Abstract

Techniques used in four major sand and gravel resource analyses in the UK are described. For each survey, an archive of pre-existing borehole data was assembled. Borehole distribution may be uneven and, in glaciated terrains, they may be concentrated in the valleys and absent from positive geomorphological features, which might represent the major resources. Satellite imagery may be useful for assessment of coastal resources and was also used to illustrate the environmental context of deposits but it is unreliable as a predictive tool in the UK. Geomorphological surveys provided a rapid cost-effective method for identifying potential resources, particularly in glaciated terrains with prominent landforms. Geophysical techniques were less successful. Seismic surveying was expensive and did not provide consistently accurate results. Resistivity surveys were used and an experiment was devised to assess their accuracy. For this, detailed logs were provided for ten boreholes to allow on-site instrument calibration, then another ten borehole locations were given but without geological data. Resistivity estimates at the latter borehole locations overestimated overburden by 39% and depth to bedrock by 340ut underestimated mineral thickness by 29%. Hydrogeological data were collected as part of the data bases and gave a broad indication of likely groundwater conditions existing in most resource areas. Resource criteria used in previous IMAU assessments are considered insufficiently stringent and, in particular, an upper limit for mineral of 40 0.000000ines is considered too high and a reduction to 20uggested. This would significantly reduce the volumes of some previously estimated resources. Within the areas surveyed here, the reduction in mineral volume would vary from 5 0n the Lleyn to 77 0n Harbury-Kineton. Planning analyses have been undertaken as part of three of these surveys and provide useful information on likely constraints to exploitation but they must avoid compromising the County Councils in their role as Minerals Planning Authorities. Techniques of data presentation are crucial to success in reaching a wider audience and the usefulness of three-dimensional diagrams is indicated.

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