54
WALLACE H. FULLER
or hard nodules, in veinings along root or worm channels, or tongues, and
in layers. Lime also is found coating soil particles, gravel, stones, and roots.
Lime tends to accumulate in a layer in the soil at a place near or at
the mean depth of moisture penetration. These carbonate layers vary considerably in concentration, depth, compaction, and density. In zonal and
some intrazonal soils the carbonate-enriched layer generally develops at
the bottom of the illuvial horizon from parent material. Lime also may
accumulate as a result of the leaching of transient dust that blows onto
the soil and is caught in a rainstorm. Some of the carbonates and more
soluble salts are carried down into the soil and the dust moves on. This
explains, in part at least, the observation that lime may be found in Aridisols even where the parent material is very low in calcium (Gile et al,
1966).
2. Origin
The origin of massive, thick lime or caliche and its genesis have been
a matter of considerable speculation because of its varied nature even
within short distances on the same terrain (Breazeale and Smith, 1930;
Gile et al, 1966). Fossils of humid climates, lake beds, and solution cavities in thick, limy layers suggest that desert soil has not always been dry
and that more than one pedogenic process has been involved. Massive,
thick carbonate layers could form by means of deposition in bodies of
water or translocation from the upper to the lower part of the profile. Some
desert soils appear to have formed over lake bottom accumulations of lime.
Others have formed over carbonate-rich layers not related to the present
land surface. Yesilsoy (1962), for example, by using the carbon dating
found that the age of deposit of the carbonate carbon increased considerably with depth in an old alluvium desert soil in Arizona. At about 1 meter
the age of the CaC0 3 layer was found to be less than 2300 years before
present, at 1.5 meter the age was about 9800 years, and at 2 meter over
32,000 years. It is believed that many of the present desert land surfaces
appear to have been stable through one or more interglacial stages when
the climate was dry. Soils on these surfaces may have had sufficient time
to accumulate a thick lime layer. Evidences of solution cavities indicate
alternate stages of wet and dry climates.
B. GYPSUM
1. Characteristics
Gypsum (CaS0 4 -2H 2 0) accumulations are not uncommon in desert
soils. They vary from salt-affected soils almost free of gypsum to large
WALLACE H. FULLER
or hard nodules, in veinings along root or worm channels, or tongues, and
in layers. Lime also is found coating soil particles, gravel, stones, and roots.
Lime tends to accumulate in a layer in the soil at a place near or at
the mean depth of moisture penetration. These carbonate layers vary considerably in concentration, depth, compaction, and density. In zonal and
some intrazonal soils the carbonate-enriched layer generally develops at
the bottom of the illuvial horizon from parent material. Lime also may
accumulate as a result of the leaching of transient dust that blows onto
the soil and is caught in a rainstorm. Some of the carbonates and more
soluble salts are carried down into the soil and the dust moves on. This
explains, in part at least, the observation that lime may be found in Aridisols even where the parent material is very low in calcium (Gile et al,
1966).
2. Origin
The origin of massive, thick lime or caliche and its genesis have been
a matter of considerable speculation because of its varied nature even
within short distances on the same terrain (Breazeale and Smith, 1930;
Gile et al, 1966). Fossils of humid climates, lake beds, and solution cavities in thick, limy layers suggest that desert soil has not always been dry
and that more than one pedogenic process has been involved. Massive,
thick carbonate layers could form by means of deposition in bodies of
water or translocation from the upper to the lower part of the profile. Some
desert soils appear to have formed over lake bottom accumulations of lime.
Others have formed over carbonate-rich layers not related to the present
land surface. Yesilsoy (1962), for example, by using the carbon dating
found that the age of deposit of the carbonate carbon increased considerably with depth in an old alluvium desert soil in Arizona. At about 1 meter
the age of the CaC0 3 layer was found to be less than 2300 years before
present, at 1.5 meter the age was about 9800 years, and at 2 meter over
32,000 years. It is believed that many of the present desert land surfaces
appear to have been stable through one or more interglacial stages when
the climate was dry. Soils on these surfaces may have had sufficient time
to accumulate a thick lime layer. Evidences of solution cavities indicate
alternate stages of wet and dry climates.
B. GYPSUM
1. Characteristics
Gypsum (CaS0 4 -2H 2 0) accumulations are not uncommon in desert
soils. They vary from salt-affected soils almost free of gypsum to large