LOCATION BIGFORK                 OK+AR

Established Series
Rev. JWF:RCB
03/2021

BIGFORK SERIES

The Bigfork series consists of moderately deep to hard chert, well drained, moderately permeable soils that formed in material weathered from chert or novaculite that is tilted 35 degrees from horizontal of Ordovician age. These gently sloping to very steep soils are on ridges of uplands in the Ouachita Mountains land resource area. Slopes are 3 to 60 percent. Mean annual temperature is 17 degrees C (62 degrees F.) and mean annual precipitation is 1219 mm (48 in).

TAXONOMIC CLASS: Loamy-skeletal, siliceous, semiactive, thermic Typic Hapludults

TYPICAL PEDON: Bigfork very stony silt loam, in a Bigfork-Yanush association 20 to 45 percent slopes mapunit, in forest. (Colors are for moist soil unless otherwise stated.)

Oi-- 1 to 0 cm (.5 to 0 in); very dark brown (10YR 2/2) litter of leaves and twigs.

A-- 0 to 13 cm (0 to 5 in); yellowish brown (10YR 5/4) very stony silt loam; moderate medium granular structure; hard, friable; common very fine and fine roots inside peds; few medium and coarse roots inside peds; 50 percent chert fragments by volume greater than 76 mm in diameter and 10 percent chert fragments by volume from 2 mm to 76 mm in diameter; strongly acid; clear smooth boundary. (Thickness/Combined thickness is 8 to 23 cm [3 to 9 in].)

Bt-- 13 to 89 cm (5 to 35 in); brown (7.5YR 5/4) very stony silty clay loam; weak fine subangular blocky structure; very hard, friable; common fine roots inside peds; few fine to coarse roots between peds; patchy clay films on faces of peds; 40 percent chert fragments by volume greater than 76 mm in diameter and 10 percent chert fragments by volume from 2 mm to 76 mm in diameter; very strongly acid; abrupt irregular boundary. (Thickness/Combined thickness is 46 to 94 cm [18 to 37 in].)

R-- 89 to 226 cm (35 to 40 in); hard chert bedrock, tilted 35 degrees from a horizontal plane.

TYPE LOCATION: Pushmataha County, Oklahoma; about 4 miles north of Tuskahoma, Oklahoma; 1,100 feet west and 400 feet north of the southeast corner of section 1, T. 2 N., R. 19 E.

USGS topographic quadrangle: Yanush, OK
Latitude: 34 degrees, 40 minutes, 2.021 seconds N
Longitude: 95 degrees, 15 minutes, 19.043 seconds W
Datum: NAD83

Decimal Degrees
Std Latitude: 34.667228
Std Longitude: -95.255290

UTM Easting: 3838455 m
UTM Northing: 293352 m
UTM Zone: 15S

RANGE IN CHARACTERISTICS: Solum thickness and depth to hard bedrock ranges from 51 to 127 cm (20 to 50 in) and due to the irregular boundary between the Bt horizon and the underlying tilted bedrock it is extremely variable within short distances.
An udic soil moisture regime. The soil moisture control section is not dry in any part for as long as 90 cumulative days in normal years.

A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5
Chroma of 2 to 4.
Thickness: Where the A horizon has moist value and chroma of 3, it is less than 6 inches thick.
Texture is stony, very stony, very gravelly, or extremely gravelly analogues of loam, silt loam, or silty clay loam.
Rock Fragments: amount-35 to 90 percent by volume; size-15 to 30 percent by volume is 2 mm to 76 mm in diameter and 20 to 60 percent by volume is greater than 76 mm in diameter; kind- chert
Reaction (pH): slightly acid to strongly acid (5.1 - 6.5)

E horizons: where present
Thickness: 2 to 8 inches thick.
Colors are 1 to 2 values and chroma higher than A horizon
Texture: stony, very stony, very gravelly, or extremely gravelly analogues of loam, silt loam, or silty clay loam.
Rock Fragments: amount-35 to 90 percent by volume; size-15 to 30 percent by volume is 2 mm to 76 mm in diameter and 20 to 60 percent by volume is greater than 76 mm in diameter; kind- chert
Reaction (pH): slightly acid to strongly acid (5.1 - 6.5)

Bt horizon:
Hue: 5YR to 10YR
Value: 3 to 5
Chroma: 4 to 8
Texture: stony, very stony, very gravelly or extremely gravelly analogues of clay loam or silty clay loam.
Rock Fragments: Content of chert fragments are similar to the A horizon.
Reaction (pH): medium acid to very strongly acid. (4.5 - 6.0)

R layer:
Bedrock: hard chert or novaculite bedrock that is tilted 20 to 60 degrees from horizontal.

COMPETING SERIES: These are the Avant, Cobstone, Lillington, Saffell, and Zafra series in the same family.
Avant soils: are underlain by an R/C horizon and can be dug with power equipment.
Cobstone soils: are very deep.
Lillington soils: have sola greater than 152 cm (60 in) thick.
Saffell soils: are deeper than 102 cm (40 in) to bedrock.
Zafra soils: are underlain with hard sandstone and typically have redder hue in the Bt horizon.

GEOGRAPHIC SETTING: .
Parent material: material weathered from chert or novaculite of Ordovician age
Landscape: Ouachita Mountains
Landform: gently sloping to very steep tops of the hills or ridges
Slope: 3 to 60 percent
Precipitation Pattern: evenly distributed throughout the year
Mean annual precipitation: 1067 to 1422 mm (42 to 56 in)
Thornthwaite P-E Index: 70 to 76
Mean annual air temperature: 14 to 18 degrees C (57 to 64 degrees F)
Frost-free period: 200 to 220days
Elevation: 243 to 427 m (800 to 1400 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: This includes the Avant, Bengal, Bismarck, and Yanush series.
Avant soils: occur on similar landscapes.
Bismarck soils: occur on similar landscapes.
Bengal soils: occur on foot slopes.
Yanush soils: occur on foot slopes.

DRAINAGE AND PERMEABILITY:
Drainage class: well
Permeability class: moderate
Runoff: rapid or very rapid on 3 to 60 percent slopes

USE AND VEGETATION:
Major uses: Used mainly for growing trees.
Native vegetation: post oak and blackjack oak with small amounts of
shortleaf pine.
Ecological sites assigned to phases and components of this series are listed below. Current ecological site assignments are in Web Soil Survey. Components of this series include the following ecological sites: ?(List Ecosites here)

DISTRIBUTION AND EXTENT:
General area: Ouachita Mountains of Oklahoma and possibly in Arkansas.
Land Resource Region: N-East and Central Farming and Forest Region
Major Land Resource Area: 119-Ouachita Mountains
Extent: moderate

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: TEMPLE, TEXAS

SERIES ESTABLISHED: Pushmataha County, Oklahoma; 1977.

REMARKS: These soils were formerly included in the Bodine series.

Diagnostic horizons and features recognized in the series are:

Ochric epipedon: 0 to 13 cm (0 to 5 in) (A horizon)
Argillic horizon: 13 to 89 cm (5 to 35 in) (Bt horizon)
Lithic contact: hard chert or novaculite at 89 cm (35 in) (R horizon)

ADDITIONAL DATA: Oklahoma State University Data for two pedons. Sample Numbers 70-OK-64-2 and 70-OK-64-3.

TAXONOMIC VERSION: Keys to Soil Taxonomy, 12 Edition, 2014.

---

National Cooperative Soil Survey
U.S.A.