About the Project
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 test the hypothesis that the timing of freshwater radiations by fish and invertebrates (Gray 1988) was linked to the creation to new terrestrial environments.
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. 2016).
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 a key period of geological time.
Four types of palaeosols have been identified: entisols, vertisols, inceptisols and gleysols (Kearsey et al. 2016). 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 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.
References
Further reading:
Bennett, C.E. Kearsey T.I., Davies S.J., Millward, D., Clack, J.A., Smithson, T.R. & Marshall, J.E.A. 2016. Early Carboniferous sandy siltstones preserve rare vertebrate fossils in seasonal flooding episodes. Sedimentology, DOI: 10.1111/sed.12280
Cressler, W. L., Daeschler, E. B., Slingerland, R., & Peterson, D. A. 2010. Terrestrialization in the Late Devonian: a palaeoecological overview of the Red Hill site, Pennsylvania, USA. Geological Society, London, Special Publications, 339, 111-128.
Davies, S. J., & Gibling, M. R. 2003. Architecture of coastal and alluvial deposits in an extensional basin: the Carboniferous Joggins Formation of eastern Canada. Sedimentology, 50, 415-439.
Gray, J. (1988). Evolution of the freshwater ecosystem: the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology, 62(1), 1-214.
Kearsey, T.I., Bennett, C.E., Millward, D., Davies, S.J., Gowing, Charles J.B., Kemp, S.J., Leng, M.J., Marshall, J.E.A. and Browne, M.A.E. 2016. The terrestrial landscapes of tetrapod evolution in earliest Carboniferous seasonal wetlands of SE Scotland. Palaeogeography Palaeoclimatology Palaeoecology, 457, 52-69. doi:10.1016/j.palaeo.2016.05.033
Smithson, T.R., Wood, S.P., Marshall, J.A.E. & Clack, J.A. 2012. Earliest Carboniferous tetrapod and arthropod faunas from Scotland populate Romer’s Gap. PNAS, 109, 4532-4537.
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