Bacterially Induced Microscale and Nanoscale Carbonate Precipitates

Abstract

Bacteria are able to form carbonate rocks and minerals at all scales, from deposits many meters thick, to distinctive shrubs, to minute crystal forms. They are particularly common in peloids, stromatolites, and hot-water travertines. The peculiar crystal morphologies they produce can be duplicated in the laboratory. Nanobacteria are much smaller forms, spheroids 0.03–0.1 µm in diameter. A quantitative census of nanobacterial bodies in limestones from Holocene to Proterozoic, and in micrite vs ooids vs sparry calcite show that the abundance is enormously variable. In a 4 µm2 area, most samples studied contain between one and 16 bacterial bodies; the median value is about four. Bacteria are significant producers of carbonate deposits.