«Mineral Resource Information in Support of National, Regional and Local Planning Oxfordshire Commissioned Report CR/04/062N BRITISH GEOLOGICAL SURVEY ...»
Mineral Resource Information in
Support of National, Regional
and Local Planning
Commissioned Report CR/04/062N
BRITISH GEOLOGICAL SURVEY
COMMISSIONED REPORT CR/04/062N
Mineral Resource Information in
Support of National, Regional and
G E Norton, D G Cameron, A J Bloodworth,
D J Evans, G K Lott, K A Arbon, N A Spencer and
D E Highley
Mineral resources, mineral planning, Oxfordshire.
Front cover Excavator working bed of sand from the Highworth Grit (Kingston Formation, Corallian Group) at Shellingford Quarry near Faringdon.
Bibliographical reference G E NORTON, D G CAMERON, A J BLOODWORTH, D J EVANS, G K LOTT, K A ARBON, N A SPENCER, and D E HIGHLEY. 2004. Mineral Resource Information in Support of National, Regional and Local Planning - Oxfordshire. British Geological Survey Commissioned Report, CR/04/062N. 12pp.
Keyworth, Nottingham British Geological Survey 2004
BRITISH GEOLOGICAL SURVEYThe full range of Survey publications is available from the BGS British Geological Survey offices Sales Desks at Nottingham, Edinburgh and London; see contact details below or shop online at www.geologyshop.com Keyworth, Nottingham NG12 5GG 0115B936 3100
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1.1 Resources and reserves
1.2 Environmental designations
2 Sand and gravel
2.1 River terrace deposits
2.2 Glaciofluvial Deposits
2.3 Bedrock deposits
3 Crushed rock aggregate
5 Building stone
7.1 Conventional oil and gas
7.2 Coal bed methane (CBM) potential
8 Brick clay
9 Fuller’s earth
10 Aims and limitations
11 Planning permissions for the extraction of minerals
FIGURES Figure 1. Production of sand and gravel in Oxfordshire, 1979-2002 (Source Annual Mineral Raised Inquiry, Office for National Statistics)
Figure 2. Marlstone Rock Formation ironstone being worked for crushed rock aggregate at Wroxton Fields Quarry near Banbury, Peter Bennie Ltd.
Figure 3. Surface planning permissions and landscape and nature conservation designations in Oxfordshire
i ii 1 Introduction This report is one of a series prepared by the British Geological Survey for various administrative areas in England for the Office of the Deputy Prime Minister’s research project Mineral Resource Information in Support of National, Regional and Local Planning.
The accompanying map relates to the county of Oxfordshire and delineates the mineral resources of current, or potential, economic interest in the area and the sites where minerals are or have been worked. It also relates these to national planning designations, which may represent constraints on the extraction of minerals.
Three major elements of information are presented:
• the geological distribution and importance of mineral resources;
• the extent of mineral planning permissions and the location of current mineral workings;
• the extent of selected, nationally-designated planning constraints.
This wide range of information, much of which is scattered and not always available in a consistent and convenient form, is presented on a digitally-generated summary map on the scale of 1:100 000. This scale is convenient for the overall display of the data and allows for a legible topographic base on which to depict the information. However, all the data are held digitally at larger scales using a Geographical Information System (GIS), which allows easy revision, updating and customisation of the information together with its possible integration with other datasets. The information will be incorporated into a regional GIS which will provide a Summary of the Mineral Resources of the South East Region.
The purpose of the work is to assist all interested parties involved in the preparation and review of development plans, both in relation to the extraction of minerals and the protection of mineral resources from sterilisation. It provides a knowledge base, in a consistent format, on the nature and extent of mineral resources and the environmental constraints which may affect their extraction. An important objective is to provide baseline data for the long term. The results may also provide a starting point for discussion on specific planning proposals for minerals extraction or on proposals, which may sterilise resources.
It is anticipated that the map and report will also provide valuable background data for a much wider audience, including the different sectors of the minerals industry, other agencies and authorities (e.g. The Planning Inspectorate Agency, the Environment Agency, The Countryside Agency and English Nature), environmental interests and the general public.
Basic mineral resource information is essential to support mineral exploration and development activities, for resource management and land-use planning, and to establish baseline data for environmental impact studies and environmental guidelines. It also enables a more sustainable pattern and standard of development to be achieved by valuing mineral resources as national assets.
The mineral resources covered are sand and gravel, crushed rock aggregate, chalk, fuller’s earth, brick clay, building stones, coal and hydrocarbons.
1.1 RESOURCES AND RESERVES Mineral resources are natural concentrations of minerals or bodies of rock (or fluids such as oil and gas) that are, or may become, of potential interest as a basis for the economic extraction of a mineral product. They exhibit physical and/or chemical properties that make them suitable for specific uses and are present in sufficient quantity to be of intrinsic economic interest. Areas that are of potential economic interest as sources of minerals change with time as markets decline or expand, product specifications change, recovery technology is improved or more competitive sources become available.
That part of a mineral resource, which has been fully evaluated and is commercially viable to work is called a mineral reserve. In the context of land-use planning, the term mineral reserve should strictly be further limited to those minerals for which a valid planning permission for extraction exists (i.e. permitted reserves). Without a valid planning consent no mineral working can take place and consequently the inherent economic value of the mineral resource cannot be released and resulting wealth created. The ultimate fate of mineral reserves is to be either physically worked out or to be made non-viable by changing economic circumstances.
Mineral resources defined on the map delineate areas within which potentially workable mineral may occur. These areas are not of uniform potential and also take no account of planning constraints that may limit their working. The economic potential of individual sites can only be proved by a detailed evaluation programme. Such an investigation is also an essential precursor to submitting a planning application for mineral working. Extensive areas are shown as having no mineral resource potential, but some isolated mineral workings may occur in these areas. The presence of these operations generally reflects local or specific situations.
1.2 ENVIRONMENTAL DESIGNATIONS The map shows the extent of selected, nationally-designated planning constraints as defined for the purposes of this study. These are defined on a common national basis and therefore represent a consistent degree of constraint across the country. No interpretation should be made from the map with regard to the relative importance of the constraints, either in relation to mineral development proposals or in relation to each other. Users should consult policy guidelines issued by the relevant Government department, statutory agency or local authority.
The constraints shown on the map are:
• Area of Outstanding Natural Beauty – Chilterns (part)
• National nature conservation designations – National Nature Reserves (NNR) and Sites of Special Scientific Interest (SSSI)
• International nature designations – Special Areas of Conservation (SAC), Special Protection Areas (SPA) and Ramsar sites
• Scheduled Monuments Mineral development may also be constrained by many other factors not shown on the map, including local landscape designations, considerations relating to the protection of other resources, such as groundwater, and local amenity or environmental concerns, such as noise, traffic and visual impact. These have been excluded because the constraint is not defined on a national basis or the information is not generally available. The extent or degree of relevance of such constraints can be ascertained from the relevant statutory agency or the appropriate Mineral Planning Authority.
2 Sand and gravel Sand and gravel are defined on the basis of particle size rather than composition. In current commercial practice, following the introduction of new European standards from 1st January 2004, the term ‘gravel’ (or more correctly coarse aggregate) is used for general and concrete applications to define particles between 4 and 80 mm, and the term ‘sand’ for material that is finer than 4 mm, but coarser than 0.063 mm. For use in asphalt 2 mm is now the break point between coarse and fine aggregate. Most sand and gravel is composed of particles that are rich in silica (quartz, quartzite and flint), but other rock types may occur locally.
The principal uses of sand are as fine aggregate in concrete, mortar and asphalt. The main use of gravel is as coarse aggregate in concrete. Substantial quantities of sand and gravel may also be used for construction fill.
Oxfordshire produced 1.5 million tonnes of sand and gravel in 2002, and has estimated permitted reserves of 12 million tones. Recent production figures are shown in Figure 1.
Sand and gravel resources occur in a variety of geological environments. In Oxfordshire, these resources fall into three categories: river terrace deposits; glaciofluvial deposits; and bedrock sand and gravel. The first two categories are considered as superficial deposits and were assessed in parts of Oxfordshire by BGS in the 1970s and 1980s. Resources identified in these areas are identified separately on the map, and the possible extent of sand and gravel concealed beneath overburden is shown. These concealed resources were defined by overburden to mineral ratios (overburden to mineral less than 3:1). Outside these areas, available data are more limited.
Generally, only exposed sand and gravel are defined, although sub-alluvial resources of sand and gravel occurring beneath modern river floodplains may be extensive in some areas, and are marked on the map. However, narrow ( 200 m width) spreads of sub-alluvial deposits are mainly excluded from the map. Their limited width is likely to preclude economic working of any sand and gravel present.
The river terrace deposits and the glaciofluvial deposits were probably formed by a similar mechanism, i.e., deposited mostly from meltwater during glacial episodes. However, the superficial deposits are split into these two different categories on this map for the following reasons. The glaciofluvial deposits are older (Anglian and pre-Anglian age) and are generally less continuous than river terrace deposits, and smaller in extent. Glaciofluvial deposits are thought to be derived partly from lithologies in the Midlands and thus have a higher proportion of quartz-rich clasts. Most current sand and gravel workings are in river terrace deposits.
Thousand tonnes Figure 1. Production of sand and gravel in Oxfordshire, 1979-2002 (Source: Annual Minerals Raised Inquiry, Office for National Statistics)
2.1 RIVER TERRACE DEPOSITS These deposits occur in both raised river terrace sequences and as flood plain terraces associated with and underlying present day alluvium. They are of late Anglian to Devensian age. River terraces occur at several levels in most of the major valleys in the county flanking the present floodplain, particularly associated with the River Thames and the major tributaries thereof. The older terraces are higher above the present course of the river and are generally dry in their upper parts. Younger terraces can be saturated at their bases. The deposits comprise sequences of sands and gravels with sheet-like morphology, sub-horizontal upper surfaces, and thicknesses of up to a few metres. The younger deposits are more laterally continuous since they have been cut down less by subsequent river erosion.
River terrace deposits represent an important resource in the county since they are generally clay-poor. They are being worked extensively throughout the Thames Valley and its tributaries.
These deposits, particularly above Oxford, are largely derived from the Jurassic limestones of the Cotswolds.
2.2 GLACIOFLUVIAL DEPOSITS In Oxfordshire there are several areas where fast-moving, high-volume rivers derived from glacial meltwater laid down gravelly deposits in pre-Anglian to Anglian times. These earlier deposits are here named ‘glaciofluvial’ deposits, and are described below. Previously some of these deposits have been mapped as glacial deposits or head gravel.