Speleothems in gypsum caves and their paleoclimatological significance |
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| Authors: | J M Calaforra P Forti A Fernandez-Cortes |
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| Institution: | (1) R.G. Water Resources and Environmental Geology, University of Almeria, Almeria, Spain;(2) Department of Earth Sciences and Environmental Geology, University of Bologna, Bologna, Italy |
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| Abstract: | This article highlights the relationship between speleothems growing inside gypsum caves and the particular climate that existed
during their development. Speleothems in gypsum caves normally consist of calcium carbonate (calcite) or calcium sulphate
(gypsum) and the abundance of such deposits greatly differs from zone to zone. Observations carried out over the last 20 years
in gypsum caves subjected to very different climates (Italy, Spain, New Mexico, northern Russia, Cuba, Argentina) highlight
wide variation in their cave deposits. In arid or semi-arid climates, the speleothems are mainly composed of gypsum, whilst
in temperate, humid or tropical regions, carbonate formations are largely predominant. In polar zones no speleothems develop.
These mineralogical details could be useful paleoclimatic indicators of climate change. The interpretation proposed is based
on the fact that in gypsum karst the kind of speleothems deposited is determined by competition between the two principal
mechanisms that cause precipitation of calcite and gypsum. These mechanisms are completely different: calcite speleothem evolution
is mainly controlled by CO2 diffusion, while gypsum deposits develop mostly due to evaporation. Therefore, the prevalence of one kind of speleothem over
the other, and the relationship between the solution–precipitation processes of calcite and gypsum, may provide evidence of
a specific paleoclimate. Additionally, other non-common deposits in gypsum caves like moonmilk, cave rafts and dolomite speleothems
can be used as markers for the prevalence of long, dry periods in humid areas, seasonal changes in climate, or rainfall trends
in some gypsum areas. Moreover, the dating of gypsum speleothems could contribute paleoclimatic data relating to dry periods
when calcite speleothems are not deposited. In contrast, the dating of calcite speleothems in gypsum caves could identify
former wet periods in arid zones. |
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| Keywords: | Gypsum Caves Speleothems Paleoclimatology |
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