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How did the first animals and plants change our planet?

Dr Benjamin Mills (SEE), Prof Simon Poulton (SEE), Dr Rob Newton (SEE)

Project partner(s): Dr Daniel Condon (BGS)

Contact email: b.mills@leeds.ac.uk

Summary

This project aims to understand the changes in Earth’s surface conditions during the Paleozoic era, which saw the evolution of land plants and the rapid diversification of animal life. Specifically we will focus on proposed large shifts in atmospheric CO2 and O2 concentrations, which have been linked to the evolution of the terrestrial and marine biospheres and their effects on the delivery and cycling of the key limiting nutrient phosphate [Lenton et al., 2016; Mills et al., 2018; Van de Velde et al., 2018]. This will be achieved using a combination of state-of-the-art geochemical analyses of ancient sedimentary rocks and the application of mathematical ‘Earth System’ models, with the potential for targeted fieldwork to collect additional samples covering specific periods of interest. The balance between laboratory work and computer modelling is flexible depending on the skills of the candidate.

The following key questions will guide the research:

1) Did changes in global phosphorus cycling accompany the expansion of the terrestrial and marine biospheres in the Paleozoic? 

2) What were the dynamics of deep ocean oxygenation throughout the Cambrian, Ordovician and Silurian periods?

3) Did the initial expansion of plant and animal species drive long term climate shifts, or can these be attributed to tectonic or geomorphological factors? 

An initial focus of the project will be the sampling of excellently preserved continuous drill core sections held by the British Geological Survey. Laboratory measurements of the speciation of iron and phosphorus will provide unprecedented insight into ocean redox conditions and marine nutrient cycling. These analyses will be combined with bulk element analyses and isotopic ratios of carbon and sulphur, which respond to changes in global tectonic processes, weathering and biogeochemical cycling. Some of these techniques have been developed by the project team, and research at Leeds will be carried out in the modern and well-equipped Cohen Geochemistry Laboratories within the School of Earth and Environment. There will be opportunities to visit field sites and collect additional carbonate and black shale samples as the project progresses.

The second focus of the project is Earth system computer modelling. Long-term biogeochemical ‘box’ models link the global cycles of carbon, sulphur, oxygen and phosphorus (among others) to reconstruct long term climate [e.g. Figure 2]. The University of Leeds is a leading institution in the development of these models and the researcher will work to improve the ongoing modelling efforts of the project team [e.g. Mills et al., 2016; Van de Velde et al., 2018; Krause et al., 2018] by investigating more detailed ocean modelling [e.g. Wallman, 2003; Clarkson et al., 2015] and new functions representing the evolving global biota [Lenton et al., 2016].  

The question of the ability of life to alter and regulate climate on a global scale is a top priority in the Earth sciences, and papers on this subject appear regularly in top geoscience journals, as well as leading interdisciplinary publications such as Science and Nature. All of the project team, and several of our previous PhD students, are active researchers who publish in the most prestigious journals. Moreover, the field of Earth systems science is relatively new, and many topics remain unaddressed. This project will not only provide an excellent suite of geochemical data for an exciting period in Earth history, it will directly address some of the key questions in the field that are also of interest to the general public. We therefore expect the impact of this project to be highly significant within the scientific community and beyond.

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Related undergraduate subjects:

  • Applied mathematics
  • Astronomy
  • Atmospheric science
  • Chemistry
  • Computer science
  • Computing
  • Earth science
  • Earth system science
  • Environmental science
  • Geochemistry
  • Geography
  • Geological science
  • Geology
  • Geophysical science
  • Geophysics
  • Geoscience
  • Hydrology
  • Mathematics
  • Meteorology
  • Natural sciences
  • Oceanography
  • Physical geography
  • Physical science
  • Physics