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

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

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

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

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

sedimentary succession and evolution of the mediterranean ridge western sector as derived from lithology of mud breccia clasts abstract rock fragments from mud breccia extruded by mud volcanoes discovered during the ttr 4 cruise of the r v gelendzhik on the western mediterranean ridge are represented by a number of different lithologies they provide important information on the composition genesis and age of the deep seated sedimentary series of the basin lithological description and age determination of the main rock types obtained as clasts from mud breccia were made on the basis of a study of ninety seven samples depositional processes and environments of their accumulation were determined using sedimentological criteria the sedimentary section through which mud volcanoes erupted on the western mediterranean ridge includes aptian albian claystones late cretaceous limestones paleogene siliciclastic rocks and a variety of miocene limestones and mudstones the rock clasts studied throw insight into the evolution of the western sector of the eastern mediterranean basin from at least aptian time the aptian albian clayey series have been deposited in the marine conditions of a relatively narrow basin with a high input of terrigenous clayey material during the late cretaceous the basin enlarged terrigenous input into deep parts of the basin decreased and carbonate pelagic sedimentation became prevalent regression in paleogene time led to the deposition of thick terrigenous siliciclastic series of deltaic prodeltaic sediments extensive turbidite systems were emplaced in the western sector of the eastern mediterranean during the miocene along with predominantly carbonate pelagic sedimentation

structure and palaeogeography of the external betic cordillera southern spain abstract a structural interpretation of the external betic cordillera in the granada jaen area of southern spain is proposed based on the interpretation of seismic reflection profiles subsurface well control and a balanced cross section restoration of this balanced cross section results in a new palaeogeographical interpretation for the area and a total estimated shortening of approximately 200 km traditionally the betic fold thrust belt has been described as a series of north vergent imbricate thrust sheets each having relatively little displacement 10 15 km restoration of this structural model to an undeformed state results in a mesozoic palaeogeographical scenario of three carbonate platforms separated by two deep basins an alternative interpretation is presented in this paper that the structural style of the granada jaen area is characterized by large displacement thrust faults restoration of the proposed cross section leads to the palaeogeographical interpretation of a single mesozoic basin along the transect of the cross section this palaeo basin is bounded to the north and south by platformal margins the major implication of this study is that the palaeogeographical interpretation of a fold thrust belt can be highly dependent on the structural interpretation

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

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

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

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

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

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

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

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

rock fragments from mud volcanic deposits of the gulf of cadiz an insight into the eocene pliocene sedimentary succession of the basin abstract two hundred clasts from the mud breccia extruded by the yuma mud volcano in the gulf of cadiz are used to establish an offshore stratigraphy the clasts are a very complex mixture of material from the sedimentary successions through which the mud volcano erupted and provide important information about the composition and genesis of deep seated strata we deal with fragments of rocks that were deposited millions of years ago subsequently buried and later erupted on to the seafloor rock fragments from the mud breccia studied in thin section under a polarizing microscope provide genetic indications suggestive of deep sea conditions during the accumulation of strata a reconstruction of the sedimentary succession through which the yuma mud volcano erupted and the depositional evolution of the gulf of cadiz was made on the basis of lithology and age determinations of the rock age and depositional environment documented by the clasts indicate that a marine basin existed in the gulf of cadiz area at least from the eocene and that in the early and middle eocene a deep sea fan depositional environment prevailed in the region resulting in the accumulation of thick turbidites the late eocene and oligocene are not represented among rock fragments from the mud breccia suggesting regional uplift and non deposition in the area sedimentation was re established in the miocene with the accumulation of a clayey aquitanian burdigalian succession pelagic carbonate sedimentation became predominant in the langhian time the serravallian early tortonian is characterized by a high supply of terrigenous material resulting in the deposition of turbiditic clays and sands shallow water sedimentation with accumulation of carbonate rocks prevailed in the basin during the middle tortonian

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

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

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

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

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

a new murid rodent assemblage from the upper siwaliks himachal pradesh india biostratigraphic phylogenetic and palaeobiogeographic implications abstract in case of freshwater deposits that cannot be isotopically dated or that lack a continuous sequence for magnetostratigraphic study rodent biochronology is an useful tool in making intra regional biostratigraphic correlations and dating isolated siwalik fossil localities within the himalayan foreland basin we here report a new fossil locality exposed near the village devni khadri situated close to the markanda river valley district sirmaur himachal pradesh india this upper siwalik locality belonging to the tatrot formation contains a diverse fauna and flora including large mammals birds crocodiles fishes gastropods bivalves ostracods and charophytes beside dental remains of murid rodents golunda kelleri mus flynni mus jacobsi and abudhabia cf a kabulense based on the biostratigraphic ranges of these murid rodents from well dated siwalik and karewa localities this richly fossiliferous locality has been placed here at 3 ma the new age facilitates regional correlation and a revision of stratigraphic placement of rodent bearing plio pleistocene indian sites a paup based cladistic analysis of fossil and extant golunda and its relatives suggest the monophyly of the golunda group and a close relationship between african and asian forms presence of common rodent elements in the fossil record of africa and asia points towards possible inter continental dispersal in pliocene time

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