TY - JOUR
T1 - Cave air control on dripwater geochemistry, Obir Caves (Austria): Implications for speleothem deposition in dynamically ventilated caves
AU - Spotl, C
AU - Fairchild, Ian
AU - Tooth, AF
PY - 2005/5/15
Y1 - 2005/5/15
N2 - 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 pCO(2), during summer and low pCO(2), in winter. Although similar seasonal changes in Soil pCO(2) 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 delta(13)C(DIC) which parallel variations recorded in delta(13)C(cave air). Chemical components unaffected by calcite precipitation (e.g., delta D,delta(18)O,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. Copyright (c) 2005 Elsevier Ltd.
AB - 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 pCO(2), during summer and low pCO(2), in winter. Although similar seasonal changes in Soil pCO(2) 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 delta(13)C(DIC) which parallel variations recorded in delta(13)C(cave air). Chemical components unaffected by calcite precipitation (e.g., delta D,delta(18)O,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. Copyright (c) 2005 Elsevier Ltd.
UR - http://www.scopus.com/inward/record.url?scp=19044375228&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2004.12.009
DO - 10.1016/j.gca.2004.12.009
M3 - Article
VL - 69
SP - 2451
EP - 2468
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -