Whitchurch and Malpas, Clwyd, Cheshire and Shropshire
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INSTITUTE OF GEOLOGICAL SCIENCES Mineral Assessment Report 136 Natural Environment Research Council Tatten hall 0 The sand and gravel I SJ 55 resources of the country 1sJ 45 around Whitchurch and - Wrexham f Malpas, Clwyd, Cheshire k? Malpas and Shropshire SJ 44 SJ 54 Whitchurch 0 Description of I :25 000 sheet SJ 44, 54 St. Martins Welshampton 0 SJ 33 \ !J 43 SJ 53 Prees I. Jackson, Q. J. Lowe, A. N. Morigi and S. J. Mathers Contributor A. A. Wilson 0 Crown copyright 1983 ISBN 0 11 884436 9" London Her Majesty'sStationery Office 1983 PREFACE The first twelve reports on the assessment of British National resources of many industrial minerals may seem sand and gravel resources appeared in the Report Series so large that stocktaking appears unnecessary, but the of the Institute of Geological Sciences as a subseries. demand for minerals and for land for all purposesis Report No. 13 and subsequent reports appear as Mineral intensifying and it hasbecome increasingly clear in Assessment Reports of the Institute. recent years that regional assessments of the resources of these minerals should be undertaken. The publication Details of published reports appear at the end of this of information about the quantity and quality of deposits Report. over large areas is intended to provide a comprehensive factual background against which planning decisions can Any enquiries concerning this report may be addressed to be made. Head, Industrial Minerals Assessment Unit, Sandand gravel, considered together as naturally Institute of Geological Sciences, Nicker Hill, occurring aggregate, was selectedas the bulk mineral Keyworth,Nottingham NG12 5GG. demanding the most urgent attention, initially in the south-east of England,where about half the national output is wonand very few sources of alternative aggregates are available. Following a short feasibility project,initiated in 1966 by the Ministry ofLand and Natural Resources, the Industrial MineralsAssessment Unit (formerly the Mineral Assessment Unit) began sys- tematic surveys in 1968. The work is now being financed by the Department of the Environment andis being undertaken with the co-operation of the Sand and Gravel Association of Great Britain. This report describes the resources of sand and gravel of 200 km2 of country around Whitchurch and Malpas, in the counties of Clwyd, Cheshire and Shropshire, shown on the accompanying resource map.The survey was supervised by I. Jackson, and carried out by him, S. J. Mathers, D. J. Lowe and A. N. Morigi. The work is based on a six-inch geological survey by E. G. Poole, A. J. Whitemanand D. Magrawin 1955-57. A. A. Wilson has substantially amended the solid geological lines and contributed the account of the solid geology. J. D. Burnell, ISO,and G. I. Coleman (Land Agents) wereresponsible for negotiating access to land for drilling.The ready co-operation of landowners and tenants in this work is gratefully acknowledged. P. A. Sabine Acting Director Institute of Geological Sciences Exhibition Road London SW7 2DE 24 January 1983 ii CONTENTS SUMMARY 1 TABLES 1 Geological sequence 4 INTRODUCTION 1 2 Lithological analyses of the +8 -32 mm DESCRIPTION OF THE DISTRICT 3 gravel 8 Topography 3 3 Sand and gravel resources of the Geology 3 district 10 Composition of the Sand and Gravel Deposits 8 4 Block A: data from IMAU boreholes 11 The Map 9 5 Block B: data from IMAU boreholes 12 Results 10 6 Block C: data from IMAU boreholes 13 Notes on the Resource Blocks 10 7 Block D: data from IMAU boreholes 13 8 Block E: data from IMAU boreholes 14 CONCLUSIONS 16 9 Block F: data from IMAU boreholes 15 REFERENCES 16 10 Block G: data from IMAU boreholes 15 Appendix A: Field and laboratory procedures 18 Appendix B: Statistical procedure 19 Appendix C: Classification and description of sand and gravel 20 Appendix D: Explanation of the borehole records 22 Appendix E: Industrial Minerals Assessment Unit borehole records 24 FIGURES 1 Sketch map showing the location of the district 2 2 Topography of the district 3 3 Sketch map showing the solid geology of the district 4 4 Sketch map showing the drift geology of the district (after Poole and Whiteman) 5 5 Generalized thickness of drift 6 6 Particle-size distribution of a sandy till 7 7 Mean particle-size distribution for the assessed thickness of sand and gravel in resource blocks A to G 9 8 Grading characteristics of the mineral in Block A 11 9 Grading characteristics of the mineral in Block B 11 10 Grading Characteristics of the mineral in Block C 12 11 Grading characteristics of the mineral in Block D 12 12 Grading characteristics of the mineral in Block E 13 13 Grading characteristics of the mineral in Block F 13 14 Grading characteristics of the mineral in Block G 16 MAP The sand and gravel resources of the country around Whitchurch and Malpas, Clwyd, Cheshire and Shropshire. in pocket iii The sand and gravel resourcesof the country around Whitchurch and Malpas, Clwyd, Cheshireand Shropshire Description of 1:25 000 sheet SJ 44,54 I. Jackson, D. J. Lowe, A. N. Morigi and S. J. Mathers SUMMARY INTRODUCTION The geological mapsof the Institute of Geological The survey is concerned with theestimation of Sciences, pre-existing borehole information and 99 bore- resources, which include deposits that are not currently holes drilled for the Industrial Minerals Assessment Unit exploitable buthave a foreseeable use, rather than form the basis of the assessment of the sand and gravel reserves, which can onlybe assessed in the light of resources of the country around Whitchurch and Malpas. current, locally prevailing, economic considerations. The glacial sediments of thedistrict proved to be Clearly, neither the economic nor the social factors used more complex than is shown on the published geological to decide whether a deposit maybe workable in the map. Glacial Sand and Gravel, present over much of the future can be predicted; they are likely to change with area in the south and east, showsrapid lateral and time. Deposits not currently economically workable may vertical variation in compositionalthough sand-grade be exploited as demand increases, as higher-grade or deposits predominate. Recorded thicknesses of over- alternativematerials become scarce, or as improved burden and waste also have a wide range. processing techniques are applied to them. The improved All the deposits in the district that might be poten- knowledge of the main physical properties of the tially workable for sandand gravel havebeen investi- resource and their variability, which this survey seeks to gated and a simple statistical method has been used to provide, will add significantly to the factual background estimate the volume.The reliability of the volume against which planning policies can be decided (Archer, estimates is given at thesymmetrical 95 per cent 1969; Thurrell, 1971, 1981; Harris and others, 1974). probability level. The survey provides information at the 'indicated' and The 1:25 000 map is divided into 7 resource blocks, 'inferred' levels. 'Indicated' assessments "are computed containing between 2.9 and 37.2 km2 of sand and gravel. partly from specific measurements, samples or produc- For each block the geology of the deposits is described, tion data and partly from projection for a reasonable and the mineral-bearing area,the mean thicknesses of distance on geologic evidence. The sites available for overburden and mineral and the mean gradings are inspection, measurement, and sampling are too widely or stated. Detailed borehole data are also given. The geo- otherwise inappropriately spaced to permit the mineral logy, the position of the boreholes and the outlines of the bodies to be outlined completely or the grade established resource blocks are shown on the accompanying map. throughout". 'Inferred' assessments are those "based largely on broad knowledge of the geologic character of the deposit and for which there are few, if any, samples Notes ormeasurements." (Bureau ofMines and Geological Each borehole registered with the Institute is identified Survey, 1948, p 15). by a four-element code (e.g. SJ 44 SE8). The first two It follows that the whereabouts of reserves must still elements define the 10-km square (of the National Grid) be established and their size and quality proved by the inwhich the boreholeis situated; the third element customary detailed exploration and evaluation under- defines a quadrant of that square, and the fourth is the taken by the industry.However, the information pro- accession number of the borehole. In the text of the vided by this survey should assist in the selection of the report the borehole is normally referred to by the last best targets for such further work.The following arbit- three elements alone (e.g. 44 SE 8). rary physical criteria have been adopted: All National Grid references in this publication lie a The deposit should average at least 1 m in thickness. within the 100-km square SJ unless otherwise stated. b The ratio of overburden to sand and gravel shouldbe Grid references are given to eight figures, accurate to no more than 3:l. within 10 m, for borehole locations. (In the text, four- c The proportion of fines (particles passing a 0.063 mm and six-figure grid references are used for more exten- B.S. sieve) should not exceed 40 per cent. sive locations, for example for farms). d The deposit should lie within 25 m of the surface, this being taken as the likelymaximum working depth under most circumstances. It follows from the second criterion that boreholes are drilled no deeper than 18 m if no sand and gravel has been proved. A deposit of sandand gravel that broadly meets these criteria is regarded as 'potentially workable'and is Bibliographical reference described and assessed as 'mineral' in this report.