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  • 21 Aug, 2019

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Elliot Formation
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-Hettangian) in age while the UEF is mainly Early Jurassic (Sinemurian-Pliensbachian) 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.

Geology

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 geologic 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.

Correlation

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.

Paleontology

The Elliot Formation is well known for its diverse dinosaur fossils. The most common dinosaur species is of the sauropodomorph species Massospondylus carinatus. Other species include Blikanasaurus cromptoni, Aardonyx celestae, Euskelosaurus browni, Antetonitrus ingenipes, Pulanesaura eocollum, and the largest sauropodomorph yet found, Ledumahadi mafube. Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park. 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. In addition this formation has yielded various crocodylomorph species, namely Litargosuchus leptorhynchus, Sphenosuchus acutus and Orthosuchus stormbergi. A large theropod dinosaur, Dracovenator regenti, has been found in the UEF. Synapsids from the formation include the dicynodont Pentasaurus goggai the tritheledontid cynodont Elliotherium kersteni and the mammaliaform Megazostrodon rudnerae. More recent vertebrate fossil finds near the town Qhemegha in the Eastern Cape have yielded possible fossil material of a poposauroid 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.

Dinosaurs

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ornithischians

Ornithischians of the Elliot Formation
Genus Species Location Stratigraphy Notes Images
Abrictosaurus A. consors
  • Upper Elliot
 A heterodontosaurid, formerly species of Lycorhinus
Eocursor E. parvus
  • Upper Elliot
 A basal ornithischian
Fabrosaurus F. australis
  • Upper Elliot
 A basal ornithischian, nomen dubium
Heterodontosaurus H. tucki
  • Upper Elliot
 A heterodontosaurid
Lesothosaurus L. diagnosticus
  • Upper Elliot
 A basal neornithischian or thyreophoran, formerly species of Fabrosaurus
Lycorhinus L. angustidens
  • Upper Elliot
 A heterodontosaurid
Pegomastax P. africana
  • Upper Elliot
 A heterodontosaurid

Sauropodomorphs

Sauropodomorphs of the Elliot Formation
Genus Species Location Stratigraphy Notes Images
Aardonyx A. celestae
  • Upper Elliot
 A derived sauropodomorph
Antetonitrus A. ingenipes
  • Upper Elliot
 A derived sauropodomorph or basal sauropod
Arcusaurus A. pereirabdalorum
  • Spion Kop Heelbo
  • Upper Elliot
 A basal sauropodomorph, known from juveniles
Blikanasaurus B. cromptoni
  • Blikana Mountain
  • Lower Elliot
 A derived sauropodomorph or basal sauropod
Eucnemesaurus E. fortis
  • Lower Elliot
 A possible riojasaurid
E. entaxonis
Euskelosaurus E. browni
  • Lower Elliot
 A plateosaurid, potentially dubious
Gryponyx G. africanus
  • Upper Elliot
 A massospondylid, potentially dubious
Ignavusaurus I. rachelis
  • Upper Elliot
 A massospondylid, known from a juvenile, potential synonym of Massospondylus
Kholumolumo K. ellenbergerorum
  • Lower Elliot
 A basal sauropodiform
Ledumahadi L. mafube A derived sauropodomorph or basal sauropod, largest in the formation
Massospondylus M. carinatus
  • Upper Elliot
 A massospondylid, most common fossil found
M. kaalae
  • Upper Elliot
 A massospondylid, differs from M. carinatus in cranial features
Melanorosaurus M. readi
  • Thaba 'Nyama
  • Lower Elliot
 A derived sauropodomorph
Meroktenos M. thabanensis
  • Thabana Morena
  • Lower Elliot
 A derived sauropodomorph, formerly a species of Melanorosaurus
Plateosauravus P. cullingworthi
  • Lower Elliot
 A basal sauropodomorph, formerly specimens of Euskelosaurus
Pulanesaura P. eocollum
  • Upper Elliot
 A derived sauropodomorph or basal sauropod
Sefapanosaurus S. zastronensis
  • Upper or Lower Elliot
 A derived sauropodomorph

Theropods

Theropods of the Elliot Formation
Genus Species Location Stratigraphy Notes Images
Dracovenator D. regenti
  • Upper Drumbo Farm
  • Upper Elliot
 A dilophosaurid
Megapnosaurus M. rhodesiensis
  • Syntarsus site.
  • Upper Elliot
 A coelophysid

Suchians

Crocodylomorphs

Crocodylomorphs of the Elliot Formation
Genus Species Location Stratigraphy Notes Images
Basutodon B. ferox
  • Lower Elliot
 A dubious suchian
Litargosuchus L. leptorhynchus
  • Eagles Crag Farm
  • Upper Elliot
 A basal crocodylomorph
Orthosuchus O. stormbergi
  • Upper Elliot
 A possible protosuchid
Rauisuchian
  • Lower Elliot
 A indeterminate large "Rauisuchian"
Sphenosuchus S. acutus
  • Upper Elliot
 A large basal crocodylomorph

Synapsids

Synapsids of the Elliot Formation
Genus Species Location Stratigraphy Notes Images
Elliotherium E. kersteni
  • Lower Elliot
 A tritheledontid cynodont
Megazostrodon M. rudnerae
  • Upper Elliot
 A megazostrodontid cynodont
Pentasaurus P. goggai
  • Lower Elliot
 A stahleckeriid dicynodont
Scalenodontoides S. macrodontes
  • Lower Elliot
 A very large traversodontid cynodont

References

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