LOCATION BAKOPI UT

Tentative Series
Rev. KWC
03/2022

BAKOPI SERIES

The Bakopi series consists of deep and very deep, well drained soils that formed in colluvium derived from basalt. Bakopi soils are on escarpments or lava flows. Slopes range from 30 to 65 percent. Mean annual precipitation is about 305mm (12 inches) and the mean annual temperature is about 13.3 degrees C (56 degrees F).

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Ustic Haplocalcids

TYPICAL PEDON: Bakopi loam - rangeland (Colors are for dry soil unless otherwise noted.)

A--0 to 3 inches (0 to 8 cm); brown (7.5YR 5/4) very gravelly loam, dark reddish brown (5YR 3/3), moist; 23 percent clay; moderate thin platy structure; slightly hard, friable, slightly sticky, moderately plastic; common very fine roots and common fine roots; few carbonate coats on bottom surfaces of rock fragments; carbonate, finely disseminated; 30 percent gravel and 15 percent cobble and 2 percent stone; slightly effervescent; slightly alkaline, pH 7.8; clear smooth boundary.

Bk1--3 to 21.5 inches (8 to 55 cm); yellowish red (5YR 4/6) very cobbly loam, dark reddish brown (5YR 3/4), moist; 26 percent clay; moderate fine subangular blocky structure; slightly hard, firm, moderately sticky, moderately plastic; common very fine roots and common fine roots; common prominent carbonate coats on bottom surfaces of rock fragments; carbonate, finely disseminated and common very fine threadlike carbonate masses; 30 percent gravel and 15 percent cobble and 5 percent stone; strongly effervescent; slightly alkaline, pH 7.8; gradual smooth boundary.

Bk2--21.5 to 43.5 inches (55 to 110 cm); brown (7.5YR 5/4) very cobbly silt loam, strong brown (7.5YR 4/6), moist; 24 percent clay; weak fine subangular blocky structure; slightly hard, firm, moderately sticky, moderately plastic; common very fine roots; common prominent carbonate coats on bottom surfaces of rock fragments; carbonate, finely disseminated and common very fine threadlike carbonate masses; 30 percent gravel and 15 percent cobble and 5 percent stone; violently effervescent; moderately alkaline, pH 8.2.

TYPE LOCATION: Washington County, Utah; about 2.6km (1.6 miles) north of Coal Pits Wash trailhead, near the confluence of Coal Pits and Scoggins Wash. lat. 37 degrees 11 minutes 35.68 seconds N. and long. -113 degrees 04 minutes 44.11 seconds W., 4118334 northing 315484 easting WGS84.

RANGE IN CHARACTERISTICS:

Soil moisture: ustic aridic moisture regime.

A horizon
Hue: 5YR, 7.5YR
Value: 3 to 5, moist or dry
Chroma: 3 or 4, moist or dry
Texture: loam, silt loam
Clay content: 18 to 25 percent
Calcium carbonate equivalent: 0 to 10 percent
Electrical conductivity: 0 to 2 mmhos/cm
Rock fragments: 30 to 60 percent

Bk1 or Btk horizon
Hue: 5YR, 7.5YR
Value: 3 to 5, moist or dry
Chroma: 3 to 5, moist or dry
Texture: loam, silt loam, clay loam
Clay content: 21 to 28 percent
Calcium carbonate equivalent: 15 to 35 percent
Electrical conductivity: 0 to 2 mmhos/cm
Rock fragments: 35 to 65 percent
Reaction: slightly to moderately alkaline (7.4 to 8.4)

Bk2 horizon
Hue: 5YR, 7.5YR
Value: 3 to 5, moist or dry
Chroma: 4 to 6, moist or dry
Texture: loam, silt loam, clay loam
Clay content: 19 to 26 percent
Calcium carbonate equivalent: 15 to 35 percent
Electrical conductivity: 0 to 2 mmhos/cm
Rock fragments: 35 to 65 percent
Reaction: moderately to strongly alkaline (7.9 to 9.0)

COMPETING SERIES: These are the Ildefonso(NM), Placitas(NM), Raydawn(NM), Seis(NM), Strych(UT) series. The Ildefonso, Raydawn, and Strych series have less than 18 percent clay in the PSCS. Placitas and Seis series are moderately deep.

GEOGRAPHIC SETTING: Bakopi soils are mapped on backslopes and noseslopes of escarpments of lava flows.
Parent material: colluvium derived from basalt
Landform: escarpments of lava flows
Slopes: 30 to 65 percent
Elevation: 1225 to 1300 meters
Mean annual temperature: 11.1 to 13.9 degrees C
Mean annual precipitation: 254 to 330 millimeters
Precipitation pattern: May and June are the driest, January to March are the wettest, and monsoonal storms in late summer.
Frost-free period: 175 to 220 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Flaco, Musofare, Windwhistle, and Sedillo series. The Flaco and Musofare soils and are on lava flow plateaus and mesa summits and shoulders. The Windwhistle and Sedillo soils are on footslopes and toeslopes of escaprments.

DRAINAGE AND PERMEABILITY: well drained, medium runoff, moderate permeability.

USE AND VEGETATION: Bakopi soil are used for wildlife habitat. Vegetation includes Mormon tea, Four-wing saltbush, Broom snakeweed, Desert needle and thread grass, Galleta grass, Cheatgrass, Desert Globemallow, Red stem filaree.

DISTRIBUTION AND EXTENT: Washington County, Utah; LRR D, MLRA 35; limited extent in southern Utah.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Phoenix, Arizona

SERIES PROPOSED: Washington County, Utah, Zion National Park, soil survey area UT690.

Remarks: Bakopi soils are mapped on backslopes and noseslopes of escarpments of lava flows. Escarpments are formed by the downcutting through lava flows and the Moenkopi formation hence the name basalt colluvium over Moenkopi residuum.

The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Twelfth Edition

National Cooperative Soil Survey
U.S.A.