Cryogenic cave carbonates

Abstract

Carbonate minerals formed by the freezing of water in karst caves comprise a unique and special class of speleothems referred to as cryogenic cave carbonates (CCCs). CCCs occur in a variety of shapes and sizes ranging from sub-μm to several cm with two distinguishable endmembers that form as a consequence of the surface area and volume of freezing water bodies and the rate of freezing. Fine and commonly powdery deposits form by rapid freezing of thin water films on ice substrates, often in caves featuring anomalously cold parts due to strong air convection. Conversely, coarser-grained crystals and aggregates precipitate in slowly freezing pools of water in ice bodies at rather stable temperatures slightly below freezing. CCCs of the latter type can be reliably and precisely radiometrically dated back to c. 600,000years, thus in circumstances where a cave is situated in permafrost and cooled via conduction, CCCs can provide a unique archive of long-term changes in permafrost extent and depth spanning multiple glacial-interglacial cycles.