42
WALLACE H. FULLER
of the surface. Like the Durargids they are relatively high in glass. The
duripans are cemented with silica and usually contain some lime. With
increasing depth, duripans often grade into petrocalcic horizons.
The Durorthids occur most frequently on fans or river terraces under
sparse desert vegetation. All appear to have had volcanic ash or glass
present at one time. There is evidence that the horizon has been influenced
by a high water table at one time or another. Some are salty.
4. Salorthids
The Salorthids are the Orthids that have a salic (salty) horizon within
75 cm of the surface, or within 1 meter of the surface for 1 month or
more if saturated with water. They have no calcic, gypsic horizon above
the salic horizon or duripan within 1 meter of the surface. Salorthids may
be known better as Solonchaks. Dry soils are encrusted with white salt
in a thin or thick layer. The salts have come to the surface by capillary
rise as well as deposit. Vegetation is sparse and salt tolerant. These soils
occur most frequently in play as (intermittent lakes) but can be found on
terraces, fans, and deltas.
5. Paleorthids
Paleorthids are Orthids with a petrocalcic horizon that has its upper
boundary within 1 meter of the soil surface. They have no duripan within
this limit nor do they have a salic horizon within 75 cm of the surface
if saturated with water within 1 meter of the surface for 1 month or more.
V. Physical Desert Surfaces
A. CLAY
Desert soils may, characteristically, have an argillic or clayey horizon
formed or synthesized during one or more of the glacial periods when the
climate was more humid. The silicate clays may have developed to a significant extent. During more recent times of drier climate, petrocalcic horizons and duripans may have formed and, in some instances, obscured the
clayey characteristics.
The clay content of many desert Bt horizons is higher than in other horizons of the soil profile. In zonal desertic soils, the ratio of the clay in the
B3 horizon to that in the A horizon ranges from 1.2 to 2.0 (Western Regional Soil Survey Work Group, 1964). Weathering processes in sierozems
of Central Asia, for example, are suggested (Rozanov, 1951) as being
sufficiently active to cause the accumulation of clay. In Arizona, Yesilsoy
WALLACE H. FULLER
of the surface. Like the Durargids they are relatively high in glass. The
duripans are cemented with silica and usually contain some lime. With
increasing depth, duripans often grade into petrocalcic horizons.
The Durorthids occur most frequently on fans or river terraces under
sparse desert vegetation. All appear to have had volcanic ash or glass
present at one time. There is evidence that the horizon has been influenced
by a high water table at one time or another. Some are salty.
4. Salorthids
The Salorthids are the Orthids that have a salic (salty) horizon within
75 cm of the surface, or within 1 meter of the surface for 1 month or
more if saturated with water. They have no calcic, gypsic horizon above
the salic horizon or duripan within 1 meter of the surface. Salorthids may
be known better as Solonchaks. Dry soils are encrusted with white salt
in a thin or thick layer. The salts have come to the surface by capillary
rise as well as deposit. Vegetation is sparse and salt tolerant. These soils
occur most frequently in play as (intermittent lakes) but can be found on
terraces, fans, and deltas.
5. Paleorthids
Paleorthids are Orthids with a petrocalcic horizon that has its upper
boundary within 1 meter of the soil surface. They have no duripan within
this limit nor do they have a salic horizon within 75 cm of the surface
if saturated with water within 1 meter of the surface for 1 month or more.
V. Physical Desert Surfaces
A. CLAY
Desert soils may, characteristically, have an argillic or clayey horizon
formed or synthesized during one or more of the glacial periods when the
climate was more humid. The silicate clays may have developed to a significant extent. During more recent times of drier climate, petrocalcic horizons and duripans may have formed and, in some instances, obscured the
clayey characteristics.
The clay content of many desert Bt horizons is higher than in other horizons of the soil profile. In zonal desertic soils, the ratio of the clay in the
B3 horizon to that in the A horizon ranges from 1.2 to 2.0 (Western Regional Soil Survey Work Group, 1964). Weathering processes in sierozems
of Central Asia, for example, are suggested (Rozanov, 1951) as being
sufficiently active to cause the accumulation of clay. In Arizona, Yesilsoy