Ecca 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 | |
The Ecca Group is a group of sedimentary geological formations found in southern Africa. A component of the Karoo Supergroup, it consists mainly of shales and sandstones, laid down in the sandy shorelines of swamplands during the Permian Period.
Description
The type area for the Ecca Group is in the Karoo Basin of South Africa and Lesotho. In the southwestern Karoo Basin, the Ecca Group has a total thickness of approximately 1300 m.[3] There is no single location where the entire vertical section of the Ecca Group is exposed. At Skoorsteenberg in the southwestern basin there is a 900-m exposure of the unit.[4]
The Ecca Group sandstones and shales originated as clastic sediment deposited in a large and shallow inland sea. Swamps and forest vegetation developed at many places and times during its deposition, resulting in widespread coal deposits. Almost all of South Africa's coal resources and one-third of the coal resources in the Southern Hemisphere are in rocks of the Ecca Group.[5]
Karoo Supergroup stratigraphic sequence
In the Eastern Cape Province the Karoo Basin fill commenced with the deposition of the Dwyka Group, followed by the Ecca Group, the Beaufort Group, the Molteno, Elliot, and Clarens Formations and the igneous Drakensberg Group. The basin followed the typical evolution of foreland basins, with the Ecca Group representing the ‘flysch’ component and the Beaufort Group, the overlying Molteno and Elliot Formations representing the ‘molasse’-fluvial type sediments.[6][7]
Ecca Group stratigraphy in the Eastern Cape Province
The Ecca Group is recognized throughout southern Africa. Stratigraphic units in this group in the Eastern Cape Province include, in order of deposition:[8]
- Prince Albert Formation, marine mudstones; formerly known as Upper Dwyka Shales and assigned to the Dwyka Group[9]
- Whitehill Formation, marine mudstones; formerly known as White Band and assigned to the Dwyka Group[9]
- Collingham Formation, persistent grey shales, alternating with yellow claystones which derive from volcanic ash
- Ripon Formation
- Fort Brown Formation
- Waterford Formation, sandstones and shales
The Pietermaritzburg Formation and the younger Vryheid Formation are also named deposits within the group.
See also
- List of fossiliferous stratigraphic units in South Africa
- List of fossiliferous stratigraphic units in Botswana
References
- ↑ 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.
- ↑ Selden, P.; and Nudds, J. (2011). "Karoo". Evolution of Fossil Ecosystems (2 ed.). Manson Publishing. pp. 104–122. ISBN 9781840761603.
- ↑ H. deV. Wickens and A. H. Bouma. 2000. The Tanqua Fan Complex, Karoo Basin, South Africa. In A. H. Bouma and C. G. Stone, eds., Fine-Grained Turbidite System. American Association of Petroleum Geologists Memoir 72/SEPM Special Publication 68. ISBN 9780891813538. pp. 153-164.
- ↑ Goldhammer, R.K., H. deV. Wickens, A. H. Bouma, and G. Wach. 2000. Sequence Stratigraphic Architecture of the Late Permian Tanqua Submarine Fan Complex, Karoo Basin, South Africa. In A. H. Bouma and C. G. Stone, eds., Fine-Grained Turbidite System. American Association of Petroleum Geologists Memoir 72/SEPM Special Publication 68. ISBN 9780891813538. pp. 165-172.
- ↑ Schlüter, Thomas (2008). Geological Atlas of Africa: With Notes on Stratigraphy, Tectonics, Economic Geology, Geohazards and Geosites of Each Country. Springer. pp. 233–234. ISBN 9783540763734.
- ↑ Johnson, M.R. (1991). Sandstone petrography, provenance and plate tectonic setting in Gondwana context of the south-eastern Cape Karoo basin. South African Journal of Geology 94, 137-154.
- ↑ Catuneanu, O. (2004). Retroarc foreland systems – evolution through time. Journal of African Earth Sciences, 38, 225-242.
- ↑ Johnson, M.R. (1976). Stratigraphy and sedimentology of the Cape and Karoo Sequences in the Eastern Cape Province. Ph.D. thesis (unpubl.), Rhodes University, Grahamstown, 336pp.
- 1 2 H. Martin (2011) [1981]. "The Late Palaeozoic Dwyka Group of the South Kalahari Basin in Namibia and Botswana and the subglacial valleys of the Kaokeveld in Botswana". In M. J. Hambrey, W. B. Harland. Earth's Pre-Pleistocene Glacial Record. Cambridge University Press (Cambridge Earth Science Series). pp. 61–70. ISBN 9780521172301.