Cold Seep Carbonates in the Tertiary of Northwest Italy: Evidence of Bacterial Degradation of Methane

  • P. A. Clari
  • L. Martire


Microbial degradation of methane seeping to the sea floor can result in the precipitation of carbonates, characterized by strongly negative 13C values. Masses of carbonate-rich sediments that crop out within the siliciclastic Oligo-Miocene succession of Monferrato, northwest Italy, are interpreted as ancient records of such a process. Two types of carbonate rock are recognized. The first is a fine-grained, manly limestone characterized by rich assemblages of chemosymbiotic lucinid clams. The second type is barren of fossils and consists of completely lithified mudstones and sandstones. These rocks are carbonate-rich only because of localized, early precipitation of cements in the pores of siliciclastic sediments. Other carbonates, both internal sediments and cements, fill cavities due to burrowing, dissolution of shells and fractures. Direct evidence of bacterial activity is provided by laminated sediment linings of cavities, peloidal textures, and dolomite spheroids with dumbbell-shaped hollow cores.


Debris Flow Carbonate Cement Bacterial Degradation Hollow Core Planktonic Foraminifer 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • P. A. Clari
    • 1
  • L. Martire
    • 1
  1. 1.Dipartimento di Scienze della TerraUniversità degli Studi di TorinoTorinoItaly

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