The Gault Formation is a geological formation of stiff blue

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...

deposited in a calm, fairly deep-water marine environment during the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Period (Upper and Middle Albian). It is well exposed in the coastal cliffs at

Copt Point Copts ( cop, ⲛⲓⲣⲉⲙⲛ̀ⲭⲏⲙⲓ ; ar, الْقِبْط ) are a Christian ethnoreligious group indigenous to North Africa who have primarily inhabited the area of modern Egypt and Sudan since antiquity. Most ethnic Copts are ...

in Folkestone, Kent,

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

, where it overlays the Lower Greensand formation, and underlies the Upper Greensand Formation. These represent different facies, with the sandier parts probably being deposited close to the shore and the clay in quieter water further from the source of sediment; both are believed to be shallow-water deposits. The etymology of the name is uncertain and probably of local origin.

Distribution

It is found in exposure on the south side of the

North Downs The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. Much of the North Downs comprises two Areas of Outstanding Natural Beauty (AONBs): the Surrey Hills ...

and the north side of the

South Downs The South Downs are a range of chalk hills that extends for about across the south-eastern coastal counties of England from the Itchen valley of Hampshire in the west to Beachy Head, in the Eastbourne Downland Estate, East Sussex, in the eas ...

. It is also to be found beneath the

scarp Scarp may refer to: Landforms and geology * Cliff, a significant vertical, or near vertical, rock exposure * Escarpment, a steep slope or long rock that occurs from erosion or faulting and separates two relatively level areas of differing elevatio ...

of the Berkshire Downs, in the

Vale of White Horse The Vale of White Horse is a local government district of Oxfordshire in England. It was historically a north-west projection of Berkshire. The area is commonly referred to as the 'Vale of ''the'' White Horse'. It is crossed by the Ridgeway Na ...

, in Oxfordshire, England, and on the

Isle of Wight The Isle of Wight ( ) is a county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the largest and second-most populous island of England. Referred to as 'The Island' by residents, the Is ...

where it is known as Blue Slipper. Gault underlies the chalk beneath the London Basin, generally overlying eroded rocks of

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

and Devonian age; lower gault is present only below the outer parts of the basin and is absent under central London. The Gault Formation represents a

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

following erosion of the Lower Greensand. It is subdivided into two sections, the Upper Gault and the Lower Gault. The Upper Gault onlaps onto the Lower Gault. The Gault Formation thins across the London Platform and then terminates against the Red Chalk just to the south of

The Wash The Wash is a rectangular bay and multiple estuary at the north-west corner of East Anglia on the East coast of England, where Norfolk meets Lincolnshire and both border the North Sea. One of Britain's broadest estuaries, it is fed by the riv ...

. The Gault exposure at Copt Point, which is the type locality for the formation, is 40 m in thickness.

Uses

The clay has been used in several locations for making bricks, notably near Dunton Green and Wye in Kent. Gault often contains numerous phosphatic nodules, some thought to be coprolites, and may also contain sand as well as small grains of the mineral glauconite. Crystals of the mineral selenite are fairly common in places, as are nodules of pyrite.

Fossils

Hamitidae Fossil in Wear Bay in Folkestone in England

Gault yields abundant marine

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 ...

s, including ammonites (such as ''Hoplites'', ''Hamites'', '' Euhoplites'', ''Anahoplites'', and ''Dimorphoplites''),

belemnites Belemnites may refer to: *Belemnitida 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. ...

(such as ''Neohibolites''), bivalves (such as ''Birostrina'' and ''Pectinucula''), gastropods (such as ''Anchura''), solitary

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and se ...

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

remains (including

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...

teeth), scattered crinoid remains, and

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s (such as the crab ''Notopocorystes''). Occasional fragments of fossil wood may also be found.

References

{{reflist

External links

Fossils of the Gault Clay

Sedimentary rocks Cretaceous paleontological sites of Europe Geology of England Geology of Kent Geology of Oxfordshire Albian Stage Lower Cretaceous Series of Europe

Distribution

Uses

Fossils

See also

References

External links