Lead supervisor: Neil Davies, Earth Sciences
Co-supervisor: Emily Mitchell, Zoology; William McMahon, Earth Sciences; Anthony Shillito, University of Saskatchewan
Brief summary:
The invasion of non-marine habitats by animal life was a complex, protracted process, and recent work has helped identify the timing of colonization by different organisms, with the Devonian period recognised as a key interval. Less well understood are broader questions such as when continental fauna began to comprise unique individuals and exhibit unique behaviours (as opposed to facies-crossing ‘marine invaders’) and the impact that these organisms had on physical sedimentary environments and sediment fabrics, and critical zone processes. This project will involve a forensic analysis of key Middle Devonian sites to address these issues.
Importance of the area of research concerned:
The critical zone is the region of the solid Earth where lithosphere meets biosphere, and its operation involves a complex network of interactions between biological and geological processes, coupled on scales ranging from patches to global and from seconds to millennia. On land, this is most recognisable in the form of soils, where metazoans interact with other life (plants, fungi, etc) and parent rock, occupying deep horizons for stability, or surface horizons for greater environmental variability, opportunities and challenges. We presently lack an informed understanding of how this critical zone developed at the onset of animal life on land, which was absent for the first 90% of Earth history. Such an understanding will impart new perspectives on the complex system that is today a key regulating venue for biodiversity, climate and the hydrosphere. Focussed analysis of key Devonian sites will isolate the timing of novel terrestrial behaviours, recognise how the critical zone expanded as animals occupied increasingly deeper tiers, and identify direct impacts on local physical geomorphology and lithological materials that can be extrapolated to have multiplied into global impacts.
Project summary :
The Devonian is a key interval of terrestrialization and sedimentary rocks of this age are well represented in the region of NW Europe, rendering it a perfect natural laboratory to assess animal impacts in different environments. Three sites act as case studies (North Devon Basin, England; Orcadian Basin, Scotland; Hornelen Basin, Norway) where underexplored records of trace fossils (burrows, trackways, etc) occur in strata deposited in shallow marine, lacustrine, floodplain soil, and alluvial environments. Detailed documentation of the size, diversity and disparity of traces, anchored in a robust sedimentary geological framework and subjected to statistical analyses, will shed light on the Devonian critical zone and identify the role of pioneer animals as ecosystem engineers impacting geomorphology and weathering processes on scales from the local to global.
What will the student do?:
The student will undertake several field seasons at the three sites to map out trace fossil bedding planes and vertical profiles and document the diversity, size and disparity of trace fossils in environments that provide a transect from marine to continental environments, using both sedimentary geological fieldwork techniques and 3d photogrammetry. Ichnofauna unique to different environments will be documented and statistical analysis of facies-crossing forms will be undertaken to assess marine vs. non-marine variability in spatial behaviour, size, density and depth of burrow systems. Original field data from the three sites will be augmented with a comparison of other global ichnofaunas, assembled as a database from pre-existing records. Sedimentary geological data will allow the depth of tiering of burrows to be recognised. Samples will be taken for thin section and scanning electron microscope (SEM) analysis of burrowed profiles to identify variability in clay mineral petrography associated with burrow formation and to recognise microscale impacts on lithology and the material properties of sediment piles.
References - references should provide further reading about the project:
Buatois, L.A., Davies, N.S., Gibling, M.R., Krapovickas, V., Labandeira, C.C., MacNaughton, R.B., Mángano, M.G., Minter, N.J. and Shillito, A.P., 2022. The invasion of the land in deep time: integrating Paleozoic records of paleobiology, ichnology, sedimentology, and geomorphology. Integrative and Comparative Biology, 62(2), pp.297-331.
Genise, J.F., Bedatou, E., Bellosi, E.S., Sarzetti, L.C., Sánchez, M.V. and Krause, J.M., 2016. The Phanerozoic four revolutions and evolution of paleosol ichnofacies. The Trace-Fossil Record of Major Evolutionary Events: Volume 2: Mesozoic and Cenozoic, pp.301-370.
Van Straalen, N.M., 2021. Evolutionary terrestrialization scenarios for soil invertebrates. Pedobiologia, 87, p.150753.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.