sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

characterization of organic matter in the oligocene chattian turbiditic fine grained deposits offshore angola variations in the abundance and gross composition of the organic matter om content of fine grained turbiditic chattian sediments off angola were explored with rock eval pyrolysis of 216 core samples from four wells the study revealed that the om in the sediments is immature but is present in sufficient abundance 1 total organic carbon toc and with a good enough quality hydrogen index hi around 185 mg hydrocarbon g toc on average to constitute a potential source rock a deeper insight into the composition of the om was provided by the extraction and analysis of the kerogen from 15 samples these samples were submitted to visual inspection and the counting of organic particles under the microscope palynofacies analysis elemental analysis and pyrolysis gas chromatography mass spectrometry gc ms although individually the various observations did not provide evidence clearly diagnostic of the origin of the om they confirm that it has a mixed marine terrestrial origin a notable part of the terrestrial contribution very probably originating from leaves the good buoyancy of the om and its richness in lipid components might explain the spreading of terrestrial om over a large area and its relatively good oil potential

relationships between heavy metals distribution and organic matter cycling in mangrove sediments conception bay new caledonia mangroves of new caledonia act as a buffer between a lagoon of more than 20 000 km2 and the island which suffers intense processes of erosion resulting from urbanization and natural resources exploitation this preliminary study aims at determining how heavy metals are distributed in mangrove sediments and pore waters in relationship with their organic content to reach our goal a series of 50 cm deep cores were collected in the mangrove of conception bay the various coring sites are representative of live forests avicennia marina rhizophora stylosa dead forest and intertidal unvegetated area the ranges of concentrations in sediments were the following mol g 1 cu 0 08 to 0 51 co 0 01 to 0 38 ni 0 03 to 3 55 cr 0 36 to 3 11 zn 0 68 to 2 36 mn 1 13 to 5 0 and fe 22 64 to 721 69 heavy metals distribution within sediments and pore water appear to result from diagenetic processes linked to om decomposition beneath the dead avicennia forest and in the unvegetated sediments the higher the organic content the higher the metal concentration in the solid phase beneath living mangrove stands despite a higher organic content as well as higher sulphur content heavy metals concentrations were not higher than those measured in the other sampling sites beneath these forests redox conditions were mainly controlled by the length of waterlogging and the activity of root system we suggest that because of the specificity of the avicennia root system and its position in the intertidal zone heavy metals are more bioavailable and potentially more mobile than beneath rhizophora stand

arid zone groundwater recharge and salinisation processes an example from the lake eyre basin australia in arid central australia the 1 14 m km2 endorheic lake eyre basin leb experiences sporadic floods and contains saline shallow groundwater in this basin where on ground physical and chemical data are very sparse new observations of major ion chemistry stable isotopes 2h 18o 13c radiogenic isotopes 3h 14c and remote sensing modis data were used to investigate groundwater recharge and salinisation processes in 2006 2007 in january 2007 there was a large and intense local rainfall event followed by flooding to the normally dry lake eyre resulting from heavy rainfall in the northern leb that took 2 months to arrive at lake eyre groundwater chemistry from this study show no evidence of recharge from the floodwaters or the local rainfall however this does not preclude the process low transit times and low infiltrating volumes may mean that the recharge event has not yet been detected over the longer term the stable isotope chemistry indicates that groundwater is predominantly diffusely recharged during heavy local rainfall events 100 150 mm month and radiogenic isotopes reflect an older shallow groundwater efficiently mixing with recent decadal recharge the high total dissolved solids tds of regional shallow groundwater up to 52 5 g l is intrinsically linked with these recharge processes where infiltrating diffuse rainfall is evaporated and heavy rainfall events transport saline pore water saline due to evaporation in the unsaturated zone to the groundwater system the high tds of shallow groundwater beneath the dry lake eyre bed up to 322 g l is also controlled by evaporation however although evaporite minerals are prolific in the lake area the non conservative behaviour of br in pore water limits analysis of the role of halite mineral dissolution and precipitation reactions controlling groundwater salinity evaporation driven salinisation of shallow groundwater in arid central australia is distinct from the transpiration driven salinisation of groundwater in the australian murray basin located in a semi arid climate and results in relatively high groundwater salinity values compared with many other large arid zone endorheic basins across the world

environmental geochemistry of core sediments from serthalaikkadu creek east coast of india the serthalaikkadu creek in muthupet mangroves region is the only e w trending coastal strip in the se coast of india and it also acts as a barrier to natural disasters natural anthropogenic signals and accumulation of elements were studied by collecting sediments from two cores textural parameters were studied in detail and carbonates caco3 organic carbon oc major si al fe na k ca mg p and trace elements mn cr cu ni co pb zn were determined textural parameters caco3 oc and al normalized pattern of elements indicate depositional events in core samples that can be directly related to natural events during the last decade the calculated enrichment anthropogenic factors and comparison of data indicate that the observed trace metals especially pb co are enriched mainly due to the anthropogenic activities in the land as well as in the coastal zone palk strait

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

hydrogeochemistry and arsenic contamination of groundwater in the rayen area southeastern iran high as contents in groundwater were found in rayen area and chosen for a detailed hydrogeochemical study a total of 121 groundwater samples were collected from existing tube wells in the study areas in january 2012 and analyzed hydrogeochemical data of samples suggested that the groundwater is mostly na cl type also nearly 25 62 of samples have arsenic concentrations above who permissible value 10 g l for drinking waters with maximum concentration of aqueous arsenic up to 25 000 g l the reducing conditions prevailing in the area and high arsenic concentration correlated with high bicarbonate and ph results show that arsenic is released into groundwater by two major phenomena 1 through reduction of arsenic bearing iron oxides oxyhydroxides and fe may be precipitated as iron sulfide when anoxic conditions prevail in the aquifer sediments and 2 transferring of as into the water system during water acidic volcanic rock interactions

significance of first order faults in folding mechanically isotropic layers evidence from the sudbury basin canada abstract the sudbury basin is a non cylindrical fold basin demarcated by the layered sudbury igneous complex sic the eastern part of which is transected by prominent curved faults folding of the sic and adjacent rock units occurred in the brittle field and is peculiar due to its petrographically distinct but initially mechanically similar layers overall the layers are characterized by low levels of solid state strain raising the question how the layer contacts acquired their curvature we addressed this question by developing a g i s based workflow to analyze the orientation and slip vectors of the faults slip vectors form clusters of normal and reverse slip along a given fault the clustering is best interpreted in terms of successive slip events during folding of the sic as the faults formed most likely as planar reverse faults prior to folding of the sic they subsequently served as mechanically anisotropic elements to fold the sic the results contribute to 1 better understand the folding mechanisms of thick melt sheets in the upper crust 2 explain apparently incompatible principal strain axes during progressive deformation and 3 efficiently analyze the orientation and kinematics of fault zones close to the earth s surface

geochemistry of core sediments from mullipallam creek south east coast of india the mullipallam creek in muthupet mangroves region is the only e w trending coastal strip in the se coast of india and is very important as the mangrove acts as a barrier to natural diasters natural anthropogenic signals and accumulation of elements were made by collecting sediment samples at various depths in a core all sediments were analyzed for carbonates caco3 organic carbon oc major si al fe na k ca mg p and trace mn cr cu ni co pb zn normalization with al values has been done for all the major and trace elements and enrichment factors have been calculated the calculated enrichment factors and comparison indicate that the trace metals especially pb are enriched mainly due to the external anthropogenic activities in the land as well as in the coastal zone palk strait

hydrochemistry of groundwater gw and surface water sw for assessment of fluoride in chinnaeru river basin nalgonda district ap india hydrochemical studies were conducted in chinnaeru river basin of nalgonda district andhra pradesh india to explore the causes of high fluorides in groundwater and surface water causing a widespread incidence of fluorosis in local population the concentration of fluoride in groundwater ranges from 0 4 to 2 9 and 0 6 to 3 6 mg l stream water ranges from 0 9 to 3 5 and 1 4 to 3 2 mg l tank water ranges from 0 4 to 2 8 and 0 9 to 2 3 mg l for pre and post monsoon periods respectively the modified piper diagram reflects that the water belongs to ca2 mg2 hco3 to na hco3 facies negative chloroalkali indices in both the seasons prove that ion exchange between na and k in aquatic solution took place with ca2 and mg2 of host rock the interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water rock interaction is responsible for major ion chemistry of groundwater surface water high fluoride content in groundwater was attributed to continuous water rock interaction during the process of percolation with fluorite bearing country rocks under arid low precipitation and high evaporation conditions the low calcium content in rocks and soils and the presence of high levels of sodium bicarbonate are important factors favouring high levels of fluoride in waters the basement rocks provide abundant mineral sources of fluoride in the form of amphibole biotite fluorite mica and apatite

the partitioning of transitional metals fe mn ni cr in mangrove sediments downstream of a ferralitized ultramafic watershed new caledonia abstract in new caledonia one third of the island is composed of ultramafic rocks and lateritic soils enriched in fe ni and cr open cast mining occurs all around the island and processes of erosion and sedimentation which occur naturally along the coastline are strongly amplified by mining activities due to their position at the interface between land and sea mangroves receive extensive amounts of particles emanating from rivers through estuaries the purpose of this study is to understand the distribution and partitioning of some transitional metals fe mn ni cr in sediments and pore waters in a mangrove swamp which is situated downstream of a catchment characterized by lateritic soils that were exploited a century ago quantitative analyses on bulk and after selective extraction were carried out on cores collected along a transect within the intertidal zone i e beneath a rhizophora stylosa stand an avicennia marina stand and within a salt flat mean metal concentrations were mol g 1 fe 1997 ni 44 2 cr 31 9 mn 8 8 thus ni cr and fe concentrations in this study are substantially higher than mangrove world average in addition ni concentrations are 10 to 100 times higher than in other new caledonian mangrove developing downstream of a catchment not composed of ultramafic rocks the studied mangrove is characterized by gradients of water and organic contents with depth and along the intertidal zone which induced different redox conditions and thus different metals partitioning transitional metals are deposited in the mangrove mainly as oxides and or oxy hydroxides that are subsequently dissolved by bacteria for the decomposition of organic matter and which leads to a strong increase of metals in the dissolved phase then dissolved metals were precipitated with organic and sulfide compounds to conclude organic diagenesis in mangrove sediments leads to the transfer of transitional metals from oxide form to organic and sulfide forms

upper crustal basement involved folding in the east range of the sudbury basin ontario inferred from paleomagnetic data and spatial analysis of mafic dykes tilting of crystalline basement rocks associated with folding strain at uppermost crustal levels is difficult to recognize if basement rocks are devoid of traceable marker planes here we use the spatial variation in strike of paleoproterozoic mafic dyke segments complemented by compiled paleomagnetic data to identify tilting in archean basement rocks associated with kilometre scale folds of the eastern sudbury basin ontario spatial analysis of the strike of dyke segments is consistent with generation of the ne lobe and a newly identified anticline referred to as the west bay anticline in the layered sudbury igneous complex sic this anticline accounts better for the structural characteristics of the eastern sudbury basin than a previously proposed anticline with west plunging hinge line the west bay anticline is characterized by abrupt plan view thickness variations in the lower sic and curved faults displaying significant strike separations of sic contacts these structural characteristics are co

relationships between environmental conditions and the diagenetic evolution of organic matter derived from higher plants in a modern mangrove swamp system guadeloupe french west indies abstract the sedimentary organic matter content of a series of 2 m deep cores was investigated along a sea land transect at five sites representing five species of mangrove and salt marsh vegetation the vegetation was settled at the same place for at least 1000 years and therefore sedimentary organic matter deriving from the decay of higher plants has accumulated in large amounts the global morphological and chemical preservation of the organic matter attested by various sedimentary parameters including the proportions of cellulose bearing tissues the toc contents the c n ratios the total sulphur contents and the 13 c compositions reveals that the sedimentary organic matter is less degraded when it has been under the influence of the marine water table for a long time this is indicated by a good correlation between the salinities of interstitial waters the redox potentials measured in the wet sediments and the chemical composition of the organic matter moreover the concentration of organic sulphur shows a positive correlation with the hydrogen index hi only under the marine water table influence suggesting the very local presence of sulphur hc compounds

variations in flow and transport in thick desert vadose zones in response to paleoclimatic forcing 0 90 kyr field measurements modeling and uncertainties 1 an understanding of unsaturated flow and potential recharge in interdrainage semiarid and arid regions is critical for quantification of water resources and contaminant transport we evaluated system response to paleoclimatic forcing using water potential and cl profiles and modeling of nonisothermal liquid and vapor flow and cl transport at semiarid high plains texas and arid chihuahuan desert texas amargosa desert nevada sites infiltration in response to current climatic forcing is restricted to the shallow 0 3 3 m subsurface subsurface cl accumulations correspond to time periods of 9 90 kyr bulge shaped cl profiles generally represent accumulation during the holocene 9 16 kyr lower cl concentrations at depth reflect higher water fluxes 0 04 8 4 mm yr during the pleistocene and earlier times low water potentials and upward gradients indicate current drying conditions nonisothermal liquid and vapor flow simulations indicate that upward flow for at least 1 2 kyr in the high plains and for 12 16 kyr at the chihuahuan and amargosa desert sites is required to reproduce measured upward water potential gradients and that recharge is negligible 0 1 mm yr in these interdrainage areas index terms 1809 hydrology desertification 1815 hydrology erosion and sedimentation 1833 hydrology hydroclimatology keywords paleoclimate chloride mass balance unsaturated zone unsaturated flow modeling

semiarid unsaturated zone chloride profiles archives of past land use change impacts on water resources in the southern high plains united states 1 unsaturated zone chloride profiles in semiarid regions provide a decadal to century scale record of past environmental changes similar to climate change records provided by tree rings and ice cores impacts of conversions from natural ecosystems to rain fed agriculture on water resources are recorded in chloride profiles in semiarid regions as typified by the southern high plains shp texas southwestern united states large chloride accumulations beneath natural grassland and shrubland ecosystems 3 profiles reflect evapotranspirative enrichment of atmospherically derived chloride during the holocene indicating no recharge in interdrainage areas conversion to rain fed agriculture is recorded by downward displacement 9 profiles or complete flushing 10 profiles of chloride bulges indicating increased recharge increased recharge associated with cultivation median 24 mm yr 5 of precipitation 19 profiles was quantified using chloride mass balance calculations the timing of land use change was estimated using chloride data and results 43 89 years are consistent with aerial photo records and landowner surveys new equilibrium volumetric recharge rates beneath rain fed agriculture in the shp 0 63 km3 yr will require decades to establish and represent one to eight times recharge rates for baseline precultivated conditions that are focused beneath ephemeral lake or playa drainages 0 08 0 83 km3 yr these chloride profiles generally represent decadal scale monitoring of subsurface response to land use change

material exchange between the continental shelf and mangrove fringed coasts with special reference to the amazon guianas coast abstract mangrove fringed coasts are a major coastal environment in the tropics that exchange enormous quantities of inorganic and organic materials and dissolved ions with the adjacent ocean in unique ways the 1 600 km long guiana coast from the amazon river mouth to the orinoco the world s most extensive example is exposed to significant oceanic wave and tidal energy but is almost exclusively composed of mud deposits the huge alluvial discharge of the amazon advected along the inner continental shelf is reworked into 20 25 shore attached and mobile mud banks 10 40 km in length frequent and deep resuspension created by the energetic conditions results in fluid mud suspensions 10 400 g 1 1 that dewater upon re deposition resulting in extreme shoreline progradation rates up to hundreds of metres per year that are equally rapidly mobilized by wave attack biological assemblages mangroves foraminifera diatoms etc and biogeochemical conditions are strongly controlled by the intense recycling of sediments on the shoreface differences in sedimentary ecological and biogeochemical processes are striking when this coast is compared with mangrove fringed deltaic and estuarine coasts elsewhere including those of west africa and southeast asia

fault slip inversions their importance in terms of strain heterogeneity and kinematics of brittle deformation abstract heterogeneous deformation is intrinsic in natural deformation but often underestimated in the analysis and interpretation of mesoscopic brittle shear faults based on the analysis of 11 222 faults from two distinct tectonic settings the central andes in argentina and the sudbury area in canada interpolation of principal strain directions and scaled analogue modelling we revisit controversial issues of fault slip inversions collectively adhering to heterogeneous deformation these issues include the significance of inversion solutions in terms of 1 strain or paleo stress 2 displacement notably plate convergence 3 local versus far field deformation 4 strain perturbations and 5 spacing between stations of fault slip data acquisition furthermore we highlight the value of inversions for identifying the kinematics of master fault zones in the absence of displaced geological markers a key result of our assessment is that fault slip inversions relate to local strain not paleo stress and thus can aid in inferring the kinematics of master faults moreover strain perturbations caused by mechanical anomalies of the deforming upper crust significantly influence local principal strain directions thus differently oriented principal strain axes inferred from fault slip inversions in a given region may not point to regional deformation caused by successive and distinct deformation regimes this outcome calls into question the common practice of separating heterogeneous fault slip data sets into apparently homogeneous subsets finally the fact that displacement vectors and principal strains are rarely co linear defies the use of brittle fault data as proxy for estimating directions of plate scale motions

the composition of sedimentary organic matter in relation to the dynamic features of a mangrove fringed coast in french guiana the sedimentary organic matter content of a series of 2 m deep cores was examined in relation to the evolution of mangrove forest on the basis of geochemical analyses and optical observations avicennia dominated forest deposits developing along the highly dynamic coastline of french guiana were collected in five stations based on stage of forest evolution the sedimentary organic matter in the upper sediment of the youngest mangrove swamp is mainly derived from algal mats with low carbon nitrogen ratios c n ratio from 6 to 8 and typical greyish amorphous organic flakes as observed in optical studies indeed rare young avicennia trees are present and effectively geochemical parameters do not give evidence of a litter made up of higher plant debris these rare debris being probably exported by the tides a slight increase with depth in the first decimetres of both total organic carbon toc content and c n ratio results from the development of the radial cable root system of the pioneer avicennia germinans early diagenetic conditions of this young forest are rather controlled by dominant suboxic processes as suggested by high eh values range 200 400 mv and local anoxic processes occurrence of pyrite in micro environments this is mainly due to the oxygen available by roots and crab bioturbation the organic content of the senescent mangrove sediment is mainly derived from higher plant debris in the uppermost 30 cm as indicated by relatively high c n ratios and the predominance of ligno cellulosic debris the strong decrease in hydrogen index values results from the degradation of the higher plant debris losing hydrogen bounds through decay processes moderately acidic ph values low ehs and the presence of pyrite framboids point towards the reducing decay processes in surficial layers of the senescent mangrove mediated by sulphate reducing bacteria whatever the stage of evolution of the forest the geochemical characteristics of the sediment below 30 cm are those of the shoreface one with opaque refractory debris derived from the amazon river detritus discharge the sediment collected from dead mangrove forests subsequently recolonized by pioneer mangroves contains organic markers which predate recolonization recording previous phases of erosion and accretion

a geochemical study of the impact of irrigation and aquifer lithology on groundwater in the upper yakima river basin washington usa the yakima river a major tributary of the columbia river is currently overallocated in its surface water usage in part because of large agricultural water use as a result groundwater availability and surface water groundwater interactions have become an important issue in this area in several sub basins the yakima river water is diverted and applied liberally to fields in the summer creating artificial recharge of shallow groundwater major ion trace element and stable isotope geochemistry of samples from 26 groundwater wells from a transect across the yakima river and 24 surface waters in the kittitas sub basin were used to delineate waters with similar geochemical signatures and to identify surface water influence on groundwater major ion chemistry and stable isotope signatures combined with principal component analysis revealed four major hydrochemical groups one of these groups collected from shallow wells within the sedimentary basin fill displays temporal variations in no3 and so4 along with high 18o and d values indicating significant contribution from yakima river and or irrigation water two other major hydrochemical groups reflect interaction with the main aquifer lithologies in the basin the columbia river basalts high na groundwaters and the volcaniclastic rocks of the ellensburg formation ca mg hco3 type waters the fourth major group has interacted with the volcaniclastic rocks and is influenced to a lesser degree by surface waters the geochemical groupings constrain a conceptual model for groundwater flow that includes movement of water between underlying columbia river basalt and deeper sedimentary basin fill and seasonal input of irrigation water

tracing of anthropogenic zinc sources in coastal environments using stable isotope composition abstract the use of zinc isotopes to trace anthropogenic sources in coastal areas has been tested in this study we determined the stable isotopic composition of zinc in sediment cores suspended particulate matter spm and rocks collected at the sepetiba bay southeastern brazil an estuarine lagoon heavily impacted by metallurgic activities these isotopic signatures were compared with those from willemite ore which represent the main mineral refined by the major industrial source of zinc the aim was to test if this tracer system enables to identify sources and sinks of anthropogenic zinc and to reconstruct the temporal and spatial evolution of zinc contamination the zinc isotopic compositions expressed using the 66zn notation relative to the jmc 3 0749 l solution showed significant variations in the sediment cores the spm and willemite ore minerals ranging between 0 01 and 1 15 spatial and temporal analysis of sediments samples fit well in a model of mixing involving three main end members i terrestrial background 66znjmc 0 28 0 12 2 ii marine detrital material 66znjmc 0 45 0 03 2 and iii a major anthropogenic source associated with electroplating wastes released into the bay 66znjmc 0 86 0 15 2 sediment cores collected in the mud flats showed high correlation between 66zn and zinc enrichment factors suggesting good preservation of the isotopic records of natural and anthropogenic sources the sediment core sampled from a mangrove wetland located in a zone impacted by the metallurgy presented levels of zinc up to 4 sediment dry weight and preserved the isotopic signatures of electroplating wastes despite evidences that post depositional processes slightly changed the isotopic signatures in some layers from this core toward heavier 66znjmc values above 1 0 a two component mixing model suggests contributions of this major anthropogenic zn source up to nearly 80 during periods of electroplating activities our work suggests that zn isotope compositions of sediments are reliable tracers of anthropogenic sources and therefore can be useful to improve environmental monitoring efforts in coastal systems

microfacies characteristics of a tropical mangrove fringed shoreline cleveland bay queensland australia sedimentary and taphonomic controls on mangrove facies development mangrove ecosystems strongly influence the sedimentology and geomorphology of contemporary intertidal environments and are known to have occupied similar ecological niches at least as far back as the early cenozoic given this it is remarkable how few records of mangrove occurrence have been reported in the geologic record here a microfacies approach is adopted to examine the characteristics of a contemporary mangrove colonized intertidal succession along an active prograding shoreline in north queensland australia and compared with a proximal mid late holocene preserved intertidal succession this enables a comparison of microfacies development and preservation potential in like for like depositional environments over short temporal and spatial scales in the contemporary intertidal system active shoreline progradation has produced a highly gradational shallowing upward succession mid to low intertidal substrates characterized by an abundant and diverse bioclast especially molluscan fauna and a rich calcareous foraminiferal assemblage are overlain by organic rich upper intertidal mangrove facies characterized by abundant organic material especially wood and bark fragments and a distinct fauna of agglutinated foraminifera the major sedimentary effects of mangrove progradation are to introduce substantial amounts of organic matter into the substrate effectively overprinting the mudflat facies to mix and re texture due to root network development and infaunal bioturbation the sediment substrate and to modify the depth ranges over which infaunal molluscs and foraminifera occur variations in the relative abundance of constituents permit however the clear delineation of mangrove and intertidal mudflat facies whilst an essentially similar facies succession is identifiable in the sub recent many of the diagnostic facies constituents are either not preserved or are present in far lower abundances than in the modern in particular the inferred mangrove units contain far less organic material most wood and root material is absent are essentially devoid of bioclastic material and contain a depauperate agglutinated foraminiferal fauna the primary drivers of this are 1 loss of calcareous foraminifera and bioclasts due to carbonate dissolution 2 loss of agglutinated foraminifera due primarily to biological fiddler crab test degradation and mineralization of their organic binding agents and 3 aerobic and anaerobic degradation of organic material consequently actual criteria for identifying the presence of a former mangrove in this succession are limited such poor preservation even within sub recent mangrove deposits suggest that the longer term preservation potential of key diagnostic criteria is likely to be extremely poor within similar terrigenoclastic dominated organically enriched successions thus whilst mangroves significantly modify and re texture intertidal substrates use may often need to be made of sparsely preserved faunal or floral remains or traces interpreted in the context of the broader intertidal depositional succession to infer the presence of mangrove colonized substrates in the rock record

the dynamics of estuarine manganese cycling seasonal observations of dissolved managnese in the tamar estuary south west england have demonstrated pronounced temporal and spatial variability in the distribution of this component simultaneous observations of physical and physico chemical properties of the estuarine system together with kinetic measurements of dissolved managenese behaviour in isolated samples have demonstrated that the observed distributions are the instantaneous product of dynamic interactions involving external sources and internal input and removal processes dissolved manganese is mobilized internally from reduced sedimentsduring advective resuspension of bed material so that this input is regulated by temporal and spatial variations in tidal stress manganese is returned to the sediments by continuous uptake on to suspended particles the rate of this process is responsive to changes in suspended particulate load ionic strength ph and temperature the reaction changes from zero order kinetics in freshwater to first order kinetics characteristic of the saline medium with marked deceleration in effective removal rate following small increases in salt concentration relative changes in the first order removal rate throughout the estuary are consistent but there are considerable temporal variations in the absolute rates this is partially attributable to variations in the quality as well as the quantity of the suspended particles these results indicate that changes in the relative effectiveness of both the input and removal mechanisms which lead to internal cycling of manganese and to variable distributions of dissolved managanese within the estuary are closely coupled to the internal behaviour of particles and hence to the tidally induced oscillations in bed stress this observation has been confirmed by sequential recordings of dissolved manganese distributions through a spring tide to neap tide period furthermore climatic events producing enhanced disturbance of bed sediment have been shown to induce a similar sequence of events to that arising from tidally induced net mobilization of bed material

half a century of dynamic coastal change affecting mangrove shorelines of french guiana a case study based on remote sensing data analyses and field surveys the mobile mud banks several kilometres wide and about 30 km long which form the sedimentary environment of the coast of the guianas are a consequence of the huge particulate discharge of the amazon these mud banks shift towards the northwest influenced by the combined action of accretion and erosion a process also affected by periodic variability because of this movement the coastline is unstable and continuously changing such changes determine the structure and composition of mangrove forests the only type of vegetation adapted to this dynamic environment the objectives of this study were to identify coastal changes that took place over the last 50 years and to relate them to natural processes of turnover and replenishment of mangrove forests these objectives have been achieved through a combination of remote sensing techniques aerial photographs and spot satellite images and field surveys in the area of the sinnamary estuary french guiana ground data were collected in representative mangrove forest stands chosen as a function of their growth stages and their structural features from pioneer and young stages to adult mixed and declining formations the coastline changes and the mangrove dynamics over the 1951 1999 period are analyzed through production of synthetic digital maps showing an alternation of net accretion 1951 1966 and erosion periods 1966 1991 followed by the present accretion phase based on this structural functional and historic information a global scenario of mangrove forest dynamics is proposed including a model of forest development forest gap processes and sedimentological dynamics the results of this research are discussed within the context of regional coastal amazonian area and global climate d 2004 elsevier b v all rights reserved

the geometrical relationship between the stretching lineation and the movement direction of shear zones abstract the geometrical relationship between foliations and lineations in shear zones is considered quantitatively assuming that the internal structures of shear zones have monoclinic symmetry the common practice of directly correlating the pitch or plunge of the stretching lineation with the obliquity of the shear direction is challenged it is the orthogonal projection of the stretching lineation on the shear zone boundary that is parallel to the shear direction a shear zone is parallel to a plane containing both the pole to the symmetry plane and the strike of the shear zone and the shear direction is parallel to the intersection of the symmetry plane and the shear zone boundary the symmetry plane is determined by the stretching lineation and the poles to the s foliation the implications of this study for the interpretation of shear zones are discussed with reference to an actual example

soil organic carbon of mangrove forests rhizophora and avicennia of the venezuelan caribbean coast abstract in order to understand the processes that control organic matter preservation in tropical wetlands we have evaluated the mineralogy total organic carbon toc wt soluble organic matter som wt bulk density g cm3 and carbon stock mg ha and used ftir to identify functional groups in som of soil in mangrove forest dominated by rhizophora or avicennia with different conditions live deteriorated and dead six locations along the cuare inlet and morrocoy national park were studied mineralogical analysis showed the presence of minerals such as pyrite and rhodochrosite from anoxic environments rhizophora mangrove soils have higher toc compared with avicennia but we did not find significant differences in som toc som ratios were lower for avicennia soils the carbon content ranged from 11 30 to 59 84 mg ha for the first 10 cm of soil regardless of stand condition the toc som ratio was lower at a depth of 20 40 cm the results of the toc som ratio are attributable to a the association of toc with clays and non crystalline minerals b the leaching processes of soluble compounds of the om c a higher proportion of recalcitrant compounds d a lower decomposition rate for recalcitrant or non recalcitrant compounds and e physicochemical conditions that limit biological activity such as high salinity soil anoxia and hypoxia the soils can be divided into three groups according to the presence and intensity of functional groups detected by ftir the functional groups identified could not be related to the sampling sites to species composition or conditions these differences may be due to other sources of organic matter as well as to degree of preservation information of soil organic matter properties and their relationship with mangrove composition and conditions is important to understand carbon sequestration and storage potential in venezuelan caribbean mangrove systems

brachyuran crab community structure and associated sediment reworking activities in pioneer and young mangroves of french guiana south america this study in french guiana evaluates the changes of crab assemblages and their bioturbation activities between mangrove early stages pioneer and young mangrove and within stages by taking their spatial heterogeneity tidal channels flat areas pools into account the results show differences in crab assemblage structure between and within the early stages of mangrove in relation to microhabitat and sediment characteristics the sediment reworking rates are a function of the biomass or density of particular species ucides cordatus uca cumulanta and burrower functional groups crab species or functional interactions mediate changes in sediment reworking rates suggesting the need to consider entire benthic communities rather than single species this study suggests that the role of the micro habitat in determining the biologically induced sediment reworking rates depends on the age of the mangrove feeding activity results in a sediment turnover of 11 7 9 7 g dw m 2 day 1 and 6 8 3 0 g dw m 2 day 1 in the pioneer and young mangroves respectively burrow maintenance excavates 40 5 7 4 g dw m 2 day 1 and 251 3 419 7 g dw m 2 day 1 in the pioneer and young mangroves respectively upscaling to the studied area sinnamary estuary 6 km 2 shows that 500 tons day 1 and 20 tons day 1 of sediments could be excavated and pelletized respectively during the spring tides of the dry season thus biological sediment reworking would greatly contribute to the sedimentary dynamics of the guianese mangroves under amazonian influence c 2016 elsevier ltd all rights reserved

origin and diagenesis of lignin and carbohydrates in mangrove sediments of guadeloupe french west indies evidence for a two step evolution of organic deposits the mangroves of grande terre island guadeloupe french west indies are known to store large amounts of organic carbon and organic rich sediments have been described to several meters depth the purpose of the present work was to precisely determine the molecular composition carbohydrates and lignin derived phenols of these organic deposits in relationship with environmental conditions it was found that within the upper meter of the cores geochemical data displayed the classical degradation pattern of organic matter om deriving from higher plants on the one hand carbohydrates from mangrove tissues underwent fast decomposition other compounds being simultaneously synthesized by bacteria on the other hand lignin phenols were lost rather slowly i e at a similar or lower rate than toc their distribution with depth evidencing various lignin decomposition pathways depending on redox conditions the position of the swamp with respect to salt and fresh water tables strongly influenced these conditions at depth results revealed an organic rich layer which was characterized by surprisingly well preserved om with regard to sugar and phenol compositions we speculate that the preservation of these compounds might be explained by a rapid and permanent flooding of the mangrove stands that may have occurred more than a thousand years ago we suggest that the geodynamic context i e the recurrent seismic activity recorded in guadeloupe may have induced such a flooding resulting in the preservation of this om

coupling between sedimentary dynamics early diagenetic processes and biogeochemical cycling in the amazon guianas mobile mud belt coastal french guiana coastal french guiana lies within the vast mobile mudbelt that characterizes much of the s american inner shelf downdrift of the amazon river approximately 15 20 of the amazon sediment outfall moves nw along the guianas in part as a series of 20 25 coastal mud waves seasonal studies of a representative migrating mudwave located between kourou and sinnamary french guiana demonstrate that diagenetic properties and biogeochemical cycling are closely coupled to sedimentary dynamics and the refluxing of reduced components between the seabed coastal facies and well oxygenated overlying water an unsteady two zone diagenetic regime is typically present in the shallow subtidal and low intertidal regions a surficial layer usually 0 5 1 m thick is nonsulfidic highly reactive and dominated by fe mn cycling this suboxic layer unconformably overlies more consolidated sediment in which net so42 reduction is often observed and contracts shoreward toward the mangrove fringe as sediments stabilize and become bioturbated the relatively stable intertidal flats are also sites of significant benthic primary production despite suboxic conditions over extensive intervals anaerobic remineralization rates are high co2 0 2 0 6 mm day 1 and often show little evidence of attenuation with depth integrated co2 fluxes are 20 235 mmol m 2 day 1 wet dry season average 120 far exceeding diffusive o2 fluxes into the bottom high reactivity 0 08 day 1 and low c n remineralization release ratios 5 3 of decomposing material imply fresh substrate of marine origin most reduced solid phase fe is present as nonpyritic authigenic fe minerals 20 fe ii is in pyrite and low sedimentary c s ratios 6 8 reflect the generally nonsulfidic conditions a broad range of tracers e g 234th t1 2 24 days 210pb t1 2 22 years seasonal cl profiles and nonsteady state diagenetic models of pore water concentrations and oxidant reductant relationships demonstrate that the upper 0 1 1 m of deposits are reworked and exchanged with overlying water on timescales of 10 days to seasonally thus the seafloor acts as a massive suboxic batch reactor entraining and processing reactive marine plankton regenerating fe mn oxides exchanging metabolites and nutrients with the oxygenated water column and generating suites of nonsulfidic authigenic minerals the apparent paradoxical properties of high remineralization rate low reductant content corg 630 mol g 1 and dominance of suboxic metal cycling are a direct consequence of frequent entrainment of highly reactive organic substrate and simultaneous regeneration of the major fe oxidants in oxygenated water the amazon guianas mobile mudbelt is a zone of extraordinarily intense sedimentary and biogeochemical recycling greatly exceeding stable coastal systems such as salt marshes in material exchange with the sea

organic carbon sources and transformations in mangrove sediments a rock eval pyrolysis approach abstract a rock eval pyrolysis study was carried out on sedimentary cores and leaf and woody tissue of vascular plant species from the mangroves of french guiana these forests develop on moving mudbanks and have a lifetime limited to few decades before being eroded our main purpose was to complete the understanding of carbon cycling in this specific environment using a method that allows monitoring the depth evolution of sources and transformation of organic matter om within a tight depth span leaf and woody tissue showed clearly distinct rock eval parameters however these parameters strongly varied with om decomposition rapidly limiting their efficiency as mangrove plant tracers the decrease in values of tps2 pyrolysis temperature corresponding to the maximum release of hydrocarbons with depth clearly showed a line between a pedogenetic layer enriched in autochthonous om and marine sediments enriched in allochthonous om this allochthonous om originated from the particulate discharge of the amazon river which is partly deflected northwestwards by the current of the guianas within the soil layer decay processes induced a strong dehydrogenation and slight oxidation of om the two processes occurring simultaneously the deeper layers were characterized by a very strong increase in oico2 quantity of pyrolysed co2 relative to total organic carbon beneath both the young and the senescent forests this trend resulted rather from an increasing content of authigenic carbonate than from increasing concentration of oxidized allochthonous debris carbonate can form as a result of the more anoxic conditions prevailing in buried layers vs the upper suboxic ones beneath the senescent mangrove a greater increase in oico2 probably reflected greater carbonate precipitation resulting from the decomposition of higher amounts of om

hydrogeochemical characterization and quality assessment of groundwater around umrer coal mine area nagpur district maharashtra india quality assessment as well as hydrogeochemical characterization of 45 representative groundwater samples around umrer coal mine area was undertaken the ph of the water lies in the normal range i e from 7 5 to 8 5 the electrical conductivity varies from 826 to 1 741 the total hardness varies from 289 to 1 302 and the tds values range from 528 6 to 1 114 2 mg l which reflects variation in lithology and thus the distinction in hydrogeological regime the cation chemistry is dominated by ca2 and mg2 while anion chemistry is dominated by cl and hco3 out of total ten hydrochemical facies the two dominant facies are mg ca hco3 37 7 and ca mg so4 hco3 17 7 the groundwater in the study area in general is useful for drinking and domestic use however it has marginal utility for irrigation purpose standard us salinity laboratory classification shows that water of the study area belongs to c2 s1 and c3 s1 classes the concentration of 9 trace elements analysed from 18 samples did not exceed the desirable limit

behavior of redox sensitive elements during weathering of granite in subtropical area using x ray absorption fine structure spectroscopy abstract the variation in chemical compositions of regolith along a weathering profile developed on a granite substrate in jiangxi province in southern china was investigated in this paper with the aim to characterize the speciation of redox sensitive elements and to evaluate their mobility and redistribution during chemical weathering mass balance calculations indicate titanium ti is the most immobile element in this weathering profile a new method x ray absorption fine structure xafs spectroscopy was used to determine the speciation of fe and mn along the profile fe k edge x ray absorption near edge structure xanes spectra show fe in saprolith is stabilized mainly in the state of fe iii suggesting fe is as immobile as conservative elements during granite weathering mn k edge xanes spectra show mn iii iv oxides are reduced to mn ii in surface soil where soil organic matter som acts as an important reductant although ce co and v were unable to be analysed by xafs their concentrations have significant correlations with that of mn indicating that the mobilization and redistribution of ce co and v may also be governed by redox condition all in all the results suggest that redox process impacts significantly on the redistribution of mn ce co and v along the profile the successful application of xafs in the study on migration of redox sensitive elements during granite chemical weathering has provided valuable information for the understanding and evaluating the geochemical behavior of elements in the environment

pyritization of trace metals in anoxic marine sediments the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as h2s reactive fe pyrite content and salinity in controlling this process the areas studied included anoxic sulfidic sediments baffin bay a hypersaline coastal lagoon from texas and green canyon a hemipelagic oil seepage area anoxic nonsulfidic sediments with high sedimentation rates atchafalaya bay mississippi delta system hemipelagic anoxic nonsulfidic sediments with low sedimentation rates gulf of mexico shelf and slope and orca basin an euxinic hypersaline basin and organic rich marsh sediments atchafalaya bay results indicate that the degree of trace metal pyritization dtmp of all trace metals except cd increased with increasing degree of pyritization dop irrespective of the type of sedimentary environment involved however for as hg and mo the dtmpdop values were generally above the 1 1 ratio line whereas the transition metals co cu mn and ni displayed a close to linear increase in dtmp with dop and moderate incorporation into pyrite chromium and the class b metals pb and zn were also gradually incorporated into the pyrite phase but without reaching the dtmp levels exhibited by the transition metals cadmium was not incorporated to a significant extent these results are consistent with the chemical attributes of these different classes of trace elements availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of co cr cu and ni into pyrite in anoxicsulfidic fe poor and h2s rich environments

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

redox stratification and heavy metal partitioning in avicennia dominated mangrove sediments a geochemical model abstract mangrove forest sediments can provide a sink for trace metals because the mangroves create a baffle that promotes the accumulation of fine grained organic matter rich sediment which is usually sulphidic due to the presence of sulphate reducing bacteria direct adsorption complexing with organic matter and the formation of insoluble sulphides all contribute to the trapping of metals the concentration and chemical speciation of the metals are influenced by the distribution of geochemically distinct horizons within the sediment in horizons with a ph 7 and an eh 100 mv oxidation horizons most metals are present as exchangeable or oxide bound species in most cores two oxidation and two reduction horizons can be recognised but dark mottles of low eh 100 mv sediment can be found around mangrove roots and burrows in the reduction horizons the depth to each horizon differs between cores and can change in response to seasonal shifts in the position of the water table a model is presented that accounts for the development of the oxidation and reduction horizons within the avicennia dominated mangrove forest sediment and describes the major controls on metal cycling within the sediment

photoelastic and numerical investigation of stress distributions around fault models under biaxial compressive loading conditions abstract this paper presents the results of a photoelastic and numerical study of stress distributions contours and trajectories around fault models of various geometries submitted to a biaxial compressive load it aims to describe typical biaxial stress behaviours and emphasize the existing differences with the well known uniaxial compressive load case stress trajectories are sometimes shown by joint sets acting as markers of a paleostress field and they can be interpreted by particular shallow tension compression situations at depth fractures can be reactivated or can dilate under conditions of triaxial compression and behaviour is essentially controlled by a high stress ratio high 3 1 ratio in spite of the potential importance of such stress states on fracture permeability and fluid flow and although they are frequently found at depth in a reservoir context such stress conditions are poorly investigated particularly in terms of stress perturbations the presented analogue experiments consisted of compression tests done on polymethylmethacrylate pmma plates this material has mechanical properties comparable to those of brittle rocks in the upper crust and presents birefringence the samples contained open defects acting as faults and the stress trajectories around these faults were investigated using a photoelastic device comparable numerical experiments were realised with a finite element code franc 2d using frictionless fault models first the effect of an increasing biaxial compressive load ratio 3 1 on stress trajectories around an isolated open defect was explored it was shown that the stress trajectories were drastically modified when 3 1 increased from 0 2 to 0 4 this result being consistent with previous studies in particular when 3 1 was superior or equal to 0 4 external isotropic points around where trajectories diverged called repulsive isotropic points appeared near the tips but away from the defects they tended to move away from the defects towards the main load direction when 3 1 increased the described isotropic points were points of stress trajectory divergence i e points where stress decreased implying that zones around them were strongly unfavourable to shear reactivation second stress trajectories around fault models of various geometries oblique isolated defect dilational jog compressive jog and complex patterns were studied the applied biaxial compressive load ratio being 0 7 these biaxial stress trajectories were compared with similar uniaxial stress trajectories in order to explore the existing differences between the two regimes it enabled new stress trajectory geometries to be described and interpreted in particular numerous external repulsive isotropic points were observed and defect tips were shown to be zones of high convergence of stress trajectories furthermore in contrast to the uniaxial compressive load case stress trajectories and stress contours were geometrically similar within dilational and compressive jogs under biaxial compressive load for both jog types the centre of the overlapping zone and the areas along the wall of a jog defining fault and facing the overlapping tip of the other fault proved to be zones of low mean stress implying that fluids may migrate towards them from the tips of the faults in response to mean stress gradients furthermore the centre of the jogs exhibiting a high differential stress was a favourable area in terms of fracture reactivation which may facilitate fluids transfer and storage it was also observed that for both the uniaxial and biaxial compressive loads isotropic zones were localised at the acute angle between branching defects

origin of amazon mudbanks along the northeastern coast of south america abstract seismic profiles sediment cores and water column measurements were collected along the northeastern coast of brazil to examine the origin of mudbanks in the amazon coastal mud belt these 10 60 km long shore attached features previously had been observed to migrate along the 1200 km coast of the guianas in response to wave forcing chirp 3 5 khz seismic profiles of the shoreface and inner shelf located two mudbanks updrift of the previous eastern limit in french guiana 210 pb geochronology shows that these two banks are migrating to the northwest over a relict mud surface in 5 20 m water depth the mudbanks are 3 4 m thick and are translating over a modern shoreface mud wedge deposited by previous mudbank passage in

the effect of seasonal rainfall on nutrient input and biological productivity in the yax chen cave system ox bel ha mexico and implications for μxrf core studies of paleohydrology abstract lakes and speleothems from mexico s yucatan peninsula have been used extensively over the past decades for paleoclimate studies however aquifer condition and its response to climate change has received little attention cenotes sinkholes and coastal caves have been shown to record the paleohydrology of the aquifer but there is little information on sedimentation in these cave systems and its response to climate change newly developed xrf instrumentation for the analysis of cores can achieve subannual resolution due to small measurement increments but short period studies examining weathering inputs and rainfall have not yet been undertaken hindering paleoenvironmental interpretations of lake and cave sediment records this study examines the spatial and temporal relationship of cave sediment geochemistry in the anchialine cave system of yax chen quintana roo mexico sediment traps n 51 were placed at seventeen stations along the 2 7 km flooded cave system which transitions from mangrove to upland forest terrain with cenotes of variable size and frequency along its length sediment traps were collected every 6 months from may 2013 may 2017 along with rainfall and groundwater level data there are distinct responses of lithogenic fe ti sr limestone weathering and biogenic influenced si k s phytoplankton and mangrove sediment elements in the sediment samples associated with seasonal rainfall and hurricanes while lithogenic elements ti k show a direct relationship seasonal rainfall the sedimentation of biologically influenced si ti elements exhibit a 6 12 month lagged response with large rainfalls such as hurricane ingrid in 2013 and other tropical storms throughout the study period

coal petrographic genetic units in deltaic plain deposits of the campanian mesa verde group new mexico usa the campanian rocks of the mesa verde group in the san juan basin new mexico usa form a littoral wedge composed of offshore shoreface and onshore facies this siliciclastic wedge was interpreted as a landward to seaward stepping of grouped genetic units i e intermediate term cycles the continental facies consist of coastal plain deposits coals shales and sandstones represented by three main domains progressively distant from the palaeoshoreline the deltaic plain the intermediate plain and the alluvial plain domains in the deltaic plain grouped aggradational retrogradational genetic units consist of preserved coal shale doublets alternating with thick shales although previous works have identified genetic units in the shoreface facies the existence of the latter has not been proven in the coastal plain deposits as coal shale doublets may represent such genetic units an organic petrography study was performed at high resolution on an 80 cm thick 1 5 km long coal seam to demonstrate this hypothesis in this work the depositional environments of the initial peatlands were rebuilt utilizing two complementary methods maceral and microlithotype analyses the results reveal the existence of internal sequences in the coal seam corresponding to recurrent patterns of a palaeogeographical model proposed for a littoral domain the authors interpret this coal sequence as the record of successive progradational and aggradational events furthermore a previous study of the organic content of the shales located above the coal demonstrated that the preservation of these facies is related to higher accommodation peat production and accommodation sedimentary supply ratios coal shale doublets are then interpreted as elemental genetic units of the deltaic plain formation this study demonstrates that contrary to original concepts littoral coal seams are not just markers of stable shoreline conditions at a high time scale but also record landscape migration

understanding distribution and abundance of metals with space and time in estuarine mudflat sedimentary environment spatial and depth wise distribution of sediment components organic carbon and selected metals fe mn al ni cr co zn and pb is studied across upper and middle tidal flats from lower and middle estuarine regions of kundalika estuary central west coast of india silt and clay form the major components in lower and middle estuary respectively sand silt clay and organic carbon showed band type distribution along the estuary the sediment deposition over the years took place in varying hydrodynamic conditions in lower and middle estuarine regions upper flats of the lower estuary represent mud while middle flats of the lower estuary facilitated the deposition of sandy mud correlation results indicated the importance of clay and organic carbon in removal and trapping of metals at lower and middle estuary respectively factor analysis indicated that the distribution of metals is largely controlled by fe mn oxyhydroxides and organic carbon the middle flats of the lower estuary showed an anthropogenic source for ni cr and co while middle flats of the middle estuary showed a mainly lithogenic source

application of gis and hydrogeochemistry of groundwater pollution status of nagapattinam district of tamil nadu india this study evaluated groundwater quality of the coastal aquifer in nagapattinam district with intensive agricultural activities in the southern part of india chemical components such as ph ec tds major cations and anions were used to identify seawater intrusion fifty two groundwater samples were collected from dug and bore wells in this region during summer and monsoon seasons 2011 ec tds na and cl were higher in summer than in monsoon the correlation and two way joining cluster analyses clearly show that groundwater quality is mainly controlled by seawater intrusion and other anthropogenic sources modified hill piper exhibits that most of the samples belong to water contaminated with gypsum sector the interpretation of gibbs plot represents the groundwater samples that fall in evaporation and rock weathering zone and other samples are affiliated to various anthropogenic activities based on na sar chloride hardness and wilcox classification the groundwater is moderately suitable for agriculture this region is vulnerable to seawater intrusion during summer due to the severe pumping of groundwater in groundwater quality maps produced by inverse distance weighting of arcgis some good and medium patches could be used for agriculture to a certain extent the northern southern and central parts of the study area fell in poor quality regions because of seawater intrusion and infiltration of irrigation water contaminated with pesticides and fertilizers

solute exchange by convection within estuarine sediments the rates of material transport through sediments are central to determining the biochemical status of sediments transport within sediments can occur by molecular diffusion through porewaters and by the activities of burrowing biological organisms but a number of physical processes can enhance transport within porewaters here convection is investigated as a mechanism for solute transport within sediments convection will occur as the gravitational adjustment to the occurrence of porewater which is of lower salinity and density than the water at the sediment surface this process could be important for exchange between sediments and the water column in regions subject to significant temporal variations in salinity such as estuaries

relationships between organo mineral supply and early diagenesis in the lacustrine environment a study of surficial sediments from the lac du bouchet haute loire france the relationships between organo mineral composition and early diagenetic processes in surface 50 cm sediments from the lac du bouchet haute loire france are presented parallel pore water studies reveal downcore increases in dissolved organic carbon inorganic carbon and ch4 illustrating the dominant methanogenetic degradation but also highlighting regions of enhanced degradation due to sulphate reduction confirmed by solid phase sulphur and pyrite distributions three sedimentary facies are observed ia 0 25 cm where the majority of compaction and degradation of the organic matter by diagenesis occurs in the absence of any significant change in the type of organic material or sedimentation rate ib 25 40 cm characterised by an increased grain size and diatom abundance ii below 40 cm whose base dates at 2500 350 bp i e within the sub atlantic shows high organic carbon contents and large grain size autochthonous amorphous organic matter is the dominant petrographical organic component whereas pedogenetic allochthonous amorphous organic matter is slightly enriched in facies ii and ia this is coincident with the disappearance of the spores and pollen and suggests a greater continental runoff from the surrounding basin at these times proportions of kaolinite chlorite and illite content do not vary greatly indicating that the detrital input has not changed significantly over the last 2500 years downcore decreases in the sial curve proxy for biogenic silica parallel those of total organic carbon suggesting the dissolution of solid phase silica over time the anthropogenic deforestation and consequent greater nutrient runoff into the oligotrophic lake encouraged an increased production of diatoms around 30 cm the increased sedimentation rate at the beginning of the sub atlantic facies ii as a result of greater continental runoff due to installation of present climatic conditions enhanced the preservation of the organic material by reducing the dia genetic effects and by increasing the proportion of diagenetically inert and relatively resistant organic matter these findings underline the critical role that bulk sedimentation rate and the nature of organic matter play in the final determination of sediment composition both in terms of input and in post depositional degradation

intertidal substrate modification as a result of mangrove planting impacts of introduced mangrove species on sediment microfacies characteristics a programme of mangrove planting has been undertaken around the island of rodrigues sw indian ocean since the mid 1980 s involving the introduction of the species rhizophora mucronata we examined three coastal embayment sites baie diamant anse goeland and anse pansia in which planting has been undertaken over different time periods within the past 20 years planting has met with variable success in the different sites probably due to variations in fluvial and groundwater influence at two sites baie diamant first planted in 1990 and anse pansia first planted in 1995 ecological data indicates that the mangroves are becoming well established and sedimentary evidence suggests that relatively rapid modification of intertidal substrates has occurred this is evident in the form of significant increases in sediment organic matter content especially fibrous organic matter and an increase in the accumulation of sediment fines inside the mangroves a strong correlation exists between the magnitude and depth of substrate modification and mangrove forest density especially root and sapling density at the third site anse goeland first planted in 2001 mangrove establishment has not been successful many of the seedlings have died and no secondary colonisation has occurred sediment substrates show no deviation from background levels in terms of organic content or weight fines content and we find no evidence for mangrove planting influencing sediment substrates despite evidence for the development of a distinctive mangrove facies at baie diamant and anse pansia there is however no evidence as yet for a marked change in substrate geochemistry such as would be demonstrated by evidence of active bioclast dissolution a common process in many natural mature mangrove substrates we infer this to be a function of the present relative immaturity of the still developing mangrove substrates but may also be a function of the apparent paucity of burrowing crabs which play an important role in nutrient cycling and sediment geochemistry thus whilst the mangroves in some of the study sites are reaching a stage where they are producing distinctive sedimentary facies the systems appear to be in a state of progressive sedimentary and diagenetic modification as the floral and infaunal components of the mangroves continue to develop

factors controlling groundwater quality in eastern united arab emirates a chemical and isotopic approach abstract chlorine 36 along with oxygen and hydrogen isotopes and selected major ions were used to investigate the factors controlling groundwater quality in the eastern part of the united arab emirates two main aquifers occupy the study area the eastern gravel plain aquifer that occurs near the coastal area and the inland ophiolite aquifer previous studies suggest that groundwater particularly in the eastern gravel plain aquifer is affected by seawater intrusion and evaporation samples of groundwater from the eastern gravel plain aquifer cl 1000 mg l have r 36 cl values in the range of 13 3 17 4 10 15 while those from the ophiolite aquifer cl 36 cl values in the range of 20 118 10 15 these values indicate the presence of bomb produced 36 cl and are consistent with recent post 1950 recharge of most of the samples d 18 o relationship plots on a typical evaporation line which suggests potential evaporation of the recharging waters prior to infiltration the r 36 cl values of the coastally bound eastern gravel plain aquifer are lower than the ophiolite aquifer which suggests an additional input of chloride to this aquifer moreover in most cases the chloride concentration is not balanced by the concentrations of other cations such as sodium potassium calcium or magnesium seawater intrusion is thus ruled out measurements of bromide concentrations support the contention that organically bound cl is being released into this environment agricultural practices which are extensive in this region are a possible source also sodium and silica concentrations provide evidence for the release of these elements by the weathering of host rocks

hydrochemical assessment of pond and stream water near abandoned barite mine sites in parts of oban massif and mamfe embayment southeastern nigeria hydrochemical studies were carried out in parts of oban massif and mamfe embayment southeastern nigeria to examine the contributions of barite mining activities on water quality pond and stream water samples were collected from six abandoned barite mines and adjoining streams areas during dry and wet seasons these samples were analysed for physicochemical parameters using standard techniques the results showed that the quality of water samples in the vicinity of barite mine sites was characterized by low ph low mineralization high suspended solids and deep colour sodium na and calcium ca2 are the dominant cations and bicarbonate hco3 and sulphate so4 2 the dominant anions the low concentration of dissolved silica relatively high concentrations of na hco3 and so4 2 suggest a combined influence of silicate carbonate and weathering of mine spoils the total dissolved solids total suspended solids electrical conductivity and major ions except na and k are higher for water draining barite mines from cretaceous sediments while na k ba2 are higher in basement rock areas correlation and factor analyses suggest that the main components of the water samples are related to anthropogenic geogenic mineralization and environmental controls while gibbs diagram plots indicate weathering as the main process controlling the chemistry of water computed values of hardness and some irrigational parameters showed that the pond and stream water samples are generally soft and can be used for irrigation generally the water quality satisfied the who 2008 and nis 2007 standards for domestic agriculture and industrial however there is the need to assess the impact of the pollution on the ecosystem and human health while remediation measures are being considered

hydrogeochemistry and pollution assessment of quaternary tertiary aquifer in the liwa area united arab emirates this study presents the data on the hydrochemical characteristics and isotope chemistry of liwa aquifer which could be useful to clarify the hydrochemical facies and hydrogeological regime in the study area electric conductivity and total dissolved solid values show that the investigated water is slightly brackish due to the effect of evaporation and the occurrences of evaporite rocks in the adjacent sabkhas of abu dhabi major cations and anions arranged according to their decreasing concentrations are na ca 2 k mg 2 and cl hco3 so4 2 respectively as sodium is the dominate cation and chloride is the prevailing anion hydrochemically the groundwater of liwa can be classified as na cl rich predominantly chloridic ion concentrations increase towards the northeast and presumably coincide with the lithological sources of ions factors affecting the hydrochemistry of the groundwater of the investigated area include the effect of weathering of soil and rocks evaporation and agricultural activities stable isotopes of oxygen and hydrogen show that the shallow aquifers contain a single water type that originated in a distinct climatic regime this water type deviates from the local meteoric water line as well as from the eastern mediterranean meteoric water line suggesting potential evaporation of recharged water prior to infiltration the waters are poor in tritium and thus can be considered generally as indication for recharge prior to 1952 the degradation of groundwater quality can be attributed to evaporation and agricultural practices in most cases

exafs analysis of iron cycling in mangrove sediments downstream a lateritized ultramafic watershed vavouto bay new caledonia mangrove forests are the dominant intertidal ecosystem of tropical coastlines in new caledonia mangroves act as a buffer zone between massive fe lateritic deposits and a lagoon partly registered by unesco as a world heritage site the new caledonian mangroves are characterized by a botanical gradient composed of three main vegetal stands i e rhizophora spp avicennia marina and salt flat which relies on the duration of tidal immersion that imposes gradients of pore water salinity oxygenation and organic content in the sediment in the present study we have determined the distribution and speciation of fe in mangrove sediments along this botanical gradient by using x ray absorption spectroscopy xas at the fe k edge both xanes and exafs results show that iron speciation strongly follows the redox boundaries marking the intertidal and depth zonations fe bearing minerals eroded from lateritic outcrops mainly goethite a feooh and phyllosilicates serpentine and talc are the major fe hosts in the upward horizons these mineral species progressively disappear with increasing depth where pyrite fes2 forms in the hydromorphic rhizophora and avicennia zones sulfate reduction is not observed in the drier salt flat zone in addition to these reduction processes intense re oxidation of aqueous fe ii and pyrite leads to the formation of poorly ordered ferrihydrite lepidocrocite c feooh and likely goethite in the upper sediments beneath avicennia and rhizophora stands the relative proportion of the newly formed poorly ordered ferrihydrite and lepidocrocite is found to be higher in the rhizophora mangrove stand which is the closest to the shore tidal fluctuations may thus be a major cause for continuous fe reduction oxidation cycles in the vegetated mangrove stands which could significantly affect the iron mass balance in mangrove systems

chemical and isotopic methods for confirming the roles of wadis in regional groundwater recharge in a regional arid environment a case study in al ain uae in arid environments groundwater may represent the most important source of water for sustaining life the timing and nature of precipitation may induce infiltration and recharge on a small scale the al ain region uae was chosen and from 1996 to 1997 studies were conducted to illustrate spatial distribution of recharge for groundwater by using chemical and isotopic methods according to the field survey uae can be hydrogeologically classified into five parts mountain area wadis sand dunes inland sabkhas and coastal sabkhas respectively in this report we studied a typical wadi wadi mieshiq area upstream of the wadi it was found that the groundwaters were characterized by low salinity stable isotopes of groundwaters in the wadi were lighter than those of the stream waters in the mountain area since stream water was affected by evaporation before it infiltrated into the ground the isotopes of recharged water into the wadi must have isotopically light values from the results above groundwater along the wadi was mainly derived from not only water from the mountain area but also infiltrated water during the flood period wadis are an important recharge region for groundwater copyright 2001 john wiley sons ltd

geochemistry of iron and manganese in soils and sediments of a mangrove system island of pai matos cananeia sp brazil abstract five zones along a transect of 180 m were selected for study on the island of pai matos sao paulo brazil four of the zones are colonised by vascular plants spartina sp laguncularia lg avicennia av and rhizophora rh and were denominated soils and the other zone which lacks vegetation was denominated sediment sd the geochemical conditions differed significantly in soils and sediment and also at different depths the soils were oxic eh 350 mv or suboxic eh 350 100 mv at the surface and anoxic eh

mangrove sediment carbon stocks along an elevation gradient influence of the late holocene marine regression new caledonia abstract among blue carbon ecosystems mangroves are very efficient in storing carbon in their sediments over decadal to millennial time scales however this ability varies with numerous parameters including climate and sea level variations in new caledonia mangrove ecosystems develop in semi arid conditions with a typical zonation rhizophora spp colonize the seaward side of the intertidal area while avicennia marina develops at higher elevations just below the salt flat within this context we determined both the quantity organic carbon content and carbon stocks and the characteristics carbon over nitrogen ratios c n stable carbon and nitrogen isotopes radiocarbon age of the organic matter stored beneath each mangrove stands carbon stocks were determined down to different limits with depth approximate extension of the root systems one meter depth and the hard substrate within the extension of the root systems the sediment carbon stock was lower than 100 mgc ha 1 regardless of the mangrove species this low value resulted directly from the dry climate that limits mangrove productivity at depth beneath every zone a buried layer enriched in mangrove derived organic matter with c n values around 40 and 13c values around 26 was observed this layer likely resulted from a sea level high stand during the late holocene that allowed a long period of stability of the mangrove slowly accumulating organic matter within the sediment in this buried layer the carbon stock was higher than in the upper sediment and reached up to 665 255 and 300 mgc ha 1 in the salt flat zone the a marina stand and the r spp stand respectively the highest stock determined beneath the salt flat was suggested to be related to a period of sea level stability that lasted 3000 years whereas beneath the other zones which are at lower elevations mangrove colonization was more recent and the sea level was continuously decreasing till recently sea level variations and specifically current sea level rise may strongly influence mangrove development due to their migration along the tidal elevation gradient to maintain the biotic conditions needed for their development

ni cycling in mangrove sediments from new caledonia abstract covering more than 70 of tropical and subtropical coastlines mangrove intertidal forests are well known to accumulate potentially toxic trace metals in their sediments and thus are generally considered to play a protective role in marine and lagoon ecosystems however the chemical forms of these trace metals in mangrove sediments are still not well known even though their molecular level speciation controls their long term behavior here we report the vertical and lateral changes in the chemical forms of nickel which accumulates massively in mangrove sediments downstream from lateritized ultramafic deposits from new caledonia where one of nature s largest accumulations of nickel occurs to accomplish this we used ni k edge extended x ray absorption fine structure exafs spectroscopy data in combination with microscale chemical analyses using scanning electron microscopy coupled with energy dispersive x ray spectroscopy sem edxs after principal component and target transform analyses pca tt the exafs data of the mangrove sediments were reliably least squares fitted by linear combination of 3 components chosen from a large model compound spectral database including synthetic and natural ni bearing sulfides clay minerals oxyhydroxides and organic complexes our results show that in the inland salt flat ni is hosted in minerals inherited from the eroded lateritic materials i e ni poor serpentine 44 58 ni rich talc 20 31 and ni goethite 18 24 in contrast in the hydromorphic sediments beneath the vegetated avicennia and rhizophora stands a large fraction of ni is partly redistributed into a neoformed smectite pool 20 69 of ni montmorillonite and ni speciation significantly changes with depth in the sediment indeed ni rich talc 25 56 and ni goethite 15 23 disappear below 15 cm depth in the sediment and are replaced by ni sorbed pyrite 23 52 in redox active intermediate depth layers and by pyrite 34 55 in the deepest sediment layers ni incorporation in pyrite is especially observed beneath an inland avicennia stand where anoxic conditions are dominant in contrast beneath a rhizophora stand closer to the ocean where the redox cycle is intensified due to the tide cycle partial re oxidation of ni bearing pyrites favors nickel mobility as confirmed by ni mass balance estimates and by higher ni concentration in the pore waters these findings have important environmental implications for better evaluating the protective role of mangroves against trace metal dispersion into marine ecosystems they may also help in predicting the response of mangrove ecosystems to increasing anthropogenic pressure on coastal areas

concentration distribution and assessment of heavy metals in sediments of mud area from inner continental shelf of the east china sea heavy metals cr cu zn cd pb hg and as grain size ph eh and total organic material tom and tn of 59 surficial sediments of mud area from the inner continental shelf of the east china sea have been analyzed the relations of the heavy metals to sediment composition ph reduction oxidation conditions and total organic materials were evaluated with multivariate statistics analysis and the hydrodynamic conditions such as coastal current and taiwan warm current are the other important controlling factors to the distribution of heavy metals sediment enrichment factors and potential ecological hazard index e text ri were used to assess the heavy metals accumulation the results indicate that moderate contamination of most heavy metals is prevalent and the contamination level in the estuary is rather high which is mainly from anthropogenic source compared with other areas in china the contaminant level of the study area is moderate

hydrogeochemistry and quality of groundwater of coastal unconfined aquifer in amol ghaemshahr plain mazandaran province northern iran groundwater of the unconfined aquifer 1 100 sq km of a two tier coastal aquifer located in the amol ghaemshahr plain mazandaran province northern iran is classified into fresh and brackish water types fresh groundwater fgw samples n 36 are characterized by ca2 na mg2 k and hco3 cl so4 2 no3 spearman s rank correlation coefficient matrices factor analysis data values of the c ratio av 0 89 and cai and values of the molar ratios of ca2 hco3 ca2 so4 2 mg2 hco3 and mg2 so4 2 indicate that the ionic load in the fgw is derived essentially from carbonic acid aided weathering of carbonates and aluminosilicates saline sea water trapped in the aquifer sediments now admixed with the groundwater and ion exchange reactions values of the cai and na cl molar ratio suggest that the part of the ca2 mg2 content in 23 fgw samples is derived from clay minerals of the aquifer matrix and part of the na content in 20 12 and 3 fgw samples is derived respectively from alkali feldspar weathering clay minerals of the aquifer matrix and rain water and or halite brackish groundwater bgw samples n 4 contain cl as the dominant anion and their average total ionic concentration 38 65 meq l is 1 79 times higher than that of the fgw samples 21 50 meq l bgw pockets were generated by non conservative mixing of fgw with the upconed saline water from the underlying saline groundwater zone of the semi confined aquifer along bore wells involved in excessive extraction of groundwater from the unconfined aquifer groundwater belongs essentially to high salinity low sodium irrigation water class

a review of the ecological and taphonomic controls on foraminiferal assemblage development in intertidal environments intertidal foraminifera from surface sediments are commonly used as a high resolution indicator of sea level change the integrity of this approach is based upon the assumption that surface assemblages are similar in composition to their buried fossil counterparts this assumption may in some cases be inappropriate due to subsurface or infaunal production and taphonomic alteration here we review the current understanding of foraminiferal production and taphonomic loss in intertidal environments and examine the extent to which these processes can affect the development of foraminiferal assemblages in intertidal environments as a sediment layer undergoes burial dead tests are added at a rate proportionate to the standing crop at that depth as a consequence test accumulation within the layer is proportionate to the depth integrated standing crop depending on the nature of its vertical living distribution the upper 1 cm of sediment may therefore not adequately characterise a given species total input instead a comparison of each species contribution to the entire depth integrated living community may offer a better a priori estimate of relative input to the sediment column this provides an improved base line for identifying true taphonomic trends downcore the potential for infauna to create discrepancies between surface and subsurface assemblages may be minimised however where 1 reproduction is concentrated near to the sediment surface transforming an apparent infaunal standing crop into an effective epifaunal production 2 the living fauna is composed similarly at all depths of production and or 3 intense bioturbation homogenises the upper sediment layers the likely decline in the intensity of taphonomic processes with depth may mean that the foraminiferal production from different depths may not experience taphonomic processes uniformly consequently in addition to their possible gradual enrichment due to subsurface production infaunal species may be preferentially preserved by virtue of their production closer to the base of the taphonomically active zone additionally homogenisation of the sediment column by reworking may mix temporally and perhaps environmentally distinct faunas affecting the stratigraphic integrity of the sediment deposit the most important taphonomic processes in intertidal environments are those associated with early diagenesis while the organic cements of agglutinated taxa may be directly oxidised the associated changes in the saturation state of porewaters with respect to calcium carbonate may affect calcareous species the type of diagenetic reaction operating within the sediment provides a quantitative control on agglutinated test degradation but a largely qualitative control on calcareous preservation in addition calcareous test preservation is dependent upon the rate with which organic matter is supplied while agglutinated test preservation is independent of organic matter concentrations although the specific morphological pathways of test degradation for calcareous species are well understood the stages under which agglutinated tests are lost are less clear the combined but varying influences of production infaunal and species composition taphonomic processes and bioturbation may create complex pathways in the transition from live to dead to fossil assemblages understanding the extent to which infauna taphonomic loss and sediment reworking affect assemblage development in different intertidal environments is essential in order to interpret the fossil record

wetland dynamics of marajo island northern brazil during the last 1000 years abstract the wetland dynamics in eastern amazon region during the last thousand years were studied by pollen analysis and ams radiocarbon date three sediment cores were sampled from the marajo island which is located at the mouth of the amazon river marajo island is covered mainly by amazon coastal forest herbaceous and varzea vegetation one core was obtained from lake arari which is surrounded by herbaceous vegetation flooded by freshwater two cores were sampled from an herbaceous plain that lies 45 km southeast from the lake arari the pollen records indicate that the herbaceous vegetation began its development approximately 800 cal yr b p the pollen percentages between 750 and 500 cal yr b p indicate the expansion of mangroves the predominance of herbaceous and varzea pollen occurs between 500 and 200 cal yr b p and the varzea pollen percentage increased during the last 200 years the vegetation changes proposed by the pollen records from the lake arari probably represent the regional vegetation dynamics of the marajo island while the pollen profiles from herbaceous plain present a smaller spatial representativeness of the vegetation the alternation between fresh and brackish water vegetation in the wetlands may indicate changes in the physicochemical characteristics of the sediment during the time interval studied

are mangrove forest substrates sediments or soils a case study in southeastern brazil abstract morphological and analytical data corresponding to several profiles from two mangrove systems in the brazilian state of sao paulo were examined for evidence of pedogenetic processes plant activity exerted a strong effect on the processes occurring in mangrove substrates especially on the intensity of these processes and therefore constitutes one of the major factors involved in the differentiation of sediments and soils colonization of substrates by vascular plants leads to drastic changes in physicochemical conditions the redox processes were much more diverse in the soil than in the sediment substrate without vegetation in the former they varied with depth with oxic or suboxic conditions being observed at the surface and anoxic conditions observed below 30 cm whereas in the sediment anoxic conditions were observed throughout likewise the acid base conditions were more variable in the soils ranging from strongly acid to neutral and in the sediment they were close to neutral furthermore different pedogenetic processes were identified 1 addition of organic matter by accumulation of vegetable debris and dead roots with formation in some cases of a histic epipedon 2 transfer of soluble iron fe2 towards the surface and precipitation in the form of fe oxyhydroxide and transfer of the mineral particles due to the bioturbation caused by activity of crabs 3 transformation of elements such as iron gleization and sulphur sulphidization changes undergone in the mangrove substrates were also characterized by simultaneity and intergradations between pedogenesis and diagenesis especially in the lowermost layers in which authigenesis appears to intensify thus the presence of smectite minerals in the clay fraction may be attributed to authigenic processes that take place in both soils and sediments

sulfide diagenesis and sedimentation in the albian harmon member western canada abstract the albian harmon member comprises three lithofacies lm laminated mudstone resulted from hemipelagic sedimentation under dominantly anoxic conditions lbs laminated to bioturbated siltstone was deposited primarily by distal storm or turbidity currents under dysaerobic to anoxic conditions icm interbedded conglomerate mudstone represents deposition of turbidites or tempestites in more proximal basin margin facies under dysaerobic to perhaps aerobic conditions the rapid and episodic deposition of lbs and icm compared to the slower steadier rate of deposition for lm lithofacies is interpreted to be a primary control on the carbon sulfur and iron systematics of the sediments and the morphology and isotopic composition of authigenic pyrite pyrite in lm lithofacies is homogeneously distributed and occurs almost exclusively as discrete framboids less than 20 m in size lm lithofacies is further characterized by relatively constant carbon sulfur ratios iron sulfur ratios and 34s values for pyrite that indicate virtual open system conditions with respect to sulfate evaluation of organic matter om maturity and hydrogen indices hi suggests that om reactivity limite sulfate reduction in these sediments pyrite in lbs and icm lithofacies transition zone generally is distributed heterogeneously and occurs as framboidal zoned or massive aggregates up to 400 m in size transition zone sediments have extremely variable carbon sulfur and iron sulfur ratios and pyrite 34s values pyrite in these sediments is enriched in 34s relative to lm sediments indicating that the exchange of sulfate between pore waters and the overlying water column was restricted with sulfate reduction sometimes occurring under virtual closed system conditions with respect to sulfate

hydrogeochemistry environmental isotopes and the origin of the hamamayagi ladik thermal spring samsun turkey hamamayagi thermal spring hts is located along the north anatolian fault zone the thermal spring has a temperature of 36 c with total dissolved solids ranging from 485 6 to 508 5 mg l hard brittle and gray limestones permian aged are the reservoir rocks of the hts 18o 2h isotope ratios clearly indicate a meteoric origin for the waters the 34s value of sulfate in the thermal water is nearly 4 1 and implies a diagenetic environment characterized by reduced sulfur compounds the 13c ratio for dissolved inorganic carbonate in the hts lies between 1 78 and 1 62 showing that it originates from the dissolution of fresh water carbonates quartz geothermometry suggests a reservoir temperature of 52 85 c for the hamamayagi geothermal field but chalcedony geothermometers suggest reservoir temperatures between 30 and 53 c

hydrogeochemical evaluation of groundwater of bhaktapur municipality nepal the present study aims to evaluate groundwater hydrogeochemistry of bhaktapur municipality nepal with respect to water types chemical elements and their statistical variability samples were collected in pre monsoon april june monsoon july august and post monsoon october november seasons in 2007 laboratory analysis of samples revealed inter seasonal variability primarily attributed to hydrogeochemical processes all or most of the samples exceeded the world health organization who guideline value glv for iron conductivity and turbidity while none of the samples exceeded who glv for hardness and arsenic with minor fraction exceeding glv for chloride content higher ammonia content in well water and highest phosphate concentration occurred for stone spout in pre monsoon season principle component analysis highlighted three principle components while the dendrogram divided the sampling sites into four and two clusters respectively for well water and stone spout water sampling sites saturation index computed through wateq4f model revealed that ferrihydrite siderite strengite and vivianite minerals were in under saturated state while goethite was in supersaturated condition for each type of samples well water and stone spout water in both pre and post monsoon seasons depicting their tendency to precipitate high degree of supersaturation in goethite mineral indicated response to temperature gradient of the reactions while under saturation for other minerals indicated the effect of dilution

investigating the characteristics of mine water in a subsea mine using groundwater geochemistry and stable isotopes investigation were conducted in the xinli subsea mine from 2006 to 2011 which is the largest subsea mine in china and threatened by the overlying quaternary aquifer and seawater hydrochemical and stable isotopic 2h and 18o analyses were used to study the relationships between various waters hydrochemical results indicated that the seepage water in the mine tunnels had higher ec tds and concentrations of most elements than the seawater and saline groundwater water analyses indicated the mine discharge was a mixture of the seawater brine and atmospheric precipitation the proportions of the three different sources were calculated based on hydrochemical and isotopic analyses the seepage water were more isotopically enriched than the seawater but less than the brine in addition the isotope mixing calculation indicated that the average proportions of mine water from seawater brine and atmospheric precipitation were about 38 5 46 and 15 5 respectively for the entire mine in 2006 however the concentrations of these analyses decreased and the proportion of the seawater increased 21 1 after 5 years of exploitation in 2011 these changes demonstrated that the surrounding rock mass underwent a certain extent of deformation and failure because of the mining disturbance which enhanced the permeability of the surrounding rock mass

pore water chemistry in mangrove sediments relationship with species composition and developmental stages french guiana spatial and seasonal variability of sedimentary salinity ph redox potential and solid phase sulphide concentration were investigated in a range of mangrove communities along the coast of french guiana seasonal depth distributions of these parameters and organic content were compared within avicennia rhizophora and mixed mangrove stands at different stages of plant development mangrove communities and variable surface water inputs strongly impact sediment and ground water properties in the upper sediment changes in salinity are mainly controlled by seasonal conditions transpiration and proximity of fresh water influx whereas we suggest that constant basal salinity results from an accumulation of salt that has migrated as a result of density driven convection processes there are no clear differences between the depth distributions of salinity obtained beneath avicennia germinans and rhizophora mangle stands implying that plant zonations are not primarily controlled by soil salinity in this environment nevertheless r mangle grows in places subjected to the greatest variability in freshwater influxes suggesting that rhizophora might require or withstand occasional inundation by fresh water beneath rhizophora stands sediment properties reflect anaerobic and sulphidic conditions close to the sediment surface in contrast beneath avicennia stands sediment geochemistry mostly depends on the stages in forest development on contents in sedimentary organic matter and on seasonal changes in the early stage of avicennia settlement the sediment at the level of radial pneumatophore bearing cable roots displays permanent suboxic conditions with eh values reaching 400 mv these high ehs are interpreted as an effect of the oxidation produced by the cable root system the development of mature avicennia stands results in accumulation of sedimentary organic matter and promotes low ehs and the reduction of pore water sulphate near cable root level the oxidation process observed in pioneer mangroves results in a reoxidation of solid sulphides produced previously during dry conditions the desiccation of the upper sediment adds its oxidation effects to those of root activity as a result suboxic processes dominate in the upper 20 cm thick layer organic matter decomposition and sulphur oxidation strongly acidify the sediment below 20 cm the sediment is anaerobic and sulphidic hence sulphide concentrations depend on the edaphic conditions controlling decay processes and appear to be a consequence rather than a cause of the observed zonation of vegetal species the small size of a germinans propagules might have a significant influence on the extensive development of this plant community along the highly dynamic coastline of the guianas this study demonstrates that the different properties of pore water were intimately linked and that the explanation of the evolution of this forest reflects a combination of multiple parameters moreover it appeared that the organic content played a key role along with the species composition and the seasonal variations waterlogging desiccation

how wet is wet precipitation constraints on late quaternary climate in the southern arabian peninsula it is generally recognized that the southern arabian peninsula has had two wet periods in the late quaternary to quantify wet a 28 000 year old capillary surface associated with a paleowater table was mapped and used as a surrogate for the water table in a ground water model analysis of this model suggests 1 4 mm year 1 of recharge is necessary to support the water table at the mapped elevations during the wet period climatic relations between rainfall and recharge in arid areas infer that annual rainfall during this wet period was approximately 200 50 mm year 1 or approximately five times the present rate

foraminiferal biofacies across mangrove mudflat environments at cocoa creek north queensland australia contemporary and relict subsurface intertidal foraminiferal dead assemblages were collected from a site near to cocoa creek north queensland australia and analysed for the purpose of understanding fossil assemblage development and preservation a marked dichotomy was identified between dead foraminiferal assemblages within mangrove sediments and those within adjacent mudflat sediments mangrove assemblages were almost exclusively represented by agglutinated species mainly arenoparrella mexicana haplophragmoides wilberti milliammina fusca m obliqua trochammina inflata while calcareous species dominated the mudflat mainly ammonia aoteana pararotalia venusta parrellina hispidula surface and subsurface test abundances were also an order of magnitude greater within mudflat sediments 1000 3000 tests per cm3 than in the sediments beneath the mangroves 100 300 tests per cm3 statistically significant differences in the abundance of calcareous and agglutinated tests between wet and dry seasons within the mangrove suggest that tests are systematically lost from this part of the system on an annual basis a model of assemblage formation under shoreface progradation is presented which makes a direct link between surface assemblages post depositional processes and the composition and environmental resolution of the fossil assemblages entering the stratigraphic record assemblages within the mangrove undergo rapid taphonomic loss and are then overprinted during burial by the deep infaunal communities associated with the prograding higher elevation environments as such much of the eventual mangrove sequence is represented entirely by assemblages produced relatively recently within an upper mangrove environment and therefore cannot be differentiated according to elevation at the time of deposition in addition organic enrichment of upper mudflat deposits by mangrove roots which occurs during progradation results in the dissolution of calcareous tests from an 40 cm thick stratigraphic interval it is argued that in order to reliably recognise the changes to foraminiferal assemblages which occur during burial assemblages must be compared with respect to stratigraphy rather than reflexively downcore

hydrochemistry assessment of groundwater quality in al ain city uae groundwater is the main source for irrigation purposes in al ain city urbanization and agricultural activities are considered potential sources of groundwater pollution in this area therefore assessment of groundwater quality is very important to detect and prevent contamination for effective groundwater management this paper focuses on the impact of urbanization on the groundwater resources of the gravel alluvial aquifer in the vicinity of al ain city northeast of abu dhabi emirate groundwater samples were collected from 28 wells in al ain city the chemical monitoring revealed high spatial variability in chemical parameters as influenced by climate matrix aquifer changes in geological formations and water table depth results show that changes in groundwater chemistry in the aquifer are mainly controlled by evaporation silicate mineral dissolution evaporite dissolution cation exchange and mixing by upward leakage from jabal hafit limestone aquifer the concentration increases were accounted for primarily by dissolved sodium chloride and sulfate the high total dissolved solids tds of shallow groundwater beneath the city of al ain up to 5640 mg l are mainly controlled by evaporation groundwater quality was better in the northeast and the east areas near oman mountains compared to the south area northern edge of jabal hafit

geochemical investigation of the south wellesley island wetlands insight into wetland development during the holocene in tropical northern australia the south wellesley islands in the gulf of carpentaria northern australia were the recent focus of a palynological investigation which found vegetation change during the holocene was driven by coastal progradation and regional climate here we present new elemental data from x ray fluorescence core scanning which provides non destructive continuous and high resolution analysis from three wetlands across bentinck island the largest of the south wellesley islands elemental data and grain size analyses are combined with lead 210 210pb and accelerator mass spectrometry ams carbon 14 14c dates an open coastal environment was present 1250 cal a bp on the south east coast of bentinck island with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock prograding shorelines dune development and river diversion formed a series of swales parallel to the coast by 800 cal a bp forming the marralda wetlands wetlands developed at sites

mangrove expansion in the gulf of mexico with climate change implications for wetland health and resistance to rising sea levels abstract black mangroves avicennia spp are hypothesized to expand their latitudinal range with global climate change in the 21st century induced by a reduction in the frequency and severity of coastal freezes which are known to limit mangrove colony extent and individual tree size the gulf of mexico is a prime candidate for population expansion to occur because it is located at the northward limit of black mangrove habitat this may come at the expense of existing coastal saline wetlands that are dominantly spartina spp marsh grasses the present study was conducted to focus on the implications of a marsh to mangrove transition in gulf wetlands specifically 1 wetland resistance to accelerating eustatic sea level rise eslr rates 2 resistance to wave attack in large storms increased cyclonic storm frequency intensity is predicted with future climate warming and 3 organic carbon sequestration and wetland soil geochemistry field sites of adjacent and inter grown avicennia germinans mangrove and spartina marsh populations in similar geomorphological setting were selected in back barrier areas near port aransas and galveston tx elevation surveys in the more mature port aransas site indicate mangrove vegetated areas are 4 cm higher in elevation than surrounding marsh on an average regional scale and 1 2 cm higher at the individual mangrove scale 210pb and 137cs accumulation rates and loss on ignition data indicate that mineral trapping is 4 1 times higher and sediment organics are 1 7 times lower in mangroves at port aransas this additional mineral trapping does not differ in grain size character from marsh accumulation elevation change may also be effected by soil displacement of higher root volumes in mangrove cores port aransas porosities are lower in mangrove rooted horizons with a corresponding increase in sediment strength suggesting mangrove intervals are more resistant to wave induced erosion during storm events port aransas mangroves exhibit higher pore water redox potentials and salinities over entire core depths and depressed ph over rooted intervals suggesting a distinct diagenetic environment exists relative to marsh sites the rooting network which introduces oxygen into the sediment and focuses evapo transpiration and salt exclusion within this zone may prove advantageous when competing with grasses by elevating salinities to levels that are toxic for spartina trends observed in the more mature systems of port aransas are generally absent in galveston suggesting the youth and physically shorter stature of these systems means they have not yet established a unique sediment signature

concentration distribution and assessment of heavy metals in the surface sediments of the western gulf of thailand heavy metals cr cu zn cd pb hg as grain size ph eh total organic carbon and total nitrogen of 157 surface sediments from the western gulf of thailand got were analyzed to determine the spatial distribution pattern constraint factors and pollution status of heavy metals in the surface sediments of the western got the relationships of the heavy metals with sediment composition ph reduction oxidation conditions and total organic materials were evaluated by statistical analysis sediment compositions were the main factors controlling the concentrations of heavy metals as reported in many previous studies while the hydrodynamic conditions in particular the seasonal eddies were an important factor controlling their distribution both sediment enrichment factor and geoaccumulation index were used to assess heavy metal accumulation only as reached the light contamination level near the upper got and the coastal area close to the songkhla province due primarily to anthropogenic activities

graphic derivation of the local sense of shear strain components in stretched walls of lithotectonic boundaries abstract lithotectonic boundaries ltbs are deformed interfaces between rock masses such as sheared strata midcrustal thrust slices or sutured microcontinents structural analysis of strained ltb walls have focussed attention on rock cuts through the foliation normal and mineral lineation direction but this practice is commonly inappropriate for investigating the tangential shear strain a simple graphic technique is introduced whereby one may derive the sense of large shear strain components in two sections across an ltb wall segment one section parallel to the lineation direction the other normal to the foliation the orientation of the strain ellipse is used on each section to deduce the sense of its shear strain component by visual inspection the technique is applicable to metamorphic rocks with l s mineral fabrics but without reliable gauges of large incremental or total longitudinal strain if the factor of prolateness oblateness of the strain ellipsoid is unknown then the direction cannot be fixed within an angle of journal of structural geology 20 969 973 however the direction may be accurately determined if an ltb cross section fortuitously contains the normal to foliation as well as the mineral lineation direction similarly the direction can be determined if the local strain ellipsoid corresponds to an oblate or prolate spheroid where the ellipsoid is nearly spheroidal one can therefore discern which of the two shear strain components under consideration has the larger magnitude this proves advantageous in assessing the sense of alleghanian tangential shear below the brevard fault zone grandfather mountain area southern appalachians here has the sense of a ductile thrust 1 km into the stretched footwall close to the fault zone however has a large sinistral component unless the ltb dip is 40