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

relationships between sulphur organic carbon and iron in the modern sediments of the black sea abstract the ratio of sedimentary s to organic c has been used as a diagnostic criterion for recognizing anoxic environments in the sedimentary record here we examine the relationship between pyrite s and organic c in the modern unit 1 sediments of the black sea to re evaluate this suggested relationship in box cores from shallow oxic or near oxic water pyrite s contents ranging from 0 1 and 2 5 by weight do not correlate with organic c contents in cores from the deep anoxic basin pyrite s concentrations range between 1 0 and 2 5 and are linearly related to organic c contents with an intercept that is not significantly different from zero the s c ratio is around 0 31 in these sediments which is somewhat lower than the ratio of 0 36 considered to be characteristic of normal marine oxic sediments thus the black sea anoxic sediments appear to be depleted in s relative to organic c the degree of pyritization dop of the sediments may be a better measure of anoxic conditions of sedimentation the dop values measured here show that pyrite formation is fe limited the correlation between organic c and pyrite s probably being induced by a positive correlation between fine grained sediment components the original fe source for pyrite formation in the sediments and organic matter such fe limitation is probably characteristic of anoxic basins where pyrite formation can take place in the water column and fe oxyhydroxides do not accumulate in the surface sediments the results on the sample set examined here are at variance with earlier data and interpretations for the black sea in particular the suggested s enrichment of anoxic black sea sediments was not found because of fe limitation

origin of interstitial water compositions in postglacial black clays northeastern sweden abstract the distribution of the major elements cl na ca 2 mg 2 and k in postglacial black clays is caused by diffusion of these elements to the surface during the 300 yr the sediments have been above sea level the diffusion model gives whole sediment diffusion coefficients of 5 10 6 cm 2 s 1 for the monovalent ions and 3 10 6 cm 2 s 1 for the divalent ions the model suggests that the water at depth in the core approximates in major element composition to water trapped in the sediment during deposition 7000 yr ago the computed paleosalinity value of 13 is similar to values of 12 14 derived indirectly from paleoecological studies the results suggest that it is possible to obtain quantitative information about the chemical composition of postglacial aqueous systems from similar chemically and mechanically undisturbed systems using diffusion models

anomalous accumulation of acid volatile sulphides avs in a coastal marine sediment saguenay fjord canada sulpha te reduction usually leads to the formation and accumulation of authigenic pyrite fes2 in organic rich coastal marine sediments iron monosulphides fesx are most often found as a minor constituent of the reduced sulphur pool in these sediments and are believed to be precursor phases which convert to pyrite during early diagenesis abnormally high ratios of acid volatile sulphides avs to pyrite however are found in the sediments of the saguenay fjord canada the avs s fes2 s ratio observed throughout the anoxic zone in three sediment cores collected along the main axis of the fjord generally exceeds 1 and reaches values as high as 7 at the head of the fjord to document and explain this anomaly solid phase components avs fes2 s reactive iron feno coro and total n as well as porewater constituents so4 fe and mn were analyzed degree of pyritization dop values were low 0 1 11 and generally decreased toward the mouth of the fjord in contrast degree of sulphidization dos esti mates were high and reached values of up to 43 at the head of the fjord these latter values indicate that pyrite formation is not limited by iron availability but a large excess of reactive iron may in fact inhibit the build up of reduced sulphur zh2s in the porewaters as a result of avs s precipitation in the absence of a strong eh2s gradient slow diffusion to the redox boundary and limited formation of soluble inter mediate reduced sulphur species may hinder the conversion of avs to pyrite

sulfur geochemical constraints on mesoproterozoic restricted marine deposition lower belt supergroup northwestern united states abstract despite nearly a century of study by a diverse group of precambrian workers competing interpretations have persisted that favor both marine and nonmarine depositional settings for the mesoproterozoic belt supergroup of the northwestern united states our data for sedimentary pyrite formation in unmetamorphosed organic rich shales of the newland formation of the lower belt supergroup western montana argue that at least a portion of the belt basin during its early history was characterized by restricted marine conditions with only episodic incursions of seawater this model is supported by ratios of organic carbon corg to pyrite sulfur that once corrected for selective diagenetic and thermal loss of corg and the inferred high reactivity of the corg reservoir in the absence of vascular land plant remains suggest degrees of sulfate limitation consistent with a restricted marine setting the isotopically heavy disseminated pyrite that dominates the black shales shows a broad range of 34s values of bacterial origin 34s ranges from 8 7 to 36 3 mean 7 6 n 41 the pyrite data overlap with the 34s range of coeval barite sulfate within the basin and are similar to independent estimates for the sulfate of mesoproterozoic seawater these relationships have allowed us to delineate a record of bacteriogenic pyrite that formed in a modified marine reservoir where the supply of sulfate was limited a bacterial mechanism is further suggested by the morphological character of this early formed pyrite including the ubiquitous framboids after comparing our results with those from present day localities such as the black sea and sites of lacustrine deposition we conclude that the abundant 34s enriched bacteriogenic disseminated pyrite observed in black shales of the newland formation must record a style of sulfate limitation possible only within an isolated marine basin receiving an intermittent flux of seawater although the entire belt basin likely remained a restricted marine setting throughout deposition of the lower belt supergroup sulfur isotope data from the newland formation at two localities separated by more than 150 km in the eastern belt basin reveal stratigraphic trends in the strength of the marine connection specifically the connection evolved such that inputs of seawater sulfate increased progressively in frequency and possibly strength during deposition of the newland formation overall the hypothesized restricted marine setting when viewed in light of independent tectonic sedimentologic and geochronologic evidence suggests syndepositional and likely episodic continental rifting which helps constrain the proterozoic paleotectonic history of western laurentia

back analysis of an excavated slope failure in highly fractured rock mass the case study of kargar slope failure iran this paper examines the failure of kargar cut slope located at the south part of esfahan subway using analytical and numerical back analysis methods the excavated trench has 27 m depth with near vertical walls due to the space limitation around it the geology of the area comprises weathered and heavily jointed shale and sandstone overlaid by alluvium deposits despite the slope being supported by shotcrete and fully grouted rock bolts a catastrophic failure occurred at the east wall due to the uncertainty about the causes of failure initiation back analyses have been performed via both the limit equilibrium and numerical method for considering various probable mechanisms in the back analysis with limit equilibrium method the rock mass is assumed as an equivalent continuum and hoek brown failure criterion and geological strength index gsi are applied to calculate the shear strength parameters the results show that gsi value was 33 in the failed mass in the numerical back analysis the distinct element method is applied to study the contribution of rock joints to the failure and progressive rock mass strength degradation until failure the results show that threshold values of joint cohesion and friction were 0 2 mpa and 30 respectively also the modeled slip surface being step shaped agrees with the observed one

microfabric analysis of mn carbonate laminae deposition and mn sulfide formation in the gotland deep baltic sea the manganese carbonate deposits of the anoxic littorina sediments of the gotland deep have been commonly related to the periodic renewal of deep water by inflowing saline water from the north sea the use of scanning electron microscopy based techniques allows identification of small scale sedimentary and geochemical features associated with mn carbonate laminae which has significant implications for models of mn carbonate formation varves occurring in the littorina sequence contain up to four laminae that may be placed in a seasonal cycle and kutnahorite laminae occur within varves only as a winter early spring deposit this kutnahorite laminae seasonality is in agreement with the seasonal distribution of major baltic inflow events recorded in historical records and a direct causal link between inflows and kutnahorite deposition is implied benthic foraminifera tests are found to be heavily encrusted in kutnahorite implying that benthic recolonization during oxidation events occurs concurrently with kutnahorite formation the relatively common occurrence of small 50 to 100 m hexagonal mn sulfide pseudomorphs associated with 13 of kutnahorite laminae studied is reported in gotland deep sediments for the first time although mn sulfide crystals are not usually preserved in the sediment the discovery of mn sulfide pseudomorphs suggests that initial formation of mn sulfide in the gotland deep may occur much more commonly during the process of kutnahorite formation than previous reports of mn sulfide occurrence have implied

characterization of the unconventional tuscaloosa marine shale reservoir in southwestern mississippi usa insights from optical and sem petrography abstract this study presents new optical petrography and electron microscopy data interpreted in the context of previously published petrophysical geochemical and mineralogical data to further characterize the tuscaloosa marine shale tms as an unconventional reservoir in southwestern mississippi the basal high resistivity zone has a higher proportion of type ii sedimentary organic matter than the overlying tms indicating it is more prone to oil generation optical petrography and electron microscopy reveal a heterogeneous clay matrix with ubiquitous pyrite grains quartz feldspar glaucony foraminifera shell fragments and rarer occurrences of apatite and crinoid fragments as well as liptinite alginite inertinite and vitrinite our petrographic observations suggest that higher abundances of detrital quartz grains coupled with minimal authigenic cements result in higher porosity and permeability however the tms is also more clay rich than other unconventional shale oil and gas plays which can impair the effectiveness of hydraulic fracture stimulation thin section observations reveal alternating clay and calcium carbonate laminae that are interpreted to reflect changes in sediment flux planktonic foraminifera indicate an overlying oxygenated water column while benthic inoceramid fragments and pervasive authigenic pyrite suggest anoxic or dysoxic bottom water conditions apatite fragments in thin section suggest mixing events and an influx of nutrient rich sediments overall these observations suggest that a variety of paleodepositional environments occurred in the tms and the lithofacies diversity resulting from these small scale depositional cycles makes it difficult to determinatively identify areas conducive to enhanced economic hydrocarbon recovery

methods for inferring regional surface mass anomalies from gravity recovery and climate experiment grace measurements of time variable gravity 1 the gravity recovery and climate experiment grace will deliver monthly averages of the spherical harmonic coefficients describing the earth s gravity field from which we expect to infer time variable changes in mass averaged over arbitrary regions having length scales of a few hundred kilometers and larger to accuracies of better than 1 cm of equivalent water thickness these data will be useful for examining changes in the distribution of water in the ocean in snow and ice on polar ice sheets and in continental water and snow storage we describe methods of extracting regional mass anomalies from grace gravity coefficients spatial averaging kernels were created to isolate the gravity signal of individual regions while simultaneously minimizing the effects of grace observational errors and contamination from surrounding glacial hydrological and oceanic gravity signals we then estimated the probable accuracy of averaging kernels for regions of arbitrary shape and size

manganese authigenesis in the landsort deep baltic sea abstract manganese mineralogy because of its redox sensitivity is a valuable parameter for interpreting water column anoxia and sediment diagenesis in the baltic and especially the landsort deep the relatively widespread occurrence of mn carbonates and the unique observations of authigenic mn sulphides in sedimentary environments need to be accounted for within the models proposed for mn authigenesis in diverse settings in this study stratigraphic changes in the geochemistry and mineralogy are documented in two gravity cores using petrographic microscopy xrd sem eds analyses of c and s content 13 c isotopes icp ms cation determinations and electron microprobe element profiling the lamination in the bottom sediments of the landsort deep suggests essentially continuous anoxic conditions at the sediment surface during the last ca 4500 14 c years the most striking variations in the sediments are related to the occurrence of two mn ii precipitate rich sapropel intervals recent and 1390 1990 14 c years bp sapropel deposition is associated with relatively slow detrital sedimentation allowing the concentration of organic matter the sediment c org content is influenced by the variations in the primary production as well as the supply of terrestrial c org but a major control appears to be detrital dilution the precipitation of mn carbonate as individual aggregates of spherical particles dispersed within clayey sediment matrix and as laminae with semi seasonal cyclicity is believed to be largely induced by the high alkalinity in connection with organic matter deposition and degradation where h 2 s has exceeded fe availability mns has also precipitated most commonly as well developed hexagonal crystals but also as the cubic variety alabandite which has not previously been reported from a sedimentary environment an expansion of the anoxic bottom water conditions during sapropel deposition is interpreted by correlation with laminated intervals on the slope of the deep basin budget calculations for the supply of mn to the basin during mn rich sapropel formation can be better balanced by the addition of mn from dissolution of oxides formed prior to the anoxic expansion the importance of alkalinity for the precipitation of mn carbonates and sulphides does not exclude the need for considerable mn concentrations but the model argued in several recently published studies stressing mn availability as the major control does not seem appropriate for the landsort deep and may be too restrictive in many other settings as well

late weichselian and early holocene shore displacement in the central baltic sea abstract the glacial unloading and resulting isostatic land uplift have together with hydro isostasy eustatic rise of sea level and geoidal changes ruled the shore displacement of fennoscandia within the baltic basin periods of damming and shifts of outlet further complicated the shore displacement during the period studied ca 12 2 8 4 ka bp information on the baltic history was derived from shoreline observations and studies on sediment cores from lakes formerly directly affected by the baltic these cores were analyzed with respect to pollen diatoms and lithology to determine sequences of baltic sediments and dated by a combination of radiocarbon dates and biostratigraphy the studied areas of southeastern sweden mainly central gotland and the oskarshamn area eastern smaland display a similar course of shore displacement the late weichselian period shows a regression of a slightly decreasing rate between ca 12 2 and 10 3 ka bp then followed a fast drop 25 m of the baltic s water level the final drainage of the baltic ice lake during the next ca 700 years the yoldia stage a regression of ca 17 m occurred this period is mainly characterized by freshwater diatoms in the baltic but at ca 10 ka bp there is evidence of a shortlasting 100 150 year period with brackish water the ancylus transgression of ca 11 m began ca 9 6 ka bp and culminated ca 9 3 ka bp it was followed by a fast regression of 8 10 m thereafter the rate of regression decreased shoreline gradients showed that the fastest shoreline tilting occurred around 10 ka bp thus ca 2 ka after deglaciation

biogeochemical cycling in an organic rich coastal marine basin 6 temporal and spatial variations in sulfate reduction rates rates of sulfate reduction were measured over a 3 year period in the anoxic nearshore sediments of cape lookout bight north carolina using both a tube incubation method and a 35s sulfate direct injection technique the methods yielded similar depth integrated rates over the upper 30 cm ranging from less than 10 mol so 4 m 2 y 1 in winter to greater than 50 mol so 4 m 2 y 1 in summer there were also seasonal changes in the arrhenius activation energies for the sulfate reduction rates indicating that the assumption that ea is constant with temperature is not always valid the time averaged annual turnover rate for all three years was 20 4 11 4 mol so 4 m 2 y 1 surface rates ranged seasonally from less than 0 01 to over 3 mm so 4 d 1 between winter and summer respectively a subsurface rate maximum was observed to develop during the summer months which accounted for 28 percent of the annual depth integrated sulfate reduction rate subsurface rate maxima are the result of changes in the chemistry substrate type and or concentration and the microbiology in the sediments the possibility of the subsurface maximum being an artifact of the 35s method is also discussed however the sulfate reduction rates compare well with previous measurements of the carbon sediment water plus burial fluxes and with a depth integrated co2 production rate modelled from a co2 concentration profile from the same site

authigenic sulfide and carbonate mineral formation in holocene sediments of the baltic sea formation of authigenic sulfides and carbonates in holocene 14c dated sediments is interpreted based on analyses of cations fes s fes2 s corg and sulfur isotopes mineral distribution was studied in thin sections and mineral morphology with sem eds the sediments were deposited in the gotland deep baltic sea during freshwater and brackish stages calcium rich rhodochrosite mnco3 occurs in concentrations up to 17 dw in brackish water sediments and are mainly confined to 0 02 0 5 mm thick laminae the frequency with which these laminae occur suggests that they formed with a periodicity of one to a few years and their purity suggests that formation took place in a few weeks we propose that these carbonate laminae resulted from oxic water inflow to the euxinic basin mn ii dissolved in the water column was rapidly oxidized and large amounts of mn oxides reached the sediment reduction of these mn oxides in a high alkalinity environment facilitated rhodochrosite precipitation at the sediment surface pyrite in the brackish water sediments formed at or above the sediment water interface in an iron limited environment due to alternating oxic and euxinic conditions fes was oxidized resulting in a high fes2 sfes s ratio median 170 formation of iron sulfides in the freshwater sediments occurred below the sediment water interface in a sulfate limited environment as a result of the rapid exhaustion of reactive iron in the brackish water sediments excess h2s diffused downwards to pyritize the uppermost part of the underlying freshwater sediments

oxidation and reduction of radiolabeled inorganic sulfur compounds in an estuarine sediment kysing fjord denmark 35s labeled so42 s2o32 s0 hs h2s hs s2 and fes2 were used to trace the oxidative and reductive pathways of the sulfur cycle we studied the transformation of 35so42 35s2o3 35s0 av35s h35s fe35s and fe35s2 in 8 cm long undisturbed estuarine sediment cores in time course experiments of up to 24 h all the tracers except for pyrite were oxidized and or reduced at all depths more than 60 of the 35s from 35so22 reduction was recovered as 35s0g in the top two cm of the sediment at 2 cm nearly all of the reduced 35so42 was recovered as av35s plus fe35s2 thiosulfate was not detected in the sediment from the combined data of outer and inner labeled 35s2o32 injections concurrent oxidation reduction and disproportionation of s2o32 were demonstrated in oxidized surface sediment the three processes comprised 10 24 and 66 respectively of the metabolized 35s2o32 in reduced sediment these percentages were 16 45 and 39 injections of sh35s into s2o32 spiked sediment cores produced 71 35so42 and 29 35s2o32 of the total 35so42 35s2o32 in the oxidized zone and 8 35so42 and 92 35s2o32 in the reduced zone a similar experiment with 35s0 produced 62 35so42 and 38 35s2o32 in the oxidized zone and 22 and 78 in the reduced zone we calculated that more than half of the 35s0 and h35s oxidation to so42 proceeded through s2o32 in the reduced sediment in the oxidized sediment these percentages were 15 and 21 for sh35s and 35s0 respectively thiosulfate was thus a key intermediate in the s cycle

trace metal speciation in sea and pore water of the gotland deep baltic sea 1994 abstract studies on the speciation particulate colloidal anionic and cationic forms of trace metals cd co cu fe mn mo ni pb zn in the water column and in pore waters of the gotland deep following the 1993 94 salt water inflows showed dramatic changes in the total dissolved metal concentrations and in the ratios between different metal species in the freshly re oxygenated waters below 125 m changes in concentrations were greatest for those metals for which the solubility differs with the redox state fe mn co but were also noted for those metals which form insoluble sulphides cd pb cu zn and or stable complexes with natural ligands cu pore water data from segmented surface muds 0 200 mm indicated that significant redox and related metal speciation changes took place in the surface sediments only a few weeks after the inflow of the oxygenated sea water into the gotland deep

dolomite formation in anoxic sediments of kau bay indonesia authigenic dolomite layers occur in the organic matter rich sediments of kau bay indonesia dolomite formation is related to the anaerobic decomposition of organic matter which causes depletion of pore water sulfate and increase in interstitial water alkalinity x ray diffractograms of kau bay dolomites show sharply defined peaks including the superstructure reflections carbon isotopes indicate that a significant portion of the carbon is derived from the degradation of organic matter the pore waters are highly supersaturated with dolomite but at greater depths pore waters are undersaturated or are near saturation with calcite and aragonite dolomite seems to have formed by direct precipitation from solution the formation of dolomite is believed to be initiated by the high alkalinity levels found in the zone of anoxic methane oxidation the rate of dolomite formation is controlled by the supply of calcium and is on the order of a few centimetres per 1 ka

improved methods for observing earth s time variable mass distribution with grace using spherical cap mascons we discuss several classes of improvements to gravity solutions from the gravity recovery and climate experiment grace mission these include both improvements in background geophysical models and orbital parameterization leading to the unconstrained spherical harmonic solution jpl rl05 and an alternate jpl rl05m mass concentration mascon solution benefitting from those same improvements but derived in surface spherical cap mascons the mascon basis functions allow for convenient application of a priori information derived from near global geophysical models to prevent striping in the solutions the resulting mass flux solutions are shown to suffer less from leakage errors than harmonic solutions and do not necessitate empirical filters to remove north south stripes lowering the dependence on using scale factors the global mean scale factor decreases by 0 17 to gain accurate mass estimates ocean bottom pressure obp time series derived from the mascon solutions are shown to have greater correlation with in situ data than do spherical harmonic solutions increase in correlation coefficient of 0 08 globally particularly in low latitude regions with small signal power increase in correlation coefficient of 0 35 regionally in addition to reducing the error rms with respect to the in situ data reduction of 0 37 cm globally and as much as 1 cm regionally greenland and antarctica mass balance estimates derived from the mascon solutions agree within formal uncertainties with previously published results computing basin averages for hydrology applications shows general agreement between harmonic and mascon solutions for large basins however mascon solutions typically have greater resolution for smaller spatial regions in particular when studying secular signals

a practical procedure for the back analysis of slope failures in closely jointed rock masses abstract where closely jointed rock masses are encountered in slopes failure can occur both through the rock mass as a result of combination of macro and micro jointing and through the rock substance determination of the strength of this category of rock mass is extraordinarily difficult since the size of representative specimens is too large for laboratory testing this difficulty can be overcome by using a non linear rock mass failure criterion or by back analysis of such slopes to estimate the rock mass strength in this paper a practical procedure and a computer program are presented for the back determination of shear strength parameters mobilized in slopes cut in closely jointed rock masses which obey a non linear failure criterion rather than a linear one the procedure shows that the constants to derive normal stress dependent shear strength parameters of the failed rock masses can be determined by utilizing a main cross section and without a pre determined value of rock mass rating rmr trials are made for different rmr m and rmr s values corresponding to various possible combinations of the constant m and s which are used in the hoek brown failure criterion satisfying the limit equilibrium condition it is also noted that the procedure provides a quick check for the rock mass rating obtained from the site investigations the method is used in conjunction with the bishop s method of analysis based on circular slip surfaces the procedure outlined in this paper has also been satisfactorily applied to documented slope failure case histories in three open pit mines in turkey

sediment chemistry and magnetic properties in an anomalously reducing core from the eastern mediterranean sea abstract in core kc19c 19 6 m long recovered in the abyssal plain between crete and cyprus in the eastern mediterranean a large number of organic rich layers sapropels occur which correlate to maxima in the insolation curve in contrast to other sites in the eastern mediterranean porewaters contain sulfide below a few meters below seafloor mbsf geochemical analyses were performed on the porewaters ammonium alkalinity sulfate manganese iron bisulfide chloride eh ph and sediments organic carbon barium total sulfur total iron manganese pyrite dithionite extractable iron in addition a series of magnetic parameters and ratios nrm arm irm in arm irm s ratio arm 20mt arm in were determined in the top of the sediments fe and mn hydr oxides occur at the oxic suboxic boundary just above the youngest sapropel si2 these hydr oxides appear to be more easily demagnetized by means of alternating fields than deeper hydr oxides which presumably are of detrital origin the transition from suboxic to anoxic sediments is located at 2 mbsf sulfide is produced possibly during sulfate reduction through anoxic methane oxidation at 17 5 mbsf from 17 5 mbsf sulfide migrates upward titrating reactive fe resulting in pyrite formation in the entire sediment column up to 2 mbsf at this depth the upward sulfide flux has been totally consumed by reaction with solid phase fe and dissolved fe ii diffusing downward from the suboxic zone above from 2 mbsf downward magnetic intensities are significantly reduced indicating reductive dissolution of fe oxide minerals and pyrite formation as a consequence no reliable nrm data can be obtained in the lower half of the core

stability of rock slopes in valles marineris mars 1 new slope measurements from the mars orbiter laser altimeter mola in conjunction with the rock mass rating system rmr permit inversions of slope height and angle from wallrock and interior deposits within valles marineris troughs for strength and lithology wallrock 50 rmr 65 is stronger than interior deposits 30 rmr 55 these values are consistent with layered igneous rock beneath wallrock slopes with interior deposits consistent with partially indurated sedimentary or volcaniclastic rocks larger volumes of landslide debris relative to terrestrial slides are related to the reduced martian gravity seismicity along trough bounding normal faults likely triggered the landslides in the adjacent wallrock the weaker interior deposits are located sufficiently far from a border fault and on its hangingwall to have remained stable during the seismogenic faulting in valles marineris

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

geochemistry of inorganic and organic sulphur in organic rich sediments from the peru margin abstract we have determined 1 the abundance and isotopic composition of pyrite monosulphide elemental sulphur organically bound sulphur and dissolved sulphide 2 the partition of ferric and ferrous iron 3 the organic carbon contents of sediments recovered at two sites drilled on the peru margin during leg 112 of the ocean drilling program sediments at both sites are characterised by high levels of organically bound sulphur obs obs comprises up to 50 of total sedimentary sulphur and up to 1 of bulk sediment the weight ratio of s to c in organic matter varies from 0 03 to 0 15 mean 0 10 such ratios are like those measured in lithologically similar but more deeply buried petroleum source rocks of the monterey and sisquoc formations in california the sulphur content of organic matter is not limited by the availability of porewater sulphide isotopic data suggest that sulphur is incorporated into organic matter within a metre of the sediment surface at least partly by reaction with polysulphides most inorganic sulphur occurs as pyrite pyrite formation occurred within surface sediments and was limited by the availability of reactive iron but despite highly reducing sulphidic conditions only 35 65 of the total iron was converted to sulphide 10 30 of the total iron still occurs as fe iii in surface sediments the isotopic composition of pyrite is similar to that of both iron monosulphide and dissolved sulphide either pyrite like monosulphide formed by direct reaction between dissolved sulphide and detrital iron and or the sulphur species responsible for converting fes to fes2 is isotopically similar to dissolved sulphide likely stoichiometries for the reaction between ferric iron and excess sulphide imply a maximum resulting fes2 fes ratio of 1 1 where pyrite dominates the pool of iron sulphides at least some pyrite must have formed by reaction between monosulphide and elemental sulphur and or polysulphide elemental sulphur s0 is most abundant in surface sediments and probably formed by oxidation of sulphide diffusing across the sediment water interface in surface sediments s0 is isotopically heavier than dissolved sulphide fes and fes2 and is unlikely to have been involved in the conversion of fes to fes2 polysulphides are thus implicated as the link between fes and fes2

carbon sulfur plots to show diagenetic and epigenetic sulfidation in sediments abstract organic carbon vs sulfide sulfur plots are now being used regularly by many geochemists to help understand recent and ancient depositional environments and diagenetic processes usually these plots are useful to recognize nonmarine vs marine environments or oxic vs anoxic vs euxinic depositional environments however c vs s plots can also indicate diagenetic and epigenetic events that produce excess sulfide four new examples are presented and discussed

biogeochemical cycling in an organic rich coastal marine basin 7 sulfur mass balance oxygen uptake and sulfide retention sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of cape lookout bight n c u s a over the three year study period 1981 1983 the mean annual sulfate reduction rate was determined to be 18 2 1 6 moles m 2 y 1 this value added to the estimate of the detrital sulfur input of 1 2 4 4 gave a total sulfur input of 19 4 4 7 moles m 2 y 1 the sulfide flux to the sediment water interface measured in anaerobic benthic chambers was 4 6 0 5 moles m 2 y 1 and represented 37 of the annual oxygen uptake rate of 25 2 2 8 moles m 2 y 1 the sulfide burial rate determined to be 15 5 3 1 moles m 2 y 1 was within 5 of the value predicted by summing the fluxes at the sediment water interface the cs weight ratio of sediment below the depth of diagenetic reaction was determined to be 2 75 the sulfide retention rate in these rapidly accumulating sediments 10 cm yr was 77 19 comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention

geomechanical characterisation of rock masses in alpine regions the basque arc basque cantabrian basin northern spain the geomechanical characterisation of rock masses in alpine regions is one of the main challenges currently facing rock mechanics these rock masses made up of very different materials and frequently tectonically disturbed are affected by engineering works giving rise to potentially important problems thus in the basque country these materials are at the cause of important fatalities occurring in recent years in this context we aim at characterising these materials with the ultimate purpose of predicting their behaviour the characterisation is initially approached based on the gsi mi and ci parameters following the hoek brown failure criterion this information is supplemented with field and laboratory measurements and by obtaining the rqd and rmr indices using the information obtained from 99 metering stations we develop a graphic classification procedure which allows us to distinguish materials based on their characteristics behaviour type and degree of associated problems and type and effectiveness of solutions provided eight classes of material are established

antarctica greenland and gulf of alaska land ice evolution from an iterated grace global mascon solution we have determined the ice mass evolution of the antarctica and greenland ice sheets ais and gis and gulf of alaska goa glaciers from a new grace global solution of equal area surface mass concentration parcels mascons in equivalent height of water the mascons were estimated directly from the reduction of the inter satellite k band range rate kbrr observations taking into account the full noise covariance and formally iterating the solution the new solution increases signal recovery while reducing the grace kbrr observation residuals the mascons were estimated with 10 day and 1 arc degree equal area sampling applying anisotropic constraints an ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances the details and causes of the spatial and temporal variability of the land ice regions studied are discussed the estimated mass trend over the total gis ais and goa glaciers for the time period 1 december 2003 to 1 december 2010 is 380 plus or minus 31 gt a exp 1 equivalent to 1 05 plus or minus 0 09 mma exp 1 sea level rise over the same time period we estimate the mass acceleration to be 41 plus or minus 27 gt a exp 2 equivalent to a 0 11 plus or minus 0 08 mm a exp 2 rate of change in sea level the trends and accelerations are dependent on significant seasonal and annual balance anomalies

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

sediment biogeochemistry of iron and sulfur in an acidic lake abstract the biogeochemical cycling of fe and s in the sediments of acidic big moose lake adirondack park ny u s a was investigated sediment cores and porewater samples were collected along a depth transect from the hypolimnion 24 m water depth metalimnion 17 m and epilimion 8 12 m four vertically distinguishable zones in the sediment environment were observed at each site 1 1 no3 disappearance near the sediment water interface 2 2 accumulation of solid phase fe in the top 5 cm 3 3 coincident accumulation of chromium reducible sulfur crs disappearance of so4 and minima in c s and 34s at or slightly below maxima in oxide bound fe and 4 4 homogenous background concentrations in s and fe below 30 and 10 cm respectively iron and sulfur accumulations in the upper 10 cm occurred at the same depths in cores of different ages indicating that diagenetic rather than depositional processes played a dominant role in determining near surface fe and s profiles although sediment accumulation rates varied along the transect the four zones were located at similar depths in the sediment column at all sites diagenetic processes play a major role in the development of these features in big moose lake the extent of fe enrichment was considerably greater in the metalimnetic and epilimnetic sediments in contrast concentrations of fe were lower in hypolimnetic sediments which appeared to be losing fe to the water column at all sites increases in total s from a background concentration of 60 80 mol g 1 of dry mass occurred in sediments dated approximately 1850 more recent increases to 560 mol sg 1 occurred asynchronously in the cores indicating an important role of sulfate reduction in adding s to sediments however organic sulfur accumulation accounted for 22 56 of the recent increase in sediment s concentrations of iron and organic carbon were high in lake sediments and probably do not limit s storage in this lake

reliability back analysis of landslide shear strength parameters based on a general nonlinear failure criterion abstract the shear strength parameters of a sliding surface are important parameters for the stability evaluation and engineering design of a landslide to consider the randomness uncertainty and the nonlinear characteristics of the geotechnical the reliability back analysis method of determining shear strength parameters of a landslide based on nonlinear mohr coulomb failure criteria is proposed in this study by analyzing a slope with linear failure surface the feasibility and validity of the proposed method are discussed in an engineering case the proposed method provides a new choice and reference for the determination of the shear strength parameters of the sliding surface of a landslide

coal mining under difficult geological conditions the can lignite open pit canakkale turkey abstract this paper describes the slope instability problems in the can canakkale northwestern turkey coal mine slope instabilities have been one of the major problems in the pit mine since the beginning of mining activities in particular the west and east sector panels in front of the tki turkish coal enterprises buildings and the seramic factory located in the vicinity of the pit mine have been suffering from slope instability problems to assess the instabilities field data collection from boreholes surface sampling and monitoring studies were performed deterministic stability analyses such as limit equilibrium sensitivity and back analyses were applied based on the results the active passive wedge type of failure was determined as the most dominant instability type based on the back analysis results mean values of residual shear strength parameters were determined as c 42 kpa o 8 the results also indicate that the excessive excavation of the toe along the huge lignite open pit was the main cause of the instability the weak contacts between the lithological units were also an important factor taking into consideration the results of the analyses some remedial measures were also suggested for the coal mine such as decreasing the inclination of the toe safe benching and effective drainage of surface water and groundwater

biogeochemical cycling in an organic rich coastal marine basin 8 a sulfur isotopic budget balanced by differential diffusion across the sediment water interface abstract the sulfur isotopic composition of the sulfur fluxes occurring in the anoxic marine sediments of cape lookout bight n c u s a was determined and the result of isotopic mass balance was obtained via the differential diffusion model seasonal pore water sulfate 34 s measurements yielded a calculated sulfate input of 0 6 sulfate transported into the sediments via diffusion appeared to be enriched in the lighter isotope because its concentration gradient was steeper due to the increase in the measured isotopic composition of sulfate with depth similarly the back diffusion of dissolved sulfide towards the sediment water interface appeared enriched in the heavier isotope the isotopic composition of this flux was calculated from measurements of the 34 s of dissolved sulfide and was determined to be 15 9 the isotopic composition of buried sulfide was determined to be 5 2 and the detrital sulfur input was estimated to be 6 2 an isotope mass balance equation based upon the fluxes at the sediment water interface successfully predicted the isotopic composition of the buried sulfur flux within 0 5 thus confirming that isotopes diffuse in response to their individual concentration gradients

a new general empirical approach for the prediction of rock mass strengths of soft to hard rock masses abstract it is almost impossible to prepare representative cores of rock masses including discontinuities patterns for laboratory studies to overcome these difficulties researchers have focused on developing empirical equations for estimating of the stress strain behavior of a rock mass including measurements of the discontinuity patterns as can be seen in the literature the uniaxial compressive strength value of rock mass ucs rm can be estimated by reducing the uniaxial compressive strength of intact rock material ucs i based on the quality of a rock mass represented by variables such as rock mass rating rmr geological strength index gsi and q value for this reason a unique reducing curve form empirical equation has limited application and generally cannot be applied to all kind of rock masses from particularly soft to hard rock masses in this study a new general empirical approach is constructed to estimate the strength of rock masses of varying hardness the new empirical equations have been calibrated using data from five slope failures and four sets of uniaxial compressive strength data of rock masses in the new empirical equations the ucs i is considered not only to be a scale parameter used in the strength reduction but also used to adjust the degree of strength reduction in conjunction with elastic modulus of the rock material e i the disturbance factor on the rock mass is taken into consideration by two separate reduction factors applied to the structure rating sr to capture increasing joint density and to the s and m b parameters of the hoek brown criterion to decrease the degree of interlocking hence non interlocked cohesionless under zero normal stress rock masses such as spoil piles can also be modeled in the new empirical approach

sulphur isotope geochemistry of pyrite from the upper cretaceous marshybank formation western interior basin abstract variations in the texture and sulphur isotopic composition of pyrite in the upper cretaceous marshybank formation are linked to depositional environment abundant framboidal and lesser euhedral pyrite precipitated in offshore marine rocks moderate quantities of pyrite also crystallized in brackish coastal plain rocks however in contrast to marine pyrite coastal plain pyrite is dominantly euhedral in texture reflecting direct precipitation from a porewater with a relatively low dissolved sulphide concentration in the marine rocks pyrite 34s values range from 35 7 to 27 4 avg 4 8 canyon diablo troilite cdt pyrite within carbonate concretions hosted in these marine rocks has a similar isotopic composition 49 8 to 10 6 cdt however isotopic values are often highly variable within individual concretions as a result of the heterogeneous nature of sulphate reduction and pyrite formation within marine sediments pyrite in coastal plain rocks is characterized by relatively high 34s values 4 2 to 35 5 avg 13 2 cdt while the overlying sideritized conglomerates have the lowest 34s values reported for cretaceous rocks from the western interior basin of north america 49 8 to 41 7 cdt very low 34s values which are only observed in the marine rocks are indicative of microbial sulphate reduction and pyrite formation in a sulphate replete i e open system higher 34s values up to 18 which were obtained for both the marine and coastal plain rocks are indicative of progressive pyrite crystallization in a sulphate limited i e closed system such conditions are expected in marine sediments as burial occurs and in brackish i e low sulphate sediments pyrite with very high 34s values 18 is common in the coastal plain rocks these high values are the result of influx of 34s enriched residual sulphide derived from overlying marine units a minor amount of 34s enriched pyrite is also present within and proximal to marine sedimentary unit h which was deposited at the same time as the coastal plain rocks we hypothesize that porewater containing 34s enriched residual sulphide flowed from the coastal plain and along unit h into the marine sediments thus producing anomalously high 34s pyrite

organic rich transitional facies in silled basins response to sea level change high resolution profiles of organic carbon delta sup 13 c sub org sulfur delta sup 38 s and some trace elements in cores from two silled basins kau bay indonesia and the black sea allow division of the sedimentary record into three distinct units representing a pleistocene fresh water brackish water facies unit 3 a holocene transitional facies unit 2 and a modern fully marine facies unit 1 the geochemical characteristics of these units are strikingly similar for both basins the sediments form unit 3 are characterized by the predominance of terrestrial organic matter mo and u concentrations at crustal abundance and positive delta sup 34 s values the transitional sediments unit 2 are strongly enriched in marine organic matter and mo v and u and have intermediate delta sup 34 s values sediments from the modern marine facies unit 1 are moderately organic carbon rich and slightly enriched in mo and u and have negative delta sup 34 s values the organic carbon rich sediments from unit 2 were formed by increased production during the transition from the pleistocene isolated fresh water brackish water environment to the modern open marine facies this temporarily higher productivity was caused by displacement of nutrients from the deep water into the euphotic zone owing to the gradual infilling by marine waters

optimized sequential extraction for carbonates quantification and δ13c analysis of calcite dolomite and siderite siderite is present in diverse types of rocks and sediments but its quantification is cumbersome when present in relatively low contents a new analytical method for the sequential separation of different carbonate phases is presented the separation quantification and characterization of the carbonates is based on different kinetic reactions during acid digestion in combination with monitoring the solution composition and the concomitant release of co2 trapping the released gasses permits the isotopic characterization 13c of the different phases based on published rate laws an idealized model was built to identify ph and temperature conditions for optimal separation of the various carbonates by taking the size distribution of carbonate particles into consideration results from the theoretical survey were implemented in an extraction scheme which was optimized and evaluated by tests on pure mineral phases and their mixtures further tests on a diverse array of sediment and rock samples validated the specificity and reproducibility of the method

numerical methods in rock mechanics the purpose of this civilzone review paper is to present the techniques advances problems and likely future development directions in numerical modelling for rock mechanics and rock engineering

formation of pyrite in freshwater sediments implications for c s ratios abstract the vertical distribution of pyrite acid volatile sulphide avs carbon and total s st were determined directly in the sediments of three lakes of different trophic status the results showed that freshwater pyrite formation reflects the redox status of the sediment or overlying waters it appears to form chiefly in reducing sediments which are subject to oxidizing influences by either a low turnover of organic carbon or periodic incursions of oxygen although there are high concentrations of avs in the near surface sediments of productive lakes very little is diagenetically converted to pyrite the feasibility of using sulphur ratios to diagnose whether rocks were formed in marine or freshwater environments is assessed new values for fes 2 fes of 0 5 5 show that this ratio does not provide a reliable test values of c sp where sp represents pyrite sulphur lie within the range of 160 700 and are much higher than previously measured ratios of c s t of 1 50 these new determinations show that if pyrite sulphur is unequivocally measured c s ratios may be a more sensitive indicator of salinity than had been previously thought

degree of pyritization of iron as a paleoenvironmental indicator of bottom water oxygenation abstract a new method is presented for recognizing the degree of bottom water oxygenation in organic carbon bearing rock the method uses the parameter degree of pyritization dop which is the ratio of pyritic fe to pyritic fe acid soluble fe sediments with ages ranging from devonian to cretaceous have been classified on paleoecological and sedimentological criteria as having been deposited in aerobic conditions deposited in fully oxygenated bottom waters restricted marine conditions deposited in waters with low oxygen concentrations or inhospitable bottom conditions where little or no oxygen is present and h2s may be continually or intermittently present aerobic dop

carbon sulfur iron systematics of the uppermost deep water sediments of the black sea box cores recovered during leg 4 of the 1988 r v knorr black sea oceanographic expedition from deep water regions of the basin were dominated by coccolith rich microlaminated unit 1 sediment and muddy gray turbidite layers both organic carbon oc and pyrite sulfur values for unit 1 display narrow ranges with mean concentrations of 5 3 1 1 1 wt and 1 3 0 3 wt respectively unit 1 is not enriched in pyrite s relative to sediments deposited under oxygenated bottom waters normal marine sediments with comparable oc concentrations carbon sulfur relationships evaluated on a calcium carbonate free basis to avoid spurious correlations resulting from dilution effects demonstrate that oc and pyrite s are essentially decoupled these observations combined with the persistence of elevated pore water sulfide to depth and a strong correlation between pyrite s and the detrital fe component argue strongly for limitation of pyrite formation in unit 1 by the availability of reactive fe unit 1 fe limitation is further indicated by degree of pyritization dop studies a measure of the extent to which the original potentially reactive fe has been transformed to pyrite these studies show sulfidation of reactive fe ranging from 57 to 78 with dop values independent of oc concentration unit 1 dop profiles suggest that the majority of the pyrite is formed in the sulfidic water column and or very close to the sediment water interface pyrite s concentrations of unit 1 when compared with the particulate reduced sulfur fluxes measured in time series sediment traps are compatible with predominantly water column pyrite formation because of the limitations in the supply of reactive fe associated with the comparatively high supply of oc the microlaminated sediment is characterized by c s ratios greater than those typical of holocene oxically deposited sediments the turbidite muds of the deep basin display high reduced s values relative to holocene normal marine sediments in samples with low oc concentrations low c s ratios this reflects pyrite formation under anoxic sulfidic bottom water conditions in a probable upper slope source region as well as during transport and final deposition intermediate dop values for the turbidites in part a product of their rapid rate of deposition reveal that fe limitation is ultimately not a factor and that further pyrite should form during burial however the very rapid rate at which unit 1 pyrite forms suggests fundamental differences between the overall reactivities of the fe phases associated with the microlaminated and turbiditic sediments the signature of water column anoxia with regard to sedimentary pyrite formation is clearly indicated by the high dop values of unit 1 and the comparatively high levels of s associated with the low concentrations of oc of the turbidite muds this agrees with similar conclusions based on studies of ancient sedimentary rocks

new approaches to the characterization of clay bearing densely jointed and weak rock masses various classification systems for rock masses have been used in engineering applications however these systems are not sufficient to classify clay bearing densely jointed and weak rock masses among the factors that cause this deficiency are the damaging effect of water on rocks which has not sufficiently been described in the existing classification systems this factor was allowed for by the inclusion of new parameters in the modified rock mass classification m rmr system developed in recent years the aim of this study is to make contributions to the m rmr classification system and to overcome the difficulties encountered in the classification procedure for this purpose data were collected for rock mass classification from 13 clay bearing densely jointed and weak rock masses in four regions yatagan soma baskoyak and guvenc located in the western and middle parts of turkey the discontinuity data were collected by the line survey technique and evaluated by statistical methods in addition to the uniaxial compressive strength test for the determination of the rating for intact rock strength the block punch index test was also considered as an alternative parameter and the slake durability index test and x ray diffraction analyses were performed on 104 samples collected from the studied rock masses further the weathering coefficient wc determined by schmidt hammer was considered as an alternative parameter for the determination of the rating for joint weathering as a result of statistical evaluation of data obtained from the field and laboratory studies it has been concluded that the block punch index bpi could be used as an alternative parameter for the determination of the rating for intact rock strength in the m rmr classification system it was also found that the slake durability index id determined at the fourth cycle would be a more effective approach than the second cycle index that has previously been used to express the unfavourable effect of water on the rock mass the propositions made in the present work to contribute to the m rmr system were tested in back analyses of three previously failed slopes and the performance of the system with the newly introduced improvements appeared to be satisfactory

marine flooding surfaces recorded in permian black shales and coal deposits of the main karoo basin south africa implications for basin dynamics and cross basin correlation abstract the marine origin of black shales in the context of the permian postglacial development of the karoo basin south africa is subject of an ongoing controversial discussion here we present and discuss palynological and sedimentological data providing evidence of a transgressive event during the early guadalupian palynofacies assemblages of the black shales of the southern basin include marine phytoplankton that exhibit peak abundance within the whitehill shales and which also occur within siltstones and glauconitic sandstones on top of the no 5 coal seam of the north eastern basin palynostratigraphic control makes this marine signal a powerful tool for cross basin correlation moreover palynofacies analysis demonstrates a facies transition from terrestrial lacustrine and fluvio deltaic in the northeast to deep marine in the south western parts of the basin

trace fossils as indicators of environmental change in holocene sediments of the archipelago sea northern baltic sea abstract biogenic structures in holocene sediments from the archipelago sea northern baltic sea were characterized through the analysis of x ray images of four cores collected from water depths between 32 and 66 m in the area initial colonization of endobenthic invertebrates occurred at 7800 80 calendar years bp the trace assemblage at this level is low diversity small diameter shallowly tiered and palaeophycus dominated rare arenicolites are also observed early colonization coincides with increasing marine influence in the post glacial lacustrine setting just before the dramatic onset of brackish water conditions established after 7600 bp the post incursion brackish water assemblage possesses a higher diversity of traces planolites arenicolites lockeia teichichnus which is taken to reflect the enhanced salinity and trophic state of the basin the shift from palaeophycus mottling to a planolites dominated fabric represents changed behavioural patterns in the endobenthic community due to changed substrate properties the ethology of the succeeding trace assemblage also represents a switch from domicile based activities such as predation scavenging and interface dominated deposit feeding to shallow tier deposit feeding finally traces are excluded from thinly laminated intervals demonstrating that seafloor oxygen deficiency commonly reached levels that were detrimental to colonization of the sediment substrate

early diagenesis of foraminiferal calcite under anoxic conditions a case study from the landsort deep baltic sea iodp site m0063 abstract the chemical composition of foraminiferal calcite is widely used for studying past environmental conditions and biogeochemistry however high rates of microbial organic matter degradation and abundant dissolved metal sources in sediments and pore waters may impede the application of foraminifera based proxies due to formation of secondary carbonates or other authigenic minerals on and or inside of foraminiferal tests secondary carbonate precipitation severely alters the bulk foraminiferal geochemistry and can be difficult to eliminate through standard foraminiferal trace element cleaning procedures we present results showing the mineral composition and formation sequence of diagenetic coatings on foraminiferal tests formed under extreme anoxic conditions in the baltic sea s deepest basin the landsort deep iodp exp 347 site m0063 our study focuses primarily on the diagenetic carbonates present on and in the tests of the low oxygen tolerant benthic foraminiferal species elphidium selseyensis and elphidium clavatum we applied various geochemical and imaging methods to ascertain the diagenesis processes and the authigenic mineral formation sequence on foraminifera the authigenic carbonates were enriched in mn mg fe and ba depending on the environmental redox conditions when the authigenic carbonates were precipitated concentrations of redox sensitive elements such as mn and fe were particularly elevated in bottom waters and sedimentary pore waters under oxygen depleted conditions in the landsort deep resulting in formation of carbonates with highly elevated mn and fe contents in addition to mn and fe carbonates several other types of authigenic minerals also formed on and in the foraminiferal chambers including authigenic calcite and non carbonate accessory minerals the formation sequence reveals the redox sensitivities of different elements and the preferential sequence of oxidants used by the microbes during organic matter oxidation and secondary redox reactions this study provides a case study of extreme early diagenesis of foraminiferal calcite and may serve as a valuable guide when interpreting foraminiferal trace element records from low oxygen environments

antarctic contribution to sea level rise observed by grace with improved gia correction antarctic volume changes during the past 21 thousand years are smaller than previously thought and here we construct an ice sheet history that drives a forward model prediction of the glacial isostatic adjustment gia gravity signal the new model in turn should give predictions that are constrained with recent uplift data the impact of the gia signal on a gravity recovery and climate experiment grace antarctic mass balance estimate depends on the specific grace analysis method used for the method described in this paper the gia contribution to the apparent surface mass change is re evaluated to be 55 13 gt yr by considering a revised ice history model and a parameter search for vertical motion predictions that best fit the gps observations at 18 high quality stations although the gia model spans a range of possible earth rheological structure values the data are not yet sufficient for solving for a preferred value of upper and lower mantle viscosity nor for a preferred lithospheric thickness grace monthly solutions from the center for space research release 04 csr rl04 release time series from january 2003 to the beginning of january 2012 uncorrected for gia yield an ice mass rate of 2 9 29 gt yr the new gia correction increases the solved for ice mass imbalance of antarctica to 57 34 gt yr the revised gia correction is smaller than past grace estimates by about 50 to 90 gt yr the new upper bound to the sea level rise from the antarctic ice sheet averaged over the time span 2003 0 2012 0 is about 0 16 0 09 mm yr

phosphorus recycling and burial in baltic sea sediments with contrasting redox conditions in this study redox dependent phosphorus p recycling and burial at 6 sites in the baltic sea is investigated using a combination of porewater and sediment analyses and sediment age dating pb 21

pyrite and organic matter in phanerozoic normal marine shales data have been obtained from our own chemical analyses and from the literature for the concentrations of organic carbon c and pyrite sulfur s in over 600 samples of cambrian to recent normal marine shales normal marine refers to deposition in oxygenated bottom water as evidenced by the presence of benthic fossils and or indicators of bioturbation all samples were selected to minimize 1 1 loss of c and or s due to weathering at the outcrop by emphasizing the use of drill core material 2 2 analytical errors and non diagenetic effects by avoiding sediments low in c or s content such as sandstones 3 3 fe limitation of pyrite formation by avoiding limestones cherts and euxinic shales 4 4 metamorphic loss of c relative to s by avoiding rocks obviously subjected to even low grade metamorphism our results indicate that 1 there is generally a good positive linear correlation between organic c and pyrite s for normal marine shales of all ages and 2 the mean cs ratio for normal marine shales has varied over time devonian to tertiary shales exhibit mean cs weight ratios 1 8 0 5 somewhat lower than quaternary sediments meancs 2 8 this we believe is due to preferential c loss relative to s during biogenic methanogenesis plus diagenetic heating distinctly lower mean c s values for the cambrian and ordovician 0 5 0 1 cannot be explained solely in terms of diagenetic c loss and instead must represent low original ratios the low original ratios we suggest were due mainly to the absence of bacterially refractory organic matter added to the marine environment by rivers at that time because the major source of such material vascular land plants had not yet evolved this along with a possibly lower degree of bioturbation contributed to enhanced pyrite formation and preservation and thus lower early paleozoic cs ratios

metal pollution of estuarine sediments caused by leaching of acid sulphate soils abstract this study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate as soil landscapes in the boreal zone finland the main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish water estuary in order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the vora river which is one of the most heavily as soil impacted rivers in finland and europe two of the cores were rather deep 2 5 m and 4 0 m and the others were shallow 0 4 m and 0 8 m the results showed that an appreciable amount of aluminium al cobalt co cadmium cd copper cu manganese mn nickel ni and zinc zn were elevated in the surface and sub surface of the sampled bottom sediments compared to the deeper sediment background levels these metals are all known to be abundantly leached from the as soils at the site approximately 4 km away from the river mouth the concentrations of cd co mn ni and zn were elevated 5 100 times as compared to the background levels and showed an intriguing cyclic pattern most likely reflecting seasonal leaching dynamics in the as soil landscapes in contrast metals that are not abundantly leached from as soils i e chromium cr iron fe and vanadium v had consistently low concentrations throughout all sediment cores the elevated metal concentrations in the top layers of the sediments in the estuary are alarming the continuous land uplift of the region combined with the episodic rapid declines in ph may result in short and long term extensive release of metals this in turn may have significant effects on the trace metal contents in the gulf of bothnia and the entire baltic sea

controls on c s ratios in hemipelagic upwelling sediments the relationship between organic carbon and reduced sulfur concentrations was investigated in hemipelagic sediments underlying highly productive regions of the ocean and oxic to suboxic waters the benguela upwelling area peru and oman margins at all three sites the degree of pyritization averaged close to 0 4 indicating that reactive iron was probably not limiting for pyrite formation complete sulfate reduction occurred in the upper sections of the sediments from the oman and peru margins however dissolved sulfate never decreased below 5 mm in the benguela upwelling sediments the authors attribute this to more advanced organic matter degradation at the benguela upwelling site c s ratios increased with increasing organic carbon concentrations at all sites for sediments with greater than 3 wt toc the c s ratio averaged about 1 3 and 1 8 times the normal marine ratio of 2 8 at the benguela upwelling and peru margin sites respectively but 2 9 times this value in the oman margin sediments they hypothesize that the quality of the organic matter undergoing burial and rates of near interfacial transport processes are the dominant controls on sulfur burial in these sediments

formation and solid solution behavior of ca rhodochrosites in marine muds of the baltic deeps authigenic ca rhodochrosites are found in organic rich sediments in the deep anoxic basins of the baltic sea rhodochrosite formation is apparently the result of organic matter degradation the rhodochrosite contains 10 to 40 mol caco3 and 2 to 5 mol mgco3 as determined by microprobe the composition of the carbonates at a given depth varies by about 5 mol mnco3 sem revealed the rhodochrosite to be present as globular aggregates consisting of microcrystallites dissolution features such as cavities within the aggregates are frequently observed and indicate that extensive recrystallization takes place pore waters are greatly supersaturated with respect to both rhodochrosite and calcite rhodochrosite is only found in sediments where pore waters show the highest degree of supersaturation due to ion exchange ca2 diffuses from the underlying freshwater clays this results in increasing aca2 amn2 ratios in the pore waters from the sediment surface downward in response to this the maximum caco3mnco3 ratio also increases with depth the composition of rhodochrosite which forms under these conditions may be determined by both the porewater aca2 amn2 and precipitation kinetics however if their composition is controlled solely by the aca2 amn2 in solution their behavior can be described by a regular solid solution model

sedimentary molybdenum cycling in the aftermath of seawater inflow to the intermittently euxinic gotland deep central baltic sea abstract molybdenum mo concentrations and isotope compositions in sediments and shales are commonly used as proxies for anoxic and sulfidic i e euxinic conditions in the water column of paleo marine systems a basic assumption underlying this practice is that the proxy signal extracted from the geological record is controlled by long term order of decades to millennia mo scavenging in the euxinic water column rather than mo deposition during brief episodes or events order of weeks to months to test whether this assumption is viable we studied the biogeochemical cycling of mo and its isotopes in sediments of the intermittently euxinic gotland deep in the central baltic sea here multiannual to decadal periods of euxinia are occasionally interrupted by inflow events during which well oxygenated water from the north sea penetrates into the basin during these events manganese mn oxyhydr oxide minerals are precipitated in the water column which are known to scavenge mo we present sediment and pore water mo and mo isotope data for sediment cores which were taken before and after a series of inflow events between 2014 and 2016 after seawater inflow pore water mo concentrations in anoxic surface sediments exceed the salinity normalized concentration by more than two orders of magnitude and coincide with transient peaks of dissolved mn a fraction of the mo liberated into the pore water is transported by diffusion in a downward direction and sequestered by organic matter within the sulfidic zone of the sediment diffusive flux calculations as well as a mass balance that is based on the sedimentary mo isotope composition suggest that about equal proportions of the mo accumulating in the basin are delivered by mn oxyhydr oxide minerals during inflow events and mo scavenging with hydrogen sulfide during euxinic periods since the anoxic surface sediment where mo is released from mn oxyhydr oxides are separated by several centimeters from the deeper sulfidic layers where mo is removed the solid phase record of mo concentration and isotope composition would be misinterpreted if steady state mo accumulation was assumed based on our observations in the gotland deep we argue that short term redox fluctuations need to be considered when interpreting mo based paleo records

holocene history of the baltic sea as recorded in a sediment core from the gotland deep a 4 m long sediment core from the gotland deep baltic sea was investigated by means of biostratigraphical and chemical parameters and c 14 datings this multidisciplinary approach allows us to ev

the geochemistry of manganese carbonate in panama basin sediments abstract the mn distribution in panama basin area sediments and interstitial waters is discussed striking surficial mn enrichments produced by a well known diagenetic recycling process characterize the sediments of the region thermodynamic solubility calculations indicate that in at least one core interstitial waters approach saturation with respect to mnco3 a mixed carbonate phase of composition mn48 ca47 mg5 co3 was recovered from an ash band in the same core the association of this material with the coarse volcaniclastic debris is thought to result from facile manganous carbonate precipitation in sediment horizons of coarser mean grain size since sulphate reduction in the upper two metres of panama basin sediments is fairly minor little increase in alkalinity is observed and it is postulated that significant production of carbonate alkalinity is not a prerequisite for manganous carbonate generation in hemipelagic sediments a more important factor appears to be the availability of mn oxides for solution during early diagenesis stable c isotopic analyses indicate that little c of organic origin is used in the precipitation reaction in either panama basin or loch fyne scotland sediments

manganese uptake during calcite precipitation from seawater conditions leading to the formation of a pseudokutnahorite manganoan magnesian calcite overgrowths were precipitated from artificial seawater at 25 c on pure calcite seeds using a constant disequilibrium technique the composition of the overgrowths and more specifically their mn mg na and sr content was determined as a function of the precipitation rate and mn2 concentration in the parent solution x ray diffraction patterns indicate that the overgrowths produced were one phase multicomponent solid solutions and contained up to 40 mole mnco3 the amount of mn coprecipitated with calcite decreased with increasing precipitation rate thus overgrowths are not in exchange equilibrium with the solutions from which they precipitated a kinetic model is proposed which adequately describes the composition of the overgrowths in terms of the relative precipitation rate of an 8 10 mole magnesian calcite and a pseudokutnahorite from seawater the possible existence of a pseudokutnahorite in marine sediments and its implications are discussed the concentration of mg in the overgrowths decreased with increasing mnco3 content but their mg ca ratio remained nearly constant strontium and na incorporation was strongly dependent on the number of available nonlattices sites

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 carbon sulphur and iron in recent semi euxinic sediments of kau bay indonesia kau bay island of halmahera eastern indonesia is a 470 m deep basin separated from the pacific ocean by a sill that is at present only 40 m below sea level during weichselian time the sea level dropped below the depth of the sill and freshwater sediments were deposited these sediments are rich in organic matter corg 2 6 wt with terrigenous isotope characteristics 13corg 28 to 30 and are also rich in sulphur s 4 wt this sulphur enrichment is interpreted to be a late diagenetic feature related to diffusion of dissolved sulphate and sulphide from the marine sediments into the freshwater sediments the sulphur in these sediments has a 34s value of 15 the overlying holocene sediments consist of marine muds deposited in alternating low oxygen and h2s bearing bottom waters the marine sediments are also rich in organic matter corg 2 6 wt but of mixed terrigenous and marine origin 13c 25 to 19 moreover the sulphur content of these holocene sediments is lower s 1 2 wt and isotopically lighter 34s 20 in addition to pyrite large amounts of acid volatile sulphur avs compounds accumulate in kau bay the reactive iron content of the sediment limits the amount of iron that is sulphidized while the supply of oxidants controls the limited conversion of avs to pyrite total and reactive iron contents are strongly correlated with the amount of terrigenous organic matter as a consequence of their common provenance and depositional histories the marine sediments in kau bay show no simple relation between organic carbon and sulphur

engineering characteristics of ankara greywacke under the foundation of the beytepe open air theatre ankara turkey the construction of a large open air theatre having with an audience capacity of 7 000 is planned at the beytepe campus of hacettepe university located near ankara turkey in the heart of anatolia the foundation of the open air theatre is composed of weak and heavily jointed ankara greywacke an estimation of the strength and deformation of the ankara greywacke was required for assessments of short and long term stability accordingly rock mass characterization of the ankara greywacke was investigated in detail by scan line surveys and back analyses of in situ tests performed on the excavated surface of the rock mass the final version of the hoek and brown criterion hoek et al in proceedings of the north american rock mechanics society meeting toronto canada pp 1 6 2002 together with and improvements proposed by sonmez and gokceoglu int j rock mech min sci 43 671 676 2006 were considered together for the back analyses of small slope benches subjected to plate loading test loaded to failure in addition the plate loading test data were used with some well known empirical equations for predicting of deformation modulus of rock masses to calculate ranges of values of the geological strength index gsi the static and pseudostatic slope stabilities of the audience seating structures to be supported by benches excavated into the rock were also analyzed the stability assessments revealed the unlikelihood of large rock mass failures for the short term construction stages or for the long term as constructed conditions under static or pseudo static conditions additionally the analyses showed that there was no need for anchors between the concrete seating structures and greywacke rock mass

sulphur speciation and pyrite formation in meromictic ex fjords abstract powell and sakinaw lakes are stably stratified ex fjords which became isolated from the strait of georgia approximately 11000 years ago by emerged sills due to post glacial isostatic rebound both lakes contain highly sulphidic relict seawater powell 3 0 mm sakinaw 5 5 mm at depth chemically analogous to porewaters of reducing marine sediments sakinaw has a very sharp chemocline located just below the oxic anoxic interface whereas in powell the interface is spread out over 200 m of the water column sulphate is present in the oxic part of the water column at much higher concentrations in sakinaw lake up to 65 m than in powell lake 10 m and increases in concentration with depth until reaching the interface below which it is rapidly depleted sulphur oxyanions of intermediate oxidation state thiosulphate sulphite and tetrathionate are not detectable in either lake particulate elemental sulphur was also not found in either lake high concentrations of reduced iron and hydrogen sulphide result in formation of iron monosulphides and pyrite in the anoxic water columns of both lakes the presence of these two minerals correlates well with their calculated saturation states pyrite precipitates with no apparent monosulphide precursor at depths where dissolved sulphide concentrations are low and monosulphide phases are undersaturated as sulphide levels increase at greater depths the waters become saturated with respect to iron monosulphides and particulate fes species are detected in the water column the large separation of the oxic anoxic interface and the chemocline in sakinaw 10 m and especially in powell lake 100 m relative to that of sediment porewaters allows excellent resolution of these processes

deterministic stability and sensitivity analyses of slopes in jointed rock masses abstract the paper describes a deterministic stability analysis together with a sensitivity analysis of slopes in heavily jointed rock mass with planar circular or combined modes of failure this approach is based on the modified sarma method of analysis in which the strength parameters are derived from the rock mass classification rmr system and applied to the hoek and brown rock failure criterion the results of the analysis are presented as a plot of factor of safety f against acceleration k which shows the effect of vibrations blasting earthquake etc and acceleration on the factor of safety of slopes the paper also considers the influence of various strength parameters on the factor of safety and the acceleration k application of this technique is illustrated with the aid of an example of a slope in an iron ore mine

isotopic composition and speciation of sulfur in the miocene monterey formation reevaluation of sulfur reactions during early diagenesis in marine environments the timing and pathways of early diagenetic sulfur transfer from dissolved species in pore waters to solid inorganic and organic compounds in sediments have been studied in the miocene monterey formation santa maria basin onshore california correlation between concentrations of total organic carbon toc and total sulfur ts in addition to concentrations of titanium aluminum total iron and reactive iron have been used to infer organic matter reactivity redox conditions and relative rates of clastic and biogenic input for each lithofacies isotopic compositions of six sulfur species acid volatile disulfide kerogen bitumen sulfate and elemental have provided information regarding relative timing of sulfur incorporation sulfate diffusivity in the upper centimeters of the sediments and the sources of sulfur for individual species isotopically the disulfide species expresses the greatest fractionation relative to estimated values of miocene seawater sulfate 22 cdt on average disulfide is depleted in 34s by 10 4 relative to kerogen and by 9 9 relative to acid volatile sulfide the 34s of bitumen shows no systematic change relative to 34skeregon suggesting the presence of migrated bitumen isotopic similarity of sulfate and elemental sulfur to sulfides and bitumen indicates that sulfate and elemental sulfur are chemical and or biological oxidation products derived from sulfides and bitumen consistent ordering of isotopic values for sulfur species disulfide acid volatile sulfide kerogen indicates that pyrite precipitated nearest to the sediment water interface under mildly reducing conditions and with little or no decrease in sulfate concentration relative to seawater enrichment of 34s in acid volatile sulfide and kerogen sulfur resulted from formation of these species at greater depths or in restricted micro environments under more reducing conditions and with low concentrations of porewater sulfate the formation of acid volatile sulfide after pyrite but during early diagenesis is significant because it implies more strongly reducing conditions than are generally recognized in deep water marine sediments

assessment of the failure mechanism of a highwall slope under spoil pile loadings at a coal mine abstract the design of a highwall in coal mining involves the consideration of many factors the evaluation of a lignite strip coal mine at yatag an in southwest turkey has provided an opportunity to combine both qualitative and quantitative factors in highwall design in this paper an attempt has been made to illustrate an instability problem that occurred in a highwall externally loaded by a spoil pile in the southern part of the pit geotechnical data with slope monitoring information were evaluated and shear strength of the highwall material was determined using non linear failure criterion for jointed rock masses in conjunction with rock mass classification using a model for the loaded highwall these studies were complemented by limit equilibrium back analysis and finite element stress analysis incorporating the effect of the spoil pile loadings the results of the back analysis and numerical modelling which confirmed each other and detailed examination of geotechnical data with movement monitoring records indicate that the instability occurred by shallow seated circular failures mainly caused by the stresses exerted by the pile the progressive failure developed through a combination of sliding along structural discontinuities and failure through the moderate quality low strength rock mass in addition the calculated slip surfaces match the actual slip surfaces and the non linear shear strength failure criterion confirmed that the mobilized shear strength appears realistic for design purposes

outcrop scale physical properties of burns formation at meridiani planum mars 1 a rock mass rating rmr analysis was performed on an outcrop of burns formation at meridiani planum mars rmr values were calculated for the present dry conditions rmr 63 and past wet conditions rmr 52 for present day dry conditions the rock mass has an in situ modulus of deformation e of 21 1 gpa cohesive strength c 0 of 4 64 mpa and tensile strength t 0 of 0 24 mpa these values were reduced by at most 50 during previous water saturated conditions the critical grain crushing pressure p for dry conditions is 19 5 gpa with an uncertainty of about an order of magnitude analysis of the rover observations indicates that the physical properties of burns formation are in the range of analogous terrestrial porous rock masses such as sandstone and shale