Silt

Environmental sustainability of animal agriculture is strongly dependent upon development of approaches to minimize the potential environmental impacts of applying animal manures. The excess manure and its nutrients (primarily phosphorus) in intensive animal production regions may need to be exported to other areas to comply with increased regulations on manure management. In our previous study we generated a variety of granulated products from poultry litter to achieve export of excess litter from the southwestern Ozarks, AR, USA. Our objective in the present study was to determine the effect of the application of poultry litter and granulated litter products on phosphorus (P), arsenic (As), copper (Cu) and zinc (Zn) dynamics in two Arkansas soils (Dewitt silt loam and Hector sandy loam). Poultry litter and granulated products were mixed with the surface horizon (0-15 cm) of soils at two application rates: P-based (100 kg total P per hectare) and N-based (160 kg plant-available N per hectare). Soil-litter mixtures were incubated at 25°C for 21 days. Sub-samples were removed at 1, 7 and 21 days to determine the solubility and availability of P, As, Cu and Zn in soils. Results suggest that when litter was applied at 100 kg total P per hectare, contents of P, As, Cu and Zn were significantly greater in the soils amended with litter and granulated products than in the control (soil alone). However, the contents of P, As, Cu and Zn did not significantly differ in the soils amended with either normal litter or granulated litter products at total P or plant-available N-based application rates. This suggests that poultry litter granulation is a sound management practice that can be used to reduce concerns with fresh litter transport and potentially improve P and trace element balances in intensive poultry production regions, especially when applied on a plant-available N basis.

Non-point source (NPS) pollution, unlike point source pollution from domestic and industrial wastewater treatment plants, comes from many diffuse sources. It is caused by the movement of rainfall or snowmelt that picks up and carries pollutants to receiving waters. NPS pollution represents the main cause of contamination of many rivers, streams and other water bodies of many developed countries. Best management practices (BMPs) are intended to reduce NPS pollutants, particularly those from highway runoff, e.g., oil and grit separators, grassed swales, vegetated filter strips, retention ponds, and catch basin inserts. A catch basin insert (CBIs) is a device that reduces stormwater pollution from runoff, without requiring any land use because it is typically mounted within a catch basin. In this study, six commercially-available CBIs were installed and monitored at sites along highways in Westchester County that are under the jurisdiction of the New York State Department of Transporta...

Quaternary sedimentary successions are described from the Linda Valley, a small valley in western Tasmania that was dammed by ice during Early and Middle Pleistocene glaciations. Mapping and logging of exposures suggest that an orderly sequence of deposits formed during ice incursion, occupation and withdrawal from tributary valleys. Four principal sediment assemblages record different stages of ice occupation in the valley. As the glacier advanced, a proglacial, lacustrine sediment assemblage dominated by laminated silts and muds deposited from suspension accumulated in front of the glacier. A subglacial sediment assemblage consisting of deformed lacustrine deposits and lodgement till records the overriding of lake-bottom sediments as the glacier advanced up the valley into the proglacial lake. As the glacier withdrew from the valley, a supraglacial sediment assemblage of diamict, gravel, sand and silt facies formed on melting ice in the upper part of the valley. A lacustrine regression in the supraglacial assemblage is inferred on the basis of a change from deposits mainly resulting from suspension in a subaqueous setting to relatively thin and laterally discontinuous laminated sediments, occurrence of clastic dykes, and increasing complexity of the geometry of deposits that indicate deposition in a subaerial setting. A deltaic sediment assemblage deposited during the final stage of ice withdrawal from the valley consists of steeply dipping diamict and normally graded gravel facies formed on delta foresets by subaqueous sediment gravity flows. The sediment source for the delta, which prograded toward the retreating ice margin, was the supraglacial sediment assemblage previously deposited in the upper part of the valley. A depositional model developed from the study of the Linda Valley may be applicable to other alpine glaciated areas where glaciers flowed through or terminated in medium- to high-relief topography.

In this research, waste stone sludge obtained from slab stone processing and waste silt from aggregate washing plants were recycled to manufacture artificial aggregate. Fine-powdered stone sludge was mixed with waste silt of larger particle size; vibratory compaction was applied for good water permeability, resulting in a smaller amount of solidifying agent being used. For the densified packing used in this study, the mix proportion of waste stone sludge to waste silt was 35:50, which produced artificial aggregate of more compact structure with water absorption rate below 0.1%. In addition, applying vibratory compaction of 33.3 Hz to the artificial aggregate and curing for 28 days doubled the compressive strength to above 29.4 MPa. Hence, recycling of waste stone sludge and waste silt for the production of artificial aggregate not only offers a feasible substitute for sand and stone, but also an ecological alternative to waste management of sludge and silt.

Sur les hautes terres malgaches, le bassin d'Antsirabe, d'origine tectonique, présente un socle cristallin faillé, bordé à l'ouest par des édifices volcaniques récents (Vakinankaratra). Le bassin sédimentaire présente deux surfaces planes, étagées et légèrement inclinées vers le sud, qui ont été considérées jusqu'alors comme témoignant chacune d'un remplissage lacustre. Les séries stratigraphiques reconnues présentent, sur le socle ou ses altérites, deux corps sédimentaires remarquables. A la base, sur une dizaine de mètres d'épaisseur, une série fluvio-palustre de plaine d'inondation, où sables, limons et graviers alternent avec des niveaux tourbeux décimétriques, au nombre maximum reconnu de sept sur une même verticale. Au-dessus, une couverture de cinérites, fine au sud-est et plus grossière au nord-ouest, atteint généralement vingt mètres d'épaisseur. Les datations 14 C obtenues placent les alluvions fluviopalustres entre 35 000 BP et 14 400 BP. La série volcanique explosive majeure est donc plus récente que 14 400 BP. Elle aurait duré 6 000 ans. La vitesse moyenne de dissection de ces matériaux tendres peut être relativement bien cernée. Le comblement du bassin d'Antsirabe n'est donc pas d'origine lacustre, de tels sédiments n'ayant été reconnus que ponctuellement à la base de la série, le long de la faille du Mandray. Le remplissage du bassin d'Antsirabe constitue de ce fait une archive sédimentaire remarquable correspondant aux stades isotopiques 2 et 3 d'une plus grande fiabilité que les sédiments de lacs de cratère proches.

A numerical code for the prediction of the settlement of pile groups and piled rafts is presented. The code is based on the interaction factors method; the non-linearity is simulated as suggested by Caputo and Viggiani, that is, concentrating it at the pile±soil interface. In the linear range, the accuracy is checked against known benchmark solutions. A standard procedure, based on the results of load tests on single piles, is suggested for the evaluation of soil properties and for the implementation of the analysis in real cases. Nineteen well-documented case histories are then analysed, calculating for each of them a linear elastic, an equivalent linear elastic and a non-linear solution. Five out of the 19 cases are illustrated in some detail, to allow a deeper insight into the procedure. In all but one of the analysed cases the predicted values of the average settlement are within AE20% of the observed values. The maximum differential settlement is predicted with slightly lesser accuracy. For foundations characterized by a relatively high safety factor, linear and non-linear analyses are essentially equivalent. Some evidence suggests that the low-strain shear modulus, obtained by in situ shear wave velocity measurements, can be successfully employed in the prediction of the settlement. When the safety factor is low, the consideration of nonlinearity becomes mandatory.

In the present day construction industry in developing countries, concrete has emerged as the most common building material. Hence careful consideration must be given to factors that affect its strength. For sand having above 3.4% of clay content used in a 1:1: 2 (M-25) mix of concrete resulted in the production of concrete with compressive strength less than 25 N/mm2.Therefore, this work was conducted to investigate the amount of cement needed for sand samples with varying amount of clay/silt cement from 0% to 10% to produce concrete with compressive strength not less than 25 N/mm2 for mix 1:1:2.The sieved clay/silt is added to each of the parts of the washed sand from 1% to 10% by weight of the sand. The amount of cement necessary to be added to each part of the sand with varying cement content of clay/silt 1% to 10%, so as to achieve minimum strength of 25 N/mm2 for the mix ratio 1:1:2 was determined. It was discovered that the higher the clay/silt content, the compressive strength of concrete is decreases. It is concluded that the higher amount of cement dosage is needed to maintain the compressive strength of concrete.

To estimate the unsaturated soil hydraulic conductivity of a silty soil, an insertion tensiometer has been used for measuring its suction corresponding to different water contents. These suction values have been used for developing the soil-water characteristic curve (SWCC). The obtained SWCC has been compared with the trends predicted by various fits available in the literature. Further, with the help of the obtained SWCC, the unsaturated soil hydraulic conductivity has been estimated. The study demonstrates the usefulness of insertion tensiometers for measuring soil suction and for estimating its hydraulic conductivity.

A revised textural classi"cation of gravel-free muddy sediments based on the adaptation, modi"cation and expansion of previous schemes using ternary plots is presented. The new approach increases the range of application and the environmental sensitivity of textural sediment classi"cation. In the case of simple two-component sand/mud mixtures, six sediment types based on mud (silt#clay) or sand content are distinguished: sand ((5% mud), slightly muddy sand (5}25% mud), muddy sand (25}50% mud), sandy mud (50}75% mud), slightly sandy mud (75}95% mud), and mud ('95% mud). The class names accurately describe a sediment within de"ned textural limits, and the scheme can thus be used to divide a depositional environment into textural sub-environments or facies. By diagonally subdividing the two-component system, a more complex three-component classi"cation scheme based on sand/silt/clay ratios has been generated. In this scheme, 25 sediment classes are distinguished, each de"ned by a generic name and a letter}number code. It not only allows a more detailed textural subdivision of sedimentary environments than the two-component system, but also incorporates a genetic element by distinguishing between di!erent hydrodynamic regimes. Thus, sandier and more silty sediments, re#ecting deposition under higher energy conditions, are progressively segregated from muddier and more clayey sediments which re#ect deposition under lower energy conditions. This is illustrated with examples from a variety of intertidal and open shelf environments. In addition, the letter}number codes can be used to label sediment facies maps, annotate stratigraphic sections and structure data banks. The two classi"cation schemes are complementary, o!ering two levels of resolution and ful"lling the basic requirements of practicality, ease of use and global applicability.

Guidance is provided for geotechnical engineers designing civil engineering works in silty soils based on a detailed characterisation of a glaciomarine silt from Os in western Norway. It was found that these soils are susceptible to disturbance by good quality fixed piston tube sampling and care needs to be taken when using laboratory derived design parameters, particularly for consolidation and shear strength properties. A technique for assessing sample disturbance using shear wave velocity and suction measurements proved promising. Conventional techniques for determining soil strength from triaxial tests in silt are inappropriate due to the dilational nature of the material and more reliable and logical strength estimates can be made from a limiting strain criterion. Field vane data should be used with caution as measured strength, particularly remoulded values, may be high and it seems more reliable parameters can be derived from CPTU tests. One dimensional consolidation and creep of these silts can be modelled successfully by the well-known Janbu formulation. The behaviour of the Os silts does not fit easily into classical soil mechanics and published frameworks for soft soils. It seems the material is of "transitional" type and this work adds to the database of such soils which includes other natural silts and gap graded soils. For future work it is recommended that larger sample tubes (say 75 mm) with a very sharp cutting edge should be used in parallel with in situ CPTU testing.

. Gullies locally termed dongas are a characteristic feature of the landscape in central KwaZulu-Natal and are highly associated with widespread, stratified colluvial sediments and the buried palaeosols that have formed in this material. Research objectives were to find out which sediment property or properties contribute most to the vulnerability of the colluvium to gully erosion; to study the erosion susceptibility of the sequence of buried stratigraphic layers and palaeosols; and to improve understanding of the relationship between erosion susceptibility of the colluvial layers and palaeosols and their disposition in the landscape. Materials from several colluvial layers and palaeosols exposed in the donga sidewall of the Dabekazi donga, 13 km north of Nqutu in central KwaZulu-Natal, were subjected to chemical and mineralogical analyses, several dispersion and erodibility tests and were characterized physically. Exchangeable sodium Ž . percentages ESP ranged from 0% to 23% and the dispersivity and erodibility tests revealed a range of dispersion potential and erodibility across the sequence of colluvial layers and palaeosols. However, a poor correlation was found between the results of different dispersion tests, as well as between dispersion tests and dispersion-related properties. Dispersion tests showed significant correlation with silt content. An erodibility test using a flume showed very strong correlation with Ž . Ž . electrical conductivity EC and sodium adsorption ratio SAR of the saturated paste extract and ESP values. The plasticity index ranged from 0% to 0.23 and estimated hydraulic conductivities ranged from 33 to 0.7 mrday. High correlation with ESP and EC suggests that dispersion plays an important role in the erodibility of the materials under conditions of short duration, turbulent water ) Corresponding author. 0341-8162r00r$ -see front matter q 2000 Published by Elsevier Science B.V. All rights reserved.

This paper presents the first results of a 14 C and optical luminescence dating project on extensive alluvial silt formations in the southern Anti Atlas Mountains in southern Morocco. The silts comprise three members: basal silts, an inter-silt fluvial gravel member and a top silt member and are incised by the rivers. Top silt dates are: 11 340-11 940, 12 670-13 130 cal. yr BP, and 10.6 ± 0.7 ka (OSL). OSL dates for the inter-silt gravels are 29.6 ± 2.0 ka and for the bottom silts is 45.0 ± 3.7 ka. The sediments correlate with Soltanian stratigraphies known elsewhere in Morocco. To cite this article: M. Thorp et al., C. R. Geoscience 334 (2002) 903-908.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS Morocco / Anti Atlas / Upper Pleistocene / alluvial sediments / dating Résumé -Datation des sédiments alluviaux du Pléistocène supérieur du versant sud de l'Anti-Atlas, Maroc. Cet article présente les premiers résultats d'un projet de datation au carbone 14 et par luminescence optique des vastes formations alluviales limoneuses du Sud de l'Anti-Atlas, au Maroc. Les limons comportent trois membres : limon basal, membre fluvial graveleux inter-limon et membre limoneux sommital, tous incisés par les rivières. Les âges des silts sommitaux sont : 11 340-11 940 ans BP cal., 12 670-13 130 ans BP cal. et 106 ± 0,7 ka (OSL). Les âges (OSL) sont, pour le membre inter-limon, 29,6 ± 2,0 ka et, pour le silt basal, 45,5 ± 3,7 ka. Les sédiments peuvent être corrélés avec les formations soltaniennes, connues ailleurs au Maroc. Pour citer cet article : M. Thorp et al., C. R. Geoscience 334 (2002) 903-908.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS Maroc / Anti-Atlas / Pléistocène supérieur / sédiments alluviaux / datation

The Lake Lahontan basin has been the site of numerous pluvial lakes during the Pleistocene. We address the question of whether or not the highest remnant shoreline features around the perimeter of the lake were produced during the most recent Ž . Ž . Sehoo highstand ; 13 ka , the penultimate Eetza highstand ; 140-280 ka , or both. To do so, we document surficial characteristics, morphologic preservation, and soil development on multiple Sehoo beach barriers in the Jessup embayment to define the range in characteristics displayed by latest Pleistocene beach features. Sehoo barriers generally exhibit original constructional morphology that has been little modified by erosion. Soils developed on Sehoo barriers are generally thin and weakly developed and are strongly influenced by the introduction of eolian fines into the predominately clast-supported coarse beach gravels. Similar observations from 13 other highstand barriers and from seven older-than-latest Pleistocene paleosols located around the basin form the basis for a regional comparison. Based on similar characteristics, including the degree of morphologic preservation and weak soil development, we conclude that the widespread and nearly continuous high shoreline around the perimeter of Lake Lahontan dates from the most recent major lake cycle in all areas except in the Walker Lake subbasin. In the Walker Lake subbasin, isolated early to middle Pleistocene lacustrine outcrops and landforms are elevated as much as 70 m above the late Pleistocene limit, but are differentiated by their degraded form and lack of continuity around the subbasin. Similar unambiguous landforms were not observed elsewhere and at similar elevations in the northern subbasins of Lake Lahontan. q

Analysis of the sensitivity of predictions of slope instability to input data and model uncertainties provides a rationale for targeted site investigation and iterative refinement of geotechnical models. However, sensitivity methods based on local derivatives do not reflect model behaviour over the whole range of input variables, whereas methods based on standardised regression or correlation coefficients cannot detect non-linear and non-monotonic relationships between model input and output. Variance-based sensitivity analysis (VBSA) provides a global, model-independent sensitivity measure. The approach is demonstrated using the Combined Hydrology and Stability Model (CHASM) and is applicable to a wide variety of computer models. The method of Sobol', assuming independence between input variables, was used to identify interactions between model input variables, whilst replicated Latin Hypercube Sampling (LHS) is used to investigate the effects of statistical dependence between the input variables. The SIMLAB software was used, both to generate the input sample and to calculate the sensitivity indices. The analysis provided quantified evidence of well-known sensitivities as well demonstrating how uncertainty in slope failure during rainfall is, for the examples tested here, more attributable to uncertainty in the soil strength than to uncertainty in the rainfall. r (N.A.S. Hamm), [email protected] (J.W. Hall), [email protected] (M.G. Anderson).

Oedometric mechanical compaction tests were performed on brine-saturated synthetic samples consisting of silt-clay mixtures to study changes in microfabric and rock properties as a function of effective stress. The silt consisted of crushed quartz (w100%) with grain size range between 4 and 40 mm, whereas the clay consisted of 81% kaolinite, 14% mica/illite and 5% microcline of grain size between 0.4 and 30 mm.

A complex of geophysical methods were used to investigate a small karst area aimed at the production of detailed geological mapping, to confirm geological localization of known sinkholes, and to find possible continuations of caves and voids below the surface. The dipole electromagnetic profiling and radiometric mapping (the gamma-ray spectrometry method) were applied to determine the spatial distribution of hard carbonate rocks and weathered valley-fill sediments. Detailed high-definition magnetometry was carried out at selected sites in the studied region with the aim of distinguishing between sinkholes and man-made lime-kilns, pits where limestone was heated and transformed into lime. The microgravity and the electrical-resistivity tomography (ERT) methods were used to create high-resolution images of the underground cave. The results of ERT and the geological survey were used as an initial model for gravity modeling. Subsurface cavities of various sizes are contrasting geophysical objects, and the electrical resistivity can range from very conductive to relatively resistive depending on the composition of the filling materials. The interpretation of resistivity properties is not always straightforward. We must distinguish air-filled (high-resistivity) and loamy water-filled (low-resistivity) cavities and fractures. The combined geophysical methodology permits us to determine a more accurate near-surface geological model, in our case the parallel interpretation of a strong conductive anomaly in the ERT inversion and a predominant density decrease in the gravity modelling yield the presence of cavities at depths approximately of 50 to 60 m below the surface.

A complex of geophysical methods were used to investigate a small karst area aimed at the production of detailed geological mapping, to confirm geological localization of known sinkholes, and to find possible continuations of caves and voids below the surface. The dipole electromagnetic profiling and radiometric mapping (the gamma-ray spectrometry method) were applied to determine the spatial distribution of hard carbonate rocks and weathered valley-fill sediments. Detailed high-definition magnetometry was carried out at selected sites in the studied region with the aim of distinguishing between sinkholes and man-made lime-kilns, pits where limestone was heated and transformed into lime. The microgravity and the electrical-resistivity tomography (ERT) methods were used to create high-resolution images of the underground cave. The results of ERT and the geological survey were used as an initial model for gravity modeling. Subsurface cavities of various sizes are contrasting geophysical objects, and the electrical resistivity can range from very conductive to relatively resistive depending on the composition of the filling materials. The interpretation of resistivity properties is not always straightforward. We must distinguish air-filled (high-resistivity) and loamy water-filled (low-resistivity) cavities and fractures. The combined geophysical methodology permits us to determine a more accurate near-surface geological model, in our case the parallel interpretation of a strong conductive anomaly in the ERT inversion and a predominant density decrease in the gravity modelling yield the presence of cavities at depths approximately of 50 to 60 m below the surface.

It was assumed that protected soil organic matter SOM inside small macroaggregates is Ž. Ž y3. indicated by the enriched labile fraction ELF 2.07-2.22 g cm of aggregated fine silt. The ELF should be of fungal origin and sensitively reflect management effects on SOM. To test these Ž. hypotheses, we have isolated ELF from mollic epipedons 0-10 cm of Chernozems under native steppe, meadow, forest, and long-term arable land. The ELF was characterized by C, N, amino-sugar and 13 C-CPrMAS-NMR measurements. The results showed that the glucosamineto-muramic acid ratio was higher in ELF than in other aggregate-density fractions. This indicated that microbial residues in the ELF, stronger than in other fractions, are of fungal origin. The remaining SOM composition as identified by 13 C-CPrMAS-NMR spectroscopy was not different from that of the other density fractions. The ELF was therefore enriched in fungal debris but it did not solely consist of microbial N. Nevertheless, ELF seemed to reflect land-use effects on SOM. The C and N loss from ELF due to arable land use or afforestation resulted in a relative preservation of its bacterial-derived muramic acid relative to glucosamine, however, due to the lack of independent replicates such effects could not be statistically evaluated.

Assessment of two methods for the determination of organic carbon (OC) in the silt-clay fraction of marine sediment has been carried out with reference to values from the decarbonated sediment, using a CHN analyzer. Although the mass loss on ignition (MLOI) was lower at 440°C than at 550°C or 600°C, the OC contents were overestimated by a factor near three from these results, and the rank order of OC in dierent sediments was not reproduced. Wet oxidation using the revised Walkley± Black titration overestimated OC in anoxic sediments, but gave an underestimation for oxic sediment. The need for sediment reference material with certi®ed OC content is stressed.

This study documents the stratigraphic and palaeogeographic distribution of hybrid event beds that comprise both debris-flow (cohesive) and turbidity current (non-cohesive) deposits. This is the first study of such beds in a submarine fan system to combine outcrop and research borehole control, and uses a dataset from the Skoorsteenberg Formation of the Tanqua depocentre in the Karoo Basin, South Africa. Three types of 0.1-1.0 m thick hybrid beds are observed, which have a basal weakly graded finegrained sandstone turbidite division overlain by a division of variable composition that can comprise 1) poorly sorted carbonaceous-rich material supported by a mud-rich and micaceous sand-matrix; 2) poorly sorted mudstone clasts in a mud-rich sand-silt matrix; or 3) gravel-grade, rounded mudstone clasts in a well sorted (mud-poor) sandstone matrix. These upper divisions are interpreted respectively as: 1) the deposit of a debris-flow most likely derived from shelf-edge collapse; 2) the deposit of a debris flow, most likely developed through flow transformation from turbidity current that eroded a muddy substrate; and 3) from a turbidity current with mudstone clasts transported towards the rear of the flow. All three hybrid bed types are found concentrated at the fringes of lobes that were deposited during fan initiation and growth. The basinward stepping of successive lobes means that the hybrid beds are concentrated at the base of stratigraphic successions in medial and distal fan settings. Hybrid beds are absent in proximal fan positions, and rare and thin in landward-stepping lobes deposited during fan retreat. This distribution is interpreted to reflect the enhanced amounts of erosion and availability of mud along the transport route during early lowstands of sea level. Therefore, hybrid beds can be used to indicate a fan fringe setting, infer lobe stacking patterns, and have a sequence stratigraphic significance.

An exact analytical solution for the quantity of seepage from a trapezoidal channel underlain by a drainage layer at a shallow depth has been obtained using an inverse hodograph and a Schwarz-Christoffel transformation. The symmetry about the vertical axis has been utilized in obtaining the solution for half of the seepage domain only. The solution also includes relations for variation in seepage velocity along the channel perimeter and a set of parametric equations for the location of phreatic line. From this generalized case, particular solutions have also been deduced for rectangular and triangular channels with a drainage layer at finite depth and trapezoidal, rectangular, and triangular channels with a drainage layer and water table at infinite depth. Moreover, the analysis includes solutions for a slit, which is also a special case of polygon channels, for both cases of the drainage layer. These solutions are useful in quantifying seepage loss and/or artificial recharge of groundwater through polygon channels.

This paper presents the results of a comprehensive experimental study of the desiccation of fine-grained soils. Air drying of initially saturated soil slabs in controlled conditions is investigated by performing three kinds of tests: free desiccation tests, constrained desiccation tests (prevented shrinkage), and crack pattern tests. Strains, suction, water content, and crack geometry are investigated. Results reveal that unconstrained drying exhibits two stages: a domain with large, mostly irrecoverable deformations and degree of saturation close to 100%, followed by a domain with lower deformations at a decreasing degree of saturation. Homogeneous soil macroscopic cracking is possible only in the presence of boundary constraints and (or) moisture gradients, inducing the build-up of tensile stresses. Results also show that, for the initially saturated remoulded soils tested here, in the whole sample and near a crack initiation point, the degree of saturation remains very close to 100% until cracking, while cracking onset, the air-entry suction, and the shrinkage limit are close to each other. Cavitation nuclei and the formation of an irregular drying front at cracking initiation are commented upon in light of this observation. Finally, results suggest that the crack pattern geometry is the result of energy redistribution. A quantification of the process is proposed.

A carbon-rich black layer encrusted on a sandy pebbly bed of outwash in the northern Venezuelan Andes, previously considered the result of an alpine grass fire, is now recognized as a 'black mat' candidate correlative with Clovis Age sites in North America, falling within the range of 'black mat' dated sites (~12.9 ka cal BP). As such, the bed at site MUM7B, which dates to <11.8 ka 14 C years BP (raw dates) and appears to be contemporaneous with the Younger Dryas (YD) cooling event, marks a possibly much more extensive occurrence than previously identified. No fossils (megafauna) or tool assemblages were observed at this newly identified candidate site (3800 a.m.s.l.), as in the case of the North American sites. Here, evidence is presented for an extraterrestrial impact event at~12.9 ka. The impact-related Andean bed, located~20 cm above 13.7-13.3 ka cal BP alluvial and glaciolacustrine deposits, falls within the sediment characteristics and age range of 'black mat' dated sites (~12.9 ka cal BP) in North America. Site sediment characteristics include: carbon, glassy spherules, magnetic microspherules, carbon mat 'welded' onto coarse granular material, occasional presence of platinum group metals (Rh and Ru), planar deformation features (pdfs) in fine silt-size fragmental grains of quartz, as well as orthoclase, and monazite (with an abundance of Rare Earth Elements-REEs). If the candidate site is 'black mat', correlative with the 'black mat' sites of North America, such an extensive occurrence may support the hypothesized airburst/impact over the Laurentide Glacier, which led to a reversal of Allerød warming and the onset of YD cooling and readvance of glaciers. While this finding does not confirm such, it merits further investigation, which includes the reconnaissance for additional sites in South America. Furthermore, if confirmed, such an extensive occurrence may corroborate an impact origin.

Most researchers consider the black shale Bazhenov Formation as the main source of petroleum in the West Siberian fields. Detailed sedimentological, mineralogical and geochemical investigations reveal that there are three main types of Bazhenov Formation rocks: (i) clayey-siliceous; (ii) argillites; and (iii) anomalous clayey-silt-sandy rocks. The first type is characterized by more frequent benthic and planktonic fossils, extreme reducing conditions and lower rates of sedimentation in comparison with the argillites. The clayey-silt-sandy anomalous rocks are non-fossiliferous, were deposited in oxic conditions, and are characterized by the highest rates of sedimentation. We conclude that the clayey-siliceous rocks were deposited in moderately hemipelagic environments, the argillites were products of distal turbidities, and the anomalous clayey-silt-sandy rocks were deposited in channels.

Mineralogy and geochemistry of modern shallow sediments (up to 5 m thick) within the zone of water table fluctuations were studied to determine the likely sources and processes responsible for releasing As into groundwater. Samples were collected from different geological settings with varying groundwater As concentrations during dry (December 2005) and wet (September 2006) seasons at Sonargaon, Bangladesh. Stratigraphic sequences of the studied sediments showed three distinct lithofacies, viz. clayey-silt, silty-clay, and silty-very fine sand, corresponding to fine-grained overbank associations. Total As concentrations of shallow sediments ranged from <1 to 16 mg/kg without a significant difference in the range of As concentrations between the seasons. Sequential chemical extraction analysis of As revealed that >80% of the As was fixed in insoluble and organic phases, while the amount of As in reducible and acid-soluble phases was very low (<20%) and varied inversely with total As content. Total As concentration varied with mica content (muscovite and biotite) and its related elements (Al, Mg and Fe), but not with total organic C, suggesting that biotite is the major host phase of As. Arsenic appears to be liberated from biotite and/or other As-bearing minerals via chemical weathering (i.e., hydration-decomposition), either from the near-surface sediments which are subject to seasonal cycling of the redox conditions, or from within the aquifer sediments. Once released, progressive diagenesis to form As-bearing organic matter may be responsible for controlling As distribution in the sediments and coexisting groundwater of the study area.

Several new active fault traces were identified along Katrol Hill Fault (KHF). A new fault (named as Bhuj Fault, BF) that extends into the Bhuj Plain was also identified. These fault traces were identified based on satellite photo interpretation and field survey. Trenches were excavated to identify the paleoseismic events, pattern of faulting and the nature of deformation. New active fault traces were recognized about 1 km north of the topographic boundary between the Katrol Hill and the plain area. The fault exposure along the left bank of Khari River with 10 m wide shear zone in the Mesozoic rocks and showing displacement of the overlying Quaternary deposits is indicative of continued tectonic activity along the ancient fault. The E-W trending active fault traces along the KHF in the western part changes to NE-SW or ENE-WSW near Wandhay village.

The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4-7.4, dissolved oxygen (DO) of 0.8-1.8 mg/l, Ca contents of 5-50 mg/l, and Fe contents of 0.2-12.9 mg/l. Arsenic concentrations ranged from 8 to 251 lg/l, with an average value of 63 lg/l. A strong positive correlation exists between As and Fe (r 2 = 0.802; p = 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top, passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core sediments are oxidized (average oxidation reduction potential (ORP) ?170 and ?220 mV, respectively), and the ORP values gradually become negative from 3 to 13 m depths (-35 to -180 mV), indicating that anoxic conditions prevail in the shallow aquifers of the Brahmaputra plain. Age determinations suggest that clay horizons at *10 m depth were deposited at around 2,000 and 5,000 years BP ( 14 C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments, indicating As may be adsorbed onto Fe oxides in aquifer sediments.

Co-genetic debrite–turbidite beds are most commonly found in distal basin-plain settings and basin margins. This study documents the geometry, architectural association and paleogeographic occurrence of co-genetic debrite–turbidite beds in the Carboniferous Ross Sandstone with the goal of reducing uncertainty in the interpretation of subsurface data in similarly shaped basins where oil and gas is produced.The Ross Sandstone of western Ireland

During a pause in cone penetration in fine-grained soils, pore-water pressure dissipation tests are performed to evaluate the coefficient of consolidation. For standard piezocones with shoulder filter elements, soft clays and silts show a monotonically decreasing response with time; however, dissipation tests performed in heavily overconsolidated silts and clays show dilatory behavior, with the pore-pressure behavior increasing from the initial measured value to a maximum, and then decreasing to hydrostatic values. This paper presents a theoretical framework which combines cavity-expansion theory and critical-state soil mechanics with an analytical solution to the radial consolidation equation. The method is able to describe the pore-pressure response curve for dissipation tests performed in soils which demonstrate either monotonically decreasing or dilatory pore-pressure behavior.Key words: cavity expansion, consolidation, piezocone, pore pressure.

e Petites Dales cave is a favourable site for studying the sedimentary fi ll of the karst in the chalk of Normandy. e study of the fi ll is based on the lithological characterization and mineralogical and chemical comparison between the karstic sediments and the likely sedimentary sources (insoluble residue of chalk, clay-with-fl ints, loess). Results show that there are three main families of sediment in the Petites Dales karst: brown clayey silts, beige silts, pale beige silts. e karst sediments essentially originate from the mechanical erosion of loess. e insoluble residue of chalk, derived from the weathering of the chalk, is only found in the brown clayey silts, and constitutes a weak amount of this sediment type. According to these results, three conceptual models are proposed for the hydrosedimentary behaviour of the Petites Dales karstic system that could have resulted in such an intra-karstic deposition sequence. e integration of the sedimentary data into the morphological study of the galleries and their arrangement contributes to the conceptualization of an evolutionary pattern of the underground network in its paleogeographic context.

The lithologic composition and grain size distribution of sediments are primary determinants of their inherent reflectance properties. However, moisture content is also known to have a strong influence on reflectances of soils and sediments. If the effects of sediment composition, grain size and moisture content could be distinguished spectrally, it might be possible to map these properties at synoptic scales using hyperspectral, or perhaps even broadband, remote sensing. Mapping the spatiotemporal distribution of sediment composition and moisture content could provide unique constraints on both the processes by which the sediments are deposited as well as the constraints they may impose on subsequent water flow and sediment transport. The Ganges-Brahmaputra delta (GBD) is formed by the convergence of these two great rivers and is superlative in both size and geologic activity. Sediment redistribution and channel migration associated with the annual floods disrupt the lives of hundreds of thousands of people living on the GBD but is also critical for maintaining the delta area fertile and above sea level. The 30+ year archive of Landsat imagery could provide a basis for spatiotemporal analysis of these fluvial dynamics if sediment properties could be inferred or measured from reflectance spectra. However, before confronting the challenge of broadband detection we must understand the spectral properties of the sediments under more controlled laboratory conditions. Bidirectional reflectance spectroscopy of 109 sediment samples from the GBD yields a spectral mixing space that appears to be structured by variations in moisture content, grain size and possibly lithology. Although the individual Empirical Orthogonal Functions of the Principal Components do not correspond to unique absorption features, clustering within the mixing space is clearly influenced by moisture content and grain size. Laboratory spectra of sediment reflectance measured under varying moisture content yield distinct trajectories through the spectral mixing space for different grain size distributions of sieved sediments. These variations in moisture content account for N98% of spectral variance observed in these samples. Drying trajectories of coarse, fine and mixed sediments are distinct and suggest that moisture and grain size might be spectrally distinguishable. These results are consistent with Angstrom's hypothesis of moisture-driven spectral absorption but more controlled experiments are necessary to test the hypothesis rigorously.

1] The evaluation of the relationship between satellitederived vegetation indices (normalized difference vegetation index and normalized difference water index) and soil moisture improves our understanding of how these indices respond to soil moisture fluctuations. Soil moisture deficits are ultimately tied to drought stress on plants. The diverse terrain and climate of Oklahoma, the extensive soil moisture network of the Oklahoma Mesonet, and satellitederived indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) provided an opportunity to study correlations between soil moisture and vegetation indices over the 2002 -2006 growing seasons. Results showed that the correlation between both indices and the fractional water index (FWI) was highly dependent on land cover heterogeneity and soil type. Sites surrounded by relatively homogeneous vegetation cover with silt loam soils had the highest correlation between the FWI and both vegetation-related indices (r$0.73), while sites with heterogeneous vegetation cover and loam soils had the lowest correlation (r$0.22). Citation:

AB ST R ACT : The spatial distribution of the Atterberg limits can be used to distinguish the consistency and behaviour of a soil and its engineering properties, which strongly depends on the water content of the soil and types of silts and clays in the soil. By spatial modeling, and comparing the results of ordinary kriging with the cokriging approach, this study aims to find correlations between the Atterberg limits and the selected physical soil parameters in order to examine how effective they are in generating an understanding of the dynamics of a physical soil system.

Bankfull channel width is a fundamental measure of stream size and a key parameter of interest for many applications in hydrology, fluvial geomorphology, and stream ecology. We developed downstream hydraulic geometry relationships for bankfull channel width w as a function of drainage area A, w = α A β , (DHG wA ) for nine aggregate ecoregions comprising the conterminous United States using 1588 sites from the U.S. Environmental Protection Agency's National Wadeable Streams Assessment (WSA), including 1152 sites from a randomized probability survey sample. Sampled stream reaches ranged from 1 to 75 m in bankfull width and 1 to 10,000 km 2 in drainage area. The DHG wA exponent β, which expresses the rate at which bankfull stream width scales with drainage area, fell into three distinct clusters ranging from 0.22 to 0.38. Width increases more rapidly with basin area in the humid Eastern Highlands (encompassing the Northern and Southern Appalachians and the Ozark Mountains) and the Upper Midwest (Great Lakes region) than for the West (both mountainous and xeric areas), the southeastern Coastal Plain, and the Northern Plains (the Dakotas and Montana). Stream width increases least rapidly with basin area in the Temperate Plains (cornbelt) and Southern Plains (Great Prairies) in the heartland. The coefficient of determination (r 2 ) was least in the noncoastal plains (0.36-0.41) and greatest in the Appalachians and Upper Midwest (0.68-0.77). DHG wA equations differed between streams with dominantly fine bed material (silt/sand) and those with dominantly coarse bed material (gravel/cobble/boulder) in six of the nine analysis regions. Where DHG wA equations varied by sediment size, fine-bedded streams were consistently narrower than coarse-bedded streams. Within the Western Mountains ecoregion, where there were sufficient sites to develop DHG wA relationships at a finer spatial scale, α and β ranged from 1.23 to 3.79 and 0.23 to 0.40, respectively, with r 2 N 0.50 for 10 of 13 subregions (range: 0.36 to 0.92). Enhanced DHG equations incorporating additional data for three landscape variables that can be derived from GIS-mean annual precipitation, elevation, and mean reach slope-significantly improved equation fit and predictive value in several regions, most notably the Western Mountains and the Temperate Plains. Channel width was also related to human disturbance. We examined the influence of human disturbance on channel width using several indices of local and basinwide disturbance. Contrary to our expectations, the data suggest that the dominant response of channel width to human disturbance in the United States is a reduction in bankfull width in streams with greater disturbance, particularly in the Western Mountains (where population density, road density, agricultural land use, and local riparian disturbance were all negatively related to channel width) and in the Appalachians and New England (where urban and agricultural land cover and riparian disturbance were all negatively associated with channel width).

Durant cette période, j'ai bénéficié, à l'Ecole Nationale d'Ingénieurs de Tunis, du soutien attentif et des conseils précieux du Professeur Mounir Bouassida et de Monsieur Mehrez Jamei. A l'Université Joseph Fourier, une aide considérable, m'a été apportée par le Professeur Pascal Villard. Egalement, de la confiance et de la bienveillance que le Professeur Jean-Pierre Gourc a témoignées à mon égard le long de ce travail. Tous ces facteurs importants ont aidé à l'aboutissement de ce travail. Je tiens, donc, à leur exprimer tous mes remerciements. Sur le plan de l'étude expérimentale réalisée à l'ENIT, je suis très reconnaissant à Madame Houda Guiras pour son soutien considérable. Je remercie également dans le même cadre Monsieur Olivier Plé et tous les techniciens de la section géotechnique de SCETAUROUTE de Grenoble. Je remercie également les membres de jury de la thèse d'avoir accepter de rapporter et d'examiner ce travail de recherche. Il serait difficile de citer ici toutes les personnes qui ont contribué à l'aboutissement de ce travail. J'adresse tout de même une pensée particulière à Monsieur Mabrouk Hatira et à Madame Samia Boussetta pour leurs instincts parentaux surdéveloppés. Je remercie par la même occasion tous mes collègues de l'ISTEUB, de l'ENIT, de l'URIG et de l'ex-LIRIGM qui ont contribué de près ou de loin à la réalisation de ce travail.

Measurements of the refractive index ( A n ) and loss tangent (tan 6 ) of dust particles in a laboratory simulated model of dust storms have been carried out at 11 GHz utilizing a confocal microwave open-cavity resonator. Four samples were used; namely sandy, silty, clayey silt, and clayey for concentrations varying from to 4 x g/cm3. The particle-size distribution (PSD) of each sample was measured by seiving along with the hydrometer technique.

Field studies of fine-sediment transport were carried out in the Mekong River estuary, Vietnam, in the high-flow season of November 1993. In the freshwater region, erosion and deposition of suspended sediment occurred at tidal frequency with a strong down-river transport at a mean velocity of 1ms−1and mean suspended-solid concentration of about 250mgl−1. Also, the suspended sediment was mostly fine silt,

This paper deals with the application of two different processing methods of the georadar data aimed at improving the results in the case of bad quality data. The georadar data are referred to two areas located in the Axum archaeological park (Ethiopia) and were acquired prior to the reinstallation of the returned Stele from Italy to the Ethiopian Government. In the area the schist formation is covered by an outcropping sandy silt formation about 6-8 m thick. The archaeological excavations, performed before the georadar data acquisition, revealed that tombs and catacombs were dug into the superficial layer. Because the complexity of the georadar data interpretation based on standard data processing, some of the collected measured data are also processed by an innovative microwave tomographic approach which permits to achieve clearer diagnostic results with respect to the classic radaristic techniques in 2D and 3D representation. We take into account the data acquired for the East stele 2 with 100 MHz antenna and in the parking area of the archaeological park with 200 MHz antenna. The data were acquired on profiles 1 m apart. Comparing the data processed with the two different approaches, we obtained an improvement of the vertical resolution and of the quality of image on time slices using the tomographic approach compared to the results obtained with the classic radar one.

Construction of a 16-m deep, 55-m wide, almost square, underground structure through 8-m of soft soils and 8-m of sandstone and siltstone led to the development of widespread settlements. The affected area extended to distances of over 200 m from the perimeter of the structure. The floor slab of the underground structure was not designed for water pressure. Thus, operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure. Subsurface investigation and monitoring data obtained over 5.75-year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure. An analytical study was undertaken to project the long term settlement. A simple analytical model could be used to simulate the complex hydrogeological problem reasonably. The details of hydrogeologic setting, subsurface investigation and monitoring activities, and the analytical model for projecting long-term settlements are presented in this paper.

à la périphérie nord-ouest des Vosges, de nombreux dépôts anciens ont été décrits sous des appellations variées, avec des âges attribués allant du Mindel au Pliocène. L'inventaire systématique de ces données, complété par des levés de terrain, a permis de différencier plusieurs faciès et formes de relief dont le sommet est à une altitude relative supérieure à 60 m par rapport aux basses terrasses actuelles. Les dépôts comprennent des alluvions grossières à galets, des graviers peu classés, des sables et parfois des lentilles de silt sableux blanc. Les structures sédimentaires, relativement perturbées par le tassement dû à la dissolution ou à l'altération d'une partie du matériel initial, sont à stratification en faisceaux arqués, avec des structures d'affaissement, de cryoturbation et parfois de chenalisation. Le matériel grossier est composé en majorité de quartz et quartzite provenant du Conglomérat principal du Buntsandstein, avec des galets très altérés de grès et exceptionnellement de granite. Le matériel est globalement très lessivé. Une couverture silteuse, de un à plusieurs mètres d'épaisseur, coiffe ces unités. Ces formations anciennes sont associées à plusieurs types de formes construites : un épandage fluvioglaciaire en terrasse (Épinal, Moselle) prolongé en aval par des lambeaux de terrasse (Charmes), des lambeaux de cônes latéraux et de terrasses (vallée de la Meurthe) et des épandages de piémont en inversion de relief (Tanconville-Cirey-sur-Vezouze, Arentèle et Mortagne). L'origine fluvioglaciaire de ces derniers reste à démontrer en raison de la quasi absence, originelle ou due à l'altération, de matériel provenant du socle cristallin des Vosges. Un âge minimal Mindel/Elstérien (fin du stade OIS 12) est attribué à la terrasse fluvioglaciaire d'Épinal d'altitude relative de +60 m. Les épandages de piémont à 80 m d'altitude relative, blanchis dans les lithozones inférieures, sont très probablement plus anciens, ils pourraient dater du stade glaciaire OIS 16 du Cromérien.

The suspended sediment of the Fly River is mostly fine silt with a mean particle size of 8 /olm; the clay fraction makes up less than 20% of the suspended sediment by volume. On reaching brackish water in the estuary, the sediment flocculates. The floes are small (typical mean size of 30 /olm) and are a mixture of fine silt and clay particles, with silt particles dominating. Because of the dominance of silt particles incorporated in the floes, the floes are structurally weak and are destroyed by tidal turbulence at spring tides. The clay particles are selectively trapped in the turbidity maximum zone of the estuary.

A palygorskite unit was discovered in a road cut of undifferentiated Tertiary limestone between the villages of El Pariso and San Roman (18°49.309N, 88°37.861W) in the southeastern Yucatán Peninsula, Mexico. This is the southern most locality of a clay-rich sedimentary unit reported in the literature for the Tertiary carbonates of the Yucatán Peninsula. This occurrence indicates a much wider range of palygorskite-rich clay deposition than previously recognized. The lithology is 99% clay and 1% sand to silt size diagenetic quartz grains. The clay consists of approximately 85% palygorskite, 15% montmorillonite and trace amounts of titanium oxides. EDS analyses on palygorskite are largely consistent with sedimentary palygorskites from other coastal marine settings, however palygorskite has a low total Fe content (average = 0.40 wt% expressed as Fe 2 O 3 ) compared to many other sedimentary palygorskites. Montmorillonite chemical compositions are typical and compared to the palygorskite have substantially higher Fe 2 O 3 concentrations (average = 3.90 wt%). The low percentage of coarse grains in the lithology combined with a high proportion of palygorskite and lack of detrimental trace minerals suggest the deposit is of industrial grade; however, it has limited reserves (6,000 m 3 ). The unit could be potentially used in a wide array of environmental applications which are needed in the region including liners for landfills and constructed wetlands. The unit is in a geographic location which would serve the expanding economy of the region. This resource has the potential to have great impact on the quality of the local environment and the economy of a region under great environmental threat.