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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 
Brief summary: 
The production of mud and deposition of mudrock is fundamental to how Earth works as a planet - this project will seek to understand the geochemical and petrological attributes of mud, as the chemical weathering factory evolved in deep time, allied to the evolution of land plants.
Importance of the area of research concerned: 
Mudrock is one of the most important and evolutionarily revealing rock types at the Earth's surface, and has acted as both as an archive and a regulator throughout the planet's history. This project hinges on new observation regarding Earth's mudrock record: that there is a massive upsurge in the amount of mudrock preserved in river-deposited sediments at around 400 million years ago. Before this shift, the amount of mudrock in alluvium was typically less than 2% of total sedimentary rock volume, but afterwards mud could account for up to 95% of any given river-deposited succession. This major shift in the nature of the rock record happened only once in Earth history, and occurs at the same time that newly-evolved land plants were beginning their greening of the continents. This research aims to shed further light on this critical evolutionary chapter in Earth history. There was little mud preserved in river systems before plants, so did mud end up washed out into the marine realm, or lakes, or was there just less mud being produced in the first place? Did land plants help to promote chemical weathering and the production of mud?
Project summary : 
This project will link into ongoing research regarding the evolution of mudrock in geological time. Samples of mudrock will be collected and contextualized from a variety of Precambrian to Carboniferous aged rock successions. This project will be particularly focussed on one or more of the characteristics of mudrock through geological time: 1) Petrology: by assessing the mineralogy of samples the project will track changes to the composition of mud through the key interval. 2) Geochemistry: by looking at the isotopic record of the samples, questions can be addressed regarding the intensity of chemical weathering before and after plant evolution.
What will the student do?: 
The student will be involved in the collection and characterization of mudrock samples from selected geological successions in the UK. They will determine weathering intensity on the continents using samples from lacustrine facies with Li isotopes measured on the clay size fraction and the bulk. They will also look at a wider range of specimens, from a petrological standpoint, and these will be processed for XRD and SEM analysis. By the end of the project, the student will have amassed an atlas of mudrock properties from before, during, and after the evolution of land plants, permitting an answer to the long-standing question as to whether the greening of the continents preferentially boosted mudrock production or retention, and refining our understanding of the long term evolution of global geochemical cycles.
References - references should provide further reading about the project: 
McMahon, W.J. and Davies, N.S., 2018. Evolution of alluvial mudrock forced by early land plants. Science, 359(6379), pp.1022-1024.
Zeichner, S.S., Nghiem, J., Lamb, M.P., Takashima, N., de Leeuw, J., Ganti, V. and Fischer, W.W., 2021. Early plant organics increased global terrestrial mud deposition through enhanced flocculation. Science, 371(6528), pp.526-529.
Kalderon-Asael, B., Katchinoff, J.A., Planavsky, N.J., Hood, A.V.S., Dellinger, M., Bellefroid, E.J., Jones, D.S., Hofmann, A., Ossa, F.O., Macdonald, F.A. and Wang, C., 2021. A lithium-isotope perspective on the evolution of carbon and silicon cycles. Nature, 595(7867), pp.394-398.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Dr Edward Thomas Tipper
Dr Oliver Shorttle
Department of Earth Sciences Graduate Administrator
Dr Neil Davies