Precipitation of Salts from Mg2+-(Na+)-So42–-Cl– Playa–Lake Brines: The Endorheic Saline Ponds of La Mancha, Central Spain
Published:January 01, 1994
Salvador Ordóñez, Sergio Sánchez Moral, Maria De Los Angeles García Del Cura, Eduardo Rodriguez Badiola, 1994. "Precipitation of Salts from Mg2+-(Na+)-So42–-Cl– Playa–Lake Brines: The Endorheic Saline Ponds of La Mancha, Central Spain", Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models, Robin W. Renaut, William M. Last
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More than 25 ephemeral saline lakes are found in La Mancha, an endorheic region with a semi-arid climate in central Spain. The annual rainfall is 400 mm/yr, with an evaporation rate of 1,400 mm/yr. Many of the lakes occupy the small closed or nearly closed hydrological basins, approximately 10 km2 in extent. The area annually flooded by brines is approximately 0.5 km2. The water depth in the lakes during the rainy season (winter) is <0.5 m. In some lakes, precipitation of salts during summer develops a "bull's eye" pattern of concentrically zoned salts, with bischofite crusts in the innermost zone of the lake, then a zone of halite-epsomite crusts, followed by hexahydrite-halite crusts, and finally, hexahydrite-gypsum crusts in the outermost zone.
The thin crust of the outer zone is always overlain by organic muds; some crusts commonly display tepee structures. Salts precipitated in summer are dissolved during winter, and mass-balance solute models show some playas to be nearly closed systems. An experimental pond was built in one of the lakes (Quero). This pond has allowed us to monitor temporal variations in the concentration and temperature (both upper and lower layers) of the brine, and the precipitation of saline minerals. The sequence of minerals precipitated in the experimental pond agrees with the observed natural sequence; most salts grow at the air-brine interface. A direct correlation has been recognized between the vertical temperature patterns, and various parameters of the brine concentration during periods of brine "stagnation."
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Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes - This volume of papers grew out of a four-day symposium entitled ?Sedimentary and Paleolimnological Records of Saline Lakes? held at Saskatoon, Canada in August, 1991. The aim of this Special Publication is to bring together selected papers from this conference that deal specifically with the sedimentological, inorganic geochemical, and hydrological aspects of salt lakes and their stratigraphic records. This volume is divided into four sections. The first section contains papers that deal with modern saline lakes. The second section contains papers dealing with sedimentation and diagenesis of late Quaternary salt lakes. The third and fourth sections contain papers devoted to ancient (pre-Quaternary) Lacustrine sequences.