x ray microanalysis of fluid inclusions and its application to the geochemical modeling of evaporite basins direct access to brines trapped in halite is possible by freezing and breaking halite crystals on a cooling stage inside a scanning electron microscope quantitative analyses of major solutes na mg k ca cl and so4 in natural brines were obtained by means of x ray microanalysis of the frozen fluid inclusions using frozen droplets of brines with known composition as standards precision errors were estimated to be lower than 10 and detection limits vary from below 0 02 mol l for ca k and so4 to 0 55 mol l for na analyses of several inclusions of sizes larger than 20 m were performed for each cross section of halite the composition of primary fluid inclusions in halites from a drill core in the messinian basin of lorca se spain were used to constrain the parameters of a geochemical model of the evolution of the basin a computer program to simulate evaporation paths was developed using thermodynamic equilibrium and mass balance as constraints the halite sequence was interpreted as resulting from the evaporation of initial seawater in a hydrologically open basin with seawater replacing the evaporated water and a small fraction of basinal brine leaking out in the middle of the sampled sequence the basin was closed to the sea and only continental water flowed into the basin reworking part of the halite deposited in the margins in contrast with these results only very poor information would have been obtained from the mineralogical record alone consisting mainly of halite and minor gypsum

green river laminites does the playa lake model really invalidate the stratified lake model proponents of the playa lake model have proposed deposition of most of the green river formation microlaminated carbonates including oil shales in lakes that were not perennially stratified meromictic however there is a variety of evidence favoring a meromictic depositional environment 1 close similarity of much of the lamination to varves in modern meromictic lakes 2 evidence that hydrologic events favoring development of meromixis chemical stratification occurred prior to deposition of major accumulations of oil shale 3 mutually exclusive distribution of fossil nekton especially fish and normal lacustrine benthos including mollusks and 4 analogy with a quaternary playa that became a meromictic lake following increased inflow the playa lake model is untenable for the typical fish bearing kerogen rich microlaminated sediments these laminites were probably deposited in a large ectogenic meromictic lake a chemically stratified lake that formed when increased fresh water inflow drowned a saline playa complex

morphology structure and flow phases in soil pipes developing in forested hillslopes underlain by a quaternary sand gravel formation hokkaido northern main island in japan preferential flow pathways such as soil pipes are usually present in the soil of slopes subsurface flow through the soil pipes affects the subsurface drainage system and is responsible for sediment removal from slopes however a record of the inner structure of soil pipes has rarely been reported for slopes a fibrescope examination of the morphology and flow phases in soil pipes in hillslopes underlain by a quaternary sand gravel formation provided the following information the main pores of the soil pipes ran mostly parallel with the slope gradient the cross sections of the soil pipes were approximately circular and occurred on a few occasions with some triple junctions being present in addition both full flow and partly full depth conditions occurred simultaneously in the soil pipe the full flow condition has long been used in hydrological studies to model the pipe flow mechanism both the full flow condition and the partly full depth condition however must be examined closely in order to evaluate the subsurface hydrology in heterogeneous soil and the hydrogeomorphological processes of subsurface hydraulic erosion copyright 2000 john wiley sons ltd

changes in gas composition during simulated maturation of sulfur rich type ii s source rock and related petroleum asphaltenes abstract asphaltenes extracted from crude oils are proposed to possess structural features of the related source rock kerogen for the present study micro scale sealed vessel pyrolysis mssv and combustion isotope ratio mass spectrometry gc c irms were used to compare gas generation from a whole rock type ii s kerogen from southern italy with that from related sulfur rich asphaltenes isolated from a low maturity heavy crude oil the purpose of was to determine whether experimental pyrolysis of oil asphaltenes can be used to predict the timing and the chemical and isotopic composition of hydrocarbon gases generated from genetically related kerogen in the source rock during burial maturation the results show that parameters such as gas to oil ratio gor and oil and gas formation timing are very similar for these two sample types whereas gas composition product aromaticity and sulfur content are remarkably different slight differences in gor are mainly due to differences in gas formation characteristics at very high levels of thermal alteration secondary gas formation from the whole rock covers a much broader temperature range under geological conditions than that from the asphaltene products however it is remarkable that both the onset and the maximum temperature are nearly identical under geological conditions the observed differences in gas generation characteristics are supported by discrepancies in the carbon isotopic characteristics of the gas range compounds and indicate different precursors and or mechanisms for gas generated from whole rock and asphaltenes

association of redeposited salt breccias and potash evaporites in the lower miocene of stebnyk carpathian foredeep west ukraine abstract potash evaporites of the lower miocene vorotyshcha suite are sandwiched in salt breccias in the ukrainian part of the carpathian foreland basin these breccias have traditionally been interpreted as tectonically deformed units related to the overthrust nappes of the carpathians most clasts consist of intrabasinal sandstone marlstone halite and anhydrite but exotic clasts consisting of rocks that are characteristic of the carpathian flysch rocks are also present breccia beds are intercalated with salt layers containing chevron crystals and cubic hopper crystals and some layers are composed of detrital salt these salt layers rarely display graded bedding or cross lamination and continue over great distances there are also slump structures associated with the bedded salts the salinity in the vorotyshcha basin was extremely high but intermittent inflows caused brine dilution so that it could maintain halite precipitation for a long time during long periods of evaporative concentration and reduced inflow brines in the basin could reach the sylvite saturation level so that potash chlorides and sulfates started to precipitate the potash precipitated subaqueously on the basis of evidence from the study of fluid inclusions the depth of the brine is interpreted to have been 20 30 m in agreement with the supposed brine stratification in a basin subjected to influxes of sediment laden waters the breccias are debris flow deposits they are commonly tectonically deformed but analysis of the relation of breccias to evaporites suggests that both were formed in water ten to a few tens of meters deep it therefore seems that halite breccias in other foreland basins could have had a sedimentary origin

petrographical and organic geochemical study of the kovin lignite deposit serbia abstract the origin of the organic matter om and the characteristics of the depositional environment of lignites from the upper miocene kovin deposit hosting three coal seams of serbia were evaluated based on petrographic data bulk organic geochemical parameters biomarker analysis and stable isotope geochemistry 13c of individual biomarkers samples were collected from four boreholes gd 601 and gd 603 the a field and kb 79 and kb 91 the b field representing different parts of coal seams i ii and iii investigated lignites are typical humic coals the om of lignites is derived from woody vegetation and herbaceous peat forming plants with prevalence of the former in most samples peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by a low amount of angiosperms lignite forming plants mostly belonged to the gymnosperm families cupressaceae taxodiaceae phyllocladaceae and pinaceae slight input of ferns fungi and aquatic macrophyta to lignite om is also evident distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic chemoautotrophic and heterotrophic bacteria during diagenesis prominent c28 28 30 bisnorneohop 13 18 ene was observed for the first time in the lignite extracts according to the 13c value it was probably derived from chemoautotrophic bacteria c28 28 30 bisnorneohop 13 18 ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at c 21 via progressive aromatization peatification proceeded in a fresh water environment under variable redox conditions from anoxic to slightly oxic all three coal seams are heterogeneous the lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas which was subjected to inundations the upper parts of coal seams represent a wet forest swamp with relatively stable conditions despite the observed variations in all three coal seams the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam iii to seam i maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams relatively frequent variations in all three coal seams followed by repetition of lignite characteristics depict well the pronounced seasonality e g short term cycles of the climate during late miocene in investigated area

pipes and pipe flow process in an upland catchment wales abstract the results of observations on the spatial localisation origin and function of soil pipes in an upland catchment are discussed the pipes occur in distinct zones in the brown earth soils of the lower slopes and form a hydrological link conducting water between an upslope zone of highly permeable skeletal soils and the stream channel it is proposed that in this catchment pipes develop from an initial network of mole burrows modified by hydraulic activity to produce an efficient downslope transmission network a conceptual model for the pipe slope segment is proposed which recognises the importance of this transmission role slope discharge controls switching between saturated throughflow pipe flow and overland flow each of which has a specific threshold value for operation attempts to investigate the significance of pipe flow at the catchment scale met with limited success but it appears to be important in increasing both contributing area and duration of storm flow

earthquake induced resedimentation in the badenian middle miocene gypsum of southern poland in the badenian middle miocene basin of the carpathian foreland of southern poland gypsum breccias occur associated with laminated gypsum deposits these breccias consist of large clasts of gypsum carbonates marls and clay chips of variable size embedded in a gypsarenitic matrix constituent gypsum grains and clasts commonly appear to be mechanically abraded and chemically corroded crystals or fragments of selenitic laminated and alabastrine gypsum gypsorudites are commonly accompanied by laminated gypsarenites and gypsolutites which show graded bedding a vertical sequence of graded gypsum beds showing bouma sequences may be recognized in borehole sections microfolding is common within the folded laminated gypsum and is closely associated with expressions of extensional strain both are accompanied by pervasive microfaulting suggesting a semi coherent downslope mass movement the stratiform geometry of the breccias together with the intensity of slumping relatively independent of the palaeoslope suggest earthquake shocks as the initial main cause gypsum deposits form a constant laterally extensive sequence of different lithofacies the occurrence of the same lithologies and shallowing up cycles over a wide area reflects thrusting of the carpathians over the carpathian foredeep local tectonism has also played a significant role the tectonic framework favoured activation of dip slip faults promoting shallow focus earthquakes these in turn resulted in the resedimentation of gypsum by slumps debris flows and turbidites a similar basinward resedimentation of clastic material by gravity flows initiated by fault induced earthquakes could be of great importance in the foreland geological setting and may explain some phenomena observed in other evaporite formations from different geological settings especially of rift type

origin of secondary potash deposits a case from miocene evaporites of nw central iran abstract in early miocene times an extensive carbonate shelf developed in central iran and during several cycles of sea level fluctuations evaporite bearing carbonate sequences of the qom formation were deposited however in the early middle miocene development of restricted marine conditions led to a facies change from shelf carbonates of the qom formation to the evaporite series of the m 1 member of the overlying lower red formation this member is a facies mosaic of lagoonal and salina evaporites mainly halite beds admixed with wadi siliciclastics the purpose of this study which focuses on two salt mines in the northwestern portion of central iran in the zanjan province was to reveal the origin sedimentary environment and diagenesis of these potash bearing evaporite sequences petrographic examination revealed the following mineral assemblage halite gypsum anhydrite and carnallite as primary precipitates and langbeinite and aphthitalite as secondary metamorphic potash salts in the iljaq mine distorted halite beds are dominated by burial and deformational textures and a great deal of secondary potash salts in the qarah aghaje mine however the bedded halite shows pristine primary textures and is devoid of the secondary potash salts high bromine content of most evaporite minerals suggests their marine origin and confirms the absence of the extensive meteoric alterations and subsequent bromine depletions potash salts are mainly secondary and resulted from diagenetic replacements of distorted halite beds during thermal and dynamic metamorphism in a burial setting

lipid biomarker and stable isotopic profiles through early middle ordovician carbonates from spitsbergen norway abstract one of the most dramatic episodes of sustained diversification of marine ecosystems in earth history took place during the early to middle ordovician period changes in climate oceanographic conditions and trophic structure are hypothesised to have been major drivers of these biotic events but relatively little is known about the composition and stability of marine microbial communities controlling biogeochemical cycles at the base of the food chain this study examines well preserved carbonate rich strata spanning the tremadocian through upper dapingian stages from the oslobreen group in spitsbergen norway abundant bacterial lipid markers elevated hopane sterane ratios average 4 8 maximum of 13 1 detection of chlorobi markers in organic rich strata and bulk nitrogen isotopes 15ntotal averaging 0 to 1 for the open marine facies suggest episodes of water column redox stratification and that primary production was likely limited by fixed nitrogen availability in the photic zone near absence of the c30 sterane marine algal biomarker 24 n propylcholestane 24 npc in most samples supports and extends the previously observed hiatus of 24 npc in early paleozoic late cambrian to early silurian marine environments very high abundances of 3 methylhopanes average 9 9 maximum of 16 8 extends this biomarker characteristic to early ordovician strata for the first time and may reflect enhanced and sustained marine methane cycling during this interval of fluctuating climatic and low sulfate marine conditions olenid trilobite fossils are prominent in strata deposited during an interval of marine transgression with biomarker evidence for episodic euxinia anoxia extending into the photic zone of the water column

methylhopanoids molecular indicators of ancient bacteria and a petroleum correlation tool abstract methylhopanoids are organic compounds synthesized by certain bacteria that when preserved in sediments act as molecular fossils or biomarkers for organic matter inputs from specific bacterial sources two series of methylhopanoids occur each mainly deriving from a distinct bacterial source cyanobacteria 2 methyl and methanotrophic bacteria 3 methyl the abundance and composition of methylhopanoids within sediments of modern depositional environments varies widely apparently due to different bacterial communities contributing to the sedimentary organic matter comparable molecular characteristics are found in oils and their source rocks consequently methylhopanoids are valuable in oil oil and oil source rock correlations distinguishing between samples related to different depositional environments in particular abundant 3 methylhopanoids from methanotrophic bacteria or an additional unknown bacterial source are characteristic of some modern alkaline saline lake environments comparable compositional features in the methylhopanes of oils allow the assignment of lacustrine oils offshore west africa to two distinct lacustrine source rock facies and to distinguish between different marine source facies thus refining oil source rock correlation

extended 3β methylhopanes up to c45 in source rocks from the upper cretaceous qingshankou formation songliao basin northeast china abstract 3 methylhopanes methylated at the c 3 position of the a ring have been detected ubiquitously in sedimentary rocks with carbon numbers of c28 and c30 c36 these compounds have been attributed to aerobic methanotrophs due to their strongly 13c depleted compositions here we report 3 methylhopanes with carbon numbers up to c45 in source rocks from the first member of the upper cretaceous qingshankou formation songliao basin northeast china the extended homologues up to c45 might be derived from long chain alkyl bacteriohopanetetrols by consecutive enzymatic additions of a c5 sugar extremely 13c depleted compositions combined with a high 3 methylhopane index suggest an intense ch4 cycle induced by blooms of aerobic methanotrophs in the songliao paleo lake

sediment transport by burrowing mammals marin county california abstract field observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in marin county california spatial concentrations of the 1 150 gopher mounds surveyed vary from 0 16 mounds m on interfluves to 0 32 mounds m on sideslopes and in the topographic hollow with localized concentrations of up to 2 88 mounds m on the margins of the colluvial deposit simple models of sediment transport by burrowing activity yield estimates of between 0 91 and 2 33 cm3 cm yr for the basin as a whole with absolute minimum and maximum rates of 048 and 6 31 cm3 cm yr i these values are similar to those previously estimated for this area lehre 1982 and are nearly an order of magnitude less than average long term sediment transport rates at the same site reneau 1988 key words sediment transport erosion rates bioturbation introduction burrowing animals disturb and transport soil in environments ranging from alpine tundra to humid grasslands hansen and morris

in situ formed and redeposited gypsum breccias in the middle miocene badenian of southern poland abstract gypsum arenites gypsum rudites and laminated gypsum occur in the upper part of the middle miocene badenian gypsum in southern poland we interpret these as resedimented deposits the large size of the clasts and precipitated rain from low density turbid layers these resedimented deep water depositss overlie a shelf evaporite complex of mostly shallow water gypsum the sequence is therefore generally deepening upward similar sequences with important redeposition episodes are characteristic of the final stage of development of many other evaporite basins the important environmental change that occurred at the top of the lower part of the gypsum sequence was induced by changes in basin dynamics and resulted climate change which we relate to an increased tectonic activity the resulting differentiation of the intrabasinal relief combined with possible brine level fluctuations and earthquakes led to a widespread redeposition of gypsum deposits the presence of in situ brecciation as well as levels of breccias recorded in the borkow quarry indicate that within the part of the discussed sequence the source of gypsum was not at the periphery of the basin

marine and continental lower permian evaporites of the prypiac trough belarus abstract sakmarian evaporites which include gypsum anhydrite halite carnallite kieserite and bischofite occur in the prypiac trough belarus within the lower and upper parts of one lithostratigraphic unit the svaboda suite the lower part of svaboda suite is up to 143 m thick and is composed of rock salt with interbeds of red claystones siltstones and potassium magnesium and magnesium sulfate salts which are correlated with the lowest potassic salts of the sakmarian kramators k suite of the dnipro donets basin these salts originated from precipitation from marine brines salts occur in a very limited area and the occurrence of sulfate facies is much wider the upper part of the svaboda suite up to 520 m thick is composed of interbedded mixed halite siliciclastic and terrigenous deposits there were two major sources of solutions flowing into the continental basin in which the subsuite was formed meteoric and continental waters and brines derived from the dissolution of devonian salts the distribution of the mixed halite siliciclastic facies was related to tectonic dislocations that controlled the depocenter and the outflow from the underlying famennian deposits of the major volume of salt into the intensively growing salt domes accordingly the tectonic framework was the major control on the evaporite basin during deposition of the upper part of the svaboda suite

the influence of hydrocarbon expulsion on carbon isotopic compositions of individual n alkanes in pyrolysates of selected terrestrial kerogens expulsion of petroleum from source rock is a complex part of the entire migration process there exist fractional effects on chemical compositions in hydrocarbon expulsion does the carbon isotopic fractionation occur during expulsion and to what extent here the influence of hydrocarbon expulsion on carbon isotopic compositions of individual n alkanes from pyrolysates of selected terrestrial kerogens from tuha basin and fushun liaoning province of china has been experimentally studied the pyrogeneration expulsion experiments were carried out under semi closed system the carbon isotopic compositions of individual n alkanes were measured by gc irms the main conclusions are as follows first there is carbon isotopic fractionation associated with hydrocarbon expulsion from type iii kerogens in tuha basin there exist differences of carbon isotopic compositions between the unexpelled n alkanes and expelled n alkanes from tuha desmocollinite and tuha mudstone second there is almost no carbon isotopic fractionation associated with hydrocarbon expulsion from type ii kerogens in fushun and liaohe basin third carbon isotopic fractionation in hydrocarbon expulsion should be considered in making oil source correlation of type iii kerogens at least in the tuha basin further studies need to be carried out to determine whether this is true in other basins fourth oil and source at different maturity levels cannot be correlated directly for type iii kerogens since the carbon isotopic compositions of expelled hydrocarbons at different temperatures are different the expelled hydrocarbons are usually lighter depleted in 13 c than the hydrocarbons remaining in the source rock at the same maturity

observations on the incorporation of trace elements in halite of oligocene salt beds bourg en bresse basin france abstract it is common practice to employ trace elements found in chloride salts as indicators of the conditions of deposition because some halite contains abundant fluid inclusions it is necessary to separate the salt from the inclusions before analysis this study presents the data derived from the use of a simple preparative technique which permits analysis of the trace elements in solid halite and provides a guide to test the success in elimination of the contaminants contained in the fluid inclusions the differentiation is accomplished simply by crushing the salt in alcohol followed by separate analysis of the fluid and solid components thus yielding accurate trace element concentrations in the solids crystal lattice dislocations and grain boundaries and the fluids br and k are present both in the solid and liquid phases of the halite but mg is exclusively in the fluid inclusions the elimination of the mg from the analysis of the solid phase may thus be employed as a monitor to indicate the degree of purification of the samples being analysed

lipid biomarkers record fundamental changes in the microbial community structure of tropical seas during the late ordovician hirnantian glaciation the late ordovician mass extinction was linked to climate cooling and glaciation of gondwana during the terminal ordovician hirnantian age 444 7 443 4 ma extinction patterns have been well described for many marine taxa but much less is known about marine microbial communities through this interval to elucidate the structure of microbial communities in tropical marine basins through the late ordovician we analyzed lipid biomarkers in thermally well preserved strata from the taconic foreland anticosti island canada the cincinnati arch midwestern united states and the western continental margin vinini formation nevada united states despite clear oceanographic differences lipid biomarker profiles show similarities between these three localities major shifts in biomarker distributions of anticosti island and the vinini formation mainly hopane sterane ratios record changes in the balance of bacterial versus algal primary production bacterial contributions to sedimentary organic matter were highest during warm intervals both before and after hirnantian cooling in particular 3 methylhopanes likely sourced from aerobic methanotrophic bacteria occur in high relative abundance many times the phanerozoic average across laurentia throughout most of the interval studied 3 methylhopane abundances also reveal an overall positive relationship with paleotemperature proxies implying increased methane cycling during warm intervals these results suggest that enhanced methane cycling could have provided an important positive feedback on climate during extended intervals of early paleozoic time

carbon isotopic composition of individual biomarkers in gilsonites utah abstract carbon isotopic compositions of saturated hydrocarbon aromatic hydrocarbon nso resin and asphaltene fractions of vein forming gilsonites cowboy bonanza independence wagonhound and harrison veins in the ne uinta basin utah are all similar and isotopically resemble mahogany zone shale extracts of the green river formation 13 c 29 to 31 individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the eocene uinta greater green river paleolake system carbon isotopic compositions of c28 and c29 steranes 13 c 25 to 32 pristance and phytane 33 to 34 and perhydro carotene carotane 13 c 33 2 suggest that organisms producing these compounds grew near the lake surface the c33 carotenoid lexane is isotopically identical to the c40 carotenoid carotane supporting a common c40 carotenoid precursor two groups of hopanes can be differentiated in the gilsonites based on carbon isotopic compositions c29 c31 and c32 hopanes and moretanes 40 9 to 44 3 consistent with a source from midwater bacteria and c30 hopanes and moretanes 51 0 and 60 5 for which the strong 13c depletion suggests at least partial derivation from methylotrophs the isotopic signatures of these molecular fossils suggest the source beds of the gilsonites were deposited in a stratified paleolake system with a depositional environment similar to that which formed the mahogany zone shales of the piceance creek basin algal biomarkers in the gilsonites are isotopically uniform throughout the area of the gilsonite vein occurrence 1500 km3 and resemble those in the mahogany zone shale in the piceance creek basin over 50 km to the east this remarkable lateral uniformity suggests that very similar photic zone water conditions existed across the entire uinta piceance creek paleolake system at the time of deposition of the gilsonite source bed mahogany zone shale sterane isotopic compositions are effective for the genetic correlation of the solid bitumens immature oils in contrast the carbon isotopic compositions of the bacterial biomarkers in the gilsonites vary significantly suggesting that conditions in deeper waters of the paleolake system were more variable carbon isotopic signatures of individual hopane biomarkers in the green river formation appear to be valuable for identifying different source facies characteristics within the same paleolake depositional system

the study on the source of the oil seeps and bitumens in the tianjingshan structure of the northern longmen mountain structure of sichuan basin china abstract the tianjingshan structure of the northern longmen mountain is located in the north of the sichuan province china two primary source rocks are present in this region the overmature infracambrian lower cambrian source rocks and the mature upper permian source rocks oil seeps and solid bitumens occur extensively in the mesozoic and paleozoic marine strata indicating good exploration prospects in this area however oil to source correlation in the tianjingshan structure is difficult due to both high maturity of the lower cambrian source rocks and severe biodegradation of oil seeps and bitumens in this work one oil seep from the permian qixia formation and two severely degraded bitumens from the cambrian strata in the tianjingshan structure were correlated with their potential source rocks hydropyrolysis was used to release biomarkers bound to kerogen of the overmature lower cambrian source rock the released biomarkers were used for the oil to source correlation together with those indexes resistant to thermal degradation and biodegradation based on the geochemical data and the petroleum geological settings of the area it can be inferred that the cambrian ordovician and silurian bitumens with light bulk isotopic values commonly 13 c

zoogeomorphology in the alpine some observations on abiotic biotic interactions abstract cryonival processes typify the alpine environment these cold based processes operate synergistically with wind rainsplash surface wash and mass movement to create the local morphology these traditionally accepted abiotic processes are rarely if ever identified as operating in conjunction with biotic processes paradoxically the existence and activity of animals within the alpine zone is widely reported here the argument will be made for the interoperation of the biotic with the abiotic in the development of the alpine terrain animals frequently exert a strong geomorphic influence in alpine environments through such activities as grazing trampling digging burrowing and direct erosion of even bedrock the impact of the animals in a geomorphic context can be both direct and indirect direct effects are soil compaction removal of sediments loading causing slope failure and the introduction or removal of chemicals nutrients as significant as these impacts can be so too are the indirect effects preparation of sediments for removal by abiotic processes decreasing of slope stability by burrowing increasing surface wash and or concentration of overland flow as a result of compaction pedoturbation and changing of soil water chemistry because of facilitating water penetration as a result of burrowing the abiotic and biotic impacts occur both in parallel i e at the same time and or in series i e one subsequent to another frequently as a function of seasonal climatic influences on both forces climate exerts a significant impact on both biotic and abiotic processes and aspect can greatly influence these solar radiation ground temperature wind and precipitation affect biotic and abiotic attributes and their interaction slope angle and parent material s will also affect the degree of influence biotic abiotic interactions are complex outcomes of parent material aspect slope and season and all of the factors that these influence i e vegetation here a series of flow diagrams are used to identify both abiotic and biotic elements and to show the manner in which they interoperate to create the local alpine terrain examples from a variety of alpine locations canada and china will be used to exemplify geomorphic outcomes

modeling the sulfur and oxygen isotopic composition of sulfates through a halite potash sequence implications for the hydrological evolution of the upper eocene southpyrenean basin the isotopic composition of sulfates sampled throughout a complete evaporite sequence has contributed to the understanding of the evolution of the southpyrenean upper eocene basin the 34s and 18o values appear to be constant in thick segments of the sequence this pattern is clearly different from the continuous decrease in values predicted by the evaporation processes in a closed system the observed trend of the 34s and 18o values can be successfully modeled by an evaporation process in an open system where steady state conditions are reached separated by periods of significant changes in the hydrological regime of the basin moreover in the segments of the sequence where they are constant the 34s and 18o values help to constrain the hydrological parameters of the model a first marine stage of the evolution of the basin corresponds to the formation of the basal anhydrite and lower halite units the mineral sequence corresponds to evaporation in a basin with a progressive degree of restriction and evaporation compensated by equal inflow of major marine origin the sharp decrease in the 34s and particularly the 18o values recorded at the end of the basal anhydrite unit illustrates a limited reservoir effect produced by the increase of restriction leading to the halite precipitation the modeling of the constant isotopic values through the lower halite unit confirms the isotopic composition of eocene marine dissolved sulfate 34s 20 0 0 18o 8 7 0 deduced from the average values of marginal gypsum the second continental stage of basin evolution corresponds to the formation of the potash unit and the upper halite unit the mineral sequence and lateral extension indicate that the basin evolved with a decreasing brine volume after disconnection from the sea the dilution of the residual brine stopped the precipitation of camallite and the basin then evolved as a perennial endorreic lake with continental recharge replacing evaporation the sharp decrease in the 34s and 18o values in the sylvite member is consistent with the massive precipitation of sulfate occurring during the decrease in the volume of water the values of the sulfates intercalated in the camallite and the upper halite unit indicate the influence of the recycling of both the already deposited upper eocene sulfates and the upper triassic sulfates carried by continental recharge the constant 34s and 18o values from the uppermost half of the upper halite unit is used to constrain the sulfate source as 80 recycled upper triassic and 20 recycled eocene gypsum

salt deposition and brine evolution in the granada basin late tortonian se spain abstract a group of sedimentary basins in the betic chain were formed during the middle late miocene as a result of the closure of the tethys during the alpine orogeny in the late miocene tortonian messinian the connections between the atlantic ocean and mediterranean sea were interrupted and those basins hosted major evaporites the granada basin an inner basin located far from the mediterranean contains a thick rock salt deposited during the latest tortonian in the transition from marine to non marine conditions in the centre of the basin three halite bearing units overlie a basal anhydrite bed the lower halite unit the intermediate sandstone unit and the upper halite unit fluid inclusion compositions and bromine concentrations in halite together with stable isotopes 34 s sulfate 18 o sulfate and 87 sr 86 sr indicate a mixture of different inflow waters in the granada basin beginning with a marine lagoon that evolved into a salt pan strongly isolated from the sea saline waters evolved from sulfate rich marine derived to sulfate depleted non marine brines influenced by the addition of cacl 2 rich inputs these cacl 2 rich waters were probably linked to thermal fluids associated with a major crustal fracture system crevillente or cadiz alicante fault system that cuts through the granada basin

is there evidence for a substantial contribution of prokaryotic biomass to organic carbon in phanerozoic carbonaceous sediments the role of prokaryotes bacteria and archaea in producing biomass and reworking settling and buried organic matter is of paramount importance since it exerts a major impact on the composition of sedimentary organic matter and ultimately petroleum this key role of prokaryotes in combination with a biomarker fingerprint often dominated by prokaryotic molecular fossils e g hopanoids has led to the assumption that prokaryotic biomass is a substantial source for organic carbon in carbonaceous sediments however biosynthesising and reworking organic matter does not necessarily imply sourcing organic matter by the prokaryotes and the abundance of biomarkers does not always reflect relative contributions to sedimentary organic matter in this paper the existing evidence for a substantial prokaryotic biomass contribution to sedimentary organic carbon oc is critically evaluated this shows that despite the often prominent presence of prokaryotic biomarkers in sediments evidence for a substantial prokaryotic contribution to sedimentary oc is generally lacking this is demonstrated by i the application of the carbon isotopic mass balance principle in various sedimentary settings ii an alternative explanation for the proposed dominant role of heterotrophic reworking in the oxford clay iii a summary of the effects of bacterial oxidation in organic matter rich turbidites and iv recent data showing that the evidence for recalcitrant carbon in prokaryotes is scant although these observations do not rule out substantial contributions of prokaryotic carbon to oc in phanerozoic carbonaceous sediments this remains to be demonstrated and the final answer awaits the development of new technologies to full characterise sedimentary oc

interaction of coal and oil in confined pyrolysis experiments insight from the yields and carbon isotopes of gas and liquid hydrocarbons abstract isothermal confined gold capsule pyrolysis experiments were performed for coal alone oil alone and coal plus oil with oil coal ratios ranging from 0 006 to 0 171 at 315 c 345 c and 375 c respectively and 50 mpa for 72 h in the experiment for coal plus oil the amounts and compositions of hydrocarbon gases are substantially different from those predicted from the results in the experiments for oil alone and coal alone the results of these experiments demonstrate that kerogen and oil do not crack separately in the experiments of coal plus oil the interaction between kerogen and oil components leads to the generation of hydrocarbon gases with oil coal ratio increasing the amounts of individual and total hydrocarbon gases decrease at first and then increase rapidly up to several times those calculated from the yields of these components in the experiments for oil alone and coal alone the c1 c1 5 ratios of hydrocarbon gases decrease and are increasingly lower than those calculated from the yields of hydrocarbon gases in the experiments for oil alone and coal alone the amount and carbon isotopes of individual n alkane demonstrate that the free liquid n alkanes were incorporated into kerogen and replaced the bound liquid n alkanes covalently bonded alkyl groups in kerogen carbon isotopes of hydrocarbon gases further suggest that the bound liquid n alkanes in kerogen preferentially crack into hydrocarbon gases

the major ion composition of cenozoic seawater the past 36 million years from fluid inclusions in marine halite fluid inclusions from ten cenozoic eocene miocene marine halites are used to quantify the major ion composition mg2 ca2 k na so42 and cl of seawater over the past 36 my criteria used to determine a seawater origin of the halites include 1 stratigraphic sedimentologic and paleontologic observations 2 br in halite 3 34s of sulfate minerals 4 87sr 86sr of carbonates and sulfates and 5 fluid inclusion brine compositions and evaporation paths which must overlap from geographically separated basins of the same age to confirm a global seawater chemical signal changes in the major ion chemistry of cenozoic seawater record the end of a systematic long term 150 my shift from the ca2 rich mg2 and so42 poor seawater of the mesozoic cacl2 seas to the mgso4 seas with higher mg2 and so42 ca2 of the cenozoic the major ion composition of cenozoic seawater is calculated for the eocene oligocene 36 34 ma serravallian tortonian 13 5 11 8 ma and the messinian 6 5 ma assuming chlorinity 565 mmolal salinity and the k concentration 11 mmolal are constant and the same as in modern seawater fluid inclusions from cenozoic marine halites show that the concentrations of mg2 and so42 have increased in seawater over the past 36 my and the concentration of ca2 has decreased mg2 concentrations increased from 36 mmolal in eocene oligocene seawater 36 34 ma to 55 mmolal in modern seawater the mg2 ca2 ratio of seawater has risen from 2 3 at the end of the eocene to 3 4 and 4 0 respectively at 13 5 to 11 8 ma and 6 to 5 ma and to 5 in modern seawater eocene oligocene seawater 36 34 ma has estimated ranges of so42 14 23 mmolal and ca2 11 20 mmolal if the ca2 so42 product is assumed to be the same as in modern seawater 300 mmolal2 eocene oligocene seawater had ca2 16 mmolal and so42 19 mmolal the same estimates of ca2 and so42 for serravallian tortonian seawater 13 5 11 8 ma are so42 19 27 mmolal and ca2 8 16 mmolal and so42 24 mmolal and ca2 13 mmolal if the ca2 so42 product is equal to that in modern seawater messinian seawater has an estimated range of so42 21 29 mmolal and ca2 7 15 mmolal with so42 26 mmolal and ca2 12 mmolal assuming the ca2 so42 product is equal to that in modern seawater regardless of the estimation procedure so42 shows progressively increasing concentrations from 36 ma to the present values which are the highest of the cenozoic

methylhopane biomarker hydrocarbons in hamersley province sediments provide evidence for neoarchean aerobiosis abstract bacteriohopanepolyols with a ring methyl substituents are bacterial lipid biomarkers that are presently known to originate from just a few specific taxa when preserved in ancient rocks the fossilized hydrocarbon skeletons of these molecules have the potential to provide biogeochemical records of those taxa and their respective physiologies considering both their occurrences in modern organisms and their proterozoic and phanerozoic sedimentary distributions hopanes carrying 2 methyl or 3 methyl substituents are proposed to be derived from cyanobacteria and oxygen respiring methanotrophs respectively here we report the distribution of methylhopanes in 2 72 2 56 billion year old neoarchean rocks from the hamersley province on the pilbara craton the relative abundance of c 31 3 methylhopane but not that of c 31 2 methylhopane shows a strong correlation to the carbon isotopic composition of co occurring kerogen insoluble particulate organic matter the unanticipated nature of this relationship provides evidence for a shallow water locus of carbon cycling through aerobic oxidation of ch 4 and coincidentally a means to demonstrate biomarker syngenicity 2 methylhopanes are most abundant in both shale and carbonate from shallow water sediments and a positive correlation to carbonate abundance contrasts to variable but generally lower 2 methylhopane abundances of deeper water facies these observations are consistent with their origin from cyanobacteria which were likely the cornerstone of microbial communities in shallow water ecosystems providing molecular oxygen fixed carbon and possibly fixed nitrogen

molecular and carbon isotopic geochemistry of crude oils and extracts from permian source rocks in the northwestern and central junggar basin china abstract the junggar basin is a major oil producing province in china most oil reservoirs found so far in this basin are in the mahu sag and neighboring uplifts northwestern junggar basin a total of 78 oils and 10 permian source rocks from the northwestern and central junggar basin and two oils and two permian source rocks from the eastern junggar basin were analyzed by gc gc ms and gc irms the 78 oils can be clearly classified into two groups based on these analytical results for group i oils 13c values of individual n alkanes are relatively higher and remain stable with increasing carbon number for group ii oils these values are relatively lower and decrease at first and then increase with carbon number differences in molecular parameters can be also observed between these two groups of oils group i oils generally have 1 higher pr n c17 and ph n c18 ratios and lower pr ph ratio and 2 higher gammacerane c30 hopane gammacerane and carotane carotane c30 hopane ratios compared with group ii oils in addition group i oils mainly have tricyclic terpane distribution patterns with either c20 c21 c23 while group ii oils mainly have the pattern of c20 c23 however molecular parameters overlap to some extent between these two groups of oils group i oils correlate well with the nine source rocks of the lower permian fengcheng formation p1f while group ii oils correlate well with the three source rocks of middle permian age based on carbon isotopic and molecular compositions the occurrence of these two groups of oils in the northwestern and central junggar basin are consistent with facies and thickness variations in the source rocks within the lower permian fengcheng formation p1f and middle permian lower wuerhe formation p2w

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

an experimental study on the burrowing activity of river crabs on subsurface water movement and piping erosion abstract the effects of the burrowing activity of river crabs on subsurface water movement and piping erosion were studied through a flume experiment cohesive field soil was used and constant fluvial head was applied during the experiments with river crabs burrows were excavated downwards under the groundwater level at the outlet of each burrow the crabs excavated pellets of soil and stacked them in piles in the form of cone mounds these mounds acted as effective dams for subsurface outflow but they sometimes collapsed the roofs of the burrows also caved in occasionally whereby the crabs would excavate new burrows the burrowing activity of the crabs led to marked erosion in contrast no marked erosion was observed in experiments without crabs indicating that piping erosion occurs through the assistance of burrowing activity it was observed that burrowing activity and piping erosion was pronounced when the hydraulic head was not significantly high 0 21 0 25 analysis of the potential distribution of the soil mass indicated that the head loss close to the burrow was small in the case of experiments with crabs this suggests that the burrow enhances rapid discharge of subsurface water consequently burrowing activity was found to play an important role in piping erosion and rapid discharge of subsurface water

characteristics and origin of carbon isotopes of n alkanes in crude oils from the western pearl river mouth basin south china sea abstract the quantitative characterization of carbon isotopes of n alkanes is commonly carried out in organic geochemical studies possible controls on carbon isotopes include source organic matter maturity fractionation during oil expulsion and migration and the mixing of different oils in this study of the origin of crude oils in the western pearl river mouth basin the influences of all of these factors have been considered in reaching a conclusion carbon isotopes of n alkanes in the crude oils and the extracts of the two effective source rocks the wenchang and enping formations in the basin exhibit clear differences the wenchang source rocks have heavy 13 c values that remain almost constant or become slightly heavier with increasing carbon number the enping source rocks have light 13 c values that become lighter with increasing carbon number two groups of oils in this area were identified based on the carbon isotopes of the n alkanes groupioils are similar to extracts of the wenchang source rocks however the groupiioils are different from both the wenchang and enping source rocks and the carbon isotopic profiles of their n alkanes exhibit a v feature with increasing carbon number the results of artificial thermal maturation experiments indicate that from the early stage to the peak stage of oil generation with easyro between 0 64 and 1 02 the 13 c values of n alkanes in the pyrolysis oils become heavier by about 3 with increasing thermal maturity but the shape of the carbon isotopic profiles are not significantly changed calculated 13 c values of n alkanes in mixed artificial pyrolysis oils indicate that the mixture of oils generated from the same source rocks with different maturities could not change the carbon isotopic profile of the n alkanes however a mixing of the wenchang and enping oils could give the v feature in the profiles similar to the groupiioils in this area the groupiioils appear to be mixed wenchang and enping oils the latter being the dominant component in the mixture we conclude that the source organic matter and the degree of mixing are the main factors controlling the carbon isotopic characteristics of n alkanes in crude oils in the western pearl river mouth basin

correlation of crude oils and oil components from reservoirs and source rocks using carbon isotopic compositions of individual n alkanes in the tazhong and tabei uplift of the tarim basin china abstract carbon isotopic compositions were determined by gc irms for individual n alkanes in crude oils and the free adsorbed and inclusion oils recovered by sequential extraction from reservoir rocks in the tazhong uplift and tahe oilfield in the tabei uplift of tarim basin as well as extracts of the cambrian ordovician source rocks in the basin the variations of the 13 c values of individual n alkanes among the 15 oils from the tazhong uplift and among the 15 oils from the triassic and carboniferous sandstone reservoirs and the 21 oils from the ordovician carbonate reservoirs in the tahe oilfield demonstrate that these marine oils are derived from two end member source rocks the major proportion of these marine oils is derived from the type a source rocks with low 13 c values while a minor proportion is derived from the type b source rocks with high 13 c values type a source rocks are within either the cambrian lower ordovician or the middle upper ordovician strata not drilled so far while type b source rocks are within the cambrian lower ordovician strata as found in boreholes td2 and fang 1 in addition the three oils from the cretaceous sandstone reservoirs in the tahe oilfield with exceptionally high pr ph ratio and 13 c values of individual n alkanes are derived or mainly derived from the triassic jurassic terrigenous source rocks located in quka depression the difference of the 13 c values of individual n alkanes among the free adsorbed and inclusion oils in the reservoir rocks and corresponding crude oils reflects source variation during the reservoir filling process in general the initial oil charge is derived from the type b source rocks with high 13 c values while the later oil charge is derived from the type a source rocks with low 13 c values the 13 c values of individual n alkanes do not simply correlate with the biomarker parameters for the marine oils in the tazhong uplift and tahe oilfield suggesting that molecular parameters alone are not adequate for reliable oil source correlation for high maturity oils with complex mixing

sedimentary and diagenetic markers of the restriction in a marine basin the lorca basin se spain during the messinian abstract the lorca basin southeastern spain is part of a chain of small marginal neogene basins located in the structurally active betic area the upper miocene messinian sequence is composed of a thick diatomite bearing series tripoli unit overlain by the main evaporites analogous to the classical succession that records the main events during the salinity crisis in the mediterranean region the shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings an integrated approach using sedimentology micropalaeontology stable isotope geochemistry and organic geochemistry has been applied to the tortonian messinian succession of the lorca basin in order to obtain a continuous record of the environmental changes the sediments record two major events which affected the whole mediterranean 1 high levels of productivity that led to the formation of the diatomite bearing deposits in the early messinian tripoli and 2 the messinian salinity crisis with its two major stages represented by the halite and gypsum units both mainly precipitated from marine derived brines the rapid reflooding of the mediterranean by normal marine waters at the base of the pliocene did not reach the lorca basin nor other basins of this part of the betic area instead continental sediments were deposited as a consequence of the regional uplift of se iberia which started close to the messinian pliocene boundary the most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the tripoli unit which led to intercalations of precursor evaporitic layers consisting of ca sulphate deposited in sub aqueous and sabkha conditions interbedded with diatomites this alternation of evaporites and diatomites proves that the lorca basin was periodically restricted and reflooded by marine waters a possible cause for this being relative sea level fluctuations in the mediterranean this strengthens evidence of diachronism that suggests that the onset of the first messinian evaporitic deposition was not synchronous but was dependent on bathymetry and local tectonics high productivity during the early messinian in this basin is demonstrated by the thick deposits of diatomites however stagnation episodes may have occurred during this interval as suggested by the preservation of high amounts of organic matter organic rich shales and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis the formation of organo sulphur compounds replacement of sulphates by carbonates and the high levels of elemental sulphur are by products of diagenetic processes occurring in a restricted hypersaline environment

composition of fluid inclusions in permian salt beds palo duro basin texas u s a abstract several methods have been developed and used to extract and chemically analyze the two major types of fluid inclusions in bedded salt from the palo duro basin texas data on the ratio k ca mg were obtained on a few of the clouds of tiny inclusions in chevron salt representing the brines from which the salt originally crystallized much more complete quantitative data na k ca mg sr cl so 4 and br were obtained on 120 individual large mostly 500 m on an edge i e 1 6 10 4 g inclusions in recrystallized salt these latter fluids have a wide range of compositions even in a given piece of core indicating that fluids of grossly different composition were present in these salt beds during the several stages of recrystallization the analytical results indicating very large inter and intra sample chemical variation verify the conclusion reached earlier from petrography and microthermometry that the inclusion fluids in salt and their solutes are generally polygenetic the diversity in composition stems from the combination of a variety of sources for the fluids permian sea meteoric and groundwater as well as later migrating ground formation or meteoric waters of unknown age and a variety of subsequent geochemical processes of dissolution precipitation and rock water interaction the compositional data are frequently ambiguous but do provide constraints and may eventually yield a coherent history of the events that produced these beds such an understanding of the past history of the evaporite sequence of the palo duro basin should help in predicting the future role of the fluids in the salt if a nuclear waste repository is sited there

a paleoweathering profile from griqualand west south africa evidence for a dramatic rise in atmospheric oxygen between 2 2 and 1 9 bybp a core drilled near wolhaarkop in griqualand west south africa intersected highly oxidized kuruman iron formation below red beds of the gamagara formation the lateral equivalents of the kuruman iron formation in this drill hole consist largely of siderite ankerite magnetite greenalite and quartz the oxidation of the kuruman iron formation in wol 2 occurred almost certainly during weathering prior to the deposition of the gamagara formation the date of this weathering episode is bracketed between about 2 2 and 1 9 bybp by the age of the ongeluk lavas in the transvaal sequence below the unconformity and by the age of the hartley lavas in the olifantshoek group above the unconformity the ratio of iron to sio2 in the several facies of the weathered kuruman iron formation in wol 2 is nearly the same as that in their unweathered equivalents since sio2 loss during weathering was almost certainly minor the similarity of the fe sio2 ratio in the weathered and unweathered bif indicates that nearly all the feo in the kuruman iron formation was oxidized and retained as feo3 during weathering such a high degree of iron retention is best explained by an o2 content of the atmosphere or 0 03 atm at the time of weathering such an o2 pressure is very much greater than that suggested by the composition of paleosols developed on basalt or 2 2 bybp but is consistent with the highly oxidized nature of the 1 85 by flin flon paleosol the new data suggest that po2 rose dramatically from about 1 percent pal present atmospheric level to or 15 percent pal between 2 2 and 1 9 bybp

origin and age of the mediterranean messinian evaporites implications from sr isotopes strontium isotope ratios from the messinian late miocene 6 4 to 4 85 ma evaporites of the mediterranean basin 1 2 support a subdivision into stratigraphically lower predominantly marine deposits lower evaporites lev lower gypsum and main salt characterized by sr isotopic ratios generally equivalent to those of messinian seawater and stratigraphically higher deposits upper evaporites uev with 87sr 86sr ratios lower than messinian seawater the range of 87sr 86sr ratios of the lev unit from the eastern mediterranean overlap with values obtained from essentially coeval red sea evaporites 3 strontium isotopic ratios measured from the upper evaporites however are lower and a high proportion of this sr was probably derived from low 87sr 86sr continental runoff that characterizes much of this basin 4 these results therefore strongly support depositional models utilizing a deep desiccated basin 1 with a constant marine inflow during the early stages including salt formation followed by a series of long lasting and sometimes isolated desiccation events that produced a strong but variable continental influence on the sr isotopic compositions of the uev strontium isotopic measurements can also be used to asses the actual timing of the deposition of the lev ratios obtained from oyster fragments and foraminifers from pre evaporitic units at odp site 654 tyrrhenian sea suggest that the major rifting phase in this region occurred between 8 and 6 5 ma ratios obtained from the early lev from the mediterranean sea suggest that initiation of evaporite deposition began about 5 65 ma ago results from units immediately overlying the uev in sicily suggest termination of evaporite deposition about 4 9 ma ago errors associated with these age estimates are about 0 5 ma 2

seepage erosion and its implication to the formation of amphitheatre valley heads a case study at obara japan seepage erosion was investigated in an amphitheatre with a semicircular valley head steep slopes and a flat bottom developed in granodiorite hills at obara aichi prefecture japan a high sediment yield occurred where the measuring sites were located at the base of the landslide debris in the base of the convex slopes whereas sediment outflows were small where the measuring sites were located at the base of the strong convex slopes this implies that the seepage erosion was an effective agent for removal of debris deposited at the base of the slope small landslides can be found at the lower slopes within the area of the observed amphitheatre the slope stability analysis and subsurface water observation of the lower slope suggest that the small landslides in this amphitheatre are due to over steepened slopes and relatively insensitive to subsurface water status colluvium in the flat valley bottom thinly covers the bedrock surface therefore the topography of the amphitheatre was found to be formed by parallel retreat of slopes by the repetition of basal seepage erosion and subsequent small landslides

the chemical and hydrological evolution of an ancient potash forming evaporite basin as constrained by mineral sequence fluid inclusion composition and numerical simulation the chemical evolution of the brine in a potash evaporite basin has been investigated by x ray microanalysis of frozen primary inclusions trapped in halite a computer program based on thermodynamic equilibrium and mass balance principles has been used to simulate evaporation paths the comparison between the results of calculations the observed mineralogy and mineral sequence and the solute content in fluid inclusions has placed constraints on the hydrological evolution of the basin the upper eocene basin of navarra southern pyrenees spain began as a marine basin evolving from a moderate to a high degree of restriction depositing first a basai anhydrite horizon and then a thick sequence of massive halite an additional inflow of cacl2 in the basin during seawater evaporation is proposed as the process responsible for the sulfate depletion required for sylvite instead of mg sulfates to form mixing of seawater with continental waters bacterial sulfate reduction and in situ dolomitization are discarded the basin subsequently closed to the sea and evolved with decreasing volume alternating bands of clays halite sylvite and then clays halite carnallite were deposited under the influence of seasonal continental recharge before reaching total desiccation the residual brine was diluted by continental water the basin then evolved under an endoreic regime where continental recharge and the recycling of previously formed halite led to deposition of alternating beds of clays and halite

novel cyclised and aromatised diagenetic products of β carotene in the green river shale abstract a suite of novel diagenetic products of carotene has been identified in an extract of a sample from the green river shale identification is mainly based on comparison of mass spectra with those of diagenetic products of another carotenoid isorenieratene these compounds were formed by i cyclisation and aromatisation of the polyene isoprenoid chain ii explusion of toluene and m xylene from the polyene isoprenoid chain and iii aromatisation of the 1 1 5 trimethylcyclohex 5 enyl moieties resulting in 1 2 dimethylbenzene end groups reduction of the double bonds of carotene is the most important diagenetic process however as judged from the high relative amount of carotane 63 of quantified diagenetic products of carotene these results indicate that the fossilisation potential of carotenoids is greater than previously thought

environmental and sequence stratigraphic implications of anhydrite textures a case from the lower triassic of the central persian gulf abstract the lower triassic kangan formation in the persian gulf south pars gas field and its adjacent areas are composed of carbonate evaporite sequences these sediments were deposited in a shallow marine homoclinal ramp study of the anhydrite bearing intervals shows various structures and textures the anhydrite structures are mainly bedded massive chicken wire and nodular type and the main textures are felted sparse crystal needle shape lath shape equant and fibrous pervasive and poikilotopic cement together with replacement and porphyroblastic gypsum are accounted as the most common diagenetic features in anhydrite evaluation of anhydrite occurrences and features support both primary and secondary formations the nodular to chicken wire anhydrite formed under synsedimentary sabkha conditions whereas anhydrite cements occurred during the late stages of diagenesis shallow burial stage massive to bedded anhydrite could have been formed under subaqueous conditions or originated by coalescing and continued growth of anhydrite nodules in the sabkha zone anhydrite fabrics impose a significant control on the reservoir quality of the kangan carbonates at the south pars gas field thick massive and bedded anhydrite could have been formed as an intraformational seals and anhydrite cements occluded pore spaces and reduced the poroperm values the sequence stratigraphic analysis revealed two depositional sequences in the studied intervals which are composed of tst and hst investigation of anhydrite throughout depositional sequences indicates a change in the content and style of anhydrite texture anhydrite content volume decreases upward through transgressive system tract sea level rise whereas it enhances during highstand system tract sea level fall pervasive and poikilotopic anhydrite cements together with replacement by anhydrite are prevalent features during transgressive and early highstand system tract at the late hst with a progradational stacking pattern anhydrite value increases and felted radial equant crystalline and mosaic texture are the most common anhydrite fabrics sequence boundaries that indicate maximum sea level fall and exposure of successions are marked by the broad anhydrite deposits with massive to bedded and chicken wire structures and various textures that located in late hst package there is an unambiguous relationship between the microfacies associations the evaporite textures and the sea level fluctuations this relationship could lead to a predictable pattern that can be of use as a general guide for the sequence stratigraphic interpretations in the area

compound specific isotopic variability in uinta basin native bitumens paleoenvironmental implications abstract we have analyzed the solvent extracts from three different types of native bitumens from the uinta basin in northeastern utah by a variety of analytical techniques including gc irms to evaluate variations in the paleodepositional environment during two periods of lake uinta deposition the gilsonite and tabbyite bitumens are associated with parachute creek member sediments deposited during a major expansion of ancient lake uinta compound specific isotopic analyses of s carotane and phytane 13 c 32 6 to 32 1 0 from these bitumens reflect input from primary photosynthetic producers such as cyanobacteria sterane 13c values 34 5 to 29 2 0 refflect contributions from lacustrine algae while extremely depleted 13c values for methylhopanes 58 1 to 61 5 0 suggest input from methanotrophic bacteria variations in the 13c values of the hopanes 51 4 to 37 7 0 imply additional input from other bacterial sources the wurtzilite bitumen was generated from the saline facies of the green river formation deposited during a later regression of lake uinta compound specific isotopic analyses of phytane 13 c 30 1 0 and steranes 13 c 29 6 to 26 7 0 from this bitumen indicate continued input from primary producers and eukaryotes the higher relative concentrations of gammacerane 13 c 26 9 0 indicate increasing input from aerobic protozoa we observed a slight enrichment in 13c in the wurtzilite extract and several biomarkers and suggest that this is a result of sulfate reducing bacteria outcompeting methanogens thereby eliminating the influence of methanotrophs in this later saline stage of deposition

upper permian lacustrine organic facies evolution southern junggar basin nw china abstract the jingjingzigou lucaogou and hongyanchi formations of the southern junggar basin together comprise over 1000 m of organic rich lacustrine facies they record an overall evolution from relatively shallow evaporative lakes to freshwater lakes associated with fluvial systems the jingjingzigou formation is characterized by low toc and hi and biomarker features such as abundant carotane consistent with a specialized saline or hypersaline biota biomarker distributions in jingjingzigou formation extracts most closely resemble oils from the giant karamay oilfield the lucaogou formation represents one of the richest and thickest lacustrine source rock intervals in the world yet it contradicts conventional lacustrine source rock models in at least two important aspects first deposition occurred at middle paleolatitudes 39 43 n rather than in the tropics second limited nutrient supply in a drainage basin dominated by intermediate volcanic rocks appears to have caused low to moderate primary productivities stable salinity stratification and low inorganic sedimentation rates in a deep lake nonetheless resulted in deposits with up to 20 toc and hi near 800 the overlying hongyanchi formation has 1 5 toc but low hi and was deposited in freshwater oxic to sub oxic lakes

geochemical and isotopic evidence for palaeo seawater intrusion into the south coast aquifer of laizhou bay china this research aims to improve the current knowledge of groundwater salinisation processes in coastal aquifers using combined hydrochemical and isotopic parameters and inverse hydrochemical modelling field investigations were conducted in laizhou bay which is the area most seriously affected by seawater intrusion in north china during three sampling campaigns along a vertical transect in the changyiliutuan area 95 ground and surface water samples were collected for major ion and isotope analysis

the use of environmental markers to distinguish marine vs continental deposition and to quantify the significance of recycling in evaporite basins abstract environmental markers namely the bromine content of halite samples the electrolyte content of primary fluid inclusions in halite and the isotopic composition of sulphates from two tertiary evaporite sequences provide complementary information on the depositional environment marine vs continental the use of these markers together with lithofacies and thicknesses of precipitated evaporites enable the detection and quantification of evaporite recycling within evaporite basins the information provided by the isolated use of each of these geochemical markers should be used with caution as this could lead to erroneous interpretations of the depositional environment or may not detect significant evaporite recycling processes the complementary information provided by geochemical markers enable quantification of solute input from recycling of previous precipitates within the basins themselves or from older evaporites the input of recycled evaporites increases progressively together with evaporite basin restriction to the open ocean

the composition of permian seawater forty nine brine inclusions in marine halite from the ochoan salado formation in the delaware basin and fifteen inclusions in halite from the leonardian wellington formation in the kansas basin were extracted and their chemical compositions were determined the brines are of the na k mg cl so4 type their compositions resemble those of evaporated modern seawater the values of mcl mna mbr and mmg2 mca2 mso42 12 mmhco3 mbr of the inclusion brine from the two formations are equal to or slightly higher than those of modern seawater the original mna mbr and mcl mbr ratios of the inclusion brines were probably equal to or slightly larger than those of modern seawater the values of mmg2 mbr of the inclusion brines from the salado formation are very close to that of modern seawater the ratios of inclusion brines from the wellington formation are slightly lower probably due to the formation of dolomite magnesite the mmg2 mbr ratio in the initial seawater was probably close to the parent seawater of the salado brines the values of mso42 mca2 12mhco3 mbr of the inclusion brines appear to be reduced by the formation of dolomite magnesite and the value of this ratio in permian seawater was probably similar to that of modern seawater the mk mbr ratios of the inclusion brines are variable but the original ratios are probably close to or slightly larger than that of modern seawater if the br concentration of permian seawater was equal to that of modern seawater the composition of permian seawater can be narrowly constrained in mmol kg h2o 460 mna 630 550 mcl 730 mmg2 54 6 mk 11 mso2 4 mca2 12mmhco3 17 20 mso42 45 5 mca2 20 and 0 15 mhco3 5 the composition of permian seawater was therefore quite similar to that of modern seawater

the geochemical evolution of the catalan potash subbasin south pyrenean foreland basin spain over the last decade our studies in ancient evaporitic basins have been based on a detailed study of a single borehole record the detailed findings in medium to large sized evaporitic basins were shadowed with a relevant question can interpretations from a representative evaporitic record in a single borehole be extended to the whole evaporitic basin this paper addresses that question the results obtained are compared with results from another distant point within the basin the general methodology not only proves its reliability in interpreting the evolution of evaporitic basins from a single borehole but reveals its capability to obtain detailed palaeoenvironmental interpretations the chemical evolution of an upper eocene evaporitic sequence from the south pyrenean foreland basin spain has been investigated along the suria 19 borehole record detailed petrographic and mineralogical study x ray microanalysis of frozen primary inclusions trapped in halite cryo sem eds systematic isotopic analysis d 34 s and d 18 o in sulphates and computer based evaporation models have been integrated in a multi proxy methodology this study revealed that a variable amount of ca excess is required throughout different parts of the marine lower halite unit lhu for sylvite instead of k mg sulphates to form this ca excess is in turn different from that required for the western sector of the same evaporitic basin navarrese subbasin quick and variable changes in ca rich brines or equivalent dolomitization required are explained as internal processes within the basin rather than secular variations in seawater chemistry the general hydrological evolution of the catalan subbasin is explained as a restricted subbasin with a first marine stage in which continental input up to 50 of total input had an important control on the geochemistry of the subbasin a second stage was determined during potash precipitation in which the subbasin was cut from any seawater input to end up in its last stage as a purely continental evaporitic basin coupling evaporation models and analytical results we have obtained the proportions of recycling and their sources estimated to change from a 100 total mass of sulphate eocene source to 20 eocene and 80 triassic keuper towards the latest stage of potash precipitation the results obtained have been compared with results from the navarrese subbasin allowing an integrated interpretation of the hydrological evolution of the whole upper eocene south

free hydrocarbons in uinta basin utah data indicate that wurtzilite is mainly alicyclic whereas gilsonite and albertite contain more aromatic structures however the presence of a substantial amount of condensed aromatic systems in general structure of the bitumens is not confirmed generation of the gilsonite from source oil shales has resulted in significant reduction of oxygen the changes in the character of the gilsonite and wurtzilite appear to be facies dependent but the difference between gilsonite and albertite is not only due to organic facies variation but also to significant diagenetic changes all evidence suggests that expulsion of the uinta basin bitumens except ozocerite has not been associated with any catagenetic changes the strong graphitizing potential of the uinta basin gilsonite w rtzilite and albertite suggests the absence or lack of thermally stable oxygen in the molecular structure of the bitumens and their source oil shales

occurrence of 20r and 20s δ8 14 and δ14 5α h sterenes and the origin of 5α h 14β h 17β h steranes in an immature sediment abstract series of 20r and 20s 8 14 and 145 h sterenes have been identified in an immature marl from a hypersaline deposit northern apennines italy by co injection studies with authentic compounds these alkenes co occur with 13 17 5 h spirosterenes and transient 20r and 20s 14 5 h 17 h sterenes the source of these isomeric steroid alkenes is probably 7 and 8 14 5 h sterols via 2 7 2 8 14 and 2 14 5 h steradienes reduction processes in the sediment via the 14 5 h 17 h sterenes can give rise to the c 20 isomeric 5 h 14 h 17 h steranes present in anomalously high relative abundances from a thermal maturity viewpoint this diagenetic pathway is supported by laboratory rearrangement hydrogenation experiments of 5 h cholest 7 ene and from considerations of carbon number distributions of various steroid hydrocarbons in the sediment extract

geochemistry origin and correlation of crude oils in lower cretaceous sedimentary sequences of the southern mesopotamian basin southern iraq abstract thirty one crude oil samples from lower cretaceous reservoirs in southern iraq were analyzed using bulk property and molecular methods to determine their maturity and biomarker characteristics as well as to obtain information on their respective source rocks all the oils are unaltered non biodegraded have high sulfur content and api gravity is in the range for light to heavy oil 19 40 api they are characterized by low pr ph values even odd predominance and front end biased n alkane distributions based on these parameters the oils were generated and expelled from a marine carbonate source rock bearing type ii s kerogen compositional similarities of hopane and sterane biomarkers with those from potential source rocks allowed identification of the upper jurassic lower cretaceous sulaiy and yamama carbonate succession as the effective source beds a similar composition of normal and isoprenoid hydrocarbons among the oils suggests an origin from a common source rock however biomarker maturity ratios indicate a wide range of maturity this appears to result from the type of burial history of the source rock characterized by a slow passage through the liquid window interval during an extended period of geologic time

modification of the petroleum system concept origins of alkanes and isoprenoids in crude oils kerogen the source material for petroleum can have a long history of alteration and diagenesis before crude oil forms a common assumption is that the bulk composition of the expressed oil reflects so much of these progressive alterations that most of the primary biological information of the original fixed carbon has been lost exceptions are trace constituents the biomarkers that comprise only a fraction of the organic material in most pristine crude oils analysis of the alkane acyclic isoprenoid fraction of a large number of crude oils and rock extracts from the timan pechora basin russia suggest that this fraction the main constituent of most crude oils is a direct product of liquefaction of biological debris that was preserved essentially unaltered to the point of oil generation therefore the primary biological provenance of this fraction is preserved in the oil fraction a set of gas chromatographic analyses of 242 crude oils as well as 83 solvent extracts from upper to middle paleozoic putative source rocks from the timan pechora basin russia were analyzed by a multivariate data analytical procedure new to organic geochemistry the distributions of n alkanes and acyclic isoprenoids 24 in all in the 325 samples could be reproduced by linear combinations of six end member compositions attributed to distinct biological inputs four of the six are assigned to primary producers waxes from higher plants cyanobacteria microalgae and the microorganism gloeocapsomorpha prisca these end members account for most of the n alkanes and acyclic isoprenoids in our samples the other two represent the products of secondary bacterial alteration of primary organics during sedimentation and low level bacterial alteration in the reservoir biodegradation each end member is composed of a spectrum of analytes whose abundances are related to one another by fixed ratios we surmise that each primary end member represents the breakdown of a resistant biopolymer that forms cell walls and partitions of a given biological group the n alkanes and acyclic isoprenoids in crude oils represent the weighted signatures of their various ancestors i e their primary organic inputs if the precursors of most oils are the products of a small set of chemically simple biopolymers then many of our assumptions concerning the importance of total organic carbon and the nature of the oil window must be reexamined

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

burial evolution of evaporites with implications for sublacustrine fan reservoir quality a case study from the eocene es4x interval dongying depression bohai bay basin china abstract eocene sublacustrine fan sandstones that developed in a rift basin are important tight gas reservoirs in the dongying depression bohai bay basin northeastern china two units of evaporites developed at the top and bottom of the lower unit of the es4 interval es4x consist predominantly of anhydrite with subordinate gypsum evaporite and related diagenetic processes greatly influenced reservoir quality 13 c values for micritic dolomite cements in es4x are depleted 7 45 to 2 57 due to microbial sulfate reduction msr under shallow burial conditions and this interpretation is supported by large 34 s fractionation between anhydrite and framboidal pyrite precipitation temperatures for micritic dolomite are calculated as 57 5 72 8 c anhydritization of gypsum probably occurred at 100 5 145 2 c during progressive burial as evidenced by homogenization temperatures of aqueous inclusions within anhydrite cements this process resulted in dehydration fractures within anhydrite cements that increased reservoir permeability by connecting isolated pores thermochemical sulfate reduction tsr probably resulted in dissolution of gypsum and anhydrite cements under relatively deep burial conditions ankerite cements are replaced by anhydrite cements and are enclosed by solid bitumen in es4x ankerite cements likely were derived from tsr as reflected in negative 13 c values 7 12 to 3 70 and high calculated temperatures 121 3 185 1 c dissolution by products e g saddle dolomite ankerite nodular pyrite related to tsr precipitated in adjacent pores a lack of significant 34 s fractionation between parent sulfate and nodular pyrite indicates that tsr occurred in a relatively closed system therefore dissolution of gypsum and anhydrite related to tsr contributed little to reservoir quality middle fan lithofacies with better sorting porosity and permeability than inner and outer fan lithofacies constitute high quality reservoirs in es4x

biomarker similarities between the saline lacustrine eocene green river and the paleoproterozoic barney creek formations abstract the paleoproterozoic barney creek formation which is currently interpreted as a restricted deep marine paleoenvironment plays a disproportionate role in our understanding of proterozoic ocean chemistry and the rise of complex life the barney creek formation hosts several unusual biomarker features specifically its methylhopane and carotenoid signatures herein we demonstrate that the saline lacustrine eocene green river formation shares a similar distribution of methylhopanes and carotenoids which is characteristic of saline lacustrine organic matter more generally these distinct methylhopane and carotenoid patterns are not observed together in marine organic matter of any geologic age these results imply a saline lacustrine depositional environment for the barney creek formation which agrees with earlier but now abandoned depositional models of this formation as a result models of proterozoic ocean chemistry and emergence of complex life that rely on a marine barney creek formation should be reexamined alternatively if paleoproterozoic marine biomarker signatures resemble those of younger saline lacustrine systems then this must be recognized to accurately interpret geologic biomarker and paleoenvironmental records

halite cementation and carbonate diagenesis of intra salt reservoirs from the late neoproterozoic to early cambrian ara group south oman salt basin late neoproterozoic to early cambrian carbonates of the ara group form important intra salt stringer reservoirs in the south oman salt basin differential loading of thick continental clastics above the six carbonate to evaporite cycles of the ara group led to the formation of salt diapirs encasing a predominantly self charging hydrocarbon system within partly highly overpressured carbonate bodies stringers these carbonates underwent a complex diagenetic evolution with one stage of halite cementation in a shallow early and another in a deep late burial environment early and late halite cements are defined by their microstructural relationship with solid bitumen the early phase of halite cementation is post dated by solid reservoir bitumen this phase is most pervasive towards the top of carbonate stringers where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics bromine geochemistry revealed significantly higher bromine contents up to 280 p p m in the early halite compared with the late halite 173 p p m the distribution patterns and the high bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval later in burial history relatively small quantities of early halite were dissolved locally and re precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements late halite cement also seals fractures which show evidence for repeated reopening initially these fractures formed during a period of hydrothermal activity and were later reopened by a crack seal mechanism caused by high fluid overpressures porosity plugging by early halite cements affects the poroperm characteristics of the ara carbonates much more than the volumetrically less important late halite cement the formation mechanisms and distribution patterns of halite cementation processes in the south oman salt basin can be generalized to other petroliferous evaporite basins

re os geochronology and os isotope fingerprinting of petroleum sourced from a type i lacustrine kerogen insights from the natural green river petroleum system in the uinta basin and hydrous pyrolysis experiments abstract rhenium osmium re os geochronology of marine petroleum systems has allowed the determination of the depositional age of source rocks as well as the timing of petroleum generation in addition os isotopes have been applied as a fingerprinting tool to correlate oil to its source unit to date only classic marine petroleum systems have been studied here we present re os geochronology and os isotope fingerprinting of different petroleum phases oils tar sands and gilsonite derived from the lacustrine green river petroleum system in the uinta basin usa in addition we use an experimental approach hydrous pyrolysis experiments to compare to the re os data of naturally generated petroleum in order to further understand the mechanisms of re and os transfer to petroleum the re os geochronology of petroleum from the lacustrine green river petroleum system 19 14 ma all petroleum phases broadly agrees with previous petroleum generation basin models 25 ma suggesting that re os geochronology of variable petroleum phases derived from lacustrine type i kerogen has similar systematics to type ii kerogen e g selby and creaser 2005a selby and creaser 2005b finlay et al 2010 however the large uncertainties over 100 in some cases produced for the petroleum re os geochronology are a result of multiple generation events occurring through a 3000 m thick source unit that creates a mixture of initial os isotope compositions in the produced petroleum phases the 187os 188os values for the petroleum and source rocks at the time of oil generation vary from 1 4 to 1 9 with the mode at 1 6 oil to source correlation using os isotopes is consistent with previous correlation studies in the green river petroleum system and illustrates the potential utility of os isotopes to characterize the spatial variations within a petroleum system hydrous pyrolysis experiments on the green river formation source rocks show that re and os transfer are mimicking the natural system this transfer from source to bitumen to oil does not affect source rock re os systematics or os isotopic compositions this confirms that os isotope compositions are transferred intact from source to petroleum during petroleum generation and can be used as a powerful correlation tool these experiments further confirm that re os systematics in source rocks are not adversely affected by petroleum maturation overall this study illustrates that the re os petroleum geochronometer and os isotope fingerprinting tools can be used on a wide range of petroleum types sourced from variable kerogen types

the origins of the mengye potash deposit in the lanping simao basin yunnan province western china abstract the lanping simao basin lsb is a mesozoic cenozoic continental margin rift basin in western china it formed during the opening and closing of the tethys ocean this basin is also known as a metal belt as it hosts several metal deposits besides the mengye potash deposit however the exact dates of the formation either in the paleocene or the cretaceous and thus the origins of the marine continental or mixed origins of the mengye deposits remain disputed based on the basin s evolution materials of marine origin and or remnant seawater should be present but instead the salt layers of the mengye potash deposit present typically continental lithological features this study examines and reviews evaporative minerals br cl and i cl molar ratios and isotopes of s b and sr i and i cl data for this area has not been previously reported the basin s evaporative minerals are dominated by halite and sylvite the amounts of anhydrite chlorocalcite langbeinite glaserite tachyhydrite and glauberite are small all of these form in both marine and continental environments the values of i and the i cl molar ratios of halite and sylvite are from 0 07 to 0 27 ppm and from 0 03 to 0 11 10 6 respectively dependent on organic substances br and molar br cl values are from 89 08 to 555 45 ppm and from 0 06 10 3 to 0 38 10 3 respectively all of the br cl molar ratios are lower than those of seawater and most of them are 34 s 11 b and 87 sr 86 sr values for evaporative minerals indicate a continental origin for the mengye potash deposit however materials of hydrothermal origin are widely distributed in the basin and may have played an active role for the formation of the potash deposit thus the mengye potash deposit could be of continental origin with a remnant seawater trace

using the cl br ratio as a tracer to identify the origin of salinity in aquifers in spain and portugal summary a study on the applicability of the cl br molar ratio for identifying the origin of groundwater salinity is presented according to the experience gained in spain and portugal cl br ratios in atmospheric bulk deposition have helped to distinguish groundwater in which cl derives only from atmospheric sources from groundwater in which cl is contributed by endogenous lithological or anthropogenic sources considering the seawater cl br ratio of 655 4 cl br ratios may be increased up to 1500 in groundwater by the addition of wastewater loaded with nacl or leaching of solid waste and decreased to 300 by the use of br based pesticides or leaching farm animal or septic waste leaching and dissolution of natural and industrial nacl and of gypsum rich formations containing some nacl may yield cl br ratios between one thousand and several thousand although leaching of potassium halides near salt mines produces cl br ratios below the seawater ratio when cl content in groundwater is not affected by extreme evaporation up to halite saturation at 6 2 mol l 1 of nacl and if there are no other cl sources recharge by rainfall can be estimated by relating cl in atmospheric bulk deposition to derived groundwater the cl br ratio appears to be a good tracer for discriminating non atmospheric cl contributions to groundwater provided chemical analyses are accurate since its variability is not wide data have been collected from different areas of spain and portugal and are explained and illustrated by two cases described in detail the donana aquifer in southwest spain and the canary islands both showing the mixing paths