Alluvial Material Research Articles

Characterization and Classification of Soils of Valsad taluka, Valsad District, Gujarat

Five representative pedons (P1 Umarsadi; P2 Segvi; P3 Chikla; P4 Bagal; and P5 Faldhara) from different landforms of Valsad taluka in the coastal region of Valsad district, Gujarat were studied for their morphological, physical, and chemical properties. The soils were deep to very deep, well to imperfectly drained, slightly alkaline to strongly alkaline (pH 7.8 to 9.7), non-saline tosaline (0.1 to 4.4 dS m-1), low to high in organic carbon (2.4 to 12.3 g kg-1) and CaCO3 (0.2 to 19.5%), and medium to high in CEC [21.8 to 69.9 (p+) kg-1]. Soil texture varied from sandy clay loam to clay with clay content ranging from 21.2 to 53.5 %. Bulk density was lower in P5 (1.28-1.33 Mg m-3) than the other pedons (1.21-1.48 Mg m-3). Saturated hydraulic conductivity (sHC) was less than the critical limit of 1.0 cm hr-1 in P3, and generally low due to high (>15) exchangeable sodium percentage (ESP) and exchangeable magnesium percentage (EMP). Pedon P1 was classified as Sodic Haplusterts and P4 as Typic Haplusterts. The pedon P2 with an argillic horizon(<35 cm thickness) in the deeper layerswas classified as Inceptic Haplustalfs. The pedon P3 with lithological discontinuity was classified as Typic Ustifluvents and P5 as Vertic Haplustalfs. The pedons P1, P3 and P4 were developed in the basaltic alluvial parent material, and their subsurface properties were influenced by the paleosols. The pedons P1, P2, and P5 under perennial crops such as mango and eucalyptus have higher organic carbon and lower bulk density. Management measures are required to reduce subsoil sodicity, and sustain crop production in the heavy textured soils.

Geochemical signature of earthquake-induced surface flooding by mineralized groundwater over the buried Atlántida deposit, northern Chile

At the buried Atlántida deposit (Cu–Au–(Mo)) in the Atacama Desert of Chile, highly saline pockets of fine-grained material 10 cm–3 m in diameter were identified on the alluvial surface using remote sensing and detailed regolith mapping. The median salinity (NaCl dominant) of the saline pockets is 2.2% compared to background alluvial material with a median salinity of 0.01%. Their distribution along mapped fault structures and the highly saline nature of the material suggest they form as an expression of groundwater forced through fractures to the surface during seismic activity. A targeted geochemical survey, oriented parallel to the orientation of the structures (sample spacing 250 m along structural trend) specifically sampling saline pockets on relatively old surfaces, was performed over the deposit. Deionized water extraction of soluble salts and analysis by inductively coupled plasma mass spectrometry revealed strong correlations of increasing salinity and increasing concentrations of porphyry copper pathfinder elements. Elevated responses of Se, Mo, Re and Te normalized to a groundwater volume proxy are present directly over the Atlántida deposit. This suggests the rate of erosion and sedimentation is slow enough in the Atacama Desert to preserve surficial anomalies as saline pockets, formed by periodic seismically induced surface flooding of groundwater along faults extending to surface. Targeted sampling of saline pockets along structural trends using weak leach geochemistry in terrains dominated by transported cover can serve as a routine exploration method for the potential discovery of buried copper porphyries and other styles of mineralization in the Atacama Desert of Chile.

Identification of gypsum karstification using an electrical resistivity tomography technique: The case-study of the Sivas gypsum karst area (Turkey)

The Sivas district is the most important gypsum karstified area in Turkey. The oldest evaporites in the region were formed during the sedimentation process of the Oligocene period. Generally, these units extend along the southern part of the Sivas basin. After the Early Miocene Sea drained from this region, extensive evaporite deposition developed. An electrical resistivity tomography (ERT) study was carried out between the Hafik and İmranlı districts of the Sivas gypsum karstified area. In this research, the prior aim was to determine the general characterization, geometry, sedimentary cover and resistivity properties of gypsums. In addition, the study includes the synthetic modelling of different gypsum karstification types. The evaluation and interpretation were based on ERT data that was collected from the Hafik-İmranlı region. First, the different karstifications were identified, together with the characteristic features of gypsum in the area. The ERT studies showed that there are large and old karst structures between the Hafik and Zara district. However, the karst structures that are located between the Zara and İmranlı regions were interpreted as smaller and younger. The characteristics of both of the regions are different in terms of the morphometric properties. It is certain that the Kızılırmak River has an important impact on the formation of these structures. ERT studies have shown that the cover- and bedrock-type collapse sinkholes are very spread out across the area, and their geometries are different. Throughout time, the suffosion type of cavities formed inside the cover-type sinkholes as a consequence of geological and geomorphological events. The ERT sections showed that certain parts of these structures collapsed, and then alluvial materials filled in. The shallow groundwater level in the drilling results and the conductive zone in the ERT results are compatible with each other. ERT studies clearly determined the various karstification typologies of gypsums in the region, which also contributed to the creation of a detailed conceptual geological model.

Integrating radon and thoron flux data with gamma radiation mapping in radon-prone areas. The case of volcanic outcrops in a highly-urbanized city (Roma, Italy)

An integration of laboratory radon and thoron exhalation data with gamma radiation mapping is applied to assess the geogenic radon and the exposure of people to natural radiation in a highly-urbanized city (Roma, Italy). The study area is a protected territory where ignimbrites from Colli Albani volcano and alluvial sediments largely crop out. A map of total gamma radiation, a gamma transect across Caffarella valley and 9 vertical gamma profiles have been carried out, showing that the main control of gamma levels is, of course, the lithological nature, without neglecting the simultaneous effect of other parameters such as slope morphology, erosion/weathering processes, occurrence of sinkholes or underground tunnels. The surveys allowed to distinguish the medians of ignimbrites (from 816 ± 16 cps to 936 ± 19 cps) from that of alluvial materials (611 ± 14) cps), but showed also that alluvial sediments with anomalously high radioactivity (769 ± 14 cps) can be locally recognized, providing valuable information on the interaction between sedimentation and erosion in fluvial valleys. Total gamma activity was converted into absorbed gamma dose rate ranging from 0.33 to 0.38 μSv/hr. Outdoor Annual Effective Dose Equivalents were also estimated between 0.58 and 0.67 mSv y−1.Laboratory radon and thoron exhalation rates of collected material are positively correlated with gamma radiation. Volcanic and alluvial sediments are well-discriminated. The correlation between the two variables is evident, but not robust because of the variable concentration of 40 K, which is not contributing to radon and thoron exhalation rates. Anomalous data of soil samples located at the foot of a slope can be interpreted as due to reworking and accumulation processes. Similar gamma radiation data documents analogous concentration of radon and thoron parent-nuclides, but coexisting different radon and thoron exhalation rates provides an additional information on different grain size distributions which can be considered as a proxy for soil gas permeability.The integration of gamma mapping and radon and thoron exhalation measurements is a very useful tool to assess people exposure to natural radiation, in terms of dose rates and potential indoor radon. Gamma mapping, which provides data on the radiation source (the bedrock) is fast and not expensive. It allows to obtain very detailed pictures of a study area, but it needs to be combined with laboratory determination of radon and thoron release in order to definitely and correctly interpret variations of gamma signal. Furthermore, laboratory determination of soil radon exhalation gives information on the release of radon and is a good proxy for soil gas permeability. It has the great advantage over in-situ measurements of gas flow not to be influenced by seasonal pedoclimatic parameters and is affected by lower analytical uncertainties. These data are thus reproducible and precise and can be used to estimate potential radon hazard, which is the main source of exposure and thus the most important parameter for human protection from environmental radioactivity.

The contribution of geophysics to archaeology: a case study of an ancient canal of the Oc Eo culture in the Mekong Delta, Vietnam

Generally, underground ancient canals are infilled with alluvial materials, with the canal bed and substrate often having different resistivity values. This study aimed to determine the location and morphology of Malleret’s ancient canal 16 located to the southeast of the Ba The mountain, Mekong Delta, Vietnam by means of geophysical techniques. Two geophysical methods were used: electromagnetic profile and electric resisitivity tomography. A geoelectric structure 70 m long with 70–95 mS/m of apparent conductivity was found. On the electrical resistivity tomography section, a resistivity zone of 10–20 Ω∙m, 1–4 m deep, 70 m wide corresponds to the mentioned above geoelectric structure, which is in an asymmetric U-shape extending toward the southeast-ern bank of canal 16. Hand-augering confirmed that the canal bed is fully incised into Holocene sediments as a substrate which stretches down to the Pleistocene. The sediments are composed of loams mixed with plant re-mains with a resistivity ρ ~ 10–15 Ω∙m. Both of the canal banks at a depth of 5 m are made up of Holocene sedi-ments (ρ ~ 4–10 Ω∙m). The 14C measurements determined the age of the organic matter in the canal as being equal to 1210 ±85 BP, suggesting canal 16 ceased being operational at that time. The precise positioning of canal 16 on the ground surface, as well as identifying the morphology of the canal bed, were corroborated by geophysical techniques. The obtained results are of considerable value to archaeologists.

Hydrochemistry of groundwaters from alluvial and fractured igneous aquifers at the western region of Lake Hazar (Elazığ, Turkey)

The study area is located at Eastern Anatolian Fault Zone and at the western shore of Lake Hazar (Elazig, Turkey). This study aims to identify the hydrochemical features of groundwaters from fractured igneous aquifers and to correlate them with the alluvial aquifer’s groundwaters. The water samples were collected in April and September during the rainy and dry periods, respectively. As a result of active tectonism in this region, hard rocks have gained secondary porosity and permeability. According to major ion composition, the fractured igneous and alluvial aquifer groundwaters can be grouped into the Ca-Mg-HCO3 type, whereas the groundwaters emerging very close to the thrust fault locations can be classified as the Mg-Ca-HCO3 type. The water-rock interaction process represents the primary factor controlling the hydrochemistry of the investigated groundwaters. Generally, the alluvial aquifer’s groundwaters are characterized by low pH values. Clay minerals in the alluvial material may act as H+ buffers and cause decreased pH values. According to the isotopic tracers of 18O, 2H, and 3H, the spring water discharging at higher altitudes from the fractured igneous aquifer reflects rapid circulation and recharging from recent precipitation compared to alluvial aquifer groundwater. The groundwaters’ major ions fall well within the permissible limits for drinking water in Turkey. In contrast, the NO3− and NH4+ concentrations from groundwaters, especially those recharging from fractured igneous aquifers, are very close to or in excess of the limit values. The high concentrations of NO3− and NH4+ in groundwaters presumably result from landfills and the use of agricultural fertilizers in the study area. The surface waters (Lake Hazar and man-made wetland (MMW)) also are investigated within the scope of the hydrochemistry studies. Higher TDS, Cl−, and Na+ concentrations in the MMW reflect salinity that could result from lake water intrusion and evaporation processes.

Shallow Subsurface Stratigraphy Inferred from the Use of Vertical Electrical Soundings (VES) Survey in Central Chihuahua, Mexico

Vertical Electrical Soundings (VES) provide fast and economical measurements used in geophysical exploration. VES were carried out in El Sauz-Encinillas (ESE) aquifer, in northern Mexico, to determine apparent resistivity and geoelectrical units’ thickness. Despite it being one of the three main aquifers feeding Chihuahua city, a lack of available geophysical data prevails in its northern portion. The main goal of this study was the determination of the geoelectrical units in the subsurface stratigraphy via electrical-resistivity soundings. The ESE’ aquifer is located within alluvial Quaternary sediments, with varying granulometry and reaching from a few meters to more than 600 meters of thickness at the center of the valley. Forty-five vertical electrical resistivity soundings (Schlumberger array, maximum AB/2 distance of 500 m) were performed throughout ESE aquifer’s northern portion. Field data were analyzed using software. Results illustrate a wide variability in resistivity values throughout the study area. Five geoelectrical units were identified: 1) a hardpan topsoil, with resistivity values ranging from 200 - 800 Ω-m ; 2) an alluvial material mixture (sand/silt) with resistivity values ranging from 25 to 100 Ω-m; 3) playa lake-type material (clay/evaporites mixture) with resistivity values ranging from 0.2 to 15 Ω-m; 4) a gravel/sand mixture with resistivity values from 100 to 300 Ω-m; and 5) a partly fractured rock or conglomeratic material with resistivity values ranging from 400 to 3500 Ω-m. The electrical resistivity data, therefore gives reasonably accurate results that can be used to understand the subsurface stratigraphy and basement configuration in groundwater exploration.

Seismic Response of Irregular Triangular Alluvial Valleys under Shear Waves Using Spectral Elements

The present study investigates seismic response problems of triangular uniform irregular alluvial valleys under shear waves using a finite element spectral method. Alluvial valleys; affect the shape and properties of alluvial materials on the response and seismic behavior of the valley surface due to the geometry conditions. Therefore this study aims to illustrate the plots and magnitude of amplification values for irregular alluvial valleys in a two-dimensional triangular manner, with the characteristics of homogeneous alluvial materials and different geometric characteristics. The analysis in the time domain was performed based on the finite element method of the spectral element (SFEM) using NASEM software, developed by Najafizadeh. The valleys are analyzed with the slope angles of 15, 30, 45 and 60 degrees on one side and in opposite directions with a slope of 45 degrees and with a maximum depth of 50 meters for the alluvial valley. The horizontal amplification curves in the alluvial valley's points from the analysis reach a maximum value at a given frequency, which can be an ideology for determining the frequency of irregular triangular alluvial valleys under different slope valley angles. The results of natural valley frequencies indicate that with decreasing slope of the valley, the natural frequency of the valley decreases, as well as amplification plots are related to the slope of the valley.

Morphological Dynamics of the Jamuna River in Kazipur Subdistrict

This study identifies and evaluates the morphologically changing trend and process–response mechanisms of Jamuna River. The study considers the bank erosion, bank-line shifting, rate of erosion, accretion, sedimentation, course changing directions, changes in river width, fluvial landform dynamics, and floodplain features. The lower Brahmaputra–Jamuna River (named Jamuna River) at Kazipur subdistrict, Sirajganj district in Bangladesh are the study area. Multispectral Landsat satellite imageries of dry seasons were used for time series analyses of time periods (1972–2016) to interpret the chronological changes of morphology. The outcomes obtained from the analyse, support the historical westward channel shifting of the river, alluvial material properties, explicate fluvial processes, discharge anabranch instability, erosion, and morphological responses.

Characteristics, classification and genesis of vertisols under seasonally contrasted climate in the Lake Chad Basin, Central Africa

General properties of Vertisols are known world-wide, but these properties vary in different areas due to specific environmental conditions. The mastery of the specific characteristics of each Vertisols in a given area requires detailed site-scale investigation. This work aims to study the properties of the Lake Chad Basin Vertisols, attempt to highlight their genetic processes and classification. These Vertisols are dark, clayey and massive, very compact, with deep wide-opened cracks and gilgaï micro-relief. They show neutral to slightly alkaline pH, low organic matter content (0.7–2.73%) and high C/N ratio values (7.34–39.64). Ca2+ and Mg2+ are the most represented exchangeable cations (5.92–30.72% and 1.28–5.44%, respectively) on the absorption complex. Smectite is the main clay mineral species, but small contents of kaolinite, illite, quartz and feldspars are also present. The most concentrated elements in the profile are silica (61.07–77.78 wt.% SiO2), aluminium (7.08–15.54 wt.% Al2O3) and iron (1.78–6.92 wt.% Fe2O3). The Si/Al ratio (>2) and chemical index of alteration (CIA) are moderate to high (56.76–88.39) and indicate a moderate to intense weathering. Such properties reflect the pedogenic influence of the environmental factors like contrasting climate, low topographic position and the alluvial parent material. The accumulation of basic cations favours the neosynthesis of smectite minerals typical of a dominant bisiallitisation process. The Vertisols profiles, due to the presence of a perched water table, enable to classify these soils as Epiaquerts and Endoaquerts Vertisols (USDA soil taxonomy) and Gleyics and Fulvics Vertisols (WRB). Their physical characteristics and notably their difficult water management constitute a limitation to agricultural activities.

Clay dispersion: An important factor in channel runoff generation in a semi-arid, loess-covered area with very low rain intensities

Overland flow is usually regarded as an important contributor to storm channel flow. This observation is certainly applicable to dryland areas, where base flow is often irrelevant, particularly in small watersheds. This study examines channel runoff generation in the extensive loess-covered areas that characterize the mildly arid area of western Israel, where the average annual rainfall is 280 mm. Hydrological data point to a peculiar hydrological behavior of the ephemeral streams that experience a high frequency of sporadic channel flow events. Even in extreme rain events, peak discharges are exceptionally low, indicative of a limited contributing area. Hydrographs are characterized by very steep rising and falling limbs, usually representative of saturated areas, located in the vicinity of the runoff recording station. Based on this observation, we advanced the hypothesis that storm runoff originated in the limited area of the active channel, with negligible runoff from the adjoining hillslopes. We argue that a quasi-permanent surface seal, at the top of the alluvial deposit, drastically limits the hydraulic conductivity of the alluvial fill, allowing runoff generation at very low rain intensities. The occurrence of the surface seal is ascribed to the combination of two main factors. A high clay content (~40%), where the dominant clays are smectite and illite, characterized by a laminar structure and a high-water absorption capacity. The swelling of the clay particles considerably reduce the porosity of the alluvial material, allowing runoff generation at very low rain intensities while limiting the depth of water penetration in the channel itself. Data presented fit the concept of “Partial Area Contribution” identified in humid areas. However, the application of this concept to dryland areas is based on completely different reasons.

ENGINEERING GEOLOGICAL MAPPING ON SLOPE DESIGN IN THE MOUNTAINOUS AREA OF SABAH WESTERN, MALAYSIA

The geology in the mountainous area of Sabah western provides a favourable setting for engineering geological instability. The area is underlain by the Trusmadi Formation (Palaeocene to Eocene age), the Crocker Formation (Late Eocene to Early Miocene age) and vary recent Quaternary alluvial materials which are still being deposited. The argillaceous nature and intense deformation suffered by the Trusmadi Formation and the highly jointed sandstone and mudstone beds of the arenaceous Crocker Formation makes them highly susceptible to weathering and instability. The weathered materials are unstable and may experience sliding due to by high pore pressure and intensively of geomorphological processes. In this study, a total of 20 selected critical slope failures were studied and classified into two main groups; rock slope (ten) and soil slope (ten). Soil slope failures normally involved large volumes of failed material as compared much rock slopes, where the failures are mostly small to medium. Kinematics rock slope analyses indicates that the variable potential of circular, planar, wedges, and toppling failures modes as well as the combination of more than one mode of aforementioned failure. Rock and soil slopes stability analysis indicates that the factor of safety value as unsafe (0.56 to 0.95). The geological influence had transformed the slopes in the Sabah mountainous area to be highly unstable and susceptible to landslide occurrences. Six (6) related main parameters to the landslide occurrence in the study area were attributed; 1) local and regional geology, 2) hydrological and geohydrological, 3) mineralogical and micro structures, 4) local discontinuities structures, 5) physical and engineering properties of soil and rock, and 6) geomorphological processes which can help in evaluating landslide problems. Therefore, development planning has to consider the slope hazard and risk management. This engineering geological mapping may play a vital role in disaster risk reduction programme in Sabah to ensure the public safety and to be extend with different environment.

ENGINEERING GEOLOGICAL STUDY ON THE SLOPE FAILURE ALONG THE KIMANIS TO KENINGAU HIGHWAY, SABAH, MALAYSIA

The geology along the Kimanis to Keningau Highway provides a favourable setting for engineering geological instability. The area is underlain by the Crocker Formation (Late Eocene to Early Miocene age) to vary recent Quaternary alluvial materials which are still being deposited. Crocker Formation consists mostly of interbedded grey sandstones and grey mudstones or shales. The sandstones are texturally immature where angular to subrounded quarts grains are cemented by clay minerals and occasionally by calcite. The Crocker Formation has also undergone intense deformation. The tectonic complexities influenced the physical and mechanical properties of the rocks, resulting in a high degree of weathering and instability. The weathered materials are unstable and may experience sliding due to by high pore pressure and intensively geomorphological processes. In this study, a total of 28 selected critical slope failures were studied and classified into two main groups: rock slope and soil slope. Failures in soil slopes (including embankments) are 18 (64 %) whereas 10 of all failures (36 %) of rock slope. Soil slope failures normally involved large volumes of failed material as compared much rock slopes, where the failures are mostly small. Of the 18 failures in soil slopes, 6 (33 %) are embankment failures making them 21 % of all types of failures. Kinematics rock slope analyses indicates that the variable potential of circular, planar, wedges and toppling failures modes as well as the combination of more than one mode of aforementioned failure. Rock and soil slopes stability analysis indicates that the factor of safety value as unsafe (0.50 to 0.96). The main factors causing slope failure occurrences in the study area are natural (geology, meteorology, topography and drainage system) and human factors (lack of proper planning, human activities and community’s attitude). Development planning has to consider the hazard and environmental management program. This engineering geological study should be prioritized and take into consideration in the initial step in all infrastructures program and it may play a vital role in landslide hazard and risk assessment to ensure the public safety.

Seismic velocity structure of the Jakarta Basin, Indonesia, using trans-dimensional Bayesian inversion of horizontal-to-vertical spectral ratios

Characterizing the interior structure of the Jakarta Basin, Indonesia, is important for the improvement of seismic hazard assessment there. A dense-portable seismic broad-band network, comprising 96 stations, has been operated between October 2013 and February 2014 covering the city of Jakarta. The seismic network sampled broad-band seismic noise mostly originating from ocean waves and anthropogenic activity. We used horizontal-to-vertical spectral ratio (HVSR) measurements of the ambient seismic noise to estimate fundamental-mode Rayleigh wave ellipticity curves, which were used to infer the seismic velocity structure of the Jakarta Basin. By mapping and modelling the spatial variation of low-frequency (0.124–0.249 Hz) HVSR peaks, this study reveals variations in the depth to the Miocene basement. These variations include a sudden change of basement depth from 500 to 1000 m along N–S profile through the centre of the city, with an otherwise gentle increase in basin depth from south to north. Higher frequency (2–4 Hz) HVSR peaks appear to reflect complicated structure in the top 100 m of the soil profile, possibly related to the sediment compaction and transitions among different sedimentary sequences. In order to map these velocity profiles of unknown complexity, we employ a trans-dimensional Bayesian framework for the inversion of HVSR curves for 1-D profiles of velocity and density beneath each station. Results show that very low-velocity sediments (<240 m s−1) up to 100 m in depth cover the city in the northern to central part, where alluvial fan material is deposited. These low seismic velocities and the very thick sediments in the Jakarta Basin will potentially contribute to seismic amplification and basin resonance, especially during giant megathrust earthquakes or large earthquakes with epicentres close to Jakarta. Results have shown good correlation with previous ambient seismic noise tomography and microtremor studies. We use the 1-D profiles to create a pseudo-3-D model of the basin structure which can be used for earthquake hazard analyses of Jakarta, a megacity in which highly variable construction practices may give rise to high vulnerability. The methodology discussed can be applied to any other populated city situated in a thick sedimentary basin.

GEOCHRONOLOGY AND HYDRODYNAMIC ENERGY CONDITIONS IN SURFACE COVERINGS OF LOW HOLOCENE FLUVIAL, FLUVIAL-MARINE, AND MARINE TERRACES: CLIMATIC PULSATIONS TO THE SOUTH OF THE ARANGUAGUÁ RIVER BASIN (SC)

This research aims to perform the geochronology of surface coverings in low Holocene marine, fluvial-marine, and fluvial terraces, associating the genesis of paleo-forms with the occurrence of Holocene climatic pulsations, the consequential switches between hot-dry/hot-wet continental phases, and the retrograde and prograde movements of the oceanic coast due to eustatic sea-level fluctuations. At the same time, it aims to verify and correlate specific hydrodynamic energy conditions during past depositional events, responsible for preparing the levels of low fluvial, fluvial-marine, and marine terraces to the south of the Araranguá river (SC). The methodology was based in absolute dating through Optically Stimulated Luminescence (OSL) in quartz grains of the surface coverings of these low terraces and in granulometric tests with later data plotting and verification of sediment types, textural classes, and the respective paleo-hydrodynamic energy conditions, classified based on the textural diagram of Flemming (2000). Results of geochronological reconstruction corresponded to climatic events of switches between hot-dry/hot-wet environments and to global cooling periods identified by Bond et al. (1997, 2001) and Wanner et al. (2011). Three Holocene climatic pulsations were identified, which were determinant for the superficial organization of the landscape in the lower course of the Araranguá river and the oceanic plain of the Araranguá River Basin: Climatic pulsation I (6.000 ± 820 to 5.000 ± 620 Years B.P.), climatic pulsation II (2.700 ± 420 to 2.250 ± 300 Years B.P.) and climatic pulsation III (420 ± 65 to 215 ± 25 Years B.P.). The application of results in the textural diagram of Flemming (2000) allowed the differentiation of sedimentation environments, which were correlated with varied hydrodynamic energy regimes. Surface coverings of the low fluvial terrace (GS-I) and the alluvial materials of the low fluvial-marine terrace (GS-II) presented the highest mud content among all samples, which was correlated with moderate and moderate-to-high hydrodynamic energy transport flows. On the other hand, surface coverings of marine terraces (GS-III and GS-IV) and the marine sandy materials underlying alluvial deposits of the fluvial-marine terrace showed low levels of mud and high levels of sand, representing high- and very high-intensity hydrodynamic energy flows.

Understanding the spatial distribution and physical attributes of upland swamps in the Sydney Basin as a template for their conservation and management

ABSTRACTTemperate Highland Peat Swamps on Sandstone (THPSS) and Coastal Upland Swamps in the Sydney Basin (CUSSB) are listed as endangered ecological communities under Australia's national and state legislation. They are threatened by a range of human and climate impacts. Across the region there are 3208 individual, valley-bottom, elongate-shaped, upland swamps that drain first- or second-order drainage lines and small catchment areas (mean = 0.25 km2). They occur at a median distance of 57 km from the coast in areas with an average annual rainfall of 1505 mm/year and average annual temperature of 15°C. Those closer to the coast occur on elevations as low as 160 m a.s.l., and those further from the coast, on plateau country, occur up to 1172 m a.s.l. (median 634 m a.s.l.). The valleys that contain these swamps terminate downstream at a valley constriction or bedrock step, behind which alluvial materials have accumulated, and peat has formed to produce relatively steep swamps (median slope 6.2 per cent). Understanding the spatial distribution and physical attributes of these systems, and having the accompanying maps as a resource, is critical for development of sound, well-informed conservation, rehabilitation and monitoring programs, and for analysing the ecosystem services they provide.

Mineralogy and geochemistry of the Lokoundje alluvial clays from the Kribi deposits, Cameroonian Atlantic coast: Implications for their origin and depositional environment

The Lokoundje alluvial clay deposits are located at the left floodplain of the Lokoundje River, towards the estuary in the Kribi region. The mineralogical and geochemical features of the Lokoundje River fine-grained sediments have been reported using XRD, XRF, ICP-MS, and IR instruments in order to understand their provenance and depositional history. The Lokoundje watershed covers a surface area of about 5381 km2. The basement of this watershed is made up of gneisses, amphibolites, migmatites, charnockites, and pyroxenites from the Nyong and Ntem units, in the NW border of the Congo craton. The alluvial materials are about 100 cm thick and cover a total area of 1.4 km2. They are mainly plastic clays with silty-clayey texture and four colors (yellow, red yellow, white, and light grey). The mineral assemblage is composed of kaolinite, quartz, illite, gibbsite, goethite, rutile, and interstratified illite-vermiculite. The infra-red data associated with those of XRD portray the disordering of kaolinite. These materials are mostly constituted by SiO2 (44.33–69.19 wt%, av. = 51.17 wt% with n = 18) and Al2O3 (20.69–30.26 wt%, av. = 26.07 wt%) with very low Fe2O3 contents (1–7.71 wt%, av. = 3.35 wt%). The SiO2/Al2O3 ratio range between 1.46 and 4.1 (av. = 2.06). The alkali contents (Na2O + K2O) are below 5 wt%. ICV, CIA, PIA, and SiO2/Al2O3 portray high degree of chemical weathering in the source area as well as the maturity of sediments. The trace element behavior is quite different probably due to the mixed source rocks; Ba, Sr, Zn have high contents while several elements such as Th and U show low contents. The REE contents are also variable; their concentrations vary between 92 and 1065 ppm (av. = 307 ppm). The mineral assemblage associated with the geochemical data reveal that REE are mainly housed in clay minerals. The behavior of REE is also marked by the abundance of LREE (LREE/HREE = 19.69–34.62). The REE chondrite-normalized spectra confirm the LREE-abundance and exhibit negative Eu anomalies. The PAAS-normalized patterns reveal slight positive Eu anomalies and negative Ce anomalies. The (La/Yb)N values (3.30–8.43, av. = 5.71) display low degree of REE-fractionation in the Lokoundje watershed. The morphological, mineralogical, and geochemical features reveal that the fine-grained sediments derive from the intense weathering of mixed source. The disordering of kaolinite confirms that sediments were sorted during a long transportation before their deposition under oxic conditions (U/Th < 1.25; V/Cr < 2) in the floodplains near the Atlantic coast.

Avaliação de multiabordagem da distribuição espacial do rendimento específico: aplicação no aquífero da planície do Crau, França

Spatially distributed values of the specific yield, a fundamental parameter for transient groundwater mass balance calculations, were obtained by means of three independent methods for the Crau plain, France. In contrast to its traditional use to assess recharge based on a given specific yield, the water-table fluctuation (WTF) method, applied using major recharging events, gave a first set of reference values. Then, large infiltration processes recorded by monitored boreholes and caused by major precipitation events were interpreted in terms of specific yield by means of a one-dimensional vertical numerical model solving Richards’ equations within the unsaturated zone. Finally, two gravity field campaigns, at low and high piezometric levels, were carried out to assess the groundwater mass variation and thus alternative specific yield values. The range obtained by the WTF method for this aquifer made of alluvial detrital material was 2.9– 26%, in line with the scarce data available so far. The average spatial value of specific yield by the WTF method (9.1%) is consistent with the aquifer scale value from the hydro-gravimetric approach. In this investigation, an estimate of the hitherto unknown spatial distribution of the specific yield over the Crau plain was obtained using the most reliable method (the WTF method). A groundwater mass balance calculation over the domain using this distribution yielded similar results to an independent quantification based on a stable isotope-mixing model. This agreement reinforces the relevance of such estimates, which can be used to build a more accurate transient hydrogeological model.

Technological aspects of Middle Bronze Age II production of pithoi at Tel Kabri, Israel: specialized pottery production in a palatial system

A study of pithoi production technology at the Middle Bronze Age Canaanite palace at Tel Kabri, Israel, utilized experimental and analytical methods. Pithoi from two phases of the palace were produced using local alluvial raw material, by coil/slab technique, and finished on a slow wheel. Firing at c. 600°C for a short duration seems to be related to the potters’ knowledge of the limitations of the raw material used, further indicating no significant environmental effect despite growing palatial demand. Differences in pithos rims, sizes and contexts may relate to various consumption patterns in the earlier and later phases of activity at the palace.

GEOHAZARDS IN SANDAKAN TOWN AREA, SABAH, MALAYSIA

The geology of the Sandakan town area provides a favourable setting for geomorphological hazards occurrences. The exposed rocks in the study area and its surrounding vary in types and ages, from Late Eocene-Early Miocene Neogene’s clastic sediment of the Garinono Formation, the Sandakan Formation and Volcanic Facies to vary recent Quaternary alluvial materials which are still being deposited. These rock units are dissected by numerous lineaments with complex structural styles developed during series of regional Tertiary tectonic activities. Rapid urbanization activities have caused changes in the land use. Urbanization processes may contribute to the exposure of impervious surface, loss of vegetation cover, modification of slope gradient and drainage systems. The last decade has seen slope failure, flash flood and erosion events, which have claimed lives, damaged properties and increased the cost of maintenance. The main factors causing geomorphological hazards occurrences in the study area are natural (geology, meteorology, topography and drainage system) and human factors (lack of proper planning, human activities and community’s attitude). Serious efforts to increase the community’s awareness to geomorphological hazards occurrences and reconstruction of natural ecosystem must be taken. To handle this issue, both prevention and mitigation are necessary. At the planning level a multi disciplinary approach to zoning, risk assessment and design with construction practices is recommended. This is to ensure that future activities will not cause further damage to natural environmental condition or ecosystem.