LOCATION MCELMO NMEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Natrigypsids
TYPICAL PEDON: McElmo very gravelly sandy clay loam -- on a slightly convex dipslope of a cuesta sloping 7 percent to the east at 5,460 feet elevation -- rangeland. (Colors are for dry soil unless otherwise noted. When described, the soil was moist from 2 through 7 inches and dry below.)
A--0 to 1 inch; light reddish brown (5YR 6/4) very gravelly sandy clay loam. reddish brown (5YR 4/4) moist; moderate very thick platy structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine vesicular pores; 45 percent angular pebbles and 10 percent angular cobbles; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (1 or 2 inches thick)
2Btn/E--1 to 4 inches; yellowish red (5YR 5/6) gravelly clay, yellowish red (5YR 4/6) moist; strong medium prismatic structure parting to strong fine angular blocky; upper one-half inch is pink (5YR 7/3), light reddish brown (5YR 6/4) moist (E part); hard, friable, very sticky and very plastic; few fine and common very fine roots; many fine vesicular pores in upper one-half inch; many very fine irregular pores; common thin clay films on faces of peds and lining pores; upper 1 inch of prisms have some uncoated sand grains (E part); 20 percent angular pebbles; strongly effervescent, secondary calcium carbonate segregated in very few fine irregularly shaped accumulations on faces of peds; strongly alkaline (pH 8.8); clear smooth boundary. (3 or 4 inches thick)
2Btkn--4 to 14 inches; light reddish brown (5YR 6/4) clay, yellowish red (5YR 4/6) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, very firm, very sticky and very plastic; few medium and common fine and very fine roots; few very fine tubular pores; common moderately thick clay films on faces of peds and lining pores; 10 percent angular pebbles; strongly effervescent, secondary calcium carbonate segregated in few fine and medium irregularly shaped accumulations on faces of peds; strongly alkaline (pH 9.0); clear irregular boundary. (6 to 23 inches thick)
3Bky1--14 to 30 inches; pink (5YR 7/3) cobbly gypsiferous silty clay loam, light reddish brown (5YR 6/4) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; few medium and very fine roots; common very fine tubular pores; 10 percent angular pebbles and 15 percent angular cobbles; secondary fine sand sized gypsum crystals in few fine irregularly shaped accumulations as soft masses; violently effervescent, secondary calcium carbonate segregated in common medium and large irregularly shaped accumulation as soft masses and on rock fragments; strongly alkaline (pH 8.6); clear wavy boundary. (6 to 16 inches thick)
3Bky2--30 to 41 inches; pink (5YR 7/3) gypsiferous silty clay loam, light reddish brown (5YR 6/4) moist; weak coarse subangular blocky structure; slightly hard, friable, sticky and plastic; few fine and very fine roots; common very fine tubular pores; 30 percent soft shale fragments and 5 percent angular pebbles; secondary fine sand sized gypsum crystals in common fine and medium irregularly shaped accumulations on faces of peds and on rock fragments; strongly effervescent, secondary calcium carbonate segregated in few medium irregularly shaped accumulations on rock fragments; moderately alkaline (pH 8.0); clear irregular boundary. (7 to 16 inches thick)
3Cy--41 to 54 inches; pink (5YR 7/3) gypsiferous silty clay loam, light reddish brown (5YR 6/4) moist; massive, platy rock structure; slightly hard, friable, sticky and plastic; few very fine roots; few very fine irregular pores; 60 percent soft shale fragments; secondary fine sand sized gypsum crystals in few fine irregularly shaped accumulations on rock fragments; slightly effervescent, secondary calcium carbonate segregated in very few fine irregularly shaped accumulations on rock fragments; slightly alkaline (pH 7.8); clear irregular boundary. (12 to 25 inches thick)
2Cr--54 inches; fractured bentonitic shale bedrock with very few roots and few accumulations of secondary gypsum in fractures.
TYPE LOCATION: San Juan County, New Mexico; on the Navajo Indian Reservation about 16 miles southwest of Shiprock; 2,500 feet north and 1,000 feet east of the southwest corner of section 9, T.29N., R.20W.; Latitude 36 degrees 44 minutes 27 seconds North, and Longitude 108 degrees 58 minutes 2 seconds West.
RANGE IN CHARACTERISTICS:
Soil moisture - Typically, the soil moisture control section (SMCS) is intermittently moist in some part from July to October and December to March. The SMCS is assumed to be dry in all parts 50 to 75 percent of the time (cumulative), when the soil temperature at 20 inches is 41 degrees F or higher. Typic aridic moisture regime.
Soil temperature - 52 to 54 degrees F.
Soil depth - 40 to 60 inches to soft bedrock
Silicate clay content, control section weighted average - 40 to 60 percent
Depth to base of natric horizon - 10 to 25 inches
Depth to calcic horizon - 5 to 25 inches
Depth to gypsic horizon - 25 to 40 inches
Organic carbon content - less than 0.29 percent
Reaction - ranges from slightly alkaline in the surface to strongly alkaline in the subsoil
A horizon - Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 through 6
Salinity, mmhos/cm: 0 to 2
Sodicity, SAR: 0 to 5
Rock fragments: Total range is 35 to 60 percent
35 to 50 percent pebbles
0 to 10 percent cobbles
2Btn/E horizon - Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 4 through 6
Texture: gravelly clay or clay
Clay content: 40 to 60 percent
Salinity, mmhos/cm: 2 to 4
Sodicity, SAR: 13 to 30
Rock fragments: 0 to 20 percent pebbles
2Btkn horizon - Hue: 5YR or 7.5YR
Value: 5 through 7 dry, 4 or 5 moist
Chroma: 4 through 6
Texture: clay or silty clay
Clay content: 40 to 60 percent
Salinity, mmhos/cm: 2 to 4
Sodicity, SAR: 13 to 30
Calcium carbonate equivalence, <2mm: 10 to 25 percent
Rock fragments: 0 to 10 percent pebbles
3Bky1 horizon - Hue: 5YR through 5Y
Value: 6 or 7 dry, 5 through 7 moist
Chroma: 1 through 4
Texture: gypsiferous silty clay, gypsiferous clay loam or cobbly gypsiferous silty clay loam
Clay content: 35 to 50 percent
Salinity, mmhos/cm: 8 to 16
Sodicity, SAR: 5 to 13
Calcium carbonate equivalent, <2mm: 15 to 25 percent
Rock fragments: Total range is 0 to 25 percent
0 to 10 percent pebbles
0 to 15 percent cobbles
Gypsum content: 2 to 5 percent as small secondary crystals
Other features: 0 to 15 percent soft shale fragments
3Bky2 horizon - Hue: 5YR through 5GY
Value: 7 or 8 dry, 5 through 7 moist
Chroma: 1 through 4
Texture: gypsiferous silty clay loam or gypsiferous silty clay
Clay content: 35 to 50 percent
Salinity, mmhos/cm: 8 to 16
Sodicity, SAR: 5 to 13
Calcium carbonate equivalent, <2mm: 5 to 10 percent
Rock fragments: 0 to 10 percent pebbles
Gypsum content: 10 to 30 percent as small secondary crystals
Other features: 10 to 30 percent soft shale fragments
3Cy horizon - Hue: 5YR through 5GY
Value: 5 through 8 dry, 4 through 7 moist
Chroma: 1 through 4
Texture: gypsiferous silty clay or gypsiferous silty clay loam
Clay content: 35 to 50 percent
Salinity, mmhos/cm: 8 to 16
Sodicity, SAR: 5 to 13
Gypsum content: 10 to 20 percent as small secondary crystals
Other features: 50 to 75 percent soft shale fragments
COMPETING SERIES: There no competitors.
GEOGRAPHIC SETTING: McElmo soils are on dipslopes of cuestas. They formed in alluvium and residuum derived from Jurassic bentonitic shale and sandstone. Slopes range from 5 to 15 percent. Elevation ranges from 5,300 to 6,300 feet. The mean annual precipitation is 8 to 12 inches with 35 to 60 percent falling as rain from high intensity thunderstorms between July and October. The mean annual temperature is 50 to 52 degrees F. The average frost-free period is 130 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beclabito, Bodot and Farview soils. Beclabito soils are fine-loamy and lack gypsic horizons. Bodot soils are moderately deep to a paralithic contact and are undeveloped. Farview soils are very shallow to a lithic contact and are undeveloped.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; slow permeability
USE AND VEGETATION: McElmo soils are used for livestock grazing. Present vegetation is galleta, alkali sacaton, sand dropseed, shadscale, cheatgrass, mound saltbush, and desert seepweed with widely scattered Utah juniper.
DISTRIBUTION AND EXTENT: McElmo soils are of small extent on the Blanding Basin portion of the Colorado Plateau province in northwest New Mexico and northeast Arizona. MLRA 35.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Shiprock Area, Parts of San Juan County, New Mexico and Apache County, Arizona; 1993.
REMARKS: The series type location was moved to the Shiprock Soil Survey Area in Western San Juan County, New Mexico in 1988; this area better represents the taxonomic classification.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to a depth of about 1 inch. (A horizon)
Natric horizon - The zone from 1 to about 14 inches. (2Btn/E and 2Btkn horizons)
Calcic horizon - The zone from 14 to about 30 inches.
(3Bky1 horizon)
Gypsic horizon - The zone from 30 to about 54 inches.
(3Bky2 and 3CY horizons)
Paralithic contact - The presence of soft shale bedrock
at about 54 inches.
Keys to Soil Taxonomy - Soils classified according to the Eighth Edition, 1998.
ADDITIONAL DATA: Percent gypsum and SAR values are estimated. Salinity values were determined on three pedons with an Instant EC salinity kit. Calcium carbonate equivalence was determined with a field volume calcimeter.
-Annual Pattern of Soil-Water States- -----------------------------------------------------------
Depth Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
(in)
0-1 f f d d d d d m d d m f
1-4 f w m m d d d m m m m m
4-14 f m m m d d d d m m m m
14-30 d d m d d d d d d d d d
30-41 d d d d d d d d d d d d
41-54 d d d d d d d d d d d d ------------------------------------------------------------
f: frozen more than half of the month
w: wet more than half of the month
m: moist more than half of the month
d: dry more than half of the month
Information gathered from: Estimates and field notes