London Clay Research Articles

Early Eocene fossil illuminates the ancestral (diurnal) ecomorphology of owls and documents a mosaic evolution of the strigiform body plan

We describe a partial skeleton of a fossil owl (Strigiformes) from the early Eocene London Clay of Walton‐on‐the‐Naze (Essex, UK). The holotype ofYpresiglaux michaeldanielsi, gen. et sp. nov. is one of the most complete specimens of a Palaeogene owl and elucidates the poorly known ecomorphology of stem group Strigiformes. Whereas most of the postcranial bones show the characteristic strigiform morphology, the new species exhibits plesiomorphic features of the skull and cervical vertebrae that differ distinctly from extant owls. A well‐developed supraorbital process of the lacrimal bone suggests that the eyes were not as greatly enlarged and forward‐facing as in extant owls. A plesiomorphic quadrate morphology indicates differences in the otic region, and a proportionally longer axis suggests that the fossil species was not able to rotate its head to the degree found in crown group Strigiformes. Therefore, the fossil documents a mosaic evolution of the strigiform body plan, with owls developing raptorial adaptations before specializations of the visual and acoustic systems evolved. Because the latter relate to a crespuscular or nocturnal activity pattern, we hypothesize thatYpresiglauxwas diurnal. Nocturnality in owls may have evolved in response to the emergence of evolutionary opportunities, which enabled owls to exploit new ecological niches, or owls may have been driven into nocturnal habits by ecological competition.

Oldest fossil loon documents a pronounced ecomorphological shift in the evolution of gaviiform birds

Abstract We describe a stem group representative of Gaviiformes (loons or divers) from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). The holotype of Nasidytes ypresianus gen. et sp. nov. is a partial skeleton including the mandible and all major limb bones. The new species is the oldest unambiguously identified loon and the most substantial Palaeogene fossil record of Gaviiformes. The mandible of Nasidytes is proportionally wider than that of extant loons and resembles that of extant coots (Fulica spp.), which indicates that the new taxon was less piscivorous than crown group Gaviiformes. Hypotarsus morphology suggests that N. ypresianus is the sister taxon of a clade including all other Cenozoic fossil loons and crown group Gaviiformes. According to its plesiomorphic leg morphology, and unlike extant loons, the new species was not a specialized pursuit predator of fishes. The evolution of advanced diving capabilities in the stem lineage of Gaviiformes is likely to have been correlated with an increased piscivory of loons, and the skeletal morphology of Nasidytes conforms to multiple independent origins of specialized piscivory and a highly aquatic ecology in the waterbird clade (Aequornithes).

Effects of fibre additions on the tensile strength and crack behaviour of unsaturated clay

Desiccation cracking in clay soils is a combined mechanical and hydraulic problem and such soils can be improved by various methods including reinforcement with fibres. The relationships between tensile strength, cracking resistance and water-retention properties of fibre-reinforced fine-grained soils lack coverage in the literature to date. In this study, these three properties are evaluated and connected by way of a series of tensile strength and desiccation cracking tests on fibre-reinforced London clay. The results confirm that increased fibre addition delays the occurrence of peak stress and changes failure behaviour from brittle to ductile. The tensile strength increment gets higher as water content decreases, and reaches a maximum value of 460 kPa when the water content is 12%. The crack intensity factor reduces from 7.20% to 0.89% when 12 mm long fibre is used at a ratio of 0.9%. Fibre reinforcement also changes the crack development pattern by reducing the size of large cracks and increasing the proportion of small individual cracks. However, the presence of fibres was not observed to change the water-retention properties of the soil, indicating that the tensile improvement comes from the pull-out resistance of the fibres rather than suction changes.

Numerical Simulation of a Tunnel Built in London Clay Using the MIT-E3 Model

Abstract The prediction of ground surface troughs due to underground tunneling is an important problem in geotechnical design. After its calibration based on recent and last studies on London Clays...

Mastixioid fruits (Cornales) from the early Eocene London Clay Flora: morphology, anatomy and nomenclatural revision

Following on the seminal works of Reid and Chandler in 1933 and Chandler in 1961, morphology and anatomy of fossil mastixioid fruits from the early Eocene London Clay of southern England were reanalyzed with the benefit of new methods in comparison with extant genera of Mastixiaceae and with other fossil representatives from Europe and North America. The species named Mastixia cantiensis E.Reid et M.Chandler was based on a heterogeneous assemblage of specimens, all representing Mastixiaceae, some of which truly represent Mastixia whilst others correspond to Diplopanax and Mastixiopsis The holotype of M. cantiensis E.Reid et M.Chandler corresponds to extant Diplopanax rather than Mastixia. Therefore, this species is moved out of Mastixia and is treated as Diplopanax cacaoides (Zenker) comb. nov. Nine species of mastixioid fruits are currently recognized in the London Clay flora: Mastixia parva E.Reid et M.Chandler, M. cf. oregonensis (R.A.Scott) Tiffney et Haggard, Diplopanax cacaoides, Tectocarya grandis (E.Reid et M.Chandler) comb. nov., Mastixiopsis nyssoides Kirchh., Exbeckettia mastixioides (E.Reid et M.Chandler) gen. et comb. nov., Lanfrancia subglobosa E.Reid et M.Chandler, Portnallia bognorensis M.Chandler, and Langtonia bisulcata E.Reid et M.Chandler. These include the oldest known representatives of the genera Diplopanax, Tectocarya and Mastixiopsis and contribute to our understanding of the former morphological diversity and palaeobiogeography of the Mastixiaceae.

An experimental study into the ultimate capacity of an ‘impression’ pile in clay

The ultimate capacity of a novel type of piled foundation called an ‘impression’ pile has been investigated using centrifuge modelling techniques. The name derives from the small discrete impressions created in the side walls of a bored cast in situ pile to increase the soil/pile friction such that the impressions form nodules on the shaft of the concreted pile. The technology is suitable for bored piles in overconsolidated clay, such as London Clay. The experiments explored the influence of geometrical parameters such as the vertical spacing of the impressions, their number at each level and their shape. The data show a consistent increase in pile capacity of 40% when the impressions extend over 85% of the pile length. The ultimate capacity of the pile is primarily affected by the length of the pile which is impressed, the number of nodules at a given cross-section and the spacing of the nodules in the vertical direction, as long as this is greater than a threshold value. According to the experimental evidence, a block failure occurs for a spacing lower than this threshold value. Plastic failure mechanisms for the impression pile were established. These were used successfully to calculate the ultimate capacity of the impression piles tested with an error of less than 10%.

New fossils from the London Clay show that the Eocene Masillaraptoridae are stem group representatives of falcons (Aves, Falconiformes)

ABSTRACT The Eocene taxon Masillaraptoridae includes long-legged, raptorial birds, the phylogenetic affinities of which are poorly resolved. Here, fossils from the London Clay of Walton-on-the-Naze (Essex, U.K.) are described, which corroborate the hypothesis that masillaraptorids are stem group representatives of the Falconiformes (falcons). Two partial skeletons are assigned to a new genus and species, Danielsraptor phorusrhacoides, gen. et sp. nov., whereas a smaller species closely resembles Masillaraptor parvunguis from the German fossil site Messel. The new fossils show previously unrecognized derived characters shared by masillaraptorids and falconiform birds, and a phylogenetic analysis also supported a sister group relationship between the Masillaraptoridae and the Falconiformes. By contrast, the long and deep beak of masillaraptorids is remarkably similar to that of the cariamiform Phorusrhacidae and the tarsometatarsus also shows a resemblance to that of some Cariamiformes. The similarities between masillaraptorids and the Cariamiformes are notable, because most sequence-based analyses show the Falconiformes and Cariamiformes to be closely related, and a few studies even suggest a sister group relationship between both taxa. These similarities may be plesiomorphic for a more inclusive clade containing falconiforms and cariamiforms, but it is also possible that masillaraptorids represent a direct evolutionary link between the Falconiformes and Cariamiformes.

Intertidal cohesive foreshores: Erosion rates and processes illustrated by a shore platform at Warden Point, Kent, UK

Data are presented from a 9-year monitoring period, using a Traversing Erosion Beam (TEB), of erosional lowering of an inter-tidal shore platform developed in cohesive London Clay at Warden Point, Isle of Sheppey, Kent, UK. Over the monitoring period, average lowering decreased from >30 mm a−1 at 30 m down-platform from the MHW line to <15 mm a−1 at 75 m down-platform and <8.0 mm a−1 at the lowest measured point 120 m seaward of MHW, giving an overall average 17–18.0 mm a−1 across the measured section of platform. Differences in lowering rates recorded between the three down-platform measuring stations were statistically significant, as were differences between average annual rates and between seasons. It is suggested that these differences in recorded rates of lowering result from variation in the relative importance over space and time of sub-aerial versus marine processes of weathering and erosion. Adding the local relative sea-level rise of 2.23–2.36 mm a−1 the average annual rise in mean water level over the platform surface was ~20 mm a−1 and at the cliff-platform junction >32 mm a−1. Backed by cliffs 48 m tall retreating at a long-term average > 1.0 m a−1 the maximum contribution of platform lowering to the long-term erosional budget of the study site was ~7.4%.The significant differences in recorded annual and seasonal erosion rates indicate that extrapolation of average rates based on data collected for two years or less on such rapidly eroding platforms should be treated with caution because they may not be representative of the longer-term average rate either for the entire platform or for individual monitoring points.

Design method for the ‘impression pile’

Urban development in congested cities requires a better exploitation of the available surface, leading to taller structures. These buildings are usually founded on piles that have to be increased in dimension to accommodate the larger loads, resulting in increases in both the cost and the carbon dioxide footprint of the pile foundation. An alternative option is to improve pile performance by enhancing the shaft capacity, which is commonly the most important factor in determining the ultimate capacity of a pile constructed in a clay soil subjected to axial load. For piles in stiff clays such as London Clay, the soil–pile friction may be increased by profiling the side walls of a bored cast in situ pile with small discrete ‘impressions’ such that the latter form nodules on the shaft of the concreted pile. Centrifuge tests carried out at City, University of London, and field trials undertaken by Keltbray Piling across different London sites showed an increase in the shaft capacity of around 40%. In this work, a simple design method based on experimental evidence and an existing plastic failure mechanism was derived for ‘impression’ piles. The proposed method shows good agreement with data and enables a direct prediction of the increase in capacity for future designs.

A partial skeleton of Septencoracias from the early Eocene London Clay reveals derived features of bee-eaters (Meropidae) in a putative stem group roller (Aves, Coracii)

A partial skeleton of the putative stem group roller Septencoracias is described from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). With an age of about 55 million years, the bones represent one of the earliest fossil records of a coraciiform bird. The new fossil reveals that the proximal pedal phalanges of the three anterior toes of Septencoracias exhibit markedly widened distal ends. This distinctive trait is not found in other representatives of the Coracii, but occurs in the Meropidae (bee-eaters). The quadrate likewise exhibit a derived characteristic of the Meropidae, and the beak is narrower than in rollers. These previously unnoticed features are of particular interest, because the Meropidae result as the sister taxon of the Coracii in sequence-based analyses. Calibrated molecular data suggest that the divergence between the Coracii and the Meropidae occurred at 55.6 Ma, with the new fossil being only slightly younger than this date. However, phylogenetic analyses recovered Septencoracias within the Coracii, so that the derived features shared with the Meropidae most likely are either plesiomorphic and were lost in the Coracii, or they represent parallelisms that evolved convergently in Septencoracias and the Meropidae. In any case, these traits suggest that Septencoracias differed from extant rollers in its ecological preferences and foraging mode.

An early Eocene fossil from the British London Clay elucidates the evolutionary history of the enigmatic Archaeotrogonidae (Aves, Strisores)

AbstractArchaeotrogons have long been known from late Eocene and Oligocene localities in France, where limb bones are abundantly represented. The phylogenetic affinities of these birds, however, have remained elusive. Although archaeotrogons are now considered to be representatives of the Strisores, the clade including ‘caprimulgiform’ and apodiform birds, their exact position in this clade is unresolved. Here, a partial skeleton of a new species of the Archaeotrogonidae is described from the early Eocene London Clay of Walton‐on‐the‐Naze (Essex, UK). In addition, a new specimen of the archaeotrogon Hassiavis from the latest early or earliest middle Eocene of the Messel fossil site in Germany is reported, which is the best preserved skeleton of this species. Archaeodromus anglicus gen. et sp. nov. from the London Clay is the earliest archaeotrogon known to date, and the holotype shows previously unknown skeletal characteristics of archaeotrogons that bear on the phylogenetic affinities of these birds. The quadrate in particular exhibits a distinctive morphology and shows derived morphological characteristics of the Strisores. Although the primary analysis did not conclusively resolve the affinities of archaeotrogons, analyses constrained to a molecular scaffold resulted in a sister group relationship to the Caprimulgidae (nightjars). The evolutionary history of this most species‐rich group of nocturnal Strisores is virtually unknown, and recognition of archaeotrogons as archaic stem group representatives of the Caprimulgidae would fill a striking gap in the fossil record.

Effect of initial stiffness on the behaviour of two geotechnical structures: An embankment and a tunnel

This work analyses the effect of the change in the initial stiffness on the behaviour of two geotechnical structures performed on/in overconsolidated clays: an embankment built on Boston blue clay and a tunnel dug in London clay. The numerical predictions are performed with the MIT-E3 model, which reproduces the small strain nonlinearity and hysteretic stress–strain response observed in unload-reload cycles. Firstly, the performance of the constitutive model to replicate an unload-reload cycle of a consolidation test is validated. The initial stiffness is varied by changing the κo parameter of the MIT-E3 model. Thus, several numerical predictions of the two geotechnical structures, performed for different κo values are compared with each other and field measurements, in terms of settlement and horizontal displacements. The results show that the variation in initial stiffness has a greater effect on the behaviour of the tunnel than the embankment. In fact, in the case of the tunnel, the majority of the stress paths occur inside the yield surface, where the stiffness is the key parameter. On the other hand, for the embankment, the yield occurs in the major part of the domain, therefore the stiffness effect is less significant.

A diverse crinoid fauna (Echinodermata, Crinoidea) from the Lower Eocene of the Gulf of Languedoc (Corbières, Aude, southern France)

Detailed studies of the middle Ilerdian (lower Ypresian) blue marls of the Gulf of Languedoc (Corbières, Aude, France), belonging to the north Pyrenean foreland basin, have revealed a more abundant and diverse crinoid fauna than previously documented from the Lower Eocene. Here we describe five species of stalked crinoids in the family Rhizocrinidae (Cherbonniericrinus requiensis n. sp., ?Democrinus elongatus, Globulocrinus amphoraformis n. gen., n. sp., Pseudoconocrinus doncieuxi and P. lavadensis n. sp.), one barnacle-like species in the stalkless family Holopodidae (Holopus plaziati n. sp.) and a single feather star in the family Conometridae (Amphorometra atacica). Several sites have yielded brachials and rhizoids in addition to abundant aboral cups and columnals indicating in situ fossilisation of the dissociated skeletal elements. P. lavadensis n. sp. and ?D. elongatus have been collected only from outcrops located in the upper part of the middle blue marls, while P. doncieuxi predominates, with a wide range of morphological variation, in the lower blue marls. The fossil assemblage at the locality of Réqui near Montlaur differs from the others in the smaller size of most individuals and the presence of H. plaziati n. sp., C. requiensis n. sp., G. amphoraformis n. gen., n. sp., and P. doncieuxi suboblongus n. subsp. This particular association with high juvenile mortality corresponds to an unstable environment with mixed substrates (muddy and rocky). The crinoid fauna of the Corbières appears to be the most diverse of Early Eocene age known to date. With the fauna of the London Clay, a boreal formation of the same age, it shares the presence of the genera Democrinus and Amphorometra in an open-sea environment. A comparison with extant faunas allows the depth of deposition at the Ypresian sites in the Gulf of Languedoc to be estimated between from 100 and 140 meters.

A partial skeleton of a new species of Tynskya Mayr, 2000 (Aves, Messelasturidae) from the London Clay highlights the osteological distinctness of a poorly known early Eocene \u201cowl/parrot mosaic\u201d

Tynskya eocaena is an early Eocene bird with a raptor-like skull and semi-zygodactyl feet, whose description is based on a skeleton from the North American Green River Formation. In the present study, three-dimensionally preserved bones of a new species of Tynskya, T. waltonensis, are reported from the London Clay of Walton-on-the-Naze (Essex, UK). The fossils belong to a single individual and provide new insights into the skeletal morphology of messelasturids. In particular, they reveal unusual vertebral specializations, with the cervical vertebrae having concave rather than saddle-shaped caudal articulation facets and the caudalmost thoracic vertebra being platycoelous (flat articular surfaces). The very deep mandible and a derived morphology of the ungual phalanges support a sister group relationship between Tynskya and the taxon Messelastur (Messelasturidae). Phylogenetic analyses of an emended data matrix did not conclusively resolve the higher-level affinities of messelasturids and the closely related halcyornithids, with both taxa sharing derived characters with only distantly related extant taxa (Accipitriformes, Strigiformes, Falconiformes, and Psittaciformes). An analysis that was constrained to a molecular scaffold, however, recovered messelasturids as the sister taxon of a clade including psittaciform and passeriform birds. The derived morphologies of the mandible and cervical vertebrae suggest specialized feeding adaptations of Tynskya, and messelasturids may have exploited a feeding niche, which is no longer available to extant birds.

Innovative monitoring of the response of a heritage masonry building to nearby tunnelling in London Clay

Heritage masonry structures require detailed monitoring during nearby underground construction, to address the concerns of building owners and mitigate uncertainties relating to the soil–structure system. This paper discusses innovative displacement and strain monitoring of a listed masonry church undergoing ground movements due to nearby tunnelling in London Clay. In addition to conventional surveying and tilt monitoring, laser scan displacement monitoring and fibre optic strain sensing was conducted. Prior to construction, point clouds of the structure were used to map pre-existing geometric distortions in the structure. During construction, detailed monitoring of displacements and strains was conducted across the building facades and the tower. The same techniques were also used to monitor the painted dome of the church where conventional displacement monitoring was not feasible. With a focus on the new engineering insight provided by the innovative monitoring techniques, the impact of the underground construction activities on the church is discussed in this paper. The proposed sensing techniques provide new data on the influence of pre-existing damage and tunnel advance on soil–structure interaction.

Numerical investigation of the performance of engineered barriers in reducing flood risk

In this paper, 2-dimensional, hydro-mechanically coupled finite element analyses are performed to assess the performance of an engineered barrier aimed at reducing flood risk in urban environments. The barrier consists of an unsaturated compacted soil layer and a drainage layer of a coarse granular material, constructed on top of the natural soil, in this case London clay. The barrier is vegetated so that its water storage capacity is renewed after each rainfall event. Sophisticated boundary conditions are used to simulate the effect of precipitation and evapotranspiration. The rainfall water infiltration and the initiation of water run-off during intense precipitation events are simulated. The effect of the hydraulic properties of the unsaturated soil layer on the performance of the system is investigated by means of parametric analyses. The effect of precipitation rate and geometry of the barrier is also discussed. Design recommendations for the properties of the compacted layer and the dimensions of the system are given at the end of the paper.

Investigation of tunnel movement of the Thameslink tunnels below site S3 of King’s cross zone development

ABSTRACT Site S3 of the King’s Cross Development Zone is located in Central London to the North of King’s Cross Station. The site directly overlies the 11 m deep Thameslink twin-rail tunnels. The excavation of a rotary core borehole on site led to tunnel inward movement recorded by in-tunnel prism arrays. Live monitoring data has been used to investigate and determine the causal link between borehole RC1 and this movement. The borehole excavation lost excessive amounts of fluid flush into the London Clay. The interaction between flush fluid and soil is numerically investigated in this paper with an investigation into the numerical simulation of the physical excavation of the borehole itself. The aim of this research work is to investigate the mechanisms of movement that may have resulted in the tunnel deformation while numerical analysing the construction of the borehole in stages. Using a 2D plane strain model, the HSS (Hardening Soil with small strain) constitutive model has been utilised in order to recreate the stress history within the London Clay.

A remarkably complete skeleton from the London Clay provides insights into the morphology and diversity of early Eocene zygodactyl near-passerine birds

Recognition of the zygodactyl parrots (Psittaciformes) as the closest extant relatives of passerines (Passeriformes) shed new light on the affinities of various Paleogene birds with a zygodactyl foot, which are now considered to be stem group representatives of the Passeriformes. However, most of these taxa are known only from compression fossils, which allow the recognition of a limited number of osteological details. Here, an exceptionally complete skeleton of a new species is described from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). Parapsittacopes bergdahli gen. et sp. nov. resembles Psittacopes lepidus (Psittacopedidae) from the Messel fossil site in Germany, from which it is distinguished in beak shape and several postcranial characters. Even though the phylogenetic analyses yielded conflicting tree topologies under different settings, all of the resultant phylogenies supported close affinities between Parapsittacopes, Psittacopes and the Eocene taxa Pumiliornis and Morsoravis. The three-dimensionally preserved bones of the P. bergdahli holotype exhibit subtle osteological characteristics of passeriform birds, which have not been reported from previously known fossils of closely related zygodactyl stem group taxa. The broad beak and low mandibular rami indicate that P. bergdahli may have caught insects by sallying flights from perches, and the new species therefore adds another feeding adaptation to the already diverse array of zygodactyl stem group Passeriformes with disparate feeding ecologies. http://zoobank.org/urn:lsid:zoobank.org:pub:FD0E9DC4-961F-4460-9466-164E5EB42E4E

Forecasting the long-term deterioration of a cut slope in high-plasticity clay using a numerical model

This paper details development of a numerical modelling approach that has been employed to forecast the long-term performance of a cut slope formed in high plasticity clay. It links hydrological and mechanical behaviour in a coupled saturated and unsaturated model. This is used to investigate the influence of combined dissipation of excavation-generated excess pore water pressures and seasonal weather-driven near-surface cyclic pore water pressures. Deterioration of slope performance is defined in terms of both slope deformations (i.e. service) and factor of safety against shear failure (i.e. safety). Uniquely, the modelling approach has been validated using 16 years of measured pore water pressure data from multiple locations in a London Clay cut slope. Slope deterioration was shown to be a function of both construction-induced pore water pressure dissipation and seasonal weather-driven pore water pressure cycles. These lead to both transient and permanent changes in factor of safety due to effective stress variation and mobilisation of post-peak strength reduction over time, respectively, ultimately causing shallow first-time progressive failure. It is demonstrated that this long-term (90 year) deterioration in slope performance is governed by the hydrological processes in the weathered near surface soil zone that forms following slope excavation.

Análise simplificada de recalques de um radier estaqueado em Argila de Londres

O trabalho analisa a evolução de recalques do edifício Hyde Park Cavalry Barracks, em Londres, partindo de simulações numéricas axissimétricas em elementos finitos. A edificação apresenta uma fundação do tipo radier estaqueado, construído sobre uma espessa camada de argila, representada pelo modelo constitutivo Cam-Clay modificado. Dados da obra e parâmetros do solo foram obtidos através dos trabalhos de Hooper (1973) e Gasparre (2005). A sequência de etapas construtivas da fundação foi considerada e os recalques previstos foram comparados com dados de monitoramento e com as previsões numéricas de Hooper (1973), Hain e Lee (1978), Sales et al. (2010) e Bernardes et al. (2019). A análise proposta difere daquelas publicadas anteriormente por não utilizar parâmetros do solo retroanalisados dos dados de monitoramento de recalques da edificação. Os resultados indicam razoável concordância entre os valores previstos e medidos, ressaltando a escolha adequada do modelo constitutivo Cam-Clay modificado e a importância da definição da inclinação da reta de recompressão na análise de argilas muito sobreadensadas.