Uitenhage Group

Geological group of post-Karoo Mesozoic rocks in South Africa

Uitenhage Group

Stratigraphic range: Late Early Jurassic-Early Cretaceous
~183–100 Ma

PreꞒ

Type| Geologic group
Sub-units| Enon, Kirkwood, Sundays River & Buffelskloof Formations
Underlies| Algoa Group
Overlies| Suurberg Group
Lithology
Primary| Sandstone, mudstone, siltstone, shale, conglomerate
Other| Calcite
Location
Region| Western & Eastern Cape
Country|  South Africa
Type section
Named for| Uitenhage area

Map showing extent of the Uitenhage Group in the Algoa and Gamtoos Basins

The Uitenhage Group is one of three geological groups, which comprise the onshore and offshore post-Karoo middle to lower Upper Mesozoic geological rock units in South Africa.[1][2][3][4] Stratigraphically, the Uitenhage Group overlies the Suurberg Group and is overlain by the Algoa Group.[5][6] It contains four formations that range in age from late Early Jurassic and late Early Cretaceous in age (~183 - 100 Ma).

## Geographic extent

[edit]

In the onshore part of the southern Cape, deposits of the Uitenhage Group occur predominantly in the Algoa and Gamtoos Basins, which are situated north/north-west of Port Elizabeth in the Eastern Cape, South Africa. Smaller deposits also occur in the Baviaanskloof, Georginda, Vlakteplaas, Oudtshoorn, Plettenberg Bay, Knysna, Herbertsdale-Mossel Bay, Heidelberg-Riversdale, Swellendam, and Worcester-Robertson Basins.[7] These are grabens and half-grabens (rift basins) that opened up due to mainly normal faulting processes during the break-up of Gondwana.[7][1][8]

## Stratigraphic units

[edit]

Stratigraphic units in this group include (from oldest to youngest):

* Enon Formation: Contains subordinate sandstones and different types of thickly-bedded conglomerates, which consist mainly of quartzite and sometimes slate, shale, and charcoal. The clasts are poorly-sorted, sub-rounded to rounded pebbles and cobbles. Deposition occurred mainly in high-energy alluvial environments (e.g., alluvial fans, low sinuosity rivers).[7]
* Kirkwood Formation: Contains mainly medium-grained sandstone that is locally charcoal-rich, sporadic conglomerates, and variegated mudstone. Out of the three formations of the Uitenhage Group, the Kirkwood is the most well-studied, and is extremely fossil-rich. Deposition occurred under mainly fluvial conditions at or near sea level.[9][10][11][12][13][14]
* Sundays River Formation: Contains fine- to medium-grained grey sandstones, siltstones, and mudstones. The sandstone layers are frequently cemented with calcite and contain shell fragments. The Sundays River is also highly fossiliferous. Deposition occurred under shallow marine and estuarine conditions.[15][16][17]
* Buffelskloof Formation: Deposited in a high energy braided river system with conglomerate deposits, similar to that of the Enon Formation. Some fossil material such as petrified wood and scant remains of fossil dinosaur teeth and claws have been recovered. In the Herbertsdale/Mossel Bay Basin this formation, with the overlying Hartenbos Formation, forms the lateral equivalent of the Sundays River Formation.[18]

## Paleontology

[edit]

Fossils are especially common in the Kirkwood and Sundays River Formations, although regarding the Sundays River Formation the most common fossils are of invertebrates. Past expeditions within the Kirkwood Formation have uncovered several dis-articulated remains of theropod, sauropod, and ornithopod dinosaurs,[19][11][20][21] and a plesiosaur fossil[17] is known from the Sundays River Formation. Fossil remains of amphibians, lizards, fishes, and small mammals have also been recovered.[19][22] A variety of bivalve, gastropod, ammonites, and ostracods[15][2] are likewise known from these deposits. The fossil flora is equally diverse[12][13] and silicified tree trunks - some with evidence of being charred by fire[23] \- have also been found.

## References

[edit]

1. ^ a b Shone, R.W. (2006-01-01). "Onshore post-Karoo Mesozoic deposits". The Geology of South Africa: 541–552.
2. ^ a b McLachlan, I.R.; McMillan, I.K. (1979-01-01). "Microfaunal biostratigraphy, chronostratigraphy and history of Mesozoic and Cenozoic deposits on the coastal margin of South Africa". Geological Society of South Africa, Special Publication. 6: 161–181.
3. ^ McMillan, I.K.; Brink, G.I.; Broad, D.S.; Maier, J.J. (1997-01-01). "Chapter 13 Late Mesozoic Sedimentary Basins Off the South Coast of South Africa". Sedimentary Basins of the World. 3: 319–376. doi:10.1016/S1874-5997(97)80016-0. ISBN 9780444825711. ISSN 1874-5997.
4. ^ "Structural and sedimentary development of the continental margin off Southwestern Africa" (PDF). Retrieved 2024-02-03.
5. ^ Marsh, J. S. Goonie (2016). "New Evidence for the Correlation of Basalts of the Suurberg Group with the Upper Part of the Karoo Basalt Sequence of Lesotho". Origin and Evolution of the Cape Mountains and Karoo Basin. Regional Geology Reviews. Springer, Cham. pp. 59–65. doi:10.1007/978-3-319-40859-0_6. ISBN 9783319408583.
6. ^ Klinger, H. C., & Kennedy, W. J. (1977). Cretaceous faunas from Zululand, South Africa, and southern Mozambique. The Aptian Ancyloceratidae (Ammonoidea). Annals of the South African Museum, 73(9), 215-359.
7. ^ a b c Muir, R.A.; Bordy, E.M.; Reddering, J.S.V.; Viljoen, J.H.A. (2017-06-01). "Lithostratigraphy of the Enon Formation (Uitenhage Group), South Africa". South African Journal of Geology. 120 (2): 273–280. Bibcode:2017SAJG..120..273M. doi:10.25131/gssajg.120.2.273. ISSN 1012-0750.
8. ^ Gresse, P.G.; Theron, J.N.; Fitch, F.J.; Miller, J.A. (1992-01-01). "Tectonic inversion and radiometric resetting of the basement in the Cape Fold Belt". Inversion Tectonics of the Cape Fold Belt, Karoo and Cretaceous Basins of Southern Africa: 217–228.
9. ^ Muir, R.A.; Bordy, E.M.; Reddering, J.S.V.; Viljoen, J.H.A. (2017-06-01). "Lithostratigraphy of the Kirkwood Formation (Uitenhage Group), including the Bethelsdorp, Colchester and Swartkops Members, South Africa". South African Journal of Geology. 120 (2): 281–293. Bibcode:2017SAJG..120..281M. doi:10.25131/gssajg.120.2.281. ISSN 1012-0750.
10. ^ Rich, Tom; Molnar, R.E.; Vickers Rich, Patricia (1983-01-01). "Fossil vertebrates from the Late Jurassic or Early Cretaceous Kirkwood Formation, Algoa Basin, southern Africa". pp. 281–291.
11. ^ a b W. McPhee, Blair; Mannion, Philip; De Klerk, William; Choiniere, Jonah (2016-04-01). "High diversity in the sauropod dinosaur fauna of the Lower Cretaceous Kirkwood Formation of South Africa: Implications for the Jurassic–Cretaceous transition". Cretaceous Research. 59: 228–248. Bibcode:2016CrRes..59..228M. doi:10.1016/j.cretres.2015.11.006. hdl:10044/1/27470.
12. ^ a b Bamford, Marion (1986-01-01). "Aspects of the palaeoflora of the Kirkwood and Sundays River Formations, Algoa Basin, South Africa".
13. ^ a b Gomez, Bernard; Bamford, Marion; Delclòs, Xavier (2002-03-01). "Lower Cretaceous plant cuticles and amber (Kirkwood Formation, South Africa)". Comptes Rendus Palevol. 1 (2): 83–87. Bibcode:2002CRPal...1...83G. doi:10.1016/S1631-0683(02)00014-3.
14. ^ Forster, Catherine A.; Farke, Andrew A.; McCartney, Jacob A.; De Klerk, William J.; Ross, Callum F. (2009). "A "basal" tetanuran from the Lower Cretaceous Kirkwood Formation of South Africa". Journal of Vertebrate Paleontology. 29 (1): 283–285. Bibcode:2009JVPal..29..283F. doi:10.1671/039.029.0101. S2CID 131280290.
15. ^ a b Brenner, P; HJ, Oertli (1976-01-01). "Lower Cretaceous Ostracodes (Valanginian to Hauterivian) from the Sundays River Formation, Algoa Basin, South Africa". Bulletin Centre Recherches Pau-SNPA. 10: 471–533.
16. ^ Bamford, Marion (1986-01-01). "Aspects of the palaeoflora of the Kirkwood and Sundays River Formations, Algoa Basin, South Africa".
17. ^ a b Andrews, C.W. (2018-05-08). "Description of a new plesiosaur (Plesiosaurus capensis, sp. nov.) from the Uitenhage Beds of Cape Colony". Annals of the South African Museum. 7: 309–322.
18. ^ "Extension of quarrying on portion 12 of farm Hartenbosch 217 (Maandagskop crusher), Mossel bay, Western cape" (PDF). Archived from the original (PDF) on 2018-05-08. Retrieved 2018-05-08.
19. ^ a b Rich, Tom; Molnar, R.E.; Vickers Rich, Patricia (1983-01-01). "Fossil vertebrates from the Late Jurassic or Early Cretaceous Kirkwood Formation, Algoa Basin, southern Africa". pp. 281–291.
20. ^ De Klerk, William; Forster, Catherine; Sampson, Scott; Chinsamy-Turan, Anusuya; Ross, Callum (2000-06-27). "A new coelurosaurian dinosaur from the Early Cretaceous of South Africa". Journal of Vertebrate Paleontology. 20 (2): 324–332. doi:10.1671/0272-4634(2000)020[0324:ANCDFT]2.0.CO;2. S2CID 128622530.
21. ^ Choiniere, Jonah; Forster, Catherine; De Klerk, William (2012-08-01). "New information on Nqwebasaurus thwazi, a coelurosaurian theropod from the Early Cretaceous Kirkwood Formation in South Africa". Journal of African Earth Sciences. s 71–72: 1–17. Bibcode:2012JAfES..71....1C. doi:10.1016/j.jafrearsci.2012.05.005.
22. ^ Ross, Callum; Sues, Hans-Dieter; De Klerk, William (1999-03-15). "Lepidosaurian remains from the Lower Cretaceous Kirkwood Formation of South Africa". Journal of Vertebrate Paleontology. 19 (1): 21–27. Bibcode:1999JVPal..19...21R. doi:10.1080/02724634.1999.10011119.
23. ^ Muir, Robert A.; Bordy, Emese M.; Prevec, Rose (2015-09-01). "Lower Cretaceous deposit reveals first evidence of a post-wildfire debris flow in the Kirkwood Formation, Algoa Basin, Eastern Cape, South Africa". Cretaceous Research. 56: 161–179. Bibcode:2015CrRes..56..161M. doi:10.1016/j.cretres.2015.04.005. ISSN 0195-6671.

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Cretaceous|

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