A HighResolution Record of Late Quaternary Aeolian Activity at Witpan, South Africa: Palaeoclimatic

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A High-Resolution Record of Late Quaternary
Aeolian Activity at Witpan, South Africa
Palaeoclimatic and Palaeoenvironmental
Implications
Matt Telfer Prof. Dave Thomas Dr Mark Bateman
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Title
Background

• 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 and the advent of luminescence
  dating, the chronology for these landforms was
  extremely vague

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Title
Background

• Stokes et al (1997) represented the first
  systematic dating study of dune forms in this
  area
• Periods of dune-building (arid) identified at
  916, 2026, 4146 and 95115 kyr

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Title
Background

• So what is there still to do?
• The southwestern Kalahari is represented by
  only 8 dates, and the earlier two phases are not
  recorded here.
• Samples are taken from hand-dug pits on the
  surface of the dunes generally 3m deep at most.
• Many dunes represented by a small number of
  dates is deposition between these ages
  continuous or are these discrete phases?
• The sites involved are over 1000km apart
  different climatic controls?

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Title
Aims and Objectives

• Investigate the preservation potential of the
  Kalaharis dunes, and improve process knowledge
  of how an aeolian chronology is preserved
• Extend the aeolian record with coring techniques
• By using a high-resolution strategy within cores
  as well as within the locale, investigate the
  continuity of dune records

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Title
Field site

• Southwestern Kalahari of the Northern Cape,
  South Africa

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Title
Field site

• 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.

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Title
Field site

• 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.

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Spatial variation of lunette deposition
All ages in ka
0.08 0.01
0.20 0.02
Kal 02/4
1.1 0.1
2.0 0.1
Kal 02/5
Kal 02/21
0.07 0.01
Kal 02/20
Kal 02/6
0.53 0.03
0.57 0.04
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Spatial variation of lunette deposition
CaO ()
Sr (ppm)
CaO ()
Sr (ppm)
0.3
60
Linears
Kal 02/21
1.6
419
Pan
0.3
58
5.1
594
Kal 02/5
2.1
310
Kal 02/6
Geochemistry
mean values for all samples at a site
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Title
Coring
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Linear deposition intra-core variation
Kal 02/7
Depth (m)
Age (ka)
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Linear deposition inter-core variation
Kal 04/6
Kal 02/1
3m
Depth (m)
Age (ka)
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Linear dune OSL histograms
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Linear dune OSL histograms
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Linear dune OSL histograms
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Linear dune OSL histograms
Evidence of wet interval at c.8-5ka Wonderwerk
Cave (Butzer 1984) Kathu Vlei pollen and
clastics (Beaumont 1984) Namibian valley
silts (Eitel et al 2001)
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Linear dune OSL histograms
Evidence of dry interval at c.14-9ka Kathu Vlei
pollen (Beaumont et al 1984) Otavi cenotes
(Brooke et al 1998) Tsodilo Hills lakeshores
(Thomas et al 2003)
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Linear dune OSL histograms
Lake stands indicating wetter regional
conditions than present at 2712 ka with a
possible drying out at 2219 ka (Thomas et al
2003) Tsodilo Hills
Short-lived dry interval from 20-19ka (Brook et
al 1998), South African tufas and Botswanan caves
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Title
Conclusions

• 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 dune building near 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.

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Title
Summary

• So how are we doing?
• The southwestern Kalahari is represented by
  only 8 dates, and the earlier two phases are not
  recorded here.
• Samples are taken from hand-dug pits on the
  surface of the dunes generally 3m deep at most.
• Many dunes represented by a small number of
  dates is deposition between these ages
  continuous or are these discrete phases?
• The sites involved are over 1000km apart
  different climatic controls?

?
?
?
?
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Implications for further work

• The Kalaharis linear dunes have the potential
  to record long albeit discontinuous sequences
  of aeolian deposition.
• 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 further proxies.