Barton Clay Research Articles

Disentangling the Impact of Global and Regional Climate Changes During the Middle Eocene in the Hampshire Basin: New Insights From Carbonate Clumped Isotopes and Ostracod Assemblages

AbstractWe present a novel multiproxy data set (bulk and clumped isotopes on gastropod shells and variations in ostracod assemblages) of the Hampshire Basin (Southern‐England) that sheds light on the connection between the North Sea and the Atlantic Ocean through the English Channel during the deposition of the Barton clay formation (latest Lutetian—Bartonian, middle Eocene; ∼41–40 Ma). During this time period, the English Channel operated as a gateway between the warmer Atlantic Ocean and the colder North Sea waters. High‐latitude water mixing combined with the regional hydrological cycle and sea‐level variations, may have contributed to mitigate the water temperatures in the Hampshire Basin, with an average recorded of ca. 25°C. In the uppermost part of the section the connection between the two water masses was limited or absent as evidenced by warmer (up to ca. 35°C) Atlantic Ocean temperatures in the Hampshire Basin. The large differences in average oxygen isotope composition of seawater (δ18Owater) recorded (from δ18Owater −1.7‰ to δ18Owater of −0.7‰) evidenced large salinity differences between the Atlantic Ocean and the North Sea. Ostracods suggest that the temporary connection between those two water masses was caused by relative regional sea‐level variations. This scenario could be partially linked to glacio‐eustatic sea‐level changes related to climate fluctuations probably associated with the MECO event.

Discussion on ‘Reactivation of landsliding following partial cliff stabilization at Barton-on-Sea, Hampshire’ by M. E. Barton & P. Garvey Quarterly Journal of Engineering Geology and Hydrogeology , 44, 233–248

We are familiar with the sites mentioned by Barton & Garvey (2011) from site visits and by working through a series of back-analyses of the sections presented in their paper. We wish to bring some observations to the authors’ attention, and seek their views. First, the basal shear surfaces of the Hoskin’s Gap, Hoskin’s Gap West and Central Amenity area slips are all shown in the figures of the paper to have occurred along bedding planes situated in the F and H horizons of the Barton Clay, but at different although closely spaced stratigraphic positions. We have followed the line of this slip surface (notionally in the F bed) where it crops out in the cliffs west of the Cliff House landslide nearly as far as Chewton Bunny, and are confident that it follows only one stratigraphic horizon. Hence, we think it improbable that it follows a variety of beds to the east of the Cliff House landslide. However, this upper slide-prone horizon is admittedly more …

Reactivation of landsliding following partial cliff stabilization at Barton-on-Sea, Hampshire, UK

Abstract The historically unstable eastern side of the Barton Clay coastal outcrop was subject to stabilization works during 1967–1968, the principal part of which was a 1450 m long filter drain with a sheet pile cut-off aimed at the seepage-prone Barton Sand–Barton Clay junction. Subsequently four reactivated landslides occurred and by 2008 amounted to c . 46% of the total length of the filter drain. Two of these landslides were massive failures of the whole undercliff. This paper examines the relations between the landslides and the stratigraphy, including the presence of the known preferred surfaces of shearing, and the characteristic geomorphological modes of degradation in the Barton Clay undercliffs. It is shown that although the original drainage design reflected the influence of the stratigraphy, there was insufficient consideration of the hazards posed by the natural patterns of degradation and their geomorphological expression. The earlier two of the landslides were followed by remedial measures but the latest two are continuing. Although the cliff toe is well protected by a robust rock armoured revetment, the western end of this area is now reverting to the state that existed before the stabilization works were installed.

Glacioeustasy during the middle Eocene? Insights from the stratigraphy of the Hampshire Basin, UK

The sedimentary strata of the Hampshire Basin constitute some of the best-preserved Palaeogene sequences worldwide, and include the traditional ‘unit stratotype’ for the Bartonian (~36.9–41.4Ma). The Barton Clay Formation at Alum Bay on the Isle of Wight (IOW) was studied to assess the evidence for middle Eocene sea-level variation in records of grain size, sediment properties, faunal assemblage, foraminiferal diversity indices and foraminiferal stable isotopes. Sedimentary cycles of 1–10Myr (third order) and 0.2–0.5Myr (fourth order) duration are reported and interpreted to reflect ~20–60 metre variations in water depth. Additionally, an integrated magneto-bio-chemostratigraphical age model for the succession at Alum Bay is presented and new and published litho- and bio-stratigraphical markers are used to correlate additional successions. Based on this age model, it appears that during the late Lutetian and early Bartonian (~42–38Ma), water depth variation identified within the basin was synchronous.Sedimentary and fossil evidence supports episodic uplift in the eastern part of the Hampshire Basin during the Bartonian, which at present precludes the calculation of eustatic sea-level. However, the amplitude and frequency of water-depth variations identified in the Barton Clay Formation, and correlations to published sea-level curves, are consistent with a component of these changes being glacioeustatic during the middle Eocene. There is also evidence for a large excursion (δ18O>1‰) in the mono-specific benthic foraminiferal oxygen-isotope record (Alum Bay) ~39.9Ma, which is correlated to the isotope excursion at the ‘middle Eocene climatic optimum’ previously reported in the Southern Ocean, and other localities. A contemporaneous water-depth increase of ~40m at Alum Bay may indicate that a component of this ‘global’ oxygen-isotope excursion results from a reduction in continental ice storage.

Anguimorph lizards (Squamata, Anguimorpha) from the Middle and Late Eocene of the Hampshire Basin of southern England

The Hampshire Basin in southern England is the only sequence virtually spanning the Eocene-Oligocene boundary in western Europe. It has provided an opportunity to observe changes in populations across the Grande Coupure event, as an overturn in the squamate assemblage of continental Europe has also been noted. Five Tertiary formations have yielded lizard material: Creechbarrow Limestone, Barton Clay, Headon Hill, Bembridge Limestone and Bouldnor Formation. These formations span the period from the late Middle Eocene to the earliest Oligocene. Localities in the Hampshire Basin represent a depositional environment with an increasing tendency towards lacustrine and riparian influences in later horizons. The anguimorph fauna includes one new anguine, Headonhillia parva gen. et sp. nov., diagnosed by: (1) small size, (2) large parietal area levis, and (3) short parietal crista postfovealis. Another anguine, Ophisaurus sp., is identified on the basis of the morphology of the parietal. Three further morphotypes of anguines have been distinguished based on dentary, vertebrae and osteoderm specimens. Two types of indeterminate Anguidae are distinguished on the basis of maxillae and dentaries and three morphotypes of indeterminate Anguidae on the basis of vertebrae. Glyptosaurines have been identified in three members on the basis of osteoderms. ‘Necrosaurs’ have also been identified from the Hampshire Basin: two types, distinguished on the basis of dentary material and osteoderms, are identified as indeterminate ‘necrosaurs’. One type of indeterminate Varanoidea is distinguished on the basis of dentaries. The presence of anguids in the Hampshire Basin is well documented, and they appear to form a consistently diverse assemblage throughout the sequence. Anguine osteoderms are present in both pre- and post-Grande Coupure material. Pre-Grande Coupure vertebrae and osteoderms are similar in size to those of adult Recent anguine Pseudopus apodus, although many of the Hampshire Basin anguines, including Headonhillia parva, represent the smallest anguines known to date.

The slip surface in the D Zone of the Barton Clay

The most dominant of the preferred bedding plane surfaces of shearing in the Eocene Barton Clay coastal cliffs of the Hampshire Basin is that near the base of the D Zone. This is utilized as the basal surface of compound landslides virtually throughout its 2.3 km outcrop from near the cliff top to beach level, an elevation change of nearly 30 m. The shear zone is located along a thin seam of dark chocolate brown clay, which has been investigated by X-ray powder diffraction mineralogical analysis, X-ray fluorescence chemical analysis, scanning electron microscope study of the microfabric and ring shear tests. The dark seam is slightly more clay rich and has a slightly lower value of residual shear strength than the ambient D Zone clay. The reason for its preference during landsliding is discussed. The available evidence suggests that although some previous shear displacement by flexural slip during folding may have occurred, the main displacement results from the lateral rebound response to coastal recession, involving a reorientation of any previous clay particle alignment. Lateral rebound initiates progressive failure, which leads to the compound landsliding of the in situ clay slopes.

Winners and losers: stable isotopes and microhabitats of living Archaiadae and Eocene Nummulites (larger foraminifera)

This paper discusses isotopes in larger foraminiferal calcite from two contrasting settings: modern Florida Bay, dominated by Archaiadae (the “winners”); and the Upper Eocene Barton Clay of England, locally dominated by Nummulites (“the losers”). The archaiads (plus peneroplids and soritids) were mainly collected from Thalassia leaves. They yield signatures that closely reflect strong isotopic gradients in sea water across Florida Bay and the outer patch reefs. Isotopic signatures of eurytopic Androsina lucasi record extreme conditions to the north of the bay, which includes δ 13C evidence for much nutrient-regeneration. Such tolerance of relatively eutrophic conditions may explain the capacity of Archaiadae for survival in the Caribbean region during the Neogene. Isotopes of Nummulites prestwichianus from the basal Bartonian compare more closely with data from living nummulite Heterostegina. δ 18O indicates a yearly growth cycle under tropical bottom water temperatures with an annual range of approximately 2.5°C. Carbon isotopes show a trend towards heavier values with growth, here related to decelerating rates of calcification and, perhaps, the additional effects of test-thickening on carbon isotope fractionation by endosymbionts. The nummulitic data indicate a much more stable carbon and nutrient cycle in the basal Barton Clay than seen in the Florida Bay mudmound assemblage. This is consistent with their presumed stenotopic and oligotrophic life habit. It could well explain their vulnerability to extinction after the mid-Eocene, and the post-Aquitanian decline of larger rotaliids and reefs in the Caribbean region.

A model for predicting groundwater level response to meteorological changes

Abstract A simple model, based on the overall soil water balance, has been developed for the prediction of groundwater levels in response to meteorological changes. The model consists of two parts as follows: A soil moisture deficit model which uses daily rainfall and potential evapo-transpiration data to estimate the effective rainfall entering the ground beyond the influence of evapo-transpiration. A model relating the effective rainfall to the water table and predicting the groundwater level response. Rainfall, potential evaporation and water level records are required for at least two years in order to perform a split record test. The data from the first year are used for calibrating and from the second year for testing the model. The model has been applied to a cliff top site adjacent to the degrading coastal cliffs at Naish Farm, near Highcliffe, Hampshire. The necessary data has been collected over the two year period from October 1982 to October 1984. The groundwater level data used is for the upper permeable layer of Plateau Gravel. The Plateau Gravel acts as a groundwater store, supplying seepage both down into the underlying Barton Clay and, under winter conditions, outwards to the cliff face. The meteorological data were obtained by setting up a local weather station. The results show a good model fit to the observed data. The model is suitable for general application. It is considered that it may prove of particular value for areas with active landslides as a means of understanding the incidence and rates of slope movements.

Seepage characteristics and landsliding of the A3 zone of the Barton Beds

ABSTRACT The most characteristic feature of the Barton Clay cliffs of Christchurch Bay is the presence of a number of preferred bedding plane surfaces of shearing. Most of these are contained within clay horizons and the reason for their preferential use by the coastal landslides is unknown. One surface, however, is at the base of the 2.7 m thick A3 Zone which consists of inter-bedded sand and clays. This surface is well exposed and forms a distinct feature in the cliffs throughout nearly the whole of the 1.5 mile coastal outcrop of the A3 Zone. The paper discusses the reason why a shear surface is preferentially developed at this stratigraphic location. Three possible causes are discussed under the headings of (i) pore pressure fluctuation, (ii) seepage erosion and piping and (iii) equilibration response time. The first two are well established theories but the third is a new hypothesis derived from the original Bishop and Bjerrum theory of delayed equilibration. It is considered that the discussion is useful in the general context of landsliding at sand/clay junctions in overconsolidated soils.

Characteristics and rates of the various slope degradation processes in the Barton Clay Cliffs of Hampshire : Barton, M E; Coles, B J Q J Engng GeolV17, N2, 1984, P117–136

Characteristics and rates of the various slope degradation processes in the Barton Clay Cliffs of Hampshire : Barton, M E; Coles, B J Q J Engng GeolV17, N2, 1984, P117–136

A geological appraisal of the site of the foundation failure of the giant oil tanks at Fawley, Hampshire

Summary Two giant oil tanks (79.3 m diameter by 19.5 m high) were constructed at Fawley in 1967-68. The tanks were founded on a reinforced concrete slab supported by piles of varying lengths taken through alluvium and end-bearing in Valley Gravel which overlies Barton Clay (Eocene). Totals of 1580 and 1652 piles, respectively, were used for each tank. The foundations failed during water-loading tests with a maximum depression of 0.425 m in one of the reinforced concrete slabs. Post-mortem examination of the foundations revealed defects in a number of piles, and after further tests and investigations, Professor G. A. Leonards concluded that the failure was due to defective piles. The success of the original design was critically dependent on the geology. Particular problems on which attention was focussed included the continuity and thickness of the gravels, their variation in density, the character of the interface between Valley Gravel and Barton Clay and the lithological variations within the alluvium. These problems are examined here in relation to the existing geological knowledge of the region. Of particular significance is the conclusion that, in part, the variation in density within the gravels is due to the existence of Flandrian gravel overlying Pleistocene terrace gravel. Isopachytes of the gravels have been drawn along with contours on the upper and lower surfaces. These are compared with the settlement contours of the failed foundation slab and it is concluded that there is no correlation between them.

The role of a soil × dietary sulphur interaction in the impairment of copper absorption by ingested soil in sheep

SummaryFour repletion experiments were carried out to clarify the roles of molybdenum, sulphur and iron in the inhibition of copper absorption by ingested soils. In each experiment, groups of four to six hypocupraemic Scottish Blackface ewes were repleted for 21 days with diets containing CuSO4 and/or soil Cu and the responses in plasma Cu used to assess the availability of the Cu supplied.In Expts 1 and 2, three soils varying in Mo but high in Fe content and derived from Lower Lias Clay, Namurian Shale and Weald loam were added at 100 g/kg D.M. to diets of low (1·0) and high (4·1 g/kg D.M.) S contents: they provided 3·1, 2·8 and 0·1 mg Mo/kg D.M. respectively. When compared with groups given no soil, each soil increased plasma Cu repletion in the low S experiment and decreased it in the high S experiment. Inhibition was thus not completely dependent on soil Mo but dependent upon dietary S.Soils varying in Fe content were compared in the manner of the above experiments in Expts 3 and 4. Two Fe-rich soils, developed from the Upper Chalk and a Barton Clay and providing 2·8 and 1·5 g Fe/kg D.M., impaired Cu repletion on the high S diet but not on the low S diet. A soil, developed on a sand from the Bagshot Beds and providing only 0·15 g Fe/kg D.M., did not impair repletion but FeSO4, providing 0·8 g Fe/kg D.M. did so, irrespective of dietary S content. Ingestion of Fe-rich soils in a high S diet caused three-fold increases in rumen sulphide concentrations 5 and 24 h after feeding. It is suggested that soil ingestion impairs Cu absorption in sheep by trapping S as heavy metal sulphides such as FeS and releasing sulphide in the acid abomasum.

The characteristics and rates of the various slope degradation processes in the Barton Clay Cliffs of Hampshire

Summary Research is in progress to determine the nature and pattern of the degradation processes in an actively eroding stretch of the Barton Clay cliffs in the Naish Farm area of Highcliffe, Hampshire. In response to loss of beach material the rate of recession has accelerated and is currently averaging 1.9 m/year, resulting in steepening of the overall cliff angle from an average of 13° in 1947 to a maximum recorded average of 19° in 1976. The presence of three preferred bedding plane shear surfaces at various elevations within the cliff produce a benched type of cliff profile, comparable with that seen in the Gault and Lias Clay controlled cliffs of Fairy Dell, Dorset but in contrast with the published descriptions of London Clay cliffs. The degradation processes include scarp slumping, spalling (including toppling and soil falls), bench sliding (involving movement of colluvium over a preferred bedding plane), debris sliding (including movement of screes over clay scarps), mud sliding (i.e., the traditional lobate ‘mudflows’), mud runs (true flows), stream (or gully) erosion and man-related processes. Regular surveying and monitoring using a variety of techniques and having to surmount difficult field conditions, has begun to elucidate the characteristics, rates and inter-relationships of these processes. A flow chart representing the systematic transfer of soil from the in situ state via various colluvial modes (including the three bench levels) en route to the sea and an accompanying colluvial soil budget for the year July 1981 to July 1982 has been drawn up. It is shown that bench sliding is by far the most significant process in terms of volume of colluvium moved through the under-cliff, accounting for 930f the total volume of colluvium contained in the area. Mud and debris sliding, although important processes, are of relatively minor significance.

Determination of ground moduli by a seismic noise technique on land and on the sea bed

Seismic noise appears to be present at the surface of the earth in varying degrees. It is familiar as a background signal when seismic refraction surveys and similar geophysical measurements are being carried out. The source of this noise appears to be partly atmospheric, and partly vehicle movement and other phenomena. That correlation techniques can be used for measuring surface wave velocities has been demonstrated by Roesler. Filtered white noise' signals were applied to an electromagnetic vibrator and the correlation observed with a signal transmitted through the ground and detected by a geophone. In the technique using seismic noise, correlation is observed between signals recorded from three geophones in a triangular array. The recordings are of the naturally occurring seismic noise. The test method, interpretation of results and calculation of dynamic moduli are described. Measurements were made at three sites. The authors concluded that seismic noise may be used to determine the variation of shear wave velocity with depth, the advantage of the technique being that deep measurements may be made easily without large vibration generators. The measurements also showed that the siffness properties of the boulder clay, the London clay and the Barton clay of the Christchurch Bay sea bed were similar. (TRRL)

The degradation of the Barton Clay Cliffs of Hampshire

Summary The Barton Clay crops out along a 4·8 km stretch of the Hampshire coast and together with its capping of Plateau Gravels forms a cliff profile averaging around 30 to 37 m high. The original classic work on the geology of the Barton Clay had suggested a total thickness of only 34·5 m; more recent work involving boring and levelling on the cliff face has shown the formation to be 46·4 m thick. Active degradation of the outcrop creates a markedly stepped profile, relatively flat bench levels being separated from one another by steeper scarp slopes. The benches are underlain by up to 6 m of slipped debris or bench rubble. The scarps are formed by exposures of the solid Barton Clay and Plateau Gravel in the case of the top scarp. The interface between the bench rubble and Barton Clay is formed by a shear surface, an underground continuation of the scarp surfaces, which has been polished and grooved as a result of the seaward movement of the bench rubble. These shear surfaces are developed along particular, identifiable stratigraphic horizons within the Barton Clay and tend to develop along these horizons irrespective of the height of the latter within the cliff profile. Variations in the morphology occur laterally along the outcrop and can be related to the erosional history and partly to the geology. Five individual processes of degradation are particularly active on the undercliffs; these comprise bench sliding which is sliding of the bench rubble over the shear surfaces, collapse of the scarp slopes or scarp slumping, wearing down of the scarp slope by weathering or scarp spalling, and erosion by mud-flows and running water. Both mud-flows and streams when well developed cut through bench rubble and into the scarp slope and locally destroy the stepped profile. The current activity of these processes is due to marine erosion of the toe, the net result of the processes being a progressive retreat of the cliff top averaging over one metre per year in some places.

Notes on fossil whales from the Upper Eocene of Barton, Hampshire

Three vertebrae discovered in the Barton Clay of Hampshire are described and assigned to two archaeocete whales: the short-bodied dolphin-like Zygorhiza and the large serpentine Basilosaurus. This is the first record of the latter genus outside North America.

Les diverses interpretations du terme de "Bartonien"

Abstract The various interpretations of the term "Bartonian." Concludes that the term Bartonian should be extended to include all formations from the Lutetian to the Oligocene. Three major subdivisions on the basis of distinct paleontologic zones are recognized: a lower zone--Sables moyens of the Paris basin, Upper Bracklesham beds of the London basin, and Ledian sands of Belgium; a middle zone--Cresnes sands (Paris basin), Barton clay (London basin), Wemmel sands (Belgium); and an upper zone--Pholadomya-bearing marls and gypsum beds (Paris basin), and Long Mead End Sands and Lower Headon beds (London basin). The upper zone is apparently not present in Belgium.

The Horizons of Bryozoa (Polyzoa) in the Upper Eocene Beds of Hampshire

I. I ntroduction . This communication is for the purpose of describing the horizons on which Bryozoa (Polyzoa) occur in the Upper Eocene Beds (marine clays and sands) of Hampshire. No claim is made to establish special zones with particular species confined to them, but those beds are indicated that contain a relative abundance or deficiency of bryozoan remains, within the three broad divisions of the Upper Eocene (Lower, Middle, and Upper Barton Beds). The geology of this portion of the Hampshire Basin may first be briefly reviewed. The Barton Clay and Barton Sands form part of the well-known Hampshire Syncline, and are exposed at Christchurch Bay, and also at Alum Bay and Whitecliff Bay, in the Isle of Wight. The type-section at Barton Cliffs on the mainland consists of sandy clays in the lower part (50 feet), dark sandy clays and stiff drab clays in the middle part (56 feet), and clayey sands and light-coloured sands in the upper part (96 feet). (Total = 202 feet.) Corresponding Upper Eocene Beds in the Isle of Wight attain a greater thickness. At Alum Bay, the western end of the island, they reach a total of 338 feet. At Whitecliff Bay, at the eastern end of the island, they reach a total of 368 feet (9, p. 108). Even these thicknesses may fall short of the maximum totals in the Isle of Wight, owing to the high angle of dip, and to the compression to which so many of the strata have clearly been

Note on the Cervical Vertebra of a Zeuglodon from the Barton Clay of Barton Cliff (Hampshire)

In the year 1876, Prof. H. G. Seeley published in the Journal of this Society a short account of a small Zeuglodon from the Barton Clay of Barton Cliff. This specimen, which was made the type of the species Zeuglodon Wanklyni, was discovered in 1872 and came into the possession of Dr. Arthur Wanklyn, by whom Prof. Seeley was requested to draw up some notes on this important find. Fortunately he did so, for at Dr. Wanklyn's death all trace of the specimen was lost, and it was no doubt on this account that the notes had to be published without illustrations. In 1881, Prof. J. W.,Iudd 2 gave an account of the discovery of a cetacean vertebra in the Brockenhurst Beds of Roydon (Hampshire) : this specimen was described by Prof. Seeley under the name Balænoptera Juddi , but he now, no doubt rightly, regards it as belonging to a Zeuglodon . Until quite lately no further remains of Zeuglodonts had been found in Britain, but some months ago Mr. H Eliot-Walton, who has done much collecting in the Hampshire cliffs, found a cervical vertebra of Zeuglodon , and it is to this specimen that the present note refers. The vertebra is a posterior cervical, probably the sixth. The centrum is roughly oval in outline, its greatest width, which is situated nearer the ventral than the dorsal surface, being greater than the height. The anterior face is almost flat, with a median depression, and marked by irregular ridges

III.—Note on the Discovery of a very fine Example of Pleurotoma prisca, Solander, sp. (1766), at Barton, Hants

In one of his recent visits to the Natural History Museum, Major C. E. Beadnell kindly showed me a fine example of the well-known shell Pleurotoma prisca, which had been obtained some years ago by his son, Mr. Hugh J. L. Beadnell, F.G.S. (now of the Geological Survey of Egypt), when collecting specimens from the Barton Clay (Middle Eocene) in the historical cliffs at Barton, Hampshire, whence, prior to 1766, Gustavus Brander, F.R.S., made his famous collection, some of the specimens of which are still preserved in the British Museum (Natural History).