fractionation of sulfur isotopes during bacterial sulfate reduction in deep ocean sediments at elevated temperatures abstract a numerical model of sulfate reduction and isotopic fractionation has been applied to pore fluid so 4 2 and 34 s data from four sites drilled during ocean drilling program odp leg 168 in the cascadia basin at 48 n where basement temperatures reach up to 62 c there is a source of sulfate both at the top and the bottom of the sediment column due to the presence of basement fluid flow which promotes bacterial sulfate reduction below the sulfate minimum zone at elevated temperatures pore fluid 34 s data show the highest values 135 yet found in the marine environment the bacterial sulfur isotopic fractionation factor is severely underestimated if the pore fluids of anoxic marine sediments are assumed to be closed systems and rayleigh fractionation plots yield erroneous values for by as much as 15 in diffusive and advective pore fluid regimes model results are consistent with 1 077 0 007 with no temperature effect over the range 1 8 to 62 c and no effect of sulfate reduction rate over the range 2 to 10 pmol cm 3 d 1 the reason for this large isotopic fractionation is unknown but one difference with previous studies is the very low sulfate reduction rates recorded about two orders of magnitude lower than literature values that are in the range of mol cm 3 d 1 to tens of nmol cm 3 d 1 in general the greatest 34 s depletions are associated with the lowest sulfate reduction rates and vice versa and it is possible that such extreme fractionation is a characteristic of open systems with low sulfate reduction rates

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

rethinking the ancient sulfur cycle the sulfur biogeochemical cycle integrates the metabolic activity of multiple microbial pathways e g sulfate reduction disproportionation and sulfide oxidation along with abiotic reactions and geological processes that cycle sulfur through various reservoirs the sulfur cycle impacts the global carbon cycle and climate primarily through the remineralization of organic carbon over geological timescales cycling of sulfur is closely tied to the redox state of earth s exosphere through the burial of oxidized sulfate and reduced sulfide sulfur species in marine sediments biological sulfur cycling is associated with isotopic fractionations that can be used to trace the fluxes through various metabolic pathways the resulting isotopic data provide insights into sulfur cycling in both modern and ancient environments via isotopic signatures in sedimentary sulfate and sulfide phases here we review the deep time 34s record of marine sulfates and sulfides in light of recent advances in understanding h

a unique isotopic fingerprint of sulfate driven anaerobic oxidation of methane the largest reservoir of the powerful greenhouse gas methane is in marine sediments and catastrophic release of this methane has been invoked to explain climate perturbations throughout earth history marine methane oxidation is mainly coupled anaerobically to microbial sulfate reduction which both limits and controls the release of methane from this sedimentary reservoir to the rest of earth s surface methane can be transported within the pore space of marine sediments either via diffusion or as bubbles when methane travels in bubbles these bubbles often are not completely oxidized and reach the overlying water where the methane emerges from the sediment in cold seeps although paleo cold seeps can be identified by geological features such as carbonate mounds a geochemical signature for cold seeps remains elusive we demonstrate using the sulfur and oxygen isotope composition of sulfate that a unique isotopic signature emerges during microbial sulfate reduction coupled to methane oxidation in bubbling cold seeps this isotope signature differs from that when sulfate is reduced by either organic matter oxidation or by the slower diffusive flux of methane within marine sediments we also show through a comparison with the literature that this unique isotope fingerprint is preserved in the rock record in authigenic buildups of barite associated with methane cold seeps

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

biochronology of selected bowser basin strata tectonic significance recent evaluation and reinterpretation of fossil floral and faunal data more clearly define the ages of strata exposed in the groundhog coalfield and the surrounding bowser basin of north central b

geochemical characteristics of iron in sediments from the sea of marmara abstract two 1000 cm long sediment cores were recovered from the sea of marmara one with the occurrence of gas hydrates in the western high and the other without hydrates in the cinarcik basin differences in mineralogical and chemical compositions have been identified between the two sediment cores based on the results of the mineralogical and geochemical analyses the main sources of the sediments are quite similar for both investigated areas but the authigenic components are different particularly iron sulfides and carbonates authigenic fe ii carbonate are much higher in core mrs cs 05 in the western high while crystalline fe iii phases are more abundant in core mrs cs 16 in the cinarcik basin notably the enrichments of greigite fe3s4 a metastable ferromagnetic iron sulfide mineral and intermediate polysulfide as well as iron carbonates are identified at 400 cmbsf with the maximum iron content in core mrs cs 05 these indicate the presence of a more reducing and acidic environment in the western high mainly due to higher organic matter content and seepage of heavy hydrocarbons in the sediments

sulfur and oxygen isotope tracing of sulfate driven anaerobic methane oxidation in estuarine sediments we use multiple stable isotope measurements in two highly stratified estuaries located along the mediterranean coast of israel the yarqon and the qishon to explore the consumption of sulfate through the anaerobic oxidation of methane sulfate driven aom at both sites pore fluid sulfate is rapidly consumed within the upper 15 20 cm although the pore fluid sulfate and dissolved inorganic carbon dic concentration profiles change over a similar range with respect to depth the sulfur and oxygen isotopes in the pore fluid sulfate and the carbon isotopes in the pore fluid dic are fundamentally different this pore fluid isotope geochemistry indicates that the microbial mechanism of sulfate reduction differs between the studied sites we suggest that in the yarqon estuary sulfate is consumed entirely through aom whereas in the qishon both aom and bacterial sulfate reduction through organic matter oxidation coexist these results have implications for understanding the microbial mechanisms behind sulfate driven aom our data compilation from marine and marginal marine environments supports the conclusion that the intracellular pathways of sulfate reduction varies among environments with sulfate driven aom the data can be used to elucidate new pathways in the cycling of methane and sulfate and the findings are applicable to the broader marine environment

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

currents and sediment transport in mangrove forests abstract a field study of the tidal currents cohesive sediment dynamics and transport of organic carbon in a highly vegetated mangrove swamp was carried out at middle creek cairns australia the interaction of tidal currents and the vegetation generated jets eddies and zones of stagnant waters which were numerically modelled a high value of the manning friction coefficient n 0 1 was derived by the dense vegetation about 80 of the suspended sediment brought in from coastal waters at spring flood tide was trapped in the mangroves corresponding to about 10 12 kg of sediment m 1creek length spring tide resulting in a rise of the substrate by about 0 1 cm year 1 the selective trapping of clay was caused by flocculation of the finer particles in the mangroves there was an indication of a slight inwelling of organic carbon creek water was readily differentiated from mangrove water by large differences in the molecular weight distribution of the dissolved organic carbon

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

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

semianthracite anthracite and meta anthracite in central canadian cordillera their geology characteristics and coalification history abstract in the jurassic and early cretaceous bowser basin and late cretaceous sustut basin in the north central canadian cordillera significant resources of coal ranging in rank from medium volatile bituminous coals to meta anthracite occur coal seams are up to 5 m thick have calorific values daf ranging up to 39 400 kj kg and fixed carbon daf up to 99 the coal seams are vitrinite rich have moderate to high sulphur contents and are variably argillaceous in the groundhog coal field of the bowser basin the coals are mainly anthracites and meta anthracites which are commonly cut by carbonate and quartz veins and are variably oxidized the orientation of the optical indicating surface together with regional maturation patterns suggest that the coalification in the groundhog coal field was pre tectonic and thus pre mid cretaceous extrapolation of the measured coalification gradients suggests that the coal measures were buried to depths of the order of 5000 m stratigraphic variation in the coalification gradients exist and are a product of varying thermal conductivity of the strata higher coalification gradients and levels of coalification in the southern part of the coal field reflect a combination of deeper depth of burial and higher paleoheat flow numerical modeling of the coalification gradients and burial histories suggest that paleoheat flows on the order of 80 mw m2 existed such values are consistent with deposition in a back arc basin in the sustut basin the coal ranges in rank from medium volatile bituminous coal to semianthracite and is up to about 2 m thick preliminary analyses indicate a good correlation between levels of coalification and stratigraphy which suggests that the coalification is pre tectonic pre mid tertiary the prominent variation in coal rank in the sustut basin is probably a result of the marked variation in depth of burial of the strata in isolated fault bouuded basins

modelling of erosion processes associated with rainfall triggered lahars following the 2011 cordon caulle eruption chile abstract in this work we investigate the sheet and rill erosion process as a possible lahar initiation mechanism in two catchments located in villa la angostura argentina southern andes in association with the 2011 eruption of cordon caulle chile a few days after the climactic phase of the eruption several lahar events occurred in villa la angostura where 15 cm of tephra mantled the slopes the physically based model lisem openlisem 2013a b was applied to two small catchments where sheet and rill erosion of tephra deposits was observed model input parameters related to vegetation soil surface and infiltration were obtained from field measurements geotechnical tests and the literature a total of 20 scenarios were simulated using a range of values of rainfall intensity and duration and hydraulic conductivity only 16 of these scenarios resulted in erosion results show that hydraulic conductivity ks and rainfall intensity significantly affect the runoff volume with the smallest ks i e the tephra deposits associated with the largest fraction of fine ash being associated with the largest eroded volumes and the largest discharges of water and sediment the scenarios with the highest hydraulic conductivity did not show erosion for any modelled rainfall intensity nonetheless we conclude that sheet and rill erosion were not the principal mechanism for rain triggered lahars associated with the cordon caulle eruption but mostly shallow landslide and similar erosion mechanisms contributed to lahars in villa la angostura in fact the eroded volumes calculated with lisem are significantly smaller than the volume calculated with shallow landslide models for the same catchments trigrs

sulfur and oxygen isotope fractionation during sulfate reduction coupled to anaerobic oxidation of methane is dependent on methane concentration highlights naturally enriched aom biomass was studied in high pressure continuous incubation we report the first s and o isotope fractionation values by sulfate reduction coupled to aom from culture studies there is a tight link between methane concentration and s and o isotope fractionation s and o isotope fractionation values indicate reversibility of energy limited microbial processes the wide range of environmental s and o isotope signatures can be explained abstract isotope signatures of sulfur compounds are key tools for studying sulfur cycling in the modern environment and throughout earth s history however for meaningful interpretations the isotope effects of the processes involved must be known sulfate reduction coupled to the anaerobic oxidation of methane aom sr plays a pivotal role in sedimentary sulfur cycling and is the main process responsible for the consumption of methane in marine sediments thereby efficiently limiting the escape of this potent greenhouse gas from the seabed to the overlying water column and atmosphere in contrast to classical dissimilatory sulfate reduction dsr where sulfur and oxygen isotope effects have been measured in culture studies and a wide range of isotope effects has been observed the sulfur and oxygen isotope effects by aom sr are unknown this gap in knowledge severely hampers the interpretation of sulfur cycling in methane bearing sediments especially because unlike dsr which is carried out by a single organism aom sr is presumably catalyzed by consortia of archaea and bacteria that both contribute to the reduction of sulfate to sulfide we studied sulfur and oxygen isotope effects by aom sr at various aqueous methane concentrations from 1 4 0 6 mm1 4 0 6 mm up to 58 8 10 5 mm58 8 10 5 mm in continuous incubation at steady state changes in the concentration of methane induced strong changes in sulfur isotope enrichment view the mathml sourcees34 and oxygen isotope exchange between water and sulfate relative to sulfate reduction o o as well as sulfate reduction rates srr smallest view the mathml sourcees34 21 9 1 9 21 9 1 9 and o o 0 5 0 20 5 0 2 as well as highest srr were observed for the highest methane concentration whereas highest view the mathml sourcees34 67 3 26 1 67 3 26 1 and o o 2 5 1 52 5 1 5 and lowest srr were reached at low methane concentration our results show that view the mathml sourcees34 o o and srr during aom sr are very sensitive to methane concentration and thus also correlate with energy yield in sulfate methane transition zones aom sr is likely to induce very large sulfur isotope fractionation between sulfate and sulfide i e 60 60 and will drive the oxygen isotope composition of sulfate towards the sulfate water oxygen isotope equilibrium value sulfur isotope fractionation by aom sr at gas seeps where methane fluxes are high will be much smaller i e 20 to 40

the role of debris supply conditions in predicting debris flow activity debris flow frequency and magnitude were determined for 33 basins in southwest british columbia basins were first classifiedaseitherweathering limitedortransport limitedusingadiscriminantfunctionbasedondebris contributingarea an area weighted terrain stability number and drainage density multiple regression was used to predict magnitude peak discharge frequency and activity frequency times magnitude within each group of basins model performance was improved by stratifying the total sample of debris flow basins into weathering and transport limited groups explained varianceincreasedbyanaverageof15percentinthetransport limitedsample indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge predictionofdebrisflowfrequency provedproblematicalinweathering limitedbasins themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available copyright 1999 john wiley sons ltd

diagenetic controls on the isotopic composition of carbonate associated sulphate in the permian capitan reef complex west texas late palaeozoic age strata from the capitan reef in west texas show facies dependent heterogeneity in the sulphur isotopic composition of carbonate associated sulphate which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater however diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate associated sulphate these processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest outer shelf shelf margin and slope depositional settings this study used a new multicollector inductively coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures carbonate rocks representing peritidal facies in the yates and tansill formations preserve the sulphur isotopic composition of guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes however sulphur isotopic data indicate that limestones deposited in reef and slope facies in the capitan and bell canyon formations largely incorporate sulphate from anoxic marine phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction despite generally preserving the carbon and oxygen isotopic compositions of permian seawater some early and all late meteoric calcite cements have carbonate associated sulphate with sulphur isotopic compositions distinct from that of permian seawater detailed petrographic and sedimentary context for carbonate associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms the results of this study indicate that carbonate rocks that diagenetically stabilize in high energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater s sulphur isotopic composition

isotope fractionation by sulfate reducing natural populations and the isotopic composition of sulfide in marine sediments isotope fractionations during sulfate reduction by natural bacterial populations were measured in seven different marine sediments and compared with the isotopic composition of solid phase sulfides in the same sediments the measured fractionations during sulfate reduction could explain only between 41 and 85 of the 34s depletion in the sedimentary sulfides this result directly demonstrates that the depletion of 34s in solid sulfides is an expression of the combined activity of sulfate reducing organisms with additional fractionations accumulated during the oxidative part of the sulfur cycle the only known process to significantly augment the fractionations created during sulfate reduction is the microbial disproportionation of the intermediate sulfur compounds elemental sulfur thiosulfate and sulfite in a simple model we show how important each of these disproportionation processes could be in generating the isotopic composition of sedimentary sulfides the sulfate reduction rates in the sediments studied varied by a factor of 1000 and did not correlate with the fractionation during sulfate reduction by contrast a correlation was observed between sulfate reduction rate and the extent of 34s depletion into sedimentary sulfides the most 34s depleted sulfides found in sediments supporting the lowest rates of sulfate reduction thus the fractionations imposed during the disproportionating processes are better expressed in sediments with low sulfate reduction rates the direct phototrophic oxidation of sulfide to sulfate with minimal fractionation may have been important in the sediments that had a high sulfate reduction rate

physically based modelling of soil erosion induced by rainfall in small mountain basins abstract in coarse grained unsaturated soils heavy rainstorms may cause either shallow landslides or superficial soil erosion the triggering of both of these phenomena is related to infiltration runoff and overland flow which are key processes requiring investigation in particular the quantitative estimates of the sediment yield at the outlet of mountain basins requires suitable physically based modelling in this paper the available approaches to soil erosion analysis are first reviewed and the capabilities and limitations of a physically based model are then evaluated through a case study of two small mountain basins the results obtained are in good agreement with those in the literature and with specific field data from a test area specifically for distinct realistic rainfall scenarios soil suction is found to be a key factor in the spatial temporal evolution of infiltration and runoff inside a mountain basin and soil suction and rainfall intensity greatly influence the total peak discharge of water and sediments the maximum volumetric concentration of sediments transported by water to the outlet of a mountain basin is found to be primarily related to the basin s specific morphometry

micromechanical modelling of rainsplash erosion in unsaturated soils by discrete element method abstract the rainsplash erosion is one important mechanism in natural and artificial slopes and the raindrops impact contributes to the amount of solids conveyed at the outlet of a mountain basin rainsplash erosion involves individual or small clusters of soil particles it is a dynamic temporally and spatially variable process and mainly occurs in unsaturated soils where capillarity forces allow steep slopes to be stable the discrete element method dem was firstly applied in this paper for the analysis of rainsplash erosion assuming realistic rainfall intensities and a range of both slope steepness and capillary forces in a parametric analysis the dem numerical results highlight the specific role of the slope steepness capillarity force and rainfall intensity towards the final volume of the solid eroded from the ground surface at the computational domain it is also valuable that the numerical results are in good agreement with literature formulations and increasing power law functions were found to relate well the eroded volume to rainfall intensity

tectonic history from vitrinite reflectance summary the degree of organic metamorphism of carbonaceous matter is expressed in terms of the reflectance of vitrinite vitrinite reflectance is a function of temperature and time a model relating vitrinite reflectance to temperature and time is proposed from published vitrinite reflectance temperature time nomograms a plot of the logarithm of vitrinite reflectance versus depth gives a linear curve for vitrinite reflectance greater than 0 3 per cent in a sedimentary basin which has had a constant geothermal gradient throughout its tectonic history the geothermal gradient c km 1 is equal to the slope of the curve multiplied by 194 8 the model is also applied to sedimentary basins with decreasing geothermal gradient with time i e cooling continental margin basins the vitrinite reflectance model is demonstrated to be consistent with observed reflectance data and tectonic information from the sydney bowen surat and gippsland basins in eastern australia

regional coalification pattern of lower cretaceous coal bearing strata rocky mountain foothills and foreland canada implications for future exploration abstract the regional coalification pattern of lower cretaceous strata in parts of the canadian foothills belt and adjacent foreland has been determined by vitrinite reflectance measurements the present study focusses on two coal bearing sequences bluesky gething and gates formation both of which contain coal resources of economic interest the vitrinite reflectances r max in the bluesky gething formation range from 0 76 high volatile a bituminous to 2 55 semianthracite rank changes from top to the base of bluesky gething formation follow 1st order regression lines factors influencing the rate of increase of r max per depth interval coalification gradient include paleogeothermal gradients the rank level under investigation conductivities of host rocks and thicknesses of coal seams time depth burial curves for the lower cretaceous bluesky gething formation suggest that the regional coalification pattern for the top of the formation results largerly from variations in the depth and or duration of burial beneath maastrichtian tertiary foredeep deposits coalification largerly predates deformation the coalification pattern is more complicated for the base of the bluesky gething formation because thickness changes in the lower cretaceous bluesky gething interval locally have a greater effect on the rank than does the regional change in the thickness of maastrichtian tertiary sedimentary wedge detailed rank studies on laterally continuous coal seams of the gates formation showed that coalification levels were largerly established before folding and thrusting started isoreflectance lines of the beds run parallel to the bedding of the folded strata seams collected from various thrust sheets exposed at surface do not in general show significant changes in vitrinite reflectances from one thrust sheet to another many of the coals of the gates formation were found to have biaxial negative reflectance in dicatrices orientation of r max is in all cases parallel of subparallel to the mactroscopic fold axes indicating preferential orientation of the aromatic lamellae in the coals in the direction of minimum compressive stress it is suggested that the occurrence of biaxial negative coals is related to a tectonic stress field that existed during the later stages of burial and subsequent deformation

optical anisotropy of coals as an indicator of tectonic deformation broad top coal field pennsylvania the anisotropic reflectance fabric of coal is used as a finite strain marker in the structural analysis of deformed strata in the broad top coal field of central pennsylvania oriented blocks of coal were collected at various field locations the reflectances of three orthogonal surfaces were used to estimate the magnitudes and orientations of the three principal reflectance axes broad top coals are shown to have three principal reflectance values in contrast with most bituminous coals which have only two reflectance values can be represented by a biaxial indicatrix that may be either prolate or oblate the oblate indicatrices showing flattening in the bedding plane are associated with gently deformed strata the prolate indicatrices elongated parallel to the fold axes n32 e are associated with more intensely folded strata and show the influence of strong lateral compression superimposed upon gravitational loading the reflectance indicatrices maintain a constant spatial orientation regardless of the inclination of the enveloping bedding the minimum principal reflectance axis plunges steeply toward the west indicating that during deformation the direction of maximum compression was plunging toward the northwest these results suggest that in the broad top field maximum coalification and therefore maximum burial were penecontemporaneous with the later stages of deformation postdating most of the folding

landslide zoning over large areas from a sample inventory by means of scale dependent terrain units abstract a procedure is proposed to produce landslide distribution zoning maps to be considered preparatory to susceptibility hazard and risk zoning maps based on 1 the results from a statistical multivariate analysis of a landslide inventory which must be available for only a portion of the territory to be zoned and 2 the use of appropriately defined terrain mapping units the units are divided into terrain computational units tcus and terrain zoning units tzus whose size is related to the scale of zoning the procedure comprises three phases calibration validation and prediction the purpose of the prediction phase is the application of a calibrated and validated statistical model in a territory previously recognized as viable on the basis of a priori applicability maps for which no information is available regarding the distribution of landslides or where the information provided by the landslides inventory is unreliable or heterogeneous the proposed procedure is applied to two case studies in southern italy for the analysis and zoning of slow moving landslides at 1 25 000 and 1 100 000 scales respectively the first case study illustrates the applicability of the procedure the aim of the second case study is to address the part of the procedure related to the evaluation of the computational maps at the end of the calibration and validation phases

the impact of diffusive transport of methane on pore water and sediment geochemistry constrained by authigenic enrichments of carbon sulfur and trace elements a case study from the shenhu area of the south china sea abstract sulfate driven anaerobic oxidation of methane sd aom controls methane release from marine sediments to the ocean a variety of authigenic precipitates within sediments has been widely used to identify past occurrences of sd aom however the lack of a systematic evaluation of the formation conditions of these precipitates sometimes impedes the recognition of sd aom in past environments characterized by diffusive transport of methane carbon sulfur and trace element geochemistry of pore water and sediments was investigated at a site affected by upward methane diffusion in the shenhu area of the south china sea here the sulfate methane transition zone smtz is located 7 6 m below the seafloor based on sulfate and methane concentrations the slope of 34s vs 18o values of sulfate is consistent with diffusive transport of methane concentration and isotope profiles of pore water species point to diffusive rather than advective transport of solutes enhanced sulfate reduction inferred from 34s values of sulfate agrees with the local occurrence of relatively abundant 34s enriched iron sulfide minerals the time required to produce the observed authigenic iron sulfides around the smtz is estimated to be 1 1 ka based on the amount of iron sulfide minerals and the present diffusive flux of sulfate no enrichment of authigenic carbonate barium ba and molybdenum mo was detected in the studied sediments this observation is consistent with the calculation that the current fluxes of pore water calcium magnesium ba and mo are too low to allow for authigenic enrichments the low fluxes are largely controlled by diffusion which facilitates the formation of 34s enriched iron sulfide minerals the observed enrichment patterns unlike those of sediments affected by advective seepage are expected to be prevalent in modern and ancient continental margin sediments and may contribute to the identification of past methane rich zones and overlying sd aom zones as sinks for methane in the geological record

on erosion characteristics of compacted loess during wetting procedure under laboratory conditions the erosion of engineered slope surfaces has become an urgent problem in loess regions in china which has a serious impact on the safety and stability of the slope projects in this paper to study the effect of the confining pressure dry density of the slope surface and water flow velocity during wetting procedure on the erosion characteristics of compacted loess we developed a laterally confined uniaxial compression erosion apparatus which was characterized by the fact that it can change the confining pressure of the being eroded soil sample to analyze the loess erosion rates and particle size distributions of the eroded sediments the fractal dimensions of the eroded sediments were calculated by fractal theory and their variations were analyzed results show that the erosion rate is approximately linearly related to the confining pressure the higher pressure has a tendency to move towards the free top of soil sample the erosion rate increases compared with the water flow velocity the higher confining pressure plays a greater role in the erosion rate the influence of water flow velocity on the erosion rate decreases with the increase of dry density the erosion rate decreases the higher dry density enhances the ability of soil sample to resist water erosion the confining pressure changes the particle size distribution of the eroded sediments of loess samples the median diameter d50 increases however the fractal dimension decreases with the increase in confining pressure the confining pressure of slope surface has a negative effect on the loess anti erosion characteristics the results in this paper would provide detailed information on the mechanisms of loess erosion which could contribute toward prevention of surface erosion of high fill slopes in loess regions

unsteady diagenetic processes and sulfur biogeochemistry in tropical deltaic muds implications for oceanic isotope cycles and the sedimentary record abstract sedimentary s cycling is usually conceptualized and interpreted within the context of steadily accreting 1 d transport reaction regimes unsteady processes however are common in many sedimentary systems and can result in dramatically different s reaction balances and diagenetic products than steady conditions globally important common examples include tropical deltaic topset and inner shelf muds such as those extending from the amazon river 1600 km along the guianas coast of south america these deposits are characterized by episodic reworking of the surface seabed over vertical depths of 0 1 3 m reworked surface sediments act as unsteady suboxic batch reactors unconformably overlying relict anoxic often methanic deposits and have diagenetic properties largely decoupled from net accumulation of sediment despite well oxygenated water and an abundant reactive organic matter supply physical disturbance inhibits macrofauna and benthic communities are dominated by microbial biomass across immense areas in the surficial suboxic layer molecular biological analyses tracer experiments sediment c s fe compositions and 34s 18o of pore water so 4 2 indicate close coupling of anaerobic c s and fe cycles 18o so 4 2 can increase by 2 3 during anaerobic recycling without net change in 34s so 4 2 demonstrating so 4 2 reduction coupled to complete anaerobic reoxidation to so 4 2 and a 18o so 4 2 reduction reoxidation fractionation factor 12 summed magnitudes s reoxidation must be coupled to fe oxide reduction contributing to high dissolved fe2 1 mm and fe mobilization export the reworking of amazon guianas shelf muds alone may isotopically alter 18o so 4 2 equivalent in mass to 25 of the annual riverine delivery of so 4 2 to the global ocean unsteady conditions result in preservation of unusually heavy 34s isotopic compositions of residual cr reducible s ranging from 0 to 30 in physically reworked deposits in contrast bioturbated facies adjacent to physically reworked regions accumulate isotopically light s 34s to 20 in otherwise similar decomposition regimes the isotopic patterns of both physically and biologically reworked regions can be simulated with simple diagenetic models heavy s isotopic signatures are largely a consequence of unsteady diffusion and progressive anaerobic burndown into underlying deposits whereas isotopically depleted bioturbated deposits predominantly reflect biogenic diffusive scaling and isotopic distillation diffusive pumping associated with reoxidation in burrow walls immediately adjacent to reduced zones the s isotopic transition from unsteady physically controlled regions of the amazon delta moving laterally into bioturbated facies mimics the transition of s isotopic patterns temporally in the geologic record during the rise of bioturbation no special role for s disproportionation is required to explain these differences the potential role of unsteady suboxic diagenesis and dynamic reworking of sediments has been largely ignored in models of the evolution of surficial elemental cycling and interpretations of the geologic record

bacterial sulfur disproportionation constrains timing of neoproterozoic oxygenation various geochemical records suggest that atmospheric o 2 increased in the ediacaran 635 541 ma broadly coincident with the emergence and diversification of large animals and increasing marine ecosystem complexity furthermore geochemical proxies indicate that seawater sulfate levels rose at this time too which has been hypothesized to reflect increased sulfide oxidation in marine sediments caused by sediment mixing of the newly evolved macrofauna however the exact timing of oxygenation is not yet understood and there are claims for significant oxygenation prior to the ediacaran furthermore recent evidence suggests that physical mixing of sediments did not become important until the late silurian here we report a multiple sulfur isotope record from a ca 835 630 ma succession from svalbard further supported by data from proterozoic strata in canada australia russia and the united states in order to investigate the timing of oxygenation we present isotopic evidence for onset of globally significant bacterial sulfur disproportionation and reoxidative sulfur cycling following the 635 ma marinoan glaciation widespread sulfide oxidation helps to explain the observed first order increase in seawater sulfate concentration from the earliest ediacaran to the precambrian cambrian boundary by reducing the amount of sulfur buried as pyrite expansion of reoxidative sulfur cycling to a global scale also indicates increasing environmental o 2 levels thus our data suggest that increasing atmospheric o 2 levels may have played a role in the emergence of the ediacaran macrofauna and increasing marine ecosystem complexity

recognition classification and mechanical description of debris flows abstract various types of flow or mass movement involving water and sediments occur on steep slopes in mountainous areas among them debris flows are peculiar events during which a large volume of a highly concentrated viscous water debris mixture flows through a stream channel throughout the world these phenomena cause considerable damage but remain poorly understood although a basic knowledge is already available concerning their recognition and propagation firstly a synthesis of the useful practical criteria of recognition is proposed debris flows must be seen as intermediate phenomena between hyperconcentrated flows intense bed load transport and landslides separated from them by sharp transitions of some characteristics celerity deposit nature and flow type two parameters solid fraction and material type thought to be appropriate for a sound and practical classification are brought out and the corresponding complete classification of flow and mass movements in mountain areas is presented two extreme debris flow types are thus distinguished muddy debris flows and granular debris flows a critical review of recent advances in debris flow dynamic is then proposed it is pointed out that adequate work must be carried out in the field of non newtonian fluid mechanics in particular one fundamental rheological property of debris flow materials is the yield stress which explains thick deposits on steep slopes and can be inferred from field measurements furthermore it can be used to estimate viscous dissipation within the bulk during flow relevant models predicting muddy debris flow dynamics are already available whereas further progress is needed concerning granular flows

slope stability models for rainfall induced lahars during long lasting eruptions abstract in this study we analyse the spatial distribution of potential lahar sources during long lasting eruptions using two slope stability models shalstab and trigrs the analysis is based on observed deposit grain size and thickness rainfall data and slope angle of the lahar events in the area surrounding the cordon caulle volcano chile that occurred during the 2011 eruption the main phase of the eruption 4 7 june was characterized by eruptive plumes from 7 to 11 km high which dispersed most of the tephra eastward toward argentina with a total estimated volume of about 1 km3 tephra fallout blanketed the region from ese to ene of the volcano with the thickness of the tephra fallout layers between approximately 1 m 15 km from vent and 0 06 m 240 km from the vent on 10 june 2011 a major lahar occurred close to the argentina chile border that reached the national road 231 28 km from the vent three field campaigns were undertaken to collect samples and data from tephra fallout deposits and triggering mechanisms in the lahar source area model input parameters were obtained from geotechnical tests and field measurements several metrics were used for model evaluation and best fit to the data were obtained for simulations considering non cohesive ash layers for shalstab and a cohesion of 0 5 kpa for trigrs both models are sensitive to the physical properties of the tephra fallout deposit and the hydraulic and materiel strength properties of the study area they both also show good agreement with field data but provide different information trigrs provides an estimate of the timing based on a storm event and location of a potentially unstable area while shalstab simulations result in landslide susceptibility classes based on critical rainfall value these outcomes provide fundamental insights into lahar triggering during long lasting volcanic eruptions and are crucial to the compilation of lahar hazard maps and emergency management plans in the south andes volcanic region

sulfur diagenesis under rapid accumulation of organic rich sediments in a marine mangrove from guadeloupe french west indies the biogeochemistry of sulfur and carbon during early diagenetic processes within organic rich marine mangrove sediments was studied in the manche a eau lagoon guadeloupe west indies these sediments are characterized by a total organic carbon content toc mostly above 11 wt 13ctoc below 25 vpdb and c nmolar ratios exceeding 15 rates of mangrove derived organic carbon accumulation vary between 200 and 400 goc m 2 yr 1 with highest rates at the shore of the lagoon on the lagoon border where colorless filamentous sulfur oxidizing bacteria colonize the sediments active sulfate reduction within the upper 20 cm with a net removal rate of 0 5 mol cm 3 d 1 is assumed to be essentially driven by organic carbon oxidation this is expressed by relatively low apparent sulfur isotope fractionation 34enet 33 and a gentle 18o 34ssulfate apparent slope of 0 36 0 03 2s further inside the lagoon in the absence of sulfur oxidizing bacteria higher apparent sulfur isotope fractionation and a steeper 18o 34ssulfate slope 0 67 0 20 suggest an overall lower sulfate removal rate that may be coupled to minor sulfur disproportionation spatial and vertical variation in sulfur cycling reflected by oxygen and sulfur isotopic characteristics seem to be mainly controlled by unsteady to relatively steady organic matter deposition and its reactivity in all sediments 34s values of pyrite are positively correlated with the toc ts ratio and negatively correlated with 13ctoc suggesting a primary control of the quantity and quality of organic matter on the pyrite isotope records despite potential iron limiting conditions for the most active sites our results provide insights into the role of organic carbon input on sulfur cycling stimulating sulfate reduction and in turn the presence of sulfur oxidizing microbial mats resulting in an intense cycling of both carbon and sulfur in these marine mangrove sediments

offset of an upper pliensbachian geographic zonation in the north american cordillera by transcurrent movement the north to south climatic zonation of upper pliensbachian ammonites known in europe has been recognized in the north american cordillera this simple geographic arrangement has been disrupted by northwest trending dextral transcurrent faults with further documentation the amount of offset of these zones should provide a measure of the amount of movement on these faults since pliensbachian time and further document the allochthoneity of the western part of the cordillera

sulfidization processes in seasonally hypoxic shelf sediments a study off the west coast of india abstract continental shelves are the major sites for organic carbon burial and sulfate reduction organic carbon degradation and sulfidization along continental shelves are expected to play a significant role in global carbon sulfur iron c s fe cycles here we report sediment pore water chemistry and iron sulfur speciation in two short cores ssk 42 9 and 10 collected off malvan from the seasonally hypoxic shelf region off the west coast of india wci at water depths of 30 and 13 m respectively concentration profiles of pore water so42 nh4 dic hs and depth integrated sulfate reduction rates jso4 suggest a variable influence of sedimentation rates the composition of organic matter marine and terrestrial and anaerobic oxidation of methane aom on the pore fluid chemistry chromium reducible sulfur crs and organic bound sulfur obs are the detectable solid phase sulfur species in the studied sediment cores sulfur content and isotope ratios of chromium reducible sulfur crs and organic bound sulfur obs phases produced via hs sx2 pathways sulfidization and sulfurization show contrasting profiles in ssk42 9 and 10 apparently influenced by the availability of reactive iron the relative significance of early and late diagenetic processes source of obs detritus of marine origin and sulfurized organic molecules and diffusion of hs produced via aom across the smtz the marked influence of aom driven sulfate reduction and the diffusion of isotopically enriched hydrogen sulfide across the sulfate methane transition zone smtz is apparent from the 34scrs profiles in ssk 42 10 sediment toc ts ratios recorded in this study are significantly less than that of average modern marine surface sediments 2 8 1 underlying oxygenated water and this is attributed to the enhanced sulfidization and burial of iron sulfur minerals in the seasonally hypoxic regions since the inner shelf of wci experiences seasonal alternation from normoxia to hypoxia which may have a profound influence on the benthic community structure nature and depth of bioturbation bioirrigation we propose that the impact of these processes need to be studied at a significantly higher resolution for better understanding c s fe biogeochemical cycle

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

the early diagenetic formation of organic sulfur in the sediments of mangrove lake bermuda due to a low mineral content the sapropelic sediments depositing in mangrove lake bermuda provide an excellent opportunity to explore for possible additions of sulfur to organic matter during the early stages of diagenesis we evaluated early diagenetic organic sulfur transformations by monitoring the concentrations and stable isotopic compositions of a number of inorganic and organic sulfur pools thereby accounting for all of the sulfur in the sediments we have identified and quantified the following sulfur pools porewater sulfate porewater sulfide elemental sulfur pyrite sulfur hydrolyzable organic sulfur hyos chromium reducible organic sulfur cros and nonchromium reducible organic sulfur non cros of the organic sulfur pools the non cros pool is by far the largest followed by cros and finally hyos by 60 cm depth these pools contribute respectively to 85 7 9 and 3 6 of the total solid phase sulfur the hyos pool is probably of biological origin and shows no interaction with the sulfur compounds produced during diagenesis by contrast cros is produced most likely from the diagenetic addition of polysulfides to functionalized lipids in the upper h2s poor elemental sulfur rich region of the sediment a portion of this sulfur pool is unstable and decomposes on contact with the h2s rich porewaters the portion of cros that remains in the sulfidic waters appears to readily exchange sulfur isotopes with h2s while some of the non cros pool is of biological origin some is also formed by the diagenetic addition of sulfur to organic compounds in the upper h2s poor region of the sediment by contrast with cros non cros is not diagenetically active in the h2s rich porewaters overall somewhere between 27 and 53 of the organic sulfur buried in mangrove lake sediments is of diagenetic origin with the remaining organic sulfur derived from biosynthesis we extrapolate our mangrove lake results and calculate that in typical coastal marine sediments between 11 and 29 mol g 1 of organic sulfur will form during early diagenesis of which 2 5 mol g 1 will be chromium reducible

hypersulfidic deep biosphere indicates extreme sulfur isotope fractionation during single step microbial sulfate reduction coexisting dissolved sulfide and sulfate from hypersulfidic interstitial waters of a 380 m long sediment core show a large isotopic difference of up to 72 caused by in situ microbial sulfate reduction this is considerably larger than the assumed biological maximum of 46 derived from laboratory studies with pure cultures of sulfate reducing bacteria similar high fractionations inferred from sedimentary metal sulfides have been previously explained by a multistage process involving sulfide reoxidation and disproportionation of sulfur intermediates our data show that extreme isotopic differences between sulfate and the reduced sulfur species can also be generated during microbial single step fractionation this result indicates that the sulfate reducing communities and or their cellular metabolic activities in the deep biosphere may differ from those observed in near surface sediments or the water column

environmental evolution of the east china sea inner shelf and its constraints on pyrite sulfur contents and isotopes since the last deglaciation abstract to better understand the depositional constraints on the sulfate reduction process we present a set of sulfur isotope data for hand picked pyrites 34spyr from the coarse fraction 63 250 m of bulk sediments coupled with the contents of carbonate total organic carbon toc and nitrogen tn as well as 13c values of the toc from sediments of core ec2005 on the inner shelf of the east china sea ecs since 16 4 ka our results show that core sediments were deposited in a terrestrial environment before 13 1 ka stage i when pyrite rarely occurred during stages ii 13 1 12 3 ka and iii 12 3 12 1 ka seawater began to influence the core location forming a tidal flat environment where abundant pyrites are well preserved then the inner shelf of the ecs was fully flooded and two intervals with high stage iv 12 1 6 0 ka stage vi 5 2 1 5 ka and low sedimentation rate stage v 6 0 5 2 stage vii 1 5 ka present are identified respectively when compared with previous 34s values of chromium reducible sulfur 34scrs derived from the bulk sediments 34spyr values are usually higher indicating the macroscopic pyrites form in the later stages of sedimentary diagenesis when ongoing sulfate reduction has distilled porewater sulfate to a high degree considering the wide occurrence of biogenic shallow gas dominated by ch4 in these sediments sulfate driven anaerobic oxidation of methane so4 aom and organoclastic sulfate reduction osr are expected to be two competitive pathways for sulfate reduction we propose that the changes in sedimentation rate controls the pace of migration of the sulfate methane transition zone smtz when sedimentation rate is low the smtz may be fixed in a certain depth e g sediments deposited in stage iii and v where h2s is produced by so4 aom in contrast when sedimentation rate is very high 1 cm yr the smtz would be deep and h2s is mostly produced by osr further our results imply that sulfur diagenesis in recent since 1 5 ka ecs mud sediments might be influenced by physical reworking e g typhoon and or biological activity bioturbation resulting in partial reoxidation of pyrite crystals in fluid mud our findings therefore demonstrate that pyrite sulfur isotope compositions bulk 34scrs hand picked 34spyr are sensitive to local environmental evolution and the combined use of these two indicators can provide new insights into pathway of sulfate reduction in unsteady environments

removal of methane through hydrological microbial and geochemical processes in the shallow sediments of pockmarks along eastern vestnesa ridge svalbard the recent discovery of methane seeps in the arctic region requires a better understanding of the fate of methane in marine sediments if we are to understand the contributions of methane to arctic ecosystems and climate change to this goal we analyze pore water data from five sites along eastern vestnesa ridge a sediment drift off north west svalbard to quantify the consumption of dissolved methane across the sulfate methane transition zone which are 3 5 m below seafloor from the investigated sites we use transport reaction models to quantify the hydrology as well as the carbon mass balance in the sediments pore water profiles and our model results demonstrate that hydrological microbial and geochemical processes reactions efficiently remove methane carbon from fluid over different time scales we interpret the nonsteady state behavior of the first 50 70 cm of our pore water profiles from the active sites as an annual scale downward fluid flow due to a seepage related pressure imbalance such downward flow supplies sulfate which enhances methane consumption through anaerobic oxidation of methane aom within this depth range our steady state modeling confirms the efficiency of aom in consuming dissolved methane in the upper 0 8 1 2 m of sediments based on the phosphate profiles we estimate that aom at the active pockmarks may have been operating for the last two to four centuries precipitation of authigenic carbonate removes more than a quarter of the dissolved inorganic carbon produced by aom and fixes it as authigenic carbonate in the sediments a process that sequestrates methane carbon over geological time

some aspects of the initiation of debris avalanches in the campania region the role of morphological slope discontinuities and the development of failure abstract in may 1998 a prolonged period of rainfall caused disastrous landslides in the sarno quindici area campania southern italy the landslides initiated as small debris slides and developed into debris avalanches and debris flows involving the shallow pyroclastic deposits that lie on the steep vegetated slopes of this area in view of the potential for such events to occur again in this area an understanding of the initial failure mechanism is crucial if assessments are to be made of the hazard levels in this paper the results of detailed surveys of the morphological characteristics of the source areas are presented statistical analyses and parametrical relationships have been performed on key parameters demonstrating that the initial failures were associated with the presence of morphological discontinuities such as limestone scarps and road cuts notably the presence of man made cuts appears to have been responsible for about the 60 of the initial debris slides morphometric analysis has shown that the debris avalanches are characterised by a typical triangular shape statistical analyses have been used to try to relate the apex angles to relevant geomorphological parameters allowing for differences in local morphology the findings show some significant correlation

spatial and temporal occurrence of rainfall induced shallow landslides of flow type a case of sarno quindici italy article i nfo rainfall induced shallow landslides of flow type provide unstable masses which often travel long run out distances with high velocities thus posing a high societal risk when they affect large areas therefore analysis of their spatial and temporal occurrence is relevant to landslide hazard assessment as the first step of the risk analysis in order to address this issue this paper outlines a multidisciplinary procedure that is applied to the may 1998 sarno quindici landslides southern italy whose spatial and temporal occurrence is not satisfactorily addressed in current literature the spatial occurrence of the landslides is analysed using heuristic models for both the source and propagation areas the temporal occurrence of the landslides is firstly compiled and then related to the cumulated rainfall stratigraphy and hydraulic boundary conditions finally the spatial and temporal occurrence of the main landslide triggering mechanism is modelled over the whole affected area by analysing the groundwater regime and slope stability conditions the obtained results show that the spatial and temporal occurrence is strongly related to stratigraphy and hydraulic boundary conditions at both the slope and massif scales they also highlight a suitable procedure for assessing the spatial and temporal occurrence of complex landslides over large areas