LOCATION MEGWIL CA
Established Series
Rev. ACF/JPS/SAA/ET
10/2016
MEGWIL SERIES
The Megwil series consists of very deep, moderately well drained soils formed in marine deposits derived from mixed sources. Megwil soils are on nearly level to gently sloping, dissected marine terraces and have slopes 0 to 5 percent. The mean annual precipitation is 1500 millimeters (59 inches) and the mean annual temperature is about 12 degrees C (53 degrees F).
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Oxyaquic Palehumults
TYPICAL PEDON: Megwil loam - on a nearly level, linear slope of 1 percent under orchard grass, buttercup, dandelion, and velvet grass at 6 meters (20 feet) elevation. (Colors are for moist soil unless otherwise stated. When described October 30, 2007, the soil was moist throughout).
Ap--0 to 30 centimeters (0 to 12 inches); very dark brown (10YR 2/2) loam, brown (10YR 4/3) dry; moderate very fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots throughout; common very fine tubular and common very fine irregular pores; moderately acid (pH 5.7); clear smooth boundary. (25 to 50 centimeters thick)
Bt1--30 to 52 centimeters (12 to 20 inches); strong brown (7.5YR 4/6) clay loam, yellowish brown (10YR 5/6) dry; moderate very fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots throughout; common very fine irregular and common very fine tubular pores; few faint clay films on faces of peds; strongly acid (pH 5.3); clear smooth boundary.
Bt2--52 to 75 centimeters (20 to 30 inches); strong brown (7.5YR 4/6) clay loam, yellowish brown (10YR 5/6) dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; common very fine roots throughout; common very fine irregular pores; few faint clay films on all faces of peds; common fine distinct irregular yellowish red (5YR 5/8) masses of oxidized iron with distinct boundaries in the matrix; very strongly acid (pH 5.0); clear smooth boundary.
Bt3--75 to 92 centimeters (30 to 36 inches); dark yellowish brown (10YR 4/6) clay loam, brownish yellow (10YR 6/6) dry; moderate fine and moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; few very fine and fine roots throughout; common very fine irregular pores; very few distinct clay films on all faces of peds; common fine distinct irregular strong brown (7.5YR 5/8) masses of oxidized iron in matrix and common fine prominent irregular dark grayish brown (2.5Y 4/2) iron depletions with clear boundaries on surfaces along pores; strongly acid (pH 5.5); gradual smooth boundary.
Bt4--92 to 122 centimeters (36 to 48 inches); dark yellowish brown (10YR 4/6) sandy clay loam, brownish yellow (10YR 6/6) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; few very fine roots throughout; common very fine irregular pores; very few distinct clay films on all faces of peds; many fine distinct irregular strong brown (7.5YR 5/8) masses of oxidized iron with clear boundaries in matrix and common fine prominent irregular dark grayish brown (2.5Y 4/2) iron depletions with clear boundaries on surfaces along pores; strongly acid (pH 5.5); gradual smooth boundary.
Bt5--122 to 162 centimeters (48 to 64 inches); dark yellowish brown (10YR 4/6) sandy clay loam, brownish yellow (10YR 6/6) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; common very fine irregular pores; very few distinct clay films on all faces of peds; common fine distinct irregular strong brown (7.5YR 5/8) masses of oxidized iron with clear boundaries and common fine prominent irregular dark grayish brown (2.5Y 4/2) iron depletions with clear boundaries in matrix; strongly acid (pH 5.3). (Combined thickness of Bt horizons 60-140 centimeters)
TYPE LOCATION: Del Norte County, California; located approximately 3 kilometers (1.9 miles) southeast of Crescent City, California; USGS Sisters Rock Quadrangle; WGS84 Decimal degrees 41.7473889 latitude,
-124.1595833 longitude, UTM Zone 10 403586mE 4622380mN; NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil is usually moist in all parts in the soil moisture control section in most years, but becomes nearly dry in the upper part from about September 15 to October 15 in most years. The soils have an udic soil moisture regime.
Soil temperature: The mean annual soil temperature at 50 centimeters (20 inches) is 12 to 14 degrees C (53 to 57 degrees F). The average summer soil temperature is about 18 degrees C and the average winter soil temperature is about 9 degrees C. The difference between average summer and winter soil temperatures is about 6 to 9 degrees C. The soil has a mesic soil temperature regime.
The umbric epipedon is 25 to 50 centimeters thick.
Particle-Size Control Section (weighted average):
Clay content 25 to 34 percent
Rock fragments: 0 to 5 percent gravel, 0 to 5 percent paragravel
Endosaturation: The water table is between 50 and 100 centimeters from about January through March and falls below 180 centimeters April through December.
Depth to redoximorphic features: 50 to 100 centimeters
Reaction: Very strongly to moderately acid
A or Ap horizon
Hue: 10YR or 7.5YR
Value: 2, 2.5 or 3, 3 through 5 dry
Chroma: 2 or 3, 2 or 3 dry
Texture of fine earth: loam
Rock fragments: 0 to 5 percent gravel
Clay content: 21 to 25 percent
Bt horizon
Hue: 7.5YR or 10YR
Value: 4 or 5, 5 through 7 dry
Chroma: 4 through 6, 6 dry
Texture of fine earth: sandy clay loam or clay loam
Rock fragments: 0 to 5 percent gravel
Clay content: 25 to 34 percent
Redoximorphic Features: fine iron-manganese masses and fine masses of oxidized iron
Quantity: none to many
Hue: 7.5YR or 10YR
Value: 5
Chroma: 4 to 8
Redoximorphic features: fine iron depletions
Quantity: none to many
Hue: 2.5Y
Value: 3 or 4
Chroma: 1 or 2
COMPETING SERIES: There are no competing series at this time.
GEOGRAPHIC SETTING: Megwil soils are on nearly level to gently sloping, slightly dissected marine terraces and have slopes of 0 to 5 percent. Elevations are 4 to 183 meters (10 to 600 feet). These soils form in marine deposits derived from mixed sources. A strong marine influence limits the diurnal and annual range of temperature. The climate is humid with cool, foggy summers and cool, wet winters. Mean annual precipitation is 890 to 2085 millimeters (35 to 90 inches). Mean annual temperature is 11 to 13 degrees C (51 to 55 degrees F). Frost free season is about 275 to 325 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Cannonball, and
Timmons soils which also occur on dissected marine terraces. Timmons soils lack redoximorphic features within the upper 100 centimeters. Cannonball soils occur under mixed conifer forest of
Sitka-spruce and redwood, where the difference between mean winter and mean summer soil temperatures is less than 6 degrees C.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: moderately well drained; low to medium runoff; moderately low saturated hydraulic conductivity.
USE AND VEGETATION: This soil is used predominantly for pasture, recreation and urban development. Vegetation includes California blackberry, common dandelion, white clover, sweet vernalgrass, brome, common velvetgrass, vernalgrass, blue grass, and other pasture grasses and forbs.
DISTRIBUTION AND EXTENT: California Coastal Redwood Belt; MLRA 4B. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Humboldt and Del Norte Counties Soil Survey, Northern Part, California, January 2013. Proposed 2010. The soil is named after Megwil Point, north of Trinidad, Ca.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
1. Umbric epipedon - the zone from 0 to 30 centimeters (A horizon).
2. Argillic horizon - the zone from 30 to 162 centimeters (Bt1, Bt2, Bt3, Bt4. Bt5).
3. Particle-size control section - the zone from 30 to 80 centimeters (Bt1, Bt2 horizons) averages 31 percent clay and 35 percent fine sand or coarser, by weight.
4. Palehumult feature: clay decrease with increasing depth is less than 20 percent from maximum: from 34 to 33 percent.
ADDITIONAL DATA:
NASIS User Pedon ID 07CA605429
Keys to Soil Taxonomy, 12th edition.
National Cooperative Soil Survey
U.S.A.