The sand and gravel resources of the country around Whittlesey, Cambridgeshire : description of 1:25,000 resource sheets TF 20 and TL 29

The geological maps of the Institute of Geological Sciences, pre-existing borehole information, and 186 boreholes drilled for the Industrial Minerals Assessment Unit form the basis of the assessment of the sand and gravel resources of the country around Whittlesey, Cambridgeshire. All the deposits in the resource sheet area that might be potentially workable for sand and gravel have been investigated and a simple statistical method has been used to estimate the volume. The accompanying 1:25 000 map is divided into nine main resource blocks. The geology of the deposits is described and the mineral-bearing areas within each block are distinguished by sub-blocks. The mean thicknesses of overburden and mineral and the mean gradings, together with detailed borehole data, are also given. The geological lines and symbols, the positions of all non-confidential boreholes used in the assessment (and grading information for most IMAU boreholes) and the outlines of the resource blocks and sub-blocks are shown on the accompanying Map. The principal mineral resources are First Terrace fluviatile gravels (up to 8.2 m thick) and their marine/estuarine facies; boreholes indicate that the latter is more extensive than hitherto known. The thickness of the overburden in the central part of the resource sheet area increases towards the east and south and in the northern part towards the north-east. The survey supports a twofold altimetric subdivision of the 'Fen Gravel' and indicates that those gravels which are equated with the Nene Second Terrace represent a continuation westwards of the March Gravels. The drilling occasionally encountered a 'leaf' of the Lower Peat and indicated an eastwards extension of the Tinwell-Marholm Fault.