Lower Dicker is a 0.12 hectare (0.23 acre) geological Site of Special Scientific Interest

Site of Special Scientific Interest

A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...

 in East Sussex

East Sussex

East Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the south by the English Channel.-History:...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. The site was notified in 1998 under the Wildlife and Countryside Act 1981

Wildlife and Countryside Act 1981

The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom and was implemented to comply with the Directive 2009/147/EC on the conservation of wild birds...

. The site is a small, over-grown quarry approximately four kilometres north-west of Hailsham

Hailsham

Hailsham is a civil parish and the largest of the five main towns in the Wealden district of East Sussex, England. Mentioned in the Domesday Book, the town of Hailsham has had a long history of industry and agriculture...

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Geology

Exposures of a sand member are present in the quarry. The sand is of the lower division of the Weald Clay

Weald Clay

Weald Clay is a Lower Cretaceous sedimentary rock underlying areas of South East England. It is part of the Wealden Group of rocks. The clay is named after the Weald, an area of Sussex. It varies from orange and grey in colour and is used in brickmaking....

. The sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 units of the Weald Clay Group represent river deposits which periodically extended into the Wealden lake or lagoon

Lagoon

A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

. The sandstones are important as lithostratigraphical markers (units of rock with the same affinity) and are considered to reflect the effects of tectonic uplift

Tectonic uplift

Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...

 in nearby areas feeding sediment into the area. The mineralogy

Mineralogy

Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...

 of these sandstones reflects their provenance and they are therefore of great importance for understanding the changes which took place in the palaeogeography

Palaeogeography

Palaeogeography is the study of what the geography was in times past. It is most often used about the physical landscape, although nothing excludes its use in reference to the human or cultural environment...

 of the Weald

Weald

The Weald is the name given to an area in South East England situated between the parallel chalk escarpments of the North and the South Downs. It should be regarded as three separate parts: the sandstone "High Weald" in the centre; the clay "Low Weald" periphery; and the Greensand Ridge which...

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Upper Dicker provides the most southerly exposure of any of the Weald Clay sand members in Britain. It is also important for marking the furthest known extension eastwards of Cornubian (what is today Devon and Cornwall) debris (pieces of rock incorporated into the sandstones and clays), indicating the presence of a river system extending out of south-west England at this time.