Tritium dating of dripwater from Villars Cave (SW-France)

Abstract

Abstract The tritium content of rainwaters and dripwaters was monitored from 2008 to 2016 to determine the age of the dripwaters in Villars Cave, SW-France. Dripwater was collected at two stations, one in the upper gallery and the other in the lower gallery of the cave. Stable isotopes have been monitored at these two stations since 1997. The infiltration time of the rainwater between the surface and the cave galleries was determined using a simple one-dimensional model of the infiltration of recharge waters. The model was forced by monthly precipitation and the concentration of tritium in precipitation reconstructed from the IAEA isotope network and our own measurements in rainwater collected at the Villars site. The age of the dripwaters is 7.0\u202f±\u202f0.5 years for the upper gallery (∼10\u202fm deep) and 11.1\u202f±\u202f0.5 years for the lower gallery (∼25\u202fm deep). For the upper gallery where 14C measurements from a modern stalagmite are available, the tritium age is in excellent agreement with the time lag between the start of the bomb 14C peak in the atmosphere and in the stalagmite carbonate. In spite of the shallow depth of Villars Cave, the infiltration time is relatively high, resulting in a substantial dampening of the seasonal to annual isotopic variations. As a consequence, Villars Cave speleothems will archive climate variability at the multi-decadal to centennial and millennial scale.