Cave air control on dripwater geochemistry, Obir Caves (Austria): Implications for speleothem deposition in dynamically ventilated caves

Citation

Material Information

Title:
Cave air control on dripwater geochemistry, Obir Caves (Austria): Implications for speleothem deposition in dynamically ventilated caves
Series Title:
Geochimica et Cosmochimica Acta
Creator:
Spötl, Christoph
Fairchild, Ian J.
Tooth, Anna F.
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Co2 ( local )
Pco2 ( local )
Speleothems ( local )
Obir Caves ( local )
Genre:
serial ( sobekcm )

Notes

Abstract:
There are very few process studies that demonstrate the annual variation in cave environments depositing speleothems. Accordingly, we initiated a monitoring program at the Obir Caves, an Austrian dripstone cave system characterized by a seasonally changing air flow that results in a predictable pattern of high pCO2 during summer and low pCO2 in winter. Although similar seasonal changes in soil pCO2 occur, they are not directly connected with the changes in the subsurface since the dripwaters are fed from a well-mixed source showing little seasonal variation. Cold season flushing by relatively CO2-poor air enhances degassing of CO2 in the cave and leads to a high degree of supersaturation of dripwater with regard to calcite. Forced calcite deposition during the cold season also gives rise to a pronounced pattern of synchronous seasonal variations in electrical conductivity, alkalinity, pH, Ca and δ13CDIC which parallel variations recorded in δ13Ccave air. Chemical components unaffected by calcite precipitation (e.g., δD, δ18O, SiO2, SO4) lack a seasonal signal attesting to a long residence in the karst aquifer. Modeling shows that degassing of CO2 from seepage waters results in kinetically-enhanced C isotopic fractionation, which contrasts with the equilibrium degassing shown from the Soreq cave in Israel. The Obir Caves may serve as a case example of a dripstone cave whose seepage waters (and speleothems) show intra-annual geochemical variability that is primarily due to chemical modification of the groundwater by a dynamic, bidirectional subsurface air circulation.
Original Version:
Geochimica et Cosmochimica Acta, Vol. 69, no. 10 (2005-05-15).

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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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