LOCATION TOIMI MNEstablished Series
TAXONOMIC CLASS: Coarse-loamy, isotic, frigid Oxyaquic Eutrudepts
TYPICAL PEDON: Toimi stony loam on a slightly convex back slope of a drumlin with a slope of 5 percent at an elevation of about 487 meters. The site is vegetated with red pine. (Colors are for moist soil unless otherwise stated.)
A--0 to 10 cm; dark brown (7.5YR 3/2) stony loam, brown (7.5YR 4/2) dry; moderate fine and medium granular structure; friable; many very fine, fine and medium roots; about 8 percent gravel, 6 percent cobbles and 6 percent stones; strongly acid; clear smooth boundary. (5 to 15 cm thick)
Bw1--10 to 23 cm; dark brown (7.5YR 4/3 and 7.5YR 3/4) stony fine sandy loam; weak fine subangular blocky structure; friable; many very fine and fine roots and common medium roots; about 7 percent gravel, 6 percent cobbles and 6 percent stones; strongly acid; clear wavy boundary.
Bw2--23 to 38 cm; brown (7.5YR 4/4) cobbly sandy loam; weak fine subangular blocky structure; friable; many very fine and fine roots and few medium roots; about 7 percent gravel, 6 percent cobbles and 5 percent stones; moderately acid; gradual wavy boundary.
Bw3--38 to 61 cm; strong brown (7.5YR 5/6) cobbly sandy loam; moderate, medium subangular blocky structure; friable; many very fine and fine roots and few medium roots; few fine distinct strong brown (7.5YR 5/8) Fe concentrations; about 7 percent gravel, 6 percent cobbles and 3 percent stones; slightly acid; gradual wavy boundary.
Bw4--61 to 89 cm; dark brown (7.5YR 4/4 and 7.5YR 4/3) cobbly sandy loam, strong brown (7.5YR 5/6) crushed; moderate medium subangular blocky structure parting to moderate thick platy; friable; few fine roots in fractures; common fine distinct strong brown (7.5YR 5/8) and common medium distinct strong brown (7.5YR 4/6) Fe concentrations and common medium prominent brown (10YR 5/3) Fe depletions; about 7 percent gravel, 6 percent cobbles and 3 percent stones; slightly acid; clear wavy boundary. (Combined thickness of Bw is 36 to 91 cm)
2BCd1--89 to 130 cm; dark grayish brown (10YR 4/2), 65 percent gravelly sandy loam and 35 percent gravelly loamy sand; moderate very coarse and extremely coarse prismatic structure parting to moderate fine and medium platy, few 2 to 3 millimeter oblique fractures 15 cm to 1 meter apart; very firm; common fine distinct yellowish brown (10YR 5/6) and common fine prominent yellowish red (5YR 5/6) Fe concentrations in horizontal orientation; about 25 percent gravel, 5 percent cobbles and 1 percent stones; slightly acid; gradual wavy boundary.
2BCd2--130 to 178 cm; 70% dark grayish brown (10YR 4/2) gravelly sandy loam and 30% grayish brown (10YR 5/2) gravelly loamy sand; moderate very coarse and extremely coarse prismatic structure parting to moderate fine and medium platy, few 2 to 3 millimeter oblique fractures 15 cm to 1 meter apart; very firm; about 25 percent gravel, 5 percent cobbles and 1 percent stones; slightly acid; clear wavy boundary.
2BCd3--178 to 203 cm; dark grayish brown (10YR 4/2) gravelly sandy loam; moderate very coarse and extremely coarse prismatic structure parting to moderate fine and medium platy, few 2 to 3 millimeter oblique fractures 15 cm to 1 meter apart; ; very firm; 25 percent gravel, 5 percent cobbles and 1 percent stones; slightly acid.
TYPE LOCATION: St. Louis County, Minnesota; about 30 miles north of Duluth; 800 feet north and 1000 feet east of the southwest corner of section 17, T. 55 N., R. 13 W.; USGS Boulder Lake Reservoir NE Quadrangle, latitude 47 degrees 14 minutes 38 seconds N. and longitude 92 degrees 1 minute 22 seconds W., NAD 27.
RANGE IN CHARACTERISTICS: The thickness of the loamy mantle ranges from 51 to 102 cm. The depth to free carbonates is greater than 80 cm. Stony surface phases are recognized. Rock fragment content averages less than 35 percent, by volume, in the particle size control section.
Some pedons have a thin O horizon (duff layer).
The A horizon has hue of 7.5YR or 10YR, value of 2 or 3 and chroma of 1 to 3. It is stony loam, stony fine sandy loam, stony sandy loam, or their non-stony, gravelly or cobbly analogues. Rock fragment content by volume ranges from 2 to 30 percent with 2 to 15 percent gravel, 0 to 20 percent cobbles and 0 to 10 percent stones and boulders. It is strongly acid to slightly acid.
Some pedons have a thin E horizon up to 8 cm thick but this occurs in less than 50 percent of all pedons.
The Bw horizon has hue of 7.5YR or 10YR, value of 3 to 5 and chroma of 3 to 6. It is sandy loam, fine sandy loam, loam or their stony, cobbly or gravelly analogues. Rock fragment content by volume ranges from 2 to 30 percent with 2 to 15 percent gravel, 0 to 20 percent cobbles and 0 to 10 percent stones and boulders. It is strongly acid to slightly acid.
Some pedons have a BC or 2Bw horizon.
The 2BCd horizon has a hue of 10YR, value of 3 to 5 and chroma of 2 or 3. It is gravelly sandy loam, gravelly loamy sand, gravelly loamy coarse sand or gravelly coarse sandy loam or their very gravelly analogues. Rock fragment content by volume ranges from 15 to 45 percent with 15 to 35 percent gravel, 0 to 10 percent cobbles and 0 to 2 percent stones and boulders. The moist 1/3 bar bulk density of the fine earth fraction is from 1.8 to 2.0 gm/cm3. It is moderately acid to neutral.
COMPETING SERIES: These are the Greysolon, Normanna, Soudan and Wahlsten series. The Greysolon and Wahlsten soils have bedrock at depths of 51 to 102 cm. The Normanna soils formed in Superior Lobe till with substratum colors having hue of 5YR. Soudan soils have dense till with greater than 35 percent rock fragments in the lower third of the series control section and have sandy textures in the middle third of the series control section.
GEOGRAPHIC SETTING: These soils are on convex ridgetops and back slopes of drumlins and moraines. Slopes typically are 5 to 18 percent, but range from 1 to 45 percent. They formed in a coarse loamy mantle and the underlying dense coarse loamy basal Rainy Lobe till of Late Wisconsinan glaciation. Mean annual air temperature ranges from 2 to 6 degrees C., and mean annual precipitation ranges from 710 to 790 mm. Annual frost free days range from 90 to 120 days. The elevation above sea level ranges from 200 to 600 meters.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brimson, Bugcreek and Nevens soils. The somewhat poorly drained Brimson soils are on plane to slightly convex slopes, typically below the Toimi soils. The very poorly drained Bugcreek soils are on toeslopes or in drainageways and depressions. The poorly drained Nevens soils are on plane to slightly concave summits and footslopes.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained. Surface runoff is low to high. Saturated hydraulic conductivity is 1.41 to 14.11 micrometers per second (0.20 to 2.0 inches per hour) in the upper part and .01 to .42 micrometers per second (0.0015 to 0.06 inches per hour) in the lower part. The Toimi soils have a perched seasonal high saturation as high as 46 cm below the surface in spring in normal years. After rainfall events, a higher water table may be perched for brief periods of time. At the contact between the mantle and the dense till there is commonly a concentration of redoximorphic features that has a shallow penetration into the dense till along fractures and rock sockets.
USE AND VEGETATION: These soils are used mainly for timber production. Native vegetation was mixed deciduous and coniferous forest. Major tree species are quaking aspen, paper birch and balsam fir.
DISTRIBUTION AND EXTENT: MLRA-93A. Northeastern Minnesota. Moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: St. Louis County, Minnesota, (Duluth subset), 2007.
REMARKS: Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface to 10 cm below the surface (A horizon); cambic horizon - the zone from 10 to 89 cm (Bw horizons); oxyaquic subgroup based on saturation within 102 cm of the surface; isotic mineralogy based on lab data from the NSSL.
The previous classification of this soil was coarse-loamy, mixed, frigid Typic Dystrochrepts.
The designation of the 2BCd horizon is based on fractures and platy structure in the densic material. Clay and silt translocation can be seen between the horizontal plates when broken apart.
ADDITIONAL DATA: Refer to NSSL pedon number 95MN-137-541 for additional analysis.