Search results for "Stalactite"
showing 4 items of 4 documents
Are oxygen isotope fractionation factors between calcite and water derived from speleothems systematically biased due to prior calcite precipitation …
2021
Abstract The equilibrium oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) is an important quantity in stable isotope geochemistry and allows in principle to infer temperature variations from carbonate δ18O if carbonate formation occurred in thermodynamic equilibrium. For this reason, many studies intended to determine the value of the oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) for a wide range of temperatures using modern cave calcite and the corresponding cave drip water or ancient speleothem carbonate and fluid inclusion samples. However, the picture that emerges from all of these studies indicates that speleothem calcite i…
The effects of drip rate and geometry on the isotopic composition of speleothems: Evaluation with an advection-diffusion-reaction model
2022
Abstract The curvature and slope of speleothem surfaces have been shown to affect the reaction rates in the aqueous carbonate system by altering the thickness of the CaCO3-precipitating solution. However, the effects of speleothem geometry and drip rate on the speleothem’s carbon and oxygen isotopic composition have yet to be investigated. Over more strongly sloping surfaces, solutions are thinner and flow faster. The effects of thinner and faster-flowing solutions on the isotopic composition of carbonate minerals precipitated from these solutions are of opposite sense. Thinner solutions enhance rates of CO2 degassing and mineral formation, increasing the degree of isotopic distillation of …
A stalactite record of four relative sea-level highstands during the Middle Pleistocene Transition
2017
International audience; Ice-sheet and sea-level fluctuations during the Early and Middle Pleistocene are as yet poorly understood. A stalactite from a karst cave in North West Sicily (Italy) provides the first evidence of four marine inundations that correspond to relative sea-level highstands at the time of the Middle Pleistocene Transition. The speleothem is located ∼97 m above mean sea level as result of Quaternary uplift. Its section reveals three marine hiatuses and a coral overgrowth that fixes the age of final marine ingression at 1.124 ± 0.2, thus making this speleothem the oldest stalactite with marine hiatuses ever studied to date. Scleractinian coral species witness light-limited…
Submerged speleothems and sea level reconstructions: a global overview and new results from the Mediterranean Sea
2021
This study presents a global overview of the submerged speleothems used to reconstruct paleo sea levels and reports new results from two stalactites collected in the Mediterranean Sea. Coastal cave deposits significantly contributed to the understanding of global and regional sea-level variations during the Middle and Late Quaternary. The studied speleothems cover the last 1.4 Myr and focused mainly on Marine Isotope Stages (MIS) 1, 2, 3, 5.1, 5.3, 5.5, 7.1, 7.2, 7.3 and 7.5. The results indicate that submerged speleothems represent extraordinary archives that can provide detailed information on former sea-level changes. The two stalactites collected in the central Mediterranean Sea, at Fa…