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Overview

Project Highlights:

  • Application of cutting-edge methods to provide entirely new insights into palaeo-hydrology in southern Africa.
  • Utilisation of novel environmental archives (rock hyrax middens).
  • Integration with large and well-established research team focused on African palaeoclimate.

Overview

The arid - sub humid sub-tropics of Africa are long-recognised to have responded sensitively to Pleistocene glacial-interglacial climatic changes, 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 late Pleistocene sedimentary archives, particularly in arid regions. In this respect the analysis of the communal latrines of the rock hyrax (Procavia capensis) has opened entirely new avenues for palaeoenvironmental research in arid southern Africa (Chase et al., 2012). These stratified deposits of dried urine and faecal matter may be >50,000 years old, preserve remarkably high resolution (often centennial-scale and substantially better than many sedimentary archives in this region) records and host a broad range of micro-fossil & geochemical proxy environmental data. They have been shown to preserve abundant plant biomarkers, including dietary markers, as well as plant leaf waxes. The latter are environmentally sensitive, in terms of their overall composition (Carr et al., 2014) and their compound-specific (d13C and dD) stable isotope composition (Herrmann et al.; in review). This project will primarily focus on the use of compound-specific stable hydrogen (dD) isotope measurements as a means to provide the first extensive, systematically sampled terrestrial palaeo-hydrological archives from southern Africa. These data will provide new insights into hydro-climatic conditions and wider (palaeo) climatic drivers for southern Africa. Leaf wax dD data from marine archives adjacent to the continent (e.g. Collins et al., 2014) demonstrate the great potential of this proxy, but hyrax middens will faciliate the application of this cutting edge method at far higher termporal-spatial resolutions, providing unique insights into the underlying mechanisms and impacts of climatic change in African desert regions. The project will focus on applying this method across the major summer, winter and year-round rainfall regimes of the southern African sub-continent, and will combine these analysis with leaf wax d13C analysis to further refine our understanding of regional palaeoecological change.

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 high resolution leaf wax d13C and dD records of palaeoclimatic change, which can be integrated with other proxies from these archives (Figure 1).

Initial data from modern leaf waxes (Herrmann et al, in review) demonstrate good correlations betweeen contemporary climate and leaf wax dD. Using these initial data and newly sampled material this project will also seek to refine our understanding of contemporary climate-eco-physiological controls on leaf wax dD and use these finding 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. The student will attain a high level of competence in several cutting-edge analytical techniques. The work will be carried out in the Environmental Stable Isotope Laboratory in Geography and will include GC/MS (liquid) analysis and compound-specific stable isotope analysis (GC-IRMS for 13C and D). GC/MS work will include training in mass spectrometry and mass spectra interpretation. Analysis of contemporary patterns in modern leaf wax and rainfall dD will involve the use of various multivariate statistical analyses, and include opportunities for field experience and field sampling design. There may be additional opportunities for the application of solid phase micro-extraction (SPME) methods in the characterisation of midden organic materials.

Timeline

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

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

Year 3: Development of winter rainfall and year-round rainfall palaeo-dD records. Analysis contemporary dD isoscapes, synthesis of palaeo-hdrology across regional rainfall zones.

Partners and collaboration (including CASE)

The supervisors Carr and Boom have significant expertise concerning southern African palaoeecological and stable isotope/geochemical methods. Carr is a physical geographer interested in African climate change and Boom is a biogeochemist. The project will be co-supervised Dr Brian Chase at the Centre National de la Recherche Scientifique, Institut des Sciences de l'Evolution-Montpellier, the leading expert on hyrax middens and African palaeoclimate. The supervisors are part of the HYRAX project, which involves collaborations with colleagues elsewhere in the UK, South Africa and Germany; the student will be integrated into this research community.

Further Details

A Carr asc18@le.ac.uk A Boom ab269@le.ac.uk