Gázquez, Fernando and Calaforra, José María and Sanna, Laura and Forti, Paolo (2011) Espeleotemas de yeso: ¿Un nuevo proxy paleoclimático? = Gypsum speleothems: a new palaeoclimatic proxy? Real Sociedad Española de Historia Natural. Boletín. Sección Geológica, Vol. 105 (1-4), p. 15-24. ISSN 0583-7510. Article.
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As secondary carbonate deposits in cave, gypsum speleothems are also a proxy for Quaternary climate researches. According to the environmental characteristics in which they formed, they can be grouped in subaerial and underwater gypsum speleothems. The first ones grow in vadose conditions by evaporation of a Ca2+ and SO42- saturated solution. Gypsum caves in the karst massif of Sorbas (Almería, SE Spain) host some of the most relevant worldwide. On the other hand, underwater gypsum speleothems usually precipitate from hydrothermal water with high Ca2+ and SO42- concentration. Precipitation occurs very slowly and in high-stability conditions. The most important of them were found in the Cueva de los Cristales (Crystals’ cave) and Cueva de las Espadas (Swords’ cave), in the Naica mine (Chihuahua, Mexico) as well as in the giant geode of Pulpi (Almería, SE Spain). In both cases, stable isotopes composition and trace elements distribution together with geochronologic information from U-Th dating, could reveal palaeoclimate record that complement those obtained from carbonate speleothems. Stable isotope composition of crystallization water of gypsum (δD) records the characteristic of the aquifer and the evaporation rate within the cave during speleothem growth. Due to the fact that the gypsum deposition requires water from the solution, isotopic signal of gypsum speleothems might show past changes in the meteoric water supply, for example as a moisture source variations. In addition, oscillations in the cave temperature, precipitation rate or mixing deep (ancient and/or thermal) water with fresh meteoric one in hydrothermal systems could be detected by trace elements distributions in gypsum speleothems, thanks to the close relationship between these climatic factors and partition coefficient of each trace element. Finally, the study of speleothem growth direction will help to know the preferential direction of airflow inside the cave during gypsum precipitation, a useful tool in understanding the evolution of the karst system, like the opening of new cave entrance and/or gallery collapses.
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