Assessment of Aquifer Storage and Recovery (ASR) feasibility at selected sites in the Emirate of Abu Dhabi,UAE

Aquifer storage and recovery (ASR) is considered as a strategy for the storage of water to ensure a sustainable water supply in the Abu Dhabi emirate. Earlier investigations have been conducted, and two sites were proposed for the installation of ASR in the surficial aquifer. Recently, the site located in the center of Abu Dhabi (sand dune area) was executed, and the second site is undergoing the pilot phase of the study. However, the performance and influence of the regional groundwater system may vary depending on regional hydrogeological characteristics, which have not been investigated. Hence, this study attempts to understand the feasibility of the proposed ASR sites in the surficial aquifer using a regional model developed by the finite-difference approach with an accuracy of 0.28 m mean residual difference. Additionally, six sites were selected on the basis of the literature and aquifer parameters and were investigated for their suitability for future ASR installation. Six cycles of injection and recovery at various rates were analyzed at each ASR site by using a transient calibrated model until the end of the year 2030. The area of influence is axisymmetrical in the sand dune area and non-symmetrical in the east and northeastern areas because of the steep topography and groundwater table gradient. At the sites that possess a non-symmetrical influence, the area of influence is always high upstream of the groundwater flow. Heterogeneity-induced variation in the fluctuation of the groundwater table is noted in all sites. Even with 100% recovery, the groundwater table did not reach the ambient groundwater table during the recovery period. This finding confirms the contribution of regional groundwater to the site during recovery. All sites selected for future ASR installation, except site 5, are capable of storing the volume needed to meet expected water demand. Site 2 is considered the most suitable site for ASR installation in the future. This study will facilitate the scientific communities and authorities in understanding the feasibility of ASR installation for sustainable water storage and supply in the Abu Dhabi emirate.     

Sedimentary evidence for deforming bed conditions associated with a grounded Irish Sea glacier,southern Ireland

Along the south coast of Ireland, a shelly diamict facies, the Irish Sea Till, has been variously ascribed to subglacial deposition by a grounded Irish Sea glacier or to glacimarine sedimentation by suspension settling and iceberg rafting. Observations are presented here from five sites along the south coast to directly address this question. At these sites, sedimentary evidence is preserved for the onshore advance of a grounded Irish Sea glacier, which glacitectonically disturbed and eroded pre‐existing sediments and redeposited them as deformation till. Recession of this Irish Sea glacier resulted in the damming of ice‐marginal lakes in embayments along the south coast, into which glacilacustrine sedimentation then took place. These lake sediments were subsequently glacitectonised and reworked by overriding glacier ice of inland origin, which deposited deformation till on top of the succession. There is no evidence for deposition of the Irish Sea diamicts by glacimarine sedimentation at these sites. The widespread development of subglacial deforming bed conditions reflected the abundance of fine‐grained marine and lacustrine sediments available for subglacial erosion and reworking. Stratigraphical and chronological data suggest that the advance of a grounded Irish Sea glacier along the south coast occurred during the last glaciation, and this is regionally consistent with marine geological data from the Celtic Sea. These observations demonstrate extension of glacier ice far beyond its traditional limits in the Celtic Sea and on‐land in southern Ireland during the last glaciation, and remove the stratigraphical basis for chronological differentiation of surficial glacial drifts, and thus the Munsterian Glaciation, in southern Ireland. Copyright © 2001 John Wiley & Sons, Ltd.     

Source of paleo-groundwater in the Emirate of Abu Dhabi, United Arab Emirates: evidence from unusual oxygen and deuterium isotope data

Paleo-groundwaters of 6000?years BP from the Liwa water-table sand dune aquifer in the Rub al Khali and the Gachsaran artesian carbonate aquifer, on the coast of the Emirate of Abu Dhabi (UAE), exhibit normal ??²H/??¹⁸O slopes, modest ??¹⁸O increases, and large negative deuterium excess ??d?? (Liwa aquifer: 2.19?? VSMOW and d?=??C15; Gachsaran aquifer: 3.16?? VSMOW and d?=??C28) compared to local Shamal precipitation (0.05?? VSMOW and d?=?7). This unusual isotopic signature is hypothesized to result from re-evaporation of continental runoff to the Red Sea catchment basin. It is postulated that this continental water flowed onto the surface of the Indian Ocean providing a moisture source for the monsoon that dominated precipitation during this, the last wet period in the area from 5000 to 9000 BP. Carbonate precipitation, forming speleothems, travertines, tufas, lacustrine, and capillary-zone deposits, subsequently record this ??¹⁸O isotopic signature. This rock record is thus dominated by the water source, rather than environmental conditions of deposition normally assumed to control the rock ??¹⁸O isotopic signature. As a consequence, re-evaluation of paleo-climate??¹⁸O data from the rock record may be necessary for this time period in southern Arabia.     

Timing of Lateglacial vegetation dynamics and respective palaeoenvironmental conditions in southern Estonia: evidence from the sediment record of Lake Nakri

This paper investigates a detailed well‐dated Lateglacial floristic colonisation in the eastern Baltic area, ca. 14 000–9000 cal. a BP, using palynological, macrofossil, loss‐on‐ignition, and ¹⁴C data. During 14 000–13 400 cal. a BP, primarily treeless pioneer tundra vegetation existed. Tree birch (Betula sect. Albae) macro‐remains and a high tree pollen accumulation rate indicate the presence of forest‐tundra with birch and possibly pine (Pinus sylvestris L.) trees during 13 400–12 850 cal. a BP. Palaeobotanical data indicate that the colonisation and development of forested areas were very rapid, arising within a period of less than 50 years. Thus far, there are no indications of conifer macrofossils in Estonia to support the presence of coniferous forests in the Lateglacial period. Signs of Greenland Interstadial 1b cooling during 13 100 cal. a BP are distinguishable. Biostratigraphic evidence indicates that the vegetation was again mostly treeless tundra during the final colder episode of the Lateglacial period associated with Greenland Stadial 1, approximately 12 850–11 650 cal. a BP. This was followed by onset of the Holocene vegetation, with the expansion of boreal forests, in response to rapid climatic warming. Copyright © 2011 John Wiley & Sons, Ltd.     

Diagenesis of Holocene beachrocks: a comparative study between the Arabian Gulf and the Gulf of Aqaba,Saudi Arabia

Beachrocks occur in present-day intertidal zones of the Arabian Gulf and the Gulf of Aqaba, on the eastern and northwestern coasts, respectively, of Saudi Arabia. The beachrocks occur as linear patches within beach deposits, which have variable grain size and detrital compositions. The Arabian Gulf beachrocks are composed of sand-sized bioclasts and siliciclastic grains, whereas the Gulf of Aqaba beachrocks are composed of sand- to pebble-size grains, which are dominated by igneous rock fragments and small amounts of skeletal carbonate grains. The cement includes micritic high-magnesian calcite and isopachous acicular/bladed aragonite. In addition to cements, intergranular pores are locally filled by a lime–mud matrix. Radiocarbon dating of beachrock samples from the Arabian Gulf yielded ages from ca. 655 to 2185 year bp, whereas the Gulf of Aqaba samples range in age between 2745 and 5075 year bp.     

Accumulation and distribution of Hg and 210Pb in superficial sediments from a coastal lagoon in the SE Gulf of California associated with urban-industrial and port activities

The Estero de Urías Lagoon (EUL) is an inner shelf barrier coastal lagoon, located in the Mexican Pacific Coast (SE Gulf of California). It is surrounded by Mazatlán City, one of the most important international tourist areas of Mexico. To provide a comprehensive reassessment of the concentration levels and spatial variability of Hg and ²¹⁰Pb in the EUL, 40 surface sediment samples were analyzed for several geochemical variables (e.g. grain size distribution, organic matter and reference element concentrations) that could explain the observed variability of Hg and ²¹⁰Pb. The Hg concentrations ranged from 23 to 214 ng g^?1, whereas ²¹⁰Pb activities varied from 20 to 56 Bq kg^?1. No defined distribution pattern was observed for Hg and ²¹⁰Pb concentrations in the lagoon and no evidence of a common atmospheric delivery route was observed. The sediments from EUL were found contaminated by Hg, and according to international guidelines 48 % of the sampling sites have concentrations that could be harmful to biota.     

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf,southern Italy)

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.     

Mantle derivation of Archean amphibole-bearing granitoid and associated mafic rocks: evidence from the southern Superior Province,Canada

Amphibole-bearing, Late Archean (2.73–2.68 Ga) granitoids of the southern Superior Province are examined to constrain processes of crustal development. The investigated plutons, which range from tonalite and diorite to monzodiorite, monzonite, and syenite, share textural, mineralogical and geochemical attributes suggesting a common origin as juvenile magmas. Despite variation in modal mineralogy, the plutons are geochemically characterized by normative quartz, high Al₂O₃ (> 15 wt%), Na-rich fractionation trends (mol Na₂O/K₂O >2), low to moderate Rb (generally<100 ppm), moderate to high Sr (200–1500 ppm), enriched light rare earth elements (LREE) (Ce_N generally 10–150), fractionated REE (Ce_N/Yb_N 8–30), Eu anomaly (Eu/Eu^*) 1, and decreasing REE with increasing SiO₂. The plutons all contain amphibole-rich, mafic-ultramafic rocks which occur as enclaves and igneous layers and as intrusive units which exhibit textures indicative of contemporaneous mafic and felsic magmatism. Mafic mineral assemblages include: hornblende + biotite in tonalites; augite + biotite ± orthopyroxene ± pargasitic hornblende or hornblende+biotite in dioritic to monzodioritic rocks; and aegirine-augite ± silicic edenite ± biotite in syenite to alkali granite. Discrete plagioclase and microcline grains are present in most of the suites, however, some of the syenitic rocks are hypersolvus granitoids and contain only perthite. Mafic-ultramafic rocks have REE and Y contents indicative of their formation as amphibole-rich cumulates from the associated granitoids. Some cumulate rocks have skeletal amphibole with X_Mg(Mg/(Mg+ Fe²⁺)) indicative of crystallization from more primitive liquids than the host granitoids. Geochemical variation in the granitoid suites is compatible with fractionation of amphibole together with subordinate plagioclase and, in some cases, mixing of fractionated and primitive magmas. Mafic to ultramafic units with magnesium-rich cumulus phases and primitive granitoids (mol MgO/ (MgO+0.9 FeO^TOTAL) from 0.60 to 0.70 and C_T >150 ppm) are comagmatic with the evolved granitoids and indicate that the suites are mantle-derived. Isotopic studies of Archean monzodioritic rocks have shown LREE enrichment and initial ¹⁴³Nd/¹⁴⁴Nd ratios indicating derivation from mantle sources enriched in large ion lithophile elements (LILE) shortly before melting. Mineral assemblages record lower P_H2O with increased alkali contents of the suites. This evidence, in conjunction with experimental studies, suggests that increased alkali contents may reflect decreased P_H2O during mantle melting. These features indicate that 2.73 Ga tonalitic rocks are derived from more hydrous mantle sources than 2.68 Ga syenitic rocks, and that the spectrum of late Archean juvenile granitoid rocks is broader than previously recognized. Comparison with Phanerozoic and recent plutonic suites suggests that these Archean suites are subduction related.     

Slip rates on the Helike Fault, Gulf of Corinth, Greece: new evidence from geoarchaeology

Palaeoseismological and archaeological analysis of a trench enabled us to estimate the Holocene slip rates on the East Helike Fault, flanking the south-western Gulf of Corinth. We recognized two major fault strands within the trench: the ‘north fault’ controls a succession of three colluvial wedges and the deposition of a 2.7 m thick sedimentary sequence. The ‘south fault’ controls the deposition of a 2.9-m thick brownish-red colluvium. Based on colluvial stratigraphy, radiocarbon dating of the sediments suggests that the slip rate was c. 0.3 mm yr⁻¹ from 10 250 to c. 1400 bp , when it increased dramatically to c. 2.0 mm yr⁻¹ after a strong earthquake event near 1400 bp . The faster slip rate evidently increased the sedimentation rate.     

The effects of oasis on aeolian deposition under different weather conditions: a case study at the southern margin of the Taklimakan desert

Heavy aeolian deposition is one of the most threatening natural hazards to oases in arid areas. How an oasis affects aeolian deposition is tightly related to the local ecological environments. To examine the effects of oasis on aeolian deposition under different weather conditions, monthly aeolian deposition from April 2008 to March 2009 and additional samples during dust storms in April and May 2008 were collected at four sites along the Qira oasis. The monthly ADRs (aeolian deposition rates) varied greatly with seasons and sites, ranging from 19.4 to 421.2 g/m²/month and averaging 198.8 g/m²/month. Aeolian deposition in the oasis was composed dominantly of sand and silt. Based on the variations of ADRs from the four sites, it can be found that the oasis exhibits two different effects on aeolian deposition under different weather conditions. During dust storms, the oasis demonstrates a significantly shielding effect due to the obstruction of the oasis-protection systems, resulting in most aeolian particles being deposited at the windward side of the oasis. While during non-dust storm periods with weak winds, the oasis exhibits an “attracting” effect on aeolian deposition, leading to a higher ADR inside the oasis. Owing to the annual ADR is dominated by the non-dust storm ADR in Qira, the oasis seems to become an important aeolian deposition area caused by the “attracting” effect of the oasis.     

Late Holocene Neoglacial conditions from the Lesotho highlands, southern Africa: phytolith and stable carbon isotope evidence from the archaeological site of Likoaeng

The late Holocene environmental history of the Lesotho highlands, southern Africa, is poorly understood with few detailed studies to date. At Likoaeng, Senqu Valley, Lesotho, a 3 m stratified sedimentary sequence from an open-air archaeological site records vegetation development for the period 3400-1070 cal. BP. Phytolith analyses and bulk sediment organic matter δ¹³C indicate that C₄ grassland dominated the lower part of the sequence until approximately 2960 cal. BP when there was a switch to C₃ Pooid grassland (2960-2160 cal. BP). Also noted was a change from hunting mainly bovids to a dominance of fishing at the site. The change in grassland type and archaeological subsistence strategies corresponds with an episode of neoglacial cooling and the expansion of Alpine sourgrasses into lower altitudes. From 2160 to 1600 cal. BP grassland became a mix of C₃ and C₄ types and by 1600-1070 cal. BP there was a return to C₄ dominated grassland. During this latter phase there was a reversal from fishing to hunting again (and eventually some keeping of domestic livestock) at the site. These data outline the vegetation response to latitudinal shifts of frontal systems, and relatively strong atmospheric circulation variability, perhaps underpinned by variations of polar water into the Benguela Current during the late Holocene.     

Development of an incised valley‐fill at an evolving rift margin: Pleistocene eustasy and tectonics on the southern side of the Gulf of Corinth,Greece

This study from the southern margin of the Gulf of Corinth documents a Late Pleistocene incised valley‐fill succession that differs from the existing facies models, because it comprises gravelly shoal‐water and Gilbert‐type deltaic deposits, shows strong wave influence and lacks evidence of tidal activity. The valley‐fill is at least 140 m thick, formed in 50 to 100 ka between the interglacials Marine Isotope Stage 9a and Marine Isotope Stage 7c. The relative sea‐level rise left its record both inside and outside the incised valley, and the age of the valley‐fill is estimated from a U/Th date of coral‐bearing deposits directly outside the palaeovalley outlet. Tectonic up‐warping due to formation of a valley‐parallel structural relay ramp contributed to the valley segmentation and limited the landward extent of marine invasions. The valley segment upstream of the ramp crest was filled with a gravelly alluvium, whereas the downstream segment accumulated fluvio‐deltaic deposits. The consecutive deltaic systems nucleated in the ramp‐crest zone, forming a bathymetric gradient that promoted the ultimate growth of thick Gilbert‐type delta. The case study contributes to the spectrum of conceptual models for incised valley‐fill architecture. Four key models are discussed with reference to the rates of sediment supply and accommodation development, and it is pointed out that not only similarity, but also all departures of particular field cases from these end‐member models may provide valuable information on the system formative conditions. The Akrata incised valley‐fill represents conditions of high sediment supply and a rapid, but stepwise development of accommodation that resulted from the spatiotemporal evolution of normal faulting at the rift margin and overprinted glacioeustatic signals. This study adds to an understanding of valley‐fill architecture and provides new insights into the Pleistocene tectonics and palaeogeography of the Corinth Rift margin.     

The palaeoenvironment associated with a partial Iguanodon skeleton from the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks (Ockley, Surrey, UK), based on palynomorphs and ostracods

In 2001 a partial skeleton of an Iguanodon was discovered in the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks near Ockley, Surrey, UK. When the dinosaur was excavated, a detailed stratigraphic section was logged and 25 samples taken for palynological and micropalaeontological (ostracod and megaspore) analysis, including a detailed sample set of the dinosaur bed itself. Qualitative and quantitative analysis of the palynoflora revealed rich and well-preserved non-marine assemblages of pollen and spores, including early angiosperms, and freshwater green algae. Four types of angiosperm pollen are described and assigned to the genus Retimonocolpites Pierce, 1961, but left in open nomenclature. Some marine elements such as dinoflagellate cysts are identified as the result of reworking of Middle and Upper Jurassic sediments. The pollen/spore assemblages depict a vegetational change from principally gymnosperm-dominated assemblages at the base to principally pteridophyte-dominated assemblages at the top of the section. The dinosaur bed shows a pteridophyte-dominated assemblage, with a significantly high amount of the freshwater green alga Scenedesmus novilunaris He Cheng-quan et al., 1992. Samples close to the dinosaur bed yielded the first useful ostracod finds from Smokejacks Brickworks: well-preserved assemblages containing Cypridea clavata (Anderson, 1939), Damonella cf. pygmaea (Anderson, 1941), Stenestroemia cf. cressida Anderson, 1971 and Stenestroemia sp. A, and fragments and damaged valves of a thin-shelled ostracod, possibly belonging to Mantelliana Anderson, 1966. Those identified as Cypridea clavata show a wide range of morphological variety and in opposition to Anderson's (1967, 1985) taxonomic scheme, which would assign them to up to five different taxa, they are considered to be intraspecific variants of a single species. The possibilities and limitations of age determination of the Wealden sediments using palynomorphs and ostracods are discussed; distinct forms of early angiosperm pollen, together with the ostracod fauna, are consistent with an early Barremian age. Pollen and spores are discussed in terms of their parent plants and the reconstruction of vegetation and palaeoclimate. Palynology and ostracods give evidence for temporary freshwater conditions at the time when the Iguanodon died and the carcase was buried.     

Anthropogenic and natural metal contents of coastal sediments with potential transfer to associated waters: the case of El Melah lagoon near Slimane,Tunisia

Cu, Zn, Ni, Cr and Co pollution of El Melah lagoon waters near the city of Slimane in northwestern Tunisia was evaluated relative to identified human activity and waste repositories in the neighborhood. These metals were measured in lagoon waters and sediments, and in the potential pollutants, during two consecutive years for evaluation of their impact on the lagoon waters. A sequential extraction of the metals from sediments was designed to distinguish those potentially anthropogenic from those naturally scavenged by the sediments. This procedure allowed identification and quantification of the metals that are temporarily trapped, therefore contributing directly to the ecotoxicity of the lagoon waters, from those incorporated in the sediments. The highest supplies of Cr and Co to the lagoon waters come from El-Bey creek waters, while the wastewater treatment plant contributes for most of the Zn, and the urban garbage deposit for most of the Ni. Alternatively, the impact of the cultivated soils is minimal for the studied metals. In fact, Zn and Ni contents of the sediments amount 100 to 20 times less than in the present water, which is negligible. Cr is potentially the most polluting with contents up to ten times more in the sediments of the eastern lagoon pool and next to the outlet of the wastewater plant than in the waters. Potentially, contents of the anthropogenic Cu of the sediments amount 3–15 times less than in the lagoon waters.     

Geochemistry of a paleosol horizon at the base of the Sausar Group,central India: Implications on atmospheric conditions at the Archeane Paleoproterozoic boundary

A paleosol horizon is described from the contact of the Sausar Group(w2400 Ma) and its basement(Tirodi Gneiss; 2500 Ma) in Central India. Physical evidence of pedogenesis is marked by the development of stress corrosion cracks, soil peds, corestone weathering and nodular rocks. XRD and SEM-EDX data indicate the presence of siderite, ankerite, uraninite, chlorite, alumino-silicate minerals, ilmenite,rutile and magnetite, in addition to quartz, feldspar and mica. The chemical index of alteration, the plagioclase index of alteration, and the chemical index of weathering show an increasing trend from parent rock to the paleosol and indicate a moderate trend of weathering. The A-CN-K plot indicates loss of feldspars, enrichment in Al2O3 and formation of illite. Different major element ratios indicate baseloss through hydrolysis, clay formation, leaching of some elements, and more precipitation with good surface drainage. The paleosol is depleted in HREE in comparison to the parent rock indicating high fluid-rock interaction during weathering. The paleosol samples show flat Ce and Eu anomalies, low SREE, and high(La/Yb)N, indicative of a reducing environment of formation. Reducing condition can also be inferred from the concentration of elements such as V, Co, Cu, Pb, and Zn in the paleosol profile. Although enriched in Fe and Mg, the overall geochemical patterns of the paleosol indicate oxygen deficient conditions in the atmosphere and development by weathering and leaching processes associated with high precipitation and good surface drainage at the time of development of this paleosol during the Archeane Paleoproterozoic transition.     

Variation of the chemical composition of sediments under middle- and low-temperature hydrothermal conditions in the southern trough of Guaymas Basin,Gulf of California: Communication 2. Results of the study of grain size fractions of sediments

The chemical composition of grain size fractions of the Upper Pleistocene sediments in the southern trough of Guaymas Basin (Gulf of California) is studied based on materials from DSDP Hole 477 (191 m). The sediments are located in the upper part of the main long-lived hydrothermal system. Therefore, they were subjected to long-term reworking by the middle- and low-temperature solutions (100?300°C) and short-term hydrothermal impact during the intrusion of basalt sills. The upper part of the main hydrothermal system is divided into three middle- to low-temperature hydrothermal alteration zones: lower (III), middle (II), and upper (I). In zone III (250?300°C), hydrothermal alterations of sediments are most significant. The coarsegrained fractions are enriched in Fe, S, Ni, Cu, Zn, Mo, Co, Se, Cd, Bi, Pb, and Ag due to the formation of sulfides and precipitation of native metals. The silt fractions are enriched in Be, Sc, Nb, Ta, W, Th, U, Y, and REE. In contrast, the pelite fractions are depleted in most of these elements. The fine-dispersed (<0.001 mm) pelite fractions are appreciably enriched in Mg (due to the formation of the authigenic Mg-chlorite), as well as MnO, Cr, V, Ga, Pb, and Zr. Virtually all grain size fractions are depleted in K₂O, Li, Rb, Cs, and Tl due to the dissolution of the K-bearing terrigenous minerals. In zones II (146?170 m) and I (110?146 m), where the temperature of hydrothermal solutions dropped successively from 250 to 180?195 and 100°C, the sedimentary environment was unfavorable for the concentration of Fe, S, and a large group of ore elements that are typical for sediments in zone III. Intrusion of basalt sills and a short-term hydrothermal impact changed concentrations of several components in the sediments overlying the sill complex: CaO, K₂O, Li, Rb, Cs, and Tl acquired a trend typical of the high-temperature lower zone III, whereas Fe, MgO, P₂O₅, TiO₂, V, Sc, and Y distribution pattern became typical of the low-temperature upper zone I. Significant compositional variations in the grain size fractions of sediments are lacking beneath the sill base.     

Quantitative studies of weathering in saprolitized charnockites associated with a landslip zone at the porthimund dam,India

Studies on saprolitized charnockites associated with a landslip observed in the Blue Mountains in close proximity of the Porthimund Dam (11°22'E 76°34′30″N), Nilgiris District, Tamilnadu State, South India, are reported.Laboratory investigations of the geotechnical properties were carried out to evaluate the nature and degree of weathering quantitatively for estimating the soundness of the charnockites constituting the slip zone. The results of per cent decomposed product of the crest, scarp and toe portions of the slip denote positive correlations with porosity and compressibility; and negative correlations against density, wave velocity, Young's modulus, compressive strength and tensile strength. It is also seen that in the absence of the information on decomposed product, weatherability could still be evaluated considering the per cent change of any physical parameter.Such studies should prove valuable in the mapping of weatherability zones and the assessment and determination of foundation conditions.     

Lower Aptian Subbetic organic-rich facies, radiolarites, and associated deposits: the local expression of Oceanic Anoxic Event 1a (Carbonero Formation, southern Spain)

The Carbonero Formation represents a scarce, well documented example of Aptian anoxic facies in the Betic Cordillera. Generally, the Aptian record in the pelagic Subbetic basin is both very discontinuous and affected by frequent hiatuses, but in some subsident areas controlled by extensional faults (as in the Carbonero trough) an interesting record is preserved. The Carbonero Formation is characterised by a thick pelagic succession composed of marls with intercalations of calcareous turbidites and a thick interval of anoxic facies. This interval, dated as early Aptian, most likely represents the local expression of Ocean Anoxic Event 1a in the Subbetic basin. A multidisciplinary study including lithostratigraphy, biostratigraphy, and sedimentology has been carried out in the Carbonero Formation, with special attention to the anoxic interval. A collection of facies and sedimentary features has been characterised and interpreted, including barite concretions, calcareous concretions, black shales, siliceous marls and radiolarites, and calcareous turbidites. All these facies seem to have been deposited under oxygen-depleted conditions on a fault-bounded depression with a high subsidence rate. The accumulation and burial of sediments and the preservation of organic matter were controlled by both local and regional factors, such as the physiography of the basin and tectonic setting, as well as by global factors, such as palaeoceanographic and climatic changes.