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Weald Clay

Geological formation in England

Field	Value
name	Weald Clay
image	Clay Pit, Clock House, near Capel - geograph.org.uk - 1779315.jpg
caption	Weald Clay exposed at Clock House Brickworks
type	Geological formation
age	Hauterivian-Barremian,
period	Barremian
prilithology	Shale, Mudstone
otherlithology	Siltstone, Sandstone, Limestone, Ironstone
namedfor	Weald
region	England
country	United Kingdom
unitof	Wealden Group
subunits	Horsham Stone Member
underlies	Atherfield Clay Formation
overlies	Tunbridge Wells Sand Formation
thickness	up to 460 m
map	Gallois_Geological_Map_of_Wealden_District_1965.jpg
map_caption	Extent of the Weald Clay within the Weald Basin, shown with horizontal lines

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.

The formation was deposited in lagoonal, lacustrine and alluvial conditions that varied from freshwater to brackish. The climate at the time of deposition is thought to have been semi-arid, and prone to fire. The clay alternates with other subordinate lithologies, notably hard red-weathering beds of ironstone, limestone (Sussex Marble) and sandstones, notably including the calcareous sandstone unit referred to as the Horsham Stone. It has a gradual, conformable contact with the underlying Tunbridge Wells Sand Formation, and has a sharp, unconformable contact with the overlying Atherfield Clay Formation, a shallow marine unit deposited after marine transgression during the Aptian.

Physical properties

The weathered and unweathered forms of the Weald Clay have different physical properties. Blue looks superficially like a soft slate, is quite dry and hard and will support the weight of buildings quite easily. Because it is quite impermeable, and so dry, it does not get broken by tree roots. It is typically found at 750mm down below a layer of yellow clay. Yellow, found on the surface, absorbs water quite readily so becomes very soft in the winter. The two different types make quite different bricks.

Paleofauna

Vertebrates

Vertebrates reported from the Weald Clay	Genus	Species	Location	Stratigraphic position	Material	Notes	Images
		Smokejack Clay Pit	Upper Weald Clay		A spinosaurid
		Rudgwick Brickworks	Upper Weald Clay
Iguanodon	I. bernissartensis	Smokejack Clay Pit	Upper Weald Clay		Iguanodontian, also known from the Wessex Formation.
Mantellisaurus	M. atherfieldensis	Smokejack Clay Pit	Upper Weald Clay		Iguanodontian, also known from the Wessex Formation
		Heathfield	Lower Weald Clay
Leptocleidus	L. superstes			NHM R4828 (holotype)	Pliosauroid
Wyleyia	W. valdensis
Dorsetisaurus	Indeterminate	Keymer Tile Works
Sauropoda	Indeterminate	Smokejacks, Bexhill
Anura	Indeterminate	Keymer Tile Works	Lower	last=Sweetman, S.C; Evans, S. E.	title=English Wealden fossils	date=2011	publisher=Palaeontological Association	isbn=978-1-4443-6711-9	chapter=Lissamphibians (frogs, salamanders and albanerpetontids)	oclc=777385514	chapter-url=https://www.researchgate.net/publication/258090858}}
Urodela	Indeterminate	Keymer Tile Works	Lower	Atlas vertebra	Has been suggested to have a close relationship with Balveherpeton from Germany.

Invertebrates

Numerous insect species are known from several localities in the Weald Clay, including Rudgwick Brickworks, Auclaye Brickworks, Smokejacks and Clockhouse Brickworks

Invertebrates reported from the Weald Clay	Genus	Species	Location	Stratigraphic position	Material	Notes	Images
last1=Jepson	first1=JE	last2=Makarkin	first2=VN	last3=Jarzembowski	first3=E	year=2009	title=New lacewings (Insecta: Neuroptera) from the Lower Cretaceous Wealden supergroup of Southern England	journal=Cretaceous Research	volume=30	issue=5	pages=1325–1338	doi=10.1016/j.cretres.2009.07.012}}	P. rudgwickensis	Rudgwick Brickworks	Upper Weald Clay	Single partial fore-wing	An Ithonidae lacewing, the second in Principiala
Englathauma	E. crabbi	Rudgwick Brickworks	BMB 021962/3 almost complete forewing	A englathaumatid scorpionfly
E. mellishae	Smokejacks	Wing and wing fragments
Cretophasmomima	C. traceyae	Smokejacks	Forewing	A stick insect
Valdicossus	last1=Li	first1=Yuling	last2=Jarzembowski	first2=Edmund	last3=Chen	first3=Jun	last4=Wang	first4=Bo	date=March 2019	title=New Palaeontinidae (Insecta: Hemiptera) from the Lower Cretaceous of southern England	journal=Cretaceous Research	language=en	volume=95	pages=297–301	doi=10.1016/j.cretres.2018.11.019	s2cid=134479224 }}	Smokejacks	Upper	Hindwing	A member of Palaeontinidae
V. chesteri	Cooden Beach	Lower	Hindwing
Ilerdocossus	I. prowsei	Clockhouse Brickworks	Lower		A member of Palaeontinidae
Proraphidia	P. hopkinsi		A member of Mesoraphidiidae
Turanophlebia	T. anglicana		Dragonfly, member of Tarsophlebiidae
Brochocoleus	B. keenani B. tobini	Smokejacks	Upper		Member of Ommatidae
Diluticupes	D. crowsonae
Zygadenia	Z. tuberculata, Z. angliae
Cionocoleus	C. elizabethae, C. watsoni C. minimus
Omma	O. elongatum	Keymer Tile Works	Lower

Flora

Plants reported from the Weald Clay	Genus	Species	Location	Stratigraphic position	Material	Notes	Images
last=Batten	first=David J.	date=June 1998	title=Palaeonenvironmental implications of plant, insect and other organic-walled microfossils in the Weald Clay Formation (Lower Cretaceous) of southeast England	url=https://linkinghub.elsevier.com/retrieve/pii/S0195667198901161	journal=Cretaceous Research	language=en	volume=19	issue=3-4	pages=279–315	doi=10.1006/cres.1998.0116	url-access=subscription }}	W. reticulata	A tree fern
Brachyphyllum					Conifer leaves
Pagiophyllum					Conifer leaves
Pseudofrenelopsis	P. parceramosa				A conifer belonging to the extinct family Cheirolepidiaceae

Footnotes

References

Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. .

References

"Wealden Clay Formation". British Geological Survey.
Radley, Jonathan D. (June 1999). "Weald Clay (Lower Cretaceous) palaeoenvironments in south-east England: molluscan evidence". Cretaceous Research.
Akinlotan, Oladapo O.. (July 2022). "Clay mineral formation and transformation in non-marine environments and implications for Early Cretaceous palaeoclimatic evolution: The Weald Basin, Southeast England". Journal of Palaeogeography.
"Table 4.1," in Weishampel, et al. (2004). Page 72.
"Table 17.1," in Weishampel, et al. (2004). Page 367.
Raven, T. J., P. M. Barrett, S. B. Pond, and S. C. R. Maidment. 2020. Osteology and taxonomy of British Wealden Supergroup (Berriasian–Aptian) ankylosaurs (Ornithischia, Ankylosauria). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2020.1826956
Blows, W.T., 2015, British Polacanthid Dinosaurs – Observations on the History and Palaeontology of the UK Polacanthid Armoured Dinosaurs and their Relatives, Siri Scientific Press, 220 pp.
Galton, P.M., 2009, "Notes on Neocomian (Late Cretaceous) ornithopod dinosaurs from England - ''Hypsilophodon'', ''Valdosaurus'', "Camptosaurus", "Iguanodon" - and referred specimens from Romania and elsewhere", ''Revue de Paléobiologie'' '''28'''(1): 211-273
"Reassessment of the Lower Cretaceous (Barremian) pliosauroid Leptocleidus superstes Andrews, 1922 and other plesiosaur remains from the nonmarine Wealden succession of southern England {{!}} Oxford Academic".
"10.18 West Sussex, England; 1. Hastings Beds" in Weishampel, et al. (2004). Page 559.
Sweetman, S.C; Evans, S. E.. (2011). "English Wealden fossils". Palaeontological Association.
(December 2020). "First salamander from the Lower Cretaceous of Germany". Cretaceous Research.
"Rudgwick Brickworks, Upper Weald Clay (Cretaceous of the United Kingdom)".
"Auclaye Brickworks (BMB collection) (Cretaceous of the United Kingdom)".
"Smokejacks Brickworks (Cretaceous of the United Kingdom)".
"Clockhouse Brickworks (MNEMG collection) (Cretaceous of the United Kingdom)".
"Clockhouse Brickworks (BMNH collection) (Cretaceous of the United Kingdom)".
"Clockhouse Brickworks (BMB collection): Late/Upper Hauterivian, United Kingdom".
(2009). "New lacewings (Insecta: Neuroptera) from the Lower Cretaceous Wealden supergroup of Southern England". Cretaceous Research.
(January 2020). "A new stick insect (Phasmatodea: Susumanioidea) from the Lower Cretaceous Wealden Group of southern England". Cretaceous Research.
(March 2019). "New Palaeontinidae (Insecta: Hemiptera) from the Lower Cretaceous of southern England". Cretaceous Research.
(2008-04-16). "A new genus and species of Palaeontinidae (Insecta: Hemiptera: Cicadomorpha) from the Lower Cretaceous of southern England". Zootaxa.
J. E. Jepson and E. A. Jarzembowski. 2008. [https://www.researchgate.net/publication/242734354_Two_new_species_of_snakefly_Insecta_Raphidioptera_from_the_Lower_Cretaceous_of_England_and_Spain_with_a_review_of_other_fossil_raphidiopterans_from_the_JurassicCretaceous_transition Two new species of snakefly (Insecta: Raphidioptera) from the Lower Cretaceous of England and Spain with a review of other fossil raphidiopterans from the Jurassic/Cretaceous transition]. ''Alavesia'' '''2''':193-201
G. Fleck, G. Bechly, X. Martínez-Delclòs, E. A. Jarzembowski, and A. Nel. 2004. A revision of the Upper Jurassic-Lower Cretaceous dragonfly family Tarsophlebiidae, with a discussion on the phylogenetic positions of the Tarsophlebiidae and Sieblosiidae (Insecta, Odonatoptera, Panodonata. ''Geodiversitas'' '''26(1)''':33-59
(August 2013). "Brochocolein beetles (Insecta: Coleoptera) from the Lower Cretaceous of northeast China and southern England". Cretaceous Research.
(January 2015). "Boring beetles are not necessarily dull: New notocupedins (Insecta: Coleoptera) from the Mesozoic of Eurasia and East Gondwana". Cretaceous Research.
A. G. Ponomarenko. 2006. On the Types of Mesozoic Archostematan Beetles (Insecta, Coleoptera, Archostemata) in the Natural History Museum, London. ''Paleontological Journal'' 40(1):90-9
E. A. Jarzembowski, E. V. Yan, B. Wang and H. Zhang. 2013. Ommatin beetles (Insecta: Coleoptera) from the Lower Cretaceous of northeast China and southern England. ''Terrestrial Arthropod Reviews'' 6:135-161
Batten, David J.. (June 1998). "Palaeonenvironmental implications of plant, insect and other organic-walled microfossils in the Weald Clay Formation (Lower Cretaceous) of southeast England". Cretaceous Research.

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