Project highlights

  • Unpick the controls on Pleistocene coastal landscape change along the spectacular Western and Eastern Cape Province coastlines of South Africa
  • Application and training in diverse set of geochronological and geophysical methods
  • Co-supervision from an internationally leading interdisciplinary research group

Overview

The tectonically stable and ‘far-field’ South African coast preserves an impressive record of Plio-Pleistocene landscape change and represents a key region for Neogene and Pleistocene sea level studies (Hearty et al. 2020). Within the Cape Floristic Region (CFR) in the Western and Eastern Cape Provinces, cemented coastal dunes form impressive sequences that preserve evidence for wider palaeoenvironments via buried palaeosols, fossils and trace fossil animal trackways (Helm et al., 2020). This palaeoscape is referred to as the Palaeo-Agulhas Plain (Marean et al. 2014). The timing of onshore dune and shoreline emplacement in many locations broadly equates to interglacial sea-level highstands (Bateman et al., 2011), with coastal dune formation tracking the coastline onto the continental shelf during low stands (e.g. Marine Isotope stage (MIS) 4 and 6; Cawthra et al 2018).

However, recent research proposes more complex scenarios, particularly in areas – in contrast to the studies associated with the wide Agulhas Bank to the west – accompanied by a narrow coastal shelf. A recent study of the Robberg Peninsula (Figure 1) argued that the preserved coastal dune record reflects the subtle interplay of fluvial sediment supply, offshore and onshore topography and antecedent (inherited) offshore sediment sources. This resulted in a stratigraphic record very different to elsewhere on the coastline (Carr et al., 2019). It potentially implies that the peri-coastal stratigraphic record east of the Agulhas Bank, where the shelf is greatly narrowed, may preserve much more varied records of landscape change. This is exciting as it indicates scope to drill more deeply into long-term coastal landscape responses via focused, high density geochronological sampling and geophysical analyses.

This project seeks to investigate complex scenarios of Pleistocene coastal evolution within the Palaeo-Agulhas Plain. It will build a new suite of geochronological data to be integrated with offshore geophysical survey data and potentially offshore sampling methods. The goal is to build a fuller sense of the local vs. regional controls on the Pleistocene coastal stratigraphic record.  The student will focus particularly on the development of new optically stimulated luminescence (OSL) dating chronologies, in collaboration with researchers from the African Centre for Coastal Palaeoscience (ACCP).

 

Host

University of Leicester

Theme

  • Dynamic Earth

Supervisors

Project investigator

  • Andrew Carr, University of Leicester

 

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
  • Dr Mark Powell, University of Leicester

How to apply

Methodology

The student will work closely with the team from the ACCP to identify new locales preserving ancient dune deposits, largely along the less studied eastern Palaeo-Agulhas Plain. The primary focus of the student’s work will be to identify, field map and sample onshore coastal dune sediments for optically stimulated luminescence dating. While the basic quartz luminescence method is established for this region, two new aspects will be pursued; 1) routine refinement of environment dose rate estimation via analysis of the cementation and diagenesis of the dunes and 2) testing and applying potassium feldspar luminescence methods to extend the reliable dating range beyond marine isotope stage 7 (~200 ka). The student will also work with the ACCP team to integrate onshore chronologies and stratigraphic data with offshore geophysical data and seamless onshore-offshore profiles from Cape St. Francis and Algoa Bay.

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 shoreface sediments. Together with project partners the student will also receive training in, and experience of, field mapping and sampling, analysis and interpretation of offshore geophysical data (including multibeam bathymetry and sub-bottom profiling)

 

Partners and collaboration

This project is in collaboration colleagues at the ACCP, Nelson Mandela University (South Africa); viz Drs Hayley Cawthra and Jan De Vynck, and Professor Curtis Marean. The former are leading experts on the landscapes, (on and offshore) geology and ecology of the region, while the latter is an internationally renowned archaeologist whose work focuses on the role of this coastal region in the evolution of modern humans. 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 Andy Carr asc18@le.ac.uk

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. Initial field reconnaissance and sampling of newly identified sites, collection of test samples for feldspar methods (older dune samples).

Year 2

Development of methods/approaches for understanding dose rate evolution in coastal dune sediments (from micro-morphological analyses), major field sampling campaign, testing of feldspar methods to extend dating age range.  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 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.

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.

Marean, C.W., Cawthra, H.C., Cowling, R.M., Esler, K.J., Fisher, E.C., Milewski, A., Potts, A.J., Singels, E., De Vynck, J., 2014. Stone Age People in a Changing South African Greater Cape Floristic Region, In: Allsopp, N., Colville, J.F., Verboom, T. (Eds.) Ecology and Evolution of Fynbos:  Understanding Megadiversity. Oxford University Press, Oxford, 164-199.

COVID-19

The project is field-based, which presents some risk in terms of travel restrictions. It is however supported by a team at the ACCP 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 on-going 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.