Textural characteristics, mode of transportation and depositional environment of the Stormberg Group in the Eastern Cape, South Africa: evidence from grain size and lithofacies analyses
The Stormberg Group comprises the Molteno, Elliot and Clarens formations and is one of four stratigraphical groups that make up the Karoo Supergroup in South Africa. The group is the highest unit in the Karoo Basin, representing the final phase of preserved sedimentation. The major problem with th...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Sciendo and Adam Mickiewicz University
2022
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| Subjects: | |
| Online Access: | https://doi.org/10.2478/logos-2022-0005 http://hdl.handle.net/11408/5067 |
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| Summary: | The Stormberg Group comprises the Molteno, Elliot and Clarens formations and is one of four stratigraphical groups
that make up the Karoo Supergroup in South Africa. The group is the highest unit in the Karoo Basin, representing the
final phase of preserved sedimentation. The major problem with the Stromberg Group is that the mode of transport, hy-
drodynamic energy conditions and depositional environment are still poorly understood. For the present paper, grain
size and lithofacies studies on selected sandstones from the Molteno, Elliot and Clarens formations were performed
so as to elucidate their textural characteristics, depositional processes, sedimentation mechanisms and hydrodynamic
energy conditions and to discriminate different depositional environments. The statistical parameters of grain size
distribution (mean grain size, standard deviation, skewness and kurtosis) show that the sandstones are predominantly
unimodal, fine grained, moderately well sorted, mesokurtic and near symmetrical. The bivariate diagrams of the afore-
mentioned statistical parameters demonstrate that river and aeolian dune had the greatest impact on the depositional
environments. Likewise, the C-M pattern (Passega diagram) shows that the sandstones were mostly deposited through
tractive current process. Furthermore, the C-M diagram reveals the prevalence of rolling, suspension and graded sus-
pension modes of sediment transportation. Seventeen sedimentary lithofacies were identified and grouped into seven
lithofacies associations. These lithofacies associations indicate braided channel, overbank and swamp deposits for the
Molteno Formation, alluvial fan/floodplain and playa deposits for the Elliot Formation and aeolian deposits for the
Clarens Formation. |
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