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) Published June 2015 Derived from BGS digital geological mapping Introduction at 1:625,000 scale, British Geological Survey © West Sussex Bedrock Geology NERC. All rights reserved There is a major unconformity between the The solid geology of West Sussex comprises Cretaceous strata and the oldest Tertiary gently-dipping Cretaceous and younger (Palaeogene) sediments. The latter mainly crop Cenozoic sedimentary rocks which form a out south of a line extending roughly east-west series of east-west trending ridges and vales from near Westbourne via Chichester and across much of the southern and central parts Arundel to Worthing. These Palaeogene strata of the county. consist largely of shallow marine clays and The oldest rocks are of Early Cretaceous age sands, but they do include concretionary layers and crop out in the north-east of the county in (Bognor Rock and London Clay Cementstone) the High Weald area. Here, the Ashdown and and calcareous sandstones (Mixon Stone) Tunbridge Wells formations (belonging to the which have been used locally as building ‘Hastings Beds’) have provided a number of stones. sandstones for building purposes, including Above the Tertiary deposits is a further the Ardingly Sandstone. Further west in the stratigraphic gap, over which the Quaternary- county, thin sandstones within the overlying aged deposits lie. Without doubt, the most Weald Clay Formation have been quarried important of these from a building stone mostly on a minor scale for building stone, perspective are the various, extremely resistant, with the exception of the Horsham Stone and types of ‘Quaternary flints’ (derived from the Horsham Stone-slate. The latter is the most older Cretaceous White Chalk Subgroup) such important indigenous roofing stone in the as Downland Field Flint and Beach Pebble Flint. county. The Weald Clay Formation is also well The youngest building stone to have been used known for the occurrence of Sussex Marble, a in West Sussex is Tufa, although this has a very limestone packed with fossil gastropod shells, limited distribution and is employed only on a which polishes well and has been much-used minor scale. for internal decorative work. West Sussex has a very long history of stone The oldest east-west trending belt of rocks in extraction and usage. This began in Neolithic the county comprises the Lower Greensand times when flint for making tools was mined Hythe Formation (one of the most important and worked at various sites along the South sources of building stone in West Sussex), Downs, although the earliest flint implements overlain by the Folkestone and Upper found so far in West Sussex (at Boxgrove), Greensand formations. These provide the are much older and date from approximately sources for two other much-used building 490,000 years ago. Numerous quarries were stones: the deeply coloured Carstone (an opened to provide building stone from Roman ironstone) and the pale grey Malmstone, times onwards, several of which were re-used respectively. Above these lie the Upper during the Saxon period (from about 950 Cretaceous Chalk Group deposits. Typically, AD) for the construction of small churches. these are too soft to be employed as an After the Norman Conquest in 1066, large external building stone, although Lavant Stone quantities of building stone were required for (a gritty phosphatic chalk), Chalk Calcrete and the construction of military, civic and religious Flint are more resistant and have been used buildings. New quarries were opened, existing externally, mainly in the southern part of the quarries were enlarged and barge access outcrop. permitted the importation of large amounts of Caen Stone from Normandy and Quarr Stone from the Isle of Wight. West Sussex Strategic Stone Study 1 West Sussex Strategic Stone Study 2 PERIOD GROUP FORMATION/MEMBER BUILDING STONES • Tufa • Ferricrete Various/not defined Various/not defined QUATERNARY • Downland Field Flint, Beach Pebble Flint, River Terrace & Fan Gravel Flints Barton Group Barton Clay Formation Selsey Sand Formation • Mixon Stone, Hounds Stone Marsh Farm Formation Bracklesham Group TERTIARY Earnley Sand Formation (PALAEOGENE) Wittering Formation • London Clay Cementstone, Turritella Bed London Clay Concretions Thames Group Formation • Bognor Rock • ‘Harwich Formation Siltstone’ Harwich Formation Reading Formation • ‘Reading Formation Ironstone’ Lambeth Group Fewer building stone quarries operated post- Useful accounts of the geology and use of Upnore Formation • Sarsen Stone C14th and especially after the Dissolution of the building stones in West Sussex are provided in Portsdown Chalk Formation • Top Chalk Monasteries and it was not until the C18th and the relevant memoirs of the British Geological Culver Chalk Formation Newhaven Chalk Formation C19th that social and industrial changes created Survey (BGS) and in the key references listed • Lavant Stone Lewes Nodular Chalk Formation a need for more construction stone. The at the end of this Atlas. The Cretaceous New Pit Chalk Formation Chalk Group by-product of chalk extraction for agriculture rocks, in particular, have a complex history of Holywell Nodular Chalk Formation Chalk (incl. Amberley Chalk) and Quarry Flint White Chalk Subgroup White purposes was flint, which was extensively used classification and various names have been (Plenus Marls at base) ZigZag Chalk Formation for building; large amounts of flint gravel were assigned to both the strata themselves and West Melbury Marly Chalk Formation (Glauconitic also removed from beaches along the coast, to the building stones they have yielded. For Marl at base) although even in the early C19th the removal clarity, the building stone types recognised Grey Chalk Subgroup Upper Greensand Formation • Malmstone of stone from offshore reefs was recognised during this study are summarised in Table 1 Selborne Group Gault Formation as leading to a steady increase in coastal on page 4 opposite, set against the modern Folkestone Formation • Carstone th erosion. By the mid-C20 , most of the building stratigraphical framework (which is adhered to Marehill Clay Member stone quarries had closed either due to having throughout). Pulborough been worked out or to rising costs and stricter • Pulborough Sandrock Sandgate Formation Sandrock Member environmental regulation making production Rogate/Fittleworth uneconomic. CRETACEOUS Lower Greensand Group Members Easebourne Member • Bargate Stone Today, a few quarries extract Hythe Sandstone and Horsham Stone intermittently in West • Hythe Chert Hythe Formation • Hythe Sandstone (Pulborough Stone, Sussex. The only quarry currently in full-scale Lodsworth Stone, Midhurst Stone, Petworth Stone) production is Philpots Quarry at West Hoathly, Atherfield Clay Formation which works Ardingly Sandstone. • Sussex Marble (‘Paludina Limestones’) • Weald Clay Sandstones (Hadfold, Alfold, Weald Clay Formation Oakhurst, Billingshurst, Wisborough and Andrews Hill Sandstones) Wealden Group (‘Wealden Horsham Sand • Horsham Stone, Horsham Stone-Slate Sandstones’) Member Upper Tunbridge • Forest Sandstone (Shelley Plain, Colgate Wells Sand and Roffey Park Sandstones) Grinstead Clay • Cuckfield Stone, Tilgate Stone Tunbridge Wells Member Sand Formation Lower Tunbridge • Ardingly Sandstone Wells Sand & Ardingly Member (Subgroup)’ ‘Hastings Beds Wadhurst Clay Formation • Ashdown Sandstone Ashdown Formation Table 1. Summary of stratigraphical names applied to Cretaceous and Cenozoic sediments in West Sussex (the main sources of building stones are highlighted in blue). West Sussex Strategic Stone Study 3 West Sussex Strategic Stone Study 4 Jacobean Almshouses at Sackville College, built 1609-19. Distinguishing between individual sandstones is usually These are built mainly of rough, squared blocks of ochreous Lower Tunbridge Wells Sandstone alternating with silvery-grey Lower Cretaceous not possible unless their exact provenance is known from Ardingly Sandstone; the roof is of Horsham Stone-slate. Wealden Group documentary evidence. Each sandstone unit is up to 6m thick and comprises yellowish-brown to pale grey, fine- Wealden Sandstones and Sussex Sandstones grained sandstones with a thin, pebbly base. Sandstone varieties occur in each unit and range from massive to flaggy The Wealden Group, in South-East England, comprises lithologies, sometimes with ripple-marks on the uppermost a thick sequence of Early Cretaceous sediments. The surface, and they are often cemented with calcite and iron history of the Wealden Group stratigraphy is long and oxides. The latter varieties are more resistant to weathering. complex, and various names have been applied to Throughout the sandstone units, fossils are generally sparse different parts of the succession at various times. This and poorly preserved, but locally they may be abundant and is partly the result of the lateral facies variations shown include freshwater bivalves, gastropods and plants, with by these sediments across their outcrop area, which is occasional rolled dinosaur bones occurring in the thin basal an issue that has particular relevance to the numerous pebble-bearing beds. sandstones that occur within the Wealden Group and have been employed for building purposes. All four Ashdown Sandstone units have been used historically as a source of local building stone and The situation is further complicated by the recognition were formerly quarried around Horsted Keynes and that