Difference between revisions of "Geology of the Andover area: Exposed strata - Artificial ground"

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Revision as of 11:31, 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.

ARTIFICIAL GROUND

The major occurrences of made, worked, infilled and landscaped ground are noted on the 1:10 000 scale maps within the district. Only the larger areas are transferred onto the published 1:50 000 scale Andover Sheet 283. In urban areas the amount of artificial ground is often difficult to determine, and its limits often masked by the built environment. Whilst most of the villages are on natural ground, the larger urban areas (particularly within industrial estates, development parks and post-war housing estates) have suffered a large amount of landscaping and the degree of ‘cut and fill’ is often impossible to determine. The artificial ground shown on the maps in those areas is probably an underestimate.

Most of the major road (and rail) routeways have a network of worked (cuttings), made (embankments) and infilled ground that is too complex to show at 1:50 000 scale and even in some cases on the 1:10 000 scale maps. Where previously created artificial ground has been further disturbed, the relationship can be even more complex. A good example of this is in the use of the old Newbury to Winchester railway line as the routeway for part of the A34 dual carriageway that crosses the district from Burghclere to Whitchurch.

Made ground

Made ground is a term used to denote areas where additional material, foreign to the site, has been deposited above the natural ground surface. Occurrences are mainly related to road and rail embankments and archaeological sites (commonly identified by a symbol on the base maps). Modern road and rail developments are generally made up of ‘engineered fill’ designed to carry the loads expected, and therefore considered to be more stable than that created by the excavations for archaeological earthworks and other features.

The two main categories of made ground are waste in landfill sites and natural materials produced either as spoil from mineral extraction, or dug for the construction of various embankments and raised areas, including bunds for flood defence. Recycling of waste construction materials is leading to their increased usage in urban and industrial landscaping.

Worked ground

Worked ground is shown where natural materials are known to have been removed, for example in quarries and pits, road and rail cuttings and general landscaping.

In the Andover district, chalk is the most commonly extracted material, principally for use as an agricultural lime but also, in the past, for the manufacture of cement, as a filler and as a whitening agent.

There are records of extraction of the Upper Greensand Formation near Burghclere and Highclere in the 13th century for building stone.

There are some old sand and gravel workings, mostly associated with alluvial gravels and river terrace deposits. In the past most villages had a small brick and tile quarry to supply local needs. In the Andover district, the Lambeth Group, Thames Group and a number of the Quaternary deposits have been used in the past for such material.

Infilled ground

Infilled ground comprises areas where the natural ground has been removed and the void, wholly or partly backfilled with man-made deposits, which may be either natural or waste material, or a combination of both. Where quarries and pits have been filled, the ground restored and landscaped, built on or returned to agricultural use, there may be no surface indication of the extent of the backfilled area. In such cases, the boundaries of these sites are taken from archival sources such as earlier aerial photographs, local authority records and old topographical and geological maps.

Landscaped ground

This consists of areas that have been extensively remodelled or landscaped, with complex patterns of cut and fill, too small to be identified separately. Such areas commonly include parkland, golf courses and major construction sites.

Geology of the Andover area - contents

Introduction

Geological setting

Geological description

Concealed strata
Ordovician to Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Exposed Strata
Upper Greensand Formation (UGS)
Chalk Group
Palaeogene
Quaternary
Artificial ground

Applied geology

Hydrogeology
Bulk minerals
Geotechnical considerations and hazards

Information resources

References

Geological map