The Cornbrash Formation is a

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...

geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in England. It ranges in age from

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. ...

to Callovian, the uppermost part of the Middle Jurassic.

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607. The name Cornbrash is an old English agricultural name applied in

Wiltshire Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire ...

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 Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

which, in the south of England, breaks up in the manner indicated. Although only a thin group of rocks (10–25 feet c. 3–7 m), it is remarkably persistent; it may be traced from Weymouth to the

Yorkshire Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...

coast, but in

north Lincolnshire North Lincolnshire is a unitary authority area in Lincolnshire, England, with a population of 167,446 in the 2011 census. The borough includes the towns of Scunthorpe, Brigg, Haxey, Crowle, Epworth, Bottesford, Kirton in Lindsey and Bar ...

it is very thin, and probably dies out in the neighborhood of the

Humber The Humber is a large tidal estuary on the east coast of Northern England. It is formed at Trent Falls, Faxfleet, by the confluence of the tidal rivers Ouse and Trent. From there to the North Sea, it forms part of the boundary between ...

. 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

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...

s 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 Bedfordshire (; abbreviated Beds) is a ceremonial county in the East of England. The county has been administered by three unitary authorities, Borough of Bedford, Central Bedfordshire and Borough of Luton, since Bedfordshire County Council ...

it has been termed the Bedford limestone.

Fossils

The Cornbrash is a very

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

iferous formation; the fauna indicates a transition from the Lower to the Middle

Oolite Oolite or oölite (''egg stone'') is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Ancient Greek word for egg (ᾠόν). Strictly, oolites consist of ooids of diameter 0.25� ...

s, though it is probably more nearly related to that of the beds above than to those below. Good localities for fossils are

Radipole Radipole was is a suburb of Weymouth in Dorset, England. History It was formerly an independent parish, until abolished as a separate local government unit in 1933. It remains a separate ecclesiastical parish. Radipole stands at the head of, an ...

near Weymouth,

Closworth Closworth is a village and civil parish in Somerset, England, south of Yeovil in the South Somerset district, on the border with Dorset. The village has a population of 220. The parish includes the villages of Pendomer and Sutton Bingham, the ...

, Wincanton, Trowbridge,

Cirencester Cirencester (, ; see below for more variations) is a market town in Gloucestershire, England, west of London. Cirencester lies on the River Churn, a tributary of the River Thames, and is the largest town in the Cotswolds. It is the home of ...

Witney Witney is a market town on the River Windrush in West Oxfordshire in the county of Oxfordshire, England. It is west of Oxford. The place-name "Witney" is derived from the Old English for "Witta's island". The earliest known record of it is as ...

Peterborough Peterborough () is a cathedral city in Cambridgeshire, east of England. It is the largest part of the City of Peterborough unitary authority district (which covers a larger area than Peterborough itself). It was part of Northamptonshire unti ...

and Sudbrook Park near Lincoln. A few of the important fossils are: '' Waldheimia lagenalis'', '' Pecten levis'', '' Avicula echinata'', '' Ostrea fiabelloides'', '' Mycicites decurtatus'', '' Echinobrissus clunicularis''. '' Macrocephalites macrocephalus '' is abundant in the midland counties but rarer in the south;

belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

s are not known. Indeterminate

stegosauria Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europ ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

material (sometimes known under the ''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate desc ...

'' " Eoplophysis") have been discovered in this formation. The teleosaurid crocodyliformes ''

Yvridiosuchus ''Yvridiosuchus'' (meaning "hybrid crocodile") is an extinct genus of machimosaurid crocodyliform from the Middle Jurassic (Bathonian) Cornbrash Formation of England and the '' Sommet de la Grande Oolithe'', Calvados Calvados (, , ) is a ...

, '' Seldsienean, '' Clovesuurdameredeor'' and '' Deslongchampsina'' are known from the formation.

Footnotes

References

* Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. . * Historical geology Stratigraphy of the United Kingdom Geology of England Bathonian Stage Callovian Stage {{UK-geologic-formation-stub

Fossils

See also

Footnotes

References