G.K. Lott

Sourcing stone for the conservation and repair of historical buildings in Britain

Stone for the construction of buildings and monuments has been locally quarried from most parts of Britain’s lithologically diverse geological succession starting about 3500 years ago. Each part of the geological column, from the Precambrian to Quaternary, has yielded stone for building, providing a colourful palette for Britain’s stone architecture and monuments. For those involved in conserving these structures this diversity of stone types has become an increasing problem as many of the original quarries have long since stopped working and the stones have disappeared from the marketplace. This lack of an adequate range of indigenous stones suitable for conservation repair and for sympathetic new-build projects is a continuing concern for heritage organizations, property owners and developers in Britain. There are a number of ways in which this problem is being addressed. It is clearly important to demonstrate the scale of the problem by collating sufficient information to identify those stones (and, therefore, those stone structures) most under threat. Although some vernacular stones were often used widely others appear in only a small number of buildings. A national database of all indigenous stone sources and an assessment of their extent of use is, therefore, essential. Subsequent analysis of the data gathered will then allow those stones that are of critical concern to be identified, which might generate sufficient interest and economic potential for quarry operators to consider reopening sites for new stone production. This contribution is an attempt to give an overview of the former extent of the building stone resources of Britain to illustrate the magnitude of the current problems of stone supply.

A reappraisal of the stratigraphy and depositional development of the Upper Greensand (Late Albian) of the Devizes district, southern England

Three members are recognized within the Upper Greensand Formation of the Devizes district on the basis of outcrop, newly acquired cored borehole and petrographical data. These are, in ascending stratigraphical order, Cann Sand Member, Potterne Sandstone Member and Easterton Sandstone Member. Compared to the imprecise historical subdivisions, the members provide a much clearer indication of lithological variation through the Upper Greensand and this, in turn, provides clues to its depositional development. The biostratigraphy of each member was determined using macrofossils and microfossils. The new biostratigraphical data clarify the relationship of the Potterne Rock to the traditionally named ‘Ragstone’, which caps the Shaftesbury Sandstone in the Shaftesbury district, and suggest that the correlation of the Potterne Rock and ‘Ragstone’ is less straightforward than suggested previously. There are some distinct contrasts with the stratigraphy of the Upper Greensand southwest of Devizes (Shaftesbury and Wincanton districts). Whilst tectonic influences have been demonstrated to affect coeval strata in parts of the eastern Weald, these may not be the dominant control on the Devizes succession, which seems to be influenced more strongly by its palaeogeographical setting with respect to sediment source areas, and the effect this had on the volume and timing of sediment infill. Palaeogeography may also be indirectly responsible for the absence of cherts in the Upper Greensand of the Devizes area, in contrast to their conspicuous development in the Upper Greensand of southwest England and the Weald.