Bacteriogenic iron oxides as an evidence of hydrothermal vent activity : case study from the Polish part of the Silesian Nappe and Tatra Massif

Ferruginous (i.e. ferrous oxides/hydroxides) coatings occurring in the Upper Albian– Cenomanian marine sediments of the Carpathians, represent the occurrence of Iron Related Bacteria. The singular grain coatings consist of densely packed elongated capsules of 5 μm width, with a wall thickness of 0.1 μm. These structures are remnants of the original bacterial sheath. The chemical composition of the capsules and their morphology show that they may be representatives of the Sphaerotilus–Leptothrix group, living recently around low-temperature hydrothermal vents. Such vents are interpreted as the source of metals for bottom sediments in the Silesian Basin (Outer Carpathians) and most probably in the Tatric Basin (Inner Carpathians), too.