Carbon and oxygen isotope study of the active water-carbonate system in a karstic Mediterranean cave: Implications for paleoclimate research in semiarid regions
- Geological Survey of Israel, Jerusalem (Israel); and others
In a semiarid climatic zone, such as the Eastern Mediterranean region, annual rainfall variations and fractionation processes in the epikarst zone exert a profound influence on the isotopic compositions of waters seeping into a cave. Consequently, the isotopic compositions of speleothems depositing from cave waters may show complex variations that need to be understood if they are to be exploited for paleoclimate studies. This is confirmed by a four-year study of the active carbonate-water system in the Soreq cave (Israel). The {sigma}{sup 18}O (SMOW) values of cave waters range from -6.3 to - 3.5{per_thousand}. The highest {sigma}{sup 18}O values occur at the end of the dry season in waters dripping from stalactites, and reflect evaporation processes in the epikarst zone, whereas the lowest values occur in rapidly dripping (fast-drip) waters at the peak of the rainy seasons. However, even fast-drip waters are about 1.5{per_thousand} heavier than the rainfall above the cave, which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone. {sigma}{sup 13}C (PDB) values of dissolved inorganic carbon (DIC) vary from -15.6 to -5.4{per_thousand}, with fast-drip waters having lower {sigma}{sup 13}C values (mostly-15.6 to -12{per_thousand}) and higher DIC concentrations relative to pool and stalactite-drip water. The los {sigma}{sup 13}C values of fast-drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil-CO{sub 2} derived from overlying C{sub 3}-type vegetation and marine dolomite host rock. The 10{per_thousand} variation in the {sigma}{sup 13}C values associated with contemporaneous speleothems in order to clarify the effects of degassing from those due to differing vegetation types. 55 refs., 10 figs., 1 tab.
- OSTI ID:
- 530432
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 60, Issue 2; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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