Strategic Stone Study a Building Stone Atlas of West Sussex (Including Part of the South Downs National Park)
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Strategic Stone Study A Building Stone Atlas of West Sussex (including part of the South Downs National Park) Revised November 2015 Introduction The solid geology of West Sussex comprises gently-dipping West Sussex has a very long history of stone extraction and Cretaceous and younger Cenozoic sedimentary rocks which usage. This began in Neolithic times when flint for making tools form a series of east-west trending ridges and vales across was mined and worked at various sites along the South Downs, much of the southern and central parts of the county. although the earliest flint implements found so far in West Sussex (at Boxgrove), are much older and date from approxi- The oldest rocks are of Early Cretaceous age and crop out in mately 490,000 years ago. Numerous quarries were opened to the north-east of the county in the High Weald area. Here, the provide building stone from Roman times onwards, several of Ashdown and Tunbridge Wells formations (belonging to the which were re-used during the Saxon period (from about 950 ‘Hastings Beds’) have provided a number of sandstones for AD) for the construction of small churches. After the Norman building purposes, including the Ardingly Sandstone. Further Conquest in 1066, large quantities of building stone were west in the county, thin sandstones within the overlying Weald required for the construction of military, civic and religious Clay Formation have been quarried mostly on a minor scale for buildings. New quarries were opened, existing quarries were building stone, with the exception of the Horsham Stone and enlarged and barge access permitted the importation of large Horsham Stone-slate. The latter is the most important indige- amounts of Caen Stone from Normandy and Quarr Stone from nous roofing stone in the county. The Weald Clay Formation is the Isle of Wight. also well known for the occurrence of Sussex Marble, a lime- stone packed with fossil gastropod shells, which polishes well Fewer building stone quarries operated post-C14th and, and has been much-used for internal decorative work. especially after the Dissolution of the Monasteries, it was not until the C18th and C19th that social and industrial changes The oldest east-west trending belt of rocks in the county created a need for more construction stone. The by-product of comprises the Lower Greensand Hythe Formation (one of the chalk extraction for agriculture purposes was flint, which was most important sources of building stone in West Sussex), extensively used for building; large amounts of flint gravel were overlain by the Folkestone and Upper Greensand formations. also removed from beaches along the coast, although even in These provide the sources for two other much-used building the early C19th the removal of stone from offshore reefs was stones: the deeply coloured Carstone (an ironstone) and the recognised as leading to a steady increase in coastal erosion. pale grey Malmstone, respectively. Above these lie the Upper By the mid-C20th, most of the building stone quarries had Cretaceous Chalk Group deposits. Typically these are too soft to closed due to having been worked out or to rising costs and be employed as an external building stone although Lavant stricter environmental regulation making production uneco- Stone (a gritty phosphatic chalk), Chalk Calcrete and Flint are nomic. more resistant and have been used externally, mainly in the southern part of the outcrop. Today, a few quarries extract Hythe Sandstone and Horsham Stone intermittently in West Sussex. The only quarry currently There is a major unconformity between the Cretaceous strata in full-scale production is Philpots Quarry at West Hoathly, and the oldest Tertiary (Palaeogene) sediments. The latter which works Ardingly Sandstone. mainly crop out south of a line extending roughly east-west from near Westbourne via Chichester and Arundel to Worthing. Useful accounts of the geology and use of building stones in These Palaeogene strata consist largely of shallow marine clays West Sussex are provided in the relevant memoirs of the British and sands, but locally they include concretionary layers Geological Survey (BGS) and in the key references listed at the (Bognor Rock and London Clay Cementstone) and calcareous end of this Atlas. The Cretaceous rocks in particular, have a sandstones (Mixon Stone) which have been used locally as complex history of classification and various names have been building stones. assigned to both the strata themselves and to the building stones they have produced. For clarity, the building stone types Above the Tertiary deposits is a further stratigraphic gap above recognised during this study are summarised in Table 1, set which the Quaternary-aged deposits lie. Without doubt the against the modern stratigraphical framework (which is most important of these from a building stone perspective are adhered to throughout). the various, extremely resistant, types of ‘Quaternary flints’ (derived from the older Cretaceous White Chalk Subgroup) such as Downland Field Flint and Beach Pebble Flint. The youngest building stone to have been used in West Sussex is Tufa, although this has a very limited distribution and is employed only on a minor scale. West Sussex Strategic Stone Study 1 PERIOD GROUP FORMATION / MEMBER BUILDING STONES l Tufa l Ferricrete QUATERNARY Various / not defined Various / not defined l Downland Field Flint, Beach Pebble Flint, River Terrace & Fan Gravel Flints Barton Group Barton Clay Formation Selsey Sand Formation l Mixon Stone, Hounds Stone Marsh Farm Formation Bracklesham Group Earnley Sand Formation Wittering Formation TERTIARY (PALAEOGENE) l London Clay Cementstone, London Clay Formation Turritella Bed Concretions Thames Group l Bognor Rock Harwich Formation l ‘Harwich Formation Siltstone’ Reading Formation l ‘Reading Formation Ironstone’ Lambeth Group Upnore Formation l Sarsen Stone Portsdown Chalk Formation l Top Chalk Culver Chalk Formation Newhaven Chalk Formation l Lavant Stone Chalk (incl. Amberley Chalk) Lewes Nodular Chalk Formation and Quarry Flint UPPER Subgroup New Pit Chalk Formation Chalk Group White Chalk CRETACEOUS Holywell Nodular Chalk Formation (Plenus Marls at base) ZigZag Chalk Formation West Melbury Marly Chalk Formation Subgroup (Glauconitic Marl at base) Grey Chalk Grey Chalk Upper Greensand Formation l Malmstone Selborne Group Gault Formation Folkestone Formation l Carstone Marehill Clay Member Pulborough l Pulborough Sandrock Sandrock Member Rogate/Fittleworth Sandgate Lower Greensand Group Formation Members Easebourne Member l Bargate Stone l Hythe Chert Hythe Formation l Hythe Sandstone (Pulborough Stone, Lodsworth Stone, Midhurst Stone, Petworth Stone) LOWER Atherfield Clay Formation CRETACEOUS l Sussex Marble (Paludina Limestones) l Weald Clay Sandstones (Hadfold, Alfold, Weald Clay Formation Oakhurst, Billingshurst, Wisborough and Andrews Hill Sandstones) Horsham Sand Member l Horsham Stone, Horsham Stone-slate Wealden Upper Tunbridge l Forest Sandstone (Shelley Plain, Group Wells Sand Colgate and Roffey Park Sandstones) (‘Wealden Sandstones’) Grinstead Clay Member l Cuckfield Stone, Tilgate Stone Lower Tunbridge Wells Sand & Ardingly l Ardingly Sandstone Tunbridge WellsTunbridge Sand Formation Subgroup Sandstone Member ‘Hastings Beds’ Wadhurst Clay Formation Ashdown Formation l Ashdown Sandstone Table 1. Summary (Interactive) of stratigraphical names applied to Cretaceous and Cenozoic sediments and building stones in West Sussex. West Sussex Strategic Stone Study 2 N West Sussex Bedrock Geology Map N Crawley Horsham Horsted Keynes Billingshurst Midhurst Haywards Heath Singleton South Downs National Park Chichester Worthing Bognor Regis 0 5 10 Km West Sussex Bedrock Geology West Sussex Bedrock Geology BUILDING STONE SOURCES BUILDING STONE SOURCES BRACKLESHAM GROUP AND BARTON GROUP (UNDIFFERENTIATED) - SAND, SILT AND CLAY BRACKLESHAMTHAMES GROUP GROUP AND - CLAY, BARTON SILT, GROUP SAND (UNDIFFERENTIATED) AND GRAVEL - SAND, SILT AND CLAY THAMESLAMBETH GROUP GROUP- CLAY, SILT, - CLAY,SAND AND SILT, GRAVEL SAND AND GRAVEL LAMBETHWHITE GROUP CHALK - CLAY, SUBGROUP SILT, SAND AND GRAVEL CHALK GROUP - CHALK WHITEGREY CHALK CHALK SUBGROUP SUBGROUP } CHALK GROUP - CHALK GREYGAULT CHALK FORMATION SUBGROUP AND UPPER GREENSAND FORMATION (UNDIFFERENTIATED) - MUDSTONE, SANDSTONE AND LIMESTONE GAULT FORMATION AND UPPER GREENSAND FORMATION (UNDIFFERENTIATED) - MUDSTONE, SANDSTONE AND LIMESTONE LOWER GREENSAND GROUP - SANDSTONE AND MUDSTONE LOWER GREENSAND GROUP - SANDSTONE AND MUDSTONE WEALDENWEALDEN GROUP GROUP (principally (principally Weald Clay Weald Formation, Clay but Formation, also includes but stratigraphically also includes lower stratigraphically mudstone-bearing lower units) mudstone-bearing - MUDSTONE, units) SILTSTONE- MUDSTONE, AND SANDSTONE SILTSTONE AND SANDSTONE WEALDEN GROUP (principally Tunbridge Wells Sand Formation, but also includes coarser grained lithologies of stratigraphically higher mudstone-dominatedWEALDEN GROUP units) (principally - SANDSTONE Tunbridge AND SILTSTONE, Wells INTERBEDDED Sand Formation, but also includes coarser grained lithologies of stratigraphically higher mudstone-dominated units) - SANDSTONE AND SILTSTONE, INTERBEDDED Derived from BGS digital geological mapping at 1:625,000 scale, British Geological Survey © NERC. All rights reserved West Sussex Strategic Stone Study 3 and comprises yellowish-brown to pale grey, fine-grained Lower Cretaceous sandstones with a thin, pebble-bed base. Sandstone varieties Wealden Group occur in each