Thanet Sand Research Articles

Jet grouting to new depths in the Lambeth Group and Thanet Formation beneath London

A jet grouting trial was undertaken within the Thames Tideway Tunnel shaft at Kirtling Street in Battersea, SW London, to assess the viability of the technique within the Lambeth Group and Thanet Formation sediments up to 60 m below ground level. There was no precedent industry experience of jet grouting in the UK at this depth and in these soil types. Four, separate, upper and lower grout columns were constructed respectively within upper and lower granular zones inside the shaft footprint, and then exhumed for inspection and measurement during ensuing excavation within the diaphragm wall lining. Target diameters for the upper columns were achieved within granular channel sand and Laminated Bed material, with minimal vertical deviation. These were not so successfully achieved, however, within stiff cohesive Laminated Bed and Lower Shelly Clay materials. Formation of the lower columns was severely restricted in dense gravel belonging to the ‘Pebble Bed’ and stiff gravelly clay, at the top of the Upnor Formation, but target diameters were being achieved in the lower portion of the formation, comprising Upnor sand. At their base, the column diameters were, again, restricted in the very dense sand at the top of the Thanet Formation.

Detrital zircon U-Pb ages and source of the late Palaeocene Thanet Formation, Kent, SE England

The sources of the Paleocene London Basin marine to fluviodeltaic sandstones are currently unclear. High analysis number detrital zircon U-Pb age investigation of an early-mid Thanetian marine sand from East Kent, reveals a large spread of zircon age peaks indicative of a range of primary sources. In particular, a strong Ediacaran age peak is associated with the Cadomian Orogeny, while secondary peaks represent the Caledonian and various Mesoproterozoic to Archean orogenies. The near absence of grains indicative of the Variscan orogeny refutes a southerly or southwesterly source from Cornubia or Armorica, while the strong Cadomian peak points to Avalonian origin for a major component of the material. Furthermore, the relatively well expressed Mesoproterozoic to Archean age components most likely require significant additional Laurentian input. Comparison to published data shows that both Devonian Old Red Sandstone and northwesterly (Avalonia-Laurentia) derived Namurian-Westphalian Pennine Basin sandstones show strong similarities to the Thanetian sand. This pattern is consistent with derivation of Thanetian material via a SE draining proto-Thames River system that was initiated in the Paleocene due to uplift of western and northwestern Britain. This river system would have incised and eroded cover sandstones and potentially also Avalonian basement of mid to north Wales and England. However, the possibility of a contribution of Laurentian grains directly from the north via longshore drift cannot be excluded by the data, and the extent to which the sediment source signatures of Paleogene sands of the London Basin are variable both geographically and over time remains unclear.

Development of the ground model for the Clay-with-flints Formation: adventures in geological boundaries

The Clay-with-flints Formation crops out on the high chalk plateaux in southern England. Changes in terminology are summarized and distinctions from adjacent similar deposits (e.g. Valley Gravel) are detailed. A threefold division of the transition zone between the two deposits is proposed based on degree of disturbance. Relationships with parent materials are discussed through structural and spatial relationships, as shown on published maps and in memoirs. Dominant pedological processes involved in the formation of the Clay-with-flints Formation from the Lambeth Group are described. A twofold division between the two is proposed based on physical changes. In addition to geological and pedological information, the deposit was studied through ground investigation data from 60 km of motorway network, which covers the variation in the Paleocene deposits (Lambeth Group facies (Reading Formation to Woolwich Formation) and the increasing presence of Thanet Sand Formation along the North Downs, east of approximately Leatherhead). The resulting ground model requires detailed knowledge of the microstructures of the chalk, the facies variation of Paleocene and Pliocene deposits, and temperate climate pedological processes in the vadose zone. Future work to study the engineering properties reflecting the variation of both the Paleocene facies and the development of the vadose zone is summarized. Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology

Mineralogical and geochemical characterisation of warm-water, shallow-marine glaucony from the Tertiary of the London Basin

AbstractGlaucony is present in the Palaeocene sediments of the London Basin, from the Thanet Sand Formation to the gravel beds at the base of the Lower Mottled Beds of the Reading Formation. The Upnor Formation glaucony is a rare example of formation in warm, shallow, brackish water and this, combined with the ready availability of fresh material from boreholes, make this study important in developing our understanding of this mineral. Glaucony comprises up to 50% of the Upnor Formation, a grey to green sandstone, of variable thickness and composition, which was deposited in awarm, shallow, marine to estuarine environment, ∼55.6–56.2 Ma. Using morphological criteria, X-ray diffraction data and K+abundance, the Upnor glaucony may be defined as evolved. The underlying shallow marine Thanet Sand contains <5% of nascent to slightly evolved glaucony. The rare earth element (REE) data for the Upnor Formation suggest more than one source for the sediment from which the Upnor glaucony formed, while the ThanetREEdata are consistent with a large detrital clay component.In the Upnor Formation, the large proportion of glaucony that occurs as granule fragments rather than whole granules, and the high-energy estuarine to shallow-marine environment of deposition, are indicative of reworking. The Upnor glaucony is inferred to be intraformationally reworked, rather than derived from the Thanet Sand Formation. The glaucony may have formed in sediments deposited away from the main estuarine channel, and been subsequently reworked into higher-energy sediments.Warm seas with freshwater mixing are more typically characteristic of verdine formation than of glaucony. The shallow, brackish environment of deposition suggests that there is not a clear distinction between the environmental requirements of verdine (or odinite) and glaucony (or glauconite), as is often proposed. The highly fractured, delicate nature of some granules indicates that they have experienced somematurationin situ, after reworking.The oxygen and hydrogen isotopic compositions of Upnor Formation shark teeth and glaucony point to formation in low-salinity water at ∼23 ± 3°C, also consistent with formation in the Upnor Formation, rather than in a fully marine sediment and subsequent reworking. A higher than normal temperature of formation may have increased the rate of evolution of glaucony.Our multidisciplinary study considers many of the factors relating to depositional environment that must be considered when glaucony-rich facies are encountered in comparable palaeo-environmental settings elsewhere in the geological record.

Closed form solution of Eigen frequency of monopile supported offshore wind turbines in deeper waters incorporating stiffness of substructure and SSI

Offshore wind turbines (OWTs) are dynamically loaded structures and therefore the estimation of the natural frequency is an important design calculation to avoid resonance and resonance related effects (such as fatigue). Monopiles are currently the most used foundation type and are also being considered in deeper waters (>30m) where a stiff transition piece will join the monopile and the tapered tall tower. While rather computationally expensive, high fidelity finite element analysis can be carried to find the Eigen solutions of the whole system considering soil–structure interaction; a quick hand calculation method is often convenient during the design optimisation stage or conceptual design stage. This paper proposes a simplified methodology to obtain the first natural frequency of the whole system using only limited data on the WTG (Wind Turbine Generator), tower dimensions, monopile dimensions and the ground. The most uncertain component is the ground and is characterised by two parameters: type of ground profile (i.e. soil stiffness variation with depth) and the soil stiffness at one monopile depth below mudline. In this framework, the fixed base natural frequency of the wind turbine is first calculated and is then multiplied by two non-dimensional factors to account for the foundation flexibility (i.e. the effect of soil–structure interaction). The theoretical background behind the model is the Euler–Bernoulli and Timoshenko beam theories where the foundation is idealised by three coupled springs (lateral, rocking and cross-coupling). 10 wind turbines founded in different ground conditions from 10 different wind farms in Europe (e.g. Walney, Gunfleet sand, Burbo Bank, Belwind, Barrow, Kentish flat, Blyth, Lely, Thanet Sand, Irene Vorrink) have been analysed and the results compared with the measured natural frequencies. The results show good accuracy (errors below 3.5%). A step by step sample calculation is also shown for practical use of the proposed methodology.

Fibre optic monitoring of a deep circular excavation

This paper describes part of the monitoring undertaken at Abbey Mills shaft F, one of the main shafts of Thames Water's Lee tunnel project in London, UK. This shaft, with an external diameter of 30 m and 73 m deep, is one of the largest ever constructed in the UK and consequently penetrates layered and challenging ground conditions (Terrace Gravel, London Clay, Lambeth Group, Thanet Sand Formation, Chalk Formation). Three out of the twenty 1·2 m thick and 84 m deep diaphragm wall panels were equipped with fibre optic instrumentation. Bending and circumferential hoop strains were measured using Brillouin optical time-domain reflectometry and analysis technologies. These measurements showed that the overall radial movement of the wall was very small. Prior to excavation during a dewatering trial, the shaft may have experienced three-dimensional deformation due to differential water pressures. During excavation, the measured hoop and bending strains of the wall in the chalk exceeded the predictions. This appears to be related to the verticality tolerances of the diaphragm wall and lower circumferential hoop stiffness of the diaphragm walls at deep depths. The findings from this case study provide valuable information for future deep shafts in London.

Canary Wharf Crossrail station cofferdam, London, UK: design, construction and performance

The construction of the first Crossrail station at Canary Wharf in London, UK reached a significant milestone in March 2012 when the station box was formally handed over to Crossrail for the preparation of the tunnel eyes to receive and re-launch the tunnel-boring machine. The station box is constructed in the North Dock at Canary Wharf in around 9 m of dock water. Excavation of the 265 m long, 25–30 m wide and 18 m deep station box was completed in about 12 months. This paper provides useful guidance for practising engineers on the design and construction of cofferdams' retaining walls in a dock environment. It describes the performance of the retaining structures constructed using the innovative Japanese Giken tubular pile system. Some details are also included of the site-wide dewatering undertaken to lower the groundwater in the Chalk and control it, allowing excavation into the Upnor Formation and Thanet Sand. The effects of unexploded ordnance probing on the performance of the retaining wall are described. Together with details of the laboratory tests undertaken to inform the ship impact berm design and the monitoring system used to verify the retaining wall design and comparison of the predicted and measured wall movements during excavation.

TBM and spoil treatment selection process – case history Crossrail C310 Thames Tunnel

AbstractSlurry TBM versus EPB TBM The contract C310 comprises the construction of the Plumstead and North Woolwich Portals and the twin tube Thames Tunnel, which has a length of approximately 2.6 km between the two portals. The two TBMs used for the construction of the Thames Tunnel will drive through varying ground conditions (Thanet Sand, River Terrace Deposit (gravel), and chalk) below the water table. During the drive under the River Thames, the tunnels will only have an overburden of approximately 12 m. The effect of pressure variation due to the tidal River Thames has to be accounted for in the control of the tunnelling. The tunnel will pass underneath several grade II listed buildings, utilities, adjacent to operational railway tracks and close to existing subway tunnels. Previous experience of the handling and disposal of excavated chalk has been gained on several tunnelling projects in chalk, most notably the Dartford Road Tunnels, the Channel Tunnel, the Brighton Stormwater Tunnel, the Lille Metro Tunnel, the Socatop Road Tunnel near Paris and Channel Tunnel Rail Link CTRL 320. The Contract allowed for both Mixshield and EPB TBM Technology. The advantages and disadvantages of a TBM‐S with Earth Pressure Balanced face support (EPB‐TBM) and a TBM‐S with Slurry Face support (Mix‐Shield TBM) for the C310 Thames Tunnels were discussed after contract award and a comparative risk assessment was developed. A Mixshield TBM is more expensive but outperformed the EPB TBM in the overall scoring of risk assessment and therefore it has been decided to use this type at C310.

High Speed 1, UK: a silty sustainable earthworks case study

In the UK, the High Speed 1 project formally pioneered on a large scale the earthworks design philosophy of maximising reuse of excavated materials and minimising waste. Now, in 2011, it is considered best practice for sustainable earthworks on all major infrastructure projects. This philosophy was a requirement of the Channel Tunnel Rail Link Act 1996, and a waste minimisation hierarchy was therefore included within construction specifications. This paper presents two different solutions found on one contract to enable two difficult silty soils, which would historically have gone to mitigation or taken off site, to be successfully retained and used as engineered fill. The first soil was quarry overburden material of Thanet Sand with considerably varying optimum moisture contents. A ‘family of curves' approach was developed to enable rapid single-point compaction testing to predict optimum moisture contents. The second was an artificial soil called cement kiln dust, generated as a by-product of cement manufacture. This material had a high silt proportion, and very high natural and optimum moisture contents, and was in a condition much wetter than optimum. A strength-based end-product acceptance criterion was developed using a CBR MEXE probe.

On the behaviour of Thanet Sand: an example of an uncemented natural sand

An extensive laboratory investigation was made of the mechanics of Thanet Sand, testing the soils from a number of locations and depths in the triaxial apparatus over a wide range of stress levels. Comparisons between tests on intact and reconstituted samples and between vertically and horizontally trimmed intact samples highlighted the effects of structure on the behaviour of this uncemented sand, in particular a significant effect of anisotropy. Two distinct substrata have previously been identified with different fines contents, and the key difference in their behaviour has been found here to be the location of their Critical State Line in the v:lnp′ plane, which has a significant effect on the engineering behaviour of the two substrata and can explain recent unusual observations of decreasing pile capacity with depth. Tests in which the glauconite content was removed from the sand showed that it did not affect its behaviour.

The impact of adverse geological conditions on the design and construction of the Thames Water Ring Main in Greater London, UK

Abstract The Thames Water Ring Main has been driven through the various Palaeogene deposits of London and the underlying Cretaceous Chalk. Much of the tunnel alignment was designed to keep within the London Clay Formation over the western half of the project, although discovery of a number of Quaternary scour hollow features, during the ground investigation, led to revisions in tunnel design. In addition, a scour feature was also intersected during tunnelling, necessitating changes to the tunnel lining and use of compressed air. Over much of the eastern half of the project, the tunnel alignment was unable to avoid the lower Palaeogene deposits of the Lambeth Group, and Thanet Sand Formation, as well as the underlying Chalk. These deposits were found to contain hazardous features, such as sand-filled channels, sub-artesian groundwater and hard ground, complicated further by geological faults along the route. Intersection with these features could have had serious implications for the health and safety and efficiency of tunnelling operations. These adverse geological conditions were avoided by changes to the alignment during design or by ground dewatering prior to construction. When intersection occurred, the open-faced machines used compressed air and lining changes to mitigate the risk. From 1990, the project used Earth Pressure Balance Machines (EPBMs) for the first time in the UK. These allowed better control of problematic ground and allowed the project to set an all-time productivity record.

Groundwater control for construction in the Lambeth Group

Excavations in the Lambeth Group often encounter groundwater problems. This is related to the variable nature of the Lambeth Group soils and the presence of permeable water-bearing layers of sand, silt and gravel, where groundwater inflows can lead to instability. The permeability of the water-bearing layers can vary within a wide range. The pore water pressure and associated piezometric head in each layer can be difficult to predict, as the piezometric profile may diverge from the hydrostatic, under the influence of underdrainage from the Chalk Group and Thanet Sand Formation, which forms the lower aquifer beneath the Lambeth Group. Stability of excavations can be improved by using groundwater control techniques to reduce pore water pressures in permeable layers. Suitable methods, including active and passive pressure relief and underdrainage are discussed, and case histories presented.

Dewatering the Thanet Beds in SE London: three case histories

Abstract The construction of the Jubilee Line Extension in southeast London required the construction of a number of deep excavations extending into the Thanet Beds. These Lower Tertiary strata are predominantly silty fine sands, and in order for the excavations to be carried out in the dry, dewatering was necessary. Three examples of excavations in the Thanet Beds are described in this paper, in each of which dewatering was attempted by pumping from the underlying Chalk to induce drainage of the Thanets. Although the three sites were only approximately 1 km apart, the performance of the dewatering schemes was different at each site. One excavation proved impossible to dewater by this method, whilst the other two, although successfully completed, demonstrate very clearly the extreme variations in the permeability of the Chalk and the difficulties that may arise therefrom.

Palynostratigraphy and depositional history of the Palaeocene Ormesby/Thanet depositional sequence set in southeastern England and its correlation with continental West Europe and the Lista Formation, North Sea

Analysis of palynofloras from eleven sections of the Late Palaeocene Thanet Sand and Ormesby Clay formations of southeastern England has enabled construction of a stratigraphy for a period of approximately 2 Myr, based upon eighteen palynofloral association sequences. This high-resolution stratigraphy has allowed the accurate recognition of the extent of depositional sequences in the region. Deposition of claystones was initiated in Norfolk after 58.5 Ma as a prograding series of five parasequences, with the onset of sedimentation in the majority of the southeastern England area resulting from a subsequent rise in relative sea level at around 58 Ma. Relative sea levels reached a maximum at 57.91 Ma, after which a period of condensed sedimentation ensued. This first maximum flooding surface initiated deposition in the far south of the area (Kent), and was succeeded by a distinct fall in relative sea level and subsequent retrogradation of sedimentary units. A major change in lithology and palynofloras is marked by the initiation of a further sequence at approximately 57.5 Ma, with a second maximum flooding surface occurring shortly afterwards, followed by prograding sedimentary units. The uppermost part of the Thanet Sand and Ormesby Clay formations is composed of two separate maximum flooding events, the uppermost of which is poorly preserved. The lack of any other depositional units between these events suggests the presence of a significant disconformity at this point. Comparison of the palynofloral association sequences and flooding events of southeastern England, with sections in Belgium, Denmark and with the Lista Formation in the North Sea, demonstrates a close affinity between these areas. The transgressive surface identified at the base of the Thanet Sand Formation in southeastern England is preserved as the shales immediately overlying the Balmoral tuffite of the Lista Formation, and as the base of the Orp Sands in Belgium and Holmehus Formation in Denmark. The subsequent record of relative sea level change in the south is mirrored in the Lista Formation, with the maximum flooding events being represented by shales and the intervening prograding sequences by siltstones and thick sands. This comparability of the record implies a similar regime of relative sea level change in the North Sea and southeastern England area throughout the deposition of the Lista/Ormesby/Thanet sediments, prior to the contrasting environments of Sele Formation-Lambeth Group sedimentation.

Chronostratigraphic framework for the Thanetian and lower Ypresian deposits of southern England

Abstract Magnetostratigraphic and palynomorph data are used to assess the timing and nature of the late Paleocene-earliest Eocene depositioanl sequences of SE England. Ormesby Clay Formation mudstones in east Norfolk are the oldest upper Paleocene deposits (C26r) of southern England. The base of the type Thanet Sand Formation (= start of the Thanetian Stage) is c. 0.65 million years younger (C26n). A subaerial erosion surface separates the Thanet-Ormesby package from the Lambeth Group sediments. The duration of the hiatus (>0.5 million years) separating the two units can be calculated from the magnetostratigraphic data; C25n is missing from the stratigraphic record across almost all of southern England. However, the Upnor Formation in central London contains a record of C25n. A hiatus of c. 0.4 million years separates the late Paleocene Lambeth Group from the early Eocene Harwich Formation. The Lambeth Group, Harwich Formation and lower London Clay Formation were all deposited during C24r. The start of Chron C24n.3n is positioned at the base of Division B of the London Clay Formation.

Tectonic controls on sequence development in the Palaeocene and earliest Eocene of southeast England: implications for North Sea stratigraphy

Abstract Depositional sequences in the Palaeocene and early Eocene of southern England are grouped into three unconformity-bounded composite sequences, corresponding to the Ormesby Clay and Thanet Sand formations, the Lambeth Group (including the Woolwich and Reading formations) and the Thames Group (including the Harwich and London Clay formations). A refined chronostratigraphical framework, coupled with a revised Palaeogene chronometry, reveals a clear relationship between long-term Palaeocene to early Eocene sea-level trends and radiometrically dated volcanic events in the North Atlantic Province. In gross terms, it is possible to relate the progressive Palaeocene uplift of NW Europe to the rise of the proto-Icelandic mantle plume beneath the continental crust of East Greenland, and the early Eocene subsidence of NW Europe to the transfer of the plume to the developing NE Atlantic mid-ocean ridge. However, both the sedimentary and volcanic record indicate that the uplift of NW Europe took place in three stages, expressed in the North Sea region as long-term regressive-transgressive facies cycles. The first uplift phase was associated with the onset of Hebridean volcanic activity and with a short-lived influx of coarse clastic sediments into the North Sea Basin (basal Ekofisk Formation). No sediment associated with this cycle is preserved in southern England. The second uplift phase was associated with the main period of Hebridean activity and led to substantial uplift of Scottish source areas. It was followed by regional subsidence and transgression of the basin margins (Ormesby-Thanet composite sequence). The third uplift phase was associated with the onset of rifting and volcanism along the North Atlantic rift zone. Eastward tilting initially led to sedimentation in eastern and southern England (Lambeth composite sequence), but continued uplift of southern and western Britain eventually restricted sedimentation to the central and northern parts of the North Sea basin, with major progradation of the Dornoch delta complex taking place along the eastern margin of the Scottish land mass. This period marked the maximum isolation of the North Sea Basin, with reduced salinities being reflected in a near-absence of marine fauna and a highly restricted microflora. The third uplift phase is believed to mark the culmination of plume-related tectonism in NW Europe and was associated with a resurgence of volcanic activity in the British Tertiary Igneous Province, including intrusion of the Cleveland-Blyth-Acklington dyke system along the uplifted Sole Pit inversion zone. A sharp reduction in intrabasinal activity, coupled with the initiation of a long period of regional subsidence (Thames composite sequence), is interpreted as representing thermal subsidence following the onset of seafloor spreading between Greenland and Scotland. Oceanic crust generation was initially subaerial and was associated with intense, largely basaltic, pyroclastic activity that affected the whole of NW Europe (Balder Formation and equivalent tuffs). The cause of the episodic nature of the plume-related uplift is uncertain. It appears that the mechanics and configuration of plume emplacement were either intrinsically more complex than previously recognized, or were influenced by changes in the regional stress pattern within the NW European crust.

Enfield-Haringey artificial recharge scheme

Artificial recharge was carried out experimentally in north London by the Water Resources Board and the Metropolitan Water Board between 1953 and 1970(Boniface 1959). These trials were successful, although only small volumes of water were recharged. Research by Thames Water Authority continued between 1975 and 1984 at a larger scale in the north London area (Flavin & Hawnt 1979; Flavin & Joseph 1983). Thames Water Utilities drilled and tested 14 new production boreholes for the Enfield-Haringey Scheme along the course of the New River in north London (Fig. l, opposite). These new boreholes, together with nine existing sites, are designed to increase the strategic groundwater resources of north London by 90 Ml/d by artificially recharging the Chalk and Thanet Sands aquifer beneath London (O'Shea 1994). During an average year, demand for water is often lower than that available from the Coppermills Water Treatment Works and between 10 and 20 M1/d of this excess fully treated water can be gravity recharged to the aquifer. This will be by low-rate, trickle recharge ensuring that the volume of water stored in the aquifer is sufficient to sustain a prolonged drought abstraction for up to 200 days. When demand for water is high, as in drought conditions, groundwater can be pumped from the aquifer, using the same boreholes, directly into the New River which acts as an aqueduct taking the water back to Coppermills, via the East Reservoir at Stoke Newington for treatment and supply. The scheme will be used strategically in times of

New information on the age and sequence stratigraphy of the type Thanetian of southeast England

The drilling of a cored borehole at Bradwell, Essex, has provided an opportunity to examine an unweathered and almost continuous section through equivalents of the Thanet Formation stratotype sections of northeast Kent. Calcareous nannoplankton and magnetostratigraphic analysis indicate an age range from NP6 (Chron 26N) to NP8 (Chron 25R), similar to that reported from the stratotype sections. However, whereas the base of the type Thanetian has previously been dated only as undifferentiated NP6/ NP7, the upward incoming of Sphenolithus anarrhopus in the Bradwell section provides a strong indica­ tion that both zones are represented. The association of the basal sediments with Chron 26N confirms that rhe base of the type Thanetian lies within the upper part of NP6. The relative thinness of the section attributed to NP7 in the Bradwell section appears to result from non-sequence and condensed sedimentation associated with a sequence boundary that occurs near the middle of the formation. This sequence boundary is equated with the base of the Reculver Silts in the stratotype section and with the base of the Lower Landenian in Belgium.

Magnetostratigraphy of the upper paleocene and lowermost eocene of SE England

Today, the upper Paleocene of SE England is one of the most intensively studied pre‐Quaternary intervals anywhere. Until recently, knowledge of the magnetostratigraphy of these deposits was restricted to (1) the Thanet Formation stratotype, (2) a borehole core from Ormesby, Norfolk, and (3) outcrops of the Reading Formation and lower part of the London Clay Formation on the Isle of Wight (Figs. 1 and 2). The oldest Paleocene sediments (Chron C26r) were reported from the Ormesby Clay Fm in the Ormesby borehole (Cox et al. 1985). The Thanet Fm was deposited during Chrons C26n and C25r, whilst the Lambeth Group, Hales Clay, Harwich Fm, and lower London Clay Fm were all deposited during Chron C24r(HailwoodT Aubry et al. 1986). (The nomenclature of the upper Paleocene of southern England is currently under revision; Ellison et al. pers. comm. Their new scheme is illustrated in Fig. 3.) Aubry et al. (1986) concluded that the absence of arecord of Chron C25n from the upper Paleocene of SE England i...

A revision of the lithostratigraphical classification of the early Palaeogene strata of the London Basin and East Anglia

Current multidisciplinary research on the Palaeogene strata in the London Basin and East Anglia has been given impetus by the drilling of several key boreholes for stratigraphical purposes, and for major construction projects in the London area. Improved rotary coring over the past five years or so has resulted in virtually complete recovery of Palaeogene successions. These cores have formed the basis for building on established research in order to provide a formal lithostratigraphical framework appropriate for academic and practical use. A new formation, the Ormesby Clay Formation, is introduced for argillaceous sediments in East Anglia equivalent to the Thanet Sand Formation of the London Basin. The term Lambeth Group is introduced, replacing the 'Woolwich and Reading Beds' and thereby allowing the beds to be defined in formations. Thus the former ‘Bottom Bed’ is named Upnor Formation and the overlying strata are divided into a Woolwich Formation and a Reading Formation. The dominantly arenaceous and pebbly beds between the Lambeth Group and London Clay Formation, including strata traditionally known as the Oldhaven Beds, Blackheath Beds, and ‘London Clay basement bed’ and the ash-bearing beds in the northeast of the London Basin and East Anglia, are grouped together as the Harwich Formation.