Overview

The sub-tropics of Africa are long-recognised to have responded sensitively to Pleistocene glacial-interglacial climatic change, evidenced in the formation of palaeo-lakes and the activity of now relict dune systems (Thomas and Burrough, 2012). However, the timing, drivers and specific environmental responses to such climatic changes are far more difficult to decipher. This reflects a long-standing problem concerning a paucity of Pleistocene sedimentary archives, particularly in arid regions. In this respect, the analysis of the communal latrines of the rock hyrax (Procavia capensis) has opened novel avenues for palaeoenvironmental research in southern 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 - better than most regional sedimentary archives) and host a diverse range of micro-fossil & geochemical proxy data. They have been shown to preserve abundant plant biomarkers and animal dietary markers. Plant leaf waxes in particular are environmentally sensitive proxies, both in terms of their overall composition (Carr et al., 2014) and their compound-specific (δ13C and δD) stable isotope composition (Herrmann et al., 2017). This project will focus on the use of compound-specific stable hydrogen (δD) isotope measurements as a means of providing 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 the application of this approach at far higher temporal-spatial resolutions, providing unique insights into the complex drivers of hydrological change in southern African desert regions (see Chase et al. 2017). The project will focus on refining (via modern plant/water sampling) and applying this method across the summer, winter and year-round rainfall regimes of the southern African sub-continent. It will combine these analysis with leaf wax δ13C data to further-refine our understanding of regional ecological change. Ultimately, the data will contribute to ongoing climate model-data comparisons for this region.

 

Sampling rock hyrax middens in Namibia (top) and a Holocene nitrogen isotope record from Spitzkoppe, Namibia (bottom).

Methodology

Building on on-going work, this project will use our extensive archive of sampled and dated hyrax middens from across southern Africa. The middens range from modern to nearly 70,000 years old and will provide the archives necessary to develop long, high resolution leaf wax d13C and dD records of palaeoclimatic change, which can be integrated with other proxies and existing reconstructions from these archives (Figure 1).

Initial data from modern leaf waxes (Herrmann et al, 2017) demonstrate good correlations between contemporary climate and leaf wax dD. Building on this, this project will further-refine our understanding of contemporary climate-eco-physiological controls on leaf wax dD through an additional modern water/plant/soil environmental sampling campaign and use these findings to support new records extracted from hyrax middens.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10-day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. You will attain a high level of competence in cutting-edge analytical techniques at the Leicester Environmental Stable Isotope Laboratory. These will include GC/MS and compound-specific stable isotope analysis  of 13C and D from plant biomarkers. You will be trained in mass spectrometry and mass spectra interpretation. Analysis of contemporary patterns in modern leaf waxes and rainfall dD will involve various geospatial and multivariate statistical analyses, and include opportunities for field experience and field sampling design. To complete your climatic reconstructions, you will work with multi-proxy data sets and in the development of high-resolution age-depth models using (e.g.) Bayesian modelling approaches.

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)

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