| Type |
Article |
| Date |
2014-07-01 |
| Language |
English |
| Author(s) |
Lyons Richard1, 2, Tooth Stephen1, 2, Duller Geoff A. T.1 |
| Affiliation(s) |
1 : Aberystwyth Univ, Dept Geog & Earth Sci, Aberystwyth SY23 3DB, Dyfed, Wales.
2 : Univ Witwatersrand, Sch Geosci, Johannesburg, South Africa. |
| Source |
Quaternary Science Reviews (0277-3791) (Pergamon-elsevier Science Ltd), 2014-07-01 , Vol. 95 , P. 43-59 |
| DOI |
10.1016/j.quascirev.2014.04.021 |
| WOS© Times Cited |
45 |
| Keyword(s) |
Erfkroon, Southern Africa, Palaeosol, OSL, Quaternary, Mineral magnetism |
| Abstract |
The nature, spatial patterns and forcing mechanisms of Quaternary climatic changes across southern Africa remain unresolved and contentious, principally due to the scarcity of continuous and robustly-dated proxy records. We present what we interpret to be a broadly continuous record of late Quaternary climatic change based on optically stimulated luminescence (OSL) dating, and mineral magnetic and diffuse reflectance spectroscopy (DRS) analyses of stacked palaeosols within an overbank alluvial succession along the Modder River, central South Africa. The OSL ages indicate that alluvial sedimentation occurred at a fairly steady rate, averaging similar to 0.15 mm/yr from at least 44 ka until similar to 0.83 ka. This suggests that the palaeosols are accretionary, having formed contemporaneously with sedimentation. Climate is identified as the key soil-forming factor controlling the intensity of pedogenesis and is reflected in the changing concentration of pedogenic ferrimagnetic minerals (magnetite/maghemite) of single domain and superparamagnetic dimensions, and by variations in the amount of hematite compared to goethite. These data indicate that the climate was generally dry (rainfall similar to 200-400 mm/yr) from similar to 46 to 32 ka, except for a brief peak in humidity at similar to 42 ka. There was then a period of greater humidity (rainfall similar to 400 -600 mm/yr) from similar to 32 to 28 ka, possibly reflecting enhanced moisture supply from the Atlantic Ocean associated with the equatorward migration and intensification of westerly storm tracks. Although the precise mechanism remains unresolved, this climatic change may have been linked to an obliquity minimum at similar to 29 ka. After similar to 28 lea, the climate became progressively cooler and drier, especially between similar to 18 and similar to 15.5 ka when rainfall was as low as similar to 100-200 mm/yr. Temperatures and rainfall then increased from similar to 15.5 ka onwards, with the latter possibly linked to rising sea-surface temperatures in the SW Indian Ocean and enhanced moisture supply from easterly circulation. At similar to 0.83 ka, a time corresponding with part of the Medieval Climatic Anomaly (MCA, similar to 900-1300 AD), rainfall reached similar to 600-700 mm/yr and was higher than at present (similar to 400-500 mm/yr). Fluvial landforms have previously been overlooked as a source of palaeoenvironmental information in southern Africa, but this study clearly demonstrates the potential to extract robust palaeoenvironmental data from alluvial-palaeosol successions in the arid to semi-arid interior where other forms of proxy record are scarce. |
| Full Text |
| File |
Pages |
Size |
Access |
| Publisher's official version |
17 |
3 MB |
Open access |
|
