LOCATION CHURNABOG TX

Tentative Series
WLM-JKW-RM
09/2013

CHURNABOG SERIES

The Churnabog series consists of very deep, very poorly drained, very slowly permeable soils that formed in clayey alluvium of Holocene age. These nearly level soils are in shallow depressions of abandoned channels, backswamps, and flats on flood plains of the Brazos, San Bernard, and Colorado Rivers on the Texas coastal plain. Slope ranges from 0 to 1 percent. Mean annual air temperature is about 21 degrees C (70 degrees F), and mean annual precipitation is 1321 mm (52 in).

TAXONOMIC CLASS: Very-fine, smectitic, hyperthermic Typic Epiaquerts

TYPICAL PEDON: Churnabog clay -- on a south facing, concave, less than 1 percent slope, at an elevation of 12 m (40 ft) in microlow in bottomland hardwoods. (Colors are for moist soil unless otherwise stated.)

A--0 to 14 cm (0 to 5 in); very dark gray (2.5Y 3/1) clay, very dark gray (2.5Y 3/1) dry; moderate fine and medium subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; many fine and medium and few coarse roots; common fine and medium interstitial and tubular pores; few cracks 1 to 2 cm wide; less than 1 percent fine prominent strong brown (7.5YR 5/6) masses of oxidized iron with clear boundaries on faces of peds; less than 1 percent fine prominent brownish yellow (10YR 6/6) masses of oxidized iron with diffuse boundaries lining pores; slightly acid; clear smooth boundary. (10 to 38 cm [4 to 15 in] thick)

Bg--14 to 44 cm (5 to 17 in); very dark gray (10YR 3/1) clay, very dark gray (10YR 3/1) dry; moderate medium and coarse angular blocky structure; extremely hard, extremely firm, very sticky and very plastic; common fine and medium and few coarse roots; common fine tubular pores; few faint slickensides; common distinct pressure faces; few cracks 1 to 2 cm wide; less than 1 percent black (10YR 2/1) iron-manganese nodules 2 to 3 mm in diameter with a brownish yellow (10YR 6/8) calcareous rind; 1 percent very fine black (10YR 2/1) iron-manganese nodules without rinds; less than 1 percent fine prominent yellowish red (5YR 5/6) iron-manganese masses with clear boundaries; less than 1 percent fine prominent yellowish brown (10YR 5/6) masses of oxidized iron with diffuse boundaries lining pores; 1 percent calcium carbonate equivalent; slightly alkaline; clear smooth boundary. (25 to 53 cm [10 to 21 in] thick)

Bssg1--44 to 82 cm (17 to 32 in); very dark gray (10YR 3/1) clay, gray (10YR 5/1) dry; moderate medium and coarse wedge structure parting to weak medium angular blocky; extremely hard, extremely firm, very sticky and very plastic; common fine and medium roots; few fine tubular pores; common distinct slickensides; many distinct pressure faces; few cracks 1 to 2 cm wide; 1 percent black (10YR 2/1) iron-manganese nodules 2 to 3 mm in diameter with a brownish yellow (10YR 6/8) calcareous rind; less than 1 percent very fine black (10YR 2/1) iron-manganese nodules without rinds; 1 percent fine distinct light olive brown (2.5Y 5/3) masses of oxidized iron with diffuse boundaries lining pores; 1 percent calcium carbonate equivalent; slightly alkaline; gradual wavy boundary. (Combined thickness of the Bssg horizons is 43 to 97 cm [17 to 38 in])

Bssg2--82 to 129 cm (32 to 51 in); very dark gray (10YR 3/1) clay, gray (10YR 5/1) dry; moderate medium and coarse wedge structure parting to moderate medium angular blocky; extremely hard, extremely firm, very sticky and very plastic; few fine roots; few fine tubular pores; many distinct slickensides; many distinct pressure faces; few cracks 1 to 2 cm wide; 3 percent crayfish krotovinas; few krotovinas filled with a mixture of calcareous reddish brown (5YR 5/4) and brown (10YR 5/3) clay; 1 percent masses and nodules of calcium carbonate up to 2 mm in size; 2 percent calcium carbonate equivalent; slightly alkaline; gradual wavy boundary.

Bkss--129 to 152 cm (51 to 60 in); 70 percent dark gray (10YR 4/1) and 30 percent brown (10YR 5/3) clay, 70 percent gray (10YR 5/1) dry, and 30 percent pale brown (10YR 6/3) dry; moderate medium and coarse wedge structure parting to moderate medium angular blocky; extremely hard, extremely firm, very sticky and very plastic; few fine roots; few fine pores; many distinct slickensides; many distinct pressure faces; 5 percent crayfish krotovinas filled with a mixture of calcareous reddish brown (5YR 5/4) and brown (10YR 5/3) clay; 1 percent masses of calcium carbonate up to 2 mm in size; 8 percent nodules of calcium carbonate 5 to 10 mm in diameter; 8 percent calcium carbonate equivalent; slightly effervescent; slightly alkaline; gradual wavy boundary. (25 to 117 cm [10 to 46 in] thick)

2Bk1--152 to 178 cm (60 to 70 in); 45 percent brownish yellow (10YR 6/6) and 30 percent light brownish gray (10YR 6/2) silty clay loam, 45 percent brownish yellow (10YR 6/6) dry, and 30 percent light gray (10YR 7/2) dry; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; very hard, very firm, sticky and plastic; few fine roots; 5 percent crayfish krotovinas filled with a mixture of calcareous reddish brown (5YR 5/4) and brown (10YR 5/3) clay; 10 percent masses of calcium carbonate 2 to 15 mm in size with a few having nodules up to 2 mm in size in the center; 1 percent fine and medium distinct brown (7.5YR 5/4) masses of oxidized iron with sharp boundaries on faces of peds; light brownish gray (10YR 6/2) matrix color consists of iron depletions on faces of peds; few very fine mica flakes; 21 percent calcium carbonate equivalent; strongly effervescent; moderately alkaline; gradual wavy boundary. (Combined thickness of the 2Bk horizons is 0 to 53 cm [0 to 21 in])

2Bk2--178 to 196 cm (70 to 77 in); 35 percent pale brown (10YR 6/3), 35 percent light brownish gray (10YR 6/2), and 30 percent strong brown (7.5YR 5/8) silty clay loam, 35 percent very pale brown (10YR 7/3) dry, 35 percent light gray (10YR 7/2) dry, and 30 percent strong brown (7.5YR 5/8) dry; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; very hard, very firm, sticky and plastic; few fine roots between peds; common prominent clay films on vertical faces of peds; 3 percent crayfish krotovinas filled with a mixture of calcareous reddish brown (5YR 5/4) and brown (10YR 5/3) clay; 10 percent masses and nodules of calcium carbonate from 2 to 20 mm in size; light brownish gray (10YR 6/2) matrix consists of iron depletions on faces of peds; few very fine mica flakes; 18 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; gradual wavy boundary.

3Bss--196 to 220 cm (77 to 87 in); reddish brown (5YR 4/3) clay, reddish brown (5YR 5/3) dry; moderate medium wedge structure parting to moderate medium angular blocky; extremely hard, extremely firm; very sticky and very plastic; few fine roots; common faint slickensides; common distinct pressure faces; 1 percent fine strong brown (7.5YR 5/8) masses of oxidized iron with sharp boundaries on faces of peds; 3 percent fine prominent gray (10YR 6/1) iron depletions with clear boundaries on pressure faces and slickensides; 1 percent masses of calcium carbonate with hard, pitted centers up to 5 mm in size; 20 percent calcium carbonate equivalent; violently effervescent; moderately alkaline.

TYPE LOCATION: Brazoria County, Texas; from the intersection of Texas Highway 35 and Farm Road 524 in Old Ocean; about 3.6 miles west on Farm Road 524 to pipeline right-of-way; 0.2 mile north of right-of-way to east running road; 0.5 mile east on road; located about 200 feet south in an area of bottomland hardwoods. Latitude: 29 degrees, 6 minutes, 54 seconds N; Longitude: 95 degrees, 46 minutes, 37.4 seconds W. Ashwood USGS topographic quadrangle; NAD 83.

RANGE IN CHARACTERISTICS:
Soil Moisture: An aquic soil moisture regime. September through May are the wettest months, while June through August are the driest months. These soils remain ponded for periods of 2 continuous weeks to as long as 24 continuous weeks during normal years. Desiccation cracks that are 5 mm or more wide through a thickness of 25 cm or more, within 50 cm of the mineral surface, stay open for less than 60 cumulative days. The period when cracks remain open, is from June to August in normal years.

Mean annual soil temperature: 20 to 22 degrees (68 to 72 degrees F)
These are cyclic soils comprised of low relief, indistinct microlows and microhighs in wetter areas to distinct microlows and microhighs in dryer areas. The distance from the center of the microlow to the highest point on the microhigh is from 1 to 3 meters (3 to 10 feet). Elevation difference between bottom of microlow and top of microhigh is from 6 to 20 cm (2 to 8 in)

Depth to secondary calcium carbonate: microlow is 30 to 60 cm (12 to 24 in); microhigh is 0 to 30 cm (0 to 12 in)
Thickness of the mollic epipedon: microlow is 89 to 140 cm (35 to 55 in); microhigh is 64 to 86 cm (25 to 34 in)

Depth to redox concentrations: 0 to 50 cm (0 to 20 in)
Depth to redox depletions: 60 to 130 cm (24 to 51 in)
Depth to episaturation: 0 to 75 cm (0 to 30 in)
Thickness of the free water: 10 to 75 cm (4 to 30 in)
Vertic features: 30 to 200 cm (12 to 79 in)

Particle-size control section (weighted average)
Clay content: 60 to 75 percent

A horizon (microlow)
Hue: 10YR, 2.5Y, or N/
Value: 2, 2.5, or 3
Chroma: 1
Texture: clay
Clay content: 55 to 75 percent
Redox concentrations: amount-0 to 2 percent, size-fine, contrast-distinct or prominent, boundary-sharp, clear, or diffuse, location-lining pores and faces of peds, shades-red, brown, yellow
Calcium carbonate equivalent: 0 to 1 percent
Identifiable secondary calcium carbonate: amount-0 to 1 percent, size-up to 5 mm, kind-nodules
Effervescence: none or very slight
Reaction: slightly acid or neutral

A horizon (microhigh)
Hue: 10YR, 2.5Y, or N/
Value: 2 to 4
Chroma: 1
Texture: clay
Clay content: 55 to 75 percent
Redox concentrations: amount-0 to 1 percent, size-fine, contrast-distinct or prominent, boundary-sharp, location-lining pores and faces of peds, shades-brown, yellow
Calcium carbonate equivalent: 1 to 5 percent
Identifiable secondary calcium carbonate: amount-0 to 3 percent, size-fine or medium, kind-nodules
Effervescence: very slight or slight
Reaction: slightly alkaline or moderately alkaline

Bg horizon (microlow)
Hue: 2.5Y, 10YR, or N/
Value: 2, 2.5, or 3
Chroma: 1
Texture: clay
Clay content: 60 to 75 percent
Redox concentrations: amount-0 to 2 percent, size-fine, contrast-distinct or prominent, boundary-sharp, clear, or diffuse, location-lining pores and faces of peds, shades-red, brown, or yellow
Iron-manganese concentrations: amount-0 to 3 percent, size-fine or medium, kind-nodules
Calcium carbonate equivalent: 0 to 2 percent
Identifiable secondary calcium carbonate: amount-0 to 1 percent, size- up to 10 mm, kind-nodules
Effervescence: none to slight
Reaction: slightly acid or neutral

Bg horizon (microhigh)
Hue: 2.5Y, 10YR, N/
Value: 3 to 5
Chroma: 1
Texture: clay
Clay content: 60 to 75 percent
Redox concentrations: amount-0 to 2 percent, size-fine, contrast-distinct or prominent, boundary-sharp, location-lining pores and faces of peds, shades-red, brown, or yellow
Iron-manganese concentrations: amount-0 to 3 percent, size-fine or medium, kind-nodules
Calcium carbonate equivalent: 1 to 5 percent
Identifiable secondary calcium carbonate: amount-1 to 5 percent, size- up to 10 mm, kind-nodules
Effervescence: very slight or slight
Reaction: slightly alkaline or moderately alkaline

Bssg horizon (microlow)
Hue: 2.5Y, 10YR, or N/
Value: 2, 2.5, 3
Chroma: 1
Texture: clay
Clay content: 60 to 75 percent
Redox concentrations: amount-0 to 5 percent, size-fine, contrast-distinct or prominent, boundary-sharp or diffuse, location-lining pores and faces of peds, shades-red, brown, or yellow
Iron-manganese concentrations: amount-0 to 3 percent, size- fine or medium, kind-nodules
Calcium carbonate equivalent: 0 to 2 percent
Identifiable secondary calcium carbonate: amount-0 to 1 percent, size- up to 5 mm, kind-nodules
Effervescence: none to slight
Reaction: neutral to slightly alkaline

Bssg horizon (microhigh)
Hue: 2.5Y, 10YR, or N/
Value: 4 to 6
Chroma: 1
Texture: clay
Clay content: 60 to 75 percent
Redox concentrations: amount-0 to 2 percent, size-fine, contrast-distinct or prominent, boundary-sharp, location-lining pores and faces of peds, shades-red, brown, or yellow
Iron-manganese concentrations: amount-0 to 3 percent, size- fine or medium, kind-nodules
Calcium carbonate equivalent: 2 to 10 percent
Identifiable secondary calcium carbonate: amount-2 to 5 percent, size- up to 10 mm, kind-nodules
Effervescence: very slight to strong
Reaction: slightly alkaline or moderately alkaline

Bkss horizon (microhigh and microlow)
Hue: 5YR, 7.5YR, or 10YR
Value: 4 to 6
Chroma: 1 to 6
Texture: clay
Clay content: 60 to 75 percent
Redox concentrations: amount-0 to 2 percent, size-fine, contrast-distinct or prominent, boundary-sharp, location-lining pores and faces of peds, shades-red, brown, or yellow
Redox depletions: amount-0 to 2 percent, size-fine or medium, contrast- distinct or prominent, boundary-sharp, location- faces of peds and lining pores, shades-gray, brown
Iron-manganese concentrations: amount-0 to 3 percent, size- fine or medium, kind-nodules
Calcium carbonate equivalent: 5 to 25 percent
Identifiable secondary calcium carbonate: amount-5 to 12 percent, size- 2 to 25 mm, kind-soft masses or nodules, location-matrix
Effervescence: strong or violent
Reaction: slightly alkaline or moderately alkaline

2Bk horizon (microhigh and microlow where present)
Hue: 5YR, 7.5YR, or 10YR (variegated matrix)
Value: 5 to 7
Chroma: 1 to 8
Texture: loam or silty clay loam
Clay content: 25 to 35 percent
Redox depletions: amount-3 to 10 percent, size-fine or medium, contrast- distinct or prominent, boundary-sharp, location-lining faces of peds and pores, shades-gray, brown
Iron-manganese concentrations: amount-0 to 2 percent, size- fine or medium, kind-nodules
Calcium carbonate equivalent: 5 to 15 percent
Identifiable secondary calcium carbonate: amount-5 to 15 percent, size- 2 to 25 mm, kind-threads, soft masses, nodules, location-matrix
Mica flakes: amount-0 to 2 percent, size-fine
Effervescence: strong or violent
Reaction: slightly alkaline or moderately alkaline

3Bss horizon (microhigh and microlow where present)
Hue: 5YR, 7.5YR, 10YR
Value: 4 to 6
Chroma: 3 or 4
Texture: clay or silty clay
Clay content: 45 to 70 percent
Redox depletions: amount-3 to 20 percent, size-fine or medium, contrast- distinct or prominent, boundary-sharp, location-lining faces of peds and pores, shades-gray, brown
Iron-manganese concentrations: amount-0 to 2 percent, size- fine or medium, kind-nodules
Calcium carbonate equivalent: 5 to 25 percent
Identifiable secondary calcium carbonate: amount-1 to 10 percent, size- fine or medium, kind-threads, soft masses
Effervescence: strong or violent
Reaction: slightly alkaline or moderately alkaline

COMPETING SERIES: There are no other series in this family. Similar soils are the Brazoria(TX), Fausse (LA), Ganado(TX), Pledger(TX), Sharkey (LA), and Sumpf (TX) series.
Brazoria soils: have a chroma of 3 or more, or value of 4 or more, in the upper 30 cm (12 in) of the solum.
Fausse soils: typically have a muck surface layer and do not have slickensides.
Ganado soils: have a fine particle-size control section.
Pledger soils: do not pond for long or very long periods.
Sharkey soils: have gypsum within 100 cm (40 in) of the mineral surface, and are in a thermic temperature regime.
Sumpf soils: have mixed clay mineralogy, are in a thermic temperature regime, and have endosaturation.

GEOGRAPHIC SETTING:
Parent material: clayey Holocene age fluvial sediments
Landform: shallow depressions of abandoned channels, backswamps and flats on flood plains of the Brazos, San Bernard, and Colorado Rivers on the Texas coastal plain.
Slope: 0 to 1 percent
Mean annual air temperature range: 21 to 22 degrees C (69 to 72 degrees F)
Mean annual precipitation range: 1,016 to 1,321 mm (40 to 52 in)
Precipitation Pattern: May, June, July, September and October are the wettest months, with averages of 111 to 171 mm (4.36 to 6.75 in) per month. February through April are the driest months with average of 57 to 72 mm (2.25 to 2.83 in) per month.
Frost-free period: 260 to 280 days
Elevation: 3 to 31 m (10 to 100 ft)
Thornthwaite annual P-E indices: 60 to 66

GEOGRAPHICALLY ASSOCIATED SOILS: These are the, Asa(TX), Brazoria(TX), Norwood(TX), Pledger(TX), and Sumpf(TX) series
Asa soils: are on slightly higher landscapes and are less clayey throughout
Brazoria soils: are on slightly higher landscapes and do not pond for long or very long periods
Norwood soils: are on slightly higher landscapes and are less clayey throughout
Pledger soils: are on slightly higher landscapes and do not pond for long or very long periods
Sumpf soils: are on remnants of abandoned river channels and typically have higher chroma in the upper part

DRAINAGE AND PERMEABILITY: Very poorly drained. Permeability is very slow. Runoff is negligible. These soils are rarely to frequently flooded for brief duration, except where protected. The soil is ponded, or the surface is saturated, for long to very long periods during the months of September to May. Saturated hydraulic conductivity is low.

USE AND VEGETATION: Used for pasture and wildlife land. Where drained, the soil is used for growing grain sorghum, corn, soybeans, and other crops. Native vegetation consists of savannah panic grass, dwarf palmetto, water hickory, cedar elm, green ash, and sugarberry. Clayey Bottomland ecological site (150AY527TX).

DISTRIBUTION AND EXTENT: Gulf Coast Prairie (MLRA 150A in LRR T) on the central part of the Texas coastal plain. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas

SERIES PROPOSED: Brazoria County, Texas, 2007. The name is coined.

REMARKS: The series was formerly included in the Pledger series. The series are separated based on an interagency study, Soil Characterization and Hydrological Monitoring Project, Brazoria County, Texas, Bottomland Hardwood Vertisols, W. L. Miller and A. L. Bragg. 2007. USDA-NRCS, Temple, Texas.
Diagnostic horizons and features recognized in this pedon are:

Particle size control section: 25 to 100 cm. (10 to 39 in) (Bw, Bss horizon)
Mollic epipedon: 0 to 129 cm (0 to 51 in). (A, Bw, Bssg1 and Bssg2 horizons)
Redoximorphic concentrations: 0 to 200 cm (0 to 79 in) (A, Bg, Bssg1, Bssg2, Bkss, 2Bk1, 2Bk2, 3Bss horizons)
Redoximorphic depletions: 129 to 200 cm (51 to 79 in) (Bkss, 2Bk1, and 2Bk2 horizons)
Vertic features: The presence of slickensides at 14 to 152 cm (6 to 60 in) (Bg, Bssg1, Bssg2, and Bkss horizons)
Episaturation: The zone of saturation at 0 to 75 cm (0 to 30 in) (A, Bg, Bssg horizons)
Aquic conditions: 0 to 75 cm (0 to 30 in)

ADDITIONAL DATA: Characterization data from the National Soil Survey Laboratory are available on pedon (S98TX-039-006), project number 98P0586, from the series type location.

Taxonomic Version: Keys to Soil Taxonomy, Eleventh Edition, 2010.

National Cooperative Soil Survey
U.S.A.