ASGP (2015), vol. 85: 371–385

EVIDENCE OF BACTERIOGENIC IRON AND MANGANESE OXYHYDROXIDES IN ALBIAN–CENOMANIAN MARINE SEDIMENTS OF THE CARPATHIAN REALM (POLAND)

Marta BĄK (1), Krzysztof BĄK (2), Zbigniew GÓRNY (1, 3) & Beata STOŻEK (3)

1) Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Aleja Adama Mickiewicza 30, 30-059 Kraków, Poland; martabak at agh.edu.pl
2) Institute of Geography, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland; sgbak at cyf-kr.edu.pl
3) Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland

Bąk, M., Bąk, K., Górny, Z. & Stożek, B., 2015. Evidence of bacteriogenic iron and manganese oxyhydroxides in Albian–Cenomanian marine sediments of the Carpathian realm (Poland). Annales Societatis Geologorum Poloniae, 85: 371–385.

Abstract: The Albian and Cenomanian marine sediments of the Silesian and Tatric basins in the Carpathian realm of the Western Tethys contain ferric and ferromanganese oxyhydroxides, visible macroscopically as brown stainings. They coat calcareous bioclasts and mineral clasts, fill pore spaces, or locally form continuous, parallel microlayers, tens of micrometers thick. Light-microscope (LM) and scanning-electron-microscope (SEM) obser- vations show that the coatings contain elongated capsules, approximately 3–5 µm across and enriched in iron and manganese, which may be remnants of the original sheaths of iron-related bacteria (IRB). Moreover, the ferric and ferromanganese staining observed under LM is similar to bacterial structures, resembling the sheaths, filaments and rods formed by present-day bacteria of the Sphaerotilus–Leptothrix group. All of the possible bacteria-like structures are well preserved owing to processes of early diagenetic cementation. If the observed structures are fossil IRB, these organisms could have played an important role in iron and manganese accumulation on the sea floor during Albian–Cenomanian time. The most plausible source of metals for bacterial concentration in the Silesian Basin might have been submarine low-temperature hydrothermal vents, as previously was hypothesized for Cenomanian–Turonian deposits on the basis of geochemical indices.

Manuscript received 6 March 2014, accepted 29 January 2015