Project highlights

  • Develop new approaches for understanding coastal landscape change over varied timescales along the spectacular coastline of South Africa
  • Application and training in diverse set of geochronological and geophysical methods
  • Co-supervision from an international interdisciplinary research group

Overview

The South African coast is a key region for Neogene and Pleistocene sea level studies (Hearty et al. 2020). Along the Western and Eastern Cape Provinces, thick sequences of cemented coastal deposits form an archive of climatic and landscape change, preserving palaeosols, trace fossils (Helm et al., 2020) and evidence of human occupation (Helm et al., 2018). This project will interrogate these coastal sedimentary archives at two scales:

  1. The timing of onshore dune and shoreline emplacement broadly equates to high interglacial sea-levels (Bateman et al., 2011), with coastal dune formation on the continental shelf during low-stands (Cawthra et al 2018). However, more complex scenarios may exist, particularly in areas accompanied by a narrow coastal shelf. It is likely that variability in the coastal stratigraphic record is imparted by the interplay of (inherited) sediment supply and offshore topography (Carr et al., 2019). We hypothesis that the coastal stratigraphic record, particularly where the shelf is narrow, preserves varied records of landscape change. This is exciting as it offers scope to drill into broader questions of (varied) coastal landscape evolutions via, high-density geochronological sampling and geophysical surveying in this case study region.
  2. Considering contemporary environmental change, the coastline is rapidly eroding due to sea level rise and the relatively soft the Neogene / Pleistocene coastal sediments. We will investigate the potential of luminescence rock surface dating to estimate the timing /rates of surface exposure in coastal cliffs and to date the displacement of blocks from cliffs and shore platforms; the latter include potential storm and tsunami deposits (e.g. Brill et al., 2021). The potential of surface exposure dating methods is still being realised, but this approach – in a region rich in quartz suitable for luminescence methods – may offer novel insights into coastal landscape change, and contribute to better-defining coastal hazards.

This project will employ luminescence dating methods, in conjunction with other surveying techniques, to interrogate of a diversity of coastal landscape processes. The student will focus on the development of the new luminescence dating chronologies at Leicester, in collaboration with researchers from the Council for Geoscience, South Africa.

 

Host

University of Leicester

Theme

  • Dynamic Earth

Supervisors

Project investigator

Co-investigators

  • Dr Hayley Cawthra, Chief Scientist – marine geology. Council for Geoscience, South Africa and African Centre for Coastal Palaeoscience, Nelson Mandela University, South Africa [email protected]
  • Dr Mark Powell, University of Leicester [email protected]

How to apply

Methodology

The student will work closely with South African collaborators to identify new locales preserving ancient dune deposits, particularly along the less-studied Eastern Cape. These will be sampled for luminescence dating in conjunction with offshore seismic surveys, allowing onshore chronologies and stratigraphic data to be integrated with offshore geophysical data, particularly for Cape St. Francis and Algoa Bay.  To consider coastal erosion and boulder emplacement, the student will apply remote sensing and terrestrial laser scanning to (respectively) locate and characterise potential boulder deposits and block fall sites. From this survey, known age samples will be identified for testing and calibration of surface exposure dating methods, following which the first exposure dating of unknown aged deposits will be attempted. These ages will be considered in light of block size/dimensions, location and climatic data to evaluate likely rates/timescales/mechanisms of block detachment and the role (or otherwise) of major storm events.

Training and skills

The student will be fully trained in sample preparation and various analytical methods/approaches for luminescence dating, which will require a good understanding of environmental radioactivity and various numerical and statistical analyses (training to be given). The student will also gain experience of thin section and micro-morphological analysis of dune and shore-face sediments. Together with project partners the student will receive training in, and experience of, field mapping and sampling, terrestrial laser scanning, and analysis and interpretation of offshore geophysical data (including multi-beam bathymetry and sub-bottom profiling).

Partners and collaboration

This project is in collaboration with Dr Hayley Cawthra of the Council for Geoscience (South Africa) and the African Centre for Coastal Palaeoscience, Nelson Mandela University, South Africa. She is an internationally recognised expert on the landscapes, (on and offshore) geology and ecology of the region, The ACCP is a leading institution conducting interdisciplinary research on the evolution of the biota (including early humans) of the mega-diverse south / southeast coasts of South Africa.

Further details

To apply to this project please visit: https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships

Possible timeline

Year 1

Training in OSL sample preparation and basic analyses using existing pilot samples hosted in Leicester. Training in mapping and geophysical survey data analysis. Review of potential sampling locales based on existing and planned surveys, as well as remote sensing analysis of fallen blocks and shore platforms to identify potential surface exposure sampling locales. Initial field reconnaissance and sampling of newly identified.

Year 2

Development /testing of methods/approaches for understanding rock surface dating (identify and sample known age blocks/boulders), major field sampling campaign for palaeo-samples.  Finalising first site summaries from field reconnaissance samples.

Year 3

Finalising luminescence chronologies for key sites, integration with geophysical survey data, publication of chronologies for key sites, synthesis of coast-wide controls on preserved coastal dune stratigraphy, further refinement/testing of rock surface methods, including application to unknown age deposits.

Further reading

Bateman, M.D., Carr, A.S., Holmes, P.J., Dunajko, A., McLaren, S.J., Marker, M.E., Roberts, D.L., Murray-Wallace, C.V., and Bryant, R.G., 2011. ‘The evolution of barrier dune systems: a case study of the Middle-Late Pleistocene Wilderness barrier dunes, South Africa’. Quaternary Science Reviews, 30, pp63–81.

Brill, D., May, S.M., Mhammdi, N., King, G., Lehmann, B., Burow, C., Wolf, D., Zander, A. and Brückner, H., 2021. ‘Evaluating optically stimulated luminescence rock surface exposure dating as a novel approach for reconstructing coastal boulder movement on decadal to centennial timescales’. Earth Surface Dynamics 9, pp.205-234.

Carr, A.S., Bateman, M.D., Cawthra, H.C. and Sealy, J., 2019. First evidence for onshore marine isotope stage 3 aeolianite formation on the southern Cape coastline of South Africa. Marine Geology, 407, pp1-15.

Cawthra, H.C., Jacobs, Z., Compton, J.S., Fisher, E.C., Karkanas, P., and Marean, C.W., 2018. ‘Depositional and sea-level history from MIS 6 (termination II) to MIS3 on the southern continental shelf of South Africa’. Quaternary Science Reviews, 181, pp156–172.

Hearty, P.J., Rovere, A., Sandstrom, M.R., O’Leary, M.J., Roberts, D. and Raymo, M.E. 2020. ‘Pliocene‐Pleistocene stratigraphy and sea‐level estimates, Republic of South Africa with implications for a 400 ppmv CO2 world’. Paleoceanography and Paleoclimatology, 35(7), p.e2019PA003835. https://doi.org/10.1029/2019PA003835

Helm, C.W., Cawthra, H.C., Cowling, R.M., De Vynck, J.C., Lockley, M.G., Marean, C.W., Thesen, G.H. and Venter, J.A. 2020. ‘Pleistocene vertebrate tracksites on the Cape south coast of South Africa and their potential palaeoecological implications’. Quaternary Science Reviews, 235, 105857.

Helm, C.W., McCrea, R.T., Cawthra, H.C., Lockley, M.G., Cowling, R.M., Marean, C.W., Thesen, G.H., Pigeon, T.S. and Hattingh, S., 2018. ‘A new Pleistocene hominin tracksite from the Cape south coast, South Africa’. Scientific Reports 8, pp.1-13.

 

 

COVID-19

The project is field-based, which presents some risk in terms of travel restrictions. It is however supported by local collaborators who can assist with remote field sampling, if necessary. Some pilot luminescence samples are already in the University of Leicester, which the student would be able to work on should initial fieldwork be delayed due to Covid issues. The luminescence lab, which will support the primary method is already a very restricted access room and it has been possible to allow access during the phase one lab returns, not least because many of the analyses are automated, requiring only short visits to reload samples. Thus, while a complete university shut down would be challenging, it has been possible to run some samples when Covid restrictions have been lifted somewhat. Some analyses and interpretations of geophysical and mapping data could be carried out remotely, with support of project partners.