Weald Clay or the Weald Clay Formation is a
Lower Cretaceous sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
unit underlying areas of South East
England
England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
, between the
North
North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography.
Etymology
T ...
and
South Downs, in an area called the
Weald Basin. It is the uppermost unit of the
Wealden Group
The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group (stratigraphy), group (a sequence of rock strata) in the lithostratigraphy of southern England. The Wealden group consists of wiktionary:paralic, paralic to c ...
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
The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
on the
Isle of Wight
The Isle of Wight (Help:IPA/English, /waɪt/ Help:Pronunciation respelling key, ''WYTE'') is an island off the south coast of England which, together with its surrounding uninhabited islets and Skerry, skerries, is also a ceremonial county. T ...
. 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
brick
A brick is a type of construction material used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a unit primarily composed of clay. But is now also used informally to denote building un ...
making.
The formation was deposited in
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...
al,
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
The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
.
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
Invertebrates
Numerous insect species are known from several localities in the Weald Clay, including Rudgwick Brickworks,
Auclaye Brickworks,
Smokejacks and
Clockhouse Brickworks
Flora
See also
*
Wealden District
Wealden is a local government district in East Sussex, England. Its council is based in Hailsham, the district's second largest town. The district also includes the towns of Crowborough, Polegate and Uckfield, along with numerous villages an ...
*
London Clay
The London Clay Formation is a Sediment#Shores and shallow seas, marine formation (geology), geological formation of Ypresian (early Eocene Epoch, c. 54-50 million years ago) age which outcrop, crops out in the southeast of England. The London C ...
*
Oxford Clay
*
List of dinosaur-bearing rock formations
Footnotes
References
* Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. {{ISBN, 0-520-24209-2.
Geology of England
Geologic formations of the United Kingdom
Claystone formations
Lower Cretaceous Series of Europe
Hauterivian Stage
Barremian Stage
Shale formations
Siltstone formations
Sandstone formations
Limestone formations of the United Kingdom