EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Farmed calcite δ18O, δ13C, and Δ47 at Ascunsă cave, Romania

Virgil Dragusin1,2, Vasile Ersek3, Alvaro Fernandez4, Roxana Ionete5, Andreea Iordache5, Nele Meckler4, Ionut Mirea1, and Ramona Zgavarogea5
Virgil Dragusin et al.
  • 1Emil Racoviță Institute of Speleology, Bucharest, Romania
  • 2Research Institute of the University of Bucharest, Bucharest, Romania
  • 3Department of Geography and Environmental Sciences, Northumbria University, Newcastle-upon-Tyne, United Kingdom
  • 4Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Norway
  • 5National Research and Development Institute for Cryogenics and Isotopic Technologies (ICSI), Râmnicu Vâlcea, Romania

Ascunsă cave (Romania) is the subject of a monitoring program since 2012. While the cave air temperature was very stable around 7°C for most of the time, it experienced in 2019 a 3°C rise, and remained high until the present.

We present here δ18O, δ13C, and clumped isotope results from calcite farmed at two drip points inside the cave (POM X and POM 2). POM X has a slower drip rate than POM 2 and deposits calcite more continuously. Calcite deposition has been shown to depend on cave air CO2 concentration, which controls the drip water pH and, further, the calcite saturation index.

In 2019, δ18O values at both sites quickly shifted to lower values as a response to the increase in temperature. At POM X, values were situated between approximately -7.2‰ and -7.6‰ before this transition, whereas in 2019 they shifted to -7.8‰ - -8.0‰. At POM 2, where values were generally lower, they shifted from -7.5‰ to -7.8‰ to -8.0‰.

Clumped isotope temperature estimates mostly agree, within measurement error, with measured cave temperature. This agreement is notable given that strong offsets are commonly observed in mid-latitude caves, reflecting kinetic fractionation effects. However, intervals with deviations from cave temperature are also observed, suggesting variations in isotopic disequilibrium conditions with time.

Here we will discuss these isotope changes in relation to cave air temperature and CO2 concentration, drip water isotope values and elemental chemistry, as well as in relation to drip rates, in order to improve our understanding of calcite precipitation and isotope effects in caves.

How to cite: Dragusin, V., Ersek, V., Fernandez, A., Ionete, R., Iordache, A., Meckler, N., Mirea, I., and Zgavarogea, R.: Farmed calcite δ18O, δ13C, and Δ47 at Ascunsă cave, Romania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7151,, 2021.