Function and Responsibilities:

Head of section 3.2 'Organic Geochemistry' at GFZ

Professor of Organic Geochemistry, Universität Potsdam (Inst. of Geosciences & Inst. of Chemistry)

Research Interests:

Christian studies the origin and fate of biological carbon in the Earth system using molecular and isotopic methods at the interface of geology, biology and chemistry. His main focus lies on working towards a holistic understanding of a co-evolving biosphere and its environmental surroundings, as well as their reciprocal interaction throughout Earth history. In particular the processes behind the evolution of progressively more complex life and the formation of a 'modern' Earth system lie at the core of Hallmann's interest.

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Advent of complex life

The emergence of the first animals can be seen as the root of our very own existence, yet the details and drivers of this consequential event are far from understood. We work towards enhanced temporal and spatial constraints for this major transition and aim at a better understanding of environmental conditions. See e.g. Nettersheim et al. (2019).

Evolution of lipid biosynthesis

Terpenoid biosynthetic capabilities have changed in the deep past and environmental (e.g. oxygen, metals) enzyme controls have been suggested. We try to link reliable records of fossil lipids to global environmental change and seek to explore the physiological advantage provided by minuscule membrane lipid adaptations. See e.g. Hoshino et al. (2017).

Earth's earliest biosphere

Exceedingly little is known about the cradle of biology, mostly as a consequence of significant reworking and overprinting of the sedimentary archives containing Earth's oldest organic matter. We explore the quantitative limits of biomarker preservation, search for new biosignatures and attempt to extract remnant biological information from macromolecular organic matter. See e.g. French et al. (2015).

Primary production throughout Earth history

Marine primary production exerts a major control on the carbon cycle, climate and the global oceanic redox state. Understanding the geological succession of primary producers is key to a holistic interpretation of the Earth system. By improving algal records we aim to disentangle the complex interplay of tectonic evolution, ocean chemistry and biological innovation. See e.g. Brocks et al. (2017).

Climate, past and future
Projections of climate change and consequences for marine biogeochemistry can be modelled but rely on understanding analog scenarios in the geological past. We focus on periods of rapid climatic change in the younger and deeper geological past to inform us about details of the change that is coming. See e.g. Feulner et al. (2015).

Career:

• 2012–2021    Max-Planck-Research-Group leader, MPI for Biogeochemistry, Jena, DE.
• 2012–2021    Staff scientist & lecturer, MARUM, University of Bremen, DE.
• 2010–2012    Postdoctoral associate, Massachusetts Institute of Technology, USA.
• 2008–2010    Agouron Institute fellow, Massachusetts Institute of Technology, USA.

Education:

• 2009    PhD in Applied Chemistry, Curtin University, Perth, AU.
• 2005    Diplom in Geology–Paleontology, University of Cologne, DE.
• 1999    Highschool diploma (Abitur), Bernardinus College, Heerlen, NL.

Awards:

Bernd Rendel Prize of the Deutsche Forschungsgemeinschaft (2005)

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> Google scholar Profile (link)

> Paleo-Biogeochemistry at MARUM (link)