Elliot Formation

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Elliot Formation
Stratigraphic range: Norian-Hettangian
~210–190 Ma
Elliot Formation Caves in 'Matalane Valley, Leribe, Lesotho - panoramio.jpg
Elliot Formation caves in the Matalane Valley, Leribe, Lesotho
TypeGeological formation
Unit ofStormberg Group
Sub-unitsUpper Elliot, Lower Elliot
UnderliesClarens Formation
OverliesMolteno Formation
Thicknessup to 500 m (1,600 ft)
Lithology
PrimaryMudstone, sandstone
OtherSiltstone, conglomerate
Location
Coordinates30°30′S 27°24′E / 30.5°S 27.4°E / -30.5; 27.4Coordinates: 30°30′S 27°24′E / 30.5°S 27.4°E / -30.5; 27.4
Approximate paleocoordinates44°06′S 1°54′W / 44.1°S 1.9°W / -44.1; -1.9
RegionEastern Cape, Orange Free State, Mafeteng, Maseru, Quthing, Qacha's Nek & Mohale's Hoek
Country Lesotho
 South Africa
Type section
Named forElliot, Eastern Cape
Elliot Formation is located in South Africa
Elliot Formation
Elliot Formation (South Africa)

The Elliot Formation is a geological formation and forms part of the Stormberg Group, the uppermost geological group that comprises the greater Karoo Supergroup. Outcrops of the Elliot Formation have been found in the northern Eastern Cape, southern Free State, and in the eastern KwaZulu-Natal provinces of South Africa. Outcrops and exposures are also found in several localities in Lesotho such as Qacha's Neck, Hill Top, Quthing, and near the capital, Maseru. The Elliot Formation is further divided into the lower (LEF) and upper (UEF) Elliot formations to differentiate significant sedimentological differences between these layers. The LEF is dominantly Late Triassic (Norian-Rhaetian) in age while the UEF is mainly Early Jurassic (Hettangian) and is tentatively regarded to preserve a continental record of the Triassic-Jurassic boundary in southern Africa. This geological formation is named after the town of Elliot in the Eastern Cape, and its stratotype locality is located on the Barkly Pass, 9 km north of the town.[1][2][3]

Geology[edit]

The Elliot Formation unconformably overlies the Molteno Formation and is conformably overlain by the Clarens Formation. Due to the reddish colour of the rocks, the Elliot Formation is colloquially referred to as the “Red Beds” in older literature.

The Elliot Formation is dominated by mudstones and siltstones that can be finely laminated. However, the internal structures in the mudstones are often not visible due to locally poor laminations. Calcareous nodules are also found in the mudstone layers and become more frequent up section into the UEF. The mudstones range in colour from greyish purple red in the LEF and turn a more brick red colour with more mature palaeosols in the UEF. Localized intraformational pebble conglomerates that comprise intrabasinal clasts that comprise mud chips, quartzite pebbles, pedogenic nodules, and fossil bone fragments only occur in the UEF. The lower and upper Elliot formations both contain sandstones but they vary in their internal geometries. The sandstones of the LEF mainly comprise laterally accreting channel deposits that are multi-story and contain trough, low angle, and planar, cross-bedding. Ripple cross laminations with good horizontal lamination are also present. In the UEF, sandstone beds are single story and mainly reflect downstream accretion channel geometries and are more tabular in appearance. Common internal sedimentary structures of UEF sandstones are planar, low angle cross-bedding, horizontal and ripple-cross laminations.

The LEF was deposited in a fluvio-lacustrine environment where rivers were more perennial and formed meandering channel geometries, as evidenced by the presence of lateral accretion. However, this depositional environment changed at the onset of the UEF deposits where evidence of shallower river channels, longer periods of floodplain stasis (mature palaeosols) and flash flood events (pedogenic nodule conglomerates) shows that the climate became more arid.[4][5][6][7]

Paleontology[edit]

The Elliot Formation is well known for its diverse dinosaur fossils. The most common dinosaur species recovered from the Elliot Formation is of the sauropodomorph species Massospondylus carinatus.[8][9] Other species include Blikanasaurus cromptoni, Aardonyx celestae, Euskelosaurus brownii, Antetonitrus ingenipes, Pulanesaurus eocollum, and the largest sauropodomorph yet found, Ledumahadi mafube.[10][11][12][13][14][15][16][17] Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park.[18][19] Euskelosaurus fossils are more common in the LEF while Massospondylus are only found in the UEF. The basal ornithischian dinosaurs, Heterodontosaurus tucki, Lesothosaurus diagnosticus, Abrictosaurus consors, and Lycorhinus angustidens have also been recovered from the UEF.[20][21] In addition this formation has yielded various crocodylomorph species,[22] namely Litargosuchus leptorhynchus, Sphenosuchus acutus, Orthosuchus stormbergi,[23][24][25][26] and the mammaliaform Megazostrodon rudnerae[27]. A large theropod dinosaur, Dracovenator regenti, has been found in the UEF.[28] The dicynodont species Pentasaurus goggai [29] and the tritheledontid cynodont Elliottherium kersteni [30][31] have also been recovered from the Elliot Formation. More recent vertebrate fossil finds near the town Qhemegha in the Eastern Cape have yielded possible fossil material of a popsauroid pseudosuchian. The mudstones of the LEF sometimes yield petrified wood, fossil plant matter, crustaceans, fishes, and turtles while the sandstones of the upper Elliot Formation more often contain various trace fossils. These include vertebrate trackways of basal ornithischian dinosaurs found in the Leribe, Mafeteng, and Mohales Hoek Districts of Lesotho. Possible trackways of the dicynodont Pentasaurus have been found on Morobong Hill in the Mohales Hoek District of Lesotho.[32][33][34][35]

Correlation[edit]

The Elliot Formation is currently considered to correlate chronostratigraphically with geological formations of the Bodibeng Sandstone of the Tuli Basin in Botswana, the Omingonde Formation of the Etjo Basin in Namibia, and the Chinle Formation of the Colorado Plateau in Utah, United States.[36][37][38][39][40][41]

References[edit]

  1. ^ Bordy, Emese M.; John Hancox, P.; Rubidge, Bruce S. (2004-03-01). "Fluvial style variations in the Late Triassic–Early Jurassic Elliot formation, main Karoo Basin, South Africa". Journal of African Earth Sciences. 38 (4): 383–400. doi:10.1016/j.jafrearsci.2004.02.004. ISSN 1464-343X.
  2. ^ "A description of the sedimentology and palaeontology of the Late Triassic–Early Jurassic Elliot Formation in Lesotho". WIReDSpace Wits. 2004-09-01. ISSN 0078-8554.
  3. ^ Bordy, E.M.; Eriksson, P. (2015-09-01). "LITHOSTRATIGRAPHY OF THE ELLIOT FORMATION (KAROO SUPERGROUP), SOUTH AFRICA". South African Journal of Geology. 118 (3): 311–316. doi:10.2113/gssajg.118.3.311. hdl:2263/55739. ISSN 1012-0750.
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  5. ^ "Meander channel, point bar, crevasse splay and aeolian deposits from the Elliot Formation in Barkly Pass, North-eastern Cape". South African Journal of Geology. 83 (1). 1980-01-01. ISSN 1012-0750.
  6. ^ Bordy, E.M.; Eriksson, P. (2015-09-01). "LITHOSTRATIGRAPHY OF THE ELLIOT FORMATION (KAROO SUPERGROUP), SOUTH AFRICA". South African Journal of Geology. 118 (3): 311–316. doi:10.2113/gssajg.118.3.311. hdl:2263/55739. ISSN 1012-0750.
  7. ^ Sciscio, Lara; De Kock, Michiel; Bordy, Emese; Knoll, Fabien (2017-11-01). "Magnetostratigraphy across the Triassic-Jurassic boundary in the main Karoo Basin". Gondwana Research. 51: 177–192. doi:10.1016/j.gr.2017.07.009. ISSN 1342-937X.
  8. ^ Sues, H.D., Reisz, R.R., Hinic, S. and Raath, M.A., 2004. On the skull of Massospondylus carinatus Owen, 1854 (Dinosauria: Sauropodomorpha) from the Elliot and Clarens formations (Lower Jurassic) of South Africa. Annals of Carnegie Museum, 73(4), pp.239–257.
  9. ^ Chinsamy, Anusuya. "Bone histology and growth trajectory of the prosauropod dinosaur Massospondylus carinatus Owen | Request PDF". ResearchGate. Retrieved 2018-11-14.
  10. ^ Galton, Peter M.; Heerden, Jacques (April 1998). "Anatomy of the prosauropod dinosaurBlikanasaurus cromptoni (Upper Triassic, South Africa), with notes on the other tetrapods from the lower Elliot Formation". Paläontologische Zeitschrift. 72 (1–2): 163–177. doi:10.1007/bf02987824. ISSN 0031-0220.
  11. ^ Yates, Adam M. (2003). "A definite prosauropod dinosaur from the Lower Elliot Formation (Norian: Upper Triassic) of South Africa". ISSN 0078-8554. Cite journal requires |journal= (help)
  12. ^ Barrett, Paul M. (2004-09-01). "Sauropodomorph dinosaur diversity in the upper Elliot Formation (Massospondylus range zone : Lower Jurassic) of South Africa : research letter". South African Journal of Science. 100 (9–10). ISSN 0038-2353.
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  14. ^ Hancox, P. John; Rubidge, Bruce S.; Yates, Adam M. (1 September 2004). "First record of a sauropod dinosaur from the upper Elliot Formation (Early Jurassic) of South Africa : research letter". South African Journal of Science. 100 (9): 504–506.
  15. ^ McPhee, Blair W.; Yates, Adam M.; Choiniere, Jonah N.; Abdala, Fernando (2014-04-25). "The complete anatomy and phylogenetic relationships of Antetonitrus ingenipes (Sauropodiformes, Dinosauria): implications for the origins of Sauropoda". Zoological Journal of the Linnean Society. 171 (1). doi:10.1111/zoj12127. ISSN 1096-3642.
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  18. ^ Kitching, James (1979). "Preliminary report on a clutch of six dinosaurian eggs from the Upper Triassic Elliot Formation, Northern Orange Free State". Palaeontologia Africana. 22: 41–45.
  19. ^ Reisz, Robert R.; Evans, David C.; Sues, Hans-Dieter; Scott, Diane (2010-12-02). "Embryonic skeletal anatomy of the sauropodomorph dinosaurMassospondylusfrom the Lower Jurassic of South Africa". Journal of Vertebrate Paleontology. 30 (6): 1653–1665. doi:10.1080/02724634.2010.521604. ISSN 0272-4634.
  20. ^ Knoll, Fabien (2002-07-08). "Nearly complete skull ofLesothosaurus(Dinosauria: Ornithischia) from the Upper Elliot Formation (Lower Jurassic: Hettangian) of Lesotho". Journal of Vertebrate Paleontology. 22 (2): 238–243. doi:10.1671/0272-4634(2002)022[0238:ncsold]2.0.co;2. ISSN 0272-4634.
  21. ^ Butler, Richard J. (October 2005). "The 'fabrosaurid' ornithischian dinosaurs of the Upper Elliot Formation (Lower Jurassic) of South Africa and Lesotho". Zoological Journal of the Linnean Society. 145 (2): 175–218. doi:10.1111/j.1096-3642.2005.00182.x. ISSN 1096-3642.
  22. ^ Clark, James M.; Sues, Hans-Dieter (2002-08-21). "Two new basal crocodylomorph archosaurs from the Lower Jurassic and the monophyly of the Sphenosuchia". Zoological Journal of the Linnean Society. 136 (1): 77–95. doi:10.1046/j.1096-3642.2002.00026.x. ISSN 1096-3642.
  23. ^ Walker, A. D. (1990-10-29). "A revision of Sphenosuchus acutus Haughton, a crocodylomorph reptile from the Elliot Formation (late Triassic or early Jurassic) of South Africa". Phil. Trans. R. Soc. Lond. B. 330 (1256): 1–120. doi:10.1098/rstb.1990.0185. ISSN 0962-8436.
  24. ^ Nash, Diane (2009-08-20). "A crocodile from the Upper Triassic of Lesotho". Journal of Zoology. 156 (2): 163–179. doi:10.1111/j.1469-7998.1968.tb05927.x. ISSN 0952-8369.
  25. ^ Nash, D.S., 1975. The morphology and relationships of a crocodilian, Orthosuchus stormbergi, from the Upper Triassic of Lesotho. South African Museum.
  26. ^ Dollman, K. N.; Viglietti, P. A.; Choiniere, J. N. (2017-10-12). "A new specimen of Orthosuchus stormbergi (Nash 1968) and a review of the distribution of Southern African Lower Jurassic crocodylomorphs". Historical Biology. 31 (5): 653–664. doi:10.1080/08912963.2017.1387110. ISSN 0891-2963.
  27. ^ E, Gow, Chris (1986-06-30). "A new skull of Megazostrodon (Mammalia, Triconodonta) from the Elliot Formation (Lower Jurassic) of Southern Africa". ISSN 0078-8554. Cite journal requires |journal= (help)
  28. ^ "A new theropod dinosaur from the Early Jurassic of South Africa and its implication for the early evolution of theropods | Request PDF". ResearchGate. Retrieved 2018-11-16.
  29. ^ F., Kammerer, Christian (2018). "The first skeletal evidence of a dicynodont from the lower Elliot Formation of South Africa". Palaeontologia Africana : Annals of the Evolutionary Studies Institute. ISSN 2410-4418.
  30. ^ Hancox, P. J.; Sidor, C. A. (March 2006). "Elliotherium Kersteni, A New Tritheledontid from the Lower Elliot Formation (Upper Triassic) of South Africa". Journal of Paleontology. 80 (2): 333–342. CiteSeerX 10.1.1.557.9156. doi:10.1666/0022-3360(2006)080[0333:EKANTF]2.0.CO;2. ISSN 0022-3360.
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  32. ^ Anderson, J.M.; Anderson, H.M.; Cruickshank, A.R.I. (1998). "Late Triassic ecosystems of the Molteno Lower Elliot biome of southern Africa" (PDF). Palaeontology. 41 (3): 387–421.
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  37. ^ Eriksson, P.; Bordy, E. M. (September 2015). "Lithostratigraphy of the Elliot Formation (Karoo Supergroup), South Africa". South African Journal of Geology. 118 (3): 311–316. doi:10.2113/gssajg.118.3.311. hdl:2263/55739. ISSN 1012-0750.
  38. ^ Smith, R. M.H.; Swart, R. (2002-06-01). "Changing Fluvial Environments and Vertebrate Taphonomy in Response to Climatic Drying in a Mid-Triassic Rift Valley Fill: The Omingonde Formation (Karoo Supergroup) of Central Namibia". PALAIOS. 17 (3): 249–267. doi:10.1669/0883-1351(2002)017<0249:CFEAVT>2.0.CO;2. ISSN 0883-1351.
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  40. ^ Walker, A. D. (1990-10-29). "A revision of Sphenosuchus acutus Haughton, a crocodylomorph reptile from the Elliot Formation (late Triassic or early Jurassic) of South Africa". Phil. Trans. R. Soc. Lond. B. 330 (1256): 1–120. doi:10.1098/rstb.1990.0185. ISSN 0962-8436.
  41. ^ Tucker, Maurice E.; Benton, Michael J. (1982-12-01). "Triassic environments, climates and reptile evolution". Palaeogeography, Palaeoclimatology, Palaeoecology. 40 (4): 361–379. doi:10.1016/0031-0182(82)90034-7. ISSN 0031-0182.