LOCATION THROCKMORTON IN

Established Series
Rev. TRZ-KKN
11/2021

THROCKMORTON SERIES

The Throckmorton series consists of very deep, moderately well drained soils that are deep to dense till. The Throckmorton soils formed in loess, loamy glaciofluvium, and loamy till. They are on till plains. Slope ranges from 1 to 3 percent. Mean annual precipitation is about 914 mm (36 inches), and mean annual air temperature is about 10 degrees C (50 degrees F).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Mollic Oxyaquic Hapludalfs

TYPICAL PEDON: Throckmorton silt loam, on a 1 percent slope in a cultivated field at an elevation of about 216 meters (710 feet) above mean sea level. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 23 cm (0 to 9 inches); very dark gray (10YR 3/1) silt loam, dark grayish brown (10YR 4/2) dry; moderate medium granular structure; friable; neutral; abrupt smooth boundary. [18 to 20 cm (7 to 9 inches) thick]

Bt1--23 to 30 cm (9 to 12 inches); brown (10YR 4/3) silt loam; moderate fine subangular blocky structure; firm; common very fine vesicular pores; common distinct dark brown (10YR 3/3) organo-clay films on faces of peds; slightly acid; clear smooth boundary.

Bt2--30 to 56 cm (12 to 22 inches); dark yellowish brown (10YR 4/4) silty clay loam; moderate fine subangular blocky structure; firm; many very fine vesicular pores; common distinct dark brown (10YR 3/3) organo-clay films on faces of peds; strongly acid; clear smooth boundary.

Bt3--56 to 74 cm (22 to 29 inches); dark yellowish brown (10YR 4/4) silty clay loam; moderate medium subangular blocky structure; firm; many very fine vesicular pores; common distinct brown (10YR 4/3) clay films on faces of peds; very strongly acid; clear smooth boundary.

Bt4--74 to 86 cm (29 to 34 inches); yellowish brown (10YR 5/4) silty clay loam; moderate medium subangular blocky structure; firm; many very fine tubular pores; common distinct brown (10YR 4/3) clay films on faces of peds; few fine prominent yellowish brown (10YR 5/8) masses of iron accumulation in the matrix; few fine distinct grayish brown (10YR 5/2) iron depletions in the matrix; very strongly acid; clear smooth boundary. [Combined thickness of the Bt horizon is 36 to 74 cm (14 to 29 inches).]

2Bt5--86 to 107 cm (34 to 42 inches); dark yellowish brown (10YR 4/4) clay loam; moderate coarse subangular blocky structure; firm; many very fine tubular pores; common distinct dark brown (7.5YR 3/2) organo-clay films on faces of peds; common medium distinct grayish brown (10YR 5/2) iron depletions in the matrix; 1 percent gravel; very strongly acid; clear wavy boundary.

2Bt6--107 to 114 cm (42 to 45 inches); brown (10YR 4/3) sandy loam; moderate coarse subangular blocky structure; firm; many very fine tubular pores; common distinct dark brown (10YR 3/3) clay films on faces of peds; common medium distinct dark yellowish brown (10YR 4/6) masses of iron accumulation in the matrix; common fine black (N 2.5/) manganese accumulations; common medium faint grayish brown (10YR 5/2) iron depletions in the matrix; 12 percent gravel; moderately acid; clear smooth boundary. [Combined thickness of the 2Bt horizon is 15 to 76 cm (6 to 30 inches).]

3Bt7--114 to 147 cm (45 to 58 inches); brown (10YR 5/3) loam; weak coarse subangular blocky structure; firm; common very fine tubular pores; common distinct dark brown (10YR 3/3) clay films on faces of peds; few fine black (N 2.5/) manganese accumulations; common medium faint light brownish gray (10YR 6/2) iron depletions in the matrix; 6 percent gravel; slightly acid; gradual wavy boundary. [8 to 36 cm (3 to 14 inches) thick]

3Cd--147 to 165 cm (58 to 65 inches); yellowish brown (10YR 5/4) loam; massive, but has well defined horizontal and vertical fracture planes which define plates 5 to 13 cm (2 to 5 inches) horizontally and 1 to 2.5 cm (0.5 to 1 inch) vertically; very firm; common medium distinct light brownish gray (10YR 6/2) iron depletions in the matrix; 6 percent gravel; strongly effervescent; moderately alkaline.

TYPE LOCATION: Tippecanoe County, Indiana; about 3 miles southwest of West Point; 590 feet east and 100 feet north of the southwest corner of sec. 27, T. 22 N., R. 6 W.; USGS Westpoint, Indiana topographic quadrangle; lat. 40 degrees 18 minutes 59 seconds N. and long. 87 degrees 5 minutes 26.3 seconds W., NAD 27; UTM Zone 16, 492298 easting and 4462881 northing, NAD 83.

RANGE IN CHARACTERISTICS:
Thickness of the loess: 61 to 102 cm (24 to 40 inches)
Depth to the base of the argillic horizon: 102 to 152 cm (40 to 60 inches)
Depth to carbonates: 102 to 152 cm (40 to 60 inches)
Depth to redox depletions: 61 to 102 cm (24 to 40 inches)
Depth to densic contact: 102 to 152 cm (40 to 60 inches)

Ap or A horizon:
Hue: 10YR
Value: 3
Chroma: 1 to 3
Texture: silt loam
Reaction: strongly acid to neutral depending on liming history

Bt horizon:
Hue: 10YR
Value: 4 or 5
Chroma: 3 to 6
Texture: silt loam or silty clay loam
Clay content: 20 to 34 percent
Reaction: very strongly acid to slightly acid

2Bt horizon:
Hue: 7.5YR or 10YR
Value: 4 or 5
Chroma: 2 to 4
Texture: clay loam, sandy clay loam, or sandy loam
Clay content: 15 to 30 percent
Sand content: 30 to 60 percent
Rock fragment content: 1 to 14 percent
Reaction: very strongly acid to moderately acid

3Bt horizon:
Hue: 10YR
Value: 4 or 5
Chroma: 3 or 4
Texture: loam
Rock fragment content: 3 to 10 percent
Reaction: slightly acid or neutral

3Cd horizon:
Hue: 10YR
Value: 4 or 5
Chroma: 3 or 4
Texture: loam
Rock fragment content: 3 to 10 percent
Moist bulk density: 1.75 to 2.00 g/cc
Calcium carbonate equivalent: 15 to 40 percent
Reaction: slightly alkaline or moderately alkaline

COMPETING SERIES: These are the Barony, Downsouth, Grays, Hedrick, Juda, Kaneville, Newvienna, Richview, Vasa, Windere, and Wingate series. Barony soils do not have a 3B horizon formed in till in the lower part of the series control section. Downsouth and Newvienna soils do not have rock fragments in the lower part of the series control section. Grays and Juda soils have carbonates within a depth of 102 cm (40 inches). Hedrick, Kaneville, and Vasa soils are deeper than 102 cm (40 inches) to horizons with more than 30 percent sand. Richview soils are deeper than 152 cm (60 inches) to carbonates. Windere and Wingate soils do not have a 2B horizon formed in glaciofluvium and have moist bulk density of less than 1.75 g/cm3 in the lower part of the series control section.

GEOGRAPHIC SETTING: Throckmorton soils are on till plains thought to be Wisconsinan age. Slope ranges from 1 to 3 percent. The soils formed in 61 to 102 cm (24 to 40 inches) of loess and in the underlying loamy glaciofluvium and loamy till. Mean annual precipitation ranges from 889 to 965 mm (35 to 38 inches). Mean annual air temperature ranges from 10 to 11 degrees C (50 to 52 degrees F). Frost-free period ranges from 150 to 180 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Drummer, Millbrook, Octagon, Raub, and Toronto soils. The poorly drained Drummer soils are in depressions. The somewhat poorly drained Millbrook, Raub, and Toronto soils are on less sloping positions. Octagon soils are on more sloping areas along drainageways and on distinct rises where the loess is thinner.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained. The depth to the top of an intermittent perched high water table ranges from 61 to 107 cm (2 to 3.5 feet) between December and April in normal years. The potential for surface runoff is negligible to low. Saturated hydraulic conductivity is moderately high or high in the loess and glaciofluvium (4.23 to 14.11 micrometers/s); moderately high in the till subsoil (1.41 to 4.23 micrometers/s); and moderately high to low in the underlying material (0.07 to 1.41 micrometers/s). Permeability is moderate in the loess and glaciofluvium, moderately slow in the till subsoil, and slow or very slow in the underlying material.

USE AND VEGETATION: Most areas are used to grow corn, soybeans, or small grain. A few areas are used for hayland or pasture. Native vegetation is mixed prairie grasses and scattered hardwoods.

DISTRIBUTION AND EXTENT: West-central Indiana; MLRAs 111C and 111D. The type location is in MLRA 111D. The series is of small extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: AMHERST, MASSACHUSETTS

SERIES ESTABLISHED: Tippecanoe County, Indiana, 1993.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon (mollic intergrade): from the surface to a depth of 23 cm (Ap horizon).
Argillic horizon: from a depth of 23 to 147 cm (Bt, 2Bt, 3Bt horizons).
Densic contact: at 147 cm (top of the 3Cd horizon).
Aquic conditions: redox depletions in all horizons below a depth of 74 cm.

Representative NASIS data mapunit for this pedon is DMU ID 153113 in MO 11.

National Cooperative Soil Survey
U.S.A.