Clay Accumulation Research Articles

Experimental Evaluation of Blockage Resistance and Position Caused by Microparticle Migration in Water Injection Wells

Offshore oil field loose sandstone reservoirs have high permeability. However, during the water injection process, water injection blockage occurs, causing an increase in injection pressure, making it impossible to continue injecting water on site. Current research mainly focuses on the factors causing water injection blockage, with less attention given to the blockage locations and the pressure increase caused by water injection. There is a lack of research on the change in the law of injection capacity. This paper establishes a simulation experiment for water injection blockage that can accommodate both homogeneous and heterogeneous cores. The experimental core is 1 m long and capable of simulating the blockage conditions in the near-well zone during water injection, thereby analyzing the core blockage position and blockage pressure. The study clarifies the influence of water quality indicators, heterogeneity, and core length on the blockage patterns in reservoirs during water injection. The research findings are as follows: I. The reservoir blockage samples were characterized using scanning electron microscopy (SEM), casting thin sections, and X-ray diffraction (XRD) analysis. The results indicate that the main factors causing blockage are clay, silt, and fine particulate suspensions, with the fine particles mainly consisting of hydrated silicates and alkali metal oxides. The primary cause of blockage in loose sandstone is identified as the mechanism of migration and accumulation of clay, fine rock particles, and suspended matter in the injected water. II. By monitoring pressure and permeability changes in the core flooding experiments, the impact of reservoir heterogeneity on water injection capacity was evaluated. The evaluation results show that the blockage locations and lengths in heterogeneous cores are twice those in homogeneous cores. III. For heterogeneous reservoirs, if the initial permeability at the inlet is lower than in other segments of the core, significant blockage resistance occurs, with the final resistance being 1.27 times that of homogeneous cores. If the initial permeability at the inlet is higher than in other parts, the final blockage resistance is close to that of homogeneous cores. This study provides theoretical support for the analysis of blockage locations and pressures in loose sandstone water injection and offers technical support for the design of unplugging ranges and pressures after blockage in heterogeneous formations. At the same time, it provides a theoretical basis for selecting the direction of acidizing after blockage occurs in loose sandstone.

Impact of Land Use Changes on Soil Erodibility in the Outer Himalayas

Land use change hurts soil characteristics such as permeability, soil texture and aggregate stability, soil erodibility etc. which make soils susceptible to erosion and degradation. The outer Himalayan region is prone to large-scale soil erosion by water owing to the vast disparity in the slope gradient, undulating relief, largely mountainous joined with high-intensity rainfall and lithological characteristics of these rocks. Soil erodibility, one of the key factors affecting the rate of erosion can be estimated by using various soil erodibility indices. In examining erodibility indices across various land use changes, it was evident that both the clay ratio (CR) and modified clay ratio (MCR) escalated as land use shifts from forest to more disturbed environments. As we transit from forest to agriculture, these ratios increased and were even more marked in the transition from forest to wasteland. The erosional behaviour as per CR and MCR in agriculture land use transitions could be arranged in the order that forest < agriculture <builtup< wastelands. Among wasteland use transitions, the high CR and MCR indicated potential challenges in soil management, while the lower CR and MCR in transitions to agriculture and forest suggested more favourable soil conditions for these specific uses. The CR and MCR ratios indicated that the lower the ratio, the more would be the clay accumulation and lesser the erosion. This information is crucial for understanding the implications of land use changes on soil erosion and health and for guiding effective land management practices in diverse ecological settings.

Undrained behavior of marine clay under one-way cyclic loading with variable confining pressure

Settlement of roads or railway caused by traffic loading has a serious effect on the safety and service performance of transport infrastructures constructed on soft marine clay. While simple cyclic triaxial test with constant confining pressure (CCP) were used in most of the previous studies, a series of cyclic triaxial tests with variable confining pressure (VCP) were carried out on normally consolidated (NC) and overconsolidated (OC) reconstituted Wenzhou soft clay in this paper to study the undrained behavior of soft marine clay due to surcharge preloading as well as cyclic traffic loading. VCP test is able to approximate the complicated stress path than CCP test caused by traffic loading. The test results indicate that NC specimens show significantly different pore water pressure (u) evolution compared with OC specimens. However, a change in the overconsolidation ratio (OCR) of OC specimens does not have a significant influence on variation of u with identical cyclic stress ratio (CSR) and total stress path (η). The slope of the effective stress path is dependent on the total stress path under which the specimen was loaded cyclically, regardless of the OCR and whether variable confining pressure was applied. The slope of the effective stress path is broadly in line with the slope of corresponding total stress path. In addition, the development of permanent axial strain (εpa) due to one-way cyclic loading was shown to depend significantly on the values of η and OCR. Both the variable confining pressure and OCR limited the strain accumulation of saturated marine clay under undrained one-way cyclic loading. Finally, the effects of η and OCR on the magnitude of εpa after 1000 loading cycles are quantified and incorporated in a power law function for the permanent deformation prediction of soft marine clay due to traffic loading.

Determination of the geophysical signature of soft-clay and hard lateritic soils and the implications on geotechnical works using electrical resistivity imaging

Understanding the geophysical signature of subsurface is quite essential in mapping site conditions for geotechnical engineering and simulating geophysical surveys, especially in coastal areas. This article presents a comparative geophysical study of topsoil (often refer as engineering layer) of soft clay deposit and hard lateritic soil to evaluate the implications on geotechnical work using electrical resistivity imaging (ERI). The results of the 2D ERI show that the hard lateritic soil produces three distinctive geological layers with the topsoil having high apparent electrical resistivity (AER) values varying between 300 Ωm–1000 Ωm and a thickness between 2.0 m – 10.0 m. The layer between the unsaturated and saturated regions has a moderate layer AER and thickness values ranging from 100 Ωm–300 Ωm and 2.5 m–9.5 m, respectively. In contrast, the saturated (weathered) layer has a low AER value (< 100Ω m), which represents the regional groundwater unit, located beneath the subsurface of a depth > 6.0 m. However, the soft clay soil shows no distinctive subsurface layers, as it is characterized by a nearly homogeneity subsurface of poor AER variability. The top-soft clay deposit has very AER values ranging from 11.0 Ωm–80 Ωm, which extends beyond 6.5 m. Higher and lower AER values noted within the overburdened topsoil of lateritic and clay extractions, respectively, were due to the accumulations of compacted clay and lateritic soil, which are very essential for geotechnical works. In addition, the geophysical signal was conspicuously attenuated in soft clay soil, which shows that soft clay soil is not a favourite target of geophysical investigation. However, the geophysical signals in hard lateritic generate a fine geo-electrical layer pattern. It was also noted that the existence of soft clay and lateritic soil decreases with depth. This kind of information is very essential in geotechnical works.

Weathering Incongruence in Mountainous Mediterranean Climates Recorded by Stream Lithium Isotope Ratios

AbstractLithium isotope ratios (δ7Li) of rivers are increasingly serving as a diagnostic of the balance between chemical and physical weathering contributions to overall landscape denudation rates. Here, we show that intermediate weathering intensities and highly enriched stream δ7Li values typically associated with lowland floodplains can also describe small upland watersheds subject to cool, wet climates. This behavior is revealed by stream δ7Li between +22.4 and +23.5‰ within a Critical Zone observatory located in the Cévennes region of southern France, where dilute stream solute concentrations and significant atmospheric deposition otherwise mask evidence of incongruence. The water‐rock reaction pathways underlying this behavior are quantified through a multicomponent, isotope‐enabled reactive transport model. Using geochemical characterization of soil profiles, bedrock, and long‐term stream samples as constraints, we evolve the simulation from an initially unweathered granite to a steady state weathering profile which reflects the balance between (a) fluid infiltration and drainage and (b) bedrock uplift and soil erosion. Enriched stream δ7Li occurs because Li is strongly incorporated into actively precipitating secondary clay phases beyond what prior laboratory experiments have suggested. Chemical weathering incongruence is maintained despite relatively slow reaction rates and moderate clay accumulation due to a combination of two factors. First, reactive primary mineral phases persist across the weathering profile and effectively “shield” the secondary clays from resolubilization due to their greater solubility. Second, the clays accumulating in the near‐surface profile are relatively mature weathering byproducts. These factors promote characteristically low total dissolved solute export from the catchment despite significant input of exogenous dust.

Effectiveness of the adsorption properties of clay in relation to the disposal of organic waste from poultry farms

This article discusses an important problem related to the disposal of organic waste from poultry farms. Bird droppings are one of the main sources of environmental pollution and consume significant resources for disposal. The search for effective and environmentally safe methods of disposal of such waste is very relevant. The article focuses on the study of the adsorption properties of a clay accumulation site. Due to the insufficient knowledge of this technology of manure burial, full-scale modeling was performed to determine the effectiveness of protecting the components of the ecological and geological environment. It is shown that under conditions of complete water saturation, the liquid fraction from the organic waste layer will easily seep through the voids and cracks of the clay layer and poison the underlying soils and groundwater. It is concluded that a clay special site alone does not provide guaranteed environmental safety of the environment. Engineering and environmental recommendations are given on the mandatory combination of this method of burial of litter with a litter made of a layer of sealed film coating.

Effect of Coal Ash Enriched Compost on Soil Chemical Properties of Ultisols

Ultisols are soils that develop in humid tropical areas and are formed due to an intensive leaching process, resulting in the accumulation of clay in the subsoil. A decrease in the chemical-physical properties of Ultisols, such as a decrease in the levels of organic C, total N, cation exchange capacity (CEC), base saturation, and on the other hand, an increase in Al saturation and soil bulk density, can occur as a result of continuous monoculture cultivation. Improving the quality of degraded soil is usually carried out by amelioration using compost. Still, the addition of compost often only has a significant effect on improving the physical properties of the soil. Coal ash in the form of fly ash-bottom ash (FABA) is a waste product from burning coal in electric steam power plants. The amount of FABA is very abundant and its utilization is minimal. FABA has an alkaline pH and contains various nutrients in varying amounts. Therefore FABA has the potential to be used as an ameliorant to improve the chemical properties of acid soils such as Ultisols. Experiments with the spread technique of compost+FABA at a dose of 50 tons/ha and in rows technique at a dose of 25 tons/ha, 15 tons/ha, and 5 tons/ha were conducted to determine the effect of the treatment on soil chemical properties. Application of FABA-enriched compost in rows technique at a dose of 25 tons/ha had a significant effect and showed the best soil chemical properties, including increasing organic C, total N, total P, available P, exch-K, -Ca, -Mg, and -Na, CEC, base saturation, and decreased Al saturation. Utilization of FABA as a soil ameliorant combined with compost can improve soil quality more effectively.

Taxonomy and genesis of soils in contrasting ecosystems of Southern Western Ghats, India

Clay minerals formed during soil formation are imprints of ecosystem functioning and pedogenic processes in landscapes. The study evaluated the variations in taxonomy, soil weathering and pedogenic changes in contrasting forest soils in the Southern Western Ghats, India. Three different forest systems with comparable soil-forming factors vis-a-vis evergreen, moist deciduous and a man-made system (rubber plantation) were evaluated for physical, chemical, morphological, and pedogenic characteristics of the related soils. Soil profiles were dug up to 1.50 m in the selected ecosystems and horizon-wise soil samples were collected. All the pedons were classified in the soil order of Ultisols and subclassified as Ustic Palehumult (evergreen forest), Ustic Haplohumult (moist deciduous forest) and Typic Haplustult (rubber plantation), respectively. The soil pH was found to be acidic in all the ecosystems ranging from 4.6 to 5.8. Chlorite, hydroxyl interlayered vermiculite (HIV), mica, kaolinite, feldspars, gibbsite and quartz dominated the mineral assemblages in the clay fractions of soils of natural forest systems. The losses of SiO2 in the non-clay fraction and corresponding enrichment of the component in the clay-sized fraction in all horizons indicated an active continuous weathering process in all the systems of this region. Clay accumulation by way of formation and translocation was highest in the lower horizons of the soils of evergreen (Bt2 at a depth range of 28–57 cm) and moist deciduous (Bt3C at a depth range of 23–150 cm) forest, whereas it was highest at Bt1 at a depth range of 15–28 cm in the plantation soil. The depth variations in the clay formations in natural and manmade forest systems provide insights into ecosystems regulated profile development under natural and man-made systems in the humid tropics, a vital information gap hitherto in soil pedogenesis of the humid tropics. Such pedogenic assessments along with the factors responsible for such modifications would provide important inputs in developing soil health management strategies in the humid tropics.

THE EFFECT APPLICATION THE EFFECT APPLICATION OF FISH WASTE LIQUID FERTILIZER AND ACTIVE POWDER OF AHL IN IMPROVING NUTRIENTS CONTENT OF N AND P ON ALFISOL AND YIELD OF TOMATO

Alfisol is one of soil type which is a high accumulation of clay on above horizons. This conditions result in a high soil compaction which cause difficulty penetration of plant root. Moreover, this type of soil is low organic matter resulted in low nutrients content such as Nitrogen, Phosphorus and Potassium. A research had been conducted at village of East Penfui, District of Kupang since May to August 2022. Main aim of the research was to determine effect various concentration of fish waste liquid fertilizer and active powder of AHL in improving levels contain of Phosphorus, and Potassium and yield of tomato. The research was designed Completed Random Designed with three replications. Treatments of the research were control (LO), 15 ml liquid fertilizer of fish waste (L1), 25 ml liquid fertilizer of fish waste (L2), 35 ml liquid fertilizer of fish waste (L3), 45 ml liquid fertilizer of fish waste (L4), 15 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL, 25 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L6), 35 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L7), and 45 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L8). Parameters measurements were available of Phosphorus, total Nitrogen and Yield of Tomato. All data were analyzed by using Analysis of Variant followed by Duncan Multiple Range Test at 5% level. Result of the research showed that application of 45 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L8) resulted significantly highest contents of available of Phosphorus (33.41 ppm), total Nitroegn (1.23%). Meanwhile, application of 25 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L6) resulted a highest of of tomato by 526.22 g per plant which is not significantly different to application of 45 ml liquid fertilizer of fish waste (L5) + 0.2 g active powder of AHL (L8)&#x0D; &#x0D;

Low amplitude strain accumulation model for natural soft clays below railways

An improved constitutive model for strain accumulation of natural clays under undrained cyclic loading is presented. The proposed model includes a formulation for the non-linear small-strain stiffness in the overconsolidated regime, along with a modified hardening law for cyclic accumulation to improve the tracking of strain accumulation at small stress amplitudes. To calibrate and validate the proposed model, a series of laboratory tests were conducted to study the cyclic response of natural Swedish clays, the effect of loading amplitude and pre-shearing history. Good agreement between predicted and measured accumulated axial strains and excess pore water pressures was obtained with different loading amplitudes. The findings reveal that the undrained pre-shearing has a substantial impact on the rate of accumulated strain, with pre-sheared samples exhibiting lower resistance values. The proposed and validated model opens up possibilities to study the monotonic and non-monotonic quasi-static response of soft clays below railway embankments over the lifetime of the structure, i.e. including the effects of construction, operation and decommissioning.

An empirical formula for the accumulative deformation of saturated clay under different cyclic loading frequencies

Road and subway tunnels in soft clay soils subjected to traffic loading often cause lager settlement. It can pose danger to the surrounding buildings and structures. Hence, it is necessary for engineers to correctly predict the long-term deformation of saturated clay foundations under cyclic loading. In this paper, a series of dynamic triaxial tests were carried out on Nanning clay to investigate the effect of loading frequency and cyclic stress on axial strain accumulation of clay under undrained condition. Results show that loading frequency has a great effect on the axial strain accumulation of clay. Based on the experimental results, an empirical formula for calculating the accumulated deformation of saturated clay under cyclic loading was presented.

Holocene climate dynamics and ecological responses in Kaas Plateau, Western Ghats, India: Evidence from lacustrine deposits

The Kaas lake is one of the unique sedimentary basins in the Northern region of the Western Ghats escarpment of India and preserves paleoclimate signals of the Holocene in its cover sequence over the lateritic basement. The signatures preserved in the lacustrine deposits, such as pollen, non-pollen palynomorphs, diatoms, and geochemistry of the sediments, were decoded and used to reconstruct the Holocene environmental changes of the Kaas Plateau in the Western Ghats. The main stages in the lake's evolution indicate the following: (1) low nutrient level and strongly changeable water levels in the early Holocene, (2) persistence of the oligotrophic state of the lake up to the last 2000 yr, and (3) strong cultural eutrophication of the lake in the recent period (c. 1000 years). The localized depression or a seasonal-lake favoured freshwater accumulation since 8.0 kyr BP and was probably dried sometimes after 2.0 kyr BP. A late Holocene peak of planktonic diatom and high organic recovery at the top level in the recent past (c. 1000 years) represents an event of eutrophication, possibly due to human impact. Being a seasonal lake, the plateau surface allowed clay accumulation with an extremely slow rate of 2.5 cm/10 kyr. Diatoms, pollen, and non-pollen palynomorphs together showed periodic fluctuations in lake hydrology, which was probably in response to climate-controlled vegetation on the Kaas Plateau. The diatom and sediment anomalies point to an ecological shift towards the mid–Holocene, supporting the hypothesis of increased Southwest Monsoons during the early Holocene around 8.0 kyr BP and the relative weakening of Northeast Monsoon after 2.5 kyr BP.

Meteoric 10Be as a tracer of soil redistribution rates and reconstruction tool of loess–mantled soils (SW, Poland)

Loess deposits are terrestrial archives that record progressive deposition and erosion events of varying intensities. Data on long-term erosion rates are crucial for tracking changes in the stability of a loess mantle and reconstructing the evolution of loess-enriched soils. We used meteoric 10Be to i) define the factors responsible for its distribution along the profile, ii) determine long-term erosion rates in loess-enriched polygenetic soils characterised by illuviation processes, and iii) evaluate initial soil thickness and stability over time. Distribution of meteoric 10Be along the soil profiles was mainly driven by its translocation with clay particles and accumulation in the illuvial horizons. However, in some cases (loess over serpentinite), the highest meteoric 10Be content was measured in the C horizons which may be related to the longer exposure of serpentinite to meteoric 10Be deposition before the occurrence of a major loess accumulation event. The estimated long-term erosion rates greatly depend on the assumed environmental settings and were in the range of about 0.1–3 t ha−1 yr−1. Based on the soil redistribution rates, we reconstructed the removed loess layer which was from a few dm to about 3 m. The results indicate four main soil evolutionary phases: a) pre-exposure of sediments to meteoric 10Be accumulation; b) formation of thick loess mantles during the Last Glacial Maximum; c) erosion events between 21 and 11.6 ka that significantly shallowed the initial loess mantles; d) pedogenesis (with subsoil clay accumulation) in the Holocene within the thinner relicts of the former Late Pleistocene loess mantle followed by a recent and strong erosional phase due to human impact. These phases are also believed to have occurred in several other areas of Central Europe.

Late Barremian–Aptian paleoenvironmental variations and OAE1a environmental effect in the eastern Crimea

The early Aptian Oceanic Anoxic Event 1a (OAE1a, or Selli Event) is widely known from many oceanic and inland sections as an interval of enhanced accumulation of sediments rich in total organic carbon (TOC), associated with the turnover in the global carbon budget and dramatic biotic variations. Our multidisciplinary study of the upper Barremian to lower upper Aptian deposits from the eastern part of Crimean Peninsula allowed us to confirm the presence of a layer that correlates to OAE1a and revealed significant reorganization in the planktonic and benthic foraminifera, nannofossils, ostracod and terrestrial plant communities at this level. The low-calcareous OAE1a deposits from the eastern Crimea lack in TOC that is not typical sedimentological response to this critical event. The OAE1a onset was associated with a nannoconid crisis, occurrence of low-abundance Hedbergella planktonic foraminifera, increased abundance of benthic foraminifera and ostracods and the bloom of Classopolis on the adjacent land. The calcareous microplankton biota was highly oppressed during OAE1a up to total elimination in the core of the event. Benthic assemblages indicate the occurrence of dysoxic conditions at the sea-floor. The absence of organic matter in the deposits of the OAE1a interval points to the low basinal biotic productivity and low input of terrestrial organic matter. We suggest that oligotrophication of the basin was related to the transgressive pulse, which led to small-scale landward moving of the coastal line barriered by coastal highland. The hot arid climatic conditions indicated by terrestrial plants, prevented the supply of nutrients and terrestrial organic matter into the basin that caused low algal and bacterial productivity and prevented accumulation of TOC-rich sediments. The termination of OAE1a coincides with the occurrence of warm humid climate and erosion of ephemeral coastal highland, more likely, built up by soft clayey sediments. The transit restoration of the normal marine biota in the early late Aptian was interrupted in the middle late Aptian by new long-lived regression led to enhanced terrestrial runoff and, possibly, fresh water input killed marine biota and caused the accumulation of low-calcareous clay.

P-y based approach to predicting the response of monopile embedded in soft clay under long-term cyclic loading

Offshore wind turbines (OWTs) are subjected to environmental loadings such as those induced by waves or wind typically comprising up to millions of cycles (i.e., high-cycle loading). To evaluate the performance of OWTs during a lifetime cycle, this study proposed a p-y based approach to predict monopile response subjected to a long-term cyclic loading. A cyclic loading may cause an accumulation of strain and a built-up of excess pore water pressure under undrained conditions, accompanied by a corresponding reduction of stiffness and shear strength in soft marine clay. In the proposed procedure, the cyclic degradation and strain accumulation of soft clay is considered by a generalized empirical model given the soil reaction calculated from p-y analysis for a prescribed loading condition on the pile. Afterward, the response of pile subjected to a long-term cyclic loading is predicted by modifying the preselected p-y curve by p-multiplier and y-multiplier to take account for the cyclic degradation and strain accumulation, respectively. The proposed approach is validated by three centrifuge tests on a monopile in soft clay. The simulation results are in good accordance with the measurements in terms of pile displacement and bending moment versus number of applied cycles. Therefore, the proposed approach is feasible to predict the long-term pile response subjected to high-cycle loading. Moreover, it is easily implemented in the widely used p-y approach.

Plastic shakedown limit of compacted clay: Experiments and predicted model

The moisture in the soils of subgrade varies with the changes in climate and the depth from the subgrade surface, which can significantly affect the strength and stiffness behaviour of subgrade soils. In this study, a series of cyclic triaxial tests on compacted clay were first conducted to investigate the effect of moisture content and confining pressure on the plastic shakedown limit of soils. The strain accumulation of compacted clay is analysed in detail, and then, the cyclic stress amplitude corresponding to the plastic shakedown limit, σ¯cycsh, is determined based on the approach proposed by Chen et al. (2019). Subsequently, the effect of the initial matric suction and confining pressure on σ¯cycsh is studied. σ¯cycsh increases linearly with increasing initial matric suction and confining pressure. By following the framework of a strength equation for unsaturated soil, the predicted model of σ¯cycsh under the coupling action of confining pressure and initial matric suction is proposed, in which only three measurable parameters are needed. The accuracy of the predicted model is effectively validated by the experimental data, and the results from the proposed model are in reasonable agreement with the measured data.

Micromorphological features of medieval cultural layers formed in different environmental backgrounds

This research compares results of micromorphological case studies conducted on four early medieval archaeological sites with differentiated spatialization of human impacts and a varied craft production located in different background environments: humid climate, subzone of mixed forests, floodplain of the Dnieper River (Gnezdovo site); semi-humid climate, subzone of forest-steppe, Middle Volga region (Muromsky Gorodok and Malaya Ryazan’ sites); arid climate, cold desert of the Aral region, ancient delta-alluvial plain of the Syr-Darya River (Dzhankent site). Micromorphological studies of habitation deposits revealed clear geographical and geochemical regularities in the occurrence of geogenic (soil, sedimentary and post-sedimentary) features. Intrasoil migration and accumulation of clay and coarser silicate material in textural pedofeatures were described in cultural layers of sites located in forest and the forest-steppe zones. An anthropogenic input of phosphates provokes simultaneous migration and illuvial accumulation of phosphates and clay. In the habitation deposits in steppe landscapes with calcareous lithology, the key background soil process is redistribution and intrasoil accumulation of calcium carbonates. In the alluvial desert landscape, major soil processes are accumulation of gypsum and readily soluble salts. All layers are or were affected by at least some seasonal over-moisturizing that resulted in a variety of redoximorphic features depending on their palaeo- and/or contemporary water regime. The high variety of anthropogenic processes and corresponding microfeatures was grouped as follows: (1) input, output, turbation, compaction; (2) neoformation and migration; (3) pyrogenic processes (products); technological processes (products). The set of anthropogenic features records past human impact in the locality. The higher the variety of anthropogenic features and their general abundance is, the more intensive and variable the human impact which had occurred in the past. At the same time, the occurrence of certain anthropogenic features may indicate not only human-related processes of their formation (or input), but also a contemporary soil environment. This environment can be favorable, or, in the opposite, deteriorative for earlier formed anthropogenic features.

A New Look at Cenozoic Fossil Wood from Thailand

Thailand contains two notable fossil forest regions. Pleistocene fluvial sediments in the Tak region in the northern highlands contain silicified trunks of large trees. Deposits in the Khorat Plateau in northeast Thailand contain a multitude of wood fossils that span a probable age range of Miocene to Pleistocene. At Ban Tak fossil logs are primarily mineralized with crystalline quartz. Incomplete mineralization is characteristic of the Tak wood, with intercellular spaces commonly remaining open. The resulting permeability allows penetration of moisture, and allows introduction of microbes and the accumulation of clays, iron oxides, soluble salts and other materials that may cause discoloration and deterioration. Hydration swelling of these components results in stress. Excavation of the huge logs means that they occupy topographically low positions prone to flooding during the monsoon season. These factors make the fossils vulnerable to weathering. A variety of methods have been employed in attempts to reduce the damage, including the construction of various styles of shelters to protect the fossil logs from direct precipitation. At Khorat, compositions of individual specimens range from pure quartz and pure opal to mixtures of the two polymorphs. Many specimens are preserved indoors in the Khorat Fossil Museum in Mueang Nakhon Ratchasima District, both as indoor exhibits and as outdoor displays in a garden plaza. The environmental complexities at the Tak and Khorat fossil wood localities challenge conservators, but their creative attempts provide useful lessons for future preservation efforts. Our report describes the geologic setting and our research mineralogy of specimens at both localities, and discusses conservation strategies.

Morphophysical and Nutrient Characteristics of Degraded Soils in Sta. Rita, Samar, Philippines

The productivity of degraded soils greatly depends on a good understanding of their characteristics. Hence, the study was conducted to determine the morphological, physical and chemical characteristics of degraded soils in Sta. Rita, Samar, Philippines. Four representative soil profiles located in different physiographic positions were examined, characterized and sampled. The examination was conducted using a pit measuring approximately 1-m wide and 1-m depth. Soil samples were collected from each horizon, processed and subjected to field and laboratory analyses. Results showed that the soils were derived from sedimentary rocks (i.e., shale). Well-developed soils were found on the summit and foot slope position (horizon sequence: Ap-Bt-BC-C), while moderately developed soils were obtained in the middle slope position (horizon sequence: Ah-Bt-C). Soils had a clayey texture with moderate bulk density, porosity and water holding capacity. They were friable to firm when moist, but plastic and sticky when wet. The soils were highly acidic (soil pH close to 5.0). They had a moderate amount of organic matter, low total nitrogen (N) and low available phosphorus (P); all of which had decreased amounts with soil depth. Exchangeable bases (calcium, magnesium, potassium and sodium) were high in most soil profiles. Thus, N and P fertilization and organic matter addition are highly recommended to increase the productivity of these degraded soils. Moreover, the soils were classified as Typic Hapludalfs or Haplic Luvisols because of their development degree. They were mature with the presence of an argillic horizon (B horizon with high clay accumulation) and high base saturation.

The Pedogenesis of Inceptisols on Southeast Toposequence of Mount Manglayang in West Java, Indonesia

DOI:10.17014/ijog.9.2.195-208The most potential soil order in Indonesia is dominated by Inceptisols, whereas the topography combined with a climatic factor are the main factors to regulate pedogenetic process. This research was intended to determine the pedogenetic process and soil development on various terrain positions at the southeast toposequence of Mount Manglayang areas that have hilly topography. The researched area was 28.83 ha. Based on those conditions, this research aims to study the pedogenetic process and soil development in the southeast slope toposequence of Mount Manglayang, the relationship between the physical, chemical, and mineralogical soil properties, the soil classification to family level based on soil taxonomy, National Soil Classification, and FAO soil classification systems. This research used survey, descriptive, and comparative methods. The result showed that the pedogenetic processes identified were the formation of B horizon through clay accumulation, soil colour, and soil structure development, and the formation of amorphous kaolinite and halloysite minerals. Based on soil taxonomy, the soil were classified as Fluventic Humudepts, coarse-loamy, kaolinitic, isohyperthermic at the upper slope and Fluventic Dystrudepts, fineloamy, kaolinitic, isohyperthermic at the middle and lower slopes. According to National Soil Classification, the soil is Humic Cambisol at the upper slope, Distric Cambisol at the middle slope, and Cromic Cambisol at the lower slope. FAO classified the soil as Umbric Cambisols at the upper slope and Dystric Cambisols at the middle and lower slopes.