BACTERIA-INDUCED CARBONATE DEGRADATION - A TAPHONOMIC CASE-STUDY OF CIBICIDES LOBATULUS FROM A HIGH-BOREAL CARBONATE SETTING

The process of bacterial degradation of skeletal-binding organic matte r forces selective carbonate dissolution in aerobic and turbulent coar se-grained environments. This is demonstrated in a Scanning Electron. Microscope study on the benthic foraminifer Cibicides lobatulus from a coastal platform in northern Norway. High CO2 partial pressures are c reated by rod-shaped bacteria colonies under the protective extracellu lar polymer surface (EPS) film. The impact of degradative bacteria on biogenic carbonates is strongly controlled by a) the microstructural c omposition. of the infested particles, and b) the distribution and Sup ply of organic compounds on and within the skeletal construction. Both factors have strong influences on. variations in rates of decay, bias ing fossil preservation. In aerobic systems, carbonate dissolution may be regarded as a metabolic by-product through bacterial-induced decom position of skeletal-binding organic matter. This study supports the i ncreasing amount of evidence pointing to carbonate dissolution and mac eration phenomena from shelf environments, especially from cold sea en vironments: and stresses microbial input in early diagenesis.