Do Microbial
Processes Control CaCO3 Crystal Morphology?
DeChoudens, Vionette1,
Jennifer Roberts1, Luis A. Gonzalez1 (1)
Alleged morphological differences between
calcium carbonate crystals produced by microbial activity and those grown abiotically have been used by several researchers to
identify the presence of microbial processes in the rock record. Although
published data have demonstrated that microorganisms isolated from caves and
other environments can influence the production of calcium carbonate through
their metabolic activity; the resulting crystal morphologies are not exclusive
to microbially influenced precipitation and should
not be used as the sole indicator of microbial presence. Recent experimental
work that simulates speleothem growth under sterile
conditions has produced crystal morphologies similar to those attributed to
microbial activity and those commonly found in cave speleothems.
The results from this work indicate that most calcium carbonate speleothem growth may occur as a result of abiotic precipitation processes because CaCO3
crystals lack definite diagnostic indicators for microbially
influenced precipitation. Microbes, however, do live in these environments and
might contribute to speleothem formation when their
metabolic activity surpasses the effects of abiotic supersaturation and precipitation. Additional experimental
and empirical research is needed to determine the specific impact of
microorganisms on speleothem growth as this can serve
to elucidate their preservation or recognition in the rock record.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California