LOCATION WILLWOOD WY+COEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed, mesic Typic Torriorthents
TYPICAL PEDON: Willwood very cobbly sand - rangeland (Colors are for dry soil unless otherwise noted.)
A1--0 to 5 inches; Gray (N 5/) very cobbly sand, very dark gray (2.5Y 3/1) moist, single grained; loose 70 percent water worn basalt gravel, cobbles, and stones; calcareous; moderately alkaline (pH 8.2); diffuse boundary. (4 to 6 inches thick)
C--5 to 60 inches; Gray (N 5/) very gravelly loamy sand, very dark gray (2.5Y 3/1) moist; single grained; loose; 60 percent basalt gravel, cobbles, and stones; most of the sand in the matrix is dark gray basalt sand; calcareous. Several feet thick.
TYPE LOCATION: Park County, Wyoming; approximately 1,100 feet north of Willwood Dam in sec. 9, T.54N., R.100W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at a depth of 20 inches is 48 degrees to 50 degrees F. Mean summer soil temperature is 62 degrees to 68 degrees F. Depth to uniformly calcareous material is 0 to 10 inches. A few pedons have some accumulation of visible calcium carbonate and/or calcium sulfate. Calcium carbonate equivalent ranges from 0 to 15 percent. Gypsum content is 0 to 5 percent. The soils are mildly to strongly alkaline. Exchangeable sodium percentage ranges from 0 to 15 percent. Some pedons have faint mottles of low contrast in the control section. The 10-to 40-inch control section is very gravelly or very cobbly loamy sand or sand with 35 to 85 percent rock fragments, mainly basalt gravel and cobbles. The A and C horizons have hue of 2.5Y or 10YR, value of 4 or 5 dry, 3 or 4 moist, and chroma of 1 or 2. The sand and silt fractions contain 5 to 20 percent dark colored magnetic ferromagnesian-rich minerals.
COMPETING SERIES: These are the Alderdale, Bluewing, Burbank, Inmo, and Skaha series. Alderdale soils have a lithic contact at depths of less than 40 inches. Burbank soils have a xeric moisture regime. Bluewing soils have a winter moisture distribution pattern and developed in parent sediments consisting mainly of rounded quartzitic gravel and cobble. Inmo soils occur in areas of winter rainfall and are very strongly alkaline in part of the control section and formed in sediments derived principally from granite with a high proportion of medium and coarse angular granite sand and fine and very fine angular granite gravel. Skaha soils are noncalcareous to depths of more than 40 inches and have a xeric moisture regime.
GEOGRAPHIC SETTING: Willwood soils are on the edges of old terrace or fan surfaces or at the margins of floodplains and recent terraces. Elevations range from 3,800 to 5,200 feet. Slope gradients range from 0 to about 6 percent. These soils formed in alluvial deposits derived principally from basalt rock. At the type location the average annual precipitation is 7 inches with peak periods of precipitation during the spring and early summer months. Mean annual temperature is 45 degrees F and mean summer temperature is 69 degrees F. Frost-free season is 110 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Avent, Sharland, and Shoshone soils. Avent soils have sand, gravel, and cobble beds at depths of 25 to 40 inches. Shoshone soils have coarse-loamy control sections. Sharland soils have argillic horizons.
DRAINAGE AND PERMEABILITY: Excessively drained; slow runoff; very rapid to rapid permeability
USE AND VEGETATION: These soils are used almost exclusively as native pastureland. Native vegetation is big sage, cactus, and scattered grasses.
DISTRIBUTION AND EXTENT: North-central Wyoming. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Park County (Big Horn River Irrigated Area), Wyoming, 1972.
OSED scanned by NSSQA. Last revised by state on 4/73.