Overview

Floodplains are key environments in the evolutionary history of life on Earth. They record the first freshwater invasions of arthropods, molluscs and vertebrates, and these environments were key habitats for the terrestrialisation of tetrapods. Late Palaeozoic floodplain sedimentary rocks preserve rich faunal and floral evidence of changes in late Palaeozoic vegetation that represent important stages in the evolution of terrestrial ecosystems. This PhD is particularly novel because it will explore and integrate evidence from sedimentology, micropalaeontology and palynology to develop a new, more holistic picture of the dynamics of these ecosystems. This research will reconstruct the ecology and sedimentology of floodplains through the late Devonian to mid-Carboniferous.

The project will initially investigate the Early Carboniferous Ballagan Formation, using a combination of rock cores and exposures in the UK. The Ballagan Formation is famous for its rare tetrapod record preserved in floodplain sediments (Smithson et al. 2012, Bennett et al. 2015).

Four types of palaeosols have been identified: entisols, vertisols (Fig. 1), inceptisols and gleysols. These represent a range of environments from waterlogged marsh, to scant, shrubby vegetation, to forested regions. The palaeosols are associated with laminated siltstones and siltstones with intraclasts representing deposition in floodplain lakes and pools, and from localised floods. Preliminary results indicate the rocks contain a rich fauna of fish (actinopterygians, rhizodonts, lungfish, chondrichthyans), tetrapods, bivalves, ostracods and arthropods. This project will be the first detailed investigation of the micropalaeontology and palynology of the floodplain sediments.

The scope of the project will then expand to investigate floodplains in the late Devonian of Pennsylvania, USA (Cressler et al. 2010) and the Pennsylvanian of Nova Scotia (Davies and Gibling 2003). This broader approach will enable the reconstruction of changing vegetation and associated sedimentary environments and habitats through time. The project will test the hypothesis that the timing of freshwater radiations by fish and invertebrates (Gray 1988) was linked to the creation to new terrestrial environments.

Students require a strong background in the geological sciences. We will be seeking enthusiasm for sedimentological fieldwork, working in a laboratory, undertaking microscope work and trying to understand complex data.

An early Carboniferous palaesol (vertisol) indicative of a forested floodplain

Methodology

The project will use detailed sedimentary logging and sampling of floodplain successions that include diferente types of palaeosol from selected sites across the UK, in the US and in Canada using field exposures and core. A range of imaging techniques (e.g. optical microscopy, CT, SEM) will be used to understand the sedimentology and stable isotope analyses will be applied as part of the palaeosol analysis. Quantitative micropalaeontological and palynological processing and interpretation will be undertaken on closely spaced samples through these floodplain successions.

Training and Skills

CENTA students benefit from 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes. 

The student will receive training in sedimentological logging field sampling and in laboratory-based lithological analysis techniques using optical microscopy and the Scanning Electron Microscope (SEM). Training in techniques for micropaleontological and palynological processing will be provided. Some isotope analyses will be undertaken as part of the palaeosol analysis.

The student will join a dynamic group working on a range of palaeoenvironmental research projects.

Timeline

Year 1: Sedimentological study and sampling of core and outcrop. Thin section analysis of selected samples will be undertaken alongside microfossil and palynological processing and analysis. Presentation of preliminary results at a national conference. Drafting of papers for peer-reviewed journals.

Year 2: Study of field sections at Red Hill, Pennsylvania and Joggins Fossil Cliffs, Nova Scotia, Canada, including microfossil and palynological processing.

Year 3:Data analysis, interpretation and thesis writing. Presentation of results at an international conference (e.g. American Geophysical Union).

Partners and collaboration (including CASE)

At Leicester, Sarah Davies (Professor of Sedimentology) focuses on the evolution of ancient depositional environments spatially and through time, with particular emphasis on fine-grained records from the Carboniferous. Carys Bennett is a sedimentologist and microplaleontologist, primarily working in the Palaeozoic. Tom Harvey‘s research uses small carbonaceous fossils to obtain a high-resolution data on broader-scale patterns and processes of evolution. The student will be co-supervised by Timothy Kearsey from the British Geological Survey, who has specific expertise in Palaeozoic-Mesozoic palaeosols and their use as climatic indicators and John Marshall (Professor of Earth Science) at the University of Southampton whose recent research has focussed on understanding Mid-Late Palaeozoic biotic events and palaeoclimates.

Further Details

For further information, please contact Prof. Sarah Davies, University of Leicester, sjd27@le.ac.uk