Elliot Formation

Elliot Formation
Stratigraphic range: Norian-Pliensbachian ~220–190 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Elliot Formation caves in the Matalane Valley, Leribe, Lesotho
Type	Geological formation
Unit of	Stormberg Group
Sub-units	Upper Elliot, Lower Elliot
Underlies	Clarens Formation
Overlies	Molteno Formation
Thickness	up to 500 m (1,600 ft)
Lithology
Primary	Mudstone, sandstone
Other	Siltstone, conglomerate
Location
Coordinates	30°30′S 27°24′E / 30.5°S 27.4°E / -30.5; 27.4
Approximate paleocoordinates	44°06′S 1°54′W / 44.1°S 1.9°W / -44.1; -1.9
Region	Eastern Cape, Free State, Mafeteng, Maseru, Quthing, Qacha's Nek & Mohale's Hoek
Country	Lesotho  South Africa
Type section
Named for	Elliot, Eastern Cape
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-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.^[1] 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.^[2][3][4]

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.^[5][6][7][8]

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.^{[9][10][11][12][13][14]}

The Elliot Formation is well known for its diverse dinosaur fossils. The most common dinosaur species is of the sauropodomorph species Massospondylus carinatus.^[15][16] Other species include Blikanasaurus cromptoni, Aardonyx celestae, Euskelosaurus browni, Antetonitrus ingenipes, Pulanesaura eocollum, and the largest sauropodomorph yet found, Ledumahadi mafube.^{[17][18][19][20][21][22][23][24]} Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park.^[25][26] 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.^[27][28] In addition this formation has yielded various crocodylomorph species,^[29] namely Litargosuchus leptorhynchus, Sphenosuchus acutus and Orthosuchus stormbergi.^{[30][31][32][33]} A large theropod dinosaur, Dracovenator regenti, has been found in the UEF.^[34] Synapsids from the formation include the dicynodont Pentasaurus goggai^[35] the tritheledontid cynodont Elliotherium kersteni^[36][37] and the mammaliaform Megazostrodon rudnerae.^[38] 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.^{[39][40][41][42]}

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 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 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

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 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