Lower Dicker is a geological

Site of Special Scientific Interest A Site of Special Scientific Interest (SSSI) in Great Britain or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland is a conservation designation denoting a protected area in the United Kingdom and Isle of ...

west of

Hailsham Hailsham is a town, a civil parish and the administrative centre of the Wealden district of East Sussex, England.OS Explorer map Eastbourne and Beachy Head Scale: 1:25 000. Publisher:Ordnance Survey – Southampton B2 edition. Publishing Dat ...

East Sussex East Sussex is a ceremonial and non-metropolitan county in South East England on the English Channel coast. It is bordered by Kent to the north and east, West Sussex to the west, and Surrey to the north-west. The largest settlement in East Su ...

. It is a

Geological Conservation Review The Geological Conservation Review (GCR) is produced by the UK's Joint Nature Conservation Committee and is designed to identify those sites of national and international importance needed to show all the key scientific elements of the geological a ...

site.

Geology

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

Weald Clay 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 ro ...

. The

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

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

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'') a ...

. 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 is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thick ...

in nearby areas feeding sediment into the area. The

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...

of these sandstones reflects their

provenance Provenance (from the French ''provenir'', 'to come from/forth') is the chronology of the ownership, custody or location of a historical object. The term was originally mostly used in relation to works of art but is now used in similar senses i ...

and they are therefore of great importance for understanding the changes which took place in the

palaeogeography Palaeogeography (or paleogeography) is the study of historical geography, generally physical landscapes. Palaeogeography can also include the study of human or cultural environments. When the focus is specifically on landforms, the term pale ...

of the

Weald The Weald () is an area of South East England between the parallel chalk escarpments of the North and the South Downs. It crosses the counties of Hampshire, Surrey, Sussex and Kent. It has three separate parts: the sandstone "High Weald" in the ...

. 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.

References

{{SSSIs East Sussex Sites of Special Scientific Interest in East Sussex Geological Conservation Review sites