10.11588/data/TMYLWSRitter, SimonSimonRitter0000-0002-1152-8754Institute of Earth Sciences, Heidelberg UniversityUnravelling the formation of Hells Bells: underwater speleothems from the Yucatán Peninsula [Data]Hrydrogeochemistry and aquifer monitoring of deep stratified cenotes from the Yucatán Peninsula, MexicoheiDATA2019Earth and Environmental SciencesRitter, SimonSimonRitterInstitute of Earth Sciences, Heidelberg University2019-12-1640134492332527811676046820370081817022text/tab-separated-valuestext/tab-separated-valuestext/tab-separated-valuestext/tab-separated-valuestext/tab-separated-valuestext/tab-separated-values2.0Hells Bells are unique bell-shaped underwater speleothems recently discovered in deep meromictic sinkholes (cenotes) on the Yucatán Peninsula, Mexico. In order to unravel the underwater growth of Hells Bells and identify the mechanism of subaqueous calcite precipita-tion, several deep meromictic cenotes with and without Hells Bells were investigated. Compre-hensive hydro-, bio- and geochemical analyses of the water bodies and Hells Bells specimens including stable carbon isotope analyses, petrographic examination, U series age-dating, aqui-fer monitoring and microbiological investigations, resulted in a consistent hypothesis on Hells Bells formation. The subaqueous authigenic calcite precipitation in cenotes with Hells Bells is most likely promoted by biogeochemical processes within the narrow 1–2 m thick pelagic re-doxcline immediately above the halocline. Chemolithoautotrophy and incomplete microbial oxidation of sulfide to zero-valent sulfur via proton-consuming sulfide oxidation were identi-fied as dominant biogeochemical processes within the redoxcline. Both processes favor authi-genic calcite precipitation by increasing the pH of the surrounding water. A low degree of con-vection within the water body is identified as crucial hydrogeological prerequisite for the devel-opment of pelagic redoxclines, in which biogeochemical conditions favoring calcite precipita-tion prevail. Furthermore, in order to preserve the authigenic calcite formed in the redoxcline and build Hells Bells, a dynamic elevation of the halocline is hypothesized. Suitable conditions for Hells Bells formation are likely to be encountered in other deep stratified cenotes on the Yucatán Peninsula that are so far unexplored or unrecognized. Age-dating indicates that Hells Bells growth is an ongoing process covering the present to previous interglacial phases from ~0.1 12.5 and ~90–120 ka BP, respectively, outlasting aerial exposure during glacial sea level low stands. Eventually, isotope-geochemical and age-dating analyses reveal a great potential of Hells Bells as a geoarchive for reconstructing minimum sea level elevations, the development of the Yucatán Karst Aquifer and vegetation changes on the Yucatán Peninsula.