Cyanobacterially deposited speleothems: Subaerial stromatolites

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Abstract
Stalagmites, which appear to be deposited by cyanobacterial action, have been identified in two caves in New South Wales (Australia). These have a characteristic morphology, which has given rise to local names likening them to crustaceans. We have studied these speleothems, and the cyanobacteria covering them, by microscopic and chemical techniques. Both calcite precipitation and aeolian sediment trapping are involved in their deposition, which is strongly controlled by environmental conditions. They can be regarded as stromatolites within currently accepted definitions of the term.