Carbon and oxygen isotope study of the active water-carbonate system in a karstic Mediterranean cave: Implications for paleoclimate research in semiarid regions
- Permanent Link:
- Carbon and oxygen isotope study of the active water-carbonate system in a karstic Mediterranean cave: Implications for paleoclimate research in semiarid regions
- Series Title:
- Geochimica et Cosmochimica Acta
- Bar-Matthews, Miryam
- Publication Date:
- Subjects / Keywords:
- Isotopic Compositions ( local )
Cave Water ( local )
Carbonate-Water System ( local )
- serial ( sobekcm )
- 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 Î´18O (SMOW) values of cave waters range from âˆ’6.3 to âˆ’3.5%.. The highest Î´18O 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%. heavier than the rainfall above the cave, which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone. Î´13C (PDB) values of dissolved inorganic carbon (DIC) vary from âˆ’15.6 to âˆ’5.4%., with fast-drip waters having lower Î´13C values (mostly âˆ’15.6 to âˆ’12%.) and higher DIC concentrations relative to pool and stalactite-drip water. The low Î´13C values of fast-drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil-CO2 derived from overlying C3-type vegetation and marine dolomite host rock. The Î´18O (PDB) values of various types of present-day low-magnesium calcite (LMC) speleothems range from âˆ’6.5 to âˆ’4.3%. and Î´13C values from âˆ’13 to âˆ’5.5%. and are not correlated with speleothem type. An analysis of Î´18O values of present-day calcite rafts and pool waters shows that they form in oxygen isotope equilibrium. Similarly, the measured ranges of Î´13C and Î´18O values for all types of present-day speleothems are consistent with equilibrium deposition at cave temperatures. The Î´13Câ€“Î´18O range of contemporary LMC thus reflects the var
- Original Version:
- Geochimica et Cosmochimica Acta, Vol. 60, no. 2 (1996-01).
- Source Institution:
- University of South Florida Library
- Holding Location:
- University of South Florida
- Rights Management:
- This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.
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