Project highlights

  • Develop new approaches for understanding coastal landscape change across multiple 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 (dunes and near-shore deposits) form an archive of climatic and landscape change, as well as preserving numerous 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 long-term 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, variability in the peri-coastal stratigraphic record is imparted by the interplay of (inherited) sediment supply and offshore topography (Carr et al., 2019) and we predict more complex scenarios exist, particularly in areas with a narrower coastal shelf. This is exciting as it offers scope to drill into far broader questions of diverse coastal landscape evolution(s) via, high-density geochronological sampling closely accompanied by targeted geophysical surveying.
  2. Today parts of the coastline are rapidly eroding due to sea level rise and relatively soft Pleistocene coastal sediments. This occurs in the face of burgeoning coastal development. This project will investigate the potential of luminescence rock surface dating methods to estimate the timing and rates coastal cliff erosion and to test the potential to date the displacement of large blocks from cliffs and shore platforms; the latter include potential storm surge and tsunami deposits (e.g. Brill et al., 2021). The potential of surface exposure luminescence dating methods is still being realised, but this approach – in a region rich in quartz with suitable luminescence properties – may offer entirely new insights into shorter-term coastal landscape change, and contribute to better-defining regional coastal hazards.

This project will primarily employ luminescence dating methods, in conjunction with other surveying techniques, to interrogate coastal landscape processes over multiple spatial-temporal scales. 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.

Image showing compilations of dune luminescence ages from the South African south coast.

Caption: Compilations of dune luminescence ages from the South African south coast, showing interglacial-focused dune formation at the well-studied Wilderness embayment (black circles) accompanied by offshore Marine Isotope Stage (MIS) 4 dune formation at Groot Brak (grey squares). These contrast with a potentially new scenario for MIS 3 dune formation at Robberg (white squares).

Two photos

Caption: The “pockets” of MIS 3 dunes (“aeolianite”) at Robberg, preserved within more ancient bedrock structure (from Carr et al., 2019)

Host

University of Leicester

Theme

  • Dynamic Earth

Supervisors

Project investigator

Andrew Carr, University of Leicester ([email protected])

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])
  • Co-I 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 in the less-studied Cape St. Francis and Algoa Bay, Eastern Cape. These will be sampled for luminescence dating in conjunction with targeted geophysical surveys, allowing onshore chronologies and stratigraphic data to be integrated with offshore geophysical data.  To consider a first attempt at quantifying coastal erosion and boulder emplacement, the student will apply remote sensing and terrestrial laser scanning to (respectively) locate and characterise boulder deposits and block fall sites. From this, known age samples will be identified for testing of surface exposure luminescence dating. Following this, first attempts at dating unknown aged deposits will be made. 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

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.

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, geochemistry 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 (assisted by DMP), 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

Contact Andrew Carr for further information – [email protected]

If you wish to apply to the project, applications should include:

  • A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)

Applications to be received by the end of the day on Wednesday 11th January 2023. 

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 sites.

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 first applications to unknown-aged 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, presenting some travel restriction risk. However, it is supported by local collaborators who can assist with remote field sampling. The luminescence lab is a restricted access room and access during the Covid pandemic was possible, partly as many analyses are automated. Some analyses and interpretations of geophysical data could be carried out remotely. In the event of a major pandemic more emphasis could be placed on sampling for the long-term records limiting the more complex / lengthy fieldwork likely required for boulder and cliff collapse dating.