Microbial activity records in Marinoan Snowball Earth postglacial transition layers connecting diamictite with cap carbonate (Otavi Group, NW-Namibia)

Autor(en)

Ildiko Gyollai, Marta Polgari, Krisztian Fintor, Elemer Pal-Molnar, Friedrich Popp, Christian Koeberl

Abstrakt

This study concerns the microbial mat formation in postglacial layers of the Marinoan Snowball Earth glaciation. A high resolu-
tion investigation was carried out on the transition layers of Ghaub to Maieberg Formation (start of Keilberg Member) of the Otavi
Group in NW-Namibia (Neoproterozoic). Macroscopic characterization, optical rock microscopy, XRD mineralogy, Raman spectros-
copy investigations were done and geochemical (major and trace element content) as well as carbonate carbon isotopic data
were collected. Three types of microbial contributions were determined: (1) primary, synsedimentary Fe-rich biomats; (2) secon-
dary biomats from biodegradation of Fe-bearing minerals (pyrite, chlorite); and (3) pseudo-secondary structures coating on clasts.
These microbial mats of iron-oxidizing bacteria consumed iron from different sources, such as hydrothermal solutions or iron-
bearing minerals. On the basis of the morphology of Fe-biomats, and the mineralogical and geochemical signatures, we suggest
that the Marinoan postglacial transition layers (Ghaub-Maieberg boundary) formed under neutral, suboxic conditions in brackish
water at the studied locality.

Organisation(en)

Institut für Geologie, Department für Lithosphärenforschung

Externe Organisation(en)

Eszterházy Károly University of Applied Sciences, University of Szeged, Naturhistorisches Museum Wien (NHM), Universität Wien, Magyar Tudományos Akadémia

Journal

Austrian Journal of Earth Sciences

Band

110

Seiten

4-20

Anzahl der Seiten

17

ISSN

2072-7151

Publikationsdatum

2017

Peer-reviewed

Ja

ÖFOS 2012

105105 Geochemie, 105121 Sedimentologie

Schlagwörter

ASJC Scopus Sachgebiete

Geology, Palaeontology, Stratigraphy

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/96af2b60-bf44-491e-afaa-6fc8c94a9b0e