge shaped aggregates; few distinct slickensides; 5 percent gravel and 2 percent shale parachanners; 18 percent calcium carbonate equivalent; violently effervescent; moderately alkaline (pH 8.1); gradual wavy boundary. (Combined thickness of the Bss horizons is 18 to 27 inches)
BCk--29 to 33 inches; 50 percent light olive brown (2.5Y 5/3) and 50 percent dark grayish brown (2.5Y 4/2) parachannery clay, dark grayish brown (2.5Y 4/2) moist and crushed; massive; extremely hard, very firm, very sticky and very plastic; few very fine roots; common fine rounded masses of calcium carbonate; 15 percent calcium carbonate equivalent; violently effervescent; 15 percent shale parachanners; slightly alkaline (pH 7.6); clear wavy boundary. (0 to 5 inches thick)
BCk/Cr--33 to 36 inches; 30 percent light olive brown (2.5Y 5/3) and 30 percent dark grayish brown (2.5Y 4/2) very parachannery clay loam, dark grayish brown (2.5Y 4/2) moist and crushed; ; few very fine roots in cracks; common fine rounded masses of calcium carbonate; few fine distinct gypsum crystals, violently effervescent (10 percent calcium carbonate equivalent); slightly alkaline (pH 7.6); 40 percent (Cr); moderately cemented shale parachanners; clear wavy boundary. (0 to 3 inches thick)
Cr--36 to 60 inches; gray (2.5Y 5/1) thin platy soft to moderately cemented shale, dark gray (2.5Y 4/1) moist; massive with moderate medium platy and angular rock structure,; extremely hard, extremely firm, very sticky and very plastic; slighltly effervescent (2 percent calcium carbonate equivalent); slightly alkaline (pH 7.6).
TYPE LOCATION: Las Animas County, Colorado; about 3.2 miles east of Trinchera, Colorado; located about 1,900 feet north and 1,050 feet east of the southwest corner of sec. 35, T. 34 S., R. 59 W.; Branson USGS quad; lat. 37 degrees 02 minutes 08 seconds N. and long. 103 degrees 59 minutes 22 seconds W., NAD 1927
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is moist intermittently May through August, dry December through February; Ustic moisture regime bordering on aridic.
Mean annual soil temperature: 48 to 54 degrees F
Mean summer soil temperature: 68 to 73 degrees F
Depth to paralithic contact: 20 to 40 inches to shale
Depth to secondary calcium carbonate: 0 to 3 inches
Gypsum content: ranges from 0 to 30 percent with major concentrations confined to the horizon above and including the paralithic contact. The gypsum is not pedogenic, but inherited from the residuum shale bedrock.
Calcium carbonate equivalent: 1 to 30 percent. CCE generally is high in the surface horizon and decreases with depth primarily due to the alluvial nature of the soil.
Thickness of the cambic horizon: 18 to 27 inches
Vertic features: Cracks extend from the shale bedrock to the surface horizon. Cracks range from 1 to 5 mm in width. Linear extensibility ranges from 4 to 6 cm. Wedge shaped aggregates and slickensides are present.
Particle-size control section (weighted average):
Clay content: 40 to 55 percent; carbonate clay content: 1 to 10 percent.
Sand content: 5 to 25 percent with less than 15 percent fine or coarser sand
Rock fragments: 0 to 10 percent gravel
Pararock fragments: average 10 to 30 percent
A horizon:
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 3 to 5 moist
Chroma: 2 or 3
Clay content: 35 to 50 percent
Rock fragments: 0 to 5 percent
Calcium carbonate equivalent: 15 to 30 percent
EC (mmhos/cm): 0 to 2
SAR: 0 to 2
Bss horizons:
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: silty clay, clay
Clay content: 40 to 55 percent
Pararock fragments: 0 to 5 percent shale fragments
Calcium carbonate equivalent: 15 to 30 percent
EC (mmhos/cm): 0 to 1
SAR: 0 to 1
Reaction: slightly alkaline or moderately alkaline
BCk horizon:
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: silty clay, clay
Clay content: 35 to 50 percent
Pararock fragments: 5 to 50 percent shale fragments
Calcium carbonate equivalent: 2 to 15 percent
EC (mmhos/cm): 1 to 3
Gypsum: 5 to 25 percent
SAR: 0 to 2
Reaction: slightly alkaline or moderately alkaline
BCk/Cr horizon:
Pararock fragments: 35 to 50 percent shale fragments
Calcium carbonate equivalent: 1 to 10 percent
EC (mmhos/cm): 1 to 3
Gypsum: 10 to 25 percent
SAR: 0 to 2
Reaction: slightly alkaline or moderately alkaline
COMPETING SERIES: These are the
Albers(AZ), Domingues(CO),
Sideshow(CO), and
Springerville(AZ) series.
Albers and Sideshow soils: are very deep.
Domingues and Springerville soils: are 40 to 60 inches to paralithic or lithic contact.
GEOGRAPHIC SETTING:
Parent material: alluvium and residuum derived from shale.
Landform: hills, fans, structural benches, and pediments
Slopes: 1 to 9 percent
Elevation: 5,000 to 6,500 feet
Mean annual temperature: 49 to 54 degrees F
Mean annual precipitation: 14 to 18 inches
Precipitation pattern: peak periods of precipitation occur May through August.
Frost-free period: 120 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lanola, Manzanst and Midway series. The Lanola soils are shallow to lithic contact and are on hills and scarps. The Manzanst soils are very deep and are on fans. The Midway soils are shallow to paralithic contact and are on hills.
DRAINAGE AND PERMEABILITY: Well drained, runoff is high on 1 to 5 percent slopes and very high on 5 to 9 percent slopes, very slow permeability.
USE AND VEGETATION: The soil is used as rangeland and wildlife habitat; the potential plant community is blue grama, western wheatgrass, sideoats grama, green needlegrass, fourwing saltbush, and winterfat.
DISTRIBUTION AND EXTENT: northeastern New Mexico and southeastern Colorado; LRR G, MLRA 70 and transitional areas into MLRA 67; the soil is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES PROPOSED: Las Animas County, Colorado, Las Animas County soil survey area, Colorado. The name is from the Rito Azul drainage.
REMARKS: The soil was formerly included in the Litle series. Litle soils have a soil moisture control section that is dry for longer periods of time and occur in an aridic moisture regime. Evaluation of laboratory data and field data supports the classification of Aridic Haplusterts. Calcium carbonate in the solum decreases with depth and is considered primary, not secondary. Gypsum in the BCk/Cr is primary to the shale parent paterial. Smectitic mineralogy based on field observations during September, 2002 Progress Field Review.
Diagnostic horizons and features recognized in this pedon are:
Series control section: 10 to 36 inches.
Particle-size control section: 10 to 36 inches. (lower part of the Bss1 and the Bss2, BCk and BCk/Cr horizons)
Ochric epipedon: 0 to 3 inches. (A horizon)
Cambic horizon: 3 to 29 inches. (Bss1 and Bss2 horizons)
Paralithic contact: Shale bedrock at 36 inches. (Cr horizon)
Vertic features: The presence of wedge shaped aggregates and slikensides from 3 to 29 inches (Bss1, Bss2, and BCk horizons)
Other features: Ustic moisture regime bordering on aridic.
Taxonomic Version: Second Edition, 1999
ADDITIONAL DATA: Laboratory sample S93CO-071-011 sampled as Razor, revised to Ritoazul.