Rise of atmospheric oxygen

Prof. Ronny Schönberg, Dr. Frantz Ossa Ossa, MSc Lucile Roué, Dr. Benjamin Eickmann, Dr. Mark van Zuilen (IPGP, Paris, France) , Dr. Bertus Smith, Prof. Nic Beukes & Prof. Axel Hofmann (all University Johannesburg, South Africa), Prof. Allan Wilson (University of the Witwatersrand, Johannesburg, South Africa)

The Earth’s ocean-atmosphere system experienced profound changes during the Archean-Proterozoic transition, when oxygen levels rose dramatically during a first Great Oxidation Event (GOE: 2.45 to 2.32 Ga). To better resolve Earth’s oxygenation before the GOE we apply different isotope systems of redox-sensitive elements. Molybdenum concentrations and the Molybdenum isotopic composition of marine sediments like black shales, iron formations and carbonates indeed show distinctive changes during the Archean-Proterozoic transition. However, first changes seem to predate the GOE calling for an earlier “Whiff of oxygen”. Another promising proxy for redox changes in the atmospheric and marine system is Chromium. Deciphering its behaviour and sensitivity in the environment during Earth’s history is one of our major goals. Especially the combination of these different proxies might allow us to set better constraints on the early rise of free oxygen.

  • BSc projects Manuela Benger, Tabea Post & Tobias Renz
  • MSc projects Manuela Benger, Nadine Weimar, Vanessa Sutterer & Niklas Gantert
  • PhD projects Dr. Sümeyya Eroglu & Dr. Florian Kurzweil

Toarcian Anoxic Event (Lower Jurassic)

Prof. Ronny Schönberg, MSc Yunfeng Wang, Dr. Frantz Ossa Ossa

During the early Jurassic, some 200 million years ago, when the supercontinent Pangea started to break up large parts of present day Europe still were dominated by a shallow epicontinental basin. High bio-productivity coupled with no or only limited exchange of water with the open ocean caused anoxic conditions in this basin during the Toarcian (ca. 183-174 million years ago), resulting in the deposition of organic-rich black shales – the “Posidonia Shales”, which are world-famous for their richness in well-preserved fossils. We use geochemical and isotope geochemical tools to investigate changes of the environmental conditions (transition metal redox-potentials, temperature, nutrient fluxes, mixing of water masses, etc.) within this basin during the Toarcian Anoxic Event.

  • BSc Project Mario Saussele
  • MSc Projects Christian Luthardt & Simon-Lukas Schurr

Paleoproterozoic Ocean Biogeochemistry from Modern Analogous Environments

Prof. Ronny Schönberg, Prof. Andreas Kappler, Prof. Harald Strauss (Universität Münster, Germany), MSc Gülüm Albut

Paleoproterozoic was the aftermath era of oxygenation of the atmosphere, known as Great Oxidation Event (2.45 – 2.32 Ga) in which the ocean-atmosphere system of the Earth experienced drastic changes. There is still an ongoing debate about the mode and timing of the GOE and a possible stratification of the ocean at the time. There have been extensive studies on the stable isotopic compositions of the redox sensitive elements such as Fe, S, Cr and Mo on Archean and Paleoproterozoic sedimentary rocks as proxies for environmental conditions of the atmospheric and marine systems during these eras. But what if there are modern environments that resemble the biogeochemical conditions of the Paleoproterozoic? Can we decipher the “puzzle of Paleoproterozoic redox conditions” by investigating these similar environments? Arvadi Spring in Engadine, Switzerland is a possible candidate for such a modern analog with its unique co-existence of dissolved Fe(II), Fe (III) minerals, H2S and sulfate (SO4), resembling the conditions proposed for the Paleoproterozoic ocean. The Arvadi Spring is a natural laboratory to research the mechanisms of interaction between abiotic and biotic systems as well as mineral precipitation through studying inorganic and microbial cycling of Fe and S. The aim of the project is to understand the consequences on the Fe isotopes by inorganic iron oxidation in comparison with bacterial chemolithotrophic (microaerophilic) and phototrophic iron oxidation as well as the reaction of Fe (II) with reduced sulfur and the activities of sulfur metabolizing bacteria in the spring. This will help us unravelling the role of bacteria vs. abiotic oxidation pathways in creating the biogeochemical conditions that persisted during Paleoproterozoic. This project is a close collaboration of Geomicrobiology and Isotope Geochemistry working groups.