Overview

Project Highlights:

  • Application of cutting-edge biomarker methods to provide new insights into Late Quaternary palaeohydrological change in southern Africa
  • Utilisation and development of a novel desert palaeoenvironmental archive; the communal latrines of the rock hyrax
  • Fieldwork in the deserts of southern Africa supported by a large and established research group focused on African palaeoclimates

 

Overview

The sub-tropics of Africa responded sensitively to Pleistocene glacial-interglacial climatic change, as evidenced by the formation of palaeo-lakes and the activity of now relict dune systems. However, the timing, precise climatic drivers and specific environmental responses to such global-scale forcings are far more difficult to decipher. This reflects long-standing problems concerning: a) a paucity of Pleistocene sedimentary archives, particularly in the most arid regions and b) the climatic ambiguity of existing proxy environmental evidence. In this respect, the analysis of the communal latrines of the rock hyrax (Procavia capensis) has opened up a whole new suite of potential avenues for palaeoenvironmental research in Africa (Chase et al., 2012; Chase et al. 2017). These stratified deposits of dried urine and faecal matter can be >70,000 years old, preserve remarkably high-resolution records (often centennial-scale and far better than most regional sedimentary archives) and host a diverse range of microfossil & geochemical proxies. In particular, they have been shown to preserve abundant plant biomarkers and animal dietary markers. Plant leaf waxes in particular are environmentally sensitive, both in terms of their composition (Carr et al., 2014) and their δ13C and δD stable isotope compositions (Herrmann et al., 2017). This project will focus largely on the use of compound-specific stable hydrogen (δD) isotope analyses of leaf waxes as a means to provide the first spatially extensive, systematically sampled terrestrial palaeohydrological archives from southern Africa. These data will provide critical new insights into hydro-climatic conditions and the synoptic-scale drivers of southern African palaeoclimate. Leaf wax δD data from marine archives adjacent to the continent (e.g. Collins et al., 2014) demonstrate the potential of this proxy, but hyrax middens will facilitate analyses at far higher temporal and spatial resolutions, allowing us to address more specific questions concerning the precise drivers of long-term hydrological change across southern Africa (e.g. Chase et al. 2017). The project will also focus on: 1) refining (via modern plant/water sampling) the use/interpetations of this method across the summer, winter and year-round rainfall regimes of southern Africa, 2) combining these analysis with leaf wax δ13C data to consider ecological change and resilance in savanna ecosystems and 3) intregration of these data with ongoing (isotope-enabled) climate model-data comparisons.

Figure 1: Top: sampling rock hyrax middens in Spitzkoppe, Namibia. Lower: The complete Holocene nitrogen isotope record derived from laminated midden materials from the same site, illustrating the potential of these records to provide high-resolution climate archives.

Methodology

This project will combine field and laboratory methods. Building on our on-going work, you will work with our extensive archive of sampled / dated hyrax middens, and with contemporary plant materials, obtained (with appropriate sampling design) via new field sampling of soils/plants and our existing archive. The middens will provide the long, high resolution archives from which leaf wax (n-alkane) d13C and dD records will be obtained. Interpretations of leaf wax compositions and isotopic signatures will be refined using the data from modern waxes (e.g. Herrmann et al, 2017), as obtained from your new water/plant/soil environmental sampling campaign. From this, the project will refine our understanding of contemporary climate-eco-physiological controls on leaf wax dD across the varied rainfall regimes of southern Africa. The laboratory methods will include lipid biomarker extractions, GC/MS methods and stable isotope ratio mass spectrometry.

 

Training and Skills

You will attain a high level of competence in cutting-edge analytical techniques, particularly GC/MS and compound-specific stable isotope analysis of plant biomarkers. You will be trained in mass spectrometry and mass spectra interpretation. Analysis of contemporary patterns in leaf waxes and rainfall dD will involve geospatial and multivariate statistical analyses, with opportunities for field experience and associated field sampling design. To complete palaeoclimatic reconstructions you will work with multi-proxy data sets and high-resolution age-depth models using (e.g.) Bayesian modelling approaches. Integration of palaeo-data with isotope-enabled GCM model outputs is a additional avenue, and will be supported by our project collaborator.

 

Timeline

Year 1: Initial training in sample preparation, GC/MS, mass spectrometry and GC-IRMS, working with previously-collected midden and modern plant samples. Planning field sampling campaign for calibration of modern leaf wax dD-climate relations, including arrangements for analysis of contemporary rainfall data.

Year 2: Field sampling in southern Africa, development and presentation of first summer rainfall zone palaeohydrological records. Construction and refinement of modern calibration datasets.

Year 3: Development of first winter rainfall and year-round rainfall palaeohydrological records. Analysis and presentation of contemporary dD iso-scapes, synthesis of late Pleistocene palaeohydrology across regional rainfall zones. Publication of data and presentation at international conferences is anticipated from year 2 onwards.

 

Partners and collaboration (including CASE)

The supervisors, Carr and Boom have very strong track records in southern African palaeoecology, particularly the development of stable isotope/geochemical proxies. Carr has 18 years’ experience researching African palaeoclimate change. Boom directs the state-of-art Leicester isotope facility. The project is co-supervised Dr Brian Chase at the Centre National de la Recherche Scientifique (CNRS), Montpellier, the leading international expert on hyrax middens and African palaeoclimate. The supervisors are part of the wider ERC HYRAX project which involves long-standing collaborations with colleagues in the UK, France, South Africa and Germany; the successful student will be integrated into this research community.

Further Details

Contact: Dr Andy Carr asc18@le.ac.uk