Oxford Clay | |
---|---|
Stratigraphic range: Middle to Late Jurassic (Callovian-Oxfordian), | |
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.
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]
Indeterminate euronithopod remains stratigraphically present in the Lower Oxford Clay and geographically located in Cambridgeshire, England. [3]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Ornithischians of the Oxford Clay | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
C. leedsi [3] |
| Lower [3] | "Femur." [4] | An iguanodontian dryosaur. | ||
L. durobivensis [6] | Lower [6] | A holotype pelvis. | A stegosaur | |||
Indeterminate [8] |
| |||||
L. priscus [3] |
| Lower [3] | A stegosaur. | |||
S. leedsi [3] |
| Lower [3] | "Partial mandible." [10] | An ankylosaur. |
Color key
| Notes Uncertain or tentative taxa are in small text; |
Saurischians of the Oxford Clay | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
C. stewarti [3] |
| Lower [3] | "Rear half of a skeleton." [11] | |||
E. oxoniensis [12] |
| Upper [12] | Disarticulated skull and skeleton, with some referred limb elements. [13] | |||
Indeterminate [14] | The caudal vertebrae from Cambridgeshire were mistakenly considered part of the syntypic series of "Ornithopsis" leedsi by Upchurch and Martin (2003). [15] | |||||
Indeterminate [12] |
| Middle [12] | ||||
M. parkeri |
| Upper |
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Location | Member | Abundance | Notes | Images |
---|---|---|---|---|---|---|
C. eurymerus | ||||||
C. richardsoni | A cryptoclidid | |||||
Eardasaurus | E. powelli | |||||
L. ferox | ||||||
L. pachydeirus | A thalassophonean pliosaurid | |||||
M. candrewi | A pliosaurid | |||||
M. leedsi | A cryptoclidid | |||||
P. dawnii | A pliosaurid | |||||
P. philarchus | A thalassophonean pliosaurid | |||||
P. beloclis | A cryptoclidid | |||||
P. andrewsi | A thalassophonean pliosaurid; represents a new genus distinct from Pliosaurus | |||||
S. vorax | A thalassophonean pliosaurid | |||||
T. seeleyi | A cryptoclidid | |||||
Color key
| Notes Uncertain or tentative taxa are in small text; |
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 | ||||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Location | Member | Abundance | Notes | Images |
---|---|---|---|---|---|---|
L. obtusidens | A teleosauroid belonging to the Machimosauridae | |||||
C. leedsi | A machimosaurid teleosauroid | |||||
S. edwardsi | Now referred to Neosteneosaurus. | |||||
S. durobrivensis | Junior synonym of N. edwardsi. | |||||
N. edwardsi | A machimosaurid teleosauroid | |||||
M. leedsi | A teleosaurid teleosauroid | |||||
M. superciliosus | This species was referred to a new genus, Thalattosuchus. [16] | |||||
T. superciliosus | ||||||
G. leedsi | A metriorhynchine metriorhynchid | |||||
S. brachyrhynchus | A geosaurine metriorhynchid | |||||
S. durobrivensis | A geosaurine metriorhynchid | |||||
T. lythrodectikos | A geosaurine metriorhynchid | |||||
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.
Weald Clay or the Weald Clay Formation is a Lower Cretaceous sedimentary rock unit underlying areas of South East England, between the North and South Downs, in an area called the Weald Basin. It is the uppermost unit of the Wealden Group of rocks within the Weald Basin, and the upper portion of the unit is equivalent in age to the exposed portion of the Wessex Formation on the Isle of Wight. It predominantly consists of thinly bedded mudstone. The un-weathered form is blue/grey, and the yellow/orange is the weathered form, it is used in brickmaking.
Callovosaurus is a genus of iguanodontian dinosaur known from most of a left thigh bone discovered in Middle Jurassic-age rocks of England. At times, it has been considered dubious or a valid genus of basal iguanodontian, perhaps a dryosaurid.
The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group in south-east England. The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in the cliffs west of Swanage.
Ornithopsis is a genus of sauropod dinosaur, from the Early Cretaceous of England. The type species, which is the only species seen as valid today, is O. hulkei, which is only known from fragmentary remains, and has been regarded by many authors as dubious.
The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for North Sea oil. The fossil fauna of the Kimmeridge Clay includes turtles, crocodiles, sauropods, plesiosaurs, pliosaurs and ichthyosaurs, as well as a number of invertebrate species.
The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group in the lithostratigraphy of southern England. The Wealden group consists of paralic to continental (freshwater) facies sedimentary rocks of Berriasian to Aptian age and thus forms part of the English Lower Cretaceous. It is composed of alternating sands and clays. The sandy units were deposited in a flood plain of braided rivers, the clays mostly in a lagoonal coastal plain.
The Tendaguru Formation, or Tendaguru Beds are a highly fossiliferous formation and Lagerstätte located in the Lindi Region of southeastern Tanzania. The formation represents the oldest sedimentary unit of the Mandawa Basin, overlying Neoproterozoic basement, separating by a long hiatus and unconformity. The formation reaches a total sedimentary thickness of more than 110 metres (360 ft). The formation ranges in age from the late Middle Jurassic to the Early Cretaceous, Oxfordian to Hauterivian stages, with the base of the formation possibly extending into the Callovian.
The Wessex Formation is a fossil-rich English geological formation that dates from the Berriasian to Barremian stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Formation and overlies the Durlston Formation. The dominant lithology of this unit is mudstone with some interbedded sandstones. It is part of the strata of the Wessex Basin, exposed in both the Isle of Purbeck and the Isle of Wight. While the Purbeck sections are largely barren of vertebrate remains, the Isle of Wight sections are well known for producing the richest and most diverse fauna in Early Cretaceous Europe.
The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago. The Blue Lias is famous for its fossils, especially ammonites.
The Marnes de Dives is a geological formation in Normandy, France. It dates back to the upper part of the Callovian stage of the Middle Jurassic. And is partially equivalent to the Oxford Clay in England. It predominantly consists of ooidal marl, rich in pyrite and lignite, interbedded with thin limestone horizons. It is best exposed at the base of the Falaises des Vaches Noires as well as the foreshore at low tide. It is known for its fossils, notably those of ammonites, marine crocodiles and fragmentary remains of dinosaurs, mostly theropods.
The Inferior Oolite is a sequence of Jurassic age sedimentary rocks in Europe. It was deposited during the Middle Jurassic. The Inferior Oolite Group as more recently defined is a Jurassic lithostratigraphic group in southern and eastern England. It has been variously known in the past as the Under Oolite, the Inferior Oolite, the Inferior Oolite Series and the Redbourne Group.
The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.
The Shishugou Formation is a geological formation in Xinjiang, China.
The Cornbrash Formation is a Middle Jurassic geological formation in England. It ranges in age from Bathonian to Callovian, the uppermost part of the Middle Jurassic. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. The name Cornbrash is an old English agricultural name applied in Wiltshire to a variety of loose rubble or brash which, in that part of the country, forms a good soil for growing corn. The name was adopted by William Smith for a thin band of shelly limestone which, in the south of England, breaks up in the manner indicated. Although only a thin group of rocks, it is remarkably persistent; it may be traced from Weymouth to the Yorkshire coast, but in north Lincolnshire it is very thin, and probably dies out in the neighborhood of the Humber. It appears again, however, as a thin bed in Gristhorpe Bay, Cayton Bay, Wheatcroft, Newton Dale and Langdale. In the inland exposures in Yorkshire it is difficult to follow on account of its thinness, and the fact that it passes up into dark shales in many places the so-called clays of the Cornbrash, with Avicula echinata. The Cornbrash is of little value for building or road-making, although it is used locally; in the south of England it is not oolitic, but in Yorkshire it is a rubbly, marly, frequently ironshot oolitic limestone. In Bedfordshire it has been termed the Bedford limestone.
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The Ornatenton Formation is a Jurassic marine formation in Germany that is middle Callovian in age. The formation represents a shallow marine environment.
The Coralline Oolite Formation is a limestone formation of Oxfordian age, found in the Cleveland Basin of North Yorkshire, England.