Journal of Paleolimnology

, Volume 50, Issue 3, pp 275–291

Origin and significance of diagenetic concretions in sediments of Laguna Potrok Aike, southern Argentina

Authors

    • Section of Earth and Environmental SciencesUniversity of Geneva
  • D. Ariztegui
    • Section of Earth and Environmental SciencesUniversity of Geneva
  • A. S. De Coninck
    • Water Earth Environment CenterNational Institute of Scientific Research
  • A. Lücke
    • Institute of Bio- and Geosciences IBG- 3: AgrosphereResearch Center Jülich
  • C. Mayr
    • Institute of GeographyUniversity of Erlangen-Nürnberg
    • Geobio-Center and Department of Earth and Environmental SciencesUniversity of Munich
  • C. J. Schubert
    • Department of Surface Waters-Research and ManagementEawag, Swiss Federal Institute of Aquatic Science and Technology
  • The PASADO Scientific Team
Original Paper

DOI: 10.1007/s10933-013-9723-9

Cite this article as:
Vuillemin, A., Ariztegui, D., De Coninck, A.S. et al. J Paleolimnol (2013) 50: 275. doi:10.1007/s10933-013-9723-9

Abstract

Authigenic minerals can form in the water column and sediments of lakes, either abiotically or mediated by biological activity. Such minerals have been used as paleosalinity and paleoproductivity indicators and reflect trophic state and early diagenetic conditions. They are also considered potential indicators of past and perhaps ongoing microbial activity within sediments. Authigenic concretions, including vivianite, were described in late glacial sediments of Laguna Potrok Aike, a maar lake in southernmost Argentina. Occurrence of iron phosphate implies specific phosphorus sorption behavior and a reducing environment, with methane present. Because organic matter content in these sediments was generally low during glacial times, there must have been alternative sources of phosphorus and biogenic methane. Identifying these sources can help define past trophic state of the lake and diagenetic processes in the sediments. We used scanning electron microscopy, phosphorus speciation in bulk sediment, pore water analyses, in situ ATP measurements, microbial cell counts, and measurements of methane content and its carbon isotope composition (δ13CCH4) to identify components of and processes in the sediment. The multiple approaches indicated that volcanic materials in the catchment are important suppliers of iron, sulfur and phosphorus. These elements influence primary productivity and play a role in microbial metabolism during early diagenesis. Authigenic processes led to the formation of pyrite framboids and revealed sulfate reduction. Anaerobic oxidation of methane and shifts in pore water ion concentration indicated microbial influence with depth. This study documents the presence of active microbes within the sediments and their relationship to changing environmental conditions. It also illustrates the substantial role played by microbes in the formation of Laguna Potrok Aike concretions. Thus, authigenic minerals can be used as biosignatures in these late Pleistocene maar sediments.

Keywords

Authigenic mineralsMicrobial reductionMethanogenesisVivianiteFramboidsICDP-project PASADO

Supplementary material

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Supplementary material 1 (JPEG 21268 kb)
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Supplementary material 2 (JPEG 3626 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2013