Stormberg Group

Stratigraphy of the Karoo Supergroup in the Karoo Basin
Period Group Formation west of 24°E Formation east of 24°E Assemblage Zone
Jurassic Drakensberg Hiatus Drakensberg
Stormberg Clarens
Triassic Elliot
Molteno
Beaufort
Burgersdorp Cynognathus
Katberg Lystrosaurus
Balfour
Permian Dicynodon
Teekloof
Cistecephalus
Middleton
Tropidostoma
Pristerognathus
Abrahams-Kraal Koonap
Tapinocephalus
Eodicynodon
Ecca Waterford Waterford
Tierberg / Fort Brown Fort Brown
Laingsburg / Ripon Ripon
Collingham Collingham
White Hill White Hill
Prince Albert Prince Albert
Carboniferous Dwyka Elandsvlei Elandsvlei
References: Rubidge (2005),[1] Selden and Nudds (2011).[2]

The Stormberg Group is the name given to the sedimentary geological formations of the Late Triassic Period and the Jurassic Period, found in Karoo Basin region of Southern Africa

They are of the Karoo Supergroup, immediately above the Beaufort Group, and consist mainly of sandstones and mudstones. They preserve a record of gradual desertification.

Formations

The Stormberg Group is subdivided into three formations:

The Molteno Formation consists of two major coarsening-upward sequences, the basal sequence is made up by the Bamboesberg and Indwe Sandstone and the upper sequence by the Transitional Member. Tabular sheets of horizontally and cross stratified medium- to coarse grained sandstone dominate the formation. The sandstones were deposited by braided streams on a vast braidplain.[3]
The Elliot Formation is dominated by red floodplain mudstones with subordinate channel and crevasse splay deposits. These were interpreted as a mixed load dominated meandering system in an increasingly arid setting.[4][5] Towards the top of the formation aeolian sediments occur as metre-scale intercalations in the fluvial deposits of the Elliot Formation.
The Clarens Formation consists of yellow fine-grained sandstones, sandy siltstones and mudstones. This indicates strong aridification of the climate.[7] Wind blown dunes suggest deposition in a desert environment with shallow playa lake and river deposits in the wetter parts of the basin,[8][9] producing a complex interaction of aeolian and aqueous sedimentation.

See also

References

  1. Rubidge, B.S. (2005). "Re-uniting lost continents – Fossil reptiles from the ancient Karoo and their wanderlust". South African Journal of Geology 108 (1): 135–172. doi:10.2113/108.1.135.
  2. Selden, P.; and Nudds, J. (2011). "Karoo". Evolution of Fossil Ecosystems (2 ed.). Manson Publishing. pp. 104–122. ISBN 9781840761603.
  3. Catuneanu, O., Hancox, P. J. and Rubidge, B.S. (1998). Reciprocal flexural behaviour and contrasting stratigraphies: a new basin development model for the Karoo retroarc foreland system, South Africa. Basin Research, 10, 417-439
  4. Visser, J.N. J. and Botha, B.J.V. (1980). Meander belt, point bar, crevasse splay and aeolian deposits from the Elliot Formation in Barkly Pass, northeastern Cape. Transactions of the Geological Society of South Africa, 83, 55–62.
  5. Bordy, E.M., Hancox, J.P. and Rubidge, B.S. (2004). Provenance study of the Late Triassic – Early Jurassic Elliot Formation, main Karoo Basin, South Africa. South African Journal of Geology, 107, 587-602.
  6. "The Stormberg Group".
  7. Beukes, N.J. (1970). Stratigraphy and sedimentology of the Cave Sandstone Stage, Karroo System. In: S.H. Haughton (Editor). Proceedings 2nd IUGS Symposium on Gondwana Stratigraphy and Palaeontology, CSIR, Pretoria, South Africa, 321–341.
  8. Smith, R.M.H., Eriksson P.G. and Botha W.J. (1993) A review of the stratigraphy and sedimentary environments of the Karoo-aged basins of Southern Africa. Journal of African Sciences, 16, 143-169.
  9. Catuneanu, O., Hancox, P. J. and Rubidge, B.S. (1998). Reciprocal flexural behaviour and contrasting stratigraphies: a new basin development model for the Karoo retroarc foreland system, South Africa. Basin Research, 10, 417-439

Further reading

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