The sand and gravel resources of the country west of Darlington, County Durham : description of 1:25,000 resource sheet NZ 11 and 21

The geological maps of the Institute of Geological Sciences, pre-existing borehole information, exposures and 41 boreholes drilled for the Industrial Minerals Assessment Unit, form the basis of the assessment of sand and gravel resources of an area in N ort~ Yorkshire and County Durham, west of Darlington. All deposits in the area which might be potentially workable for sand and gravel have been investigated and a simple statistical method has been used to estimate the volume. The reliability of the volume estimates is given at the symmetrical 95 per cent probability level. The 1 :25 000 map is divided into three resource blocks containing respectively 5.3, 9.2 and 9.9 km2 of potentially workable sand and gravel. For the blocks assessed statistically the geology of the deposits 1s described and the mineral-bearing area, the mean thickness of overburden, mineral and waste and the mean grading of the mineral are stated. Detailed borehole data are given. The geology, the pos1t1on of the boreholes and the outlines of the resource blocks are shown on the accompanying map.