Jis A 5354 1993 Concrete Sheet P
Christel Malden
Contact the BGS Intellectual Property Rights Manager, Keyworth, Nottingham. You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract.
Numerous organisations and individuals supplied information during the resurvey of the Sheet 126 Nottingham, including British Gypsum, Blue Circle, Tarmac Brick and Hoveringham Gravels. In particular we wish to thank the Coal Authority, RJB, British Petroleum, the Environment Agency and Nottinghamshire County Council for supplying and granting permission to publish borehole and seismic data. Burrow Croker, and G Maunsell and partners also supplied borehole core material. We are most grateful to local landowners, especially the farmers and quarry owners, for their co-operation in providing access for the surveyors.
The task of compiling the memoir was started by A S Howard and taken to completion by J N Carney. The memoir was edited by R D Lake, S G Molyneux and A A Jackson; figure production was by R J Demaine and P Lappage; pagesetting by A Hill.
In 1990, the British Geological Survey embarked upon a major programme of geological survey (or resurvey) in Britain, in order to bring standards of mapping and of multidisciplinary geological science up to the level of detail and precision that will be required for the foreseeable future. The rationale and objectives of this programme have since been revised, as reviewed by Walton and Lee (2001). The programme is driven by an assessment of end-user requirements for geoscience information, and is carried out within the framework of what is realistically achievable given the ever-changing levels of financial and staffing resources available to the survey. This memoir and the accompanying map provide a full evaluation of the detailed stratigraphy of the Nottingham district, its mineral, hydrocarbon and water resources, and the constraints that the surface and subsurface geo-environments place on urban and rural development.
The geology of the Nottingham district has exerted an important control over its industrial development and rural land use. The form of the landscape is controlled by the nature of the underlying rocks, and the location of resources such as minerals, water, fertile soils and dry, defensible land are all determined by the local geology. Information in this memoir, and in the thematic report for the Nottingham urban area by Charsley et al. (1990), shows how geology can be applied to the effective, safe and environmentally sound development of these resources. It also provides an overview of the stratigraphy and structure, which should be of interest to amateur and professional geologists alike.
Mineral exploitation has long been important to the local economy and at present is mainly represented by the extraction of sand and gravel, brick clay and gypsum. Coal resources are present at depth and have been extensively mined in the past, although there is no current activity within the district. The concealed Carboniferous rocks are important targets for hydrocarbon exploration. The subsurface geology and structure of the district are therefore important themes, and their investigation has been facilitated by the numerous deep boreholes and seismic reflection traverses conducted in support of mineral exploration.
This memoir synthesises a mass of information for the Nottingham district, and also contains much hitherto unpublished material. Many specialist contributions highlight the emphasis placed by the current BGS programme on a multidisciplinary approach to geological mapping. It represents a major advance in the understanding of the geological history and structure of the district, and I am confident that it will play its part for many years to come in serving the needs of the scientific, planning, commercial and academic communities.
This memoir describes the surface and subsurface rocks of the geological map Sheet 126, together with various aspects of the geophysical and geological structure. The district extends north-eastwards from Nottingham to the outskirts of Newark, and includes the towns of Radcliffe on Trent, Bottesford and Southwell.
Apart from a small outcrop of Carboniferous rocks in the Radford area of Nottingham City, the strata at outcrop comprise a south-eastward dipping succession of Permian, Triassic and Lower Jurassic rocks. Detailed accounts are given of the Permian and Triassic groups, formations and members, and many type localities and reference sections lie within this district. The basal Triassic rocks include thickly developed sandstones that are major aquifers, replenished from their wide outcrop in the west and north of the district and present at depth elsewhere. The upper part of the Triassic sequence is largely red-brown mudstone and includes gypsum beds that have been exploited by both opencast and underground mining.
The district has been affected by only one glaciation, during the Anglian stage (MIS 12) of the Quaternary. Few outcrops of unconsolidated glacial deposits now remain, since most were removed by a sustained, largely post-Anglian period of downcutting that has moulded the present landscape. The most notable legacy of this erosion was the formation of the wide, flat-bottomed floodplain of the river Trent, and of the many large and small tributaries of that river system. Detailed Quaternary mapping of the Trent floodplain has shown a history of at least four separate phases of aggradation, including that of the modern alluvium, which have left their mark in a series of river terrace deposits, both within and adjacent to the floodplain. Such deposits are important as aquifers and as sand and gravel resources. They also delineate areas of raised ground, and their depiction on geological maps can thus help to estimate the severity of flooding that is likely to occur at a given locality.
The memoir outlines a number of potential natural geological hazards within the district, such as the possibility of near-surface gypsum solution, radon gas emission, shrink-swell clays and flooding. It also describes the man-made hazards, including, for example, ground subsidence in the former mining areas and the local contamination of water supplies by rising mine-water discharges. A further hazard, unique to the Nottingham City area, is that many caves hewn out of the Sherwood Sandstone have weak roofs and periodically cause collapses at ground level.
Many of the above factors are of relevance to farmers or conservationists in planning the management of the land, to planners considering the location of constructional or trunk route developments, and to hydrogeologists concerned with groundwater and pollution management. There is also an increasing need to provide insurers with geoscience information that can be used to assess the risk factor imposed by the geology over large areas or in site-specific case studies.
The most recent 1:50 000 geological map of the Nottingham district, published in 1996 and described in this memoir, was compiled from 1:10 000 National Grid Sheets following detailed geological surveys and data acquisition in the district between 1987 and 1994. The 1:10 000 National Grid Sheets included in the compilation are listed in Information sources, together with the names of the surveyors, the dates of survey and reference numbers of the accompanying Technical Reports.
The most recent 1:10 000 scale surveys augmented a study commissioned by the then Department of the Environment into the geology and applied geology of Nottingham City and its environs. The results of this work provide the earth-science background to all aspects of land-use and mineral resource planning, and are contained in the Technical Report by Charsley et al. (1990), complementary to this memoir. Other BGS data covering the district, including maps, reports and digital material, are given in the Information sources section.
The geology of the district consists of three major components, namely bedrock, superficial deposits or drift, and man-made deposits. Bedrock is usually exposed only in man-made excavations, including quarries, pits, drainage ditches or boreholes; natural exposures are relatively rare. Superficial deposits, generally consisting of unconsolidated sediments such as clay, sand or gravel, are also rarely exposed. They may completely cover the bedrock to depths of several metres, as beneath the River Trent floodplain, or be thin and patchy in their distribution, as in the Nottingham City area. Man-made deposits are likely to occur wherever the land surface has been re-modelled or landscaped by the activities of man, and are widespread in all areas of human settlement.
The geological formations described in this memoir are listed on the inside of the front cover. The simplified geological map (Figure 1) shows the distribution of rock strata at the surface or at rockhead (i.e. the rocks below drift deposits). A cross-section of the strata beneath the district (e.g. section 2 at foot of 1:50 000 Sheet 126) shows that they dip gently towards the east-south-east or south-east, at an angle of 1 to 2. Consequently, the oldest Permian rocks of the Cadeby Formation crop out in the extreme north-west and west of the district, with the youngest Jurassic rocks of the
Lias Group restricted to the extreme south-east. Apart from a small area of Radford, Nottingham, where Upper Carboniferous rocks (Coal Measures) occur at the surface, Carboniferous strata are concealed beneath Permian or younger rocks, and are therefore encountered only in boreholes or underground mines.
The structure of the concealed Carboniferous rocks is more complex than that of the overlying Permian and younger rocks, from which they are separated by an unconformity. The Carboniferous rocks are gently folded into a series of low-amplitude dome and basin structures, superimposed on a gentle regional dip of 1 to 4 to the north-east. They are also disturbed to a greater extent by faults than the overlying Permian and younger strata.
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