Hampshire Basin Research Articles

THE MODIFICATION AND APPLICATION OF THE QUANTITATIVE X‐RAY DIFFRACTION METHOD OF SCHULTZ (1964) TO THE MINERALOGICAL STUDY OF LONDON CLAY SAMPLES

SummaryOver 300 samples of London Clay from twenty‐one widely scattered sample locations in the London and Hampshire Basins were to be examined in detail by X‐ray diffraction techniques. The quantitative method of Schultz (1964) was chosen as being most suited for the analysis of the samples. Series of tests designed to investigate the reproducibility characteristics of the method were conducted. These showed that the sampling, sample preparation, and interpretation procedures used all introduced cumulative reproducibility errors of roughly equal magnitude which completely overshadowed errors introduced by machine‐response variation. It was also established that minerals whose contents were below 10 percent of whole sample failed to be consistently quantitatively estimated.The accuracy of this method of analysis depended heavily on Schultz's quoted ‘intensity factors’ which were involved in the calculation of individual mineral contents. The authenticity of these factors with regard to the London Clay suite of minerals was checked by comparing accurately determined mineral percentages of six standard London Clay samples with the results obtained by use of the Schultz procedure and factors. The method was found to be basically sound although the intensity factors for quartz, total clay minerals, carbonates, and illite had all to be slightly adjusted. The accurate quartz percentages were established by three different X‐ray diffraction techniques and the carbonate percentage checks were accomplished by specially designed wet chemical methods. The total clay mineral and illite contents checks were carried out by back‐calculation of the Al2O3, and K2O percentages as determined from full wet chemical analysis. Using the adjusted factors, quartz percentages are estimated accurate to ±6 percent, total clay minerals to ±7 percent, carbonate percentages to ±1.5 percent, and illite contents to ±4 percent of the whole rock.

A temporary exposure of Fossiliferous London Clay (Eocene) at Shinfield, Berkshire

A temporary exposure of Eocene London Clay in the M4 motorway cutting at Shinfield, Berkshire, is described and the contained rich biota listed and discussed. The London Clay here is divided by the authors into seven local units, each being distinguished by particular, dominant elements of the macrofauna. The London Clay formerly exposed in the cutting is assigned to Wrigley's Divisions 3 and 4 of the London Clay in the London area. Its biota shows affinities to that of the Hampshire Basin London Clay.

Engineering Group of the Geological Society 1971–72

5 October 1971 at 5.00 p.m. A geotechnical map of the London Clay in the London and Hampshire Basins (Lecture with demonstration.) By A. D. Burnett. Aspects of the study had been to establish mineralogical and sedimentological variations within the deposits and to relate them to a recently published palaeontological zonation of London clay. The regional structure and aspects of the deposits were presented as elevation contours, isopachyte and zone maps. This work was linked with a preliminary correlation by computer studies on the variation of engineering properties and presented as trend surface maps. These engineering properties were obtained from published work, site investigation data made available by numerous firms and by individuals, and from work carried out specifically for the study. The whole rock and clay mineral distributions from several hundred analyses were illustrated by means of depth profiles, contour maps, ribbon diagrams and computer trend surfaces. Changes in the mineralogy and sedimentological conditions and in regional engineering properties were given and their influence and effect discussed. Maps and sections from the London and Hampshire Basins were displayed. 11 November 1971 at 5.15 p.m. Engineering aspects of glacial features in Britain (Lecture). By I. E. Higginbottom, P. G. Fookes, D. L. Gordon. The occurrence and classification of British glacial deposits was reviewed. Their engineering properties and typical problems of design and construction were summarized and illustrated with case histories. Much of the lecture was devoted to the planning of site investigations in glaciated areas and the problem of adequately

The regional setting

For the purpose of the present discussion, southeastern England will be understood to embrace East Anglia, the London Basin, the Weald anticline and the Hampshire Basin. However, because of the immediate practical importance of subsidence still apparently continuing, it will focus most attention upon the Thames Estuary and on London. The whole region is one in which the formations exposed at the surface are no older than Jurassic (about 160 million years (Ma)). They continue upwards through Cretaceous (Gault, Greensand, Chalk) and Tertiary to Pleistocene and Recent deposits. The Mesozoic rocks rest upon a platform of much older rocks, ranging from Carboniferous (under Kent) through Devonian under London itself to lower Palaeozoic. Figure 1 shows the formations penetrated by representative boreholes through the Mesozoic cover. The platform of Devonian lies 300 m or less below surface under London (Sherlock 1962), but the upper boundary of the ancient rock descends to 1500 m or more under the Weald (Gallois 1965). Not enough information is available to enable the thickness and structure of these old buried rocks to be worked out, but it is certain that they had been extensively folded by disturbances that culminated at perhaps 390—420 Ma (‘Caledonian’) and 280 Ma (‘Hercynian’). For long periods of geological time, what is now the infrastructure of southeastern England formed part of a great mobile belt extending, according to current ideas, longitudinally across a continental mass which included Eurasia and America.

Proceedings

20–23 September 1971 Engineering Group Regional Meeting, University of Leeds Engineering Geology: route planning, design and construction 15 October 1971 Engineering Group A geotechnical map of the London Clay in the London and Hampshire Basins (Lecture with demonstration) A. D. Burnett 20 October 1971 Ordinary General Meeting (arranged by Marine Studies Group) The stratigraphic results of the J OIDES deep-sea drilling project 1. The palaeomagnetism of marine sediments. N. D. Opdyke, Columbia University, New YorkDuring the last five years great strides have been made in the application of magnetic stratigraphy to problems of correlation within ocean sediments. The magnetic time-scale of the last 4 m.y. of earth history was reviewed giving particular emphasis to magnetic events which occur within the Brunhes, Matuyama and Gilbert magnetic epochs.The magnetic stratigraphy has recently been extended to sediments of upper middle Miocene age (magnetic epoch 15) through the use of long cores and overlapping sections. The utility and reliability of this extension of the magnetic time scale was discussed.Preliminary palaeomagnetic measurements have been made on marine sediments from the first four legs of the Deep Sea Drilling Project. The problems involved with palaeomagnetic studies on cores obtained by rotary drilling in deep water were considered and the results to date assessed.Although the principal use to which palaeomagnetic studies of sediments have been put has been stratigraphic, it should also be possible to use this information to help resolve tectonic problems, particularly when crustal plates have been moved for large distances

The recognition of a planktonic foraminiferid datum in the London Clay of the Hampshire Basin

A datum, marked by the first appearance of plaktonic species, is described from the London Clay of Whitecliff Bay and Alum Bay, Isle of Wight. Its value in the correlation of Lower Eocene sections in the Hampshire Basin is discussed.

Stratigraphy and correlation of the Headon, Osborne, Bembridge, and Hamstead Beds (Palaeogene), Hampshire Basin—a bibliography (1814–1970)

Stratigraphy and correlation of the Headon, Osborne, Bembridge, and Hamstead Beds (Palaeogene), Hampshire Basin—a bibliography (1814–1970)

Stratigraphy and correlation of the Headon, Osborne, Bembridge, and Hamstead Beds (Palaeogene), Hampshire Basin—a bibliography (1814–1970)

Stratigraphy and correlation of the Headon, Osborne, Bembridge, and Hamstead Beds (Palaeogene), Hampshire Basin—a bibliography (1814–1970)

Jarosite from the Eocene of the Hampshire Basin

Jarosite from the Eocene of the Hampshire Basin

An Early Tertiary Surface in Wiltshire

A study of early Tertiary and Pleistocene gravels on Salisbury Plain demonstrates the nature of the early Tertiary surface there and indicates its preservation in the contemporary landscape on the highest summits of the Chalk. The composition of the Pleistocene gravels is treated as a guide to the character and former extent of the early Tertiary outcrop, of which only a few isolated and disturbed outliers remain. The early Tertiary gravels show affinities with the Tertiary outcrop in the western part of the Hampshire Basin. They appear to have rested on a polycyclic surface from which, in the later stages of its development, much of the Upper Chalk had been eroded. This surface is now represented in a small number of residual summits rising above the more extensively preserved mid-Tertiary surface. THE PRINCIPAL hypotheses of landscape evolution in southern England (P. Pinchemel, 1954; S. W. Wooldridge and D. L. Linton, 1955) disagree most significantly in the interpretation of the early Tertiary period. The scope for disagreement is evident on Salisbury Plain, where undoubted Tertiary deposits are absent and the configuration of the sub-Tertiary surface is correspondingly doubtful. This problem, on Salisbury Plain and elsewhere, was clearly appreciated by the officers of the Geological Survey. A. J. Jukes-Browne (1906) regarded the clay-with-flints as a relic of the Reading Beds and suggested that, where it occurs, the sub-Eocene surface is preserved. His conclusions implied that the elevation and partial denudation of the Pewsey anticline, and related folds, were of pre-Tertiary date. H. J. 0. White (1907) inferred uniform overstep of the Tertiaries from the Hampshire Basin northward across successively lower zones of the Chalk, and rejected the pre-Tertiary folding of the Chalk. Both geologists appear to have regarded the sub-Tertiary surface as an extension of the sub-Reading Beds surface. The implications of White's account are manifest in the work of Wooldridge and Linton. Their sub-Eocene contours (1955, Fig. 5) show a surface corrugated by Alpine structures and imply that the Alpine movements occurred after the modelling of the sub-Eocene surface. It is not clear whether the Chalk retained a mantle of Eocene sediments at the time of the folding; or whether these sediments were already partly denuded and the Chalk subject to erosion. Linton (1956) suggests that renewed erosion of the Chalk is likely to have occurred before the folding, but most of the erosion, and in particular the denudation of the Alpine folds, is inevitably referred by Wooldridge and Linton to the mid-Tertiary cycle. Over the crests of the principal anticlines this implies the removal of a few hundred metres of material during this cycle. The sub-Eocene surface is therefore identified by Wooldridge and Linton as a limited facet on the Chalk dip-slope near the present boundary of the Eocene outcrop, whereas the summit planation of the Chalk they regard as a product of the mid-Tertiary cycle. This view of Tertiary events is challenged by Pinchemel (1954), who accepts the extensive survival of an early Tertiary surface on the Chalk summits of southern England and suggests that the surface is of polycyclic origin. More recently M. J. Clark, J. Lewin and R. J. Small (1967), arguing from the distribution of Eocene debris and from the nature of the relief, have also concluded that the hill-top peneplain, at least near Marlborough, may be 'the outcome of a composite Eogene cycle'.

Observations on small-scale structural discontinuities in the London Clay and their relationship to regional geology

Summary The London Clay is well known as an engineering material and it is probably the most publicized example of a stiff fissured clay. Recently, growing interest has been shown in the small-scale structural discontinuities of this clay and their effects on the engineering behaviour of the material. The paper deals with observations of small discontinuities (or fissures) at sites in the London and Hampshire Basins. Orientation data from the various sites are plotted and analysed in the form of stereographic projections. The size and form of the discontinuity surfaces are considered and their distribution related to orientation and possible modes of origin. Both orientation and surface forms of discontinuities are related to the regional structure of the clay and adjacent sediments, and it is tentatively concluded that the general trends of discontinuity patterns in local areas, the local regional structure, and geological history can be correlated.

Clay mineral provinces in the tertiary sediments of the Hampshire Basin

AbstractAn X-ray diffraction study of over 600 specimens has shown that the Tertiary sediments of the Hampshire Basin are divided into two clay mineral provinces. The western province is characterized by kaolin from the West Country granites whilst the highly montmorillonitic sediments of the eastern province were partially derived from the dissolution of Chalk by tropical weathering.

The possible role of pathogenic fungi in die-back of Spartina townsendii agg.

A recession of Spartina townsendii, known as die-back, in mud flats in the Hampshire basin, showed symptoms inconsistent with attack by a primary pathogen. Soft-rotted rhizomes of die-back plants contained no bacteria or fungi until rotting was well advanced, and an examination of moribund material revealed no obviously pathogenic fungi. Seedlings planted in sand culture alongside heavily fungus-infected plants grew strongly, and unhealthy plants set beside healthy plants in the field did not pass on the infection to the healthy ones, but themselves recovered. On the other hand, healthy plants transplanted to die-back sites died. It was concluded that attack by a strong primary pathogen was not involved, and that the cause of the disease was essentially non-parasitic. The association of the die-back with certain definite types of site emphasized the need for an investigation of the ecological conditions governing occurrence of the disease.

The palaeogeography of the London Clay Sea

The London Clay of England (London and Hampshire Basins), Denmark, Germany, Holland and Belgium is briefly described, and the question of its correlation with the Paris Basin Lower Eocene summarised. The fauna and flora of the formation are reviewed as evidence of conditions at the time of its formation. The London Clay Sea is considered to have transgressed from a region of continuous Palaeocene-Lower Eocene sedimentation in the Danish-NW. German area, where it opened north-westwards, over Holland, Belgium and much of the London Basin, then to have transgressed farther over the Hampshire Basin to a Tethyan connection over the English Channel, finally to have retreated eastwards over S. England. The famous tropical flora is considered to have grown on the south-western coasts. The London Basin lower clays are probably represented by Reading Beds in the Hampshire Basin, and the English and Belgian London Clay by non-marine Sparnacian in the Paris Basin. It is recommended that a division into Palaeocene and Lower Eocene is adequate for the pre-Lutetian tertiaries of north-western Europe, instead of stage-names now in use; formation-names are unaffected. It is considered that palynology may yield more reliable datum-lines with these deposits than either facies-faunas or diachronous transgression-planes.

The Eocene Succession in the Eastern Part of the Enborne Valley, on the Borders of Berkshire and Hampshire

Summary Records obtained from trial borings with a combined penetration of over 8000 feet of strata are analysed, and an account is given of the Eocene succession revealed. This ranges from the Lutetian to the Sparnacian, comprising the Bracklesham, Bagshot, London and Reading formations. Their maximum proved thickness is 436 feet. The Chalk next beneath the Eocene is that of the Marsupites Zone except in the most northerly boring, where the Uintacrinus Zone was proved. Evidence is adduced suggesting that local variations in the thickness of the Reading Beds may be due to original irregularities on the surface of the Chalk. The Reading Beds, averaging 69 feet thick, have a marine “bottom bed” which varies in thickness from 6 to 25 feet; in one case this facies seems to persist to within 10 feet of the top of the series, foraminiferal glauconitic sand there replacing the mottled clay of nearby borings. Several seams of lignite were found, one of them resting on a seat-earth full of pyritized rootlets. The lithology of the rest of the succession resembles Wat of the Hampshire Basin rather than that of the London Basin of which it forms a tectonic part. Alternations of marine and estuarine episodes recur throughout; banks of shingle are common and beach-deposits occur; lignite, scattered or in actual seams, pervades the whole. The London Clay rests on a plane of erosion at the top of the Reading Beds; it falls into three main sections, the Lower Silts, Stiff Clays and Upper Silts.

Foraminifera from the London Clay

A systematic study of the Foraminifera from the London Clay of six localities in the London and Hampshire Basins resulted in 137 species and varieties being recorded, including 9 new species and 1 new variety. A short review of previous research is given and the lithology of the strata and the palaeoecology of the Foraminifera are discussed. The zonal significance of the Foraminifera is assessed.

The Excavation of Two Round Barrows at Poole, Dorset

The excavation of these barrows was undertaken in the autumn of 1949 for the Ministry of Works in advance of building. They stood immediately adjacent to each other on Plateau Gravel overlying the Bagshot Beds towards the western extremity of the Hampshire Basin, and only a hundred yards north of the crest of the Bourne Bottom which leads down to Bournemouth and Poole Bay about three miles distant (fig. 1). The surrounding heath is rich in round barrows, and the district has yielded plentiful evidence of prehistoric man.

The Eocene succession at afton brickyard I.O.W.

The object of this paper has been to provide more material to piece together the jig-saw of the very varied development of the Eocene strata in the Hampshire Basin. The actual piecing together, I leave to those more experienced than myself. Some further light has also been thrown on the little-known faunas of the transition beds between the well-known Barton and Upper Bracklesham successions.

Four species of discinisca [brachiopoda] from the Eocene of the Hampshire Basin

Four species of discinisca [brachiopoda] from the Eocene of the Hampshire Basin

British Museum (Natural History) The London Clay Flora

IN this noble volume recently published by the Trustees of the British Museum, Mrs. Reid and Miss Chandler describe the results of an intensive study of thousands of fruits and seeds strewn along the foreshore of Sheppey and Herne Bay by the action of the sea on the cliffs of clay in which the drifted debris was originally embedded. The London Clay, reaching in places a thickness of 500 ft., is exposed at the surface or lies beneath superficial accumulations over a large area in Middlesex, Surrey, Essex, Kent and hi the Hampshire basin. In addition to remains of crocodiles, turtles, shells of Nautilus and other marine creatures, the clay contains innumerable samples of vegetation, mainly seeds and fruits, which grew on the northern shore of the Tethys Sea. British Museum (Natural History). The London Clay Flora. By Eleanor Mary Reid Marjorie Elizabeth Jane Chandler. Pp. viii + 561 + 33 plates. (London: British Museum (Natural History), 1933.) 50s.