LOCATION BENTONSPORT IAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Typic Hapludolls
TYPICAL PEDON: Bentonsport extremely gravelly loam, on a southeast-facing, convex slope of 20 percent, in a mixed hardwood forest, at an elevation of about 183 meters above mean sea level. (Colors are for moist soil unless otherwise stated.)
A1--0 to 8 centimeters; very dark grayish brown (10YR 3/2) extremely gravelly loam, grayish brown (10YR 5/2) dry; weak very fine and fine granular structure; friable; common fine and medium roots; many distinct very dark gray (10YR 3/1) organic coats on faces of peds; about 51 percent pebbles; about 5 percent cobbles; about 5 percent stones; slightly effervescent; slightly alkaline; clear smooth boundary.
A2--8 to 20 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, grayish brown (10YR 5/2) dry; weak very fine and fine granular structure; friable; common fine and medium roots; many distinct very dark gray (10YR 3/1) organic coats on faces of peds; about 31 percent pebbles; about 5 percent cobbles; about 5 percent stones; slightly effervescent; slightly alkaline; gradual smooth boundary.
A3--20 to 46 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, grayish brown (10YR 5/2) dry; weak very fine and fine granular structure; friable; common fine and medium roots; about 21 percent pebbles; about 15 percent cobbles; about 5 percent stones; slightly effervescent; slightly alkaline; clear smooth boundary.
A4--46 to 81 centimeters; dark brown (10YR 3/3) very cobbly loam; weak very fine and fine subangular blocky structure; friable; few fine and medium roots; many distinct very dark grayish brown (10YR 3/2) organic coats on faces of peds; about 15 percent pebbles; about 15 percent cobbles; about 8 percent stones; slightly effervescent; slightly alkaline; gradual smooth boundary. (Combined thickness of the A horizon is 60 to 90 centimeters.)
Bw--81 to 104 centimeters; brown (10YR 4/3) extremely cobbly loam; weak fine subangular blocky structure; friable; few fine and medium roots; many distinct very dark grayish brown (10YR 3/2) and common distinct dark brown (10YR 3/3) organic coats on faces of peds; about 17 percent pebbles; about 30 percent cobbles; about 20 percent stones; slightly effervescent; moderately alkaline; clear smooth boundary. (13 to 25 centimeters thick)
Bt--104 to 122 centimeters; yellowish brown (10YR 5/4) extremely gravelly loam; weak fine subangular blocky structure; friable; few fine and medium roots; many distinct brown (10YR 4/3) clay films on faces of peds; very few prominent very dark gray (10YR 3/1) manganese or iron-manganese stains in root channels and pores; about 37 percent pebbles; about 25 percent cobbles; about 8 percent stones; strongly effervescent; moderately alkaline; clear smooth boundary. (10 to 40 centimeters thick)
C1--122 to 142 centimeters; yellowish brown (10YR 5/4) very cobbly loam; massive; friable; few fine and medium roots; very few prominent very dark gray (10YR 3/1) manganese or iron-manganese stains in root channels and pores; few distinct brown (10YR 4/3) coats on faces of peds; about 23 percent pebbles; about 25 percent cobbles; about 8 percent stones; strongly effervescent; moderately alkaline; gradual smooth boundary.
C2--142 to 155 centimeters; yellowish brown (10YR 5/4) very cobbly loam; massive; friable; few fine and medium roots; very few prominent very dark gray (10YR 3/1) manganese or iron-manganese stains in root channels and pores; few distinct brown (7.5YR 4/4) coats on faces of peds; about 8 percent pebbles; about 20 percent cobbles; about 8 percent stones; strongly effervescent; moderately alkaline; gradual smooth boundary.
C3--155 to 178 centimeters; light yellowish brown (10YR 6/4) very gravelly clay loam; massive; very firm; few fine and medium roots; few prominent very dark gray (10YR 3/1) manganese or iron-manganese stains in root channels and pores; about 37 percent pebbles; about 10 percent cobbles; few fine distinct strong brown (7.5YR 4/6) redoximorphic concretions; violently effervescent; moderately alkaline; clear smooth boundary. (Combined thickness of the C horizon is 25 to 75 centimeters.)
2C4--178 to 191 centimeters; olive gray (5Y 5/2), and light olive gray (5Y 6/2) gravelly silt loam; massive; very firm; few fine and medium roots; few prominent very dark gray (10YR 3/1) manganese or iron-manganese strains in root channels and pores; about 19 percent pebbles; about 4 percent cobbles; common medium prominent brownish yellow (10YR 6/8) and few fine prominent strong brown (7.5YR 5/8) redoximorphic concretions; strongly effervescent; moderately alkaline; clear smooth boundary. (0 to 25 centimeters thick)
2Cr--191 to 200 centimeters; olive gray (5Y 5/2) partly consolidated silty clay loam shale; strongly effervescent; strongly alkaline.
TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Van Buren County, Iowa subset; about 1 mile east of Bonaparte; located about 2,230 feet north and 720 feet west of the southeast corner of section 9, T. 68 N., R. 8 W.; USGS Bonaparte topographic quadrangle; lat. 40 degrees 42 minutes 10 seconds N. and long. 91 degrees 46 minutes 43 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness--60 to 90 centimeters
Depth to paralithic contact of shale bedrock--more than 150 centimeters
Depth to carbonates--0 to 10 centimeters
Clay content in the particle-size control section (weighted average)--18 to 35 percent
Sand content in the particle-size control section (weighted average)--20 to 50 percent
Rock fragment content--35 to 60 percent, mostly limestone and sandstone pebbles, cobbles and stones, some subhorizons range from 1 to 80 percent
A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 to 3
Texture--loam, silt loam, silty clay loam or gravelly, very gravelly, or extremely gravelly analogs of these textures
Clay content--15 to 35 percent,
Sand content--10 to 50 percent
Reaction--slightly alkaline or moderately alkaline
B horizon:
Hue--10YR
Value--4 or 5
Chroma--3 to 6
Texture--loam, clay loam or gravelly, very gravelly, extremely gravelly, cobbly, very cobbly, or extremely cobbly analogs of these textures
Clay content--18 to 35 percent, the most clayey subhorizon ranges from 28 to 35 percent
Sand content--20 to 50 percent
B/A clay ratio--less than 1.15
Reaction--slightly alkaline or moderately alkaline
C horizon:
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--3 to 6
Texture--loam, clay loam, or gravelly, very gravelly, extremely gravelly, cobbly, very cobbly, or extremely cobbly analogs of these textures
Clay content--18 to 35 percent
Sand content--25 to 50 percent
Reaction--slightly alkaline or moderately alkaline
2C horizon:
Hue--7.5YR to 5Y, or neutral
Value--4 to 6
Chroma--0 to 8
Texture--varies widely due to stratification in original shale
Clay content--15 to 27 percent
Sand content--5 to 45 percent
Reaction--slightly alkaline or moderately alkaline
COMPETING SERIES: These are the
Kankakee,
Lacrescent,
Marlean, and
May City series.
Kankakee--do not have carbonates in the upper half of the series control section
Lacrescent--have a mollic epipedon 25 to 50 centimeters thick
Marlean--have a mollic epipedon 20 to 50 centimeters thick
May City--have a mollic epipedon 15 to 36 centimeters thick
GEOGRAPHIC SETTING:
Parent material--loamy colluvium, loamy-skeletal colluvial sediments from limestone and sandstone, and the underlying residuum weathered from shale
Landform--very steep side slopes on high structural benches, remnants of interfluves, and uplands
Slope--25 to 40 percent
Elevation--150 to 300 meters above sea level
Mean annual air temperature--9 to 12 degrees C
Mean annual precipitation--865 to 1,040 millimeters
Frost-free period--175 to 210 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Gosport,
Lindley,
Nordness, and
Reedscreek soils.
Gosport--are on lower landscape positions and have a clay content that averages 36 to 58 percent in the particle-size control section
Lindley--are on landscape positions similar to those of the Bentonsport soils and contain less than 5 percent rock fragments throughout the profile
Nordness--are on landscape positions similar to those of the Bentonsport soils and have a lithic contact of limestone bedrock within a depth of 50 centimeters
Reedscreek--are on lower landscape positions on floodplains and are frequently saturated at a depth between 1.2 and 1.8 meters during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained--a frequently saturated zone does not occur within a depth of 1.8 meters during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Saturated hydraulic conductivity--1.0 to 10.0 micrometers per second
USE AND VEGETATION:
These soils are mostly permanent pasture or woodland. Native vegetation is deciduous trees (hickory and oak).
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Dissected till plains
MLRA--Iowa and Missouri Heavy Till Plain (109)
LRR M; southeastern Iowa
Extent--small
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Van Buren County, Iowa, 1995.
REMARKS:
Particle-size control section--the zone from a depth of 25 to 100 centimeters;
series control section--the zone from the surface to a depth of 150 centimeters.
Diagnostic horizons and features recognized in this pedon include:
mollic epipedon--the zone from the surface to a depth of 81 centimeters (A1, A2, A3, and A4 horizons);
cambic horizon--the zone from a depth of 81 to 122 centimeters (Bw and Bt horizons);
udic moisture regime.
Cation-exchange activity class is supported by laboratory data, NSSL.
Taxonomic Version--Keys to Soil Taxonomy, tenth edition, 2006.
Bentonsport soils were included with Nordness or Sogn soils in previous surveys.
ADDITIONAL DATA:
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska - user pedon ID 92IA177005 (http://ssldata.nrcs.usda.gov/).