Dynamics of Evaporite Distribution in Soils on a Fan-Playa Transect in the Carrizo Plain, California
1989
Eghbal, M. K. | Southard, R. J. | Whittig, L. D.
Investigation of the distribution and dynamics of evaporites along an alluvial fan-playa transect in the Carrizo Plain, CA, shows that the overall salt concentration increases toward the center of the playa. Within profiles along the transect, the highest salt concentrations are found in the lower part of profiles. Sodium, K, Mg, Cl, and SO₄ concentrations increase along the transect toward Soda Lake. Calcium concentration, in the form of gypsum, is generally higher in profiles in the middle of the transect. Concentrations of Na, Ca, Mg, Cl, and SO₄ increase with depth in profiles away from Soda Lake as a function of a greater degree of leaching; higher concentrations of these ions are found toward the surface in profiles closer to Soda Lake due to capillary movement from the groundwater. Halite is the only mineral in the surface horizons. Gypsum is more common in lower horizons, closer to ground water, and is the common salt in soils farther away from Soda Lake. Other soluble evaporites, including halite, loeweite [Na₁₂Mg₇(SO₄)₁₃ · 15H₂O], and bloedite [Na₂Mg(SO₄)₂ · 4H₂O], together with gypsum, are found in extracts of soils near Soda Lake. A seasonal influence on the anion and cation distribution generally is noticeable only in soils with intermediate salt concentrations. Higher concentrations of anions and cations are found following the dry season. The orderly differences in anion and cation concentrations within most of the profiles and along the transect reflect the well established differences in solubility of the different salts.
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