Climate monitoring in the Caumont cave and quarry system (northern France) reveal near oxygen isotopic equilibrium conditions for carbonate deposition

Authors

Ingrid Bejarano-Arias, UMR 6266 IDEES CNRS, University of Rouen Normandy, FranceFollow
Carole Nehme, UMR 6266 IDEES CNRS, University of Rouen Normandy, FranceFollow
Sebastian Breitenbach, Northumbria University, UKFollow
Hanno Meyer, Alfred Wegener Institute for Polar and Marine Research, GermanyFollow
Sevasti Modestou, Northumbria University, UKFollow
Damase Mouralis, UMR 6266 IDEES CNRS, University of Rouen Normandy, FranceFollow

Highlights

• We monitored air temperature, dripwater stable isotopes and modern carbonate, deposited on glass plates at Caumont
• Dripwater δ¹⁸O values reflect thorough mixing in the epikarst and some bias towards the winter season
• Modern calcite δ¹³C indicate that prior carbonate precipitation might occur during summer
• Modern carbonate deposition analysis showed the isotope system is at/very near isotope equilibrium
• Our results show that Caumont cave is suitable for the study of climate trends in the past

Abstract

The study of modern cave deposits forming under near isotopic equilibrium conditions can potentially help disentangle the processes influencing the oxygen isotope system and suitability of stalagmites as archives of past hydrological or thermal changes. We used cave monitoring to evaluate the impact of kinetic isotope fractionation and assess the conditions under which modern cave carbonates form in the Caumont cave and quarry system, located in Normandy, northwest France. Over 20 months, we collected climatological data, dripwater, and modern carbonate samples at 2–4-week intervals at three different stations inside the Caumont cave and quarry system. We find highly stable (10.4 ± 0.3°C – 11.3 ± 0.1°C) temperature in the deeper sections of the Caumont cave and quarry system. The temporal dynamics of δ¹⁸O_drip indicates that the drip water composition in Caumont reflects the original (though subdued) signal of precipitation, rather than the impact the seasonal to interannual cave air temperature has on isotopic fractionation. The monitoring reveals that δ¹³C of modern carbonate is influenced by prior carbonate precipitation that occurs during the summer season when evapotranspiration can minimize effective infiltration. Comparison of δ18O from dripwater and modern calcite, precipitated on glass plates and collected every two to four weeks, reveals that modern calcite forms near oxygen isotope equilibrium. A Hendy test on modern carbonate deposited on a stalagmite-shaped glass flask over 20 months confirms this finding because neither does δ¹³C increase with distance from the apex, nor are δ¹³C and δ¹⁸O positively correlated. We conclude that the δ¹³C signal in speleothems reflect summer (and longer-term) prior carbonate precipitation in response to effective infiltration dynamics, and that the δ¹⁸O signal likely reflects annual to multi-annual changes in the composition of precipitation above the cave.

DOI

https://doi.org/10.5038/1827-806X.53.1.2482

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

Recommended Citation

Bejarano-Arias, I., Nehme, C., Breitenbach, S.F.M., Meyer, H., Modestou, S., Mouralis, D., 2024. Climate monitoring in the Caumont cave and quarry system (northern France) reveal near oxygen isotopic equilibrium conditions for carbonate deposition. International Journal of Speleology, 53(1), 13-23. https://doi.org/10.5038/1827-806X.53.1.2482