Are the microbes found in non-marine carbonates guilty of causing carbonate precipitation themselves? Or are they innocent bystanders, suffering calcite entombment only because of the physical environments in which they grow up? Martyn Pedley and Mike Rogerson hosted a meeting aimed at answering such questions at Hull University in 2008. The ultimate result is this well-timed collection of 17 papers, mostly from European authors. This book should be useful to those making palaeoenvironmental reconstructions from such tufa (stream, lake and swamp carbonate) and speleothem (cave carbonate) petrography and geochemistry. It could also be of interest to those studying early life and astrobiology, and to petroleum geologists exploring microbial carbonate reservoirs like those of the South Atlantic.
Pedley and Rogerson begin with a brief introduction. In this they remind the reader that tufa and speleothem can be considered as end-members of a continuum reflecting different degrees of biologically and physico-chemically controlled precipitation. This is strongly backed up by Brian Jones, who uses stunning Scanning Electron Microscopy (SEM) imagery to show not all speleothems are devoid of microbes. Bindschedler et al. are equally effective in their use of SEM images to illustrate their case for a fungal origin of calcitic nanofibres. A further highlight for petrographers and artists is a beautifully illustrated paper on Polish and Slovakian tufas by Gradziński.
Overall the reader is given little room to doubt that microbes can and do influence precipitation of non-marine carbonates. For example Dittrich and Sibler implicate cyanobacterial slime in microbial carbonate precipitation, and González-Munoz and others describe biomineralization of bacteria like Myxococcus. The book editors provided two interesting contributions themeselves, both resulting from their experiments growing tufa in laboratory flumes. First they used artificial lighting to simulate night and day, showing the effects photosynthesis has on pH and carbonate precipitation. Further towards the back of the book (presumably for reasons of modesty) are their SEM images of the microbial mats and resulting precipitates. Some of the papers also examine the case for abiotic physico-chemical tufa precipitation, such as the detailed study by Arp et al. of some modern tufa depositing streams in Germany. For those interested in palaeoenvironmental reconstruction, Arenas et al. explore oxygen isotope palaeothermometry using Spanish tufas. Capezzuoli et al. used radiometric dating techniques to examine whether Quaternary tufa deposition was associated with warmer interglacial climates.
At times this book seems more a collection of loosely related articles by authors with overlapping interests than a co-ordinated attack on the subject. A few papers relegated to the back of the book focus on chemistry and deposit morphology of (abiotic) speleothem and hydrothermal travertine. As interetesting as these papers are, they might have fitted the rest of the book better if there was some additional discussion of why these particular precipitates are believed to be (totally?) abiotic. This will no doubt prove to be a useful collection of papers, perhaps accompanied on the shelf by the two recent volumes edited by Alonso-Zarza & Tanner (Reference Alonso-Zarza and Tanner2010a, Reference Alonso-Zarza and Tannerb) which provide nice introductory reviews of ‘carbonates in continental settings’.
