Editing Gault

{{Short description|Geological formation in England}}
{{about|the clay formation}}
{{Infobox rockunit
| name           = Gault Formation
| image          = Rocks and Rock Pools - geograph.org.uk - 906044.jpg
| caption        = An exposed surface of Gault clay on the foreshore near [[Beachy Head]], [[East Sussex]]
| type           = [[Geological formation]]
| age            = [[Albian]] {{Fossil range|112|100}}
| period         = Albian
| prilithology   = [[Mudstone]], [[clay]]
| otherlithology = [[Limestone]]
| namedfor       = 
| namedby        =
| region         = [[Southern England]]
| country        = England
| coordinates    =
| unitof         = [[Selborne Group]]
| subunits       =
| underlies      = [[Upper Greensand Formation]], [[Cambridge Greensand]], [[Chalk Group]]
| overlies       = [[Monk's Bay Sandstone Formation]],  [[Folkestone Formation]], [[Woburn Sands Formation]], [[Carstone Formation]], overstepping of [[Jurassic]] and [[Triassic]] rocks in Southern England
| thickness      = 2 m in Norfolk to 110 m in the Weald
| extent         =
| area           =
| map            =
| map_caption    =
| location_ts    = Copt Point, [[Folkestone]]
}}
The '''Gault Formation''' is a [[geological formation]] of stiff blue [[clay]] deposited in a calm, fairly deep-water marine environment during the Lower [[Cretaceous]] Period (Upper and Middle [[Albian]]). It is well exposed in the coastal cliffs at [[Copt Point]] in [[Folkestone]], [[Kent]], [[England]], where it overlays the [[Lower Greensand]] formation, and underlies the [[Upper Greensand Formation]].<ref>{{cite web |url=http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=SELB |title=Selborne Group |work=The BGS Lexicon of Named Rock Units |publisher=British Geological Survey |access-date=6 April 2016}}</ref> 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.<ref>{{cite book |last1=Gallois |first1=R.W. |last2=Edmunds |first2=M.A. |edition=4th |date=1965 |title=The Wealden District |series=British Regional Geology series |publisher=British Geological Survey |isbn=0-11-884078-9}}</ref>

The etymology  of the name is uncertain and probably of local origin.<ref name="OED">{{Cite book |title=The Shorter Oxford English Dictionary |publisher=Clarendon Press |year=1973}}</ref>

==Distribution==
It is found in exposure on the south side of the [[North Downs]] and the north side of the [[South Downs]]. It is also to be found beneath the [[escarpment|scarp]] of the [[Berkshire Downs]], in the [[Vale of White Horse]], in [[Oxfordshire]], England, and on the [[Isle of Wight]] where it is known as Blue Slipper.<ref name="IOWBlueSlipper">{{cite news |url=http://www.iwcp.co.uk/news/news/men-rescued-from-mud-31920.aspx |title=Men rescued from mud |first=Martin |last=Neville |newspaper=[[Isle of Wight County Press]] |date=23 March 2010 |access-date=6 April 2016 |archive-date=17 April 2016 |archive-url=https://web.archive.org/web/20160417100236/http://www.iwcp.co.uk/news/news/men-rescued-from-mud-31920.aspx |url-status=dead }}</ref> Gault underlies the chalk beneath the [[London Basin]], generally overlying eroded rocks of [[Jurassic]] 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]] following erosion of the Lower Greensand. It is subdivided into two sections, the Upper Gault and the Lower Gault. The Upper Gault [[onlap]]s onto the Lower Gault. The Gault Formation thins across the [[London Platform]] and then terminates against the [[Hunstanton Formation|Red Chalk]] just to the south of [[The Wash]] in [[East Anglia]].

The Gault exposure at Copt Point, which is the [[type locality (geology)|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 near [[Wye, Kent|Wye]] in [[Kent]].{{cn|date=January 2025}}

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 (mineral)|selenite]] are fairly common in places, as are nodules of [[pyrite]].

==Fossils==
[[File:Hamitidae Fossil in Wear Bay in Folkestone in England.jpg|thumb|[[Hamitidae]] fossil in Gault Clay on a beach in [[Folkestone]], Kent]]
Gault yields abundant marine [[fossil]]s, including [[ammonite]]s (such as ''Hoplites'', ''Hamites'', ''[[Euhoplites]]'', ''Anahoplites'', and ''Dimorphoplites''), [[Belemnoidea|belemnites]] (such as ''Neohibolites''), [[Bivalvia|bivalves]] (such as ''Birostrina'' and ''Pectinucula''), [[Gastropoda|gastropods]] (such as ''Anchura''), solitary [[coral]]s, [[fish]] remains (including [[shark]] teeth), scattered [[crinoid]] remains, and [[crustacean]]s (such as the [[crab]] ''Notopocorystes''). Terrestrial fossils that have been found at Gault include fossil wood, a dinosaur (''[[cf.]]'' ''[[Acanthopholis]]''),<ref>{{cite book|last1=Lomax|first1=Dean R.|last2=Tamura|first2=Nobumichi|year=2014|title=Dinosaurs of the British Isles|publisher=Siri Scientific Press|isbn=9780957453050|at=367}}</ref> and [[pterosaur]]s, including [[Azhdarchoidea|azhdarchoids]], [[Ornithocheiridae|ornithocheirids]], and the indeterminate [[Pterodactyloidea|pterodactyloid]] "Pterodactylus" ''daviesii''.<ref>{{cite journal|last1=Smith|first1=Roy E.|last2=Martill|first2=David M.|year=2022|title=First occurrence of azhdarchoid pterosaurs in the Gault Formation (Lower Cretaceous, Albian) of England, United Kingdom with a brief review of Gault pterosaurs|journal=Proceedings of the Geologists' Association|volume=133|issue=6|pages=491-500|doi=10.1016/j.pgeola.2022.06.003}}</ref> Several pterosaur fossil remains from the overlying [[Cambridge Greensand]] may have been reworked from the underlying Gault.<ref>{{cite journal|last=Unwin|first=D.M.|date=2011-05-11|title=An overview of the pterosaur assemblage from the Cambridge Greensand (Cretaceous) of Eastern England|journal=Fossil Record|volume=4|pages=189-221|doi=10.1002/mmng.20010040112|url=https://onlinelibrary.wiley.com/doi/pdf/10.1002/mmng.20010040112|doi-access=free}}</ref>

==See also==
*[[Argiles du Gault]]

==References==
{{reflist}}

==External links==
* [http://www.gaultammonite.co.uk/  Fossils of the Gault Clay]
* [http://www.discoveringfossils.co.uk/folkestone_fossils.htm Folkestone fossils and geology by Discovering Fossils]

[[Category:Sedimentary rocks]]
[[Category:Cretaceous paleontological sites of Europe]]
[[Category:Geology of England]]
[[Category:Geology of Kent]]
[[Category:Geology of Oxfordshire]]
[[Category:Albian Stage]]
[[Category:Lower Cretaceous Series of Europe]]