Magnesian Conglomerate

Magnesian Conglomerate
Stratigraphic range: Rhaetian ~208–202 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Slickstones Quarry, where an outcrop of the Magnesian Conglomerate is present
Type	Geological formation, fissure fill
Underlies	none
Overlies	Friars Point Limestone Formation?
Lithology
Primary	Breccia
Other	Limestone
Location
Coordinates	51°30′N 2°36′W / 51.5°N 2.6°W / 51.5; -2.6
Approximate paleocoordinates	35°54′N 0°48′E / 35.9°N 0.8°E / 35.9; 0.8
Region	South West England & South Wales
Country	England
Extent	Bristol
Type section
Named by	Henry Riley & Samuel Stutchbury
Year defined	1836
Magnesian Conglomerate (England)

The Magnesian Conglomerate is a geological formation in Clifton, Bristol in England (originally Avon), Gloucestershire and southern Wales, present in Tytherington, Durdham Down, Slickstones Quarry and Cromhall Quarry.

It dates back to the Rhaetian stage of the Late Triassic,^[1][2] although it may be as old as the Norian stage of the Late Triassic and as young as the Hettangian stage of the Early Jurassic.^{[citation needed]}

The Magnesian Conglomerate was first discovered in autumn 1834 and was studied in 1836 by Henry Riley and Samuel Stutchbury.^[3]

The Avon Fissure Fill is often paired with the Magnesian Conglomerate.^[1]

Vertebrate paleofauna^[1]

Taxon	Species	Presence	Notes	Images
Actinopteri[4]	Indeterminate[4]	Geographically present in Durdham Down.[4]	A tooth.[4]
Agnosphitys[2][5]	A. cromhallensis[2][5]	Geographically present in Avon, England (now Bristol).[2]	Its remains include a left ilium (holotype) and a left maxilla, astragalus and humerus (referred specimen).[2]
Agrosaurus[6][2]	A. macgillivrayi[6][2]	Geographically present in Avon, England (now Bristol). Originally believed to have been found in Cape York Peninsula, Queensland (Australia).[2]	A tibia, a claw and some other fragments.[2]
Archosauria[7]	Indeterminate[7]	Geographically present in Durdham Down.[4]	Five specimens, including jaw fragments, caudals, and a scapulocoracoid.[7]
Archosauromorpha[4]	Indeterminate[4]	Geographically present in Durdham Down.[4]	A fragment of a small tooth.[4]
Asylosaurus[2][8]	A. yalensis[2][8]	Geographically present in Avon, England (now Bristol).[2][9]	Dorsal vertebrae, ribs, gastralia, a shoulder girdle, humeri, a partial forearm, and a hand; additional bones from the neck, tail, pelvis, arm and legs that may represent the same individual.[8][2]
Chimaeriformes[10]	Indeterminate[10]	Geographically present in Bristol.[2]	Indeterminate remains.[10]
Clevosaurus[11]	C. hudsoni[11]	Geographically present in Gloucestershire.[2]	Partial cranial and post-cranial skeleton (holotype).[11]
Crinoidea[10]	Indeterminate[10]	Geographically present in Bristol.[2]	Reworked from older Carboniferous sediments (Friars Point Limestone Formation).[12]
Cryptovaranoides[13]	C. microlanius[14]	Geographically present in Slickstones Quarry.[15]	Holotype (partial skeleton) and referred isolated remains.[16]
Diphydontosaurus[10]	D. avonensis[10]	Geographically present in Bristol.[2]	Complete to near-complete specimens.[10]
Herrerasauria?[8]	Indeterminate[8]	Geographically present in Durdham Down.[4]	3 indeterminate specimens.[8]
Hwiccewyrm[17]	H. trispiculum[17]	Geographically present in Slickstones Quarry.[17]	Several specimens comprising a partial skeleton.[17] Discovered during the 1970s and listed as cf. Hypsognathus by Whiteside et al. (2016).[18]
Hybodontiformes?[4]	Indeterminate[4]	Geographically present in Bristol.[2]	Indeterminate remains.[4]
Gyrolepis[19]	Indeterminate[19]	Geographically present in Bristol.[2]	Indeterminate remains.[19]
Kuehneosauridae[4]	Indeterminate[4]	Geographically present in Durdham Down.[4]	Rib that may instead be an ulna belonging to Terrestrisuchus.[4]
Lissodus[4]	L. minimus[4]	Geographically present in Bristol.[2]	Teeth.[4]
Ornithischia[8]	Indeterminate[8]	Geographically present in Durdham Down.[4]	Indeterminate specimen.[8]
Palaeosaurus[2][8]	P. cylindrodon[2][8]	Geographically present in Avon, England (now Bristol) and Bristol.[2]	Two teeth (one destroyed in 1940).[2]
Phytosauria[4]	Indeterminate[4]	Geographically present in Durdham Down.[4]	Two teeth previously assigned to Mystriosuchinae.[4]
Planocephalosaurus[20][21]	P. robinsonae[20][21]	Geographically present in Bristol.[2]	Skull (holotype) and a tooth.[20]
Plateosauria[22]	Indeterminate[22]	Geographically present in Durdham Down.[4]	22 partial specimens.[22]
Rhomphaiodon[4]	R. minor[4]	Geographically present in Bristol.[2]	Teeth, including the subsidiary cusp of one tooth.[4]
Rileyasuchus[2][23][24]	R. bristolensis[2][23][24]	Geographically present in Bristol.[2]	Two vertebrae and a humerus.[2]
Sauropodomorpha[8]	Indeterminate[8]	Geographically present in Durdham Down.[4]	Indeterminate remains.[8]
Sphenosuchia[4]	Indeterminate[4]	Geographically present in Durdham Down.[4]	A right femur initially named as Thecodontosaurus costa.[4]
Terrestrisuchus[4][10]	T. gracilis and indeterminate[4][10]	Geographically present in Bristol and South Wales.[2]	Indeterminate and partial remains.[4][10]
Theropoda[2]	Indeterminate[2]	Geographically present in Avon, England (now Bristol) and Bristol.[2]	A tooth, and a tibia that was once allied with Thecodontosaurus.[2][8] Possibly similar to Pendraig milnerae.[25]
Thecodontosaurus[2]	T. antiquus[2]	Geographically present in Avon, England (now Bristol) and Bristol.[2]	Partial cranial and postcranial remains (holotype is a lower jaw).[2]

See also

• List of dinosaur-bearing rock formations
• List of fossiliferous stratigraphic units in England

References

Bibliography

• Foffa, D.; D. I. Whiteside; P. A. Viegas, and M. J. Benton. 2014. Vertebrates from the Late Triassic Thecodontosaurus-bearing rocks of Durdham Down, Clifton (Bristol, UK). Proceedings of the Geologists' Association 125. 317–332. .
• Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2
• Riley, H., and S. Stutchbury. 1836. A description of various fossil remains of three distinct saurian animals discovered in the autumn of 1834 in the Magnesian Conglomerate on Durdham Down near Bristol. Proceedings of the Geological Society 2. 397–399. .

Further reading

• Riley, H. and Stutchbury, S. 1840. A description of various fossil remains of three distinct saurian animals recently discovered in the Magnesian Conglomerate near Bristol Transactions of the Geological Society of London 5, 349–357
• W. Buckland. 1824. Reliquiæ Diluvianæ; or, Observations on the Organic Remains Contained in Caves, Fissures, and Diluvial Gravel, and on Other Geological Phenomena, Attesting the Action of an Universal Deluge. Second Edition. John Murray, London 1-303

External links

• British Geological Survey Lexicon of Named Rock Units

This page was last edited on 23 January 2024, at 20:09