Boulder Clay Research Articles

The degree of aeolization of Quaternary deposits in Poland as a tool for stratigraphic interpretation

The aim of the study was to test if it is possible to distinguish Quaternary sediments bearing evidence of the impact of aeolian processes during their accumulation. It was also important to verify if distinguishing of these series would be useful in the accurate determination of stratigraphic position, determined previously using lithological, petrographic and palynological methods. The sediments were sampled from five boreholes, reaching the Tertiary, and from six exposures, all from Central, East and North Poland. The following features were taken to indicate a significant role of aeolian processes during sediment accumulation: high percentage of quartz grains (0.8–1.0 mm) in the sand fraction characterized by distinct rounding and frosting; high quartz content and low feldspar content (0.8–1.0 mm), and the composition of the heavy minerals fraction (0.1–0.2 mm). Garnets are particularly resistant to mechanical abrasion, whereas micaeous minerals are susceptible to winnowing. This spectrum of textural features, that indicates the effects of intensive aeolian processes, was termed “deposit aeolization”. Sediment aeolization may be observed in sediments of various origin: aeolian, fluvial or lacustrine. The study proved that the highest degree of aeolization occurred in alluvial (fluvioperiglacial) sediments accumulated before the first Riss (Odra) glaciation and in aeolian and fluvial sediments during the decline of Weichselian glaciation. Sediment aeolization is a valuable supplement to previous methods to indicate the stratigraphic position. The degree of aeolization allows the delimitation of the boundary between the Quaternary and Tertiary; it identifies glacitectonic and tectonic deformations; and it distinguishes fluvial and fluvioperiglacial sheets from fluvioglacial sheets. It is useful in estimating the length and intensity of aeolian processes; it adds to the interpretation of climatic conditions at the time of deposition and defines the limits of interglacial sheets within sandy sediments (30 to about 100 m thick) separating boulder clay units.

Observations on permafrost ground thermal regimes from Antarctica and the Italian Alps, and their relevance to global climate change

Active-layer monitoring and the permafrost thermal regime are key indicators of climate change. The results of 3 years (1997–1999) of active-layer monitoring at one high-mountain site (La Foppa, 46°28′42″N; 10°11′18″E, 2670 m a.s.l.) and at one Antarctic site (Boulder Clay, 74°44′45″S; 164°01′17″E, 205 m a.s.l) are presented. The initial analysis of a thermal profile in a borehole (100.3 m deep) within mountain permafrost at Stelvio (3000 m a.s.l., 46°30′59″N; 10°28′35″E) is also presented. At the alpine site, the active-layer thickness variations (between 193 and 229 cm) relate to both the snow cover and to the air temperature changes. By contrast, at the Antarctic site, there is a strong direct linkage only between air temperature fluctuations and active-layer variations. At the alpine (La Foppa) site, the relationship between climate and active-layer thickness is complicated by thermal offset that is almost negligible at both the Stelvio and Antarctic sites. The permafrost temperature profile at Stelvio site contains a climate signal suitable for paleoclimate reconstruction. The permafrost at this site has a mean annual ground surface temperature (MAGST) of −1.9 °C (during 1998/1999), an active layer of about 2.5 m thick and a total thickness of ∼200 m. Analysis of the MAGST history, obtained by applying a simple heat conduction one-dimensional model, revealed the occurrence of a cold period from 1820 to 1940 followed by a warming period until 1978. Since the beginning of the 1980s, temperature dropped (less than 2 °C) until the middle 1990s, when a new period of warming started. All these climatic changes fit well with the glacial fluctuations in the area and with other paleoclimatic information derived from different proxy data.

Influence of preparation techniques on the index properties of clay

Liquid limit (LL) and plastic limit (PL) are frequently used as indicators of the behaviour of fine-grained materials. These parameters are a prerequisite in every geotechnical investigation. Careful and consistent material preparation is a key component in the laboratory procedures adopted to determine the LL and PL. In preparing samples for such tests, various techniques are used in practice, and this paper examines the influence of these techniques on the actual magnitude of LL and PL measured. The index properties of a glaciolacustrine deposit, locally known as Belfast Upper Boulder Clay, which was laid down in glacial Lake Belfast, are examined. The index properties were determined on samples of the material prepared in different ways, including drying the material at two different temperatures (40°C and 110°C), crushing the dried material from coarse granular to fine granular form by adopting varying degrees of crushing effort, and mixing the dry material with both deionised water and tap water. The results indicate that the crushing procedure has a significant influence on particle size distribution and a consequential effect on the LL and PL. Pore water chemistry and the drying procedure also have a measurable influence on the magnitude of LL and PL.

Prehistoric burial and ritual, in southwest Ireland

Archaeological monitoring of the construction of the N21 road improvements, Co. Kerry, Ireland, in 1999 uncovered four sub-circular features in the townland of Rockfield (FIGURE 1).The central feature revealed itself to be small pit containing a cremation burial. The bones in this shallow pit had been subjected to intense heat, though the boulder clay beneath was unburnt. Radiocarbon (calibrated σ2) dating showed that this cremation dated from 1440–1140 BC, the date being firmly placed in the Irish Bronze Age. The total weight of the cremation was 29 g. The general size of the bone fragments recovered was very small with 72.4% being less than 5 mm in size. This severely limited the osteological analysis. At least some of the fragments, particularly some of the long bone pieces appeared to be human. On the basis of size, the cremation represents at least one adult. The uniform chalky white appearance of the bones recovered indicated that the individual was very well cremated and was probably processed by crushing or pounding of the bones after cremation.

AVO investigations of shallow marine sediments

Amplitude‐variation‐with‐offset (AVO) analysis is based on the Zoeppritz equations, which enable the computation of reflection and transmission coefficients as a function of offset or angle of incidence. High‐frequency (up to 700 Hz) AVO studies, presented here, have been used to determine the physical properties of sediments in a shallow marine environment (20 m water depth). The properties that can be constrained are P‐ and S‐wave velocities, bulk density and acoustic attenuation. The use of higher frequencies requires special analysis including careful geometry and source and receiver directivity corrections. In the past, marine sediments have been modelled as elastic materials. However, viscoelastic models which include absorption are more realistic. At angles of incidence greater than 40°, AVO functions derived from viscoelastic models differ from those with purely elastic properties in the absence of a critical angle of incidence. The influence of S‐wave velocity on the reflection coefficient is small (especially for low S‐wave velocities encountered at the sea‐floor). Thus, it is difficult to extract the S‐wave parameter from AVO trends. On the other hand, P‐wave velocity and density show a considerably stronger effect. Attenuation (described by the quality factor Q) influences the reflection coefficient but could not be determined uniquely from the AVO functions. In order to measure the reflection coefficient in a seismogram, the amplitudes of the direct wave and the sea‐floor reflection in a common‐midpoint (CMP) gather are determined and corrected for spherical divergence as well as source and streamer directivity. At CMP locations showing the different AVO characteristics of a mud and a boulder clay, the sediment physical properties are determined by using a sequential‐quadratic‐programming (SQP) inversion technique. The inverted sediment physical properties for the mud are: P‐wave velocity α=1450±25 m/s, S‐wave velocity β=90±35 m/s, density ρ=1220±45 kg/m3, quality factor for P‐wave QP=15±200, quality factor for S‐wave QS=10±30. The inverted sediment physical properties for the boulder clay are: α=1620±45 m/s,β=360±200 m/s,ρ=1380±85 kg/m3,QP=790±660,QS=25±10.

The effect of anisotropic elasticity on the yielding characteristics of overconsolidated natural clay

Quantitative application of elastoplastic theory to the yielding behaviour of natural soils has always been uncertain. Part of the reason is that the theory was developed for reconstituted materials with isotropic structure, in contrast to natural soils that are usually anisotropic. The approach considered in this study assumes that pre-yielding behaviour is governed by the theory of linear anisotropic elasticity and that yield loci in the mean effective stress ( p') – deviator stress (q) plane are aligned approximately along the coefficient of earth pressure (K0) line. The assumption of a rotated yield locus associated with anisotropic elastic behaviour within the state boundary surface indicates that the elastic wall within the state boundary surface is inclined. The form of the state boundary surface has been determined mathematically in terms of anisotropic elastic and Cam-Clay soil parameters. Stress path tests were conducted on samples of Belfast Upper Boulder Clay removed from a depth of 28 m below ground surface. Good agreement was found between predicted and measured yield loci. The study also examined the influence of subsequent isotropic compression on the yielding characteristics of the natural clay. The indications are that the anisotropy developed during deposition disappears when the sample is loaded to a stress level at least twice the stress generated during the original deposition process. The methods developed in the paper have also been applied to test results reported previously on Winnipeg clay, and good agreement was obtained.Key words: sampling, anisotropy, elasticity, suction, stiffness, yielding.

Corixidae (Hemiptera Heteroptera) in two artificial lakes on Irish cutaway raised bog

Oceanic raised bogs have long been exploited, both commercially and privately in Ireland. At present, 23,628 ha or 8% remains in an active state (Foss 1998), while at least 60,000 ha will be cutaway by the middle of the next century (Egan 1998). Industrial exploitation through milling involves the gradual removal of layers of peat until the less combustible fen peat is reached. On abandonment, the substrate is generally a mix of acid and alkaline peats and even occasionally lake marl and boulder clay. The surface level tends to be below the average water-table and in recent years areas of cutaway have been flooded to create lakes. Water is chiefly supplied by groundwater and precipitation, but some lakes may be fed by drains or small streams. these water-bodies have been allowed to colonise naturally. The development of macroinvertebrate communities was studied in two such lakes in central Ireland. As part of a wider investigation, Corixidae were sampled regularly over the course of a year and the animals examined. Interesting comparisons between sexes and between lakes were made.

Estimation of in situ stresses using anisotropic elasticity and suction measurements

Sampling and specimen preparation produce changes in mean effective stresses and pore water pressures, even with ‘perfect sampling’. The paper takes an existing simplified three-parameter cross-anisotropic elastic model and uses it to model these changes. The required ratio of cross-anisotropic parameters J/3G* can be obtained from standard CIU triaxial tests. If measurements are also made of suctions in unloaded specimens in the laboratory, then a combination of J/3G*, the measured suction, and the effective overburden pressure permits an estimation of the horizontal effective pressure and the K0 ‘at rest’ coefficient. This can be helpful in numerical modelling that needs to start from in situ conditions, and in planning pressure levels for reconsolidation of clay specimens in the laboratory. Tests were done on Belfast Upper Boulder Clay from a depth of 28 m. Values of horizontal in situ effective stress estimated from these measurements compare favorably with conventional estimates of the ‘at rest’ coefficient K0 and the overconsolidation ratio. Estimates of horizontal stress in London Clay were made using published data and the results compared with actual measurements. Again reasonable agreement was obtained.

Recent large-diameter tunnel construction in Singapore using sprayed concrete linnings

Sprayed Concrete Lining (SCL) or the New Austrian Tunnelling Method (NATM) has had limited exposure in Singapore. Previously this has been restricted to excavations of less than 6 metres inside diameter in the boulder clay and decomposed granite. For the North East Line Project (NELP) a section of SCL tunnel was constructed as part of the tunnelling works on Contract 710. This paper describes the design, planning, and construction issues of twin 8.4-metre inside diameter crossover tunnels spaced less than one diameter apart constructed in the Jurong Formation. In addition, the construction of a SCL tunnel in the Old Alluvium, is also described. This tunnel is an advance tunnel for the future Deep Tunnel Sewage Scheme (DTSS) and is being constructed as part of the NELP Contract 705 Works. Details of the Jurong Formation and Old Alluvium are given together with their geotechnical characteristics, which played a major role in the selection of temporary support methods used and the behaviour of the ground during tunnelling. The planning and design issues concentrate on aspects to ensure overall integrity and stability of both SCL projects. The success of various construction techniques utilised to construct the tunnels safely is discussed and a summary of the ground movements is presented.

Permafrost as a climatic indicator in northern Victoria Land, Antarctica

AbstractKnowledge of permafrost characteristics and distribution in Antarctica and their relationships with present and past climates is still poor. This paper reports investigations on permafrost in an area located between Nansen Ice Sheet to the south and Mount Melbourne (2732 m a.s.l.) to the north. Investigation methods included geomorphological surveys and geoelectrical soundings as well as crystallography, chemical and isotopic analyses of the ground ice. Geomorphological surveys helped to explain the relationships between periglacial landforms (e.g. rock glaciers and patterned ground) and the glacial history of the area. Geoelectrical soundings allowed us to define different ground-ice units in the ice-free areas. Each unit was characterised by a different type of permafrost (dry or ice-poor permafrost, marine or continental massive buried ice and sub-sea permafrost). To identify the nature of ground ice, trenches were dug and some shallow boreholes were drilled to a maximum depth of-3.6 m in massive buried ice. Samples of both ice-poor permafrost and massive ice were collected and analyzed. Chemical, isotopic δ18O and crystal analyses were also carried out. The relationships between climate and thermal regimes of the active layer and the upper part of permafrost were determined using a monitoring station for ground temperatures at Boulder Clay Glacier, near the Italian Antarctic station. During winter, there were several significant thermal-inversion events in the ground, which cannot be explained only by air-temperature changes, suggesting a possible influence of winter snowfall, even if these events are usually considered very rare.

The Roman Bridge at Piercebridge, North Yorkshire-County Durham

The village of Piercebridge in County Durham lies on the northern bank of the River Tees and on the route of the Roman Dere Street (FIGS 1 and 2). The village lies at c. 59 m aOD, sited on the river gravels of the Tees as it cuts through the surrounding Boulder clay. A Roman fort at Piercebridge has been known since at least Gibson's second edition of Camden's Britannia in 1722 and Roman Piercebridge is perhaps best known for the series of small excavations undertaken on that fort between 1934 and 1964. On this basis the fort could be identified as being essentially of later Roman date. Inhumation burials certainly or probably of Roman date have been recorded on a number of occasions.

AN INSTRUMENTED DRIVEN PILE IN DUBLIN BOULDER CLAY.

Precast concrete piles, driven to a set in Dublin black boulder clay, have been used extensively in Dublin where depths of fill or soft soil make shallow foundations uneconomical. This paper describes the results of a test pile which was instrumented with vibrating wire gauges and pore pressure probes at various levels along the pile shaft. Three compression tests were carried out on the test pile: one within 2.4 hours of its installation, one after 1.8 days and one after 17 days. Finally, a tension (pull-out) test was carried out after 24 days. The loading tests showed that there was a significant increase in both the ultimate shaft and base capacity with time and that about 60% of the total pile capacity was achieved in end-bearing in all three compression tests. The last compression test on the pile, which was carried out when all of the excess pore pressure set up by driving had dissipated, indicated an apparent Nc value of over 50 when applied to the in situ undrained shear strength of the boulder clay prior to the test. An analysis of the base displacement and pore pressures during load indicated that this high Nc value is likely to be due to an increase in the mean effective stress at the pile tip due to its insertion. (A)

Recharge through the drift: a study of contrasting Chalk catchments near Redgrave Fen, UK

Abstract Redgrave and Lopham Fens lie at the headwaters of the Rivers Waveney and Little Ouse in East Anglia, UK. The Fens are supported by groundwater discharge from the drift-covered Chalk underlying the area. This discharge and the ecological value of the Fens have been derogated by public water supply abstractions from a nearby borehole. Aspects of the investigations undertaken to construct a groundwater model to assess options for relocating the borehole away from the Fens are described. Particular attention is given to the value of using basic river flow data analysis to identify contrasts in the hydrological characteristics of the two catchments and constrain estimates of recharge. The Waveney catchment is flashy and dominated by run-off whereas the Little Ouse receives a more significant groundwater baseflow contribution. These catchment contrasts reflect subtle variations in boulder clay thicknesses and topography. They also reflect the contrasting effectiveness of the two rivers as drains on the groundwater system. Average recharge to the Chalk through the boulder clay-covered interfluves is estimated at around 36 mm a −1 (which is similar to other values quoted in the literature). Recharge may locally fall to less than 10 mm a −1 where the boulder clay is thick and the Chalk is strongly confined.

SEM Analysis of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin of the Quaternary “Glacial” Boulder Clays at Huangshan (Yellow Mountain), East-Central China

Geomorphic features and Pleistocene deposits on Huangshan have been attributed to glaciation. Recent reassessment questions this interpretation. As part of the reassessment, quartz sand grains from deposits identified as glacial boulder clays (till composed of boulders in a clay or silt matrix) were analyzed by scanning electron microscope for evidence of their sedimentary history. Surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains. The analysis shows that the grains lack typical glacial textures. The surface textures present indicate a complex history. Nonuniformly weathered grain surfaces point to chemical weathering of the source rock. This is supported by the deep weathering of the nonquartz clasts in the sand-sized fraction as well as in boulders at the outcrops. The close correspondence in surface-texture frequencies with those of the alluvial grains indicates an alluvial component to the grains’ history. The similarity with the colluvial grains and the outcrops’ structures suggest an alluvial/colluvial origin for the deposits. The history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east-central China for at least part of the Pleistocene.

Clay mineral assemblages in the western Baltic Sea: recent distribution and relation to sedimentary units

Surface samples and nine cores from the western Baltic Sea and marginal water bodies were investigated for clay mineral composition. The clay mineral assemblages of recent sediments are rather homogeneous. Variations result mainly from the erosion of different glacial source deposits. High percentages of illite and low kaolinite/chlorite and quartz/feldspar ratios are characteristic for this glacial source. Advection of kaolinite-rich suspensions from the North Sea is believed to account for higher kaolinite/chlorite ratios in the Mecklenburg Bight. A contribution of the rivers Trave and Oder to the western Baltic Sea is indicated by increased smectite values in marginal water bodies. They correspond to increased kaolinite/chlorite and quartz/feldspar ratios. In the main basins the river signal is diluted beyond recognition. Cores from the Arkona, Bornholm and Gotland Basins penetrate through post-Littorina muds and sediments of the Ancylus Lake/Yoldia Sea into Late Glacial sediments of the Baltic Ice Lake. Clay mineral assemblages are characterized by an increase in kaolinite/chlorite ratios from Late Glacial to Holocene sediments, with a distinct shift at each facies change. This allows the distinction and core to core correlation of main lithological units with kaolinite/chlorite ratios. Kaolinite enrichment of Holocene muds corresponds to a brackish-marine facies and may reflect influx of kaolinite-rich suspensions from the North Sea. Cores from the lagoon of the Oderhaff show fluctuations in the contributions of the two main sediment sources: river suspension and glacial deposits during the Late Glacial and Postglacial sequence. Lacustrine sediments, which were deposited prior to 5500 years B.P. are characterized by smectite, kaolinite and quartz from the drainage area of the Oder river. Erosion of coastal and offshore glacial boulder clays with the Littorina transgression supplied a marine component rich in illite, chlorite and feldspars to the brackish muds of the Oderhaff.

Magnetic properties of sediments in a Polish lake: evidence of a relation between the rock-magnetic record and environmental changes in Late Pleistocene and Holocene sediments

A study of mineral magnetic parameters was carried out on a Late Pleistocene and Holocene sedimentary sequence (of nearly 18 m) from Lake Bledowo (central Poland). Sediments of Lake Bledowo have already been analysed for bulk sediment mineralogy and biogenic materials. The mineral magnetic stratigraphy confirms the major changes in palaeo-environmental conditions that have been deduced from other methods. The most important mineral magnetic change results from the authigenetic formation of ferrimagnetic greigite, Fe3S4, during the beginning of lacustrine conditions (± 12 000 yr BP). Our data also indicate a detrital origin of overlying ferrimagnetic iron oxides. It is suggested that they originate from brown soils developed on the boulder clay constituting the west side of the lake shore. Variations of ferrimagnetic iron oxide size are related to the early diagenetic processes in the sediment. Larger particles are present in periods with early diagenesis of organic matter in anoxic conditions. This indicates the dissolution of fine magnetic particles by iron-oxide-reducing bacteria and results in homogeneous magnetic grain sizes, despite their origin from soils, characterized by a multimodal grain-size distribution.

Soil mechanics of the potentially expansive clays in Poland

This paper is an attempt to evaluate the expansivity of the main genetic types of Polish clays which very often are considered as a bedground for engineering structures. Lithological characteristics and basic physical properties presented in this paper concern the soils of (I) Quaternary age: Boulder clays and glaciolacustrine clays, (II) Tertiary continental and marine clays: Mio-Pliocene clays of Poznan series, Miocene clays of the Carpathian Foredeep (unweathered and weathered), bentonites and bentonitic clays, oligocene clays of Szczecin area and Carboniferous bentonites (Tables 1 and 2). Based on the indirect methods described by Van der Merwe (1964) and Seed et al. (1962) nomograms were used to evaluate potentially expansive soils. Information obtained includes correlation between potential expansiveness (PE), degree of expansion (DE), swelling potential (5) and the percentage content and mineral composition of the clay fraction. Graphic illustrations are presented in Figs. 1–7, which also include nomograms for the approximate estimation of the value of swell pressure (σ sp). The evaluation of potential expansivity of clays in Poland plays a key role in the design of engineering structures and in site selection.

Hydrochemical and stable isotope evidence for the extent and nature of the effective Chalk aquifer of north Norfolk, UK

In eastern England the Chalk aquifer is covered by extensive Pleistocene deposits which influence the hydraulic conditions and hydrochemical nature of the underlying aquifer. In this study, the results of geophysical borehole logging of groundwater temperature and electrical conductivity and depth sampling for major ion concentrations and stable isotope compositions (δ 18O and δ 2H) are interpreted to reveal the extent and nature of the effective Chalk aquifer of north Norfolk. It is found that the Chalk aquifer can be divided into an upper region of fresh groundwater, with a Cl concentration of typically less than 100 mg l −1, and a lower region of increasingly saline water. The transition between the two regions is approximately 50 m below sea-level, and results in an effective aquifer thickness of 50–60 m in the west of the area, but less than 25 m where the Eocene London Clay boundary is met in the east of the area. Hydrochemical variations in the effective aquifer are related to different hydraulic conditions developed in the Chalk. Where the Chalk is confined by low-permeability Chalky Boulder Clay, isotopically depleted groundwater (δ 18O less than −7.5‰) is present, in contrast to those areas of unconfined Chalk where glacial deposits are thin or absent (δ 18O about −7.0‰). The isotopically depleted groundwater is evidence for groundwater recharge during the late Pleistocene under conditions when mean surface air temperatures are estimated to have been 4.5°C cooler than at the present day, and suggests long groundwater residence times in the confined aquifer. Elevated molar Mg:Ca ratios of more than 0.2 resulting from progressive rock-water interaction in the confined aquifer also indicate long residence times. A conceptual hydrochemical model for the present situation proposes that isotopically depleted groundwater, occupying areas where confined groundwater dates from the late Pleistocene, is being slowly modified by both diffusion and downward infiltration of modem meteoric water and diffusive mixing from below with an old saline water body.

A Pottery Kiln at Catterick

Evaluation excavations undertaken in early 1994 revealed elements of a ditch system and a pottery kiln within the confines of RAF Catterick (NGR SE 24350 96900). The site is located on river gravels close to their interface with the Boulder Clays that occupy the areas to the west and south. The River Swale lies some 700 m to the east and the site forms part of the Roman roadside settlement known at Bainesse Farm located on Dere Street some 2 km south of Cataractonium Roman town. Other work undertaken as part of the evaluation programme demonstrated that the roadside settlement extended for up to 750 m south of Bainesse Farm, which indicates that the site extends for approximately 1 km along Dere Street. There is little or no evidence for the presence of structures on side roads away from Dere Street, although the work undertaken in 1981–82 did demonstrate the existence of two strip-buildings, set one behind the other, in some of the building plots. The kiln site lies on the eastern periphery of the settlement and is quite possibly part of a zone of industrial activity around the fringes of the site. The latter suggestion arises from the discovery of a scatter of slag during fieldwalking undertaken as part of the evaluation that appeared to define the limits of the settlement to the south and west.

The genesis of the brown boulder clay of Dublin : E. R. Farrell, P. Coxon, D. H. Doff & L. Pried'homme, Quarterly Journal of Engineering Geology, 28(2), 1995, pp 143–152

The genesis of the brown boulder clay of Dublin : E. R. Farrell, P. Coxon, D. H. Doff & L. Pried'homme, Quarterly Journal of Engineering Geology, 28(2), 1995, pp 143–152