Lead Supervisor: Alex Liu, Earth Sciences
Co-supervisor: Neil Davies, Earth Sciences
Brief summary:
How have the planet's smallest animals impacted the Earth's surface over the course of geological history?
Importance of the area of research concerned:
The burrowing activity of benthic organisms has had a profound impact on the fabric, porosity and geochemistry of sediments throughout the Phanerozoic geological record. However, the physical and geochemical impact of meiofaunal burrowers — organisms of ~50–1000 µm in size — on sediments is often critically overlooked. The meiofauna include diverse groups such as animals, bacteria, and protists (e.g. foraminifera and amoebae), and in modern settings they are abundant across many depositional environments, particularly under low oxygen conditions where larger metazoans are excluded.
Reports of fossil meiofaunal activity include the presence of discrete burrows, and cryptobioturbation (the total reworking of sediments with no distinct traces). However, the environmental tolerance, substrate preference, impact on fluid flow through sediments, and response of meiofauna to major environmental perturbations through Earth history remain poorly known. Also unknown is the extent to which meiofaunal organisms engineered ecosystems in deep time.
Project summary :
This project will assess how meiofaunal communities impacted the physical and chemical properties of sediments in deep time, and will address the question of whether their activity was/is necessary to ‘condition’ substrates ready for macro-faunal habitation. Investigation of the extent and distribution of meiofaunal burrows in Triassic and Jurassic mudrocks of the UK will constrain how burrowing intensity varies as a function of fluctuating redox conditions and sediment composition, as well as relative to changes in macroscopic ichnofossil diversity and ichnofabric intensity. The project will explore sections spanning the end Triassic mass extinction, documenting the meiofaunal response to extreme biosphere perturbation. Laboratory aquarium experiments investigating changes to physical and chemical sediment properties imparted by modern meiofaunal activity will provide necessary context.
What will the student do?:
The project will involve fieldwork on the Jurassic Coast of the UK, and will include stratigraphic logging of reference sections, and collection of samples. Samples will be analysed with X-ray Computerised Tomography (CT), and Scanning Electron Microscopy. Digital reconstruction of CT data, combined with geochemical (X-ray fluorescence) and microfacies analysis, will enable investigation of relationships between meiofaunal burrowing, substrate, redox geochemistry and resulting sedimentary fabrics. Measurement of variables including total organic carbon, porosity, microfabric, and clay mineral content in beds exhibiting a full spectrum of meiofaunal activity will enable comparison of burrowed versus non-burrowed substrates. Experimental work will be undertaken using aquaria in the Department of Earth Sciences, Cambridge. The student will lead the design of experimental set-ups to determine the impact of modern meiofaunal organisms on physical and chemical sediment properties. There is scope to expand investigation to other areas of the geological record, including the late Ediacaran-early Cambrian interval.
References - references should provide further reading about the project:
Pemberton, S. G., MacEachern, J. A., Gingras, M. K., & Saunders, T. D. 2008. Biogenic chaos: cryptobioturbation and the work of sedimentologically friendly organisms. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 270, pp. 273-279.
Giere, O. 2009. Meiobenthology, 2nd Edition. Springer, 527 p.
McIlroy, D. 2004. Some ichnological concepts, methodologies, applications and frontiers. Geological Society, London, Special Publications, vol. 228, pp. 3-27.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.