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When the ice melted

During the last decade cryogenic cave carbonates (CCC) emerged as a reliable indicator of glacial processes in caves. Formed during freezing of seepage water in cold cave environments these crystals either form powdery, microscopic aggregates or, if the rate of freezing is exceedingly slow, mm-sized crystals. The latter have so far only been reported from Central European caves and no modern analogue of these coarse crystalline CCC forms is currently known.

Last year´s field work in both the Swiss and the Austrian Alps now suggests, however, that very recently deglaciated ice caves may hold the key to better understand the mechanisms of CCC formation.

A cave site in the Sanetsch region of western Switzerland revealed these crystals in a chamber that is still partly ice-filled. U-Th dates rank them as the most recent coarse crystalline CCCs reported so far worldwide and underscore the potential of these crystals aggregates to constrain the timing of permafrost thawing episodes. See recent publication here.

A second site was discovered in the Zillertal Alps of Austria. A recently deglaciated high-Alpine cave yielded patches of CCCs each showing a distinct isotopic composition and a range of crystal morphologies. See recent publication here.

Photo credit: Robbie Shone