NATURAL ENVIRONMENT RESEARCH COUNCIL

INSTITUTE OF GEOLOGICAL SCIENCES

Report No. 73/8

ASSESSMENT OF BRITISH SANDAND GRAVEL RESOURCES No. 7

The sand and gravel resources of the country around Layer Breton and Tolleshunt D'Arcy, Essex

Description of 1 : 25 000 resource sheet TL 91 and part of TL 90

J. D. Ambrose, BSc

London: Her Majesty's Stationery Office 1973 The Instituteof Geological Sciences was formed by the incorporation of the Geological Survey of Great Britain and the Museum of Practical Geology with Overseas Geological Surveys and is a constituent body of the Natural Environment Research Council.

0 Crown copyright1973

It is recommended that reference to this report be made in the following form: AMBROSE,J. D. 1973. The sand and gravel resources of the country around Layer Breton and Tolleshunt D’Arcy, Essex: Description of 1 : 25 000 resource sheet TL 91 and part of TL 90. Rep. Inst. Geol. Sci., No. 73/8. 34 pp.

SBN 11 880614 9

ii Preface

It has become increasingly clear in recent years that an assessment of resources of many minerals should be undertaken. This is a report of the Mineral Assessment Unit which was set up in May 1968 to undertake such work. It describes and quantifies the resources of sand and gravel of 125. 5 km 2 of country around Layer Breton and Tolleshunt D'Arcy shown on the accompanying 1:25 000 resource sheet TL 91 and part of TL 90.

This survey is concerned with assessing sand and gravel resources on a regional scale at the indicated level; the deposits are not outlined completely nor their grade established throughout. The work may be regarded as the application to large areas of methods used commercially for evaluating reserves on small sites. It may also be regarded as an extension of geological mapping by providing information about the thickness and quality of deposits.

The survey was conducted by Mr J.D. Ambrose assisted by Mr N.E. Bradbury as field officer who supervised the drilling and sampling programme, and Mr G. M. Bladon who helped in the preparation of data for this publication. The work is based on a geological survey at the scale of 1:lO 560 in 1966-67 by Dr C.R. Bristow (East Anglia and South- East England Field Unit) who has also helped in the geological interpretation.

Mr J. W. Gardner, C, B, E. (Land Agent) has been responsible for negotiating access to land for drilling. The ready cooperation of land owners and tenants in this work is gratefully acknowledged. Special thanks are due to Dr T. L. Thomas of the Royal School of Mines, London, for his advice on methods of resource calculation. Financial support for the survey was provided by the Department of the Environment.

Kingsley Dunham Director

Institute of Geological Sciences Exhibition Road South Kensington London SW7 2DE

17 July 1972

Any enquiries concerning this report maybe addressed to Head, Mineral Assessment Unit, Instituteof Geological Sciences, Exhibition Road, LondonSW72DE

iii

CONTENTS

Page

INTRCIDUCTION Aims and Limitations Procedure The Map

DESCRIPTION OF SHEET TL 91 A.ND PA.RT OF TL 90 General Topography Geology Composition of the Sand and Gravel Deposits Results Notes on Resource Blocks A. and B List of Quarries

REFERENCES 9

A.PPENDIX A,: ASSESSMENT PROCEDURE 11

A.PPENDIX B: CLA.SSIFICA.TIONA.ND DESCRIPTION OF SA.NDA.ND GRA.VEL 14

A.PPENDIX C: BOREHOLE RECORDS 17 Explanation 17 List of Mineral Assessment Unit Boreholes 19 The Records 20

1LLUSTRA.TIONS

Fig. 1. Sketch map showing the location of sheet TL 91 and part of TL 90 and the position of the resource block boundaries 5

Fig. 2. Particle size distribution for the assessed thicknessof sand and gravel in the resource blocks A, and B 7

Fig. 3. Example of resource block, assessment: statement and calculation 12

Fig.4. Example of resource block assessment: map of a fictitious block 13

Fig. 5. Diagram showing the descriptive categories used in the classification of sand and gravel 16

Map The sand and gravel resources of sheet TL 91 and part of sheet TL 90 (Layer Breton and Tolleshunt D'Arcy, Essex) In pocket

TA.BLES

Table 1. Geological classification 4

Table 2. The sand and gravel resources of the area 8

Table 3. List of quarries in report area 9

Table 4. Classification of gravel, sand and fines 15

V Summary

The geological maps of the Institute of Geological Sciences, pre-existing borehole information, and seventeen boreholes drilled for the Mineral Assessment Unit form the basis of the assessment of sand and gravel resources in the Layer Bretonand Tolleshunt D'Arcy areas of Essex.

All deposits which might be potentially workable for sand and gravel (mineral) have been investigated geologically and a simple statistical method has been used to estimate the volume. The reliability of the volume estimates is given at the 95 per cent confidence level.

Two resource blocks, containing 8.9 and 9.1 km2 of sand and gravel, have been recognised. For each block the mineral-bearing area, the mean thickness of overburden and mineral, and the mean grading are given and the geomorphology and geology of the deposits described.

The position of the boreholes and exposures, the geology and topography and the outlines of the blocks are shown on the accompanying map. Detailed borehole data are given.

Sommaire

Les cartes g6ologiques de l'lnstitute of Geological sciences, les renseigmements sur des , trous'desonde qui existaient d6j&, etdix-sept trous de sonde for6s pour le Mineral Assessment Unit, constituent la base de l'dvaluation des ressources en sable et en gravier dans les regions de Layer Breton et de Tolleshunt DIArcy..$n Essex.

Tous les dkp6ts qui pr6sentent la possibilitk d'exploitation pour le sable et le gravier (mineral) ont 6t6 6tudi6s de point de vue geologique et on s'est servi d'une mkthode statistique simple pour en 6valuer le cubage. Les gvaluations de volume sont tenues dl&re B 95 pour cent exactes.

On a reconnu deux blocs de ressources, qui comprennent 8.9 et 9.1 km2 de sable et de gravier. On donne pour chaque bloc lletendue mineralisee, l'epaisseur moyenne de recouvrement et de mine'ral et la gradation moyenne. On d6crit aussi la gdomorphologie et la gkologie des d6p6ts.

La situation des trous de sonde et des affleurements, la g6ologie et la topographie, et la configuration des blocs sont montrkes sur la carte. Des donnees detailldes des trous de sonde sont prdsentges.

Zusammenfassung

Die geologischen Karten von der Institute of Geological Sciences, vorherexistierende Information, und siebzehn Bohrlocher, die fur die Mineral Assessment Unit gebohrt wurden, bilden den Grund fur die Einschatzung der Sand- und Schottermittel in den Layer Breton und Tolleshunt D'Arcy Gebieten in Essex.

Man hat im Gebiet alle Ablagerungen, die moglich bearbeitbar fur Sand und Schotter (Mineral) sind, geologisch untersucht, und man hat eine einfache Methode benutzt, urn das Volumen zu schatzen. Man gibt die Zuverlassigkeit der Volumenschatzungen mit 9 5 Prozent Vertrauensgrenzwerten.

Man erkannte zwei Mittelsblocke, die 8.9 und 9.1 km2 von Sand und Schotter einschtiessen.

Man gibt fur jeden Block das mineralhaltige Gebiet, die Durchschnitts dicke von Uberlastung und Mineral, und die Durchschnitts-klassifizierung, Die Geomorphologie und Geologie der Ablagerungen wurden beschriben.

Man zeigt die Lage von den Bohrlochern und Aufschlussen, die Geologie und Topographie und auch die Skizzen von den Blocken auf der Begleitkarte.

Aus fuhrliche Bohrlocherdaten werden gegeben.

vi The sand and gravel resources of the country around Layer Breton and Tolleshunt D'Arcy, Essex

Description of 1 : 25 000 resource sheet TL 9 1 and part of TL 90

J. D. AMBROSE,~BSc

Introduction measurement, and sampling are too widely or otherwise inappropriately spaced to permit the AIMS AND LIMITATIONS mineral bodieS to be outlihed completely or the National resources of many of the 'bulk' or gradeestablished throughout' (Anon, 1948, 'industrial' minerals may seem so large that p. 15). stocktaking is unnecessary, but the demand for land for all purposes and tor minerals is The survey is therefore concerned not with intensifying. In contrast with other developments the estimation of reserves (which can only be of land there may be little or no choice of area assessed in the light of particular or existing for the working of minerals andlin the caseof economic considerations), but rather with low-price materials such as sand and gravel resources, which include deposits not currently transport costs will be an important factor. exploitable but having a foreseeable use. Whereas the economic benefit of using land for Clearly, the social and economic criteria used many other purposes can be assessed, hitherto to decide whether a deposit may be workable at little has been khown of the potential value, on some time in the future cannot be rigorously a regional scale, of any mineral resources defined. After discussion with the industry, the which may be present. An important aim of the following arbitrary physical criteria were work is to improve the factual background adopted for this survey: against which planning policies can be decided a. the deposit should average at least 3 ft (Archer, 1969; Thurrell, 1971). (0.9 m) in thickness. b. the ratio of overburden to sand and gravel Sand and gravel, considered together as should be no more than 3: 1. naturally occurring aggregate, was selected as c. the proportion of fines (that is, particles the bulk mineral demanding the most urgent pasping 1/16 mm (approximately No. 200 mesh attention, particularly in the south-east of B. S. sieve) ) should not exceed 40 per cent. England, where about half the national output is won and very few sources of alternative aggre- Ground below 80 ft (24.4 m) from the surface gates are available. Following a short feas- is seldom explored, this being taken as the ibility project, initiated in 1966 by the Ministry likely maximum working deptli under most cir- of Land and Natural Resources, the Mineral cumstances. It follows that boreholes are Assessment Unit began systematic surveys on drilled no deeper than 60 ft (18.3 m) if they are a regional scale in Essex, Suffolk, and PJorfolk still in overburden. in May 1968. The work is being supported by the Department of the Environment (which A deposit of sand and gravel that broadly incorporates the former Ministry of Housing and fulfils the above criteria is considered to be Local Government and the Ministry of Public 'potentially workable' and is assessed as Building and Works) and is being undertaken 'mineral'. It is recognised that small parts of with the cooperation of the Sand and Gravel such a deposit may not satisfy all the require- Association of Great Britain (SAGA). The detail ments. is at the 'indicated' level, a term introduced in the United States in connection with the The volume and chief characteristics of sand estimation of national mineral resources. The and gravel within defined but relatively large level is that 'for which tonnage and grade are areas, referred to as resource blocks, are computed partly from specific measurements, assessed.Ideally, each resource block contains samples, or production data and partly from roughly 10 square kilometres of sand and gravel. projection for a reasonable distance on geological evidence. The sites available for inspection, The consequent limitation of the use to which the results can be put must be emphasised. The 'Institute of GeologicalSciences, 199 Knightsbridge, assessments of quantity and composition apply London SW7 1DZ to the resource block as a whole.

1 Valid conclusions cannot be drawn sample-points at a density of approximately one about the mineral in parts of a block, per square kilometre. Ideally the distribution except in the immediate vicinity of should be unbiassed with respect to the geology, the actual sample points. to ensure that the data obtained are representative of any broad trends in the variation in thickness It follows that reserves, which are accurately or grading, as this will govern spot values. demarcated areas of economically workable mineral, must be proved by the customary However, because broad trends are indepen- detailed exploration undertaken by the industry. dently overlaid by smaller scale variations, However, the information provided about the characteristically random in form, it is resource blocks in an area may assist in the unnecessary to adhere to a square grid pattern. selection of the best targets for such commercial Thus such factors as ease of access and the exploration and evaluation. need to minimise disturbance to land and the public have been taken into account in siting the Thus the work can be regarded as the statis- holes: at the same time it has been necessary tically controlled application to large areasof to guard against the possibility that ease of methods similar to those applied by industry to access (that is, the positions of roads and farms) establish the existence of workable reserves on may reflect particular geological conditions, a relatively small site, and also as an extension which may bias the drilling results. In siting of conventional geological mapping techniques, the boreholes and in the subsequent calculations, which delineate (with varying degrees of no account is taken of any factors, for example, accuracy, depending, for example, on the roads, villages and areas of high agricultural presence of cover) the areal extent of deposits. and landscape value, which might stand in the way of sand and gravel being exploited. The PROCEDURE estimate of total volume of sand and gravel Trial and error during preliminary studies therefore bears no simple relationship to the showed that for the complex and variable glacial amount that could be extracted in practice. deposits of East Anglia and Essex, an a-bsolute minimum of five sample-points evenly distri- Ideally the drilling machine employed should buted across the sand and gravel are needed to be capable of providing a continuous sample provide a worthwhile statistical assessment, representative of all unconsolidated deposits, but that, ideally, there should be no fewer than so that the in-situ grading can be determined, if ten. Sample-points are any points for which necessary, to a depth of 100 ft (30 m) at a there exists adequate information about the diameter of about 8 in (200 mm), and beneath nature and thickness of the deposit and, apart differenttypes of overburden.It should be from the holes drilled during the survey, may reliable, quiet, mobile and relatively small (so include exposures and other boreholes. In that it can be moved to sites of difficult access) particular, the cooperation of sand and gravel and it should be fast. Although uncased con- operators has ensured that boreholes have not tinuous flight power augers can meet these been drilled where reliable information was requirements in some ground, they fail below already available, Such data are held con- the water table, in some clay-free sand and fidentially by the Institute and cannot be dis- gravel when the mineral does not stay on the closed, although they may have been used in the flights, or when theborehole caves. On the calculations. area covered by this sheet, the German Wirth B1 drill (or BO modified) was used extensively. The mineral shown on each 1:25 000 sheet is With this machine, casing can be advanced at dividedinto resource blocks. The arbitrary the same time as the hole is being drilled, thus size selected, 10 km2, is a compromise to minimising disturbance to the ground, and meet the aims of the survey and to provide avoiding contamination and caving. In difficult sufficient sample-points in each block. As far ground a bailer can be substituted for the auger, as possible the block boundaries are determined although this method suffers from the disadvan- by geological boundaries; for example, wherever tage that there is a tendency for the pumping practicable glacial and river terrace gravels action to draw unwanted material into the hole are separated. Otherwise division is by either from the sides or the bottom. A con- arbitrary lines which may bear no relationship ventional 'shell and auger' machine has also to the geology. The blocks are drawn pro- been used. visionally before drilling begins. A continuous series of bulk samples is taken A reconnaissance of the ground is carried throughout the thickness of sand and gravel. out to establish whether there are any exposures, Ideally, samples are composed exclusively of the and inquiries are made to ascertain what bore- whole of the material previously occupying the hole information is available. Borehole sites space defined by the hole's ideal dimensions, as are then selected to provide an even pattern of determined by the internal diameter of the casing and the thickness penetrated. A new sample is absent. (For definitions of 'mineral' and commenced whenever there is an appreciable 'potentially workable' see page 1). The mineral lithological change within the sand and gravel, is subdivided into areas where it crops out and or for every 3 ft (0. 9 m) of depth. The samples areas where it is present in continuous (or are despatched in heavy4uty polythene bags to almost continuous) spreads beneath overburden. a laboratory for grading. Care is taken to dis- The whole area of exposed sand and gravel as card, as far as possible, material which has mapped is considered as mineral, although there caved, or been pumped from the bottom of a may be small patches where sand and gravel is hole. The samples sent for analysis each weigh absent or not potentially workable. 60-100 lb (27-45 kg). The grading procedure is based onBS 1377 (Anon,, 1967). Random checks Beneath overburden mineral may be con- are made on the accuracy of the laboratory tinuous (or almost continuous) or discontinuous. grading. The recognition of these categories is subjective, depending on the importance attached to the All data, including mean grading analysis proportion of boreholes which did not find poten- figures calculated fo-r the total thickness of the tially workable sand and gravel and the distri- mineral, are entered on standard record sheets, bution of barren boreholes within a block. The abbreviated copies of which are reproduced in mineral is described as 'almost continuous' if Appendix C. Detailed records may be consulted it is present in 75 per cent or more of the bore- at the appropriate offices of the Institute, upon holes in a resource block. The 'discontinuous' application to the Director. category has not been recognised on the present sheet. The methods used in estimating the volume of mineral and other statistics for each of the Areas where bedrock crops out, where bore- resource blocks are described in A.ppendix A. and holes indic ate absence of sand and gravel the results are quoted on page 8. beneath cover, where sand and gravel beneath cover is interpreted to be not potentially workable THE MAP and areas not assessed, are uncoloured on the The sand and gravel resource map is folded map, and where appropriate, the relevant into the pocket at the end of this report. The criterion is noted. In such areas it is assumed base map is the Ordnance Survey 1:25 000 Out- that mineral is absent except in infrequent and line Edition in grey, on which the topography is relatively minor patches which can neither be shown by contours in green, the geological data outlined nor assessed quantitatively in the in black and the mineral resource information context of this survey. in shades of red. The area of exposed sand and gravel is GEOLOGICAL DATA measured from the mapped geological boundary The geological boundary lines, symbols, etc. , lines. Inferred boundaries have been inserted shown are taken from the geological map of the around areas where sand and gravel beneath area, which was surveyed recently at the scale cover is interpreted to be not potentially workable of 1:lO 560. This information was obtained by or absent. Such boundaries, for which a dis- detailed application of field mapping techniques tinctive symbol is used, are drawn primarily by the field staff in the Institute's East Anglia for the purpose of volume estimation. The andSouth-East England Unit. Borehole data, symbol is intended to convey an approximate which include the stratigraphic relations and location within a likely zone of occurrence mean particle size distribution of the sand and rather than to represent the breadth of the zone, gravel samples collected during the survey, are its size being limited only by cartographic also shown. considerations. For the purpose of measuring areas the centre-line of the symbol is used. The geological boundaries are regarded as Description of sheet TL 91 the best interpretation of the information availableat the time of survey.However, it and part of TL 90 is inevitable, particularly with glacial deposits GENERAL (such as those included in this area)which This is a composite sheet covering a total change rapidly vertically and laterally, that area of 125. 5 km2 and comprising the whole of local irregularities or discrepancies will be 1:25 000 sheet TL 91, and that part of 1:25 000 revealed by some boreholes (for example, at sheet TL 90 which lies north of the estuary of boreholes 91 NW 6 and 91 SW 4). These are the River Blackwater. Two sand and gravel- taken into account in the assessment of resources#. bearingblocks have been outlined, one in the north of 23.3 km2 containing 8.9 km2 of mineral, MINERAL RESOURCE INFORMATION and another in the south of 25.8 km2 containing For assessment purposes the map is divided 9.1 km2 of mineral. The remaining 76.4 km2 into areas of mineral and areas where sand and of the sheet consists of an undulating area which gravel is either not potentially workable or is mainly exposed London Clay, with a few

3 Table 1. Geologicalclassification.

Drift (Superficial formations) Recent and Pleistocene

Alluvium RiverTerrace Deposits - First Terrace of River Chelmer Second Terrace of River Chelmer Head Chalky Boulder Clay Glacial Sand and Gravel

Solid (Eocene)

London Clay

patches of Head and Alluvium, passing south- decreases to the north and west, so that in wards and south-eastwards into the flat marshes borehole 91 NW 7 it is at 147 ft (44.8 m) above and creeks bordering the Blackwater Estuary. 0. D,, while in 91 NW 1 it is at 48 ft (14.6 m) The only sand and gravel deposits in this area above 0. D. In the south the surface decreases are a few outliers of Glacial Sand and Gravel in height southwards, so that in 91 SW 3 it is near Peldon, too small to be assessed in this recorded at 73 ft (22.3 m) above O.D. and in survey. 90 NW 1 at 22 ft (6.7 m) above 0,D, Between these two areas, the surface appears to have TOPOGRAPHY been at its highest, London Clay being exposed The estuary of the River Blackwater and its at present at between 150 ft (45.7 m) and 200 ft associated creeks and marshes border the area (61.0 m) above 0, D. to the ‘south and south-east. To their north and west the land surface rises unevenly to form a Glacial Sand and Grauel low ridge at about 75 ft (22.9 m) to 90 ft (27.4 m) Resting directly on the London Clay, in both above sea level between Tollesbury and the northern and southern areas, are spreads Tolleshunt Major. Further north the unduiating of Glacial Sand and Gravel, but the borehole land surface rises to a maximum height of over information has revealed substantial differences 200 ft (61.0 m) above sea level at the western in composition and thickness of these deposits edge of the area near Harborough Hall [$IO0 18711. in the two areas. In the north the glacial in the extreme north-west the landis lower. deposits occur in a more or less continuous spread of about 10.0 m mean thickness and con- GEOLOGY tain considerably more sand than gravel. The The deposits present are listed instrati- variation in thickness of these deposits from graphical order in Table 1. The Lower London borehole to borehole can be related inverselyto Tertiaries and the Chalk have been proved only the thickness of the overlying Boulder Clay. In in deep boreholes. the south the Glacial Sand and Gravel occurs in a discontinuous, patchy spread and its mean London Clay thickness in the boreholes is only about 3.5 m The London Clay is the only solid formation although it is considerably more gravelly. represented at outcrop in the area, and it forms the bedrock upon which the younger, unconsoli- The difference in the mean thickness between dated,drift deposits lie. The drift cover, the two areas can probably be explained by the however, is discontinuous, being mainly con- fact that in the north much of the sand and gravel fined to the northern and southern parts of the has been protected from erosion by the Chalky area. When fresh the London Clay is firm and Boulder Clay cover, whereas in the south the bluish-grey in colour, but the top few feet are cover consists only of isolated patches of Head commonly weathered to a softer, streaky, brown which have not afforded the same degree of pro- clay. As the Mineral Assessment Unit bore- tection; indeed some of the sand and fines content holes were stopped on reaching London Clay, it may have been carried farther ‘afield leaving a is normally the brown, weathered layer which higher concentration of gravel in the south. is recorded in the borehole logs. Chalky Boulder Clay These logs show that in the north the height The Chalky Boulder Clay is brown or greyish-. of the sub-drift surface of the London Clay blue in colour and contains fragments of chalk, mainly angular, with a few flint pebbles of National Grid References in this.publication varying size. It is sometimes silty and has all lie within 100 kilometre square TL(52 distinctly gravelly bands in places. It rests

4 8:O r-7-lNORWICH + Sheet TL 82

COLCHESTER

I "s !0- Resource block A

Limits of report area sheet TL 91 and part of TL90 / / 0 0 1 GreatWigborough Sheet TL 81 +

.Virlev <

11-114 f' Resource block B'

Sheet TL 80

SCALE 0 1 2 3 miles 1 0 12345km directly on Glacial Sand and Gravel and cuts 43i ft (13.3 m) of mineral, while in borehole - down into it so thatwhere the Boulder Clay is 91 NW 3 the top 14 ft (4.3 m) of mineral has a thickest the sand and gravel is thinnest (and fines content of almost 30 per cent. vice versa). Near Smyth's Green [922 1871-the geological map shows the Boulder Clay resting The grading figures show vertical. and directly on London Clay, the sand and gravel lateral variation from fine to coarsewithin the being absent. gravel fraction in nearly all boreholes. No cobble-size material has been recorded in any Head of the holes drilled in this area. The pebbles Elsewhere the Glacial Sand and Gravel is are predominantly subangular to subrounded either exposed or covered by patches of Head, flints with subordinate subangular to rounded which is usually brown, sometimes silty clay, quartz and quartzites. often containing flint pebbles in varying propor- tions. While depositsmapped as Headhave On this sheet no information is available been recorded overlying Glacial Sand and Gravel about the composition of the Terrace Gravels in only four boreholes, several other holes have immediately north of the Blackwater Estuary. proved similar deposits which are probably too restricted in either thickness or extent to RESULTS warrant: mapping. The statistical results are summarised in Table 2. Fuller grading particulars are shown River Terrace Deposits in Fig. 2. In the extreme south of the area, alongside the Blackwater Estuary, River Terrace deposits Accuracy of Results occur. These are limited in extent and have not, For the two resource blocks A and B on therefore, been drilled. On an adjoining sheet, sheet TL 91 and part of TL 90 (excluding the TL 80 (Ambrose, 1973) however, similar inferred assessment of the River Terrace deposits have been found to contain substantial deposits) the tolerances at the 95 per cent con- amounts of gravel and an inferred assessment fidence level on the estimate of volume are has been made of these deposits, based on %40 and 33 per cent respectively (that is, it is experience gained from that sheet. A remnant probable that nineteen times ouk of twenty the of an older terrace occurs in the north-west true volume present lieswithin these limits). [900 1901; it is of no economic importance (see However, the true values are more likely to be Haggard, 1972). nearer the figure estimated than the limits. Moreover, it is probable that in each block Alluvium roughly the same percentage limits would apply The youngest deposits in the area are the for the estimate of volume of a very much River Alluvium, which occurs flooring the main smaller parcel of ground (say, 200 acres) con- valleys, and the Marine Alluvium, found bor- taining similar sand and gravel deposit s if the dering the Blackwater Estuaryand its associated results from the same number of sample points creeks in the south and east. (as provided by, say, ten boreholes) were used in COMPOSITION OF THE SAND AND ,the calculation. Thus, if closer limits are GRAVEL DEPOSITS needed for the quotation of reserves of part of Most of the potentially workable sand and a block, it can be expected that data from more gravel is Glacial Sand and Gravel, the mean than ten sample-points will be required, even if grading of which, from the borehole evidence, the area is quite small. is fines 6 per cent, sand 63 per cent, gravel 31 per cent, but the mean grading for resource It should be noted that in Table 2 confidence block A shows a ratio of sand to gravel of limits have not been quoted for the estimate of almost 3:l while in block B they are present in the combined volume of mineral in resource approximately equal proportions. The higher blocks A and B because the standard deviation gravel content in block B is accompanied by an for thickness is greater for the combined area increase in the coarseness of the sand; fine than it is for either of the blocks. Thus, the sand is rare. In block A, however, there is thicknesses of mineral recorded in the bore- often as much fine and medium grained sand. holes show a smaller variation about the mean The chief constituent of the sand in both blocks in each block than they do about the mean for the is subangular quartz, usually brown or grey- combined area of the blocks. brown, though iron-staining may give rise to a reddish-brown colour. It must again be emphasised that the quoted volume of sand and gravel has no simple Fines are normally present but their dis- relationship with the amount that could be tribution is very variable both laterally and extracted in practice, as no allowance has been vertically.For example, in borehole 91 NW 1 made in the calculations for any restraints (such there is only a trace of fines throughout the as existing buildings and roads) on the use of

6 100'

80

0 'A6 ?4 1 4 16mm Meanparticle size '46 z- 16

Block

Fig. 2. Particle size distribution for the assessed thickness of sand and gravel in the resource blocks A and B

7 Table 2. Sand and gravel resources of the area.

Statistical Assessment of Sand and Gravel Resources.

Limits at the 95y0 confidenceFines Sand Gravel level I million millior ft m ft m ft m3 yd3

18: 10.1 33 89.9 117.6 40 36.0 4 71 25

4$ 3.9 12g 35. 5 46.4 33 I 11.7 I 148145 125.4164.0

Inferred Assessment for Terrace Deposits(not included in statistical assessment above).

I-

Part of 1.2 c.l.3 c.1. 8 2.1 2. 7 Not determined B Speculative

the land for mineral working. ness of overburden varied from 48 ft (14.6 m) in 91 NW 5 to 5 ft (1.5 m) in 91 NW 3. NOTES ON RESOURCE BLOCKS A AND B Block A General trends in thickness are difficult to The mineral in this block is all Glacial Sand determine, but the borehole information suggests and Gravel which is concealed beneath Boulder that when mineral occurs beneath Boulder Clay Clay in the north-west. To the south-east of there is an inverse relationship between their the main spread there are several patchesof thicknesses.Thus, in boreholes 91 NW 1 and mineral, some very small; some, for example, 91 NW 2, the Boulder Clay is relatively thin at Layer Breton Heath, are partly concealed by but the mineral is thick whereas in borehole 91 Head. London Clay is exposed in the remainder NW 5 the overburden is thicker and the mineral of the block except where concealed by small is relatively thin. Away from the Boulder Clay areas of Head and Alluvium. outcrop both mineral and overburden thichesses are variable and no pattern can be discerned. Mineral has been proved in seven of the eight boreholes within this block, the exception The mean grading figures for the mineral in being 91 NW 4, where drilling was stopped the boreholes in this block are fines 4 per cent, after proving Boulder Clay to60 ft (18.3 m). sand 71 per cent, gravel 25 per cent. The The area in which the mineral is not considered figures for individual boreholes indicate that potentially workable because the ratio of over- the mineral contains a higher percentage of burden to mineral probably exceeds 3:l extends gravel in the north-west than to the southand onto the three adjacent 1:25 000 sheets (TL 81, east where borehole 91 NW 7, for example, TL 82, TL 92) and may coincide with an contains only 2 per cent gravel. A substantial extension in a north-easterly direction of the increase in the content of fines is recorded in buried channel known to exist beneath the the same direction, for example, in 91 NW 3 Blackwater Valley on 1:25 000 sheet TL 81 with 14 per cent fines and 91 NW 7 with 24 per (Haggard, 1972). cent although in NE 1 the fines account for only 5 per cent. The sand fraction is consistently In the remaining seven holes in this block between 60 and 70 per cent, except in 91 NE 1 the mineral ranged in thickness from 50 ft (15.2 where it rises to 90 per cent. m) in 91 NW 6 to 6 ft (1.8 m) in 91 NW 7 with a mean thickness of 33 ft (10.1 m) and the thick- The volume of mineral within the block,

8 assessed statistically, is 89.9 million m3 k 40 The volume of mineral in this block is per cent. All limits quoted in this report are estimated to be 3 5. 5 million m3 k 33 per cent. calculated at the 95 per cent confidence level. The total area over which terrace deposits Block B occur is approximately 1.2 km2; data from the Glacial Sand and Gravel constitutes almost adjacent 1:25 000 sheet (TL 80) suggests that all of the potentially workable deposits. It is, their mean thickness is likely to be approximately however, irregular in thickness, and has a 6 ft (1.8 m), so that the inferred estimate of patchy,discontinuous distribution. London Clay their total volume is about 2.1 million m3. is exposed around the margins of the Glacial Their mean grading to the west on sheet TL 80 Sand and Gravel deposits and in inliers within is fines 8 per cent, sand 32 per cent, gravel some of the more extensive sand and gravel 60 per cent (Ambrose, 1973) and in their outcrops, for example, west of Gorwell Hall continuation into the area here described their [944 1111. River deposits representing the grading may be similar. first and second terraces of the Rivers Chelmer and Blackwater are present near the northern LIST OF QUARRIES shores of theBlackwater Estuary. Although Known quarries at the time of the survey are they probably contain potentially workable sand listed in Table 3. and gravel, no statistical assessment has been made for them as they are of limited extent on Table 3. List of quarries in report area this sheet. They are a continuation of similar Grid Ref. deposits to the west where they are more Working extensive and have been assessed statistically RoundbushCorner 928193 (Ambrose, 1973). The terraces, the Glacial Sand and Gravel, and the London Clay are covered in Disused parts by Head of varying thickness and extent Hill Farm, Tolleshunt and by Alluvium along the shores of the estuary DIArcy 117 922 and in the larger river valleys. In estimating resources the positions of the boundaries of the References mineral beneath cover have been inferred. ALLEN, V. T, 1936. Terminology of medium- Nine Mineral Assessment Unit boreholes, grained sediments. Rep.. natn. Res. Coun. one well record, 241/ 56 (Davies and Standon Wash. 1935-36.- ADD.LA- 1. ReD.A- Comm. on Batt 1965), and commercial records have been sedimentation, pp. 18-47. used in the assessment of this block. Eight of AMBROSE, J.D. 1973. Thesand and gravel the M, A, U, boreholes proved potentially resources of the country around Maldon, workablesand and gravel. The exception is Essex: Description of 1: 25 000 res0urc.e 90 NW 2 where 25 ft (7.6 m) of silty and sandy sheetTL 80. Rep. No. 73/1., Inst.geol. clays rest directly on London Clay, suggesting Sci. 60 pp. that mineral is likely to be absent beneath - cover in the adjacent valley. The mineral ANON. 1948. Mineral Resources of the United thicknesses proved in the remaining boreholes States, pp. 14-17 (Washington D. C, : Public range from 6 ft (1.8 m) in 91 SW 2 to 24 ft Affairs Press). (7.3 m) in 91 SW 6, the mean thickness being 1967. Methods of testing soils for civil 115 ft (3.5, m). Overburden thicknesses in the engineeringpurposes. Stand. No. 1377, boreholes varied from 1 ft (0.3 m) of soil in z. 233 pp. 91 SW 6 to 15 ft (4.6 m) of clay and 'clayey' gravel in 91 SW 4. No trends in the variation 1970. Metrication: two opposing views. in thickness of either mineral or overburden can QuarryMgrs Jnl, Vol. 54, N-0. 6, p . 2-30 be distinguished in the boreholes over the block ARCHER, A. A. 1969. Backgroundand problems as a whole. of an assessment of sand and gravel resources in the United Kingdom. Proc. 9th Commonw. The mean grading of the mineral in this Min. metall.Conzr. 1969. Vol. 2. Minim and block is fines 7 per cent, sand 48 per cent, v u Petroleum Geology. Pp. 495- 508. gravel 45 per cent-figures which show that the proportion of gravel is far higher than in block 1970a. Standardisation of the A. However, the distribution of gravel appears size classification of naturally occurring to be irregular; in three holes (91 SW 1, 91 SW particles.Geotechnique, Vol. 20, pp. 103- 4 and 91 SW 5) the gravel content is between 27 107. and 34 per cent and in one (90 NW 1) it is as 1970b. Making the most of high as 62 per cent. In only one hole (91 SW 5) is the content of fines greater than 9 per cent.

9 ATTERBERG, A. 1905. Dierationelle Klassification der Sande und Kiese. Chem. -Z., Vol. 29, pp. 195-198. DAVIES, M,C,and STANDON-BATT, L. 1965. Records of Wells in the Area of New Series One-Inch (Geological) Epping (240), Chelmsford (241) and Brightlingsea (242) sheets.Water Supply Pap.Inst. geol. Sci., Well.Cat. Ser. HAGGARD, H, J.E, 1972. The sand and gravel resources of the country around Witham, Essex: Description of 1:25000 resource sheet TL 81 Rep. No. 72/ 6, Inst. geol. Sci. 99 pp. LANE, E, W, and others. 1947. Report of the sub-committee on sediment terminology Trans. Am. geophys.Un., Vol. 28, pp. 936-938. PETTIJOHN, F, J. 1957. SedimentaryRocks. 2nd Ed. (London: Harper and Row). THURRELL,R,G, 1971. Theassessment of mineral resources with particular reference

TWENHOFEL, W,H, 1937. Terminology of the fine-grainedmechanical sediments. Rep. natn.Res. Coun. Wash. 1936-7. App. 1, Rep.Comm. sedimentation, pp81-104. UDDEN, J. A,1914. Mechanicalcomposition of clastic sediments. Bull- geol. SOC. Am Vol. 25, pp. 655-7440 -' ' WENTWORTH, C,K, 1922. A scale of grade and class terms for clastic sediments. JnlGeol.,Vol. 30, pp.377-392. 1935.The terminology of coarse sediments. Bull. No.98 natn. Res. Coun. Wash., pp.225-246. WILLMAN, H, B, 1942.. Geologyand mineral resources of the Marseilles, Ottawa and Steatorquadrangle. Bull. Ill. State geol. -Surv., Vol. 66, pp.343-344.

10 Appendix A: Assessment Procedure evenly spaced sample points in the sampled area is n, with mineral thickness 1. Within a resourceblock, a statistical measurements 4, 12, . . . ln, then the assessment is made for a sampled area of bestestimate of meanthickness, = mineral greater than 2 km2 and containing - a minimum of five evenly-spaced boreholes + l2 . . . In) 2. If the sampled area of mineral is between n 0.25 and 2 km2 and contains one or two For groups of closely spaced boreholes a suitably sited boreholes an inferred discretionary weighting factor may be applied assessment is made. An inferred assess- to avoid bias (see note on weighting below). ment may also be attempted for any area The standard deviation for mean thickness, S- 1 where the deduced mineral content is small expressed as a proportion of the mean and which consequently has not been sampled thickness is given by by boreholes. No specificlevel of accuracy is claimed for such subjective assessments. 3. No assessment is attemptedfor an area value in the series 11to ln. of mineral less than 0.25 km2. 8. Thesampled area A ineach resource Statistical Assessment block is coloured pink on the map. Wherever 4. The simple methods used in the calculations possible, calculations relate to the mineral are consistent with the amount of data within mapped geological boundaries (which provided by thesurvey. Conventional may not necessarily correspond to the limits confidence limits (that is, the tolerance on of adeposit). Generally, therefore, the the estimate or the range within which the only error in determining the area is the result falls) are calculated at the two-sided negligible planimetering error and SA is 0. 95 per cent confidence level, that is, there Where the area is not defined by a mapped is a 24 per cent or 1 in 40 chance that the boundary, that is, where the boundary is result exceeds the stated upper limit and inferred (and the distinctive symbol is used), a corresponding 24 per cent chance that it is experience suggests that SA is small less than the stated lower limit. relative to Si. 5. The volume estimate (V) for the sampled The relationship mineral in a given block is the product of the two variables, the sa-mpled areas (A) and the mean thickness (1) calculated from - <- is assumed in all cases. 3 the individual thicknesses at the sample points.The standard deviations for these It follows from equation (2) that variables are related such that 1.05si... sV ......

9. Thetwo-sided 95 percent confidence where Sv, SA and Si are the standard limits, Lf, for the estimate of mean thickness deviations for volume, area and mean of mineral in the sampled area, for values of thickness,- expressed as proportions of n between 5 and 20, may be expressed in absolute units. V, A and 1, respectively. - - 6. The above relationship may be trans- 1 2 (t X Si X 1)s posed such that or -as a percentage 1 -+ (t xS,- x 100) per cent sV = s- + (-)I ...... (2) 1 i' where t is Student's t at the two-sided 95 per si cent confidence level for (n - 1) degrees of freedom and is evaluated by reference to From this it can be seen that as (-) tends S- statistical tables. In applyingStudent's t it 1 is assumed that the measurements are to 0, Sv tends to Sf. If, therefore,the distributed normally. standard deviation for area is small with respect to that for mean thickness, the 10. Values of t at the two-sided 95 per cent standard deviation for volume approximates confidence level for values of n up to 2 0 are to that for mean thickness. set out below: 7. Given that the number of approximately BLOCK CALCULATION

Block

Area Volume 2 Block: 11.08 km 2 Overburden: 21 million m 3 Mineral: 8.32 km Mineral: 38 million m 3 Thickness 95 per cent confidence limits of the estimate of mineral volume Overburden: 2.5 m Mineral: 4.5 m Percentage: 53 per cent Units of volume: 20 million m 3

Thickness estimate (1 = thickness) Measurements in metres

Sample \Peighting Overburden Mineral 1 Remarks point W lo wlo lm w lm

SE 14 1 1.5 1.5 5.2 SE 18 1 3.3 3.3 nil SE 20 nil 2.1 SE 22 0.7 0.7 9.3 MAU Boreholes SE 23 6.2 6.2 5.7 5.7 SE 24 4. 3 4.3 6.5 6.5 SE 17 1.6 3.9 123145 2.0 3.6 IIydrogeol. Dept. record 1 2.4 3.4 Close group 2 4.5 0. 8 2. 5(23):;: 3. 6(25)'::) of four 4 0.4 4.3 boreholes (commercial) 5 2.8 6.0 1

Totals Xxv = 8 xwlo = 20.l(25);;: xwlm = 36. 3(25);::

Averages lm = 4.5(41);:

Calculation of Confidence Limits

1 (1 - 1) (1 -

5.2 0.49 0.7 n=8 t = 2.365 nil 20.25 4.5 2.1 5.76 2.4 9.3 4.8 23.04 5.7 1.2 1.44 6.5 4.00 2.0 3.9 0.6 0. 36 3.6 0.9 0. 81 54.77

E1 = 36.3 (25) E(1 - 112 = 56.15 = 5570 n= 8 1 = 4. 5 (41) = 4.5

12 SE SE 22 18 0 n3.3 0.7 Nil 9.3

-I Km-

SE 17 123/45 0 5E 20 0 1.2 ) NII .2.0 4 2 21 3.6

SE 23 \ 2 \ 05 0 \ \ 40 6.2 \ 5.7 \ 60 \

\ I SE 24 I I / I / 0 / I 4.3 I I 6.5 1.5 I I 5.2 I I \ 1 \ I \ /

SCALE 1: 25 000

SE 17 0 M. A. U. borehole 0 Otherboreholes 1’2 - Overburden} Thicknessin metres 4.2 - Mineral

Boundary of resourceblock /- --- Boundary of sandand gravel deposit

Fig. 4. Example of resource block assessment: rpap of a fictitious block

13 n t n t n t may be present in such areas and an assessment is made on the basis of the 1 11 2.228 co average mineral thickness deduced from 2 12.7062.201 12 exposures and any other evidence available. 13 2.179 13 3 4.303 Note on Weighting 4 3.182 14 2.160 16. The thickness of a deposit at anypoint in a sampled area may be governed solely 5 2.7762.145 15 by the position of the point in relation to a 6 571 2. 2.131 16 broad trend. However, most sand and gravel deposits in addition exhibit a random pattern 1 7 2.120 17 7 2.447 of local, and sometimes considerable, 8 2.365 18 2.110 variation in thickness. 9 2.3062.101 19 17. Thus,in estimating mean thickness of sand and gravel from a number of data 10 2.262 20 2. 093 points in a sampled area only the use of (From Table 12, Biometrika Tables for simple weighting factors is justified, and Statisticians, Volume 1, Second Ed. the distribution of data points need be only Cambridge University Press, 19 62). approximatelyregular. In practice,equal weighting can often be applied to thicknesses The value of t, 1. 96, when n is infinity at all data points within the sampled area. is used when n is greater than 20. If, however, there is a distinctly unequal 11. In calculatingthe two-sided 95 per cent distribution of points, the thicknesses must confidence limits for volume, Lv, the be weighted to avoid the bias this creates. following inequality corresponding to (3) Weighting factors are determined by first is applied: dividing the sampled area into broad zones, to each of which a value roughly proportional to its area is assigned. This value is then shared between the data points within the zone. 12. Insummary, for values of nbetween 5 and 20, Lv is calculated as Appendix B: Classification and Description of Sand and Gravel

The terminology commonly used by geologists when and when n is greater than 20, as describing sedimentary rocks (Wentworth, 1922) is not entirely satisfactory for the purposes of this 1.05- x 1.96 x/n (n- -2 x 100 per cent Report. For example, Wentworth proposed that a de- 1 - 1) posit should be described as a ‘gravelly sand’ when the proportion of sand is greater thanthat of 13. An illustration of theprocedures out- gravel whichmust exceed10 per cent, fines and lined above is given in Figs. 3 and 4, oversize materials (that is, with diameter greater where a volume estimate with confidence than 64 mm) beingless than 10 per cent. Because limits at the 95 per cent level of deposits containing more than 10 per cent fines confidence is derived from Cictitious data. (material less than 1/16 mm) are not embraced by this system a modifiedbinary classification based Inferred Assessments on Willman (1942) has been adopted. 14. If the sampled area of mineral in a For the purposes of assessing resources of sand and gravel a classification should take account of resource block is between 0.25 km 2 and economically important characteristics of the de- 2 km2 an assessment is inferred based posit, in particular the absolutecontent of fines on geological and topographical information and the ratio of sand to gravel. usually supported by the data from one or When the fines content exceeds 40 per cent the two suitablysited boreholes. The volume material is considered tobe notpotentially work- of mineral is calculated as the product of able and falls outside the definition of mineral. the sampled area, chosen from interpretation Deposits whichcontain 40 per cent fines or less of field data as in the statistical assessment, are classified primarily on the ratio of sand to and the judged average mineral thickness. gravel and qualified in the light of the fines con- Confidence limits are not calculated. tent, as. follows: less than 10 per cent fines-no qualification; 10 per cent or more, but less than 15. In some cases inaddition to the sampled 20 per cent fines-‘clayey ’; 20 to 40 per cent area of mineral a resource block includes an fines-‘very clayey’. area left uncoloured on the map, generally The term‘clay’ (aswritten, with single quote based on interpretation of mapping and marks), isused todescribe allmaterial passing sampledata. On occasionssome mineral

14 1/16 mm. Thus it has no mineralogical significance words ‘and’ or ‘with’. For example, ‘flint and quartz’ and includes particles fallingwithin the size indicates very approximateequa€ proportions with limits of silt. Wherever the termclay does not neither constituentaccounting for less thanabout appear in single quotation marks the normal mean- 25 per cent of the whole; ‘flintwith quartz’ indi- ing applies. cates thatflint is dominant and quartz, the acces- The ratio of sand to gravel defines the boundaries soryrock type, comprises 5 to 25 per cent of the between Sand, Pebbly Sand, Sandy Gravel and Gravel whole.Where the accessory materialaccounts for (at 19:1, 3:l and1:l). less than5per cent of the whole, but is still Thusit is possible toclassify the mineral into readily apparent, the phrase ‘with some’has been one of twelve descriptive categories (see Fig 5). used. Rareconstituents are referred to as ‘trace’. The procedure is as follows. The termsused in the field to describe the de- 1.Classify according to ratio of sand to gravel. gree of rounding of particles-which is concerned 2. Describe fines. with the sharpness of the edges and corners of a For example, a deposit grading: gravel, 11 per cent; clastic fragment and not the shape-(after Pettijohn, sand, 70 per cent; fines, 19 per cent is classified 1957) are as follows. as ‘clayey’pebbly sand. This short description is Angular:showing little orno evidence of wear; included in the borehole log (seeNote 10, p. 18). sharp edges and corners. Many differing proposals exist for the classifi- Subangular:showing definite effects of wear. cation of the grain sizeof sediments (Atterberg, Fragments still have their original form but edges 1905; Udden, 1914; Wentworth, 1922; Wentworth, and corners begin to be rounded off. 1935; Allen, 1936; Twenhofel, 1937; Lane and others, Subrounded:showing considerable wear. The 1947). As Archer (1970a, b) has emphasised, there is edges and corners are rounded off to smooth curves. a pressing need for a simples metric scale accept- Original grain shape is still distinct. able to both scientific and engineering interests, Rounded: original faces almost completely des- for which the class limit sizes correspondclosely troyed, but somecomparatively flat surfaces may with certain marked changes in the natural proper- stillremain. All original edges and corners have ties of mineral particles. Forexample, there is an beensmoothed off to rather broadcurves. Original impcvtant change in the degree of cohesion between shape is still apparent. particles at about the 1/16 mm size, which approxi- Well-rounded: no original faces,edges or corners mates to the generally accepted boundary between left. The entire surface consists of broad curves; siltand sand. In this and other respects the sys- flat areas are absent. The originalshape is sug- tem shownin Table 4, used in thisreport, is gest6d by the present form of the grain. satisfactory. It is based on Udden’sgeometric scale and asimplified form of Wentworth’s termi- I I I I nology. Size limits The fairly wide intervals in the scale are con- Grain size 1 Qualification ClassificationPrimary description sistent with the general level of accuracy of the I I I t quantitative assessments of the resource blocks. Cobble Three sizesof sand are recognised, fine (-5 + 64 mm 1/16 mm),medium (- 1 + ?4 mm)and coarse (-4 + 1 mm). The boundary at 16 mm distinguishesa range of finer gravel (-16 + 4 mm), often charac- terised by abundance of worn tough pebbles of vein quartz, from coarser ranges often of notably dif- Coarse ferent average composition. The boundary at 64 mm 1 mm distinguishes pebbles from cobbles. The term ‘gravel’ is usedloosely todenote both pebble-sized and !4 mm cobble-sized material. The size distribution of boreholesamples is determined bysieve analysis, and is presented by the laboratory as logarithmiccumulative curves Fines Fines (silt and clay) (see, for example, British Standard 1377:67). In I I this report the grading is tabulated on the bore- hole record sheets (AppendixC), the intercepts Table 4. Classification of gravel, sand and fines corresponding with the simple geometric scale 1/16 mm, ?4 mm, 1 mm, 4 mm, 16 mm, and so on as required. Original sample grading curves are avail- able for reference at the appropriate office of the Institute. Eachbulk sample is described, subjectively, by a geologist at the borehole site. Beingbased on visual examination, the description of thegrading is inexact, the accuracy depending on the experience of the observer. The descriptions recorded are modi- fied, as necessary, when the laboratory results be- come available for inclusion in Appendix C. The relative proportions of the rock types present in the gravel fraction are indicated by use of the

15 ‘CLAY’ i.e. fines

SAN RAVEL I Sandygravel I sand’ 19.1 3:l 1 :1 Ratio

I , Gravel L II ‘Clayey’gravel

Ill ’Veryclayey ’ gravel

IV Sandygravel

V ’Clayey’sandy gravel

VI ’Veryclayey‘ sandy gravel

> MINERAL VI1 Pebblysand

Vlll ’Clayey‘pebbly sand

IX ‘Very,clayey‘ pebbly sand

X Sand

XI ’Clayey‘sand

x1 I ‘Veryclayey’ sand

(XIII) NON-MINERAL

Fig. 5. Diagram showing the descriptive categories used in the classification of sand and gravel

16 Appendix C: Borehole Records

EXPLANATION

Annotated Example of a Borehole Record

TL 91 NW1868'9039 2l Nr Harborough Hall3

Surface level (+ 49.4 m ) + 162 ft4 Overburden7 (6.4 m) 21 ft; Water struck at ( + 31.4 m) + 103 ft5 Mineral (14.0 m> 46 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft +' January 196g6

Thickness Depth" (m) ft (m) ft

B oulder Clayg Tops,oil andTops,oilClaygBoulder brown(6.4)clay" chalky 21 (6.4) 21 with chalk fragments up to 60 mm in diameter

GlacialGravel.'VerySandy Sand (14.0)clayey' top in 46 67(20.4) and Gravel 3 ft (0.9 ftGravel and 3 m). Gravellybetween 24 ft (7.3 m) and 33 ft (10.1 m), becoming sandy for 14 ft (4.3 m) to 47 ft (14.3 m); gravel content gradually increases below 47 ft (14.3 m) Gravel; fine to coarse, subrounded to subangular flints, with fine subrounded quartz and flints Sand; reddish brown to pale brown subangular; fine to medium in top 3 ft (0.9 m) becoming medium below; mainly fine between 36 ft (11.0 m) and 41 ft (12.5 m)

Londo n Clay Weathered ClayLondon brown clay (0.9 t) 3 + (21.3) 70

Depth below" percentage^'^ % mm ?& surface (ft) Fines GravelSand G ravel" 34Gravel" t 16 14 21 - 24 62 25 13 - 16 +20 4 24 - 27 0 46 54 27 - 30 0 40 60 Sand 64 Sand - 4+1 6 30 - 33 53 1 46 - 1+% 39 33 - 36 0 83 17 - j/, +X6 19 36 - 39 8 0 92 39 - 41 6 0 94 Fines 2 - %6 2 41 - 4423 76 1 3 44 - 47 0 82 18 47 - 50 0 68 32 (50 - 53 No grading a~ailable)'~ 53 - 56 57 1 42 56 - 59 73 2 25 59 - 62 0 59 41 62 - 65 2 32 66 65 - 67 520 48

The numbered paragraphs below correspond withthe identified by a Registration Number.This consists of annotations given on the specimen record above. two statements. 1) The number of the 1 : 25 000 sheet on which 1. Borehole Registration Number. the borehole lies, for example, TL 91. EachMineral Assessment Unit(MAU) borehole is 2) Thequarter of- the 1 : 25 000 sheet on which

17 the borehole lies and its number in a series 11. Depth. for that quarter, for example, SE 5. The figures relate to depths from surface tobase Thus the full Registration Number is TL 91 SE 5. of the strata recorded on the log. Usually this is abbreviated to 91 SE 5 in the text. Grading information 2. The National Grid Reference. 12. Sampling. All NationalGrid References in this publication A continuous series of bulk samplestakenis lie within, the 100 km square TL unless otherwise throughout the thickness of sand and gravel. A new stated. Grid references are given to eight figures, sample is commenced whenever there is an appreci- accurate to within 10 m, for borehole locations. able lithological change within the sand and gravel, (In the text, six-figure grid references are used or for every 3 ft of depth. for more approximate locations, for example, for farms). 13. Grading Results. The limits are as follows: gravel, +4 mm; sand, 3. Location. -4+1/16 mm; fines, -1/16 mm. The borehole location is generally referredto the nearest named locality on the 1 : 25 000 base map. 14. Exceptionally the results of the grading of a sample or horizon may not be available. No attempt 4. Surface Level. hasbeen made to estimate the probable grading of The surface level at the borehole site is given in such samples, and the grading diagram may not be metres and feet above Ordnance Datum. All measure- shown on the map. mentswere made in feet; approximate conversions to metres are given in brackets. 15.Mean Grading. The mean grading for the mineral thickness is the 5. GroundwaterConditions. mean of the individual sample gradings, but where Three kinds of entry are made; either, the level the thicknesses of mineral represented by the sam- at which groundwater was encountered is given in ples are notconstant each grading result is first metres and feet above Ordnance Datum; or, where no weighted by its relative thickness. groundwater wasencountered, this is stated; or, The results are given for the three main classes, where there is no record of the groundwater condi- gravel, sand and fines, and for the smaller tions, this is stated. ranges within these classes. Since fully representative sampling of sand and 6. Type of Drill and Date of Drilling. gravel is difficult to achieve, particularly where Two types of drillingmachine havebeen used in groundwaterlevels are high, there maybe diffe- this survey; aShell and Auger rigand aWirth rencesbetween the gradings determined during the (a casedpower auger). The type of machine,the survey and the correspondingin-situ grading of external diameter of the casing used, and the month the deposit. Comparisonwith exposures - suggests and year of completion of the borehole are stated. that the proportion of sand in the samples collected from boreholes may be somewhat higher. Conversely 7. Overburden, Mineral, Waste and Bedrock. the results suggest that the proportion of fines Mineralis sand and gravel which,as part of a and of + 16 mm material may be lower. deposit, falls within the arbitrarydefinition of potentially workable material (see p.1). Note on metrication Bedrockis the formation, rocktype, country 1) All measurements were made in feet. Approxi- rock or rock-head, below which potentially workable mate metric conversions appearin brackets. sand and gravel will not be found. In the Norwich 2) Metric conversions of measurements of the area the bedrock is Chalk. depth and thickness of beds have been rounded Waste is any material otherthan bedrock or off to the nearest 0.1 m,because quotation totwo mineral. Wherewaste occurs between the surface places of decimals wouldimply a higher order of and a mineral horizon it is classified as overburden. accuracy thancould be justified by the original Thicknesses are given in metres and feet. figures. To eliminateany discrepancy appearing after metrication between depth as recorded and 8. Theplus sign (+) indicates that the base of depth as obtained by summing thicknesses, adjust- the deposit was not reached during drilling. ment has been made where necessary to one or more of the thickness figures. However, the recorded The borehole log mineral thickness is not adjusted. 9. Geological Classification. A geological classification of the strataencoun- tered indrilling is givenwhenever possible. (For an explanation of the terms used see p. 4).

10. Lithological Description. Whensand and gravel is recorded, a general des- cription based on the mean grading characteristics is followedis by more detailed particulars.(For explanation of conventions see Appendix B). A description of other rocktypes is based on visual field examination.

18 LIST OF MINERAL ASSESSMENT UNIT BOREHOLES

Borehole Grid reference No. (all fall in 100 km (by sheet square TL ) quadrants )

TL 91NW 1 90131968 2 90391868 3 90841769 4 91211965 5 91571881 6 93081923 7 94851877

TL 91NE 1 96581934

TL 91 SW 1 90211127 2 91211035 3 92421230 4 92641141 5 94331171 6 94841047

TL 90 NW 1' 91620925 2 93590949

TL 90NE 5 96190971

19 THE RECORDS

TL 91 NW 1 Messing19689013Lodge

Surface level ( t 35.4 m) t 116 ft Overburden (7.5 m) 24% ft; Water struck at ( + 27.9 m) t 91% ft Mineral (13.2 m) 43% ft; Shell and Auger, 6 inch diam., Bedrock (0.9 m + ) 3 ft + February 1969

Thickness Depth (m) ft (m) ft

BoulderClay Soil, made ground and firm brown (7.5) 24% 24% (7.5) chalky clay to 10 ft (3.0 m), becoming greyish blue, occasionally silty between 10 ft (3.0 m) and 20 ft (6.1 m) and with a compact silt with traces of peat from 14 ft (4.3 m) to 15 ft 6 in (4.7 m). Becoming brown and stony below 20 ft (6.1 m) with a 6 in (0.2 m) lens of clayey sand and gravel at 22 ft (6.7 m) and a 6 in (0.2 m) grey siltstone at 23 ft (7.0 m)

Glacial Sand Sandy Gravel.Pebbly sandtopin 24 ft (13.2) 43% (20.7) 68 andGravel (7.3 m). Increasegravelin content below this at the expense of the sand. Gravel: fine to coarse, subangular to subrounded flints and quartz; large coarse flints, some approaching cobble-size below 63 ft (19.2 m) Sand: brown and reddish brown sub- angular quartz; medium with fine down to 48 ft (14.6 m); mainly medium below with a medium to coarse zone between 51 ft (15.5 m) and 54 ft (16.5 m)

London ClayStiff, siltyclay; brown for 1 ft (0.3 m) at (0.9 +) 3 + (21.6) 71 the top, blue below

Depth below Percentage % mm % surface (ft) Fines Sand Gravel Gravel 29 t 16 15 24% - 27 2 77 21 - 16 +4 14 27 - 30 2 88 10 30 - 33 2 92 6 Sand 70 - 4+1 8 33 - 36 0 93 7 - I+% 44 36 - 39 2 92 6 - %+x6 18 39 - 42 1 86 13 42 - 45 2 92 6 Fines 1 - X6 1 45 - 48 2 93 5 48 - 51 2 48 50 51 - 54 0 55 45 54 - 57 2 62 36 57 - 60 2 52 46 60 - 63 0 52 48 63 - 66 0 32 68 66 - 68 2 26 72

20 TL 91 NW90391868 2 Nr Harborough Hall

Surface level ( t 49.4 m) + 162 ft Overburden (6.4 m) 21 ft; Water struck at ( + 31.4 m) + 103 ft Mineral (14.0 m) 46 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m t ) 3 ft t January 1969

Thickness Depth (m) ft (m) ft

BoulderClay Topsoiland brown chalkyclay (6.4)with 21 (6.4) 21 chalk fragments up to 60 mm in diameter.

GlacialGravel.'VerySandy Sand top clayey'in (14.0) 46 67 (20.4) andGravel 3 ft (0.9 m). Gravellybetween ft24 (7.3 m) and 33 ft (10.1 m), becoming sandy for 14 ft (4.3 m) to 47 ft (14.3 m), gravel content gradually increases below 47 ft (14.3 m) Gravel: fine to coarse, subrounded to subangular flints, with fine sub- rounded quartz and flints Sand: reddish brown to pale brown subangular; fine to medium in top 3 ft (0.9 m) becoming medium below; mainly fine between 36 ft (1 1.0 m) and 41 ft (12.5 m)

LondonClayWeathered brown clay (0.9 t) 3 t 70(21.3)

Depth below Percentage % mm % surface (ft) Fines Sand Gravel Gravel 34Gravel 14 t 16 21 - 24 25 62 13 - 16 t20 4 24 - 27 0 46 54 27 - 30 0 40 60 S and 64 Sand - 4t1 6 30 - 33 1 53 46 - lt% 39 33 - 36 0 83 17 - %+X6 19 36 - 39 0 92 8 39 - 41 0 94 6 Fines 2 - %6 2 41 - 44 1 76 23 44 - 47 0 82 18 47 - 50 0 68 32 (50 - 53 N o grading available) 53 - 5657 1 42 2 73 25 56 - 5973 2 59 - 62 41 0 59 62 - 65 2 32 66 65 - 67 0 48 52

21 .TL 91 NW 3 17699084 HaynesGreen

Surface level ( t 52.4 m) + 172 ft Overburden (1.5 m) 5 ft; Water struck at ( t 49.1 m) t 161 ft Mineral (8.9 m) 29 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m t ) 3 ft + February 1969

Thickness Depth (d ft (m) ft

Glacial Sand Soil and brown clay (1.5) 5 (1.5) 5 and Gravel

‘Clayey’Pebbly Sand. Thetop (8.9) 29 34 (10.4) 14 ft (4.3 m) is ‘very clayey’; considerable reduction in fines content below. Gravel more important towards the bottom of the deposit Sand: rust brown becoming grey to greyish brown; fine or fine to medium in top 14 ft (4.3 m) with medium sand dominant below Gravel: fine to coarse subangular to subrounded flints and quartz

London Clay Weathered brown clay (0.9 t) 3 + (11.3) 37

Depth below Percentages % mm % surface (ft) Fines Sand Gravel G ravel 18Gravel t 16 9 5- 8 28 64 8 -16+4 9 8 - 11 26 61 13 11 - 14 35 61 4 Sand 68 - 4+1 5 14 - 19 23 62 15 - l+% 37 19 - 22 9 73 18 - % + 26 22 - 25 28 2 70 25 - 28 0 92 8 Fines i4 - %6 14 28 - 31 1 64 35 31 - 34 4 59 37

TL 91 NW 4 9121 1965 DisusedAirfield, Birch

Surface level ( + 43.3 m) + 142 ft Waste (18.3 m + ) 60 ft + Water struck at ( + 32.0 m) + 105 ft Wirth B 0, 8 inch diam., January 1969

Thickness Depth (m) ft (m) ft

BoulderClay Soil and brown chalkyclay, (18.3 t) 60 t (18.3) 60 becoming grey below 23 ft (7.0 m)

22 TL 91 NWBirchHolt18819157 5

Surface level ( t 45.4 m) + 149 ft Overburden (14.6 m) 48 ft; Water struck at ( + 26.2 m) + 86 ft Mineral (7.3 m) 24 ft; Wirth B 0,8 inch diam., Bedrock (1.0 m + ) 3 ft + January 1969

Thickness Depth (m) ft (4 ft

Boulder Clay Soil and brown becomingchalkyclay, (1 48 4.6) (14.6) 48 grey below 20 ft (6.1 m) and containing occasional silty bands and gravel bands

Glacial Sand Sandy Gravel.Proportion 72 of (21.9)gravel 24 (7.3) and Gravelincreasing through thetop 9 ft (2.7 m) below this the sand content increases accompanied by decrease in gravel content. Fines content high in the top 3 ft (0.9 m) Gravel: fine to coarse subangular to subrounded flints and quartz, with fine quartzites Sand: brown; subangular, mainly medium, with varying, usually subsidiary, amounts of fine and coarse

London Clay Weathered, brown clay (1.0 t) 3 t 75(22.9)

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel 28 + 16 12 48 - 51 21 57 22 - 16 44 16 51 - 54 2 57 41 54 - 57 0 46 54 Sand 65 - 4t1 10 57 - 60 0 65 35 - l+% 39 60 - 63 3 79 18 - %+X6 16 63 - 66 12 71 17 66 - 69 7 71 22 Fines 7 - %6 7 69 - 72 10 75 15

23 TL 91 NW 6 93081923 Nr RoundbushCorner

Surface level ( t 35.4 m) t 116 ft Overburden (4.0 m ) 13 ft; Water struck at ( + 26.8 m ) + 88 ft Mineral (15.2 m) 50 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft t July 1969

Thickness Depth (d ft (d ft

? Head Soil and brown clay (4.0) 13 (4.0) 13 ,. Glacial Sand SandyGravel. Gravel content high (19.2)(15.2) 50 63 andGravel at thetop;diminishes with increasing depth, becoming irregularly distributed below 30 ft (9.1 m) Gravel: fine to coarse rounded, sub- rounded and subangular flints, quartzites and some quartz; coarsest in the top 3 ft (0.9 m) Sand: greyish brown to rust brown; mostly medium or fine to medium.

LondonClayWeathered, brown clay (0.9 t) 3 t (20.1) 66

Depth below Percentages % mm % surface (ft) Fines Sand Gravel G ravel 30Gravel 15 t 16 -16+4 15 13 - 16 0 18 82 16 - 19 0 28 72 Sand 69 Sand - 44-1 7 19 - 22 2 45 53 - 1t% 50 22 - 25 1 76 23 - % +xs 12 25 - 28 0 68 32 28 - 31 2 89 9 Fines 1 - x6 1 31 - 34 1 99 0 34 - 37 2 98 0 37 - 40 0 94 6 40 - 43 2 68 30 43 - 46 2 90 8 46 - 49 2 60 38 -’ 49 - 52 2 44 34 52 - 55 0 96 4 55 - 58 2 84 14 58 - 61 0 70 30 61 - 63 1 45 54

24 TL 91 NW9485 7 1877 Layer Breton Heath

Surface level ( t 50.9 m) + 167 ft Overburden (4.3 m) 14 ft; Water struck at ( + 46.3 m) f 152 ft Mineral (1.8 m) 6 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m t ) 3 ft t July 1969

Thickness Depth (d ft (d ft

Head Soil and brown clay giving way to (4.3) 14 (4.3) 14 grey silty clay at 8 ft (2.4 m)

Glacial Sand ‘Very clayey’ Sand. Traces of chalk and Gravel pellets in top 3 ft (0.9 m) Sand: bluish grey, mostly fine with some medium Gravel: Traces only, fine to coarse, rounded to subrounded, flints and quartz

London Clay Weathered, brown clay (0.9 t ) 3 t (7.0) 28

Depth below Percentages % mm % surface (ft) Fines GravelSand G ravel 2 Gravel + 16 1 3 14 - 1778 19 -16+4 1 17 - 20 2 29 69

Sand 74 - 4+1 3 - I+% 26 - % + 45

Fines 24 - X6 24

25 TL 91 1934NE9658 1 Wick Farm

Surface level ( + 41.5 m) + 136 ft Overburden (1.8 m) 6 ft; Water struck at ( -+ 35.1 m) + 115 ft Mineral (10.1 m) 33 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft f February 1969

Thickness Depth (m) ft (m) ft

? Head and Soil brown clay (1.8) 6 (1.8) 6

Glacial Sand PebblySand. Traces only of gravel(10.1) 33 (11.9) 39 and Gravel except for 12 ft (3.7 m) of ‘pebbly sand’ between 15 ft (4.6 m) and 27 ft (8.2 m) ‘Clayey’ bands present between 21 fi (6.4 m) and 24 ft (7.3 m) and for 3 ft (0.9 m) at the bottom of the deposit Sand: fine to medium, subangular, rust brown in top 6 ft (1.8 m);mainly medium, grey to 24 ft (7.3 m); becoming fine to medium, greyish brown below Gravel: fine to coarse subrounded flints and quartz

London Clay Brown, weatheredclay (0.9 + ) 3 f 42 (12.8)

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel 5 Gravel 3 + 16 6- 9 0 100 0 -16+4 2 9 - 12 0 97 3 12 - 15 2 96 2 Sand 90 Sand - 4+1 4 15 - 18 0 92 8 - 1+% 47 18 - 21 2 87 11 - Y4 + X6 39 15 21 - 2468 17 24 - 27 0 94 6 Fines 5 - X, 5 27 - 30 0 100 0 30 - 33 9 88 3 3 94 3 33 - 3694 3 36 - 39 17 80 3

26 TL 91 SW90211127 1 Gate Farm, Tolleshunt Major

Surface level ( + 28.0 m) f 92 ft Overburden (2.4 m) 8 ft; Water struck at ( + 21.0 m) f 69 ft Mineral (5.2 m) 17 ft; Wirth B 0,8 inch diam., Bedrock (0.9 m f ) 3 ft f July 1969

Thickness Depth (d ft (m) ft

? Head Soil and brown clay 8 (2.4) 8 (2.4)

GlacialSandy Sand Gravel. 'Clayey'between 17band(5.2) (7.6) 25 andGravel (4.3ft14 m) and17 ft (5.2 m) Gravel: Mostly fine;subangular to subrounded flints and quartz Sand: brown to greyish brown predominantly medium

London clay,BlueClayweathered brown for a few (0.9 f ) 3 f 28(8.5) inches below the surface

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel34 f 16 12 8 - 11 0 70 30 - 16 + 4 22 11 - 14 1 47 52 14 - 17 12 65 23 San d 63Sand - 4tl 8 17 - 20 1 69 30 - l+% 50 20 - 23 2 57 41 - %+X6 5 23 - 25 0 72 28

Fines 3 - X6 3

27 TL 91 SW9121 2 1035 Manor Farm, Tolleshunt Major

Surface level ( f 14.6 m) f 48 ft Overburden (0.6 m) 2 ft;

Water struck at ( f 12.8 m) + 42 ft Mineral (1.8 m) 6 ft; Wirth B 0,8 inch diam., Waste (3.4 m) 11 ft; February 1969 Bedrock (0.9 m + ) 3 ft f

Thickness Depth (4 ft (m) ft

Made ground and subsoil

G ravel (1.8) 6 (2.4) 8 (2.4) 6 Glacial(1.8) Sand Gravel and Gravel Gravel: fine to coarse becoming coarser downwards; mostly sub- angular flints with rounded to subrounded quartz Sand: medium; subrounded to subangular

? London(3.4) Clay clay Brown silty 11 (5.8) 19

London Clay (0.9Brown clay f ) 3.t (6.7) 22

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel 48 + 16 Z3 , 2-5 6 52 42 -16+4 25 5-8 8 38 54

Sand 45 - 4+1 8 - 1+% 32 - %+Xb 5

Fines 7 - %b 7

28 TL 91 SW9242 3 1230 Grout’s Farm, Tolleshunt D’Arcy

Surface level ( + 29.0 m) + 95 ft Overburden (1.8 m) 6 ft; Water struck at ( + 25.6 m) f 84 ft Mineral (4.9 m) 16 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft + February 1969

Thickness Depth (m) ft brm> ft

Head Soil and brownclay silty (1.8) 6 (1.8) 6

Glacial Sand Gravel.‘Clayey’ inthe top ft 4 (1.2 m), (4.9) 16 (6.7) 22 and Gravel the fines content decreasing below. Most gravelly in the bottom 6 ft (1.8 m) of the deposit Gravel: subangular to subrounded flints, quartzites and quartz; mostly fine in the top half of the deposit, becoming coarser downwards. Sand: greyish brown to brown; mainly medium

London Clay Brown, weathered clay (0.9 t) 3t (7.6) 25

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel 53 t 16 24 6- 8 16 42 42 - 16 + 4 29 8 - 10 11 39 50 10 - 13 9 39 52 Sand 38 - 4+1 7 13 - 16 10 53 37 - 1+% 26 16 - 19 3 29 68 - %+X6 5 19 - 22 4 28 68

Fines 9 - %6 9

29 TL 91 SW9264 1141 4 Wild FowlFarm, Tolleshunt D’Arcy

Surface level ( t 26.8 m) t 88 ft Overburden (4.6 m) 15 ft; Water struck at ( t 24.4 m) + 80 ft Mineral (3.6 m) 12 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft + July 1969

Thickness Depth (m) ft (m) ft

? Head and Soil brown clay (4.0) 13 (4.0) 13

‘V ery clayey’ gravel (0.6) 2 (0.6)Glacial gravel Sand clayey’ ‘Very 15 (4.6) and Gravel SandyGravel.‘Clayey’ the in 12(3.6)top (8.2) 27 3 ft (0.9 m). Very sandy between 18 ft (5.5 m) and 21 ft (6.4 m) Gravel: fine to coarse; mostly coarse in the top 3 ft (0.9 m), and mostly fine below; subangular to subrounded flints Sand: rust brown; fine with medium in the top 3 ft (0.9 m),mainly medium below

London Clay Blueclay,weathered brown in parts. (0.9 + ) 3 + (9.1) 30

D epth belowDepth Percentages 96 mm % surface (ft) Fines Sand Gravel Gravel 27 + 16 10 15 - 18 16 41 43 -16 +4 17 18 - 21 4 86 10 21 - 24 1 64 35 Sand 66 - 4+1 10 24 - 27 7 71 22 - 1+’/4 36 - % + x, 20 Fines 7 - x, 7

30 TL 91 SW9433 5 1171 Guisnes Court, Tollesbury

Surface level ( + 25.3 m) + 83 ft Overburden (0.9 m) 3 ft; Water struck at ( + 21.3 m) + 70 ft Mineral (2.5 m) 8 ft; Wirth B 0, 8 inch diam., Waste (3.6 m) 12 ft; February 1969 Bedrock (0.9 m f ) 3 ft +

Thickness Depth (m) ft (m) ft

Soil 3 (0.9) 3 (0.9)

Glacial Sand ‘Very Clayey’ Sandy Gravel. ‘Very (2.5) 8 11 (3.4) and Gravel clayey’ below the top 2 ft (0.6 m). Gravel: mostly fine; subangular to subrounded flints, quartzites and quartz Sand: greyish brown; medium to coarse in the top 2 ft (0.6 m), medium below

? London Clay Brown, silty clay (7.0)(3.6) 12 23

London Clay Brown, weathered clay (0.9 +) 3+ (7.9) 26

Depth below Percentages % mm % surface (ft) Fines Sand Gravel Gravel 27 f 16 9 3- 5 10 57 33 - 16 +18 4 5- 8 31 48 21 8 - 11 30 44 26 Sand 49 - 4+1 15 - 1+% 32 - %+g6 2

Fines 24 - %, 24

31 TL 91 SW94841047 6 Nr Garland’s Farm, Tollesbury

Surface level ( f 24.1 m) f 79 ft Overburden (0.3 m) 1 ft;

Water struck at ( f 22.6 m) f 74 ft Mineral (7.3 m) 24 ft; Wirth B 0,8 inch diam., Bedrock (0.9 m f ) 3 ft f February 1969

Thickness Depth (m) ft (4 ft

Soil (0.3) 1 (0.3) 1

Glacial Gravel.Sand Verytop sandy in 3 ft (0.9 m) 25(7.6) 24(7.3) and GravelGravel:and coarse;andsubangular fine flints and subordinate subrounded quartz Sand: brown, medium, subangular

London Clay Brown, clayweathered (0.9 f) 3 f (8.5) 28

Depth below Percentages ??I mm ??I surface (ft) Fines Sand Gravel Gravel 52 + 16 24 1- 4 9 60 31 - 16 +4 28 4- 7 8 39 53 7 - 16 7 38 55 Sand 41 - 44-1 7 16 - 19 5 35 60 - 1+% 29 19 - 22 6 36 58 - %fl& 5 22 - 25 6 47 47

Fines 7 - %6 7

32 T L 90TL NW91620925 1 Longwick Farm, Tolleshunt Major.

Surface level ( + 11.O m) + 36 ft Overburden (1.2 m) 4 ft; Ground water conditions not recorded Mineral (3.1 m) 10 ft; Wirth €3 0, 8 inch diam., Bedrock (0.9 m i- ) 3 ft t February 1969

Thickness Depth (m) ft (m) ft

Head 4 (1.2) and 4 Soil (1.2) gravel clay with

Glacial Sand BecomesGravel. increasinglysandy 10 (3.1) (4.3) 14 and Gravel and less gravelly with depth Gravel: fine to coarse down to 10 ft (3.0 m), mainly fine below; subangular flints and subrounded and rounded quartz and quartzites Sand: brown, mainly medium with coarse and a trace of fine; sub- angular to subrounded

London Clay Brown clay (0.9 + ) 3 i- 17(5.2)

D epth belowDepth Percentages % mm % surface (ft) Fines Sand Gravel Gravel 62Gravel 29 + 16 4- 7 0 30 70 - 16+4 33 7 - 10 7 31 62 10 - 13 0 44 56 Sand 36 - 4+1 9 13 - 14 0 47 53 - l+M 24 - %+X6 3

Fines 2 - X6 2

T L 90TL NW93590949 2 The Wycke, Tolleshunt D’Arcy

Surface level ( i- 10.1 m) + 33 ft Waste (7.6 m) 25 ft; Water not struck Bedrock (0.9 m + ) 3 ft + Wirth B 0, 8 inch diam., February 1969

Thickness Depth (m) ft (m) ft

Head Soil and silty clay 9 (2.7) 9 (2.7)

? London Clay Brown sandy clay (4.9) 16

London Clay Brown clay (0.9 +) 3 + (8.5) 28

33 TL 90TL NE96190971 5 nr Me11 House, Tollesbury

Surface level ( + 18.0 m) + 59 ft Overburden (2.4 m) 8 ft; Water struck at ( + 15.8 m) + 52 ft Mineral (3.7 m) 12 ft; Wirth B 0, 8 inch diam., Bedrock (0.9 m + ) 3 ft + February 1969

Thickness Depth (m) ft (m) ft

Glacial Sand Soil and brown clay with gravel 8 (2.4) 8 (2.4) and Gravel

Gravel. ‘Clayey’ in top 3 ft (0.9 ni); 12 (3.7) (6.1) 20 Gravel: fine and coarse, mainly rounded to subrounded quartzites with occasional subrounded to subangular flints, and rounded to subrounded quartz becoming common below 17 ft (5.2 m) Sand: brown; mainly medium, sub- angular and subrounded down to 17 ft (5.2 m); mostly fine to medium below

London C1 ay Brown clay (0.9 + ) 3 t 23(7.0)

Depth below Percentages % mm % surface (ft) Fines GravelSand Gravel55 + 16 28 8 - 11 12 35 53 -16+4 27 11 - 14 0 43 57 14 - 17 7 40 53 Sand 40 - 4+1 10 17 - 20 0 42 58 - 1+M 21 - 9

Fines 5 - %6 5

Dd. 505913 K16

Printed in England for Her Majesty’s Stationery Office by Unwin Brothers Llmited, The Gresham Press, Old Woking, Surrey

34