mobility and fractionation of rare earth elements in argillaceous sediments implications for dating diagenesis and low grade metamorphism abstract we report sm nd and rb sr data for the fine fractions of lower paleozoic argillaceous rocks from wales uk and new york usa spanning the range of low grade metamorphic conditions from the diagenetic zone zeolite facies to the epizone greenschist facies in all cases leaching of the fine fractions results in a high 147 sm 144 nd 0 09 0 29 acid soluble component and a complementary low 147 sm 144 nd 0 05 0 14 residual component the observed fractionation is an ancient feature related to diagenesis burial and metamorphism the magnitude of sm nd fractionation between leachates and residues as well as the resulting sm nd ages vary as a function of grain size and metamorphic grade uncleaved welsh mudrocks of the diagenetic zone yield sm nd leachate residue ages of 453 484 ma in agreement with their llanviian to caradocian biostratigraphic ages whereas higher grade rocks of the anchizone and epizone yield sm nd ages as young as 413 ma these ages are transitional between the time of deposition and the time of regional deformation related to the acadian orogeny at 390 ma distinct convex upward rare earth element ree patterns of the leachates suggest that the precipitation of early diagenetic apatite controls the trace element budget of the rock forcing a depletion of middle rees on the subsequently formed diagenetic phyllosilicates the amount of organic matter present and the extent of later prograde reactions are probable modifiers of this fractionation process ordovician and devonian clastic rocks associated with the trenton and onondaga limestones of new york yield single sample and multi sample sm nd isochron ages that agree well with their biostratigraphic ages of 454 ma and 390 ma respectively the ree fractionation observed in shale leachates of the ordovician utica formation is related to ca mg of the bulk rock and hence to the composition of the diagenetic carbonate cement in all cases the sm nd system remained closed subsequent to the peak of diagenesis or metamorphism including the north american rocks that show no evidence of being isotopically reset during widespread remagnetization of the subjacent limestone units in the late paleozoic

hydrocarbon potential and depositional environment of the lower cretaceous black mudstones and shales in the coastal guangdong province china abstract the mesozoic especially the cretaceous sequences in the northern south china sea scs are important potential targets of oil and gas exploration however they are currently poorly understood we use organic petrology and geochemistry to evaluate the hydrocarbon potential and study depositional environment of the cretaceous black mudstones and shales from the dayawan section in the guangdong province china these mudstones and shales yield total organic carbon toc contents of 0 63 2 76 and most samples meet the requirement for higher toc source rocks organic matters in the mudstones and shales were sourced mainly from higher plants as well as subordinate benthic macroalgae organic petrology and geochemical data suggested that the organic matters were dominated by type iii and minor type ii and generally have low thermal maturity thus we evaluated the black mudstones and shales have a potential for hydrocarbon generation especially gas prone pr ph trace elements and mixture source of organic matter suggested that these black mudstones and shales formed in a coastal lacustrine environment characterized by weakly oxidizing weakly reducing conditions and low salinity a marine transgression developing in the middle part of the section was recognized generally the northern scs which exhibits the more marine influence likely contains source rocks with higher toc contents and better organic matter types the cretaceous source rocks with higher liquid hydrocarbon generation potential may occur locally in the pearl river mouth basin

origin of siderite concretions in microenvironments of methanogenesis developed in a sulfate reduction zone an exception or a rule abstract the mississippian shales from wardie scotland were deposited in a large normally brackish water basin they host siderite concretions with 13c values ranging from 3 5 to 12 1 which show that sulfate reduction and methanogenesis contributed to the production of bicarbonate fossils are found within each of the concretions suggesting that the decay of these organic remains provided a catalyst for concretionary growth the pore water was freshened which is indicated by the very negative 18o values from 12 8 to 4 7 many features indicate that the concretions are very early diagenetic precompactional precipitates the concretions are mostly homogeneous only a few exhibit complex concentric zoning the microstructure of the homogeneous concretions indicates a pervasive growth however their isotopic composition reveals a clear trend towards lighter 13c and 18o values from the center to the edge it is proposed that the concretions grew due to methanogenesis in microenvironments around large organic remains which acted as nuclei we suggest that this process may be one of the reasons for the very common occurrence of cements as mineral concretions not as disseminated precipitates along beds these microenvironments developed entirely within the sulfate reduction zone which resulted in the establishment of isotopic gradients in bicarbonate dissolved in the pore water across these microenvironments these gradients were caused by fast consumption of sulfate by the intensive oxidation of organic remains this resulted in the isotopic trends preserved in the homogeneous concretions the formation of the zoned concretions proceeded generally concentrically but detailed observations suggest that pervasive growth also contributed to their formation afterwards all the concretions were deeply buried probably within the oil window where late diagenetic phases crystallized mainly kaolinite quartz and sulfides

diagenesis and sedimentary environment of the lower xiaganchaigou formation deposited during the eocene oligocene transition in the lenghu tectonic belt qaidam basin china

rare earth elements in the permian phosphoria formation paleo proxies of ocean geochemistry abstract the geochemistry of deposition of the meade peak member of the phosphoria formation mpm in southeast idaho usa a world class sedimentary phosphate deposit of permian age that extends over 300 000 km2 is ascertained from its rare earth element ree composition ratios of ree al2o3 suggest two sources seawater and terrigenous debris the seawater derived marine fraction identifies bottom water in the phosphoria sea as o2 depleted denitrifying suboxic most of the time and seldom sulfate reducing anoxic this interpretation is supported by earlier research that showed progressively greater ratios in the marine sediment fraction of cr ni v ni mo ni relative to their ratios in seawater for which marine cr v and mo can have a dominantly o2 depleted bottom water source and ni a photic zone largely algal source the water chemistry was maintained by a balance between bacterial oxidation of organic matter settling through the water column determined largely by primary productivity in the photic zone and the flux of oxidants into the bottom water via advection of seawater from the open ocean samples strongly enriched in carbonate fluorapatite the dominant ree host mineral have variable er sm tm sm and yb sm ratios their distribution may represent greater advection of seawater between the phosphoria sea and open ocean during deposition of two ore zones than a center waste and greater upwelling of nutrient enriched water into the photic zone however the mean rate of deposition of marine ni a trace nutrient of algae and po43 a limiting nutrient indicate that primary productivity was probably high throughout the depositional history an alternative interpretation of the variable enrichments of er tm and yb relative to sm is that they may reflect temporally variable carbonate alkalinity of open ocean seawater in permian time a more strongly negative ce anomaly for all phosphatic units than the ce anomaly of modern pelletal phosphate is further indicative of an elevated o2 concentration in the permo carboniferous open ocean as proposed by others in contrast to the depletion of o2 in the bottom water of the phosphoria sea itself the oceanographic conditions under which the deposit accumulated were likely similar to conditions under which many sedimentary phosphate deposits have accumulated and to conditions under which many black shales that are commonly phosphate poor have accumulated a shortcoming of several earlier studies of these deposits has resulted from a failure to examine the marine fraction of elements separate from the terrigenous fraction

subsidence measurements in roads and implementation in land use plan optimisation in areas affected by deep coal mining this paper presents a study of 12 year monitoring of ground subsidence along a selected road affected by subsidences trough induced by underground black coal mining in the largest mining district in the czech republic the major scientific contribution of this study is that it suggests a new methodology that involves independent observation of a subsidence trough in the linear direction a road permitting determination of the ground deformation parameters and related building site categories in areas affected by deep coal mining it is vital to update the current status of the building site categories which represent the zones of potential hazard posed to the existing structures or future development it is possible to identify the actual conditions in the localities using systematical measurements along roads which are in any case required for periodical maintenance in areas of underground mining prognoses may be subsequently optimised in this way and investors property owners and mining companies may benefit through saving on costs associated with subsidence damage in fact there are two eventualities i e the conditions either improve or deteriorate the latter occurred in the case of the study area in the beginning the majority of the study area i e 91 belonged to the most suitable category of building sites which means that development was possible without any restrictions at the end of the observation the measurements showed a prominent fall of the subsidence trough and as much as 19 of the area fell into the least suitable categories i or ii where development is prohibited the publication recommends that mining companies use road monitoring as an independent monitoring tool to determine the hazard in regions affected by deep coal mining it is possible to conveniently verify the prognostic maps in land use planning in this way

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

nd isotope composition of conodonts an accurate proxy of sea level fluctuations abstract analyses of the nd isotope composition of conodonts from the anti atlas morocco the montagne noire france and the rhenohercynian domain germany provide insight into the temporal and lateral variations in seawater geochemistry in the western part of the variscan sea during the late devonian most of the isotopic excursions accurately record changes in sea level the end values decreased during regression phases when erosion accelerated supply of unradiogenic nd from old continental sources a rise in sea level generated a positive shift in end values due to input of more radiogenic oceanic water into the seawater reservoir of the shelf areas the method has great potential for sea level research paleoceanography and correlation because sea level changes can be precisely recognized even in successions with uniform monotonous lithologies however it has a significant limitation being valid only in epeiric seas and shelf areas we have used the nd isotope record to reconstruct the eustatic sea level changes in late frasnian early famennian time the onset of the organic rich kellwasser units coincides with negative trends in end values this accords with oxygen deficiency at the sea bottom being initiated by short term regressive events which in turn would be consistent with cooling periods of glacial origin as previous authors have suggested

postdepositional sm nd fractionation in sandstones implications for neodymium isotope stratigraphy abstract sandstone reservoirs from the norwegian continental shelf commonly show varying degrees of postdepositional fractionation of sm nd ratio apparently due to preferential incorporation of sm in the crystal lattice of diagenetic apatite based on data from leaching experiments an apatite mineral separate and petrography it is proposed that fractionation occurred mainly during closed system burial diagenesis as phosphate deposited on the sea floor recrystallized to apatite and incorporated rare earth elements ree from the surrounding rock matrix as a result the sm nd model age parameter in general contains two components of information a the true crustal age of the sediment and b a secondary component of sm nd fractionation which can be either negligible or dominant it is difficult to separate these components and thus correct for component b even in data showing no obvious signs of postdepositional fractionation model ages may be variably disturbed by subordinate amounts of diagenetic alteration however the isotope ratio 143nd 144nd is expected to be relatively resistant to alteration by secondary sm nd fractionation and should therefore be used rather than model age as the principal correlation parameter in stratigraphic studies in this way nd isotope stratigraphy can still be used as a valuable and unique tool for studies of provenance and correlation even in strata showing strong sm nd fractionation effects strongly sm nd fractionated horizons recognized by bulk rock sm nd ratios 0 23 may also be useful for stratigraphic correlation but it is clear that their occurrence reflects special depositional conditions rather than shifts in sediment provenance

violent volcanism stagnant oceans and some inferences regarding petroleum strata bound ores and mass extinctions past changes from a well mixed aerated ocean to a stratified stagnant ocean are indicated by decreasing 13c of limestone opposite to prior conclusions as well as by increasing 34s of marine sulfates the proposed stagnant ocean model includes a warm co2 enriched atmosphere and a bathyal to abyssal marine system dominated by bacterial components in the food web and by consequent light carbon in organic material and biogenic carbonates culminations of prolonged stagnant episodes correspond with marine faunal extinctions of late permian and late cretaceous time and the protracted changes and correlations provide evidence against any hypothesis of mass extinction by sudden worldwide catastrophe including the asteroid impact hypothesis the cretaceous stagnant ocean taken as the prime example is attributed to climatic warming triggered by volcanic co2 greenhouse effect and several feedbacks including decreased earth albedo and increased sinking of warm evaporite brines instead of aerated polar waters marine extinctions are attributed to upward expansion of the oxygen minimum zone and to catastrophic mixing of surface waters with poisonous sulfidic waters of the deeps the stagnant ocean provided a counterbalance between deep reduction and shallow oxidation conditions that favored maximal formation of black sulfidic shales protopetroleum and sedimentary sulfide ores and shallow to mid depth barite phosphorite iron ore cherty iron formation and sulfate bearing red beds trace elements concentrated in stagnant ocean sediments include chalcophile and pt group metals negating claims that ir provides a unique fingerprint of meteorite impact and cosmic accretion

changing redox conditions at cold seeps as revealed by authigenic carbonates from alaminos canyon northern gulf of mexico anaerobic oxidation of methane in anoxic sediments at cold seeps often leads to formation of authigenic carbonates close to the seafloor along continental margins recent work however indicated that the redox conditions in sediments may vary to some degree during seepage activity in order to shed new light on the extent of this variability authigenic carbonates from alaminos canyon lease block 645 of the northern gulf of mexico have been characterized by means of inorganic and organic geochemistry the carbonates were collected from seep deposits representing various seafloor morphologies including extensive pavements mounds fractured carbonate slabs surrounded by dense bivalve shells and vestimentiferan tubeworm colonies the deposits almost entirely consist of aragonite the 18o values of aragonite vary from 2 6 to 5 8 v pdb suggesting precipitation in slight disequilibrium with the surrounding pore fluids the 13c values of aragonite between 33 9 and 20 4 v pdb agree with variable amounts of carbonate derived from oxidation of thermogenic methane and crude oil methane was primarily oxidized in an anaerobic process as revealed by the presence of 13c depleted molecular fossils of methane oxidizing archaea 13c values as negative as 118 and sulfate reducing bacteria 13c values as negative as 97 the syntrophic partners in the anaerobic oxidation of methane the observed inventories of molecular fossils in the authigenic carbonates mirror those of known consortia of anaerobic methane oxidizing archaea anme and sulfate reducing bacteria namely the anme 2 desulfosarcina desulfococcus dss and anme 3 desulfobulbus dbb consortia in contrast the same carbonates exhibit shale normalized rare earth elements patterns that all display real negative ce anomalies ce ce 0 78 suggesting that at least temporarily oxic conditions prevailed the episodic occurrence of oxic conditions is confirmed by the presence of molecular fossils of aerobic methanotrophic bacteria including 4 methylcholesta 8 14 24 dien 3 ol and two bacteriohopanepolyols aminotetrol and aminotriol the 13c values of the biomarkers of aerobic methanotrophs are as negative as 58 and are consequently less 13c depleted than the molecular fossils of the prokaryotes performing anaerobic oxidation of methane a pattern in accord with culture experiments overall our results suggest that redox conditions at cold seeps are variable this variability probably reflects changes in seepage flux the combination of an inorganic and an organic geochemical approach used here is promising to better assess the variability and diversity of past fluid and gas expulsion at seeps

monitoring of coal mining subsidence in peri urban area of zonguldak city nw turkey with persistent scatterer interferometry using alos palsar this paper presents the results of spatiotemporal monitoring of surface subsidence over a mining area in zonguldak province of turkey using synthetic aperture radar sar data providing maps of subsidence rates in the radar line of sight direction a total of 18 sar images acquired between january 2007 and june 2010 by the japanese advanced land observing satellite have been used to map the surface displacements using the persistent scatterer interferometry technique the use of phased array type l band synthetic aperture radar data has proved useful for avoiding signal decorrelation and estimating surface deformation in the heavily vegetated study region the technique enables the monitoring of continuous small displacements over a large area our findings present that many persistent scatterers were located on the vegetation cover the results reveal areas of ground surface subsidence up to 44 mm year that are well correlated with the underground coal mining galleries particularly in the gelik region where the karadon mining galleries are present

iridium sulfur isotopes and rare earth elements in the cretaceous tertiary boundary clay at stevns klint denmark microbial activity and redox controlled precipitation have been of major importance in the process of metal accumulation in the strongly ir enriched cretaceous tertiary k t boundary clay the fish clay at stevns klint in denmark two important findings support this view 1 1 kerogen recovered by leaching the fish clay in hcl and hf shows an ir concentration of 1100 ppb this represents about 50 of the ir present in the bulk sample fish clay strong organometallic complexes is the most probable carrier phase for this fraction of ir kerogen separated from the k t boundary clay at caravaca spain similarly exhibits enhanced ir concentrations 2 2 sulfur isotope analyses of metal rich pyrite spherules which occur in extreme abundance about 10 by weight in the basal fish clay give a 34s value of 32 this very low value shows that sulfide formation by anaerobic bacteria was intensive in the fish clay during early diagenesis since the pyrite spherules are major carriers of elements such as ni co as sb and zn microbial activity may have played an important role for concentrating these elements in the fish clay large amounts of rare earth elements have precipitated from sea water on fish scales analyses reveal that compared with sea water the fish clay is only about four times less enriched in sea water derived lanthanides than in ir this shows that a sea water origin is plausible for elements that are strongly enriched in the clay but whose origin cannot be accounted for by a lithogenic precursor

the environment of deposition indicated by the distribution of rare earth elements in fossil bones from olduvai gorge tanzania fossil bones of pleistocene age from olduvai gorge tanzania incorporated relatively high concentrations up to several thousands ppm of rare earth elements during their fossilization the data indicate that these elements were mobile during the diagenetic processes involved in the fossilization of the bones it is suggested that the high concentrations arose through interaction of the bone with groundwaters enriched in these and other elements introduced by contemporaneous carbonatitic or alkalic volcanism the distributions of the rare earth elements within both the fossil bone and enclosing sediment are heterogeneous but spatially systematic with concentration profiles showing a maximum in the bone at its sediment interface despite the relative porous nature of bone the steepness and variability of the rare earth element profiles indicate chemical equilibrium has not been reached of the individual rare earth elements ce behaved differently from the others systematic variations in and magnitudes of the ce anomaly within the bone cortices from different depositional environments indicate that the redox potential of the environment during fossilization was the principal factor affecting the distribution of this element

late pleistocene mammoth trackway from fossil lake oregon abstract behavior of columbian mammoths mammuthus columbi is revealed by a newly discovered trackway at the pleistocene locality of fossil lake oregon our 8 by 20 m excavation of the mammoth trackway found 117 tracks including one 20 m long adult trail partial trackways of 3 additional adults a yearling and a baby all heading generally west the tracks are in the marble bluff biotite tuff 43 2 cal ka which forms a surface horizon to the pogani silty clay loam paleosol natrargid with a cracked surface and a columnar structured subsurface bn horizon like soils under desert soda pans with alkali shrubland directly below is the yada silty clay paleosol xeroll with crumb textured surface a horizon like grassland soils the pasiwa loam psamment is a thin brown siltstone with sparse roots and burrows of lake margin early successional vegetation the pui sandy loam aquent is well bedded tuff and sand a with subhorizontal calcareous rhizomes and adventitious roots like those of lake margin tule reeds schoenoplectus acutus columbian mammoths may have moved like modern elephants with infants in matriarchal groups through landscapes of sagebrush and grassland and this trackway includes a limping female attended by concerned juveniles grassland paleosols common in the fossil lake formation are now rare in the same region perhaps related to extinction of proboscidean and equine grazers

geochemistry of the rare earth elements in hypersaline and dilute acidic natural terrestrial waters complexation behavior and middle rare earth element enrichments rare earth element ree speciation was modelled in acid 2 9 ph 3 5 hypersaline groundwaters from australia and from the palo duro basin in texas usa using a combined specific ion interaction pitzer model and ion pairing model the free metal ion species i e ln3 is the dominant form of dissolved rees in these systems accounting for 40 70 of the dissolved metal in groundwater from lake tyrrell victoria australia 50 90 of the rees in groundwater from lake gilmore western australia and always 90 of each ree in the texas groundwaters lakes tyrrell and gilmore are actually dry lakes that act as groundwater discharge zones the abundance of the free metal ion species increases in these waters with increasing ionic strength and with decreasing ph the free metal ion species is followed in abundance by ree sulfate and ree chloride complexes that account for 20 50 and 10 15 respectively of the dissolved rees in the groundwaters from lake tyrrell 15 30 and 5 20 respectively in the groundwaters from lake gilmore and 3 and 7 respectively in the palo duro basin groundwaters the groundwaters of the lake tyrrell system and the palo duro basin are enriched in the middle rees mrees compared to both the light rees lrees and the heavy rees hrees only nd sm and dy were determined in the lake gilmore groundwaters and consequently it is unclear whether these acid groundwaters are also enriched in the mrees previous investigators suggested that fe rich organic flocs ree phosphate complexation and solid liquid exchange reactions between terrestrial waters and mree enriched surface fe mn coatings suspended particulates or secondary mineral phases within aquifer materials may promote the development of mree enrichments in natural waters we propose that organic colloids and ree phosphate complexes are insignificant in acidic natural waters in regards to mree enrichments instead solid liquid exchange reactions or dissolution of surface coatings suspended particulates and or secondary phases as well as sulfate complexation more likely controls the development of mree enrichments in acidic natural terrestrial waters

unique documentation analysis of origin and development of an undrained depression in a subsidence basin caused by underground coal mining kozinec czech republic this article aims to explain and demonstrate the origin and development of a subsidence basin caused by coal mining as well as to point out important aspects of this phenomenon in engineering geology engineering geology needs to deal with a number of issues related to the origin and development of subsidence basins in areas affected by deep coal mining an interesting case study from the upper silesian basin in the northeast of the czech republic near the polish border is presented in this paper there is a clear time chronological succession in the ground surface changes manifested by a ground subsidence gradation both in their absolute values as well as in their spatial distribution the phenomenon is documented by aerial photo time series which optimally depict the origin and development of the subsidence in the study area there are changes in the landscape elements and it is essential to be considered in future land use plans the marginal conditions of the quaternary geological structure and hydrogeological conditions are responsible for an unconfined aquifer which manifests there as a water body in an undrained depression in the course of the ground subsidence

rare earth element concentrations and speciation in organic rich blackwaters of the great dismal swamp virginia usa concentrations of rare earth elements ree major inorganic solutes and dissolved organic carbon doc were measured in waters from the great dismal swamp in southeastern virginia including lake drummond ph 4 3 and its principal surface inflows and outflow concentrations of ree are high in the lake average nd 8 nmol kg and the acidic doc rich inflow and out flow waters i e nd 12 5 nmol kg in jericho washington ditch and 8 nmol kg in feeder ditch respectively the slightly acidic ph 6 6 4 inflow waters from west of the suffolk scarp that comprise the chief source of surface water flow into lake drummond exhibit lower ree concentrations nd 3 4 7 nmol kg great dismal swamp waters are all enriched in the middle rees compared to the light and heavy rees lree and hree when normalized to upper continental crustal ucc values rare earths are positively correlated to doc concentrations in great dismal swamp waters and inversely correlated with ph speciation calculations using a modified version of the well established humic ion binding model v predict that organic matter complexes are the predominant form of dissolved rees in great dismal swamp waters despite significant competition from aqueous fe and al for organic matter binding sites adsorptive cathodic stripping voltammetry acsv was employed using a previously developed competitive ligand equilibration approach that involved adding the o cresolphthalexon ocp ligand to directly investigate ree complexation with natural organic ligands in great dismal swamp waters although preliminary the results of the acs voltammetric titrations are consistent with dominance of organic matter complexes of rees in great dismal swamp waters the results of the speciation modeling and the voltammetric titrations all point towards control of dissolved rees in great dismal swamp waters by complexation of these heavy metals with natural organic matter

rare earth elements in solnhofen biogenic apatite geochemical clues to the palaeoenvironment rare earth element ree concentrations in biogenic apatite samples coprolite bone and soft tissue were used to investigate the environment of deposition of the celebrated solnhofen fossil lagerstatten the measured ree patterns are similar between different localities lithologies flinz faule and levels in the upper solnhofen plattenkalk suggestive of a stable ree supply during deposition the behaviour of cerium in the solnhofen samples implies that bottom water conditions were not anoxic and variations in the cerium anomaly can be explained by differences in burial rate these results provide further geochemical support for current depositional models barthel k w 1978 solnhofen ein blick in die erdgeschichte ott verlag thun barthel k w swinburne n h m conway morris s 1990 solnhofen a study in mesozoic palaeontology cambridge univ press cambridge that propose that extra basinal processes are responsible for the interbedded nature of the solnhofen deposits rather than intra basinal processes such as water turnover events

interelement relationships in ferromanganese crusts from the central pacific ocean their implications for crust genesis the fine scale chemical variations in ferromanganese fe mn crusts from the central pacific ocean were investigated using a variety of techniques in order to elucidate their genesis thirty seven major minor and trace elements were determined by icp oes and icp ms in sub samples collected at approximately 2 mm intervals throughout the crust sequences an inverse relationship is observed between the logarithm of the elemental distribution coefficients log cmncsw and the mean residence time tr of elements in seawater these associations provide evidence supporting the strong link between seawater and fe mn crust chemistry results of factor analysis reveal that elements in crusts can generally be partitioned into four major groups with selected elements displaying associations with several groups these statistical associations are interpreted to represent hydrogenetic mn ni co cu ce zn biogenic ba zn cu pt fe detrital al si fe and carbonate fluorapatite ca p ree groups a comparison between elemental associations in fine scale data from individual crust sequences and bulk compositional data from samples collected in separate locations reveals very similar elemental associations the similar elemental associations in bulk samples and in fine scale subsamples from individual crusts are consistent with the notions that hydrogenetic crusts exhibit no significant post depositional remobilization of elements and that elemental distributions within crusts reflect the chemistry of oceanic water during the period in which they accreted chemical paleotracks are proposed based on factor scores derived from chemical variations as a function of depth in individual crusts our results show that there is internal consistency between the chemical evolution previously proposed seamount paleotracks and nanofossil biostratigraphy dating results

rare earth element evolution of phanerozoic seawater recorded in biogenic apatites rare earth element ree contents of marine biogenic apatites have been shown to record seawater compositions a data base of available and newly acquired rare earth element ree contents of marine biogenic apatites has been created to assess the past seawater ree compositions to ensure that this data base contains only the pristine ree signals altered samples characterized by very low la sm n ratios where n stands for ree ratios normalized to the nasc composition gromet et al 1984 geochim cosmochim acta 48 1984 2469 acquired during apatite recrystallization are not included in the database these data reveal a change in the tethyan seawater composition between 110 and 80 ma after the end of the cretaceous the ree chemistry of seawater remains constant until present day this seawater composition change is likely due to concurrent changes in ree scavenging processes a strong correlation between decreasing sm yb n ratios and increasing ce anomalies for samples deposited during the 80 110 ma period is observed as ce anomalies are attributed to ocean water redox conditions changes in ree scavenging could reflect an evolution from stratified and poorly oxygenated waters towards well mixed and oxygenated waters this could have resulted from changing current patterns stemming from the contemporaneous opening of the atlantic ocean a major change in middle and late cretaceous oceanic circulation linked to plate tectonics would have favored the colonization of pelagic environments

geological characteristics of strata in chongqing china and mitigation of the environmental impacts of tunneling induced geo hazards this study investigated the geological characteristics of strata in chongqing and the tunneling induced geo hazards therein the urban area of chongqing contains six syncline anticline pairs and is bounded by the huayingshan basement fault to the west and by the changshou zunyi basement fault to the east the bedrock containing sandstone and mudstone of the upper shaximiao formation resulting from middle triassic strata is occasionally outcropped during urbanization many valleys in chongqing require to be backfilled to create more flat ground thus the extent and thickness of the loose backfill layer varied from place to place while tunneling in chongqing the following geological characteristics may cause geo hazards 1 backfill with a loose structure poor gradation high permeability and large void ratio 2 highly or moderately weathered mudstone and sandstone that can easily become softened once subjected to groundwater seepage and 3 syncline folding containing perched water or confined fissure water the potential geo hazards include groundwater ingress ground surface settlement and strata collapse while tunneling within backfill synclines sandstone synclines or weak fractured rock significant amount of groundwater may be encountered thus leading to a high risk of groundwater ingress ground surface settlement can be triggered due to the disturbances of tunnel construction to the backfill or consolidation effect after groundwater ingress strata collapse can be caused by the blasting induced disturbances to poor surrounding geology or by inadequate overburden thickness or by an increase in the effective stress resulting from groundwater loss caused by leakage to mitigate the environmental impacts of the tunneling induced geo hazards a series of countermeasures that is advance geological drilling advance ground improvement including full face grouting and grouting of the surrounding geologic media and advance pipe umbrella use are proposed in this paper the results from a case study indicate that the proposed countermeasures can greatly decrease the ground surface settlement and amount of groundwater ingress during tunneling in chongqing verifying the effectiveness of the proposed countermeasures

manganese ores in tunisia genetic constraints from trace element geochemistry and mineralogy abstract northern and central tunisia hosts few small scale stratiform and stratabound mn deposits low to medium in grade mn

deciphering the upper famennian hangenberg black shale depositional environments based on multi proxy record abstract presented for the first time in this paper are the results of a detailed multi proxy investigation conducted on the hangenberg black shale hbs from the polish part of the laurussian shelf which provide details about the environmental conditions in existence during deposition of the shale and the role played by anoxic conditions in the mass extinction events that occurred at the end of the devonian times inorganic and organic redox indicators indicate that bottom water redox conditions changed periodically from being mainly anoxic euxinic to oxic or being partially depleted in oxygen u th values above 1 25 ni co values above 7 and v v ni values above 0 8 recorded from the lower part of the hbs all point to anoxic euxinic conditions being present as do high total organic carbon contents toc above 10 and degree of pyritisation dop values around 0 75 however the presence of benthic fauna over the lower part of the hbs attests to opportunistic colonisation of the seafloor during oxic episodes evidence for similar episodes has also been recognised over the middle part of the hbs e g u th values below 1 25 ni co values below 4 v v ni values below 0 8 toc values of 3 to 5 5 and dop values of 0 4 to 0 75 plus the common occurrence of benthic fauna anoxic conditions returned during the deposition of the upper part of the hsb though they were not as well developed as when the lower part of the shale was laid down of interest is the presence of small pyrite framboids and isorenieratene biomarkers in all the analysed samples which suggest that euxinic conditions persisted in the photic zone of the water column a twenty centimetre thick layer of volcanogenic deposits tuffites is present in the middle part of the hbs the geochemical characteristics of which are typical of ocean floor basalts the occurrence of volcanogenic material below and within the hbs together with an absence of calcium carbonate over its upper part the presence of abundant tetrads just above the black shale and a drastic decrease in faunal frequency in the upper part of the hbs imply that volcanism may have caused oceanic acidification or hypercapnia that in turn potentially may have influenced the hangenberg mass extinction event

the recommended cambrian ordovician global boundary stratotype of the xiaoyangqiao section dayangcha jilin province china this paper provides a brief outline of the current detailed inter disciplinary work on the xiaoyangquiao section trying to expose all the aspects for reference tied to the global single stratigraphic point gssp concept for defining the cambrian ordovician boundary the 45 m critical interval of this section outcrops very well along the steep bank of a stream and is free from folding faulting intrusions and has not been affected by weathering colour alternation of conodonts and acritarchs and crystallinity indices of illite all indicate a maximum thermal grade of 100 c the lithofacies being of great lateral persistence for a hundred kilometres consists mainly of a rhythmical sequence of lime mudstone and shales deposited in a moderately deep outer shelf environment of quiet water well below the normal storm wave base chemical investigation of the rocks demonstrates strong positive correlation between a12o3 content and those of k2o mgo fe2o3 tio2 be cr co ni zn and ba indicating these components are tied to the clay fractions a stable depositional environment is demonstrated by the uniform chemistries through the boundary interval close to the boundary itself p2o5 contents are low indicating continuous sedimentation at fairly substantial rates the major biological events the biostratigraphic framework and the stratigraphic range of conodont graptolite trilobite and acritarch taxa are illustrated briefly with diagrams following the majority views of the calgary plenary session the boundary level is to be chosen at a point marked by the first appearance datum fad of the selected conodont taxon or taxa in the vicinity of the level close to but below the first influx of nematophorous graptolites the following four points marked by the incoming of conodont taxon or taxa are recommended for consideration of the golden spike 1 fad of cordylodus intermedius at 5 28 m below the first influx of nematophorous graptolites 2 fad of hirsutodontus simpler cordylodus drucei albiconus postcostatus at 5 23 m 3 fad of semiacontiodus lavadamensis utahconus utahensis monocostodus sevierensis at 3 85 m 4 fad of cordylodus lindstromi at 2 23 m for the following reasons the fad of h simplex c drucei a postcostatus is favoured 1 the taxa are all distinct and widely dispersed 2 intensive evolutionary change took place in conodonts graptolites trilobites and acritarchs prior to or after this point all the fossil groups occur together providing correlation with many regions throughout the world 3 the point is in a position between the previously widely accepted boundary levels based on graptolites and trilobites 4 the proposed point lies within a thin laterally persistent rhythmical sequence the fad of cordylodus lindstromi is also a favourable point sharing many advantages mentioned above but this point is less satisfactory in being defined by the fad of a single taxon c lindstromi which also has an extremely small population size an isochron age of 500 7 7 4 ma is determined from clay fractions of mudstones 8 5 m below the proposed point by means of the rubidium strontium method the nd signature determined from conodonts trilobites hyolithids and acrotretid brachiopods has a mean value of 6 7 comparable with that of the coeval oceanic water mass occupying southeastern north america and europe and indicating that northeastern china bordered the same ocean the mean tdm model age determined was 1 26 ga at the time of sedimentation compatible with the mean tdm model age of approximately 1 1 ga for the pacific ocean today the relatively low value of the tdm model age indicates a substantial input from young orogenic volcanic island arcs and terranes

geochemistry of late permian to early triassic pelagic cherts from southwest japan implications for an oceanic redox change major trace and rare earth element abundances were determined for the southwestern japanese pelagic chert sequence from the early late permian to early early triassic to investigate a redox change in deep sea pelagic environments before and at the permo triassic boundary ptb 251 ma the sequence was primarily deposited in the deep sea of the superocean panthalassa and then was accreted to japan in the middle jurassic a remarkable lithostratigraphic change from red chert to siliceous carbonaceous claystone through gray chert is observed in this sequence constituent elements for these sedimentary rocks are essentially derived from two sources 1 an ancient seawater via biogenic mainly radiolarian hydrothermal and authigenic materials and 2 an average shale like terrigenous material the present measurement demonstrates significant stratigraphic changes of the ce cenon ter value estimated ce anomaly value of non terrigenous component recalculated by subtraction of terrigenous rees from bulk rees and the mn te sample mn te paas value excess mn component other than terrigenous one te terrigenous elements including ti al nb hf th paas post archean average australian shale in the permian chert the ce cenon ter values increase from 0 2 to 1 and the mn te sample mn te paas values decrease up section suggesting that the redox condition of deep sea open ocean changed from oxic to suboxic in an interval of approximately 10 myr the fe te sample fe te paas and mn te sample mn te paas values of carbonaceous claystone near or at the ptb are less than unity suggesting that reductive dissolution of iron and manganese occurred under an anoxic condition this supports the idea of the ptb oceanic anoxia in the superocean panthalassa the present data suggest that the anoxic condition prevailed in the deep sea pelagic regions for an extremely long period much more than 10 myr from the middle late permian to early early triassic this long term development of widespread oceanic anoxia may have been linked to the greatest mass extinction of the phanerozoic

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

geochemistry of red residua underlying dolomites in karst terrains of yunnan guizhou plateau ii the mobility of rare earth elements during weathering the aim of this study is to characterize the evolution of the rare earth elements ree in the pingba red residua on karst terrain of yunnan guizhou plateau the in situ weathering and the two stage development of the profile had been inferred from ree criterions the ree were significantly fractionated and ce was less mobilized and separated from the other rees at the highly enriched top of the profile this is consistent with the increase of oxidation degree in the regolith and it is also suggested that the wet dry climate change during chemical weathering caused ce alternative change between enrichment and invariance in the upper regolith chondrite normalized ree distribution patterns for samples from dolomites and the lower regolith are characteristic of mree enrichment and remarkable negative ce anomalies patterns similar to the convex up ree patterns the following processes are interpreted for the patterns in this study 1 the accumulation of mrre rich minerals in dolomite dissolution 2 water rock interaction in the weathering front and 3 more leaching mree from the upper part of the profile the latter two explanations are considered as the dominant process for the formation of the ree patterns samples from the soil horizon exhibit typical ree distribution patterns of the upper crust i e la n yb n 10 and eu eu 0 65 all data indicate that the leaching process is very important for pedogenesis in this region the experiments demonstrating that abnormal enrichment of ree at the upper regolith bedrock interface is caused by a combination of volume change accumulation of ree bearing minerals leaching of ree from the upper regolith and water rock interaction during rock soil alteration processes our results support the conclusion that the weathering profile represents a large continental elemental storage reservoir whereas ree enrichment occurs under favorable conditions in terms of stable tectonics low erosion and rapid weathering over sufficiently long time c 2003 elsevier b v all rights reserved

authigenic carbonates from methane seeps of the northern congo fan microbial formation mechanism abstract authigenic carbonates were collected from methane seeps at hydrate hole at 3113 m water depth and diapir field at 2417 m water depth on the northern congo deep sea fan during rv meteor cruise m56 the carbonate samples analyzed here are nodules mainly composed of aragonite and high mg calcite abundant putative microbial carbonate rods and associated pyrite framboids were recognized within the carbonate matrix the 13c values of the hydrate hole carbonates range from 62 5 to 46 3 pdb while the 13c values of the diapir field carbonate are somewhat higher ranging from 40 7 to 30 7 pdb indicating that methane is the predominant carbon source at both locations relative enrichment of 18o 18o values as high as 5 2 pdb are probably related to localized destabilization of gas hydrate the total content of rare earth elements ree of 5 hno3 treated solutions derived from carbonate samples varies from 1 6 ppm to 42 5 ppm the shale normalized ree patterns all display positive ce anomalies ce ce 1 3 revealing that the carbonates precipitated under anoxic conditions a sample from hydrate hole shows a concentric lamination corresponding to fluctuations in 13c values as well as trace elements contents these fluctuations are presumed to reflect changes of seepage flux

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

paleoceanographic implications of rare earth element variability within a femn crust from the central pacific ocean abstract results of detailed geochemical analyses of thick fe mn oxide crust accumulations from the central pacific ocean lead to the suggestion that variations in their chemical composition and microstructure reflect the influence of prevailing environmental conditions at the time of formation of the deposit these findings imply that well preserved fe mn crusts represent a geologic record that may extend back to the onset of fe mn oxide precipitation on the subsrtate material current crust growth rate estimates of 1 3 mm m y imply that 6 10 cm thick fe mn oxide accumulations represent a growth record of 20 to a maximum of 100 m y detailed chemical and mineralogical analyses were performed on successive hand picked layers of a 95 mm thick fe mn crust recovered from schumann seamount in the hawaiian archipelago the analyses reveal significant variations in the elemental distribution and abundance of major constituents and rees as a function of depth within the crust the trivalent rees generally exhibit sympathetic concentration changes in pure fe mn oxides but the fractionation observed between the light and heavy rees differs in layers enriched in phosphatic matter the compositional variability and the extent of ree fractionation can be explained in large part by mineralogical control but can also be inferred to reflect differing depositional conditions in the seawater from which the deposits formed variations in the ce anomaly and ree fractionation patterns within the individual layers of the crust are related to their major element composition and mineralogy and to the anomalies observed by other workers these are used to attempt to reconstruct the growth history of the crust

rare earth elements in the terminal ediacaran bambui group carbonate rocks brazil evidence for high seawater alkalinity during rise of early animals abstract rare earth elements plus yttrium rey mass fractions of ancient carbonate rocks are used to track changes in chemistry of past seawater here we investigate rey patterns in two carbonate sections from the ediacaran bambui group sao francisco basin brazil which comprise its two lowermost transgressive regressive second order sedimentary sequences shale normalised distributions vary with the sequence stratigraphy framework in the basal 2nd order sequence carbonate samples from the basal sequence transgressive systems tract display light rey lrey distributions slightly depleted to enriched that reflect input of freshwater possibly in a post glacial episode upwards carbonate rocks from the early highstand systems tract ehst yielded lrey enriched distributions which progressively turns into lrey shale normalized depleted distributions on samples from the late highstand systems tract lhst this portion of the sequence also displays y positive anomaly in some cases carbonate samples from the upper second order sequence do not display coherent patterns ce ce values 1 in most samples throughout the two sections suggest permanent anoxia of seawater the rey change from the ehst to lhst in the basal sequence marks an important paleoenvironmental overturn in the basin with increasing alkalinity in seawater driving rey fractionation and lrey depletion confinement of the basin in the inner areas of west gondwana due the uplift of marginal neoproterozoic orogens probably changed the weathering style of source areas to more congruent thus delivering a higher ionic influx to a restricted setting increasing alkalinity during lhst cloudina sp fragments were reported in this stage of the bambui group and in carbonate rocks with high sr mass fractions in other west gondwana basins supporting the hypothesis that the high alkalinity of seawater during late ediacaran may have driven the appearance of the first biomineralizing organisms

the whole rock cerium anomaly a potential indicator of eustatic sea level changes in shales of the anoxic facies abstract the whole rock cerium anomaly tested for outer shelf upper slope stratigraphic sections from the middle ordovician through the lower silurian of scotland is proposed as an empirical technique to develop a eustatic 3rd order or finer scale sea level curve this interval was chosen as it straddles the well documented late ordovician glaciation and can be defined by graptolite zones the anomaly is calculated from neutron activation analysis of low carbonate phosphate free fossil free field identified shales of the graptolite facies by comparison of the normalized cerium content with the linearized trend of the normalized composition of other rare earth elements in order of atomic number for sections originally deposited in the main pycnocline below the surface mixed layer values of the anomaly for a given sample would indicate its position on the redox curves developed for the early paleozoic by wilde 1987 changes in the anomaly that are positive with time would indicate a lowering of sea level as the apparent depth on the redox curve would reflect more oxic conditions relative changes negative with time would indicate a rise in sea level as the apparent depth reflects more anoxic conditions depending on the vertical sample spacing and the time interval sampled resolution of the order of 1 m y might be achieved thus the vail et al 1977 curves of the 3rd order 1 to 10 m y or of finer scale could be obtained by this technique with the proper choice of section accordingly for the early through middle paleozoic when the main pycnocline was anoxic this geochemical technique could be used to develop eustatic sea level curves and additionally offer an independent calibration for seismic stratigraphy as well as an indicator of glacial interglacial climatic sequences or eustatic changes due to fluctuations in global ridge crest volumes

the geochemistry of rare earth elements in the seasonally anoxic water column and porewaters of chesapeake bay a twelve cruise time series study of a seasonally anoxic basin in chesapeake bay was carried out between february 1988 and february 1989 data from filtered bottom water and upper 0 1 cm porewater samples are presented this is the first study in which time series measurements have been employed to understand the low temperature geochemistry of rare earth elements rees the focus is on the coupling between redox reduction oxidation variations and ree cycling fractionation of trivalent rees and development of cerium anomalies the time series results demonstrate that rees have large seasonal cycles in both the water column and porewaters in response to the development of anoxia in the spring and reoxygenation in the fall the transition from oxic to suboxic to anoxic conditions results in the release of rees into the upper porewaters and bottom waters the release of rees and fe are coincident in the bottom waters while the release of rees lags fe by approximately 50 days in the upper porewaters this decoupling is explained in terms of a redox front which moves upward from the sediments to bottom waters during the development of seasonal anoxia the release of rees to the upper porewaters and bottom water are accompanied by 1 1 fractionation across the trivalent ree series and by 2 2 the preferential input of ce relative to its trivalent only ree neighbors ree iii fractionation is such that the relative rate of release increases from lu to la light ree middleree heavyree during reoxygenation removal of dissolved rees occurs from both the water column and upper porewaters and follows the same relative rates lree mree hree cerium removal occurs faster than its neighbor ree iii indicating a rapid oxidation of ce iii to ce iv

geochemical decoupling of water masses in the variscan oceanic system during late devonian times abstract neodymium isotope data obtained from conodonts collected in morocco and poland attest a geochemical decoupling of seawater in the variscan realm during the late devonian the water masses on the shelves were characterized by unradiogenic e nd values from about 7 to 12 the surface water in the bordering oceans the rheic ocean and the variscan sea yielded more radiogenic e nd values ranging from about 1 to 6 a compilation of nd and c isotope signatures from the moroccan meseta suggests that the shelf and the surface oceanic water differed also in their carbon isotope evolution the geochemical decoupling constrains a restricted water exchange between shelves and the ocean oceanic waters entered far into the shelf areas only during the semichatovae transgression in the frasnian zone 11 sea level fluctuations constituted the major force that modified circulation and thus controlled the mixing of shelf and surface oceanic seawater the nd conodont data reveal that the surface water of the variscan oceanic water resembled the seawater of the modern pacific ocean rather than those of the atlantic and indian oceans the geochemical character of the variscan oceanic water is consistent with the geotectonic regime of the variscan realm in late devonian and carboniferous times

influence of overburden mass behavioural properties on subsidence limit characteristics abstract an analytical calculation model for the angle of draw is introduced in this paper on the supposition that the roof is considered as an elastic beam this model indicates the importance of the main factors which control the extent of subsidence produced on the surface and also provides some appreciation of the influence of overburden strength on the angle of draw a finite element model has been developed for application to subsidence related rock mechanics problems by the use of this model the authors have investigated the effects rock mass behavioural properties on the limit angle and also the effects of a distinct bed strong or weak in the overburden on the subsidence affected area at the surface relevant u k data from monitored sites for determining the three limit angles variation with the dip of seam are discussed the trend of the limit angle from the north of england to the midland coalfields is also discussed in the paper it has been found that the results from the data are in good agreement with numerical model results

characteristics and formation mechanisms of the unconformity related paleokarst reservoirs in the upper sinian northwestern tarim basin china abstract in the late sinian the tarim basin experienced regional tectonic uplift and subaerial exposure a regional unconformity was extensively distributed during the succession from the sinian to cambrian as a result a large number of secondary pores were developed in the upper sinian qegebulake formation an integrated study based on petrographical and petrophysical analysis geochemistry karstology and fluid inclusions was performed to provide insight into the characteristics and formation mechanism of the upper sinian carbonate reservoirs the reservoir rocks mainly include microbial dolomite crystalline dolomite and breccias reservoir matrix porosity and permeability range from 0 30 to 11 06 and from 0 00156 md to 1 49 md respectively geological and geochemical characteristics suggest that three phases of dissolution were determined to be responsible for the development of the reservoirs within about 70 m beneath the unconformity they are meteoric dissolution during subaerial exposure and deep seated hydrothermal dissolution and organic acid dissolution during the burial stage the upper sinian dolomite underwent strong meteoric dissolution which is supported by the appearance of the unconformity and the associated caves the geochemical characteristics of the cave filling calcite further indicate the diagenetic overprint from meteoric water including the relatively negative values of 18o 18 46 to 8 5 vpdb and wide range of 13c 8 11 to 0 24 vpdb low ree 1 77 4 23 ppm and yb la and yb ca variation the occurrence of saddle dolomite as well as analytical results such as 13c 0 67 2 52 vpdb and 18o 13 21 to 9 81 vpdb isotope signature and high homogenization temperature of fluid inclusions in quartz 87 2 to 220 c and saddle dolomite 82 3 135 4 c suggest that the reservoirs rocks experienced interaction with hydrothermal fluids only bitumen occurred in the edge of secondary pores formed by dissolution of quartz and saddle dolomite which suggests that organic acid dissolution likely occurred during the evolution of reservoirs a geological model for the evolution of the paleokarst reservoirs is proposed through the analysis of major reservoir controlling factors the primary pore types and reservoir petrophysical property of the qigebulake formation mainly depend on the sedimentation supergene karstification is the most important process for reservoir formation deep seated hydrothermal activity has both positive and negative attribution on the formation of reservoirs organic acid dissolution plays an active role in the formation and preservation of reservoirs this study provides a useful reference for hydrocarbon exploration in the deep buried sinian carbonate reservoirs

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

diagenetic uptake of rare earth elements by bioapatite with an example from lower triassic conodonts of south china abstract the distribution patterns of rare earth elements rees are frequently used as proxies for ancient seawater chemistry or paleomarine environmental conditions however recent work has shown that diagenesis can lead to remobilization and inter elemental fractionation of rees and that these effects often occur in conjunction with redox reactions in sediment porewaters here we review existing literature on the diagenetic fluxes of rees in marine sediments and porewaters in order to systematize existing knowledge on this subject rees undergo significant redistribution among sediment phases during both early and late diagenesis as a consequence of adsorption and desorption processes remobilization of rees commonly leads to inter elemental fractionation variously leading to enrichment or depletion of the light middle or heavy ree fractions further ree remobilization can be facilitated by redox changes e g through reductive dissolution of host phases in suboxic and anoxic porewaters characteristic ree distribution patterns develop through these processes 1 a flat distribution signifying predominantly terrigenous siliciclastic influence 2 a middle ree bulge probably due to adsorption of light and heavy rees to mn and fe oxyhydroxides respectively and 3 heavy ree enrichment indicative of hydrogenous seawater influence note all patterns in this paper are normalized to the ree composition of average upper continental crust or ucc in the second part of this study we undertake an analysis of the ree distributions in conodonts and whole rock samples from west pingdingshan a permian triassic boundary section in south china using ree th and y ho ratios we show that almost all of the conodont samples have a strong diagenetic overprint and that the hydrogenous ree fraction is small and not isolatable furthermore the conodonts contain two diagenetic ree components one characterized by low ree 100 300 ppm high ree th ratios 1000 strong middle ree enrichment and eu eu ratios of 1 5 2 0 and the second by high ree 300 2000 ppm low ree th ratios 20 30 little or no middle ree enrichment and eu eu ratios of 1 0 the first component exhibits a pronounced middle ree bulge that represents an early diagenetic signature associated with suboxic conditions possibly related to adsorption of rees onto fe mn oxyhydroxides in the shallow subsurface environment the second component shows a flat ree distribution that is similar to both our whole rock samples and average ucc indicating derivation from rees released from detrital siliciclastics e g clay minerals probably at a range of burial depths from shallow to deep failure of the conodont samples to yield an isolatable hydrogenous component demonstrates that bioapatite does not always preserve a primary marine ree signature given that bioapatite rees have been widely used for this purpose often on the assumption of minimal or no diagenetic influence our findings are likely to necessitate a re evaluation of the results of many earlier studies in general we counsel caution in inferring a hydrogenous origin for rees in bioapatite owing to frequent diagenetic alteration of ree distributions

influence of underground mining activities on the slope deformation genesis doubrava vrchovec doubrava ujala and staric case studies from czech republic abstract one the most important manifestation of underground mining activities is its potential influence on the initiation and reactivation of the slope movements however an adequate attention has not yet been paid to these problems the goal of this study is to analyze the possible influence of present and former mining activities on the selected set of model slope deformations in the ostrava karvina coalfield and also to describe a methodology for their observation for the application to similar conditions and influence three different methodologies applied in three different case studies of slope deformations where the subsidences are still active in the first case study doubrava vrchovec inclinometer was not used in the second doubrava ujala case study only one inclinometer was installed in landslide body and in the third case study sta ic two inclinometers were installed as one of them was inside of the landslide body while the other inclinometer was outside for evaluation of the impact isocatabase maps terrain deformation parameters calculated for the point lying on the slope deformation surface length measurement by zone extensometer and dilatometer measurement in cracks was also provided in order to show that inclination of both boreholes is an evidence of underground mining impact localization of inclinometer measurement on boreholes in the active part as well as in the near vicinity was found as very important thus the study contributed to a more objective knowledge of these problems of interest for the professional public and also for the state administration to solve problems associated with the utilization and settlement of such affected areas

antarctic climate southern ocean circulation patterns and deep water formation during the eocene we assess early to middle eocene seawater neodymium nd isotope records from seven southern ocean deep sea drill sites to evaluate the role of southern ocean circulation in long term cenozoic climate change our study sites are strategically located on either side of the tasman gateway and are positioned at a range of shallow 500 m to intermediate deep 1000 2500 m paleowater depths unradiogenic seawater nd isotopic compositions reconstructed from fish teeth at intermediate deep indian ocean pelagic sites ocean drilling program odp sites 738 and 757 and deep sea drilling project dsdp site 264 indicate a dominant southern ocean sourced contribution to regional deep waters end t 9 3 1 5 iodp site u1356 off the coast of adelie land a locus of modern day antarctic bottom water production is identified as a site of persistent deep water formation from the early eocene to the oligocene east of the tasman gateway an additional local source of intermediate deep water formation is inferred at odp site 277 in the sw pacific ocean end t 8 7 1 5 antarctic proximal shelf sites odp site 1171 and site u1356 reveal a pronounced erosional event between 49 and 48 ma manifested by 2 end unit negative excursions in seawater chemistry toward the composition of bulk sediments at these sites this erosional event coincides with the termination of peak global warmth following the early eocene climatic optimum and is associated with documented cooling across the study region and increased export of antarctic deep waters highlighting the complexity and importance of southern ocean circulation in the greenhouse climate of the eocene

rare earth element composition of paleogene vertebrate fossils from toadstool geologic park nebraska usa fossil bones and teeth from terrestrial environments encode unique rare earth and trace element ree and te signatures as a function of redox conditions ph concentrations of complexing ligands and water colloid interactions this signature is set early in the fossilization process and serves as a paleoenvironmental and paleoclimatic proxy these signatures can also be used to interpret temporal and spatial averaging within vertebrate accumulations and can help relocate displaced fossil bones back into stratigraphic context rare earth elements in vertebrate fossils from upper eocene and oligocene strata of toadstool geologic park northwestern nebraska record mixing and evolution of paleogene vadose or groundwaters and variations in paleoenvironments ree signatures indicate that hree enriched alkaline groundwater reacted with lree and mree enriched sediments to produce 3 component mixtures ree signatures become increasingly lree and mree enriched toward the top of the studied section as the paleoenvironment became cooler and drier suggesting that ree signatures may be climate proxies time series analysis suggests that ree ratios are influenced by cycles of ca 1050 800 570 440 and 225 ka similar to some previously determined milankovitch astronomical and climate periodicities

rare earth elements in old biogenic apatites abstract the ree distributions in individual upper devonian conodonts have been measured by ion probe the patterns of all analyzed conodonts are enriched in middle ree eu gd and have a weak or no ce anomaly concentrations and la yb or la sm ratios vary very little within or among individuals from the same zone which suggests that uptake of labile ree from sediments was essentially quantitative therefore the ree signature of the primary carriers probably organic and oxyhydroxides particulates from marine suspensions was efficiently transferred to biogenic apatites and survived late diagenetic processes ree patterns of conodonts do not resemble those of present day seawater and post cretaceous biogenic phosphates which are typically depleted in nd and sm with a negative ce anomaly since ree distributions in the modern water column mimic those of nutrients we assume that in pre cretaceous seawater they were not controlled by surface biological activity we assume instead that ree in pre cretaceous seawater can be explained by mechanism of desorption adsorption on particle surfaces progressive extraction of lree from river water by oxyhydroxides leads to precipitates enriched in middle ree a simple quantitative model was calculated in order to illustrate the proposed mechanism

trace elements and sr and c isotopic signatures in late neoproterozoic and earliest cambrian sedimentary organic matter from siliciclastic successions in the east european platform sedimentary organic matter deriving from tubes of sabelliditids vendotaenids sapropelic films and kerogens was extracted by acid processing from upper vendian siliciclastic successions in the east european platform elemental composition obtained by ins

ree and nd isotope stratigraphy of a late jurassic carbonate platform eastern paris basin france abstract rare earth elements ree and nd isotopes on the labile fraction of the callovian oxfordian to tithonian jurassic carbonate platform of the eastern paris basin were used to reconstruct the composition of the contemporaneous waters from which the labile fraction may have originated this sedimentary record shows a remarkable change in the manganese content between the clayey deposits at the top and bottom of the succession and the carbonate platform deposits the combined analyses of ree and nd isotope ratios record the influence of emerged land and the tethys ocean the ree patterns are similar to those of seawater in the middle part of the sedimentary record suggesting ree removal by marine carbonate while bell shaped ree patterns are observed above and below reflecting continent derived ree carried by fe mn coatings on detrital particles therefore the ree patterns and their evolution through the sedimentary record highlight the roles played in the ree budget by fe mn coatings on detrital particles and by marine carbonates the predominant sources of nd during platform evolution are characterized by the nd isotope variations in the sediments the nonradiogenic values end t between 12 and 10 strongly suggest that the predominant source of nd on the platform was the continental crust through weathering and river inputs whereas some more radiogenic nd end t 5 values are more typical of the tethys seawater signature

fecal pellet flux to modern bottom sediment of santa barbara basin california based on sediment trapping fecal pellets constituted more than 60 of the material collected during 45 days of deployment of a suitcase type sediment trap in santa barbara basin the flux was 660 g m 2 yr 1 of which 22 g m 2 yr 1 was carbon flux pellet transport can account for about one half of the sediment flux to the central basin floor including the supply of terrigenous matter the clearing activities of pellet producing plankton have important implications for sedimentation and fertility in the coastal ocean

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

extinction and migration in silurian trilobites and conodonts of northwestern canada appearances and disappearances lineage turnover of trilobite and conodont evolutionary species clades in silurian shelf marginal sections of the mackenzie mountains are concentrated at particular stratigraphical levels a depth energy curve generated for this region shows three major and several minor transgressive regressive cycles in the llandovery and wenlock series a comparison of this curve with conodont and trilobite distributional data supports the thesis that there are cause effect relationships between changes in sea level and migration evolution and extinction events of these marine organisms the rate amount and direction of change in depth were important factors in the migration and extinction of clades the depth energy curve for the region fits the pattern expected for a passive downdropping shelf responding to global eustatic sea level changes emigrations and extinctions are associated with rapid transgressive episodes and concentrated at three levels lower llandovery lower wenlock and middle or lower part of the upper wenlock the early wenlock event was the most impressive a further concentration of extinctions and or migrations not considered here occurred later in the ludlow associated with a regional regression phyletic evolution is most convincingly demonstrated in fossil collections from intervals of gradual regression a model is proposed that predicts that a similar pattern of extinctions occurred around the silurian world in regions of similar palaeotectonic regime and that global extinction patterns of clades between episodes of mass extinction were not random episodes of high extinction turnover pulses were caused by perturbations of the environment foremost of which were rapid changes in the depth of the seas on the continental shelves because taxonomic loss during these extinction emigration episodes was generally at low below generic levels resolution of silurian turnover patterns requires data collected at the evolutionary species level

slope stability under the influence of ground subsidence due to longwall mining abstract in many cases it has been reported that surface subsidence especially horizontal displacements induced by underground longwall mining in hilly regions is different from that in level areas however to date the mechanisms behind the phenomenon are not clear here this problem is considered to be a slope stability problem and a mathematical model is proposed to assess the slope stability under the influence of subsidence due to longwall mining in developing the mathematical model the following assumptions are made 1 the incremental subsidence and the horizontal displacement which are the amounts of subsidence and horizontal displacement other than those expected for a flat surface are the results of the sliding between the top soil and the bedrock the triggering force which causes the top soil to slide is the stress field in the top soil induced during the ground subsidence process 2 the displacement and deformation of the bedrock could be accurately predicted by the probability function integration method assuming a level surface 3 the strain in the top soil induced by the subsidence is sufficiently small such that the top soil can be treated as a linearly elastic material 4 the longwall panel is rectangular shaped in plane view

contrasting sulfur geochemistry and fe al and mo al ratios across the last oxic to anoxic transition in the cariaco basin venezuela an abrupt transition from oxic to anoxic sulfidic euxinic marine bottom waters occurred in the cariaco basin in response to increasing productivity resulting from the late pleistocene post glacial rise in sea level and corresponding increase in surface water nutrient availability the microlaminated sediments of the euxinic interval which span the last f14 5 ky suggest a predominance of water column syngenetic pyrite formation based on 1 high pyrite sulfur spy concentrations in the surficial sediment layers 2 values for degree of pyritization dop that generally do not increase appreciably with increasing burial 3 ratios of total iron fet to al that are elevated above the continental baseline recorded in the underlying oxic sediments and 4 spy isotope trends that largely mimic the d 34 shsof the modern water column intermediate dop values in the microlaminated deposits and fet al ratios that are slightly above continental levels indicate an iron reservoir controlled by scavenging during syngenetic pyrite formation in combination with intermediate rates of fe bearing siliciclastic accumulation as predicted from the relative rates of siliciclastic delivery fet al and dop data lie between end member values observed in the modern black sea as viewed broadly fet al and dop relationships in euxinic sediments reflect the balance between syngenetic fe scavenging and temporal and spatial gradients in siliciclastic input pyrite concentrations are generally low in the underlying oxic marine deposits because of limitations in the supply of organic carbon corg however the upper 80 cm of the fe rich corg poor bioturbated sediment show evidence for a strong diffusional hsoverprint from the overlying fe limited euxinic marine environment this post glacial transition manifests in pyrite overprints that are strongly 34 s depleted relative to those in restricted presently euxinic marine settings elsewhere in the world such as the black sea where the sedimentary sequence spanning the last glacial interglacial transition begins with a shift from freshwater to corg poor oxic marine deposition and thus dominantly sulfate diffusion trends for mo al ratios in the microlaminated sediments suggest that mo is enriched by roughly two orders of magnitude above the continental levels recorded in the oxic deposits organic matter plays a role by enhancing hsproduction and or by providing a substrate for mo scavenging significant mo enrichment via diffusion into the upper portion of the bioturbated zone was not observed despite hs rich pore waters as recorded in the heavy iron sulfide overprint we have

organic matter accumulation of the lacustrine lunpola oil shale central tibetan plateau controlled by the paleoclimate provenance and drainage system abstract the cenozoic lacustrine lunpola oil shale located in the central tibetan plateau has received little research interest in its depositional history although it is estimated to be a huge resource reserve this study investigates the palaeoclimate provenance and regional drainage system of the ancient lakes using a combined analysis of element geochemistry and stratigraphy to elucidate the depositional history of the lunpola oil shale most of the samples in the lower part of the section have chemical index of alteration cia values between 65 and 75 reflecting a moderate weathered source while samples in the upper part the section have cia values between 60 and 65 which indicate relatively weak chemical weathering in the source area this stratigraphic grouping suggests a paleoclimate transition from a relatively warm or humid period to a cold or dry period the zr sc and th sc ratios of the samples reveal that sorting and recycling were minor during deposition of the oil shale the geochemical results al2o3 cao na2o k2o a cn k diagrams high contents of th plots of co th la sc and cr th sc th demonstrate that the sedimentary sources were felsic rocks plots of la th sc th sc zr 10 th co zr 10 and ti zr versus la sc illustrate that the source rocks were from continental arc and active continental margin the baingoin batholiths to the south of the lunpola basin consisting mainly of cretaceous granodiorite and adamellite are likely responsible for supplying materials to the lunpola oil shale similar special ree patterns further suggest the affiliation of the oil shale with the batholiths provenance analyses indicate a main river from the south moreover stratigraphic study confirms an upstream ancient baingoin lake between the source area and the ancient lunpola lake in this drainage system paleoclimate clearly restricted the development of rivers around the lakes although terrestrial organic matter higher plants dominated the drainage area the main river originating from the south could only bring a certain amount of them to the lakes moreover considering the filtration of the upstream ancient baingoin lake minor terrestrial organic matter could be carried and deposited in the ancient lunpola lake therefore lacustrine algae could proliferate as the main organic source and preserve in the stratified hypersaline lake to form the largest oil shale resource in tibet

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

estimation of limit angle using laminated displacement discontinuity analysis in the soma coal field western turkey determination of the limit angle at the manisa soma eynez coal field a major coal production area in turkey is difficult because of the presence of a landslide caused by the waste from a neighboring open pit site being dumped over the underground mine at the soma eynez basin in fact it is not possible to determine the effect of extraction on the surface from field studies thus in order to determine the limit angle in situ subsidence measurements geophysical measurements rock based tests in the laboratory and the data obtained from a physical model have supported numerical modeling studies the software lamodel used for the numerical modeling was developed by national institute for occupational safety and health niosh and is based on the boundary element method the results obtained from modeling have been found to be compatible with other studies and as a result the limit angle has been determined

origin of dolomites in the lower cambrian xiaoerbulak formation in the tarim basin nw china implications for porosity development abstract dolomites occur pervasively in the cambrian strata in the tarim basin nw china although the cambrian strata have been deeply buried and affected by multiple phases of dolomitization some intervals in the upper part of the lower cambrian xiaoerbulak formation developed high porosity the goal of this study is to understand the origin of different types of dolomites and the formation mechanism of the porosity in the xiaoerbulak formation the geochemistry of matrix dolomites suggests that they formed from middle rare earth element mree enriched anoxic pore fluids close to or within the zone of iron reduction the similar ree y patterns and overlapping 13 c values between pore filling and matrix dolomites indicate that the fluids that were responsible for the precipitation of pore filling dolomite apparently inherited the signatures of the formation waters that were stored in the host strata low 18 o values coupled with high ba zn and rare earth element ree content of pore filling dolomites indicate that pore filling dolomites were formed at elevated temperatures the precipitation of authigenic quartz and saddle dolomites and high mn content in pore filling dolomites indicate that hydrothermal fluids that mostly originated from cambrian basinal clastic units or basement rocks were involved the mixture of formation water and external hydrothermal fluids is the most likely explanation for the formation of significant porosity and precipitation of pore filling dolomites at depth breccia dolomite zebra dolomite and saddle dolomite occur mostly in areas that are close to faults which suggests that hydrothermal fluids passed through strike slip faults in this area when these faults were activated the development of permeable layers in the upper part of the xiaoerbulak formation overlain by impermeable layers of the wusongger formation suggests a possible potential diagenetic trap when the faults were activated high pressure and high temperature fluids flowed up through faults and hit low permeability beds at the base of the wusongger formation then the hydrothermal fluids flowed laterally into permeable dolomite strata at the top of the xiaoerbulak formation and encountered the formation brines large volumes of secondary porosity formed when host dolomite was leached by the mixing fluids and pore filling dolomites and other minerals formed soon afterward both the faults and original host facies exerted important influences on the lateral extent of the dissolution

oxygen isotope variations in phosphate of biogenic apatites iii conodonts abstract the method for measurement of the isotopic composition of oxygen in phosphates has been improved and adapted for analysis of small quantities of apatite down to 10 mg this extension enables one to analyze hand picked conodont samples with an analytical reproducibility better than 0 5 1 46 samples of conodonts ranging from the ordovician to the pennsylvanian of north america were analysed some insoluble phosphatic residues ichthyoliths and inarticulate brachiopods of the same time range were also measured the range of the 18o values of the analysed conodonts is between 15 and 19 it shows a general trend of decreasing d18o with increasing age from an average value of about 19 in the pennsylvanian to 17 in the ordovician this trend parallels that previously detected in marine phosphorites for the time range between the devonian and pennsylvanian our data are in agreement with independent paleoclimatic information specifically we detect maximum18o enrichment at the end of the pennsylvanian and minimum enrichment at the end of the devonian the difference between these two extremes is equivalent to about 10 c from about 40 to 30 c assuming constant isotopic composition of ocean water the success of oxygen isotopic analysis of conodonts raises the possibility of their use in paleozoic paleo oceanography in a similar way to foraminifera in the mesozoic cenozoic

substrate control on formation and maturation of glauconites in the middle eocene harudi formation western kutch india formation and maturation of glauconites within the early middle eocene harudi formation built up in a lagoon to shelf transition in western kutch india is addressed taking recourse to a combined sedimentological micropalaeontological and mineralogical investigation the glauconite is authigenic and its occurrence coincides with maximum flooding the glauconite is more matured within the fecal pellets and is less matured within the intra particle pores of bioclasts namely foraminifera ostracoda gastropoda and bryozoa sem eds xrd and geochemical studies clearly document that the infilling within the intra particle pores of bioclasts belong to nascent to slightly evolved glauconite 5 wt k2o while the pellet belongs to slightly evolved to evolved glauconite 5 7 wt k2o based on chemical characteristics and sem investigations the glauconitization process can be best explained by the verdissement theory the glauconite possibly formed as initial authigenic glauconitic smectite precipitates while the pellet matured subsequently by addition of k the process was hindered in case of infillings the maturation process also involved addition of si and release of al with or without release of mg the glauconite maturation was facilitated in case of fecal pellets because of higher porosity inter granular nature of pores and availability of necessary elements in semi confined micro environments in contrast the maturation was aborted at an early stage in case of infillings because of the minute closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests a low negative cerium anomaly suggests glauconite formation in sub oxic micro environments created by decay of organic matters within the fecal pellets and bioclasts a clear case of substratum control on glauconitization becomes apparent

rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments abstract analyses have been made of ree contents of a well characterized suite of deep sea 4000 m principally todorokite bearing ferromanganese nodules and associated sediments from the pacific ocean ree in nodules and their sediments are closely related nodules with the largest positive ce anomalies are found on sediments with the smallest negative ce anomalies in contrast nodules with the highest contents of other rare earths 3 ree are found on sediments with the lowest 3 ree contents and vice versa 143 nd 144 nd ratios in the nodules 0 51244 point to an original seawater source but an identical ratio for sediments in combination with the ree patterns suggests that diagenetic reactions may transfer elements into the nodules analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to ree contents of nodules and sediments is negligible inter element relationships and leaching tests suggest that ree contents are controlled by a p rich phase with a ree pattern similar to that for biogenous apatite and an fe rich phase with a pattern the mirror image of that for sea water it is proposed that 3 ree concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate processes which favour the enrichment of transition metals in equatorial pacific nodules favour the depletion of 3 ree in nodules and enrichment of 3 ree in associated sediments in contrast ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions

rare earth major and trace elements in chert from the franciscan complex and monterey group california assessing ree sources to fine grained marine sediments abstract rare earth element ree major and trace element analyses of 77 samples from the mesozoic franciscan complex and miocene monterey group of california usa indicate that magnitudes of the ce anomaly ce ce and total ree abundances sree in these rocks are controlled dominantly by a the amount of included metalliferous material b the amount of direct terrigenous input and c the overall burial rate the relative importance of these individual processes varies across an ocean basin in such a way that ree relative fractionations and sree correspond with its depositional environment our conclusions are supported by an extensive review of published ree data from various river coastal open ocean and ridge influenced waters as well as terrigenous pelagic and metalliferous sediment the chert sequences record deposition in spreading ridge open ocean basin and continental margin environments the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample s inferred depositional distance km from the spreading ridge the major element chemistry and the stratigraphie context the ce ce values are low 0 29 in the vicinity of spreading ridges and trend to successively higher 1 values with decreasing metalliferous and increasing terrigenous influences other ree indicators ree lu n la n eu eu also respond to metalliferous and terrigenous influences near the spreading ridge chert ree appears determined by burial rate while shale ree responds to metalliferous abundance in open ocean and continental margin environments ree is controlled by sediment exposure time and therefore is related inversely to burial rate ree data are consistent with the major elements fe2o3 mno and al2o3 in reflecting the respective metalliferous and terrigenous sources p2o5 and cao do not vary with ce ce in any environment but cao shows a weak negative correlation with ree trace element trends e g v cr cu ge si rb sr y th u in general can similarly be accounted for in the context of depositional position relative to metalliferous and terrigenous inputs rees in chert appear less affected by post depositional processes than either major or trace elements indicating that rees are better tools for paleoceanographic or tectonic reconstructions that are based on chert chemistry this work complements recent efforts to elucidate the factors determining large scale ree distributions in marine sediments and has direct bearing on previous attempts to use the ce anomaly in older rocks and sediments as a recorder of secular variations and anoxic events in the overlying water column

trace and rare earth element geochemistry of phosphate nodules from the lower cambrian black shale sequence in the mufu mountain of nanjing jiangsu province china abstract phosphate nodules are abundant in the lowermost section of the lower cambrian black shale sequence along a ne trend belt in the yangtze platform south china in this study we examined the neoproterozoic cambrian mufu mountain section near nanjing of jiangsu province and conducted a detailed trace and rare earth element ree study on the phosphate nodules we employed a step leaching acid dissolution protocol of 1 m hac and 1 m hcl respectively to separate carbonate from phosphate mineral contributions in the nodules both the hac leached and hcl leached fractions of the phosphate nodules show similar symmetrical variations in trace and ree concentrations and ratios the total rees and a number of redox sensitive trace metals such as v cr mo ni abundances show a systematic increase from the core to rim whereas the u and mn abundances decrease from the core to rim in most of the nodules similar trends are also observed for the rb sr u th co ni and v ni ratios but these trends in the hac leached fractions are less pronounced than the hcl leached fractions all of the hcl leached fractions for the nodule cores show seawater like shale normalized ree patterns but the rims of the nodules display slightly mree enriched and hree depleted patterns we suggest that the phosphate nodules may have formed in a basinal setting beneath a stratified water column during early cambrian and the compositional variations of rees and redox sensitive trace elements from the core to rim may record a changing redox condition and fluid mixing during different stages of nodule growth the cores of the nodules preserve more pronounced negative ce anomalies and progressively hree enriched patterns which may retain primary early cambrian seawater chemistry whereas the nodule rims record chemistry consistent with changed redox conditions and or influences from pore fluids such as generated from degradation of organic matter

sm nd in marine carbonates and phosphates implications for nd isotopes in seawater and crustal ages this study explores the possibility of establishing nd isotopic variations in seawater over geologic time calcite aragonite and apatite are examined as possible phases recording seawater values of nd modern biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have nd concentrations of from 0 2 to 70 ppb showing that primary marine caco 3 contains little ree and that nd ca is not greatly enhanced relative to seawater during carbonate precipitation very young marine limestone and dolomite containing no continental detritus have 200 ppb nd all the carbonates are lree enriched 0 16 sm nd 0 45 modern and very young atlantic and pacific carbonates have nd in the range of shallow atlantic and pacific seawater respectively implying that they derive their ree from local seawater the nd in well preserved carbonate fossils is 4 10 4 ppb much greater than in their modern counterparts but like the high values found for carbonates in other studies we believe the high ree contents at the 500 ppb level in some detritusfree carbonates are due to ree rich fe hydroxide in on the carbonate in favorable cases such material may record seawater nd values however introduction of extraneous ree may obscure the original isotopic composition of pure caco 3 because of its very low intrinsic primary ree abundance modern biogenic apatite is also shown to have very low ree content 150 ppb nd but appears to quickly scavenge ree from seawater inorganically precipitated apatite from phosphorites has high concentrations of seawater derived ree young phosphorite apatite from the atlantic and pacific oceans has nd in the range of the seawater from these oceans older apatite samples of similar age from different localities bordering common oceans record similar values of nd t sedimentary apatite has sr t values in good agreement with the curves for 87 sr 86 sr of seawater as a function of time individual conodonts from a single formation yield the same sr t and nd t other workers have shown that sedimentary apatite preserves seawater ree patterns these characteristics suggest that sedimentary apatite can be used to determine nd t in ancient seawater the seawater values so inferred range between 1 7 and 8 9 over the last 700 my and lie in the range of modern seawater showing no evidence for drastic changes high values of seawater nd t in the triassic and latest precambrian may correlate with the breakup of large continental landmasses the initial nd t 15 0 of a 2 ae old phosphorite implies the presence of 1 5 ae old continental crust at 2 ae ago the approach outlined here can be used to constrain the age of the exposed crust as a function of time

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

the permian triassic boundary in western slovenia idrijca valley section magnetostratigraphy stable isotopes and elemental variations stable isotope analyses of carbonate 13ccarb and total organic carbon toc 13corg together with geochemical analyses of 54 major minor and trace elements and magnetic susceptibility measurements were carried out on whole rock samples of the undisturbed permian triassic p tr limestone boundary sequence in the idrijca valley w slovenia at the p tr boundary there is a 0 8 cm thick clayey marl layer ptb showing a characteristic magnetic susceptibility pulse and considerable enrichment in most major minor and trace elements the p tr transition is characterized by 1 an abrupt decrease in sedimentation rate from 32 to 5 cm 100 ka 2 a well known prominent negative excursion of 13ccarb and 13corg reflecting global perturbations in the carbon cycle and 3 the drastic disappearance of typically upper permian marine fauna although the shape of the 13ccarb curve indicates gradual long term change across the p tr boundary the sharp negative 13corg anomaly within an interval from 30 cm below to 6 cm above the boundary suggests an interruption of those gradual processes our observations for selected redox sensitive elements mo u v and zn abundances for organic carbon and sulphur and the rare earth elements ree distribution in the boundary sequence as well as the shape of the ce ce curve suggest that oceanic anoxia was typical of the upper permian and that the transition to oxygenated conditions occurred at the p tr boundary oxygenation at the p tr transition is coincidental with the terminal phase of the upper permian marine regression the shape of the ce ce curve indicates that the redox environmental conditions changed again in the earliest triassic resulting once more in oxygen deficient conditions

non hydrothermal origin of apatite in sedex mineralization and host rocks of the howard s pass district yukon canada the howard s pass district hpd comprises 14 zn pb sedimentary exhalative sedex deposits and is located within the selwyn basin yukon canada although the hpd is renowned for its large accumulation of base metal sulfides in places the late ordovician to early silurian host rocks also contain abundant carbonate bearing fluorapatite cbfa this mineral is present stratigraphically be low within and above the sedex deposits and occurs as fine grained layers that are interbedded with cherty carbonaceous mudstone electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometric analysis reveal that mineral compositions and rare earth element yttrium ree y systematics respectively are remarkably similar throughout the stratigraphic succession north american shale composite nasc normalized la sm and la yb ratios indicate that the original ree compositions in cbfa have undergone only minor compositional modification subsequent to deposition uniformly negative ce anomalies indicate that the mineral formed in analogous manner to modern and ancient sedimentary phosphorites under suboxic bottom water conditions europium anomalies are mostly absent indicating that reduced slightly acidic high temperature hydrothermal fluids were not a major source of ree y to cbfa the chemical homogeneity of the mineral irrespective of its stratigraphic position indicates that a common process was responsible for its deposition within the sedimentary rocks of the hpd on the basis of the similarity of the ree patterns to modern and ancient phosphorites and the absence of positive eu anomalies we conclude that the cbfa is of hydrogenous origin and not hydrothermal as suggested by previous workers as such phosphorite formation in the hpd is casually related to sedex zn pb deposit formation