the record of the messinian salinity crisis in the tertiary piedmont basin nw italy the alba section revisited abstract the alba succession tertiary piedmont basin nw italy preserves the northernmost record of the messinian salinity crisis msc and was deposited on the southern margin of a wide wedge top basin related to the involvement of the piedmont basin in the apennine compressional tectonics pre msc sediments consist of a cyclic succession of marine euxinic shales and calcareous marls deposited under the influence of precession modulated climate changes and document the progressive restriction of the basin prior to the onset of the msc they are followed by the primary lower gypsum unit plg deposited during the first msc stage from 5 96 to 5 60 ma these sediments show a clear precession related cyclic stacking pattern and record the lateral transition from a shallow water marginal setting in the sw to a deeper one in the ne in marginal settings six plg cycles are recognised truncated by an erosional unconformity placed at the base of the post evaporitic sediments the lowermost five cycles are composed of massive and banded selenite beds separated by thin shale intervals a sharp change evidenced by the appearance of the branching selenite facies is recorded by the 6th gypsum bed that represents a distinctive marker bed here called sturani key bed that can be mapped throughout the study area basinward the lower plg cycles are transitional to decimetre thick carbonate rich layers interbedded to euxinic shales that are overlain by the sturani key bed above the marker bed other seven plg cycles are present the gypsum beds form thinner bodies compared to the sturani key bed and are characterised by a greater amount of fine grained terrigenous fraction suggesting an increase of continental runoff related in turn to humid climate conditions at the end of the first msc stage plg cycles are followed by slumped mudstones and clastic gypsum beds that correspond to the resedimented and chaotic facies resedimented lower gypsum deposited in the mediterranean basins during the second msc stage from 5 60 to 5 55 ma they are in turn overlain by continental and brackish water facies with lago mare fossil assemblages recording the final stage of the msc the messinian succession of alba provides the opportunity to reconstruct the lateral facies transition between marginal and distal settings and to shed new light on the deep water msc sedimentary record moreover the appearance of the branching selenite facies from the 6th plg cycle upward provides a tool for properly placing the piedmont record in the msc chronostratigraphic framework allowing us to investigate the influence of climate gradients on the sedimentary response to the mediterranean salinity crisis

stratigraphy and strontium geochemistry of messinian evaporite bearing successions of the southern apennines foredeep italy implications for the mediterranean salinity crisis and regional palaeogeography an integrated study comprising detailed mapping stratigraphy evaporite facies analysis strontium content and 87sr 86sr ratio data is presented for two messinian evaporite bearing units cropping out in irpinia daunia mountains southern apennines italy these units record the tectonic and palaeogeographic evolution of the messinian southern apennine foreland basin system during the abrupt salinity crisis which occurred in the mediterranean region the daunia unit comprises the monte castello evaporites formed by euxinic diatomitic marls evaporitic limestones and shallow water gypsum having a 87sr 86sr average value of 0 70898 0 00005 close to the sr isotopic value of the coeval seawater these marginal evaporites are capped by an erosional unconformity and continental clastic deposits the vallone del toro unit is made up of thin bedded marls claystones calcilutites and diatomite layers with small gypsum crystals laminated gypsum and gypsarenite testifying deposition in relatively deep water settings gypsum has variable sr isotopic data with an average value of 0 70899 0 00005 for the argilliti policrome del torrente calaggio formation and an average value of 0 70863 0 00014 for the argilliti di mezzana di forte formation reflecting major riverine freshwater input the different patterns of lithofacies and sr isotopic composition of gypsum discriminate two distinctive evaporite units reflecting the tectonic and palaeogeographic controls within the apennines mountain belt and the mediterranean data for evaporites of the southern apennines testify the presence of basins in the central and eastern mediterranean sea which never desiccated during the entire salinity crisis and evolved to widespread lago mare conditions in the latest messinian

distinguishing climatic and tectonic signals in the sedimentary successions of marginal basins using sr isotopes an example from the messinian salinity crisis eastern mediterranean the evolution of oceanic 87 sr 86 sr through the tertiary has been sufficiently well documented to provide a useful stratigraphic tool for carbonate rich marine sediments which were deposited in basins connected to the global oceans in isolated basins sea water 87 sr 86 sr will diverge from coeval oceanic values thus if independent age information exists the geochemical signature can constrain the timing of isolation in marginal basins formed in tectonically active settings the timing of isolation is critical to the assessment of the relative importance of climate or tectonic controls on that event previously isolation has been assumed to coincide with the last occurrence of open marine fauna however in an example from the eastern mediterranean 87 sr 86 sr data challenge that assumption and can be interpreted as indicating a protracted period of isolation c 3 ma during which time marine conditions prevailed prior to the messinian salinity crisis at the end of the miocene this allows tectonic and climatic signals to be distinguished since although convergence of africa with eurasia was responsible for isolation of this part of the mediterranean it is more likely that later climatic change triggered desiccation

modelling the effect of evaporation on the salinity 87 sr 86 sr relationship in modern and ancient marginal marine systems the mediterranean messinian salinity crisis abstract palaeosalinity reconstructions in marginal marine environments based on sr isotope data assume simple two end member mixing of river and ocean water an improved model that incorporates the effect of evaporation is used to demonstrate that this approach is not valid in evaporation dominated systems however sr isotope records combined with faunal and lithological constraints on salinity can be used to assess the palaeohydrological conditions of ancient marginal marine systems this new method is used to interpret deviations from the global seawater sr isotope curve observed in mediterranean successions during and up to 3 myr prior to messinian evaporite deposition results suggest that no absolute change in the net evaporation flux is required to explain the three to four fold rise in salinity of mediterranean water at the carbonate evaporite transition modelled sr isotope records indicate that this increase in salinity was synchronous with an increase in the dominance of atlantic water inflow in the hydrological budget of the mediterranean the messinian salinity crisis may therefore have been the response to a marine transgression

spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

sr s and oso4 isotopes and the depositional environments of the upper miocene evaporites spain abstract upper miocene evaporites in the nijar basin southeastern spain contain thick massive and coarse crystalline selenites of the middle messinian yesares formation on the basis of their sedimentary fabrics and structures such as euhedral terminations of crystals well preserved algal filament inclusions and standing growth orientations these selenites are interpreted to be primary bottom growth deposits most of these selenites have sr concentrations of about 1000 ppm range from 700 to 1800 ppm 87sr 86sr values of yesares selenites vary between 0 70890 and 0 70896 n 18 which are all within the known range of messinian seawater suggesting a marine origin however quantitative modeling of 87sr 86sr vs sr ca of fluids demonstrates that a minor amount of admixed nonmarine fluid e g 20 might have contributed to the yesares marine brines 34s and 18oso4 values of yesares selenites range from 21 to 24 cdt and from 10 to 16 smow respectively these ranges are more variable and most values are heavier than those expected for normal miocene marine gypsum on the basis of quantitative modeling these heavy 34s and 18oso4 values have most likely resulted from reduction and oxidation reactions of sulfur species that occurred in brines rather than from contributions of nonmarine water or from reservoir crystallization effects the use of sr s and o isotopes provides a possible means of distinguishing whether an ancient evaporite was deposited by marine nonmarine or hybrid brines sr isotopes however are insensitive to minor nonmarine contributions on the basis of quantitative modeling and consequently marine sr isotopes for evaporites e g gypsum do not necessarily indicate pure marine depositional environments compared to sr isotopes 34s and 18oso4 of marine gypsum are even more insensitive to minor nonmarine contributions because of much higher so4 concentrations in seawater and seawater evaporated brines than in most freshwaters therefore sr o and s isotopes should be used with caution to interpret depositional environments and to determine parent fluids of ancient evaporites

barnett shale gas production fort worth basin issues and discussion newark east barnett shale field fort worth basin texas is currently the most productive gas field in texas in terms of daily production and is growing at an annual rate of more than 10 however despite the fact that the barnett play has been studied intensely by very capable geologists and engineers from several companies over a period of many years there continues to be several misunderstandings concerning fundamental factors controlling the success of the barnett play of north texas barnett gas production is poorer in areas near faults and structural flexures anticlines and synclines fractures which are most abundant in these structural settings are detrimental to barnett production open natural fractures are rare in the barnett and have little or nothing to do with barnett productivity in areas where barnett shale is thermally mature with respect to gas generation it is slightly overpressured about 0 52 psi ft 11 76 kpa m limestone beds within the barnett formation are the product of debris flows that originated on a carbonate shelf to the north of the present basin center it appears that the barnett can be used as an exploration model for other basins especially analogous basins of the ouachita trend the history of the development of the barnett reservoir in north texas provides an excellent example of how persistence can lead to success in nonconventional gas plays

1d and 2d nuclear magnetic resonance nmr relaxation behaviors of protons in clay kerogen and oil bearing shale rocks abstract few 1d t2 and 2d t1 t2 nuclear magnetic resonance nmr studies have focused on oil bearing shales with complex constituents and a deeper understanding of the nmr relaxation behaviors of oil confined in shale is needed in this paper a series of t2 and t1 t2 nmr experiments were performed on oil bearing shale and its components clay minerals and kerogen to obtain the t1 t2 fluid typing chart and analyze the adsorbed and free oil in shale the results were as follows five types of water bound adsorbed free crystal and structural water in clay minerals were qualitatively identified and described by the specific t2 to t1 t2 ratio values and t1 t2 maps were used to qualitatively indicate the clay type the t1 t2 fluid typing chart containing the signatures of 8 proton populations in oil bearing shale was defined and included bulk liquid macropore 1000 nm oil nanopore

the messinian marine to nonmarine gypsums of jumilla northern betic cordillera se spain isotopic and sr concentration constraints on the origin of parent brines the origin of the messinian hoya de la sima hs gypsum betic foreland is constrained using 87sr 86sr 34s sr concentration and petrographic data the lower and middle hs units consist of subaqueous vertically aligned and stromatolitic selenites the latter containing unusual microbial depositional textures the upper unit consists of very shallow water bioturbated lenticular gypsum with paracamelus ichnites 87sr 86sr and 34s indicate precipitation from predominantly marine waters with upward increasing continental influence mixing models between messinian seawater and continental water that dissolved triassic evaporites show that the percentages of seawater required to explain the measured 87sr 86sr are analogous to the percentages obtained using 34s supporting precipitation from such mixtures 87sr 86sr and 34s of lower hs selenites resemble those of the primary lower gypsum plg of the messinian salinity crisis msc in both cases indicating precipitation from seawater continental water mixtures in which most sr and so4 were supplied by messinian seawater in the lower hs selenites sr concentrations indicate contributing continental waters with sr ca ratios similar to seawater however sr concentrations of plg selenites from other betic basins bajo segura sorbas indicate parent waters with sr ca ratios lower than seawater if the sr contents of the betic plg selenites are representative it is unlikely that the lower hs selenites represent the plg however we cannot completely discard that option since different lpg subbasins could have had variable sr ca the hs gypsums formed coevally to diapirism of triassic evaporites in a restricted lagoonal basin developed during or slightly after a phase of strike slip faulting in the betic cordillera more general implications of this work are that sr concentrations combined with 87sr 86sr and 34s data provide key constraints on the origin of parent brines and using sr concentrations as paleosalinity proxy in gypsum precipitated from seawater continental water mixtures is inconclusive because they largely depend on the initial sr ca ratio of the brine this study also illustrates that the electron microprobe is ideal to obtain reliable spatially resolved sr concentration data in selenitic gypsum these data in combination with fluorescence petrography provide valuable criteria to discriminate primary depositional from diagenetic gypsum a critical step in the interpretation of geochemical data

a modeling perspective on spatial and temporal variations in messinian evaporite deposits abstract during the messinian salinity crisis msc evaporite dominated sequences formed in marginal and deep basins of the mediterranean sea in the marginal basins the onset of the msc is synchronous and a single depositional framework fits all sequences in contrast msc sequences of the western and eastern deep basins appear to comprise a different number of units and differ greatly in thickness even though there exist numerous scenarios for deposition in the marginal and deep basins the link between the two settings is difficult and scenarios are rarely quantitatively supported we employ a simple box model for the messinian mediterranean to examine the causes of 1 spatial variation in thickness and 2 differences in the time of onset of deposition model results are compared with actual observations on the msc sequences the results show that a large connection between the western and eastern basin is necessary for and some degree of water column stratification is conducive to synchronous onset of the msc in the marginal basins moreover halite deposits in the deep basins are likely to be coeval and have formed in 60 ka after a further restriction of the atlantic mediterranean connection during the msc but without a significant sea level drop a difference in the net salt gain per unit volume caused the different halite deposition rates in the two basins a scenario with only a simple restriction of the atlantic mediterranean connection during the late miocene without significant changes in the mediterranean sea level the fresh water budget or the size of the strait of sicily is able to explain the synchronous onset of the msc the synchronous marginal evaporite formation and the differences in the deep basinal sequences

petrophysical characterization of oil bearing shales by low field nuclear magnetic resonance nmr abstract shales are important components of petroleum systems and it is necessary to reveal their petrophysical properties as reservoirs low field nuclear magnetic resonance nmr has proven to be a non invasive and effective technique for petrophysical characterization of sandstone carbonate and coal however little study has been done using this technique to systematically investigate the petrophysical properties of oil bearing shales which is essential for characterizing shale oil reservoirs in this study two sets of nmr measurements were performed to reveal the porosity permeability movable fluid volume and pore size distribution psd of oil bearing shales the results show the following 1 the nmr t2 spectrum strongly relates to the content of quartz and the amount of dissolution pores within shale three t2 spectrum peaks were identified by the relaxation times at 0 03 1 ms 1 20 ms and 20 ms corresponding to micropores 1000 nm respectively 2 by combining nmr with centrifugation both nmr porosity and movable porosity mp were calculated nmr porosity is well consistent with helium porosity and the mp values strongly relate to the development of mesopores in shales 3 based on the t2 spectrum an effective permeability model was proposed which can conveniently estimate the permeability of shales moreover two classical permeability models coates and sdr were also used to estimate shale permeability and the permeability values determined by these models agrees well with helium permeability 4 in combination with sem images analyses an nmr based psd was constructed that agrees well with the psd determined by sem the results demonstrate the applicability of nmr relaxation in a systematic investigation of the petrophysical properties of shales which has potential applications for geophysical logging in shale oil exploration

fractal characteristics of upper cretaceous lacustrine shale from the songliao basin ne china abstract to improve our understanding of the characteristics of nanopores and their influence on liquid hydrocarbon occurrences in lacustrine shale we carried out fractal analysis on 21 lacustrine shale cores from the upper cretaceous qingshankou formation k2qn in the songliao basin ne northeast china using toc total organic carbon and rock eval analysis xrd x ray diffraction low pressure nitrogen adsorption experiments and the fhh frenkel halsey hill method the relationships between composition of lacustrine shale toc minerals oil content the pore structure parameters bet surface area pore volume pore average diameter and the fractal dimensions were investigated two fractal dimensions d1 and d2 at relative pressures of 0 5 1 and 0 0 5 respectively were obtained with d1 ranging from 2 5055 to 2 8888 and d2 between 2 1026 and 2 733 d1 is greater than d2 indicating that small pores are more homogeneous than larger pores both d1 and d2 increase with increasing bet surface areas and total pore volumes and increase with decreasing average pore diameters the fractal dimensions of lacustrine shale are negatively correlated with the clay content but show no obvious relationship with the quartz content the relationship between fractal dimensions both d1 and d2 and toc content is a u shaped curve with minimum d values at 2 5 3 wt toc fractal dimension d1 can be used to characterize the shale oil content and lacustrine shale samples with a lower fractal dimension have greater free oil therefore considering the influence of toc content on fractal dimension and the relationship between oil content and fractal dimension we conclude that lacustrine shale in the oil generation stage with 2 5 3 0 wt toc is probably the preferred shale oil exploration target in the songliao basin the results indicate that fractal analysis leads to a better understanding of the pore structure and oil storage capacity of lacustrine shale

sedimentary and tectonic evolution of the vena del gesso basin northern apennines italy implications for the onset of the messinian salinity crisis the integration of field and subsurface data permits a substantial revision of the sedimentary evolution of the vena del gesso basin a thrust top basin in the northern apennines where shallow water primary gypsum deposits related to the messinian salinity crisis were well developed and preserved as inferred from lateral and vertical facies changes within the underlying deep marine turbidites of the marnoso arenacea formation evaporite precipitation occurred in a basin bounded to the north and to the east by a thrust related anticline actively growing since the late tortonian both gypsum deposition and subsequent deformation were strongly controlled by evolving paleobathymetry driven by tectonics primary gypsum precipitated in a shallow silled basin while in the adjacent deeper and larger foredeep basin organic rich shales were deposited gypsum deposits underwent severe postdepositional deformation related to large scale gravitational collapse as a result of a regional uplift event also coincident with the end of the evaporitic phase along the inner shallower dipping limb of the anticline bounding the basin large scale poorly deformed gypsum slabs moved downslope along a detachment surface developed at the contact with the underlying euxinic shales forming both extensional and compressional features and showing an overall southwestern vergence the identification of a south southwest dipping paleoslope here pointed out for the first time suggests that the deformational features affecting the gypsum unit were probably driven by gravity and not by active thrusting as thought up to now the steeper frontal limb of the anticline promoted the transformation of gypsum slides into debris flows and turbidite currents that deposited their load in the adjacent deeper basin this gravitational deformation was sealed by postevaporitic upper messinian lagomare deposits the sedimentary history of the vena del gesso basin suggests that the messinian salinity crisis in the apennine foredeep as well as in the balearic tyrrhenian sicily and eastern mediterranean basins was tightly linked to tectonic processes the large scale postdepositional collapse of primary evaporitic deposits is a widespread feature in the mediterranean basins and it may have altered the original stratigraphic relationships in some places this finding has potentially important implications for a correct paleoenvironmental reconstruction of the onset of the messinian salinity crisis

identifying late miocene episodes of connection and isolation in the mediterranean paratethyan realm using sr isotopes abstract after decades of research the timing and nature of late miocene connections between the mediterranean paratethys and the global ocean are still speculative the hydrologic flux implications of exchange or isolation are central to all hypotheses for generating the major lithological changes that represent the messinian salinity crisis moreover differences in the hydrologic fluxes envisaged are the primary distinction between models despite this these fluxes remain largely unconstrained this paper describes the basis for using sr isotope data innovatively combined with salinity data through hydrologic budget modelling to determine the timing and nature of mediterranean hydrologic connectivity we examine the hypotheses for three late miocene events to illustrate how this approach allows us to test implied hydrologic scenarios and exclude incompatible models 1 pre evaporite restriction of the mediterranean 2 the initiation of salt precipitation 3 connection between the sea of marmara and both paratethys and the mediterranean during the messinian this process suggests that the atlantic mediterranean exchange was significantly reduced up to three million years before evaporite precipitation it also indicates that end member hypotheses for initiating salt precipitation in the mediterranean desiccation and connected basin models are inconsistent with sr isotope data a contrasting model where evaporite formation was triggered by atlantic transgression into a strongly evaporation dominated mediterranean is shown to be more compatible with available datasets the application to sea of marmara samples indicates that salinity changes in the basin were not caused by changes to the amount of inflow from either paratethys or the mediterranean other possible as yet untested applications important for constraining different aspects of the messinian salinity crisis are highlighted

the importance of recycling processes in the middle miocene badenian evaporite basin carpathian foredeep palaeoenvironmental implications the middle miocene badenian evaporitic succession within the carpathian foredeep poland has been conventionally described as formed in a purely marine basin until recently data from this basin have been used to deduce the sulphate isotopic composition of the ocean during the miocene and to describe evolution of major elements in seawater this paper presents a new interpretation proving major continental inputs and ongoing recycling processes it is based on detailed petrographical mineralogical studies x ray microanalysis of primary fluid inclusions in halite cryo scanning electron microscopy sem energy dispersive microanalysis eds isotopic analysis y 34 s and y 18 o in sulphates and computerbased evaporation models two boreholes wojnicz intersecting the halite succession in the centre of the basin and

microdistribution and mobility of water in gas shale a theoretical and experimental study abstract multiphase adsorbed and free liquid water that is accumulated in shale matrix pores i e pore water substantially affects the storage and transport of gas in shale traditionally used macroscopic parameters e g initial irreducible mobile and clay bound water saturations are not sufficient to describe the microdistribution characteristics and mobility of pore water in the complex porous shale matrix in this paper a new classification was proposed in which the pore water is composed of adsorbed and free parts of which the latter is subdivided into capillary bound and mobile water the components of pore water have the following features during the centrifugation process a adsorbed water is essentially immobile while free water is potentially mobile b capillary bound water is gradually transformed into mobile water with increased centrifugal pressure difference and c the maximum mobile water amount is numerically equal to the free water amount based on the classification an effective technique which integrates centrifugation water imbibition and low temperature nitrogen adsorption methods with the modified li s adsorption ratio equation 2018 was established to quantitatively evaluate the microdistribution characteristics adsorbed and free amounts and their ratios and the mobility mobile amount potential and capacity of pore water in marine shales from the southern sichuan basin in china furthermore the mechanism of controlling the microdistribution and mobility of pore water is analyzed with respect to the microscopic pore structure characteristics and material compositions of shales the primary results demonstrate that 1 adsorbed and free water amounts obtained by centrifugation tests range from 5 145 to 31 282 mg g adsorbed and from 7 880 to 49 751 mg g free the weight ratio of adsorbed water is 0 268 0 629 2 the mobile potential and mobile capacity of pore water are represented by the free water amount and mid value pressure difference respectively a positive relationship between these two parameters occurs in the studied shales 3 pore microstructure characteristics of shale mainly impact the microdistribution and mobility of pore water in the shale matrix the adsorbed water amount is closely associated with the specific surface area of pores while the free and mobile water amounts are controlled by the pore volume the ratios of adsorbed and free water depend on the size and morphology of pores for certain state parameters the mobile ratio is impacted by pore complexity which indicates that as the complexity increases the mobile ratio decreases the study provides significant insight into the microdistribution and mobility of pore water in gas shale matrix

water saturation driven evolution of helium permeability in carboniferous shale from qaidam basin china an experimental study abstract permeability is an important parameter for describing the transport properties of gas shales this study investigates the effects of water saturation on stress dependent permeability and the slip factor of carboniferous shales in the qaidam basin china to analyze correlations between water saturation effective stress helium permeability and slip factor helium permeability of 12 shale samples with different water saturation at pore pressures up to 6 89 mpa and effective stresses up to 27 58 mpa at 25 c is measured subsequently shale characteristics including mineral composition total organic carbon toc content thermal maturity vitrinite reflectance and pore structure distribution psd pore volume and type are determined the analyses reveal a consistent exponential relation between apparent effective gas permeability at 6 89 mpa and effective stress the apparent effective helium permeability at 4 13 mpa decreases exponentially with increasing water saturation particularly in shale samples with a high intrinsic permeability the critical water saturation value of shale is 30 40 two different modes of gas water two phase flow are observed when water saturation is 30 helium permeability decreases sharply and gas water flow in the shale samples appear as channel flow however when water saturation is 40 helium permeability slowly decreases gas water flow in the shale samples appear as funicular flow gas and water simultaneously flow in all capillaries and thin films of structured water on mineral surfaces reduce the pore throat diameter thus increased water films in narrow flow paths increase the gas slippage effect furthermore the slip factor initially decreased with increasing water saturation before increasing helium permeability exhibits a negative correlation with toc and clay contents and a positive correlation with quartz content the micropores and mesopores in samples with high clay content and toc are favorable to gas adsorption but not to gas transport permeability measurements of humidity oven dried samples reveal a power law relation between the gas slip factor and klinkenberg corrected permeability the slope of the resulting curve 0 29 is lower than that obtained for low permeability gas sands this study provides practical information for further studies of shale gas migration and the gas slippage effect in certain gas water flows

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

investigation of pore structure and fractal characteristics of organic rich shale reservoirs a case study of lower cambrian qiongzhusi formation in malong block of eastern yunnan province south china abstract in order to study pore structure and fractal characteristics of the organic rich marine shale fourteen shale samples from lower cambrian qiongzhusi formation in malong block of eastern yunnan province were investigated by organic geochemical analysis total organic carbon content analysis and thermal maturity analysis x ray diffraction xrd analysis porosity and permeability tests field emission scanning electron microscopy fe sem low pressure nitrogen adsorption and methane adsorption experiments fractal dimensions d 1 and d 2 at relative pressure of 0 0 5 and 0 5 1 respectively were obtained from the nitrogen adsorption data using the fractal frenkel halsey hill fhh method not only have the relationships among pore structure parameters of shale the relationships between toc content mineral compositions pore structure parameters and fractal dimensions been discussed but also the significance of two fractal dimensions d 1 and d 2 and the impact of fractal dimensions on adsorption capacity have been investigated the results showed that fourteen shale samples have toc content ranging from 1 25 to 7 72 two fractal dimensions both increase with the increasing toc content and gradually come to a standstill the curves present the shape of parabola the major mineralogical compositions of shales are quartz and clay minerals the quartz contents are between 25 5 and 42 7 the clay contents are between 26 6 and 44 2 fractal dimension d 1 has a negative correlation with quartz contents and a positive correlation with clay minerals contents but fractal dimension d 2 has no apparent relationship with quartz and clay minerals contents the specific surface area is in the range of 4 98 m 2 g 19 66 m 2 g the total pore volume is between 0 00479 cm 3 g and 0 01765 cm 3 g and the average pore diameter is between 3 37 nm and 6 02 nm two fractal dimensions increase with the increasing surface area and pore volume and also increase with the decreasing average pore diameter because of the complicated pore surface and structure of small pores further investigation indicates that d 1 represents fractal characteristics from the irregular pore surface while d 2 represents fractal characteristics related to the complicated pore structure and shale samples with larger fractal dimensions have higher methane adsorption capacity therefore fractal analysis is helpful to have a better understanding of pore structure and adsorption capacity of marine shale

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

the record of the messinian salinity crisis in mobile belts insights from the molise allochthonous units southern apennines italy abstract mediterranean marginal basins recorded the messinian salinity crisis msc in various structural settings including syn rift thrust top foredeep and foreland basins during the msc the apennines were one of the mobile belts of the peri mediterranean chain starting from more hinterland areas allochthonous units of both the northern and southern apennines migrated toward the adriatic foreland developing allochthonous top sedimentary basins one of these basins on top of the molise allochthonous units southern apennines recorded almost all of the main steps of the msc in a gypsum quarry district the occurrence of conduits yielding flow mobilized sediments which cross cut the lower evaporites testifies to a fluid migration event responsible for the formation of a brecciated mudgrade limestone buildup this event can be connected with the mediterranean drawdown responsible for the messinian erosional surface mes the post evaporitic marly succession that unconformably overlies the lower evaporites and the brecciated limestones is characterized by the presence of paratethyan molluscs and ostracods loxoconcha muelleri and loxocorniculina djafarovi zones and small mammals among which is recorded the occurrence of stephanomys debruijni a disconformity within the post evaporitic succession divides it into lower p ev1 and upper p ev2 lago mare deposits a further erosional surface separates the messinian lago mare sediments from fully marine lower zanclean mpl2 zone deposits whilst the unconformity separating the lower evaporites and the lago mare deposits although enhanced by a tectonic event could be related to a late messinian base level drop mes1 as well as the disconformity between p ev1 and p ev2 mes2 the younger angular unconformities affecting both the lago mare deposits p ev2 and the fully marine pliocene sediments might be related to two different phases of orogenic transport those events affected the molise allochthonous units during their late miocene early pliocene forelandward migration

the mediterranean messinian salinity crisis an apennine foredeep perspective abstract owing to its expanded stratigraphic sections the apennine thrust belt offers the opportunity to better understand the evaporitic and post evaporitic messinian events a physical stratigraphic framework of messinian deposits based on facies analysis and basin wide correlation of key surfaces and sedimentary cycles is presented it is shown that the messinian apennine foredeep had marginal basins with shallow water primary evaporites and deeper basins where resedimented evaporites accumulated under relatively deep water conditions like many other mediterranean examples primary shallow water evaporites of apenninic marginal basins show evidence for subaerial exposure and erosion however the development of such an erosional surface does not correspond to the deposition of primary evaporites in the deepest part of the basin s here the unconformity can be traced towards the base of resedimented evaporites or to a level within them implying that the deeper basins of the apennine foredeep never underwent desiccation during the messinian salinity crisis but rather received the eroded marginal evaporites this fact usually overlooked raises important questions about the deep desiccation model of the mediterranean

the primary lower gypsum in the mediterranean a new facies interpretation for the first stage of the messinian salinity crisis abstract the detailed facies and physical stratigraphic analysis of the primary lower gypsum in the mediterranean indicates a surprising bed by bed correlation at basin scale spain italy hellenic arc and cyprus arc that is tuned to the orbital calibration for the first stage of the messinian salinity crisis from 5 96 to 5 61 ma ago a total of 16 precessionally controlled gypsum cycles were deposited rapidly in less than 350 ka forming sequences up to 300 m thick the lack of subaerial exposure features and the common facies associations and stacking pattern for sections located thousands of kilometers apart in different geological settings indicates a modest depositional depth not extremely shallow selenite deposition occurred only at the bottom of restricted marginal basins less than 200 m deep while no gypsum could precipitate in the deeper euxinic mediterranean portions where only thin and barren shale dolostone couplets formed the lowermost selenite beds pass laterally to dolomite rich limestones interbedded with barren euxinic shales in poorly oxygenated settings indicating that the gypsum sedimentation was diachronous and did not necessarily mark the onset on the messinian salinity crisis evaporite facies sequences ef1 to 8 within individual gypsum beds show small scale subaqueous sedimentary cycles that mimic regressive transgressive cycles a initial evaporite precipitation at relatively low supersaturation produced the massive selenite facies ef3 in a relatively deep setting b continuous evaporation and drawdown by oscillating brine level formed the banded selenite ef4 at the aridity acme of the precessionally controlled cycle c general progressive brine level rise with strong brine flow led to the formation of large selenite supercones branching laterally supercones in spain and branching selenite ef5 in the rest of the mediterranean and d flooding by undersaturated continental water terminated gypsum precipitation with the deposition of argillaceous sediments ef1 northern apennines and or limestone ef2 sicily and spain during the humid phase in the precession climate cycle the stacking pattern and selenite facies associations suggest an overall shallowing upward trend with a basin wide hydrologic change starting from the 6th cycle 5 84 ma which is marked by the appearance of the branching selenite facies supercones in spain and indicates that the brines became current dominated the sr isotope stratigraphy suggests that in the northern apennines the brines were strongly modified by continental waters 87 sr 86 sr 0 708893 to 0 708998 and received direct pulses of atlantic seawater 87 sr 86 sr 0 70900 to 0 709024 only in the upper part of the section in areas away from the mainland such as sicily the continental input was by far less important

the origin of sulfate mineralization and the nature of the baso4 srso4 solid solution series in the ain allega and el aguiba ore deposits northern tunisia abstract ain allega and el aguiba are among the largest barite celestite deposits attributed to the triassic period in tunisia they are located in the flysch zone on the eastern edge of the triassic diapir of jebel hamra the ore body consists of dolomite intensely brecciated and surrounded by marls clay gypsum and dolomite which forms the hanging wall of the deposit and rimmed by paleocene marls the ore minerals show a cap rock type mineralization with various forms and types in particular impregnation in dolomite breccia cement replacement of carbonate cap rock and open space filling in the dissolution cavities and fractures ore minerals include sphalerite galena marcasite and pyrite principal gangue minerals are barite celestite calcite dolomite and quartz the ore minerals are hosted by the triassic carbonate rocks which show hydrothermal alteration dissolution and brecciation the study of barite celestite solid solution shows a bimodal distribution in which the composition is not continuous some intermediate compositions are missing 20 80 srso4 for the el aguiba ore deposit and 50 70 srso4 for the ain allega ore deposit x ray diffraction peaks in the baso4 srso4 series display considerable broadening at intermediate compositions the unit cell volume varies from 346 97 a3 in barite 100 baso4 to 308 29 a3 in celestite 100 srso4 this variation in cell parameters is attributed to the degree of substitution of barium by strontium since there is less variation between ionic radii of these elements consequently these substitutions caused variation in morphologies position and d spacing of peaks 200 011 113 312 122 112 and 111 some barite crystals have small scale strontium compositional banding which suggests that the crystals responded to regular fluctuations in physiochemical conditions during deposition the degree of supersaturation in ba2 and sr2 controls the growth mechanism and consequently the surface structure which in turn controls the mechanism of adsorption and incorporation of minor and trace elements into the growing crystal for a solid solution the transitional supersaturation for different growth mechanisms can be significantly different for the two end members one of the most interesting and intriguing phenomena observed in natural crystals of the ba sr so4 solid solution from this study area is the development of compositional oscillatory zoning consisting of alternating ba rich and sr rich layers the sulfur isotope analyses show significant variability for barite and celestite from 16 2 to 23 these values are interpreted as the result of the mixing of two sulfur end members in the mineralizing fluids corresponding to thermochemical sulfate reduction of messinian seawater together with triassic sulfate as sulfur sources fluid inclusion studies of celestite show that the baso4 srso4 solid solution in both deposits was precipitated from hot saline solution th 190 20 c 16 37 wt nacl equivalent in ain allega and 8 2 wt nacl equivalent in el aguiba consequently the precipitation could be from mixing of basinal brines with magmatic meteoric fluid

the mediterranean water body in the late messinian interpreting the record from marginal basins on sicily the stratigraphic record of climatic and palaeoceanographic changes in the mediterranean during the late messinian is controversial on sicily sedimentary facies show a steady transgression suggesting that sub basins were hydrodynamically linked to a larger water body here we test this hypothesis using strontium isotope studies from messinian materials collected from a range of sites in the caltanissetta basin of central sicily the strata include a regionally regressive first cycle of early mid messinian age and a younger transgressive second cycle these cycles are separated by an inter regional unconformity which may be correlated with base level low stand in the mediterranean 87 sr 86 sr ratios for all first cycle gypsum fall within the expected global marine composition 0 70891 0 70897 all second cycle analyses fall within a grouping of significantly lower values 0 70868 0 70878 a surprisingly tight but discrepant grouping for data collected from shells of a brackish water fauna and from gypsum analyses from these different second cycle materials are statistically indistinguishable these results indicate that the strontium isotopic composition of waters from different sub basins on sicily are indistinguishable regardless of salinity during the late messinian therefore these basins must have mixed with a larger homogenized reservoir which we infer was the ancestral mediterranean thus circum mediterranean basins may indeed chart regional palaeoceanographic and climatic events by the end of messinian times the base level of the mediterranean was within the range of the world9s oceans but the water body probably had a distinctly different but internally homogeneous strontium isotopic composition

how dry was the mediterranean during the messinian salinity crisis the messinian salinity crisis msc 5 97 5 33 ma is an enigmatic episode of paleoceanographic change when kilometers thick evaporite units were deposited in the mediterranean basin it is generally accepted that during the msc interval there was a dry climate in the mediterranean region it is difficult to assess how dry the climate was during the msc because a modern analogue in size and duration is absent here we reconstruct hydrological changes in the mediterranean basin during the three main msc stages using excellently preserved biomarkers we used the hydrogen isotopic composition of the long chain n alkanes dn alkanes to reconstruct the hydrological changes on the land adjacent to the mediterranean sea additionally the d of long chain alkenones dalkenones is used to observe changes in the mediterranean sea water source the dn alkanes recorded during the deposition of primary lower gypsum stage 1 in monte tondo indicate a d of the precipitation comparable to the present day mediterranean implying a similar hydrologic regime indicated by experiments modelling the miocene pliocene transition elevated dalkenones values from halite unit stage 2 of the realmonte mine are associated with kainite and giant polygons consistent with presumably high evaporative conditions during halite deposition the dn alkanes recorded during the deposition of upper gypsum stage 3 in eraclea minoa indicate a dprecipitation typical for much drier settings similar to the red sea region the relative contribution of the different alkenones from eraclea minoa is similar to the one observed in present day marine settings suggesting that during stage 3 connections to the open ocean were likely maintained however the dalkenones records during deposition of the evaporites in eraclea minoa are similar to those synchronously registered in the black sea implying that a similar hydrologic regime characterized by extended drought covered large areas of southeastern europe based on the dalkenones similarity and the paratethys type of lago mare fauna in the mediterranean we speculate that the surface water during stage 3 was at times derived from the black sea

s and o so 4 isotopes simultaneous modeling and environmental significance of the nijar messinian gypsum spain abstract the messinian evaporites in nijar basin southeastern spain consist of coarse grained primary selenites and laminated fine grained gypsums these gypsums which are similar to those deposited in other mediterranean messinian basins have rather variable 34 s and 18 o so 4 21 to 24 for 34 s 10 to 17 for 18 o that are generally greater than the normal tertiary marine values 21 22 for 34 s and 13 for 18 o moreover the variation of 18 o so 4 is larger than that of 34 s continental input and reservoir effect did not play important roles for these isotope variations because these factors should have resulted in lower 34 s and 18 o so 4 than the normal marine values redox reactions of sulfur species in brine should have been responsible for the isotope variations to interpret the variable 34 s and 18 o so 4 we quantitatively modeled 34 s and 18 o so 4 of dissolved sulfate during redox reactions in two marine evaporative settings in sediment pores in a shallow water pan and in a free brine column in a deep water basin modeled 34 s and 18 o of dissolved sulfate during reduction of sulfate yield small variations especially for o isotopes in a shallow water pan however modeled 34 s and 18 o of dissolved sulfate during reduction and reoxidation cycling processes in a deep water basin show a progressive increase of up to 10 for both 34 s and 18 o so 4 above their normal marine values importantly the modeled pathways for the deep water basin setting are consistent with the nijar data whereas those for pore waters in shallow water pans are a poor fit to the nijar data the modeled results consistent with trace elements sr isotope data and selenite fabrics suggest that these yesares selenites have formed in deep marine brines the modeling results also demonstrate that 18 o so 4 can have larger variation than 34 s because the incorporation of water oxygen and probably dissolved free oxygen increases 18 o of the reoxidized sulfate whereas reoxidation of sulfide to sulfate decreases the total 34 s so 4 the modeled results could provide important geological implications for isotope and environment interpretations for ancient evaporites for example redox reactions of sulfur species during sulfate precipitation could modify normal marine 34 s and 18 o so 4 more efficiently than freshwater contributions and reservoir effects therefore to establish 34 s and 18 o so 4 age curves redox processes for ancient evaporites should be considered

the organic matter distribution and methane capacity of the lower cretaceous strata of northeastern british columbia canada abstract the methane sorption capacity of a succession of sandstone siltstone shale and coal from the lower cretaceous fort st john group of northeastern british columbia was investigated average organic matter om content for all formations is 2 3 wt with a minimum of 0 6 wt and maximum of 10 1 wt the methane sorption capacity ranges between 0 19 and 2 74 cm3 g at 6 mpa and at 30 c total gas capacity free and sorbed gas ranges between 2 2 and 16 6 cm3 g at 6 mpa micropore volumes range between 0 43 and 1 69 cm3 100 g a positive correlation exists between the om content micropore volume and the methane capacity of shales shales with high methane capacities have either high contents of inertodetrinite or vitrinite moisture content shows a positive relationship with om content micropore volume and methane capacity the negative relationship between moisture and surface area derived from n2 adsorption suggests the moisture is located within the microporosity of the om and also explains the positive relationship between methane capacity and moisture the high inertodetrinite and vitrinite contents correlate with sea level regressions that delivered terrestrial om from coastal plains located south of the study area into the basin

a box model of the late miocene mediterranean sea implications from combined 87sr 86sr and salinity data 1 under certain conditions the strontium isotope ratio in the water of a semi enclosed basin is known to be sensitive to the relative size of ocean water inflow and river input combining sr isotope ratios measured in mediterranean late miocene successions with data on past salinity one can derive quantitative information on the mediterranean hydrological budget at times before and during the messinian salinity crisis msc previous studies obtained this hydrological budget by inverting the salinity and strontium data with steady state solutions to the conservation equations of salt strontium and water here we develop a box model with a time dependent set of equations to investigate the coeval evolution of salinity and sr ratios under different water budgets gateway restrictions and riverine sr characteristics model results are compared with the salinity and strontium ratio data from the mediterranean with a present day water budget strontium ratios in the mediterranean never reach the observed messinian values regardless of gateway restriction and water budget however a model with tripled river input as inferred for the late miocene is able to reproduce the sr ratios observed the onset of the msc can be explained with a simple restriction of the gateway s between the mediterranean and atlantic lower evaporite gypsum formed in a basin with less outflow to the atlantic than modeled in previous studies because of the large late miocene river input evaporite thicknesses predicted by our model and consistent with the messinian sr ratios are on the low end of the thickness range inferred from seismics

paleoenvironmental significance of messinian post evaporitic lacustrine carbonates in the northern apennines italy the post evaporitic messinian in the northern sector of the adriatic foredeep is characterized by the occurrence of abundant terrigenous deposits which have been subdivided into two allostratigraphic units p ev1 p ev2 separated by an erosional unconformity of regional importance the p ev1 consists of basal complex of resedimented evaporites overlain by monotonous succession of mudstone siltstone alternations thin bedded turbidites with an overall coarsening and shallowing upwards trend it is possibly related to the rapid basin infill after the end of the salinity crisis the upper unit p ev2 shows in the most marginal areas a clear cyclical stacking pattern made up of three fining up sequences with fan delta conglomerates at the base of each cycle here a peculiar feature of the p ev2 deposits is the occurrence of three distinct laminated limestone horizons termed colombacci interbedded with fine grained varved mudstones these limestones are abiotic despite the occurrence of abundant ostracod assemblages lago mare fauna in the interbedding pelites and are interpreted as inorganically precipitated deposited in a relatively deep water environment possibly anoxic and related to permanent stratification of water mass events during periods of lake level maxima the combination of petrographical and geochemical observations on carbonate layers reveals that they correspond to events characterized by significant variations of environmental conditions however 18o 5 30 0 2 and 13c 9 28 1 68 signatures suggest that the precipitation of low mg calcite often occurred in a non marine environment and that meteoric water input had a considerable influence on late messinian sedimentation moreover the limestones have a uniform 87sr 86sr composition 0 70864 0 70875 in the range of other lago mare sediments from elsewhere in the mediterranean suggesting that some of the major mediterranean basins were likely interconnected during the lago mare phase a strongly reduced rate of hydrological exchange with the ocean is also possible but the possibility of marine influence during this stage is not completely excluded

an overview of canadian shale gas production and environmental concerns abstract production of hydrocarbons from canadian shales started slowly in 2005 and has significantly increased since natural gas is mainly being produced from devonian shales in the horn river basin and from the triassic montney shales and siltstones both located in northeastern british columbia and to a lesser extent in the devonian duvernay formation in alberta western canada other shales with natural gas potential are currently being evaluated including the upper ordovician utica shale in southern quebec and the mississippian frederick brook shale in new brunswick eastern canada this paper describes the status of shale gas exploration and production in canada including discussions on geological contexts of the main shale formations containing natural gas water use for hydraulic fracturing the types of hydraulic fracturing public concerns and on going research efforts as the environmental debate concerning the shale gas industry is rather intense in quebec the utica shale context is presented in more detail

the effect of moisture on the methane adsorption capacity of shales a study case in the eastern qaidam basin in china this study investigated the effects of moisture on high pressure methane adsorption in carboniferous shales from the qaidam basin china the shale characteristics including the organic inorganic compositions and pore structure volume and surface distribution were obtained using various techniques gibbs adsorption measurements were performed over a pressure range up to 6 mpa and temperatures of 308 15 k on dry samples and moisture equilibrated samples to analyze the correlations between organic inorganic matter pore structure and moisture content on the methane sorption capacity compared to dry samples the sorption capacity of wet samples 0 44 2 52 of water content is reduced from 19 7 5 3 to 36 1 6 1 langmuir fitting is conducted to investigate moisture dependent variations of adsorbed methane density langmuir pressure and volume by combining the pore volume and surface distribution analyses our observations suggested that the main competition sites for ch4 h2o covered pores of approximately 2 7 nm whereas the effective sites for methane and water were predominantly distributed within smaller 10 nm respectively regarding the compositional correlations the impact of moisture on the amount of adsorbed methane shows a roughly linearly decreasing trend with increasing toc content ranging from 0 62 to 2 88 whereas the correlation between the moisture effect and various inorganic components is more complicated further fitting results indicate that illite smectite mixed formations are closely related to the methane capacity whereas the illite content show an evident connection to the pore structural volume and surface variations in the presence of moisture

pore types in the barnett and woodford gas shales contribution to understanding gas storage and migration pathways in fine grained rocks the identification of organoporosity microscale and nanoscale pores within organic matter in shales its importance to storage and perhaps transfer of gas molecules through shales and methods for gathering three dimensional images of the pores such as by argon ion milling and or field emission scanning electron microscopy have all been well documented and discussed for unconventional gas shales however other types of pores exist within shales that can be important to storage and migration of gas and oil and other technologies are available for their identification and imaging the different pore types found in the barnett and woodford shales are described and classified in this article scanning electron microscopy revealed the presence of porous floccules in both the barnett and woodford shales which appear similar to laboratory produced floccules and to those in other ancient shales published experimental and observational studies indicate that floccules are hydraulically equivalent to coarser grains and are transported by traction processes current induced microsedimentary structures and textures within the barnett and woodford shales as well as the preserved floccules suggest such processes were active during transport and deposition pore spaces between the floccules are open and can provide storage space as well as permeability pathways for gas molecules through the shales pores are also found within organic matter that occurs both as discrete particles and as adsorbed coatings around clay grains in the shale they are referred to here as organopores porous fecal pellets are also common in the barnett shale preserved fossil fragments such as organic walled spores and inorganic sponge spicules have hollow central chambers which may remain partially or completely open even after burial intraparticle pores occur between grains of various minerals e g pyrite framboids microchannels within shale matrix which may be the bounding surfaces of scours or microsedimentary structures may also provide permeability pathways for hydrocarbon migration mircrofractures are also common and their initiation might be related to mineral crystal structure when present in sufficient quantity these pore types offer potential gas and oil molecule storage spaces and permeability pathways through the shales

estuarine lago mare fauna from the tertiary piedmont basin indicates episodic atlantic mediterranean exchange during the final stage of the mediterranean salinity crisis abstract the geochemical signature of fossils from lago mare deposits at moncucco torinese nw italy indicates a temporary marine ingression into the tertiary piedmont basin just before the miocene pliocene boundary isotope 18o 13c 87sr 86sr and trace element sr ca ba ca data from mollusk shells of multiple species and croaker otoliths indicate an upper estuarine environment with considerable seasonal variability in evaporation and freshwater input reconstructed salinities the presence of a paralic paleobiotope with thalassogenic water in the tertiary piedmont basin contradicts ideas of the mediterranean as a brackish lake fed by the paratethys during the latest stage of the mediterranean salinity crisis instead our data support previous notions of temporary atlantic mediterranean exchange during sea level highstands preceding the permanent re connection at the miocene pliocene transition the establishment of short lived and disjunct estuarine and lagoonal environments such as in the tertiary piedmont basin during marine ingressions also puts highly variable 87sr 86sr values and occurrences of shallow water benthic foraminifera in lago mare deposits of other mediterranean basins into a new perspective

sea level events in the south pacific linked with the messinian salinity crisis cores drilled through the carbonate cap of niue a mid oceanic carbonate platform in the south pacific contain an unusually well resolved stratigraphic section of the latest miocene at 35 to 140 m depth below sea level intensely leached and chalky intervals associated with pronounced 18 o and 13 c depletions mark the position of dissolution unconformities representing eight episodes of eustatic falls that outstripped the local rate of subsidence we demonstrate on the basis of sr isotope chronostratigraphy that these eustatic changes are correlative with the messinian salinity crisis events in the mediterranean sea level changes of about 10 m amplitude commenced at 6 14 ma and culminated in a large sea level fall that reached at least 30 m at 5 26 ma corresponding to the miocene pliocene boundary evaluation of the sea level history reported here and the contemporaneous mediterranean events supports the model of coupling between tectonic and eustatic factors that caused the onset and demise of the salinity crisis the available evidence suggests that during messinian time glacio eustatic falls and rises are likely to have modulated the connection between the atlantic and the mediterranean and influenced the evaporite deposition and may have contributed significantly to the final phase of isolation and desiccation of the mediterranean and its subsequent refilling during the zan clean deluge

incompatible stress regimes from geological and geomechanical datasets can they be reconciled an example from the carnarvon basin western australia abstract knowledge of the in situ stress field is essential in petroleum basins as it exerts a prime control over seal integrity fracture stimulation wellbore stability and fluid flow previous geomechanical analysis of australia s carnarvon basin the continent s premier hydrocarbon region highlights a normal to strike slip fault stress regime however neotectonic evidence and contemporary seismicity suggest the possibility of a strike slip to reverse fault stress regime we attempt to reconcile these conflicting datasets through new analysis of the in situ stresses principal stress magnitudes and orientations were defined with data from 76 previously unanalysed petroleum wells wellbore image logs yield a maximum horizontal stress orientation of 113 n consistent with modelling of the stress field throughout the indo australian plate vertical stress magnitudes are estimated to range from 20 mpa km 1 to 22 4 mpa km 1 leak off tests lot from 42 wells are analysed using two methodologies one assuming tensile failure as traditionally accepted the other assuming shear failure as outlined by couzens schultz and chan 2010 and result in two different sets of horizontal stress magnitude estimates traditional interpretation of lots results in a minimum horizontal stress gradient of 16 8 mpa km 1 and a maximum horizontal stress gradient of 21 8 mpa km 1 the new method for lot interpretation results in a minimum horizontal stress gradient of 18 1 mpa km 1 and a maximum horizontal stress gradient of 25 4 mpa km 1 inclined natural fractures observed at lot depths supports application of the new method of lot interpretation traditional interpretation of stress magnitudes implies a normal to strike slip fault stress regime while the new method implies a strike slip fault stress regime this latter interpretation is favoured by the authors as it allows for a reconciliation of the geological and geomechanical datasets the assessment undertaken herein allows for reinterpretation of stress magnitudes in seismically active basins hosting differing geomechanical and neotectonic regimes potentially altering existing understanding of seal integrity fracture stimulation wellbore stability and fluid flow

coupled measurements of δ18o and δd of hydration water and salinity of fluid inclusions in gypsum from the messinian yesares member sorbas basin se spain we studied one cycle cycle 6 of gypsum marl deposition from the messinian yesares member in sorbas basin spain the objective was to reconstruct the changing environment of deposition and its relation to astronomically forced climate change the 18o and d of gypsum hydration water caso4 2h2o and salinity of fluid inclusions were measured in the same samples to test if they record the composition of the mother fluid from which gypsum was precipitated water isotopes are highly correlated with fluid inclusion salinity suggesting the hydration water has not exchanged after formation the relatively low water isotope values and fluid inclusion salinities indicate a significant influence of meteoric water whereas 34s 18oso4 and 87sr 86sr support a dominant marine origin for the gypsum deposits the discrepancy between water and elemental isotope signatures can be reconciled if meteoric water dissolved previously deposited marine sulfates supplying calcium and sulfate ions to the basin which maintained gypsum saturation this recycling process accounts for the marine 34s 18oso4 and 87sr 86sr signatures whereas the low 18o and d values of gypsum hydration water and fluid inclusion salinities reflect the influence of freshwater the cyclic deposition of gypsum and marl in the yesares member has previously been interpreted to reflect changing climate related to earth s precession cycle we demonstrate that the 18o d and salinity of the parent brine increased from low values at the base of the cycle to a maximum in the massive gypsum palisade and decreased again to lower values in the supercones at the top of the cycle this pattern together with changes in mineralogy calcite dolomite gypsum is consistent with a precession driven change in climate with wettest conditions summer insolation maxima associated with the base of the calcium carbonate marls and driest conditions summer insolation minima during formation of the gypsum palisade

deep water clastic evaporites deposition in the messinian adriatic foredeep northern apennines italy did the mediterranean ever dry out a new genetic facies model for deep water clastic evaporites is presented based on work carried out on the messinian gessoso solfifera formation of the northern apennines during the last 15 years this model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts the model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites representing the most common evaporite facies of the northern apennines and the definition of the genetic and stratigraphic relationship with primary shallow water evaporites formed and preserved in marginal settings due to the severe recrystallization processes usually affecting these deposits petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity driven deposits ranging from debrisflow to low density turbidites almost all the laminar balatino gypsum previously considered a deep water primary deposit is here reinterpreted as the fine grained product of high to low density gravity flows facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the apennine foredeep basin the messinian salinity crisis occurred during an intense phase of geodynamic reorganization of the mediterranean area that also produced the fragmentation of the former miocene apennine foredeep basin in this area primary shallow water evaporites equivalent to the mediterranean lower evaporites apparently only formed in semi closed thrust top basins like the vena del gesso basin the subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the messinian tectonic evolution of the apennine thrust belt and related exhumation erosional processes the facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts the importance of clastic evaporites deposits has been overlooked in the study of other mediterranean areas based on the apennine basins experience it is suggested here that evaporites diffused into the deeper portions of the mediterranean basin may consist mainly of deep water resedimented deposits rather than shallow water to supratidal primary evaporites indicative of a complete basin desiccation