Matt Telfer Prof. Dave Thomas Dr Mark Bateman

1. UK Luminescence and ESR meeting 2006, University of Liverpool An OSL-dated palaeoenvironmental record from a pan-lunette complex and the linear dunes at Witpan, southwestern Kalahari Matt Telfer Prof. Dave Thomas Dr Mark Bateman

2. Background Title • Much of the Kalahari landscape is characterised by vegetated linear dunes • These have long been interpreted as evidence of former arid periods • Until the 1990s, the chronology for these landforms was extremely vague

3. Aims and Objectives Title • Extend the aeolian record with coring techniques. • By using a detailed sampling strategy within cores as well as within the locale, investigate the continuity and replicability of dune records. • Consider the implications of the record of aeolian accumulation for the regional palaeoclimatic history of the Late Quaternary.

4. Field site Title • Southwestern Kalahari of the Northern Cape, South Africa

5. 1km Field site Title • Southwestern Kalahari of the Northern Cape, South Africa. • Witpan contains a range of landforms which may act as palaeoenvironmental indicators – a pan-lunette complex set amongst linear dunes.

6. 17 3 10 11 4 1 1 6 4 4 10 1km 3 4 3 4 3 2 14 Field site Title • Southwestern Kalahari of the Northern Cape, South Africa. • Witpan contains a range of landforms which may act as palaeoenvironmental indicators – a pan-lunette complex set amongst linear dunes. • Detailed sampling strategy.

7. 1km Methods Title • 113 samples for OSL dating • Initially, SAR analyses on the 90-150 μm or 180-212 μm HF-etched quartz fraction. • Generally, samples were bright, well-bleached sands showing low inter-aliquot variability.

8. 1km Methods - SGC Title • In view of large number of samples, experiments were conducted with the very rapid Standardized Growth Curve (SGC) methods of Duller and Roberts (2003). • Curve created using large bank of data, pre-analysed by SAR methods. • 4290 dose-response points between 0 – 50 Gy, with an uncertainty of around 5%.

9. 1km Methods - SGC Title Mean ratio = 1.00 ± 0.06 • 23 samples analysed by SAR and independent SGC to test validity of method. • All samples within 1σ errors. The only sample with a SAR/SGC discrepancy of > 10% is around 0.1Gy. • Method shows considerable potential in facilitating the analysis of very large data sets.

10. Lunette dune development Telfer, M.W. and Thomas, D.S.G. (2006) Geology 34, 10, p. 853-856

11. Lunette dune development

12. Lunette/linear dune interactions

13. 0.16 ± 0.02 1.8 ± 0.1 3.5 ± 0.2 5.9 ± 0.4 9.0 ± 0.6 Depth (m) 8.9 ± 0.5 10.2 ± 0.6 9.8 ± 0.6 9.1 ± 0.6 10.0 ± 0.5 9.3 ± 0.6 10.9 ± 0.7 10.8 ± 0.7 10.5 ± 0.7 Age (ka) Linear deposition – intra-core variation Kal 02/7

14. 0.15 ± 0.02 0.16 ± 0.02 3.1 ± 0.3 4.9 ± 0.3 12.2 ± 0.8 Depth (m) 9.4 ± 0.5 10.4 ± 0.6 12.1 ± 0.8 10.1 ± 0.6 12.3 ± 0.7 9.2 ± 0.6 56 ± 3 10.3 ± 0.6 76 ± 8 12.7 ± 0.8 73 ± 7 57 ± 3 72 ± 7 Age (ka) Linear deposition – inter-core variation Kal 04/6 Kal 02/1 5m

15. SW Kalahari linear dune accumulation Stokes et al 1997

16. SW Kalahari linear dune accumulation Stokes et al 1997, Thomas and Shaw 2002, Bateman et al 2003

17. SW Kalahari linear dune accumulation Stokes et al 1997, Thomas and Shaw 2002, Bateman et al 2003, This study

18. Conclusions Title • Much of the lunette is even younger than suspected previously – full-depth (9m) reworking/deposition over the past 1000 years. • The response of the lunette dune itself is subject to the influence of differing sediment supply along its length. • The linear and lunette dunes at Witpan respond in different ways to environmental stimuli. • A major period of linear dune accumulation at Witpan occurred at 10-11ka, although there has been near-continuous low-intensity Holocene deposition. Previous periods of dune activity are recorded in this area.

19. Conclusions  Title • Extend the aeolian record with coring techniques. • … back to c. 100 ka • By using a detailed sampling strategy within cores as well as within the locale, investigate the continuity and replicability of dune records. • … evidence of both rapid and slow accumulation discovered, as well as complex lunette development • Consider the implications of the record of aeolian accumulation for the regional palaeoclimatic history of the Late Quaternary. • … work is ongoing, but a cyclical record does exist, apparently controlled by variations in the strength of the continental atmospheric circulation  ?

20. Implications for further work • The Kalahari’s linear dunes have the potential to record long – albeit discontinuous – sequences of aeolian accumulation. • A highly detailed and rigorous sampling strategy is required to discern details of the aeolian record. • Palaeoclimatic interpretation as to what these depositional events mean is greatly aided by the application of other proxies.