Relict Pleistocene calcareous tufa of the Chlupáčova sluj Cave, the Bohemian Karst, Czech Republic: A petrographic and geochemical record of hydrologically-driven cave evolution

The tufas of the presently shallow Chlupáčova sluj Cave document an unusual history of deeper to shallower hydrologic processes in cave evolution. The wider geological context of the cave, along with fluid inclusion and stable isotope (C and O) analyses of calcite from tectonic veins cutting through its wallrock, are evidence of the origin of the cave in the deeper subsurface, under the influence of ascending 25–70 °C warm, saline (2.0–22.3 wt% eq. NaCl) waters driven by regional hypogene processes. The formation of calcite veins, which occurred at 700–400 ka, was probably coeval with the early stages of cave development. However, two generations of tufa formed in the later Pleistocene during the mature shallow-subsurface stage of cave development when daylight and cold meteoric waters penetrated the cave through ceiling windows and tectonic fractures.