LOCATION GUAYAMA PREstablished Series
TAXONOMIC CLASS: Clayey, mixed, active, isohyperthermic, shallow Typic Haplustalfs
TYPICAL PEDON: Guayama gravelly clay loam--naturalized pastureland (Colors are for moist soil).
Ap--0 to 2 inches; very dark brown (7.5YR 2.5/2) gravelly clay loam; moderate fine and medium granular structure; soft, friable; slightly sticky, slightly plastic; many fine roots; common fine interstitial pores; about 25 percent, by volume, pebbles and 2 percent cobbles; moderately alkaline; noneffervescent; abrupt smooth boundary. (2 to 8 inches thick)
Bt--2 to 13 inches; dark reddish brown (5YR 3/4) extremely paragravelly clay; massive, parting to weak fine subangular blocky structure; soft, friable; sticky, slightly plastic; few fine roots; common fine interstitial pores; few faint clay films on face of peds and pore linings; about 45 percent, by volume, paragravels and 20 percent paracobbles; slightly acid; noneffervescent; clear wavy boundary. (4 to 9 inches thick)
Cr--13 to 23 inches; highly fractured unconsolidated chert; abrupt wavy boundary (4 to 10 inches thick)
R--23 inches; hard consolidated chert bedrock.
TYPE LOCATION: Cabo Rojo, Puerto Rico. Approximately 4.4 miles northwest of La Parguera Community and about 0.6 mile northeast of Rancho Cabassa homestead 1n naturalized pastureland. USGS Parguera topographic quadrangle (1966); lat. 17 degrees 59 minutes 32 seconds N. and long. 67 degrees 06 minutes 45 seconds W.
RANGE IN CHARACTERISTICS: Depth to fractured unconsolidated rock ranges from 11 to 18 inches. Depth to hard consolidated bedrock ranges from 15 to 20 inches. Reaction ranges from slightly acid to moderately alkaline throughout.
The A or Ap horizon has hue of 5YR to 10YR, value of 2.5 to 4, and chroma of 2 to 4. Texture is clay loam or clay in the fine-earth fraction. Content of pebbles and cobbles ranges from 20 to 55 percent, by volume.
The Bt horizon has hue of 2.5YR or 5YR, value of 3 to 6, and chroma of 4 to 8. Texture is clay in the fine-earth fraction. Content of paragravels and paracobbles range from 25 to 65 percent, by volume.
The BC horizon, where present, has hue of 5YR or 7.5YR, value of 4 to 6, and chroma of 4 to 8. Texture is clay loam or their gravelly analogs.
The Cr horizon is composed of unconsolidated basalt, chert or rhyolite. It can be excavated with difficulty with hand tools, and is rippable by mechanical equipment.
The R layer is composed of hard fractured basalt, chert or rhyolite bedrock.
COMPETING SERIES: There are no known series in the same family.
GEOGRAPHIC SETTING: Guayama soils are on side slopes and summits of hills and mountains on the Semiarid Mountains and Valleys MLRA. Slopes range from 12 to 60 percent. They formed in residuum and colluvium material weathered from basalt, chert and rhyolite. The climate is semiarid tropical. The average annual precipitation ranges from 33 to 37 inches and the average annual temperature ranges from 82 to 86 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Amelia, Bermeja (T) and Maguayo series. Amelia soils are on alluvial fans, are very deep and have clayey-skeletal subsoil. Bermeja (T) soils are on similar positions but do not have an argillic horizon. Maguayo soils are on alluvial fans, are very deep and have clayey subsoils.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Most areas of Guayama soils are used for pastureland. The vegetation consists of native and introduced xerophytic grasses, shrubs and trees.
DISTRIBUTION AND EXTENT: Side slopes and summits of hills and mountains of the Semiarid Mountains and Valleys MLRA. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Soil Survey of Puerto Rico; 1942.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - the zone from 0 to 2 inches (Ap horizon).
Argillic horizon - the zone from 2 to 13 inches (Bt horizon).
Paralithic contact - the contact at 13 inches (Cr horizon).
Lithic contact - the contact at 23 inches (R horizon).
This soil formed in the Mariquita Chert Formation (KJm).
The type location was moved to its present location in 2005. The classification was updated with the 11/2004 draft from Clayey, mixed, active, isohyperthermic Lithic Haplustalfs to Clayey, mixed, active, isohyperthermic, shallow Typic Haplustalfs based on the recognition of a paralithic contact.
ADDITIONAL DATA: Characterization pedon - Cabo Rojo Municipality, Puerto Rico; S61PR-079-003. Sample by NSSL, Lincoln, NE., 03/1961.
Guayama soils are in MLRA 271.