Palynological analysis of the holocene section of a new core from Tswaing Crater, South Africa
Date
2011-06-23
Authors
Metwally, Amr Abdel-Sabour Abdel-Hamide
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Abstract
Palynological data from a new core from Tswaing Crater Lake within the savanna
biome of South Africa contributes to a better understanding of vegetation and
climate dynamics during the Holocene. A 650cm sediment core section TSW1,
with 65 samples and fourteen AMS 14C dates, covers a time period between ca
10000-2000 cal yrs BP. No pollen data are available from the lower part of the
profile (600-800cm) due to palynomorph destruction, but a single sample with a
low number of pollen grains gives a glimpse into a presumably very dry time
period at ca11300 cal yrs BP. A warm and dry early Holocene (ca 9000-7500 cal
yrs BP) is evidenced by high pollen percentages of Asteraceae, Tarchonanthus
and Dichrostachys. The mid Holocene phase from ca 7500-4000 cal yrs BP is
characterised by an increase of Burkea, Combretaceae and Podocarpus as well as
aquatics and swamp plant pollen. This suggests warm sub-humid conditions and
local moisture during this time interval. A short-term dry period occurred ca 4000
-3600 cal yrs BP characterized by a significant decline of most tree pollen
including Podocarpus, whereas Poaceae pollen increased slightly. From ca 3600 -
2000 cal yrs BP tree pollen percentages gradually increased and the presence of
Spirostachys pollen suggests a return to warm sub-humid conditions. The upper
part of the profile above a depth of 150cm shows disturbances due to salt mining
and was therefore not sampled. The palaeoclimatic interpretation of the pollen
fluctuations was supported by PCA (Principal Components Analysis). From
around ca 1800 cal yrs BP additional samples were studied in this project in
comparison to the previous study of Scott to improve the resolution. The climatic
investigation from the Tswaing pollen record of the current study supports the climatic interpretations which were inferred from the biomarker analysis by
Kristen et al., 2009. A regional comparison between the current Tswaing pollen
profile and pollen records from Wonderkrater and Lake Eteza was done in the
frame of the current study. The general palaeoclimatic changes recorded from
Tswaing pollen sequence are consistent with the pollen evidence inferred from
Wonderkrater which can attributed to regional changes in eastern South Africa.
These trends differ from those in lake Eteza, especially during the early Holocene,
which might be explained as a consequence of the generally more humid climate
in the coastal plain of KwaZulu-Natal.