Difference between revisions of "Geology of the Andover area: Applied geology - Bulk minerals"
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Revision as of 11:43, 28 August 2013
|This page is part of a category of pages providing a summary of the geology of the Andover district (British Geological Survey Sheet 283), which extends over approximately 600 km2 of north-west Hampshire and a small part of eastern Wiltshire. Links to other pages in this category can be found at the foot of the page.
Authors: J Thompson, K A Lee, P M Hopson, A R Farrant, A J Newell, R J Marks, L B Bateson, M A Woods, I P Wilkinson and N J Smith.
Bulk mineral use is confined to three deposits in this district: sand and gravel, brick clay and chalk have been extracted in the past but there are no large-scale operations remaining in the district. Resources are won only a local basis and at need from older extraction sites. Further information can be obtained from the BGS BRITPITS database (http://www.bgs.ac.uk/products/minerals/BRITPITS.html)
Sand and gravel
There is no large-scale extraction of aggregate from any of the deposits in the district. Resources exist within the Upper Greensand (sand) and within the various Quaternary deposits (sand and gravel), but they are either not exploited or only worked on a local scale to support farms. Their grade and potential as a source of aggregate has not been tested.
The Lambeth Group, London Clay Formation and various Quaternary deposits were used for brickmaking in the past but there is no large-scale commercial manufacture in the district.
Chalk has been extracted in the past for cement manufacture but this industry has ceased locally as production has switched to mega-site localities elsewhere in southern England. Some chalk is still won for agricultural liming, generally on a within-farm at-need basis but even this has declined in preference to commercial supply. This liming use has given rise to a large number of small, and now generally overgrown, quarries on the margins of the Upper Greensand and the clay-with-flints that were traditionally the deposits that required regular dressing to maintain productivity.
Extensive use is made of the flints from the Chalk for building, particularly in churches and the larger houses and farms. The flint is used both as knapped squared blocks and as single-faced trimmed nodules. Flint shards derived from the knapping of dressed flint are often seen pressed into the wet mortar for decoration, a process known a ‘galletting’. Flint, as a waste product of chalk extraction and from 'field picking', has also been used to maintain farm tracks.
The harder chalks from the Melbourn Rock Member and the Lewes Nodular Chalk Formation are incorporated into buildings to a small extent in this area. Their source is unknown, but both dressed blocks (suggesting some form of quarrying) and ‘field-picked’ clasts are seen in older buildings.
A number of large houses in the district were built, rebuilt or remodelled using imported stone due to the lack of suitable building stone locally; for example, Highclere Castle, which was remodelled from a brick-built Elizabethan residence by a dressing of Bath Stone (see Plate 5) and has recently been used as a location for the filming of Gosford Park.
|Plate 5 Highclere Castle [SU 4457 5880]. A Bath Stone edifice built in 1839-42 by Sir Charles Barry (who also built the Houses of Parliament) in the Jacobethan style (a Victorian revival of the architecture of the late 16th and early 17th century). The completely remodelled castle, replacing a square classic-style mansion and an earlier Elizabethan brick and freestone house. The site was formerly occupied by a medieval palace for the Bishops of Winchester. Photo P J Witney. P775267.|
There are records of extraction of the Upper Greensand Formation near Burghclere and Highclere in the 13th century for building stone. Both the common colloidal cherts and the indurated ‘malmstone’ facies are present in buildings locally.
Geology of the Andover area - contents
- Bulk minerals