Relationship between trace elements and depositional environments in shallow sediments: a case study from Southern Kanto Plain,Central Japan

Underground developments such as subways and shopping facilities have been increasing in number and magnitude in the relatively shallow subsurface of many urban areas where the earth materials commonly are composed of marine sediments. Marine sediments can contain significant amounts of toxic trace elements such as arsenic, boron, and lead. Changes in the subsurface environment caused by excavation and construction in underground developments could potentially cause these toxic elements to be dissolved into pore water of the sediments, which might lead to groundwater pollution. The purpose of this study is to investigate correlations among chemical properties of marine sediments, such as pH and electrical conductivity (EC), concentrations of toxic trace elements, and stratigraphic characteristics of the sediments. We selected three sites with different stratigraphic settings in the southern Kanto Plain around the Tokyo Metropolis. We collected core samples from shallow strata at a site in the Arakawa Lowland, southern Saitama, and at two sites in the Musashino Upland, Middle Tokyo. All sites have both marine and non-marine sediments up to 50–60 m in thickness. We determined trace element concentrations in the pore water, pH, EC, and loss on ignition. The results show that (1) the marine sediments tend to have low pH, high EC, and high sulfur concentration compared to the non-marine sediments (2) the concentration of most of the soluble heavy metals vary depending on the concentration of sulfate, the pH, and the formation processes of the strata, (3) the arsenic concentration is not related to sulfur concentration but apparently to Fe and Al concentrations, (4) the boron concentration is not related to any other properties implying that the boron level is independent of and cannot be predicted by common chemical properties, and (5) for all three sites, concentrations of most of the trace elements, EC, pH, and sulfate concentration were correlated with each other. This study shows that the concentration and potential mobilization of many toxic trace elements in marine sediments could be predicted by easily measurable pore water chemical properties such as pH and EC. This could be useful for predicting and avoiding the risk of groundwater pollution during underground development projects.     

An Anvilian (early pleistocene) marine fauna from western Seward Peninsula, Alaska

Cover sediments of the York Terrace exposed near the California River, western Seward Peninsula, Alaska, yield mollusks, ostracodes, and foraminifera that lived during the Anvilian transgression of early Pleistocene age. The fossiliferous sediments lie at the inner edge of the York Terrace, a deformed wave-cut platform that extends eastward from Bering Strait along much of the southern coast of Seward Peninsula. The seaward margin is truncated by the little-deformed Lost River Terrace, carved during the Pelukian (Sangamonian) transgression. The early Pleistocene sediments seem to have been deposited between the first and second of four glaciations for which evidence can be found in the California River area.The California River fauna includes several extinct species and several species now confined to areas as remote as the northwestern Pacific and north Atlantic. The fauna probably lived in water temperatures much like those of the present time but deeper water on the Bering Shelf is suggested.The presence of an early Pleistocene fauna at the inner edge of the York Terrace at California River shows that the terrace was largely carved before and during early Pleistocene time. However, a marine fauna apparently of middle Pleistocene age is found on the York Terrace near Cassiterite Peak, and this seems to indicate that the terrace remained low until middle Pleistocene time. Uplift of the York Terrace probably was accompanied by uplift of Bering Strait. The strait may have been deeper, and there may have been no land bridge between the Seward Peninsula of Alaksa and the Chukotka Peninsula of Siberia during most of early and middle Pleistocene time.     

Accidents due to oxygen deficiency and methane gas blow-off in Tokyo area,Japan

The groundwater leve in the Tokyo area had declined to about 60 m below the surface because of excess withdrawal of groundwater from various aquifers. Many construction workers died due to oxygen deficiency at construction sites from 1960 to 1980, the period of decreasing groundwater level. The compressed air in pneumatic foundation construction sites passed easily through the aquifer, and the oxygen in it was consumed by ferrous ions oxidizing to ferric ions. During periods of high barometric pressure, atmospheric air penetrates into the strata and it is deoxygenated there. Suffocation occurred not only at construction sites in underground excavations, but also in residences in Tokyo. Such acidents have become less frequent with recovery of the pore-water pressure in aquifers, which has accompanied the recovery of the groundwater level since 1972.With the recovery of the pore-water pressure and the groundwater level in the aquifer, fires and explosions resulting from gushes of methane have occurred in Tokyo lowlands since 1973. These blow-off gases are classified into two types: Kameido and Asakusa.The gas of the Kameido type originates from the Kazusa Group and migrates into upper alluvial deposits or Pleistocene sediments because of the recovery of pore-water pressure in the Kazusa Group. The gas of the Asakusa type formed from the air that penetrated the aquifers during the period of low groundwater level. Methane was produced by the depletion of oxygen accumulated in alluvial deposits and Pleistocene sediments. This gas blows off through wells in alluvial deposits and Pleistocene sediments at times of low barometric pressure. Accidents of the Asakusa type will not happen when the groundwater level and pore-water pressure in alluvial and Pleistocene sediments is restored to previous levels.     

Structures associated with inversion of the Donbas Foldbelt (Ukraine and Russia)

The Donbas Foldbelt is part of the Prypiat–Dnieper–Donets intracratonic rift basin (Belarus–Ukraine–southern Russia) that developed in Late Devonian times and was reactivated in Early Carboniferous. To the southeast, the Donbas Foldbelt joins the contiguous, deformed Karpinsky Swell. Basin “inversions” led first to the uplift of the Palaeozoic series (mainly Carboniferous but also syn-rift Devonian strata in the southwesternmost part of the Donbas Foldbelt, which are deeply buried in the other parts of the rift system), and later to the formation of the fold-and-thrust belt. The general structural trend of the Donbas Foldbelt, formed mainly during rifting, is WNW–ESE. This is the strike of the main rift-related fault zones and also of the close to tight “Main Anticline” of the Donbas Foldbelt that developed along the previous rift axis. The Main Anticline is structurally unique in the Donbas Foldbelt and its formation was initiated in Permian times, during a period of (trans) tensional reactivation, during which active salt movements occurred. A relief inversion of the basin also took place at this time with a pronounced uplift of the southern margin of the basin and the adjacent Ukrainian Shield. Subsequently, Cimmerian and Alpine phases of tectonic inversion of the Donbas Foldbelt led to the development of flat and shallow thrusts commonly associated with folds into the basin. A fan-shaped deformation pattern is recognised in the field, with south-to southeast-vergent compressive structures, south of the Main Anticline, and north- to northwest-vergent ones, north of it. These compressive structures are clearly superimposed onto the WNW–ESE structural grain of the initial rift basin. Shortening structures that characterise the tectonic inversion of the basin are (regionally) orientated NW–SE and N–S. Because of the obliquity of the compressive trends relative to the WNW–ESE strike of inherited structures (major preexisting normal faults and the Main Anticline), in addition to reverse displacements, right lateral movements occurred along the main boundary fault zones and along the faulted hinge of the Main Anticline. The existence of preexisting structures is also thought to be responsible for local deviations in contractional trends (that are E–W in the southwesternmost part of the basin).     

Changes of the geological environment of the Northern Black Sea region and the chemicalization of agricultural production

The generalization of the data available, field and laboratory investigations made it possible to estimate the pesticide inflow with large rivers to the NW part of the Black Sea, and the degree of pollution of the soil cover, bottom sediments of water bodies, confined aquifers with pesticides and ground water with nitrates. As a result of the uncontrolled use of agrochemicals their residual quantities were found in 66–93% of the samples. In connection with economic activities the greatest damage was caused to the ground water — the main source of water supply in the region: in some areas the depletion of their resources, intrusion of sea water and salt ground waters into aquifers as well as presence of residual quantities of pesticides in concentrations exceeding the maximum permissible limit were detected.Ideas on limitation of the harmful impact of agrochemicals upon the region's environment are presented here.     

Simultaneous normal faulting and extensional flexuring during rifting: an example from the southernmost Upper Rhine Graben

The southern end of the Upper Rhine Graben (URG) is formed by a major continental transfer zone, which was localised by the reactivation of ENE-oriented basement faults of Late Palaeozoic origin. A combination of subcrop data (derived from exploration wells and reflection seismic lines) and palaeostress analysis provided new constraints on the timing and kinematics of interacting basement faults. Rifting in the southern URG began in the Upper Priabonian under regional WNW–ESE-directed extension, oriented roughly perpendicular to the graben axis. In the study area, this led to the formation of NNE-trending half-grabens. Simultaneously, ENE-trending basement faults, situated in the area of the future Rhine-Bresse Transfer Zone (RBTZ), were reactivated in a sinistrally transtensive mode. In the sedimentary cover the strike-slip component was accommodated by the development of en-échelon aligned extensional flexures. Flexuring and interference between the differently oriented basement faults imposed additional, but locally confined extension in the sedimentary cover, which deviated by as much as 90° from the regional WNW–ESE extension. The interference of regional and local stresses led to a regime approaching radial extension at the intersection between the URG and RBTZ.     

Age and significance of fossil white spruce (Picea glauca), Tunica Hills, Louisiana-Mississippi

Radiocarbon dates indicate a Farmdalian through Woodfordian age for fossil white spruce (Picea glauca) in the Tunica Hills, a greater time span than previously documented. These dates, furthermore, require revision of the ages of fluvial terrace deposits in the region. Spruce-bearing Terrace 1 sediments, previously regarded as late Woodfordian to Holocene age, are of Farmdalian to late Holocene age. Terrace 2 sediments, previously assigned a Sangamonian or Farmdalian age, are of probable Altonian age. Plant fossils in Terrace 1 sediments represent two climatically and temporally distinct assemblages: a cool-temperate, Farmdalian-Woodfordian assemblage dominated by white spruce but including deciduous hardwoods suggestive of an oak-hickory association; and a warm-temperate Holocene assemblage composed of southern hardwoods and nonarboreal species representative of the modern flora of the Tunica Hills. Locally, fossils of white spruce have been reworked into younger Terrace 1 sediments containing the warm-temperate plant assemblage. The transition from the cool-temperate flora to the modern warm-temperate flora in the Tunica Hills probably occurred around 12,000 yr B.P.     

Study of subsurface geology in locating arsenic-free groundwater in Bengal delta,West Bengal,India

Over a large area of the Bengal delta in West Bengal, India, arsenic distribution patterns in groundwater were studied. One hundred and ten boreholes at different target locations were made, subsurface sediments were logged and analysed, and arsenic values in sediments vis-à-vis groundwater were compared. The study elucidates the subsurface geology of the western part of Bengal delta and characterises the sediments that were intersected in different boreholes with contrasting values of arsenic in groundwater. It reveals an existence of multiple aquifers stacked over each other. Depending on the color and nature of aquifer-sands and their overlying clay beds six aquifer types (Type-1 to Type-6) are classified and described. Sediment-arsenic for all the varieties of aquifer sands are near similar but the groundwater-arsenic of these six aquifers varies widely. Type-2 and Type-5 aquifers host arsenic-contaminated groundwater whereas the other four aquifers are arsenic-free. Type-2 and Type-5 aquifers are capped by a grey to dark grey soft organic matter-rich clay unit which makes these aquifers semi-confined to leaky-confined. These contribute in releasing arsenic from the sediments. The results of this study are employed in a proposed georemedial measure against this hazardous toxic element.     

Late Pliocene–recent tectonic setting for the Tianchi volcanic zone, Changbai Mountains, northeast China

Mafic volcanic rocks have erupted in the Tianchi volcanic zone, Changbai Mountains, northeast China, since late Pliocene time. The zone formed in an extensional environment during early-middle Cenozoic time, and in a compressional environment during late Cenozoic. Crustal thickness (about 40 km) in the Changbai Mountains is larger than the regional average of 34–36 km to the northwest and southeast. The conduit for magma upwelling was not coincident with the NE-striking regional faults, but seem to be confined to a deep-seated NW–WNW-striking fault zone. Since the late Pliocene, the Tianchi volcanic zone was subjected to crustal uplift within an intracontinental, weakly compressional environment (with minor WNW–ESE shearing) related to the westward subduction of the West Pacific plate. The nature of this volcanism is not typical of active, subduction-related continental margin volcanism. The magmatic evolutionary process evolved from trachybasalt through basaltic trachyandesite, trachyte, and pantellerite.     

Factors affecting arsenic concentration in groundwaters from Northwestern Chaco-Pampean Plain,Argentina

The concentration of arsenic measured in groundwater from three aquifers in the study area located in the Eastern Tucuman province, Argentina, mostly depends on the lithology, but the spatial and temporal variations of concentrations seem to be also controlled by pH changes, climatic factors, and human perturbations. The highest concentrations of As (more than 1,000 μg L⁻¹) were found in the shallow aquifer, made of As-rich loess, while the lowest concentrations were measured in the deep confined aquifer, consisting of alternating layers of alluvial sands/gravels and clays. Intermediate values were measured in the semiconfined aquifer made of the fluvial sediments deposited in the Salí River valley, that alternate in the upper part of the sedimentary sequence with layers of loess. Because most of As in the loess is considered to be adsorbed onto Fe-oxyhydroxide coatings, the increase of pH in the flow direction (west-east) leads to increasing arsenic concentrations towards the eastern border of the study area. The decomposition of organic wastes poured into the Salí River or associated with local and diffuse sources of contamination in the eastern part of the study area depletes dissolved oxygen, which leads to the reductive dissolution of Fe and Mn oxyhydroxides, and to the subsequent release of the adsorbed and co-precipitated As. This process mainly affects shallow groundwater and the upper part of the semiconfined aquifer. Geochemical and hydrological data also suggest that rising water table levels at the end of the wet season may also lead to reductive dissolution of As-rich Fe oxyhydroxides in the shallow aquifer.     

复杂地质条件下某深大基坑降水方案优化设计

某深大基坑位于长江下游岸边,场地地层为典型的二元结构,基坑开挖涉及的两层承压含水层间的弱透水层局部缺失,之间水力联系密切,基坑场地地质条件极为复杂,基坑施工降水直接关系到基坑工程的安全。这里将基坑分3个区,分别进行降水设计。具体降水方案:Ⅰ区两层承压含水层和Ⅱ区第一承压含水层被围护结构隔断内外水力联系,采用疏干井降水;Ⅱ区第二承压含水层未被围护结构隔断,Ⅲ区两层承压含水层水力联系密切,针对这两个区域设计了两套降水方案,方案一在Ⅱ区和Ⅲ区均布置有降水井,在Ⅱ区对第二承压含水层降水,在Ⅲ区对第一承压含水层降水;方案二仅在Ⅲ区布置降水井对第一承压含水层降水。为了更好地对降水方案进行对比分析,验证方案的可行性,对此进行了数值模拟分析,计算结果显示,两种方案均能满足降水要求,不过方案二布井数量少,基坑外水位降深较小,对周边环境影响更小,优于方案一。     

Evaluation of change in subsurface thermal environment due to groundwater flow in the Tokyo Lowland,Japan

Information on the distribution of subsurface temperature and hydraulic heads at 24 observation wells in and around the Tokyo Lowland, the eastern part of the Tokyo Metropolitan area, were examined to make clear the relationship between groundwater and the subsurface thermal environment in the urban area. Minimums in temperature–depth logs due to subsurface temperature increasing at shallow parts were recognized in 21 wells. This fact shows subsurface temperature is affected by ground surface warming in almost all of this area. Deeper than minimums, where the effects of surface warming became relatively small, regional variation is observed as follows: high temperatures are shown in the central part to the southern part, and low temperatures shown in the inland to eastern part. The high temperature area corresponds to an area where the lower boundary of groundwater flow is relatively shallow. This area corresponds also to an area with severe land subsidence resulting from excessive groundwater pumping. It is considered that this high temperature area is formed by the effects of upward groundwater flow affected by hydrogeological conditions and pumping. On the other hand, a comparison between past data (1956–1967) and present data (2001–2003) revealed widespread decreasing temperature in the inland area. This is explained by downward groundwater flow based on an analysis of temperature–depth logs. This fact suggests that subsurface temperature is not only increasing from the effects of surface warming but also decreasing from the effects of groundwater environment change due to pumping.     

10Be dating of the Main Terrace level in the Amblève valley (Ardennes,Belgium): new age constraint on the archaeological and palaeontological filling of the Belle‐Roche palaeokarst

It is still disputed whether very old archaeological and palaeontological remains found in the Belle‐Roche palaeocave (eastern Belgium) pertain to the Early (～1 Ma) or Middle (～0.5 Ma) Pleistocene. Here, in situ‐produced cosmogenic ¹⁰Be concentrations from a depth profile in nearby sediments of the Belle‐Roche terrace (Amblève Main Terrace level) are used as an indirect solution of this chronological issue. The distribution of ¹⁰Be concentrations in the upper 3 m of this profile displays the theoretically expected exponential decrease with depth. Assuming a single exposure episode, we obtain a best fit age of 222.5±31 ka for the time of terrace abandonment. However, below 3 m, the ¹⁰Be concentrations show a marked progressive increase with depth. This distinctive cosmogenic signal is interpreted as the result of slow aggradation of the fluvial deposits over a lengthy interval. Modelling of the whole profile thus suggests that the onset of the terrace formation occurred at around 550 ka, with a sediment accumulation rate of ～20 mm ka^?1. Based on two slightly different reconstructions of the geomorphic evolution of the area and a discussion of the temporal link between the cave and Main Terrace levels, we conclude that the fossil‐bearing layers in the palaeokarst pertain most probably to MIS 14–13, or possibly MIS 12–11. This age estimate for the large mammal association identified in the Belle‐Roche palaeokarst and the attribution to MIS 14–13 of a similar fauna found in the lowermost fossiliferous layers of the Caune de l'Arago (Tautavel) are in mutual support. Our results therefore confirm the status of the Belle‐Roche site as a reference site for the Cromerian mammal association in NW Europe.     

Formation and evolution of the Lower Terrace of the Rhine River in the area of Basel

The response of fluvial systems to tectonic activity and climate change during the Late Pleistocene influenced sedimentary processes and hence the conditions of river terraces formation. The northern Alpine foreland is well adapted for such studies due to the high sediment input and the variety of depositional environments. This study focuses on sediments of a part of the Rhine River in the area of Basel, at the Border between Switzerland, Germany and France. A detailed evolution of the Lower Terrace is inferred from sedimentological, geomorphologic and pedological observations as well as historical documents, and calibrated using different dating methods (optically stimulated luminescence, uranium series disequilibrium, radiocarbon). The Lower Terrace was deposited during two periods (30–15 ka and 13–11 ka), which correlate with two cold climatic phases, representing the Last Glaciation of the Alps and the Younger Dryas. These ages underline that main incision of the Lower Terrace braidplain in the area of Basel is restricted to post Younger Dryas times, as sediments of that age (13–11 ka) are found atop the highest levels. From then on, a flight of cut-terraces were formed with minor re-accumulation due to Holocene flood events. These findings demonstrate that the surface of a terrace does not always represent the age of sediment aggradation, and this should be remembered when using terraces to reconstruct the tectonic history of an area.     

The Middle Pleistocene terraces of the central Waveney valley,Earsham, south Norfolk,UK

Although substantial work has been done on the pre-glacial terraces of East Anglia, very little systematic work has been done to understand the origin of river terraces in East Anglia that have formed since ice last covered the region. This paper records the results of studies of exposures and borehole records in ‘classical’ Quaternary terrace landforms that are considered to have formed since the Anglian (MIS 12) Glaciation, in the middle Waveney Valley. These features have been examined in terms of their morphological and sedimentological properties, in order to provide a detailed record of their form and composition, understand their processes of formation, and identify their stratigraphical status. The results show that the main body of the highest terrace (Homersfield Terrace, Terrace 3) is not composed of river sediments, but of shallow marine sediments, and is a remnant of early Middle Pleistocene Wroxham Crag. River sediments, in the form of Anglian age (MIS 12) glaciofluvial Aldeby Sands and Gravels also exist in the area as a channel fill, cut through the Wroxham Crag, and reflect outwash erosion and sedimentation from a relatively proximal ice margin to the west. The results mean that the interpretations previously presented for the terrace landforms of the middle Waveney valley are not applicable. The issue of why the terrace stratigraphy, hitherto identified in East Anglia cannot be related to that for the River Thames to the south and the rivers of Midland England to the west, still requires further research.     

平推式滑坡中承压水的敏感性研究

研究平推式滑坡中承压水的作用范围,有利于准确评价斜坡稳定性,对平推式滑坡的成灾机理研究和灾害防治具有较好的指导意义。平推式滑坡中岩层倾角α较小,在承压水作用范围分析时通常忽略了岩层倾角的影响。基于地下水向河渠运动相关理论,考虑岩层倾角,建立平推式滑坡地下水渗流分析模型,推导出承压水作用范围L₁新的计算公式,详细计算分析了不同透水层参数下L₁对α的敏感性,并提出了敏感倾角的概念。计算结果表明,α对L₁影响显著,这种影响程度与透水层厚度、渗流量、以及渗透系数密切相关,透水层厚度越大,α对L₁的影响越显著;同时敏感倾角受透水层厚度、渗流量、渗透系数等参数影响。最后应用新模型分析滑坡实例,验证了新模型的合理性。     

Hydrochemistry and isotope geochemistry as tools for groundwater hydrodynamic investigation in multilayer aquifers: a case study from Lomellina, Po plain, South-Western Lombardy, Italy

A multicriteria approach in studying hydrodynamics of a multilayer aquifer system has been used in the Lomellina region (Northern Italy). It involves the reconstruction of the hydrogeological framework coupled to the definition of the hydrochemical and isotopic features of the aquifers. A shallow phreatic aquifer, reaching depths of about 60–80 m from the surface, and deeper aquifers containing confined groundwater, were distinguished. Groundwater generally shows mineralisation decreasing with depth; dissolved ions depict calcium-bicarbonate hydrochemical facies and stable isotopes define the recharge mechanisms, the origin of groundwater, and the hydraulic confinement of deep aquifers. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels. Tritium and Carbon-14 groundwater dating indicate long residence times (on the order of thousands of years) for confined aquifers. The confined aquifers show essentially passive hydrodynamic conditions and maintain a higher piezometric level than the phreatic aquifer. This inhibits the possibility of recent water penetrating far below the surface. The hydrogeological setting of the Lomellina region displays features which are common to other sectors of the Po plain. As a consequence, the results of this study, although conducted on a restricted area, are highly illustrative of groundwater hydrodynamics in large sedimentary aquifers.     

Delineation of hydraulic connectivity across a dolerite dyke through hydrogeological, geophysical and tracer studies—a case study

A linear WNW–ESE trending dolerite dyke, having a width of 30–40 m and length of 3–4 km, exists in the catchment area of Himayatsagar reservoir in Ranga Reddy district of Andhra Pradesh state, India. A company has planned to set up an oil-based industrial unit a few kilometers away in the upstream side of the dyke. Hydrogeological, geophysical and tracer studies were carried out for establishing hydraulic connectivity across the dyke, which would in turn reflect on the possibility of contamination of the groundwater regime in the downstream side of the dyke due to discharge of effluents from the industry. The result of multiparameter investigations carried out in the area reveal that hydraulic connectivity exists across the dyke body.     

Trace elements in groundwater as indicators of anthropogenic impact

The distribution of several minor and trace elements mainly in fresh (dominating TDS 160–400 mg/l) groundwater of Latvia have been investigated by the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) technique. An evaluation of results of about 700 analyses leads to the conclusion that concentrations of these elements is influenced by: pH–Eh conditions, groundwater residence time and diffuse contamination, whereas the role of water-bearing sediments is of secondary importance. Most trace elements are characterised by low mobility under alkaline and reducing conditions; concentrations in confined aquifers are much smaller than the Maximum Permissible Values for drinking water. The strongest anomalies of REE, Al and P were found in shallow groundwater around the former agrochemical storehouses.     

缓倾岩层洞穴系统发育模式的模拟试验

为模拟洞穴系统的发生、演化及分布规律。对缓倾岩层(倾角<15°)裂隙疏散或密集及多层或单层含水层结构的模型所做的溶蚀试验表明:均匀介质含水层在平面上洞穴发育呈不均匀状况,剖面上以浅饱水带及承压含水层顶板附近洞穴较发育;在裂隙不发育或不贯通时洞穴发育受层面裂隙控制;在缓倾岩层中,洞穴发育循反倾向的方向逐渐减弱。