From hypogenic to biogenic speleogenesis in semi-arid climate: Bat guano-driven carbonate weathering and cave modification in Chariton Cave, Israel

Guano-related weathering in caves received notable attention in several studies over the last decades. This study investigates the influence of bat guano on the development of Chariton Cave, the largest known hypogenic cave in Israel. We examine the cave morphology, sediments, and moisture sources to understand post-speleogenetic processes in a vadose environment. Apatite deposits along cave passages with keyhole cross-sections suggest secondary enlargement by guano-induced weathering. Estimation of the guano-related weathering suggests it accounts for at least 30 % of the entire cave volume. This significant weathering occurs in semi-arid conditions, with limited infiltration of meteoric water from the surface. However, condensation-evaporation cycles within the cave provide the moisture required for weathering associated with guano. U[sbnd]Pb dating of calcite, which was deposited on secondary apatite, indicates bat activity in the cave since at least 5.19 ± 0.85 Ma. This age enables calculation of maximum guano-related weathering rate of ~0.05 to ~0.07 mm/ka and maximum incision rate in Chariton canyon of 19.2 mm/ky. Furthermore, ¹⁴C dating of guano shows bat activity and guano accumulation 3360–3620 years ago, which continues to the present. This research highlights the importance of biogenic processes in reshaping hypogenic caves after their disconnection from formative environments, contributing to our understanding of karst evolution.