Oxford Clay Explained

Oxford Clay
Type:	Geological formation
Age:	Middle to Late Jurassic (Callovian-Oxfordian),
Period:	Oxfordian
Prilithology:	Claystone
Otherlithology:	Mudstone
Namedfor:	Oxford
Region:	Oxford, Peterborough, Dorset, Yorkshire
Country:	England
Unitof:	Ancholme Group
Subunits:	Peterborough Member, Stewartby Member, Weymouth Member
Underlies:	West Walton Formation, Corallian Group
Overlies:	Kellaways Formation, Osgodby Formation
Thickness:	Up to 185 metres, typically 50 to 70 m on East Midlands Shelf

The Oxford Clay (or Oxford Clay Formation) is a Jurassic marine sedimentary rock formation underlying much of southeast England, from as far west as Dorset and as far north as Yorkshire. The Oxford Clay Formation dates to the Jurassic, specifically, the Callovian and Oxfordian ages,^[1] and comprises two main facies. The lower facies comprises the Peterborough Member, a fossiliferous organic-rich mudstone. This facies and its rocks are commonly known as lower Oxford Clay. The upper facies comprises the middle Oxford Clay, the Stewartby Member, and the upper Oxford Clay, the Weymouth Member. The upper facies is a fossil poor assemblage of calcareous mudstones.

Oxford Clay appears at the surface around Oxford, Peterborough and Weymouth and is exposed in many quarries around these areas. The top of the Lower Oxford Clay shows a lithological change, where fissile shale changes to grey mudstone. The Middle and Upper Oxford Clays differ slightly, as they are separated by an argillaceous limestone in the South Midlands.

Palaeontology

The Oxford Clay is well known for its rich fossil record of fish and invertebrates.^[2] Many of the fossils are well preserved, occasionally some are found exceptionally well preserved. Animals which lived in the Oxford Clay Sea include plesiosaurs, marine crocodiles, ichthyosaurs, cephalopods (such as belemnites), bivalves (such as Gryphaea), and a variety of gastropods. Dinosaur eggs are stratigraphically present in the Lower Oxford Clay. Geographically, they are located in Cambridgeshire, England.

Ornithischians

Indeterminate euronithopod remains stratigraphically present in the Lower Oxford Clay and geographically located in Cambridgeshire, England.

Ornithischians of the Oxford Clay
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Callovosaurus	C. leedsi	Cambridgeshire	Lower	"Femur."^[3]	An iguanodontian dryosaur.
Lexovisaurus^[4]	L. durobivensis^[5]	Cambridgeshire^[6] Dorset^[7]	Lower	A holotype pelvis.	A stegosaur
	Indeterminate^[8]	Bedfordshire^[9]
Loricatosaurus	L. priscus	Cambridgeshire	Lower		A stegosaur.
Sarcolestes	S. leedsi	Cambridgeshire	Lower	"Partial mandible."^[10]	An ankylosaur.

Saurischians

Saurischians of the Oxford Clay
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Cetiosauriscus	C. stewarti	Cambridgeshire	Lower	"Rear half of a skeleton."^[11]
Eustreptospondylus^[12]	E. oxoniensis	Oxfordshire	Upper	Disarticulated skull and skeleton, with some referred limb elements.^[13]
Sauropoda	Indeterminate	Wiltshire^[14] Cambridgeshire			The caudal vertebrae from Cambridgeshire were mistakenly considered part of the syntypic series of "Ornithopsis" leedsi by Upchurch and Martin (2003).^[15]
Theropoda	Indeterminate	Oxfordshire	Middle
Metriacanthosaurus	M. parkeri	Weymouth	Upper

Plesiosaurs

Genus	Species	Location	Member	Abundance	Notes	Images
Cryptoclidus	C. eurymerus				A cryptoclidid
	C. richardsoni				A cryptoclidid
Eardasaurus	E. powelli				A thalassophonean pliosaurid
Liopleurodon	L. ferox				A thalassophonean pliosaurid
	L. pachydeirus				A thalassophonean pliosaurid
Marmornectes	M. candrewi				A pliosaurid
Muraenosaurus	M. leedsi				A cryptoclidid
Pachycostasaurus	P. dawnii				A pliosaurid
Peloneustes	P. philarchus				A thalassophonean pliosaurid
Picrocleidus	P. beloclis				A cryptoclidid
Pliosaurus	P. andrewsi				A thalassophonean pliosaurid; represents a new genus distinct from Pliosaurus
Simolestes	S. vorax				A thalassophonean pliosaurid
Tricleidus	T. seeleyi				A cryptoclidid

Pachycormiformes

Genus	Species	Location	Member	Abundance	Notes	Images
Leedsichthys	L. problematicus				Giant filter feeding pachycormiform
Martillichthys	M. renwickae				Filter feeding pachyocormiform
"Hypsocormus"	"H." tenuirostris				Carnivorous pachycormiform, not closely related to Hypsocormus, and more closely related to Orthocormus

Thalattosuchians

Genus	Species	Location	Member	Abundance	Notes	Images
Lemmysuchus	L. obtusidens				A teleosauroid belonging to the Machimosauridae
Charitomenosuchus	C. leedsi				A machimosaurid teleosauroid
Steneosaurus	S. edwardsi				Now referred to Neosteneosaurus.
	S. durobrivensis				Junior synonym of N. edwardsi.
Neosteneosaurus	N. edwardsi				A machimosaurid teleosauroid
Mycterosuchus	M. leedsi				A teleosaurid teleosauroid
Metriorhynchus	M. superciliosus				This species was referred to a new genus, Thalattosuchus.^[16]
Thalattosuchus	T. superciliosus				A metriorhynchine metriorhynchid
Gracilineustes	G. leedsi				A metriorhynchine metriorhynchid
Suchodus	S. brachyrhynchus				A geosaurine metriorhynchid
	S. durobrivensis				A geosaurine metriorhynchid
Tyrannoneustes^[17]	T. lythrodectikos				A geosaurine metriorhynchid

Economic use

Oxford Clay has a porous consistency and is soft and is often used in the making of roads. It is also the source of the Fletton stock brick of which much of London is built. For brick making, the Oxford Clay has the advantage of containing carbon which provides part of the fuel required in firing it so reducing the requirement for an external fuel source.

See also

• List of fossil sites (with link directory)
• List of dinosaur-bearing rock formations
• Kimmeridge Clay
• London Clay
• Weald Clay

References

Bibliography

• Book: . David B. . . Peter . . Halszka . 2004 . The Dinosauria, 2nd edition . Berkeley: University of California Press . 1–880 . 2019-02-21 . 0-520-24209-2.

Further reading

• Andrews, C. W. 1910. "A Descriptive Catalogue of the Marine Reptiles of the Oxford Clay, Part I". British Museum (Natural History), London, England: 205 pp.
• Andrews, CW. 1913. "A descriptive catalogue of the Marine Reptiles of the Oxford Clay, Part II". British Museum (Natural History). pp. 205pp.
• M. J. Benton and P. S. Spencer. 1995. Fossil Reptiles of Great Britain. Chapman & Hall, London 1–386
• J. B. Delair. 1973. "The dinosaurs of Wiltshire". The Wiltshire Archaeological and Natural History Magazine 68:1–7
• P. M. Galton. 1980. "European Jurassic ornithopod dinosaurs of the families Hypsilophodontidae and Camptosauridae". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 160(1):73–95
• D. M. Martill. 1988. "A review of the terrestrial vertebrate of fossils of the Oxford Clay (Callovian-Oxfordian) of England". Mercian Geologist 11(3):171–190

Notes and References

1. Web site: Oxford Clay Formation . . The BGS Lexicon of Named Rock Units . 21 August 2017.
2. Book: Martill , D.M. . Hudson J.D.. 1991. Fossils of the Oxford Clay. Palaeontological Association.
3. "Table 18.1," in Weishampel, et al. (2004). Page 396.
4. Weishampel, et al. (2004). Pages 539-540.
5. "10.7 Dorset, England; 3. Lower Oxford Clay" and "cambridgeshire">"10.9 Cambridgeshire, England; 1. Lower Oxford Clay," in Weishampel, et al. (2004). Pages 539-540.
6. "10.9 Cambridgeshire, England; 1. Lower Oxford Clay," in Weishampel, et al. (2004). Page 540.
7. "10.7 Dorset, England; 3. Lower Oxford Clay," in Weishampel, et al. (2004). Page 539.
8. Listed as "?Lexovisaurus sp." in "10.10 Bedfordshire, England; 1. Oxford Clay," in Weishampel, et al. (2004). Page 540.
9. "10.10 Bedfordshire, England; 1. Oxford Clay," in Weishampel, et al. (2004). Page 540.
10. "Table 17.1," in Weishampel, et al. (2004). Page 367.
11. "Table 13.1," in Weishampel, et al. (2004). Page 265.
12. "10.14 Oxfordshire, England; 8. Middle Oxford Clay," in Weishampel, et al. (2004). Page 540.
13. "Table 4.1," in Weishampel, et al. (2004). Page 72.
14. "10.14 Wiltshire, England; 4. Oxford Clay," in Weishampel, et al. (2004). Page 540.
15. Noé LF, Liston JJ, Chapman SD. 2010. ‘Old bones, dry subject’: the dinosaurs and pterosaur collected by Alfred Nicholson Leeds of Peterborough, England. Geological Society, London, Special Publications 343: 49–77.
16. Young . M.T. . Brignon . A. . Sachs . S. . Hornung . J. . Foffa . D. . Kitson . J.J.N. . Johnson . M.M. . Steel . L. . Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus . Zoological Journal of the Linnean Society . 2021. 192. 2. 510–553. 10.1093/zoolinnean/zlaa092 .
17. Mark T. Young . Marco Brandalise de Andrade . Stephen L. Brusatte . Manabu Sakamoto . Jeff Liston . 2013 . The oldest known metriorhynchid super-predator: a new genus and species from the Middle Jurassic of England, with implications for serration and mandibular evolution in predacious clades . Journal of Systematic Palaeontology . 11 . 4 . 475–513 . 10.1080/14772019.2012.704948. 85276836 .