『Abstract
Calcitic speleothems from a cave located on the north central
coast of Grand Cayman commonly include corrosion surfaces that
developed when calcite precipitation ceased and corrosion mediated
by condensates became the operative process. Dissolution features
associated with these surfaces, including etched crystal surfaces,
microcavities, and solution-widended boundaries between crystals,
are commonly occupied by microbes and microbial mats that have
been replaced by calcium phosphate and/or coated with calcium
phosphate. No mineralized microbes were found in the calcite crystals
that form the speleothems. The morphology of the mineralized hyphae
(eight morphotypes) and spores (nine morphotypes) are indicative
of actinomycetes, a group of microbes that are ideally adapted
to life in oligotrophic cave environs. Superb preservation of
the delicate hyphae, aerial hyphae, and delicate ornamentation
on the hyphae and spores indicate that the microbes underwent
rapid mineralized while close to their original life positions.
Although these actinomycetes were extremely susceptible to replacement
by calcium phosphate, there is no evidence that they directly
or indirectly controlled precipitation. Nevertheless, the association
between the P-rich precipitates and microbes shows that the use
of phosphorus as a proxy for seasonal climate change in paleoclimate
analyses must be treated with caution.
Keywords: Actinomycetes; Phosphates; Speleothems; Microbes』
1. Introduction
2. Setting
3. Methodology
4. Results
4.1. General features of the speleothems
4.2. Microbes
4.2.1. Preservation
4.2.2. Morphotypes
4.2.3. Taxonomic affinities
4.3. Phosphorus-rich precipitates
4.3.1. Distribution
4.3.2. Composition
4.3.3. Distribution
5. Discussion
6. Conclusions
Acknowledgements
References