LOCATION ARCHROCK COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, micaceous Typic Humicryepts
TYPICAL PEDON: Archrock gravelly loam, on a east facing, convex, 23 percent slope in tundra at an elevation of 11,800 feet. (Colors are for dry soil unless otherwise noted.) When described on August 8, 1997, the soil was moist throughout.
The surface is covered by 20 percent cobbles.
A--0 to 8 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots and common medium roots; 25 percent gravel; very strongly acid (pH 4.8). (7 to 10 inches thick)
Bw--8 to 18 inches; brownish yellow (10YR 6/6) very gravelly loam, dark yellowish brown (10YR 4/6) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few very fine, fine and medium roots; 50 percent gravel; strongly acid (pH 5.3). (8 to 20 inches thick)
2BC--18 to 25 inches; light yellowish brown (10YR 6/4) very gravelly coarse sandy loam, yellowish brown (10YR 5/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; 40 percent gravel and 15 percent cobbles; very strongly acid (pH 4.8). (5 to 10 inches thick)
2Cr--25 to 35 inches; soft schist. (5 to 10 inches thick)
TYPE LOCATION: Larimer County, Colorado; about 0.7 miles southeast of Milner Pass in Rocky Mountain National Park; Fall River USGS quad; lat. 40 degrees 24 minutes 54 seconds N. and long. 105 degrees 48 minutes 2 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Soil moisture regime: udic
Mean annual soil temperature: 33 to 37 degrees F.
Mean summer soil temperature: 43 to 47 degrees F.
Surface rock fragments: 35 to 75 percent, dominantly fine gravel
Depth to paralithic contact: 20 to 40 inches to granite, gneiss and schist
Thickness of the umbric epipedon: 7 to 20 inches
Particle-size control section (weighted average):
Clay content: 8 to 18 percent
Sand content: 45 to 70 percent
Rock fragments: 35 to 50 percent
Mica content: 40 to 70 percent (by grain count)
A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 1 to 3
Clay content: 10 to 18 percent
Rock fragments: 15 to 35 percent, dominantly gravel
Base saturation: 10 to 40 percent
Reaction: Very strongly acid or strongly acid
Bw horizon:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 4 to 6
Clay content: 10 to 18 percent
Texture: very gravelly loam, very gravelly sandy loam
Rock fragments: 35 to 60 percent, dominantly gravel
Base saturation: 10 to 50 percent
Reaction: very strongly acid to moderately acid
2BC horizon: (a 2C in some pedons)
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 to 6
Clay content: 5 to 18 percent
Texture: very gravelly coarse sandy loam, very gravelly sandy loam
Rock fragments: 35 to 60 percent, dominantly gravel
Reaction: very strongly acid to moderately acid
COMPETING SERIES: These are the
Mummy series.
Mummy soils are greater than 60 inches deep.
Other series that may be competitors if reclassified to paramicaceous mineralogy are the
Afley,
Buell,
Causewa,
Drakespeak,
Hossick,
McCall,
Moran, and
Sibelia series. Afley and Causewa soils have lithic contact at depths of 20 to 40 inches.
The Buell, Drakespeak, McCall, and Moran soils are greater than 60 inches deep.
Hossick soils have hue of 5YR or redder.
Sibelia soils have a lithic contact at depths of 40 to 60 inches.
GEOGRAPHIC SETTING:
Parent material: slope alluvium over residuum derived from granitic rocks, gneiss and schist.
Landform: Mountain
Landform position: backslopes, summits and shoulders.
Slopes: 10 to 40 percent
Elevation: 10,500 to 13,000 feet
Mean annual air temperature: 34 to 38 degrees F.
Mean annual precipitation: 30 to 40 inches.
Wettest months: March and April.
Driest months: September and October.
Frost-free period: 10 to 30 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hiamovi, Leighcan, Mummy, and Trailridge series. The Hiamovi and Trailridge soils are less than 20 inches to paralithic contact and are on summits. Leighcan and Mummy soils are greater than 60 inches deep and are on backslopes.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained, high to very high runoff, moderately rapid permeability.
USE AND VEGETATION: These soils are used for recreation and wildlife habitat. Native vegetation is alpine avens, alpine bluegrass, rock sedge, arctic sagebrush, Parry's clover, tufted hairgrass, alpine clover and alpine willow.
DISTRIBUTION AND EXTENT: Mountain tundra in northcentral Colorado,. LRR E, MLRA 48A. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Larimer County, Colorado, 1999; Rocky Mountain National Park soil survey area. The name is taken from a geographical feature.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Umbric epipedon: The zone from 0 to 8 inches. (A horizon)
Cambic horizon: The zone from 8 to 18 inches. (Bw horizon)
Particle-size control section: The zone from 10 to 25 inches (part of the Bw and the 2BC horizon)
Paralithic contact: At 25 inches. (Cr)
Keys to Soil Taxonomy: Series classified according to Eighth Edition, 1998.
ADDITIONAL DATA:
The mineralogy class was changed from paramicaceous to micaceous in 07/2010 by the National Soil Survey Center on request of the responsible MLRA regional office. The change was necessary based on the eleventh edition of the Keys to Soil Taxonomy, 2010.