Oxford Clay
Stratigraphic range: Middle to Late Jurassic (Callovian-Oxfordian), 166–160 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Coastal exposure of the Oxford Clay Formation near Weymouth
Type	Geological formation
Unit of	Ancholme Group
Sub-units	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
Lithology
Primary	Claystone
Other	Mudstone
Location
Region	Oxford, Peterborough, Dorset, Yorkshire
Country	England
Type section
Named for	Oxford

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.^[3]

Ornithischians

Indeterminate euronithopod remains stratigraphically present in the Lower Oxford Clay and geographically located in Cambridgeshire, England.^[3]

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

Saurischians

Saurischians of the Oxford Clay
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Cetiosauriscus[3]	C. stewarti[3]	Cambridgeshire[3]	Lower[3]	"Rear half of a skeleton."[11]
Eustreptospondylus[12]	E. oxoniensis[12]	Oxfordshire[12]	Upper[12]	Disarticulated skull and skeleton, with some referred limb elements.[13]
Sauropoda	Indeterminate[14]	Wiltshire[14] Cambridgeshire[3]			The caudal vertebrae from Cambridgeshire were mistakenly considered part of the syntypic series of "Ornithopsis" leedsi by Upchurch and Martin (2003).[15]
Theropoda	Indeterminate[12]	Oxfordshire[12]	Middle[12]
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

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.