Elliot Formation

Lithostratigraphic layer of the Stormberg Group in South Africa From Wikipedia, the free encyclopedia

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 mainly Late Triassic (Norian-Rhaetian) in age while the UEF is mainly Early Jurassic (Hettangian-earliest 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]

Sub-unitsUpper Elliot, Lower Elliot
Quick facts Type, Unit of ...
Elliot Formation
Stratigraphic range: Norian-Pliensbachian
~220–190 Ma
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
Coordinates30.5°S 27.4°E / -30.5; 27.4
Approximate paleocoordinates44.1°S 1.9°W / -44.1; -1.9
RegionEastern Cape, Free State, Mafeteng, Maseru, Quthing, Qacha's Nek & Mohale's Hoek
CountryLesotho
South Africa
Type section
Named forElliot, Eastern Cape
Elliot Formation is located in South Africa
Elliot Formation
Elliot Formation (South Africa)
Close

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.[5][6][4][7]

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.[8][4][9][10][11][12]

Age

U-Pb radiometric dating using zircon grains has refined the duration of the Elliot Formation. Zircons of the Lower Elliot Formation are entirely Late Triassic, ranging from around 220 to 205 million years old (Norian to Rhaetian stages). Zircons of the Upper Elliot are mostly Early Jurassic, ranging from around 202 to 192 million years old (latest Rhaetian to Sinemurian stages). The oldest zircons of the overlying Clarens Formation are about 187 million years old (mid-Pliensbachian stage).[1]

The entire Elliot Formation also preserves a record of magnetostratigraphy, with at least nine reverse-normal polarity chron pairs (EF1r to EF9n). The lower-upper Elliot boundary is in the middle of chron EF6n. The Elliot Formation's magnetostratigraphy can be partially correlated with similar records in the Newark Basin (northeast United States), Chinle and Moenave formations (southwest United States), and Los Colorados Formation (Argentina).[7][1]

Paleontology

The Elliot Formation is well known for its diverse fossils of dinosaur and other vertebrates. The formation is divided into two biozones, the Scalenodontoides Assemblage Zone and Massospondylus Assemblage Zone. The Scalenodontoides Assemblage Zone corresponds to the Lower Elliot Formation. Formerly known as the 'Euskelosaurus' Range Zone, its index taxa include the cynodont Scalenodontoides and the sauropodomorphs Blikanasaurus and Melanorosaurus.[13] The Massospondylus Assemblage Zone extends from the Upper Elliot Formation into the Clarens Formation. Its index taxa include the sauropodomorph Massospondylus, the ornithischian Lesothosaurus, and the crocodylomorph Protosuchus.[14]

Sauropodomorphs are particularly diverse in the Elliot Formation.[15][16][17][18] The most common dinosaur is a sauropodomorph species, Massospondylus carinatus.[19][20] Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park.[21][22]

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.[23][24][25][26]

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

More information Ornithischians of the Elliot Formation, Genus / Taxon ...
Ornithischians of the Elliot Formation
Genus / Taxon Species Location Stratigraphy Assemblage Zone Materials Notes Images
Abrictosaurus A. consors Qacha's Nek, Lesotho Upper Elliot Massospondylus Several specimens consist of a partial skull and partial skeleton A heterodontosaurid, formerly species of Lycorhinus
Eocursor E. parvus Free State, South Africa Upper Elliot Massospondylus A partial skeleton consists of skull portions, lower jaw, vertebrae, and limbs A basal ornithischian
Fabrosaurus F. australis Likhoele, Lesotho Upper Elliot Massospondylus Partial jaw and dentary A basal ornithischian, nomen dubium
Heterodontosaurus H. tucki Tushielaw Farm, Tyindini, and Krommespruit of South Africa Upper Elliot Massospondylus Multiple specimens A heterodontosaurid
Lesothosaurus L. diagnosticus Multiple localities found in Lesotho and South Africa Upper Elliot Massospondylus A partial skull A basal neornithischian or thyreophoran, formerly considered a species of Fabrosaurus.[27] Larger Lesothosaurus specimens are sometimes given the name Stormbergia.[28]
Lycorhinus L. angustidens Paballong and Buck Camp of South Africa Upper Elliot Massospondylus Specimens consist of mandibles and dentaries. A heterodontosaurid
Moyenisauropus M. sp. Moyeni Tracksite, South Africa Upper Elliot Massospondylus Multiple Footprints Large ornithischian footprints similar to Anomoepus.[29]
Pegomastax P. africana Krommespruit, Voisana Upper Elliot Massospondylus A partial skull A heterodontosaurid
Thyreophora indet. Upper Elliot Massospondylus Scute specimen Known from scutes[30]
Trisauropodiscus T. aviforma Maphutseng II tracksite, Lesotho Lower–Upper Elliot Massospondylus Footprints Very small bird-like dinosaur footprints, potentially produced by theropods or heterodontosaurid ornithischians.[31]
Close

Sauropodomorphs

More information Prosauropods of the Elliot Formation, Genus ...
Prosauropods of the Elliot Formation
Genus Species Location Stratigraphy Assemblage Zone Materials Notes Images
Aardonyx[32] A. celestae Marc's Quarry bone bed Upper Elliot Massospondylus A partial skeleton consists of cranial elements, vertebrae, dorsal and cervical ribs, gastralia, chevrons, elements of the pectoral and pelvic girdles, and several limb bones. A derived sauropodomorph
Antetonitrus[33] A. ingenipes Welbedacht/Edelweiss Upper Elliot Massospondylus A partial skeleton A lessemsaurid, either a derived sauropodomorph or basal sauropod.[34]
Arcusaurus[35] A. pereirabdalorum Spion Kop Heelbo Upper Elliot Massospondylus A partial skull A basal sauropodomorph, known from juveniles
Blikanasaurus[36] B. cromptoni Blikana Mountain Lower Elliot Scalenodontoides A partial hindlimb A derived sauropodomorph or basal sauropod.[37]
Eucnemesaurus E. entaxonis Cannon Rock Farm Lower Elliot Scalenodontoides A set of postcrania consists of the posteriormost dorsal vertebrae, sacrum, anterior caudal vertebrae, pelvis, and hindlimb A possible riojasaurid
E. fortis Sonderhout A partial skeleton
Euskelosaurus E. browni Lower Elliot Scalenodontoides A plateosaurid, potentially dubious
Gryponyx G. africanus Upper Elliot Massospondylus A massospondylid, potentially dubious
Ignavusaurus I. rachelis Upper Elliot Massospondylus A massospondylid, known from a juvenile. A potential synonym of Massospondylus
Kholumolumo K. ellenbergerorum Thotobolo ea 'Ma-beata Lower Elliot Scalenodontoides A limb bone consisted of a right tibia A basal massopodan.
Ledumahadi[38] L. mafube Upper Elliot Massospondylus A lessemsaurid, either a derived sauropodomorph or basal sauropod. The largest dinosaur in the formation.[38][39]
Massospondylus M. carinatus Upper Elliot Massospondylus A massospondylid, the most common dinosaur in the formation.[19][20]
M. kaalae A massospondylid which differs from M. carinatus in cranial features
Melanorosaurus M. readi Thaba 'Nyama Lower Elliot Scalenodontoides A derived sauropodomorph
Meroktenos M. thabanensis Thabana Morena Lower Elliot Scalenodontoides A thighbone or femur and other assorted bones A derived sauropodomorph, formerly a species of Melanorosaurus
Plateosauravus P. cullingworthi Kromme Spruit Lower Elliot Scalenodontoides A partial skeleton A basal sauropodomorph, formerly specimens of Euskelosaurus
Pseudotetrasauropus P. bipedoida Lower Elliot Scalenodontoides Large bipedal sauropodomorph footprints.[40][41]
P. jaquesi Lower Elliot Scalenodontoides Footprints Large quadrupedal sauropodomorph footprints, sometimes considered a species of Lavinipes.[41]
Pulanesaura P. eocollum Sauropod Quarry Upper Elliot Massospondylus Several materials consist of two isolated teeth, a middle cervical vertebra, five back vertebral arches, a single right dorsal rib, three tail vertebrae, a left clavicle, a distal right humerus, a left ulna, possibly the fourth right middle hand bone, three ischia, a left and a right shinbone, and two hindlimb first claws. A derived sauropodomorph or basal sauropod
Sefapanosaurus S. zastronensis Zastron Lower Elliot? Scalenodontoides A set of limb elements consists of an incomplete, articulated left pes A derived sauropodomorph
Tetrasauropus T. unguiferus Lower Elliot Scalenodontoides Large quadrupedal sauropodomorph footprints.[40][41]
Close

Theropods

Large theropod-like teeth have been found in the Lower Elliot Formation.[42] Various exposures of the formation (primarily in Lesotho) preserve informative interactions between theropod trackmakers and soft sediment.[43][44][45][46]

More information Theropods of the Elliot Formation, Genus ...
Theropods of the Elliot Formation
Genus Species Location Stratigraphy Assemblage Zone Materials Notes Images
Dracovenator[47] D. regenti Upper Drumbo Farm Upper Elliot Massospondylus A partial skull A large neotheropod, potentially close to Dilophosaurus.
Eubrontes E. sp. Lower–Upper Elliot Scalenodontoides—Massospondylus Footprints Large theropod footprints.
Grallator G. sp. Lower–Upper Elliot Scalenodontoides—Massospondylus Footprints Small theropod footprints.
Kayentapus K. ambrokholohali Upper Elliot Massospondylus Footprints Very large theropod footprints. The largest prints, measuring 57 cm (22 in) in length, may belong to a theropod up to 9 m (30 ft) long.[44][48]
Megapnosaurus M. rhodesiensis Syntarsus site Upper Elliot Massospondylus A well-preserved postcranial skeleton, missing only the skull and cervical vertebrae A coelophysid, also known as Syntarsus.
Close

Pseudosuchians

More information Pseudosuchians of the Elliot Formation, Genus / Taxon ...
Pseudosuchians of the Elliot Formation
Genus / Taxon Species Location Stratigraphy Assemblage Zone Materials Notes Images
Basutodon B. ferox Lower Elliot Scalenodontoides A dubious archosaur based on a "rauisuchian"-like tooth.[49]
Batrachopus Upper Elliot Massospondylus Small crocodylomorph footprints.[50][25]
Brachychirotherium B. cf. thuringiacum Lower Elliot Scalenodontoides Large "chirothere" footprints.[50][40][1]
Litargosuchus[51] L. leptorhynchus Eagles Crag Farm Upper Elliot Massospondylus A basal crocodylomorph
Orthosuchus O. stormbergi Upper Elliot Massospondylus A possible protosuchid crocodylomorph.[52][53][54]
Paratetrasauropus P. seakensis Lower Elliot Scalenodontoides Large crocodilian-like footprints, probably from crocodylomorphs.[40]
Poposauroidea indet. Lower Elliot An indeterminate poposauroid.[49]
Protosuchus P. haughtoni Upper Elliot Massospondylus A protosuchid crocodylomorph.
Rauisuchia indet. Lower Elliot Scalenodontoides A indeterminate large "rauisuchian" (non-crocodylomorph loricatan). Many "rauisuchian" fossils have been found in the formation,[49] including very large limb bones from near Qhemegha, Eastern Cape.[55] A large toothed maxilla, formerly considered part of "Aliwalia rex", may be rauisuchian in origin.[1] Large Indeterminate loricatan partial maxilla
Sauropodopus S. antiquus Lower Elliot Scalenodontoides Large Brachychirotherium-like footprints with a narrow gait.[50][40]
Sphenosuchus S. acutus Upper Elliot Massospondylus A basal crocodylomorph.[56]
Close

Other reptiles

More information Other reptiles of the Elliot Formation, Genus ...
Other reptiles of the Elliot Formation
Genus Species Location Stratigraphy Assemblage Zone Materials Notes Images
Australochelys A. africanus Upper Elliot Massospondylus An australochelyid testudinate (early turtle).[57]
Clevosaurus C. sp. Upper Elliot Massospondylus An clevosaurid rhynchocephalian.[58]
Close

Synapsids

A possible late-surviving diademodontid cynodont may be present in the Upper Elliot Formation.[59][1]

More information Synapsids of the Elliot Formation, Genus ...
Synapsids of the Elliot Formation
Genus Species Location Stratigraphy Assemblage Zone Materials Notes Images
Ameghinichnus A. sp. Upper Elliot Massospondylus Tritylodontid cynodont footprints.[50]
Diarthrognathus D. broomi Upper Elliot Massospondylus A tritheledontid cynodont
Elliotherium[60] E. kersteni Upper Elliot[1] Massospondylus A tritheledontid cynodont
Erythrotherium E. parringtoni Upper Elliot Massospondylus A mammaliaform cynodont
Megazostrodon M. rudnerae Upper Elliot Massospondylus A megazostrodontid mammaliaform cynodont.[61]
Pachygenelus P. monus Upper Elliot Massospondylus A tritheledontid cynodont
Pentasauropus P. incredibilis Lower Elliot Scalenodontoides Dicynodont footprints
Pentasaurus[62] P. goggai Lower Elliot Scalenodontoides A stahleckeriid dicynodont, undoubtedly the trackmaker of Pentasauropus.[62]
Scalenodontoides S. macrodontes Lower Elliot Scalenodontoides A very large traversodontid cynodont
Tritheledon T. riconoi Upper Elliot Massospondylus A tritheledontid cynodont
Tritylodon T. longaevus Upper Elliot Massospondylus A tritylodontid cynodont
Close

Other vertebrates

More information Amphibians and fish of the Elliot Formation, Genus / Taxon ...
Amphibians and fish of the Elliot Formation
Genus / Taxon Species Location Stratigraphy Assemblage Zone Materials Notes Images
Brachyopoidea Quthing, Lesotho[63] Upper Elliot[1] Massospondylus An enormous brachyopoid amphibian based on a skull fragment. Potentially the largest amphibian that has ever lived.[63]
Ceratodus C. sp. Lower–Upper Elliot Scalenodontoides—Massospondylus A ceratodontid lungfish.
Chigutisauridae Lower–Upper Elliot Scalenodontoides—Massospondylus Indeterminate chigutisaurid amphibians.
Daedalichthys D. formosa Upper Elliot Massospondylus A redfieldiiform ray-finned fish, previously identified as Helichthys.
Endemichthys E. likhoeli Upper Elliot Massospondylus A redfieldiiform ray-finned fish.
Episcopopus E. ventrosus Upper Elliot Massospondylus Very large amphibian footprints.[64]
Semionotus S. capensis Upper Elliot Massospondylus A semionotid ray-finned fish.
Close

References

Related Articles

Wikiwand AI