Peaty Clay Research Articles

Predicting natural arsenic enrichment in peat-bearing, alluvial and coastal depositional systems: A generalized model based on sequence stratigraphy

Hazardously high concentrations of arsenic exceeding the threshold limits for soils and drinking waters have been widely reported from Quaternary sedimentary successions and shallow aquifers of alluvial and coastal lowlands worldwide, raising public health concerns due to potential human exposure to arsenic. A combined sedimentological and geochemical analysis of subsurface deposits, 2.5–50 m deep, from the SE Po Plain (Italy) documents a systematic tendency for naturally-occurring arsenic to accumulate in peat-rich layers, with concentrations invariably greater than maximum permissible levels.A total of 366 bulk sediment samples from 40 cores that penetrated peat-bearing deposits were analysed by X-ray fluorescence. Arsenic concentrations associated with 7 peat-free lithofacies associations (fluvial-channel, levee/crevasse, floodplain, swamp, lagoon/bay, beach-barrier, and offshore/prodelta) exhibit background values invariably below threshold levels (<20 mg/kg). In contrast, total arsenic contents from peaty clay and peat showed 2–6 times larger As accumulation. A total of 204 near-surface (0–2.5 m) samples from modern alluvial and coastal depositional environments exhibit the same trends as their deeper counterparts, total arsenic peaking at peat horizons above the threshold values for contaminated soils.The arsenic-bearing, peat-rich Quaternary successions of the Po Plain accumulated under persisting reducing conditions in wetlands of backstepping estuarine and prograding deltaic depositional environments during the Early-Middle Holocene sea-level rise and subsequent stillstand. Contamination of the Holocene and underlying Pleistocene aquifer systems likely occurred through the release of As by microbially-mediated reductive dissolution. Using high-resolution sequence-stratigraphic concepts, we document that the Late Pleistocene-Holocene lithofacies architecture dictates the subsurface distribution of As. The “wetland trajectory”, i.e. the path taken by the landward/seaward shift of peat-rich depositional environments during the Holocene, may help predict spatial patterns of natural As distribution, delineating the highest As-hazard zones and providing a realistic view of aquifer contamination even in unknown areas.

The effects of the rock stratigraphy on TPH/PAH absorption and transmission in some sections of the Gokana and Khana Local Government Areas

Concentration of TPH/PAH in soils in parts of Gokana and Khana local government areas of Rivers state were examined using samples from 30 shallow wells drilled with hand auger. The core intervals penetrated, ranged between 0 on the surface to 100cm at total depth and was composited into two sections corresponding to upper 0 – 0.5m and lower 0.51 – 0.1m sections respectively. The samples were described to determine their sedimentological characteristics and effect on absorption and transmission of fluids. The total hydrocarbon content in samples of the study area were determined following the EPA 1664 Hexane Method (Method No: EPA 418.1/413.2 &amp; EPA 1664). Individual concentrations of identified PAH congeners were noted and combined to generate the PAH concentrations in each of the two composited sections of the 30 sampled locations. The sedimentology of the logged sections consists mostly of peaty clay, clayey sands and organic clay in the upper section and clayey silt and clayey sand in the lower section. TPH in the study area ranged between 20612mg/kg at Location 15 to 37.09mg/kg at Location 11 for the upper (0 – 0.5m) sections and 14731mg/kg at Location 12 to 14.67mg/kg at Location 17 for the lower (0.51 – 1m) section. PAH ranged from 9.55mg/kg at Location 12 to &lt;0.01mg/kg at several other Locations for the upper (0 – 0.5m) sections and 5.71mg/kg at Location 11 to &lt;0.01mg/kg at several other Locations for the lower (0.51 – 1m) section. Correlation of sedimentology descriptions with the geochemical analysis indicates high concentrations of total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) within the upper (0 – 0.5m) sections than in the lower (0.51 – 0.1m) sections in consonant with the stratigraphy of the logged section.

In-Situ Stabilization Analyses of Peaty Clay Soil Layers using Solid Waste from of Biomass Power Plant

In-Situ Stabilization Analyses of Peaty Clay Soil Layers using Solid Waste from of Biomass Power Plant

The Influence of Preconsolidation Pressure on Undrained Shear Strength Characteristics of Peaty Clay in Sri Lanka

This research study investigated the effect of preconsolidation pressure on the shear strength parameters of very soft peaty clay based on a series of laboratory tests. The study included 15 Consolidated Undrained (CU) triaxial tests on peaty clay extracted from the Nilwala river basin, with preconsolidation pressures ranging from 0 to 100 kPa in 20 kPa intervals and cell pressures of 50, 100 and 150 kPa. The results indicated that the peak deviator stress of peaty clay decreased with increasing preconsolidation pressure, indicating decrease in its shear strength parameters with preconsolidation pressure. It was observed that peaty clay is highly sensitive to disturbance and requires sufficient time to regain its shear strength once its natural microstructure is altered. The study has significant implications for the construction of embankments on soft soils, particularly peaty clays. It highlights the need for accurate estimation of the undrained shear strength parameters of peaty clay, considering soil composition, structure and type of loading. It also emphasizes the importance of minimizing disturbance during construction activities to avoid compromising the stability of embankments.

Below ground carbon stock and carbon sequestration potentials of mangrove sediments in Eastern Niger Delta, Nigeria: Implication for climate change

The carbon sequestration capacity and climate change mitigation potentials of mangrove sediments in eastern Niger Delta were investigated. The aim was to determine the carbon stock in the sediments as a measure of carbon sequestration. A total of 312 sediment samples were obtained from 24 sampling 100 cm deep borings at seven locations using an open-cylindrical gouge auger of 100-cm length and 5-cm diameter. The procedures for field sampling, laboratory analysis and result presentation followed protocols for forest carbon measurement, monitoring and reporting. The lithology at the site, which is a major control on the distribution of organic carbon, included peat, peaty clay, and clayey peat with pockets of sands. Sediment bulk density (SBD), organic carbon concentration (%C), were used to estimate the organic carbon stock, carbon dioxide equivalent (CO2e), and to calculate carbon sequestration rate (CSR) and sequestration potential (CSP). Mean values of SBD were 1.30 g/cm3) and 12.48 %) respectively. Similarly, carbon averaged 39.80 Mg ha–1. The total carbon stock of the study area was estimated at 199,617.36 ± 55.64 Mg C, equivalent to 732,595.71 ± 55.64 Mg CO2. CSR was estimated at 4.54 g C cm–2 yr–1 while CSP of mangrove sediments was estimated at 21.56 Mg C yr–1. The result showed that 732,595.71 ± 55.64 Mg of carbon dioxide could either be removed or released to the atmosphere by the mangrove forest of Niger Delta through forest management practices and/or degradation. The study reinforces the need for the protection of mangroves against all anthropogenic-related degradation to improve carbon sequestration potential and achieve target in line with Sustainable Development Goal 13.

Reliability of Soil and Ground Improvement Techniques in Niger Delta Region of Nigeria

This research work presents a study of the reliability of ground improvement methods in three states of the Niger Delta Area of Nigeria namely: Rivers, Bayelsa and Akwa –Ibom states. Natural soil which is peaty clay in nature was obtained from different locations in the area of study and improved with different percentages of chemicals, cement, ranging from 2% to 10% and geotextile materials after which reliability analysis was carried out on them for CBR and UCS tests. Results show that geotextile materials are not suitable for improving the peaty clay soils in the locations under study due to poor values of reliability while the reliability values obtained for soil improved with cement increases with increase in percentage addition of cement and curing period. Reliability values for soil improved with chemicals shows some variability but increase as curing period increases at percentage addition of chemicals from 2% to 6% for Calcium Oxide, Calcium Chloride, Calcium Hydroxide and Aluminium Hydroxide before a decrease in value. Sodium silicate reliability peaked at 8% while the optimal value of reliability for cement was realised at 10%.

Geotechnical Considerations for Foundation Design in Parts of Yenagoa, Bayelsa State, Niger Delta Nigeria

This research was to determine geotechnical properties of the subsoils in some part of Yenagoa and environs to obtain proper foundation design parameters, six towns in Yenagoa local government area, Bayelsa state was investigated. Six geotechnical boreholes was drilled and laboratory studies of soils samples were obtained from 0-20.25m deep. Subsurface soil profiles were delineated followed by determination of their index and mechanical properties, including Atterberg limits, particle sizes distribution, undrained shear strength, shear box test and consolidation coefficient. The general soil profile consists of (from top to bottom), , upper Silty clay horizon (0.0-5.25m thickness) soft to firm for Yenagoa study areas, Medium silty clay horizon (0.75 to 1.5m thickness) soft to firm Yenagoa study areas, low clayey sand horizon (0.75 to 1.5m thickness) soft Yenagoa study areas, peaty clay (1.0m thickness between 3.0-4.0m) soft Igbogene Yenagoa, upper sand horizon (3.0m thickness) silty sand Etegwe town Yenagoa, lower sand horizon (13.5 to 18.0m) silty sand to fine to medium and medium coarse appear in all the boreholes in Yenagoa. Yenagoa sub-soil show clay of high plasticity, silt of intermediate to high plasticity (CH, MI and MH) according to unified soil classification system from the results it shows that pad foundation is more economical in the study areas. Raft foundation is more economical in the six towns study areas of Yenagoa with Allowable bearing capacity of the upper clay layer ranges from 23-128KN/m2 In view of the significant variations in the stratification and engineering geological index properties of the soil in the six towns in Yenagoa while geotechnical data of one location cannot be used as a basis for design of foundation in a nearby land. Axial load carrying capacity for 305, 306mm, 356, 360mm, 406mm, 600and 610mm diameter for bore pile and tubular driven steel cased piles respectively were calculated for all the studies areas. Where high rise building is required in the various study areas. The study shows that the frequent causes of building collapse in Yenagoa are as a result of inadequate geotechnical investigations of the subsoil, poor quality materials, and poor work supervision.

Lagena Inferocostata – An Opportunistic Index Species of Hydrocarbon Pollutants in Gokana and Khana Local Government Areas of River State, Nigeria

Thirty shallow cores ranging from 0.0 – 1.0m and composited into upper and lower section, was studied to determine relationship between petroleum hydrocarbon pollutants and benthic foraminiferal species in order to determine an index for environmental monitoring in the study area. The core samples were taken from Gokana and Khana Local Government Areas of Rivers State, Nigeria. The cores were treated with Rose Bengal solution to distinguish between then acoenose and biocoenosis benthonic foraminiferal. The cores were analyzed for sedimentology, petroleum hydrocarbon concentrations and micropaleontology. Sedimentological descriptions of the cores indicated inhibited free flow of fluids based on the rock textures which mostly consists of clays and peaty clays. Petroleum hydrocarbons analysis consisted of Total Petroleum Hydrocarbon (TPH) and Polycyclic Aromatic Hydrocarbon (PAH). The results in concentrations of the petroleum hydrocarbons indicated higher concentrations in the upper composited sections. Total Petroleum Hydrocarbon (TPH) and Polycyclic Aromatic Hydrocarbon (PAH) ranged between (20612mg/kg – 37.09mg/kg and 9.55mg/kg – &lt;0.01mg/kg respectively) in the upper composited section and between (14731mg/kg – 14.67mg/kg and 5.71mg/kg – &lt;0.01mg/kg respectively) in the lower composited section. Occurrence of benthonic foraminiferal in the study samples is very low to barren among very low diversity. Three benthonic foraminiferal diversities were identified in the study samples and included Lagenainferocostata, Anomalinoidesspp and Ammodiscus spp. Benthonic foraminifera showed negative correlation with TPH/PAH in the presence of carcinogenic Polycyclic Aromatic Hydrocarbon (PAH) congeners except for Lagenainferocostata which increased consistently and significantly with increasing TPH/PAH in the two composited sections. This suggested Lagenainferocostata as an Index opportunistic species for the hydrocarbon polluted study area.

Geological record of 18th and 19th century tsunamis along the Japan Sea coast of Tsugaru Peninsula, northwestern Japan

Our stratigraphic and paleontological investigations revealed three sandy event deposits (E1, E2, and E3) within peaty clay at the Sotomeyachi site on the Japan Sea coast of Honshu (mainland of Japan), northwestern Japan. Visual examination and X-ray computed tomographic images of samples of the deposits provided evidence of strong currents characterized by rip-up mud clasts, load casts, and erosional lower stratigraphic contacts. Marine, brackish, and freshwater diatom species in the deposits indicate they were derived from various coastal sources. Radiocarbon dating constrained the ages of event deposit E2 to 1764–1902 CE and E3 to 1558–1845 CE, 1699–1918 CE, and 1704–1781 CE. According to historical records, the E2 deposits likely correspond to the tsunami generated by the 1833 Shonai-oki earthquake, and the E3 deposits correspond to a tsunami associated with either a submarine landslide associated with the 1741 Oshima-Oshima eruption or the 1793 Nishi-Tsugaru earthquake. Because our numerical simulation of the 1741 tsunami showed no significant inundation at the study site, it is more likely that the 1793 earthquake was responsible for tsunami deposit E3. The E1 deposit is discontinuous and showed different characteristics (absence of load structures, rip-up mud clasts and mixed diatom assemblages) to those of events E2 and E3, so it is unlikely to be a tsunami deposit.

WHITE CLAY DEPOSITS AT DIFFERENT AREAS OF MADHABPUR AND BAHUBOL UPAZILA, HABIGONJ DISTRICT, BANGLADESH

A detail geological investigation was carried out in order to explore white clay deposite at 10 square kilometer areas of Madhabpur and 0.5 square kilometer areas of Bahubal Upazilas in Habiganj District of Bangladesh using hand auger and shallow drilling method. The whole surveyed area was identified for white clay deposits from qualitative as well as quantitative aspect. These deposits were marked at depths from 0.2 meter to 8.0 meter below the surface. Average thickness of white clay at Madhabpur and Bahubol area are 4.0 meter and 5.0 meter, respectively. The estimated reserve of white clay at Madhabpur area is about 68 million tons and that at Bahubal area is 2.8 million tons. Geological investigation suggests that the source rock near Tripura ranges was weathered, transported and deposited as feldspathic sandstone surrounding the present deposition of white clay. Later the sandstone was exposed and much of its feldspar content were weathered to the clay mineral (Kaolinite). Along with white clay peat, peaty clay, sticky clay and silica sand were also observed at depths ranging from 1.5 to 8 meter. Collected white clay samples are yellowish grey to light grey in color and highly compact in dry condition but pasty in wet condition. The dry white clay is soapy to feel, slakes in water, moderately sticky and plastic in nature. Al2O3 content ranged from 25.51 to 27.61% while average SiO2, and Fe2O3 content were found 54.58 and 3.872% respectively. Considering the physical and chemical properties the white clay of the studied area can be considered as moderate to good in quality. This white clay can use in ceramics and other industries. Therefore, this deposit of white clay may help to meet the current national demand and consequently to increase the economic growth.

ASSESSING THE SUSCEPTIBILITY OF STRUCTURAL COLLAPSE USING SEISMIC REFRACTION METHOD

Seismic refractive survey is a very important geophysical technique used to investigate the characteristics of the subsurface. The rate of building collapse has demanded the acquaintance about the structure of the subsurface especially in area where lands are recovered from water bodies for the aim of building. This paper presents the technique used in determining the thickness of the overburden for quarry prospecting using a geophysical method called as seismic refraction method. Seismic refraction method was used to delineated two distinct layers with the first layer having a weak and incompetent parameter values. The result revealed that the first layer is composed of unconsolidated formation of soft geomaterials and peaty clay that depict the lower values of parameters. This layer is underlain directly by clay, wet sand and sandy clay of soft and weak incompetent consistencies to a depth of 7 m in the subsurface. The second layer was found to have higher parameters than the first layer. The second layer revealed that the geologic formation composed of dry sand and sandy clay of fair to good competent. The geologic formation in the second layer was found to be more competent than the first layer with high allowable capacity and low ultimate failure potential. Geologically, the composition of the first layer is more recent in age of deposition than the second layer, characterized by unconsolidated geologic formation.

Briefing: Specific gravity of solids relationship with ignition loss for peaty soils

Peaty soils have an extremely high water content and a low specific gravity of solids (Gs) compared with most inorganic soils. Accurate knowledge of the Gsvalue allows void ratio computations for given water contents and densities. However, Gsdeterminations using the standard pycnometer test are time consuming and pernickety, such that the Gsvalue is often predicted by way of ignition loss (N) correlations instead. This paper presents original Gs–N data for 25 peaty soils (N = 23–86%) from the Dian-Chi Lake area, Kunming City, China, along with a data set assembled from various sources in the literature for 77 peaty clays and peats. The main research aim is to investigate correlations between Gs, natural water content (wn) and N for the standard ignition temperature of 440°C, thereby allowing indirect Gsestimations. For the 102 peaty soils examined, the best-fit Gs–N correlation was obtained for specific gravities of the inorganic and organic solids fraction values of 2.77 and 1.35, respectively. A weaker inverse bilinear relationship was found between Gsand wn. To overcome procedural differences between codes and for previous experimental work, it is recommended that an oven temperature of 105°C be consistently used for drying peaty soil specimens.

Burnt clay or terra bruciata in coastal basins of Southern Lazio, Italy: Evidence for prehistoric ignicoltura or resulting from drainage of Holocene pyritic sediments?

In the Agro Pontino and Fondi basin (Southern Lazio, Italy), burnt clay type material is common and was generally ascribed to the impact of ignicoltura. Based on the widespread occurrence of this material it was hypothesized that in these areas such ignicoltura was widely practiced in pre- and protohistoric times. However, direct evidence thereof, in the form of distinctly fired material, is extremely scarce. Earlier published and recent observations and analyses of a number of characteristic burnt clay sites together provide strong evidence for a pedogenetic origin of this material, i.e. by weathering of Holocene pyritic humic to peaty clays, brought about by their drainage. The process is well known from studies on acid sulphate soils and results in the accumulation of secondary iron concretions that resemble burnt clay but have a pedogenetic origin. Other products formed include jarosite and eventually gypsum, both regularly found in connection with burnt clay type material in these Holocene coastal basins. It is concluded that current hypotheses concerning the role and intensity of ignicoltura in both areas need to be seriously revised. Lastly, it seems likely that such pedogenetic burnt clay also occurs in other Mediterranean coastal basins where during the Holocene pyritic sediments formed and later on were drained for agriculture.

Reliability of Soil and Ground Improvement Techniques on Peaty Clay Soil – A Review

Reliability of Soil and Ground Improvement Techniques on Peaty Clay Soil – A Review

Aquatic macrophytes can be used for wastewater polishing but not for purification in constructed wetlands

Abstract. The sequestration of nutrients from surface waters by aquatic macrophytes and sediments provides an important service to both natural and constructed wetlands. While emergent species take up nutrients from the sediment, submerged and floating macrophytes filter nutrients directly from the surface water, which may be more efficient in constructed wetlands. It remains unclear, however, whether their efficiency is sufficient for wastewater purification and how plant species and nutrient loading affects nutrient distribution over plants, water and sediment. We therefore determined nutrient removal efficiencies of different vegetation (Azolla filiculoides, Ceratophyllum demersum and Myriophyllum spicatum) and sediment types (clay, peaty clay and peat) at three nutrient input rates, in a full factorial, outdoor mesocosm experiment. At low loading (0.43 mg P m−2 d−1), plant uptake was the main pathway (100 %) for phosphorus (P) removal, while sediments showed a net P release. A. filiculoides and M. spicatum showed the highest biomass production and could be harvested regularly for nutrient recycling, whereas C. demersum was outcompeted by spontaneously developing macrophytes and algae. Higher nutrient loading only stimulated A. filiculoides growth. At higher rates ( ≥ 21.4 mg P m−2 d−1), 50–90 % of added P ended up in sediments, with peat sediments becoming more easily saturated. For nitrogen (N), 45–90 % was either taken up by the sediment or lost to the atmosphere at loadings ≥ 62 mg N m−2 d−1. This shows that aquatic macrophytes can indeed function as an efficient nutrient filter but only for low loading rates (polishing) and not for high rates (purification). The outcome of this controlled study not only contributes to our understanding of nutrient dynamics in constructed wetlands but also shows the differential effects of wetland sediment types and plant species. Furthermore, the acquired knowledge may benefit the application of macrophyte harvesting to remove and recycle nutrients from both constructed wetlands and nutrient-loaded natural wetlands.

Geotechnical Index Properties of Soils in Abua and Environs: A Case Study of Obedum-Anyu-Emelago Road

The frequent collapse of engineering structure and in incessant cracks witnessed on walls of buildings within the Obedum-Anyu-Emelego axis of Abua/Odual Local Government Area of Rivers State prompted the need for geotechnical investigation to assess the suitability of soils and characterize their engineering properties as a guide to foundation designs. Soil samples were obtained between 0 and 30 metres depth and used in the study. The field boring and laboratory results shows that the stratigraphy is predominantly of medium with soft to firm brown mottle grey salty peaty clay and soft to firm grey mottle brown salty peaty clay in shallow borings of 2 m. The organic peaty clay layers are very poorly suited to support foundations due to very high compressibility compared to other materials. Laboratory analyses showed that the clays are characterized by moderately high moisture content and compressibility and fairly low undermined strength. CBR values between 5.7 percent to 8.5 percent, liquid limit between 38.8 percent and 50.6 percent, plasticity limit 18.8 percent and 25.5 percent. Comparison of these ranges of geotechnical properties with Bench Mark for sub grade indicated that they are of low standard. Recommendation includes the need for stabilization with lime and cement to avoid the collapse of structure or buildings within the study area.

Improving age-depth models of fluvio-lacustrine deposits using sedimentary proxies for accumulation rates

Lacustrine fills, including those of oxbow lakes in river floodplains, often hold valuable sedimentary and biological proxy records of palaeo-environmental change. Precise dating of accumulated sediments at levels throughout these records is crucial for interpretation and correlation of (proxy) data existing within the fills. Typically, dates are gathered from multiple sampled levels and their results are combined in age-depth models to estimate the ages of events identified between the datings. In this paper, a method of age-depth modelling is presented that varies the vertical accumulation rate of the lake fill based on continuous sedimentary data. In between Bayesian calibrated radiocarbon dates, this produces a modified non-linear age-depth relation based on sedimentology rather than linear or spline interpolation.The method is showcased on a core of an infilled palaeomeander at the floodplain edge of the river Rhine near Rheinberg (Germany). The sequence spans from ∼4.7 to 2.9 ka cal BP and consists of 5.5 m of laminated lacustrine, organo-clastic mud, covered by ∼1 m of peaty clay. Four radiocarbon dates provide direct dating control, mapping and dating in the wider surroundings provide additional control. The laminated, organo-clastic facies of the oxbow fill contains a record of nearby fluvial-geomorphological activity, including meander reconfiguration events and passage of rare large floods, recognized as fluctuations in coarseness and amount of allochthonous clastic sediment input. Continuous along-core sampling and measurement of loss-on-ignition (LOI) provided a fast way of expressing the variation in clastic sedimentation influx from the nearby river versus autochthonous organic deposition derived from biogenic production in the lake itself. This low-cost sedimentary proxy data feeds into the age-depth modelling. The sedimentology-modelled age-depth relation (re)produces the distinct lithological boundaries in the fill as marked changes in sedimentation rate. Especially the organo-clastic muddy facies subdivides in centennial intervals of relative faster and slower accumulation. For such intervals, sedimentation rates are produced that deviate 10–20% from that in simpler stepped linear age-models. For irregularly laminated muddy intervals of the oxbow fill – from which meaningful sampling for radiocarbon dating is more difficult than from peaty or slowly accumulating organic lake sediments – supplementing spotty radiocarbon sampling with continuous sedimentary proxy data creates more realistic age-depth modelling results.

NUMERICAL ANALYSIS ON THE EFFECT OF JET GROUT PILES ON AN EXCAVATION LOCATED IN AN URBAN AREA

The development of infrastructure in limited land space is a challenging scenario. Infrastructure in limited land space regions (e.g. Singapore) does not provide freedom to develop at favourable locations instead forces the engineer to design at the possible locations. Clay with high organic content, commonly referred as Peaty clay is predominant in coastal areas. This clay being highly acidic (PH>7) and possessing very low shear strength is a critical factor to the design of infrastructure in the vicinity. Ground improvement adopted weak strata will have varying effect and may not be able to achieve the required strength. This paper discusses the effect of ground improvement (Jet Grout Piles) on the sloped excavation predominantly in Peaty clay. A 15m deep excavation which is 60 m wide is used for the Finite element modeling. Impact study on a tunnel located 40m from the excavation is presented (The study is carried out for various achieved Jet grout piles strengths of 100, 200, 300, 400 and 500 kPa). The stability of the slopes for the various strengths is also discussed (GeoSlope was used as the medium to perform the geotechnical analysis).

The record of mid-Holocene maximum landward marine transgression in the west coast of Bohai Bay, China

Abstract This study used benthic foraminifera, diatom, total organic carbon, organic carbon isotope ratios, C/N ratios, and grain-size data from three AMS 14 C dated cores collected from the western coastal lowland of Bohai Bay, China, to elucidate the coastal response to relative sea-level change during the Holocene. A layer of peaty clay overlaying early Holocene terrestrial sediment was dated to 8400–8000 cal BP, and the peaty material in the sediment suggests possible vegetation cover before the mid-Holocene marine inundation in the study area. Sedimentary facies and changes in diatom and foraminifera assemblages suggest a five-stage marine transgression–regression history. During the first stage from 8000 to 7855 cal BP, the study area was inundated primarily by freshwater swamp. During the second stage from 7855 to 6000 cal BP the study area was under brackish water influence. In the third stage from c. 6000 to 5750 cal BP, the study area experienced marine influences, and by this time the Holocene transgression reached its maximum landward location and height. This was followed by a period of regression since c. 5750 cal BP. During the last 4000 years, the study area was influenced by freshwater and became a floodplain environment. Thus, this study reveals that the most landward position of the Holocene marine transgression was situated somewhere between the coring locations of DC01 and QX01, which is about 80 km inland from the present shoreline. This means the west coast of the Bay has advanced at an average speed of c. 13 m/a since the mid Holocene. The relative sea level around 6000 cal BP was at − 2.64 ± 0.1 m.

Investigation of a Proposed Four Storey Building Sites Using Geophysical and Laboratory Engineering Testing Methods in Lagos, Nigeria

The spate of engineering structures collapse in Lagos metropolis with its attendant loss of lives and properties has assumed an alarming proportion in recent times. Efforts to mitigate such incidence has necessitated an integrated geophysical and geotechnical investigation of a proposed four storey building sites with a view to determine the suitability of the site for the proposed project. Resistivity investigation, un-drained multi-stage triaxial compression and oedometer consolidation tests were carried out to determine the engineering properties of the subsurface. The results revealed peaty clay to silty sand materials characterized by 35kN/m 2 75kN/m 2 cohesion values, (5°-13°) internal friction, 29.3% 64.5% natural water content and 1.652 – 1.972 Mg/m 3 bulk density. The allowable bearing capacity of 50 kN/m 2 , volume compressibility from 0.115 m 2 /MN to 0.666 m 2 /MN, initial void ratio and consolidation coefficient of 0.779 1.381 and 2.7 m 2 /year 8.3 m 2 /year respectively on the pressure range of 0 to 400 kN/m 2 and estimated settlement values of 114 to 273 mm were obtained for the site materials. These results are indicative of soft to stiff clays and presence of sands and silts in the essentially clayey deposit. The study area is thus underlain by extensive zone of ductile and low strength founding materials having medium to high compressibility and settlement value that exceeds the tolerable limit suitable for founding a four storey building and should therefore be avoided. These characteristics preclude the use of conventional shallow foundations, piles or vibro-replacement up