The subglacial speleothem archive

Caves are widespread in the Alps and in some places host dripstones. These calcium carbonate formations are created by seepage water and are a valuable archive of regional climate and environmental change that reaches far into the past. Interestingly, studies have found that the growth of alpine dripstones was not limited to warm climatic periods of the past. The fact that some dripstones have been shown to have grown during glacial periods raises the question of how this was possible, given that the temperature of alpine caves today is often only just above freezing. The hypothesis that will be tested in this research project is that dripstone growth in cold periods is in principle possible where an alpine cave system is covered by a temperate glacier and finely distributed iron sulfide minerals occur in the surrounding rock. The temperate glacier keeps the bedrock "warm", so to speak, and the sulfide minerals, as they weather, produce acidic solutions that dissolve the rock, creating those mineralized seeps from which dripstones can crystallize. The first major goal of this project is to elucidate the processes that control dripstone growth in such subglacial caves. To this end, a series of so-called proxies will be applied to demonstrate, for example, that ice but no vegetation existed above the cave during glacial times. The second main goal is the extension of a paleoclimate calendar of the Alps, which was established by our group, beyond the penultimate warm period. Even in the very well studied Alps, there is very little knowledge about this period of recent geological history.