δ18o values of coexisting brachiopods and fish temperature differences and estimates of paleo water depths to estimate vertical thermal gradients and paleo water depths to marine platforms we present a new method based on the difference between 18 o values of contemporaneous brachiopod carbonate and fish phosphate present day marine fauna of well known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures we predict distributions of isotopic data that result from sampling strategy basin morphology and fauna ecology and discuss limitations application of the method to the jurassic paris london basin gives vertical thermal variations of up to 14 c associated with depths varying from a few meters to 170 30 m the estimated depths are minimum values and are greater than those estimated from sedimentological criteria for this ancient epicontinental sea

lithospheric and upper mantle structure of southern tibet from a seismological passive source experiment fifteen seismic stations were operated with about 20 km spacing in southern tibet across the zangbo suture the collision zone between india and asia between may and october 1994 as part of the international deep profiling of tibet and the himalaya project indepth ii for wide angle recording of the controlled source experiment and for passive earthquake recording in addition a dense deployment 4 km spacing of stations within the german depth profiling of tibet and the himalayas gedepth project also recorded a number of teleseismic earthquakes the third data source used in this study is the records of the permanent broadband station at lhasa teleseismic records have been obtained in sufficient quantity and quality to derive an image of the structure of the lithosphere and upper mantle from p to s converted phases important results are as follows the moho at 70 80 km and a second discontinuity at 50 60 km depth are observed over the entire profile south and north of the zangbo suture the data from the gedepth dense array enable the detection of inclined structures penetrating the crust at the zangbo suture a pronounced low velocity zone exists north of the zangbo suture at about 10 20 km depth the locations of the upper mantle discontinuities at 410 and 660 km depth are in agreement with the global reference model iasp91 kennett 1991 over a large region of the himalaya and southern tibet

the distribution of the mid to lower crustal low velocity zone beneath the northeastern tibetan plateau revealed from ambient noise tomography we collected continuous seismic data recorded between 2007 and 2010 by 208 broadband stations from the chinese provincial digital seismic networks a seismic collaborative experiment of northern tibet and the northeastern tibet seismic experiment cross correlations of vertical component records are computed to extract the rayleigh wave empirical green s functions group and phase velocities are then constructed from the empirical green s functions in 8 to 50 s period at periods 25 s more than 10 lower velocities are imaged beneath the qaidam basin and high velocities are observed beneath the nonbasin regions at periods 30 s up to 10 lower velocities are imaged in the qiangtang and songpan ganze terranes from these group and phase velocity maps a three dimensional 3 d vsv model of the crust is derived the model shows that the qiangtang and songpan ganze terranes have a very thick crust with a prominent low velocity zone lvz in the middle crust the lvz thins out in the vicinity of the eastern kunlun mountains providing a new constraint on the mode of deformation across the tibetan plateau the northwestern qilian orogen where receiver functions reveal a moho deeper than the surrounding areas also features a relatively weak midcrustal lvz which we interpret as an intracrustal response associated with the shortening between the north china craton and the tibetan plateau

glacial recharge and paleohydrologic flow systems in the illinois basin evidence from chemistry of ordovician carbonate galena formation waters the illinois basin provides an opportune setting for elucidating the roles of remnant evaporite brines and meteoric waters in the evolution of formation waters in an intracratonic sedimentary basin formation waters from carbonate reservoirs in the upper ordovician galena group have been analyzed geochemically to study the origin of their salinity their chemical and isotopic evolution and their relationship to paleohydrologic flow systems chloride bromide ratios and ci br na br relations indicate that initial brine salinity resulted from subaerial evaporation of seawater rather than from halite dissolution subsequent subsurface dilution of the brines by meteoric waters is disclosed by d 18 o covariance however the remnant evaporite brine has not been completely expelled from these ordovician strata galena formation waters have 87 sr 86 sr ratios that range from 0 708 17 a value nearly equal to that of coeval seawater to 0 710 43 this is the greatest range of sr isotopic ratios found in waters from any stratigraphic unit in the basin two fluid mixing events are revealed in plots of 87 sr 86 sr vs 1 sr introduction of 87 sr enriched fluids from a siliciclastic source probably overlying maquoketa shale and a later event that only affected reservoir waters in the western shelf of the basin general covariance between sr and h o isotopes suggests that the later event is related to meteoric water recharge the point of intersection of the d 18 o trend with the meteoric water line implies that this mixing event involved pleistocene glacial meltwater that recharged galena reservoirs near outcrops along the western margin of the basin ordovician galena formation waters are geochemically distinct from those in both silurian devonian and mississippian pennsylvanian strata a distinction that has evidently been maintained by the overlying maquoketa regional aquitard

temperature limits for preservation of primary calcite clumped isotope paleotemperatures abstract solid state reordering of c o bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations metrics commonly used to gauge preservation quality to correctly interpret the paleoenvironmental significance of clumped isotope derived paleotemperatures it is necessary to understand the temperature time domain in which solid state c o bond reordering is important we address this question using a combination of laboratory and natural geological experiments on paleozoic brachiopod shells the laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13 c 18 o bond reordering the resulting arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions we develop an alternative kinetic model for reordering that accounts for non first order reaction progress observed during the initial several hundred minutes of laboratory heating experiments and show that the simplified first order approximation model passey and henkes 2012 predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins we evaluate our laboratory based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories specifically we use the laboratory derived arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million year time steps reflecting the burial and exhumation temperature paths of each basin while this exercise is limited by the relatively large uncertainties in the temperature histories of these basins we find general correspondence within error between predicted and observed clumped isotope values we present simplified temperature time diagrams for calcite showing domains where primary clumped isotope compositions will be preserved partially reordered and fully reordered in conclusion calcite samples dwelling at 100 c or lower for 10 6 10 8 year timescales should not be affected by solid state c o bond reordering

chemical multi isotopic li b sr u h o and thermal characterization of triassic formation waters from the paris basin this work reports chemical and isotope data and temperature estimates for seven water samples collected from triassic formations in the paris basin in france four samples were collected in the central part of the basin saline waters and three were collected at the edge of the basin near the recharge zone dilute waters the saline waters collected from the chaunoy and champotran boreholes have high salinities around 120 g l and very similar chemical and isotopic compositions the saline water sample from the la torche borehole has much higher salinity 168 g l and significantly different isotope characteristics the chemical geothermometers applied to these fluids from the centre of the basin give temperature values ranging between 80 and 100 c the fresh water samples collected at the edge of the basin have very different chemical and isotopic compositions these dilute water samples santenay and ch teauroux are shallow with colder temperatures of around 45 to 50 c the study of uranium activity ratios for these triassic formation waters allows us as a first approximation to estimate a mean apparent fluid circulation velocity of around 0 2 m yr which corresponds to a mean age slightly higher than 1 my for waters sampled in the chaunoy champotran and la torche fields in the centre of the basin the multi isotope characterization of triassic formation waters shows that our data are in agreement with literature values as concerns traditional isotope systematics delta18o deltad 87sr 86sr li and b isotope signatures in the centre of the paris basin are in a good agreement with a fluid signature derived mainly from water rock interactions involving clastic rocks with water essentially resulting from a seawater derived brine endmember diluted by meteoric waters the data reported in the present work for li and b isotopes could be used as a reference for future studies to characterize sandstone formation waters

geodynamic control on carbonate diagenesis petrographic and isotopic investigation of the upper jurassic formations of the paris basin france abstract the oxfordian and kimmeridgian carbonates of the eastern edge of the paris basin display poor reservoir properties stable isotope investigation of these non recrystallized cements through both microdrilling sampling and in situ sims secondary ion mass spectrometry analysis shows that they originated from slightly buffered meteoric fluids 3 smow to 8 smow flowing through the malm carbonate aquifers of the eastern edge of the paris basin after a review of the post upper jurassic history of the paris basin it appears that meteoric water supplies leading to such cementations were associated with the evolution of the basin s geodynamic setting and notably with the lcu late cimmerian unconformity major event which corresponds to the uplift of the london brabant massif denudation of the oxfordian and kimmeridgian carbonates on the southern flank of the london brabant massif to the north of the study area then lead to lateral recharging of the associated aquifers with meteoric fluids this scenario is similar to the one proposed to explain cementations of the jurassic carbonates in the wessex weald basins which emphasizes the main role played by the cretaceous unconformities over carbonate diagenesis at the scale of the northwestern tethys margin

tectonics and topography for a lithosphere containing density heterogeneities the purpose of this paper is to clarify the dynamic role of lithospheric density heterogeneities in particular with respect to mountain building and other processes of intraplate deformation density anomalies within or just beneath the lithosphere constitute major sources for tectonic stress fields the product of their magnitude by their depth is shown to characterize their ability to induce deformation this rule of the density moment directly yields the lithospheric thickening or thinning rate when applied to structures of large lateral extent for anomalies of lateral extent that is small in comparison with their depth the deformation is vertically inhomogeneous and has been computed with the help of simple physical models of a stratified viscous newtonian lithosphere the analytical treatment is based on fourier transform continent continent collision thickens not only the crust but the entire lithosphere the cold root underlying a mountain chain induces strong regional compressive stresses able to sustain the mountain bulding process without further help from forces transmitted from far away thus the continental lithosphere is in a somewhat metastable mechanical state adiabatic i e rapid thickening or thinning tends to grow further once initiated tectonic phases of strong compression correspond to the climax of such instabilities the response of models with cold lithospheric roots of various intensities has been computed both in two and three dimensions they yield velocity distributions and stress fields instructive comparisons are made with earthquake focal mechanisms and in situ stress measurements in the alpine and appalachian regions in the presence of lateral variations of the mechanical properties of the lithosphere the tectonic style is not only function of the local topography and of the nature of its compensation deformations in neighbouring provinces are coupled as shown by 3 dimensional models for example thickening sustained by a cold lithospheric root may generate extension in peripheral zones of weakness these last results illustrate the point that the computation of regional tectonic stresses requires the knowledge of the density anomalies within the lithosphere on the one hand and of geometrical constraints related to lateral mechanical heterogeneities on the other

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

time capsule concretions unlocking burial diagenetic processes in the mancos shale using carbonate clumped isotopes abstract septarian carbonate concretions contain carbonate precipitated during progressive growth of the concretion and subsequent fracture filling as such they have been used to track variations in 13c and 18o of pore waters during diagenesis and to define diagenetic zones in clastic rocks however the 18o value of the carbonate is dependent on precipitation temperature and the 18o value of the pore fluid from which it precipitated interpretations must assume one of these parameters both of which are highly variable through time in diagenetic settings carbonate clumped isotopes of the cement can provide independent estimates of temperature of precipitation allowing the pore water 18o to be back calculated here we use this technique on carbonate concretions and fracture fills of the upper cretaceous prairie canyon member mancos shale colorado we sampled concretions from two permeable horizons separated by a 5 m shale layer with one permeable horizon containing concretions with septarian fractures we show cores precipitated at cooler temperatures 31 c 660 m burial depth than the rims 68 c 1980 m burial depth and relate that to the 13ccarbonate values to suggest the concretion core precipitated in the methanogenic zone with increasing input from thermogenically produced co2 the two concretion bearing horizons have different back calculated 18oporewater values mean 2 65 and 1 13 vsmow for cements formed at the same temperature and similar 13c values suggesting the shale layer present between the two horizons acted as a barrier to fluid mixing additionally the 18ocarbonate of the septarian fractures 13 8 vpbd are due to precipitation at high temperatures 102 to 115 c from a fluid with a mean 18oporewater of 0 32 vsmow therefore we can tie in the cementation history of the formation to temporal and spatial variations in 18oporewater

the origin and timing of multiphase cementation in carbonates impact of regional scale geodynamic events on the middle jurassic limestones diagenesis paris basin france the middle jurassic carbonates of the eastern part of the paris basin display surprisingly low values of porosity and permeability 15 and k 0 5 md the main objective of this study is to determine the causes and timing of the cementation that altered the petrophysical properties of these carbonates thereby destroying their potential as oil reservoirs a fate that did not befall their equivalents in deeper central parts of the paris basin using petrographic and geochemical analyses stable o and c isotopes sr isotopes major elements we identify six calcitic spar stages two dolomite stages and several episodes of fracturing and stylolitization ordered in paragenetic sequence cement quantification shows the predominance of two blocky calcite cement stages 75 of total cementation o and sr isotopes from these calcite cements suggest that the parent fluids resulted either from a mixing of trapped jurassic seawater and meteoric water or from buffered meteoric waters in the geological history of the paris basin major meteoric water inputs were possible during the early cretaceous when the middle jurassic carbonates cropped out at its northern and eastern borders lateral meteoric recharge may have occurred as a result of two separate uplift events late cimmerian unconformity and late aptian unconformity and the related exposures of carbonates to the north of the study area this palaeohydrological circulation brought about a significant reduction of porosity from 40 to 10 through calcite cement precipitation the early cretaceous events are of great importance in the diagenetic evolution of the sedimentary basins bordering the london brabant massif across all of northwestern europe a subsequent dolomite and calcite cementation stage accounts for about 5 of the total cement volumes this late cementation may have been caused by hydrothermal fluids ascending along permeable fractures during the late oligocene extension episode

oxygen isotope analysis of the eyes of pelagic trilobites testing the application of sea temperature proxies for the ordovician the oxygen isotope composition of well preserved trilobite eye calcite retaining its original optical properties represents a possible source of information on paleozoic sea temperatures species of the epipelagic telephinid genera carolinites and opipeuterella from strata of early to middle ordovician age in spitsbergen and australia were analyzed and compared with benthic asaphid species scanning electron microscope sem cathodoluminescence cl electron microprobe and electron backscatter diffraction ebsd techniques were used to assess eye preservation prior to isotope analysis some apparently well preserved eyes are identified from the valhallfonna spitsbergen and emanuel australia formations the eyes show a wide variation in 18o values 6 2 to 9 8 for the valhallfonna formation 3 2 to 10 4 for the emanuel formation and 3 6 to 7 4 for the horn valley siltstone australia intra eye secondary ion mass spectrometry sims isotope results reveal an even larger range in 18o in some specimens 18o of 2 4 to 10 4 suggesting that the trilobite eyes have undergone cryptic recrystallization a sub set of trilobite cuticle from the three formations were analyzed for their carbonate clumped isotope compositions 47 and yielded crystallization temperatures above 50 c consistent with diagenetic alteration the sims and 47 results suggest that classic preservation assessment protocols for the stable isotope study of deep time carbonate samples may be insufficient especially for these techniques there is a need for extensive microstructural characterization of lower paleozoic biogenic carbonates by techniques including ebsd sims and 47 before their stable isotope signatures can be used with certainty in paleoclimate studies

geodynamics of the tarim basin and the tian shan in central asia the india asia collision has caused crustal thickening in tibet by at least a factor of 2 in the last 20 30 myr of this collision the tian shan mountain range has also been reactivated the tarim basin however shows little internal deformation we describe a series of numerical experiments which constrain the effective lithospheric strength parameters of the tarim basin and the tian shan in the context of a thin viscous sheet model we use a finite element representation of the thin viscous sheet model to approximate the deformation field in the india asia collision and compare model crustal thickness distributions with that inferred from a local isostatic model of topography the experiments show that a strong tarim basin while undergoing little internal deformation transfers strain to the tian shan producing significant crustal thickening in the tian shan region based only on diagnostic parameters such as the maximum thickening in the tian shan and the minimum in the tarim basin the principal features of the topography can be approximately reproduced using models in which either the tarim basin is strong or the tian shan is weak or both for a rheological model in which the stress versus strain rate exponent is n 3 the strength coefficient for the strong tarim basin model vtarim is between about 1 7 and 2 for the weak tian shan model the relative strength coefficient vtian is between about 0 65 and 0 75 if both strong tarim and weak tian shan are included there is a trade off between the required values of vtarim and vtian and the shape of the predicted crustal thickness profiles better matches the observed profiles the steep topographic slope on the southern margin of the tarim basin requires that it is anomalously strong while the rapid decrease of topographic height to the north of the tian shan requires that it is anomalously weak similar conclusions are obtained with a rheological model based on n 10 simplified rheological models of the lithosphere show that the variations in lithospheric strength may be explained by changes to the moho temperature of the order of 10 to 30 c

laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25 250 c temperature range abstract many fields of earth sciences benefit from the knowledge of mineral formation temperatures for example carbonates are extensively used for reconstruction of the earth s past climatic variations by determining ocean lake and soil paleotemperatures furthermore diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications for instance for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution it is based on the temperature dependent abundance of the rare 13c 18o bonds in carbonate minerals specified as a 47 value the clumped isotope thermometer has been calibrated experimentally from 1 c to 70 c however higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory in order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high temperature geological processes we precipitated caco3 mainly calcite in the laboratory between 23 and 250 c we used two different precipitation techniques first minerals were precipitated from a caco3 supersaturated solution at atmospheric pressure 23 91 c and second from a solution resulting from the mixing of cacl2 and nahco3 in a pressurized reaction vessel at a pressure of up to 80 bar 25 250 c the calibration lines of both experimental approaches overlap and agree in the slopes with theoretical estimates and with other calibration experiments in which carbonates were reacted with phosphoric acid at temperatures above 70 c our study suggests a universal 47 t calibration t in k 47 in 47 0 98 0 01 3 407 10 9 t 4 2 365 10 7 t 3 2 607 10 3 t 2 5 880 t 0 293 0 004 this new 47 t calibration given in the absolute reference frame that extends the experimentally calibrated temperature range for clumped isotopes to 250 c can be applied to carbonates that grew at intermediate temperatures 20 250 c

subsidence of the paris basin we discuss the main results of a systematic quantitative analysis of the subsidence of the paris basin made on 100 wells backstripping techniques with decompaction as well as sea level and water depth corrections are used to derive tectonic subsidence curves in the absence of water and sediment loading assuming local as well as regional compensation a best fitting sea level variations curve is derived for the deepest central part on the basis of the resulting tectonic subsidence curve the adopted amplitude of the regression since upper cretaceous is 330 m the spatial and temporal distribution of tectonic subsidence is reconstructed and discussed it is shown that rigidity of the lithosphere with an adopted 50 km flexural parameter plays a significant role these results are then quantitatively interpreted in terms of the lithospheric stretching model this interpretation is reasonable provided it is made in terms of volumetric subsidence over the whole basin because of the thermal conduction and the rigidity low pass filtering effects the subsidence can be explained if the axial zone was thinned during permo triassic by a factor of about 1 3 with respect to the adjacent lithosphere it is shown that either the initial altitude was more than 500 m above sea level or the lower part of the lithosphere was lost at the beginning of the permo triassic phase of extension resulting in a rapid uplift of several hundreds of meters the similarity of the permo triassic initiating extensional phase with active continental rifting is shown

noble gases in crude oils from the paris basin france implications for the origin of fluids and constraints on oil water gas interactions in order to investigate the potential of noble gases to trace the dynamics of oil reservoirs we have analysed the abundance and isotopic composition of all noble gases he ne ar kr and xe in crude oils from the paris basin france using a new extraction and purification procedure the main oil reservoirs are presently located in the jurassic dogger limestone and in the triassic keuper sandstone but hydrocarbons originated from a common source rock formation located in the interbedded liassic sequence despite this common origin the abundance and isotopic ratios of the noble gases differ between the dogger and the keuper the isotopic compositions of kr and xe are indistinguishable from that of air 3he 4he ratios higher than those predicted from radiogenic production in the sediments or in the crust are attributed to the occurrence of mantle derived 3he in the basin each sedimentary sequence is characterised by well defined and homogeneous 21ne 22ne and 40ar 36ar ratios which average 0 0306 0 0008 and 312 10 for the dogger and 0 0367 0 0012 and 664 30 for the keuper respectively the main source of radiogenic noble gases appears to be the continental crust underlying the basin with possible regional contributions of noble gas isotopes produced in the sediments the helium and argon isotopic ratios of the dogger oils are very similar to those observed in geothermal waters flowing in the dogger aquifer throughout the basin demonstrating that noble gases in oils derive from associated groundwaters oil reservoirs in the paris basin therefore accumulate noble gases from wide regions of the continental crust through cross formational flow of groundwaters and subsequent partitioning into oil this observation implies that noble gases cannot be directly used to date oils but can provide time constraints if 1 water oil interactions are quantified and 2 the residence time as well as the noble gas characteristics of associated groundwaters are known oil water gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance two distinct processes have been identified 1 accumulation of atmosphere derived ang and radiogenic noble gases both initially dissolved in groundwaters resulting in a positive correlation between absolute amount of ang and the extent of heavy noble gas fractionation and 2 subsequent fractional degassing resulting in a negative correlation between ang abundance and heavy noble gas fractionation degassing is particularly evident for the keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping the ang abundance in the dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil given current estimates of the residence time for groundwaters in the dogger aquifer the duration of oil water interaction is in qualitative agreement with a palaeocene oligocene age for the major episode of secondary oil migration in the paris basin high xenon contents in keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time and that the trias might have reached hydrostatic condition only recently

seismic tomographic imaging of the crust and upper mantle under the central and western tien shan orogenic belt 1 detailed 3 d tomographic images of p and s wave velocity vp vs and poisson s ratio under the central and western tien shan orogenic belt are determined by using a large number of high quality p and s wave arrival times from local earthquakes the results show that under the tien shan orogenic belt high vp high vs and low anomalies are revealed in the upper and middle crust possibly indicating the existence of the paleozoic crystalline basement rocks while low vp low vs and high anomalies appear in the lower crust and upper mantle perhaps suggesting that the hot and wet material is upwelling under the tien shan orogenic belt from the mantle some high vp high vs and low anomalies are tilted toward the tien shan along with the seismicity these are found in the collision zones between the tien shan and the tarim basin in the south and the kazakh shield in the north and suggest the underthrusting of the tarim and kazakh lithosphere beneath the tien shan meanwhile some low vp low vs and high anomalies are imaged in other parts of these collision zones perhaps indicating the intrusion of the hot and wet material into the crust from the upper mantle these results indicate that both the upwelling of the hot and wet material and the underthrusting of the tarim and kazakh lithosphere may have played an important role in the mountain building under the tarim and fergana basins low vp low vs and high anomalies are revealed in the upper crust while high vp high vs and low anomalies are visible in the lower crust and upper mantle these may reflect the existence of less compacted sedimentary material in the shallow crust and more highly compacted craton like structures in the deeper crust and upper mantle under the basins the talas fergana fault shows an obvious tectonic boundary between central and western tien shan the central tien shan displays high vp high vs and low anomalies in the upper and middle crust while western tien shan exhibits low vp low vs and high anomalies however the pattern of seismic structure between central and western tien shan reverses in the lower crust such a correlation may extend down to the upper mantle suggesting that the talas fergana fault may be a lithospheric scale boundary additionally a columnar low vp and low vs anomaly is clearly observed around the turning point of the talas fergana fault from the nwn to nww trending orientations and may indicate that the fault provides a channel for the hot and wet material upwelling from the mantle to the surface

tectonic history of the kyrgyz south tien shan atbashi inylchek suture zone the role of inherited structures during deformation propagation 1 multimethod chronology was applied on intrusives bordering the kyrgyz south tien shan suture stss to decipher the timing of 1 formation and amalgamation of the suturing units and 2 intracontinental deformation that built the bordering mountain ranges zircon u pb data indicate similarities between the tien shan and tarim precambrian crust caledonian 440 410 ma and hercynian 310 280 ma zircon u pb ages were found at the edge of the stss related to subduction and closure of the turkestan ocean and the formation of the suture itself permian triassic 280 210 ma titanite fission track and zircon u th he data record the first signs of exhumation when the stss evolved into a shear zone and the adjacent tarim basin started to subside low temperature thermochronological apatite fission track zircon and apatite u th he analyses reveal three distinct cooling phases becoming younger toward the stss center 1 jurassic cretaceous cooling ages provide evidence that a mesozoic south tien shan orogen formed as a response to the cimmerian orogeny 2 early paleogene 60 45 ma data indicate a renewed pulse of stss reactivation during the early cenozoic 3 neogene ages constrain the onset of the modern tien shan mountain building to the late oligocene 30 25 ma which intensified during the miocene 10 8 ma and pliocene 3 2 ma the cenozoic signals may reflect renewed responses to collisions at the southern eurasian border i e the kohistan dras and india eurasia collisions this progressive rejuvenation of the stss demonstrates that deformation has not migrated steadily into the forelands but was focused on pre existing basement structures

evolution of porewater composition through time in limestone aquifers salinity and d h of fluid inclusion water in authigenic minerals jurassic of the eastern paris basin france past water circulations can significantly reduce the porosity and permeability of marine limestones this is particularly the case in the middle bathonian bajocian to upper oxfordian jurassic limestones from the eastern border of the paris basin the knowledge of the timing the temperature and composition of paleowaters is essential to model the hydrological evolution in this area where the callovian oxfordian claystones are studied for the storage of nuclear wastes in this way fluid inclusions hosted in low temperature 60 c authigenic calcite quartz and celestite crystals were analyzed by raman spectroscopy and mass spectrometry to determine the chlorinity and d h ratios chlorinity measurements mmol cl per liter of water in fluid inclusions trapped in authigenic crystals during the late jurassic early cretaceous period revealed unexpected high values up to 3800 mmol l 1 indicating that brines were involved in some of the diagenetic crystallization processes by contrast fluid inclusions in calcite cements of cenozoic age within the oxfordian limestones have low cl concentration less than 150 mmol l 1 thus showing that a dilution event caused by water infiltrations during the cretaceous uplift of this part of the basin has flushed out the original saline porewater by coupling d of fluid inclusion with 18o of calcite crystals we estimate that calcite precipitation occurred at temperatures between 25 and 53 c the hydrogen isotope composition of calcite forming water is different between the middle jurassic d ranging from 20 to 35 8 v smow and the overlying oxfordian limestone d from 59 5 to 44 8 v smow present day groundwaters are also of distinct composition on both sides of the oxfordian claystones indicating that limestone aquifers underwent independent hydrologic evolutions since the early diagenetic jurassic cementation

early dolomitization and partial burial recrystallization a case study of middle triassic peritidal dolomites in the villany hills sw hungary using petrography carbon oxygen strontium and clumped isotope data

evidence for an early cretaceous mineralizing event above the basement sediment unconformity in the intracratonic paris basin paragenetic sequence and sm nd dating of the world class pierre perthuis stratabound fluorite deposit world class stratabound fluorite deposits are spatially associated with the basement sediment unconformity of the intracratonic paris basin and the morvan massif in burgundy france the reserves are estimated to be about 5 5 mt of fluorite within six fluorite deposits in this study we aim to determine the age of the major fluorite mineralization event of the pierre perthuis deposit 1 4 mt fluorite by a combined study of the paragenetic mineral sequence and sm nd dating on fluorite crystals fluorite occurs as isolated cubes or filling geodes in a triassic silicified dolomitic formation three fluorite stages associated with sphalerite pyrite galena barite and quartz have been distinguished using optical cathodoluminescence and scanning electron microscopes seven crystals of the geodic fluorite stage were analyzed for their rare earth element ree contents and their 147sm 144nd and 143nd 144nd isotopic compositions the normalized ree distribution displays homogeneous bell shaped patterns for all the geodic fluorite samples with a mid ree enrichment over the light ree and heavy ree the 147sm 144nd varies from 0 3108 to 0 5504 and the 143nd 144nd from 0 512313 to 0 512518 a six point sm nd isochron defines an age of 130 15 ma initial 143nd 144nd 0 512054 mswd 0 21 this sm nd isochron provides the first age for the stratabound fluorite sediment hosted deposit related to an unconformity in the paris basin and highlights a major early cretaceous fluid circulation event mainly above the basement sediment unconformity during a flexural deformation of the paris basin which relates to the rifting of the bay of biscay and the formation of the ligurian sea in the western europe domain

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

a newly designed analytical line to examine fluid inclusion isotopic compositions in a variety of carbonate samples 18 o and d of fluid inclusions in carbonates provide insights into temperatures and fluid chemical compositions prevailing during the carbonate precipitation however various analytical restrictions limit a wider application of this proxy this paper presents a new fluid inclusions isotopic analytical line coupled to an online cavity ring down spectrometer that increased the analytical productivity up to 10 carbonate samples per working day this efficiency allowed for the first time to assess the reliability a large set of water samples with size ranging from 0 1 to 1 l good reproducibility 0 5 for 18 o and 2 d 1 is obtained for water quantity superior or equal to 0 3 l and no evidence of memory effect is found the line is further tested using two types of natural carbonates 1 modern speleothems samples from caves for which 18 o and d values of drip water were measured and 2 diagenetic carbonates for which the 18 o of the parent water were independently back calculated from carbonate clumped isotope 47 measurements speleothem fluid inclusion values despite falling close to the global meteoritic water line are not always representative of the isotopic composition of the parent drip water results on diagenetic cements show that the 18 o water values measured in fluid inclusions agree within 1 with the 18 o water independently derived from 47 measurements overall this study confirms the reliability and accuracy of the developed analytical line for carbonate fluid inclusion analyses with a good reproducibility obtained for water quantity above 0 3 l

stable isotope conservation and origin of saline waters from the middle jurassic aquifer of the paris basin france abstract seventy nine samples of formation water from geothermal boreholes oil field and ground water wells tapping the dogger middle jurassic limestone reservoir of the paris basin have been analyzed for their 2h 18o tds bromide and chloride contents geostatistical mapping of 2h and of 18o contents and their variations with chloride content indicate that both isotopes have a common origin and a similar behaviour within the aquifer the 2h and 18o values increase progressively from the outcrops toward a zone where temperature cl and tds values are high the 2h and 18o values are very uniform in this zone and do not show any relation with formation temperature in contrast to what is generally observed in other sedimentary basins a discussion of isotopes exchange with the carbonate matrix for oxygen and with h2s for deuterium shows that such processes are not controlling the heavy isotope contents of groundwaters this is attributed to the relatively short residence time of groundwaters in the aquifer both 2h and 18o contents of groundwater may thus be considered as conservative tracers in the dogger aquifer of the paris basin and their initial contents are modified only by fluid mixings complex mixing processes account for stable isotope composition tds cl and br values of the dogger fluids all mixtures include a brine component meteoric water percolated and dissolved halite in the triassic aquifer secondary brine this saline solution mixed with some residual primary brine then migrated via vertical faults into the dogger aquifer such migration is found to be in agreement with data from fluid inclusions in late carbonate cements from the liassic and dogger strata the requirement that these units were exposed implies that meteoric invasion could not have occurred before the tertiary successive mixings of the brine with several types of meteoric waters depleted in heavy isotopes account for the present isotope and chemical compositions of the dogger fluids

crustal thickness map of the chinese mainland from teleseismic receiver functions abstract we present a new crustal thickness map of the chinese mainland and adjacent areas based on a compilation of previously published data more than 1900 estimates of crustal thickness from receiver function studies were collected and the weighted averages were used to develop a contour map of crustal thickness beneath the chinese mainland the combined dataset provided good coverage especially over eastern and central china and our analysis revealed crustal thickness variations of the chinese mainland with considerably more detail than in previous models our crustal thickness map shows a large variation from a thickness of less than 30 km in the mesozoic basin of eastern china to over 80 km in the tibetan plateau the thickest crust was found in central tibet while the thinnest continental crust was observed beneath eastern china normal to slightly thick crust 38 51 km was found for the stable precambrian basins and orogenic belts comparison between our model and other models reveals that the models share similar large scale and smaller scale features over large portions of eastern china where the data coverage is good however large differences up to 25 km in crustal thickness occur in areas with complex crustal structure or poor data coverage we also evaluated the quality of previous models by comparing them with our newly compiled point observations of crustal thickness

syndepositional deformation features in high relief carbonate platforms long lived conduits for diagenetic fluids abstract syndepositional faults and fractures are known to affect early fluid flow in carbonate platforms less clear is whether they are active fluid conduits throughout the entire history of the platform strata syndeformational fractures in permian late guadalupian carbonates exposed in dark canyon guadalupe mountains new mexico u s a address this question transmitted light and cathodoluminescent petrography stable isotope and fluid inclusion analyses and clumped isotope thermometry show that there were multiple episodes of fracturing dissolution cementation and replacement in the fractures dolomite cement or dolomitized marine cements line the walls of some fractures and indicate the syndepositional reflux of evaporated permian seawaters through the fractures fine to medium crystalline luminescently zoned calcite may overlie the dolomite and marine cements line fracture walls where those phases are absent or cement karst breccia on fracture walls the 18o values of this calcite 8 8 to 14 0 vpdb and clumped isotope temperatures 16 to 32 c indicate precipitation from meteoric fluids 18osmow of 6 2 to 10 5 associated with episodic sea level lowstands during the development of high frequency depositional sequences the early calcites can themselves be fractured rotated and recemented indicating recurrent deformation and meteoric influx evaporite cements were once the dominant pore filling phase in the fractures forming both before and after the early meteoric cements the earliest evaporites formed during deposition of tansill limestone probably from the same brines that formed dolomites evaporites that postdate the early calcite probably did not form until permo triassic burial when geomechanical analysis indicates that the syndepositional fractures were likely reactivated and brines could have been sourced from overlying bedded evaporite all evaporite cements subsequently were calcitized mainly by coarse crystalline inclusion rich calcites that formed from warm 59 to 96 c fluids calculated fluid isotopic compositions 18osmow of 0 5 to 4 7 imply mixing of meteoric and oil field brines carbon isotope values 2 to 17 indicate microbial degradation of hydrocarbons in some of those fluids but not all geomechanical analysis indicates the potential for syndepositional fractures to have failed reactivated during basin and range extension and the warm basinal fluids are interpreted to have migrated upward through the fractures during that event platform margin fractures unassociated with faults witnessed cooler fluids 59 to 65 c than outer shelf fractures 70 to 96 c because outer shelf faults tapped waters from greater depths the most recent fluid flow through the fractures generated dissolution features and laminated speleogenetic calcites which are interpreted to result from intrastratal karsting associated with exhumation and weathering diagenetic features in the syndepositional fractures are equivalent to those observed in the adjacent limestones suggesting active fluid communication between matrix and fractures throughout the diagenetic history of the rocks the complex fracture paragenesis also indicates that syndepositional fractures are not only conduits for early fluid flow networks but they can also impact a rock s entire diagenetic history if reactivated by changing stress fields

mantle transition zone topography and structure beneath the central tien shan orogenic belt 1 in this study we calculated receiver functions rfs from teleseismic p waveforms recorded by stations of four seismic networks to determine the topography of the mantle transition zone mtz beneath the central tien shan we converted the rfs from the time domain to the depth domain and selected the depths of 410 and 660 km discontinuities after stacking the rfs in narrow raypath bins to better determine the mtz topography we applied an updated rf method to invert the depth differences between the 410 and 660 km discontinuities in each rf for lateral depth variations of the two discontinuities using this approach we detected several anomalies in the 410 and 660 km discontinuity depths beneath the central tien shan region extensive synthetic tests were carried out to confirm the main features of the result beneath the south and east of lake issyk kul the 410 km discontinuity becomes shallower while the 660 km discontinuity becomes deeper leading to a thicker mtz with a lower temperature possibly caused by pieces of thickened lithosphere dropping down to at least the bottom of the mtz beneath the northwest of lake issyk kul the 410 km discontinuity becomes deeper while the 660 km discontinuity becomes shallower resulting in a thinner mtz with a higher temperature which may reflect a small scale hot upwelling from the lower mantle

past hot fluid flows in limestones detected by δ47 u pb and not recorded by other geothermometers geothermometers are commonly used to reconstruct the diagenetic and thermal history of rocks however characterizing the timing origin and temperature of paleofluid flow remains challenging because it must be assessed indirectly through the analysis of microscopic cements that precipitate and fill intergranular spaces during fluid circulation here we measure both the clumped isotope 47 temperature and in situ u pb age of individual diagenetic calcite cements within a sedimentary section of the paris basin france whose thermal history has been previously inferred to be 70 c have been measured for calcite cements containing single phase aqueous fluid inclusions challenging the commonly accepted assertion that the absence of nucleation of a vapor phase indicates crystallization at low temperature 70 c we suggest that the kinetics of mineralization events prevented the recording of short lived hot fluid flows by other

carbonate clumped isotope bond reordering and geospeedometry carbonate clumped isotope thermometry is based on the preference of 13c and 18o to form bonds with each other at elevated temperatures such bond ordering is susceptible to resetting by diffusion of c and o through the solid mineral lattice this type of bond reordering has the potential to obscure primary paleoclimate information but could also provide a basis for reconstructing shallow crustal temperatures and cooling rates we determined arrhenius parameters for solid state reordering of c o bonds in two different calcites through a series of laboratory heating experiments we find that the calcites have different susceptibilities to solid state reordering reaction progress follows a first order rate law in both calcites but only after an initial period of non first order reaction that we suggest relates to annealing of nonequilibrium defects when the calcites are first heated to experimental temperature we show that the apparent equilibrium temperature equations or closure temperature equations for carbonate clumped isotope reordering are analogous dodson s equations for first order loss of daughter isotopes for each calcite the sensitivity of apparent equilibrium temperature to cooling rate is sufficiently high for inference of cooling rates within a factor of 5 or better for cooling rates ranging from tens of degrees per day to a few degrees per million years however because the calcites have different susceptibilities to reordering each calcite defines its own cooling rate apparent equilibrium temperature relationship the cooling rates of carrara marble inferred from carbonate clumped isotope geospeedometry are 10 6 10 3 degrees per annum and are in broad agreement with rates inferred from thermochronometric methods cooling rates for 13c depleted calcites from the late neoproterozoic doushantou cap carbonates in south china are on the order of 102 104 degrees per annum consistent with rapid cooling following formation of these calcites by a short lived hydrothermal event bristow et al 2011 nature v 474 p 68 71 most of the uncertainty in these estimates relates to uncertainty in arrhenius parameters for different calcites thus while the carbonate clumped isotope geospeedometer shows promise for recording cooling rates in settings and lithologies where other geospeedometers may not be applicable the uncertainty in cooling rate will be large without independent knowledge of the reordering kinetics of each study material thus the full potential of the method will only be realized if reordering kinetics can be accurately determined for each study material or predicted on the basis of mineral composition texture or other observable parameters

chronostratigraphic significance of cathodoluminescence zoning in syntaxial cement mississippian lake valley formation new mexico abstract echinoderm syntax ial cement crystals have been collected at several stratigraphic levels within the lake valley formation which is overlain by a major pre pennsylvanian subaerial exposure surface the crystals were microsampled along growth bands and yielded high resolution elemental and isotopic information that record fluid evolution during their growth although cement crystals show little variation in cathodoluminescence character and bulk chemistry throughout the regional extent of the formation intracrystalline patterns in minor element and stable isotope chemistry allow for the identification of several settings of cementation including the marine phreatic marine meteoric mixing and meteoric phreatic zones when placed in a regional stratigraphic context crystal growth records enable reconstruction of the temporal and spatial extent of these diagenetic environments isotopic petrographic and stratigraphic constraints indicate that cementation was related to two temporally distinct meteoric systems most lake valley formation syntaxial cement formed in the marine phreatic and marine meteoric mixing zones during the earliest phase of cementation of this cement in excess of 60 formed in the marine phreatic zone and lowermost marine meteoric mixing zone smaller volumes precipitated from progressively fresher mixtures of marine and meteoric fluid during the gradual expansion of a freshwater lens that developed in response to pre pennsylvanian lowering of sea level meteoric phreatic fluids were relatively unimportant during this episode of cementation in contrast cement of entirely meteoric phreatic origin is associated with a later meteoric system but is found only in the northern part of the study area and at stratigraphic levels immediately adjacent to the pre pennsylvanian unconforrnity our results indicate that cements in the upper and lower parts of the lake valley formation are genetically and temporally unrelated thus the cement cathodoluminescence stratigraphy which has been previously applied to the lake valley can not be valid over the full extent of the formation this has wider implications our demonstration that diverse and temporally distinct diagenetic settings can produce identical cl characteristics shows that caution should be employed when using cement cl stratigraphy alone to extend diagenetic interpretations over large geographic regions or through substantial stratigraphic successions

lower paleogene denudation of upper cretaceous cover of the morvan massif and southeastern paris basin france revealed by aft thermochronology and constrained by stratigraphy and paleosurfaces abstract low temperature thermochronology data have been acquired from outcrop samples from the southeastern edge of the paris basin morvan they provide indications about the former sedimentary cover its denudation and about inversion tectonics in the paris basin apatite fission track data acquired on variscan granites and triassic sandstones reveal that the basement was subjected to temperatures of about 70 10 c during the late cretaceous we suggest that the peak temperature was generated by an upper cretaceous sedimentary cover of low thermal conductivity chalk additional stratigraphic sedimentological paleogeographic paleoweathering and continental paleosurface data support the reconstruction of this chalk paleocover and of its erosion this former blanketing sequence was removed during the early paleogene regional inversion episode which affected the southern edge of the basin intensively and was related to far field compression between europe and africa this study shows that i for the se border of the intracontinental paris basin kilometer scale vertical deformation occurred ii the sedimentary sequences of the paris basin covered considerably larger areas than the present contours of the sediment fill iii paleoweathering and erosion processes later removed the sedimentary cover rather quickly

impact of basin burial and exhumation on jurassic carbonates diagenesis on both sides of a thick clay barrier paris basin ne france several diagenetic models have been proposed for middle and upper jurassic carbonates of the eastern paris basin the paragenetic sequences are compared in both aquifers to propose a diagenetic model for the middle and late jurassic deposits as a whole petrographic optical and cathodoluminescence microscopy structural fracture orientations and geochemical 18o 13c ree studies were conducted to characterize diagenetic cements with a focus on blocky calcite cements and their connection with fracturation events four generations of blocky calcite cal1 cal4 are identified cal1 and cal2 are widespread in the dominantly grain supported facies of the middle jurassic limestones about 90 of the cementation whereas they are limited in the oxfordian because grain supported facies are restricted to certain stratigraphic levels cal1 and cal2 blocky spars precipitated during burial in a reducing environment from mixed marine meteoric waters and or buffered meteoric waters the meteoric waters probably entered aquifers during the late cimmerian jurassic cretaceous boundary and late aptian early cretaceous unconformities the amount of cal2 cement is thought to be linked to the intensity of burial pressure dissolution which in turn was partly controlled by the clay content of the host rocks cal3 and cal4 are associated with telogenetic fracturing phases the succession of cal3 and cal4 calcite relates to the transition towards oxidizing conditions during an opening of the system to meteoric waters at higher water rock ratios these meteoric fluids circulated along pyrenean oligocene and alpine fractures and generated both dissolution and subsequent cementation in oxfordian vugs in mud supported facies and in poorly stylolitized grainstones however these cements filled only the residual porosity in middle jurassic limestones in addition to fluorine inputs fracturation also permitted inputs of sulphur possibly due to weathering of triassic or purbeckian evaporites or h2s input during paleogene times

new insight into crustal and lithospheric variability beneath the central tien shan nw china revealed by p wave receiver functions abstract the tien shan has experienced intensive crustal shortening and lithospheric deformation making it an ideal site to study the orogeny processes we applied p wave receiver functions to get new insight into crustal and lithospheric variability beneath the central shan region clear p to s converted phases are observed at many recording stations exhibiting double positive converted phases at 5 9 s the corresponding crustal thickness varies from 35 km to 70 km which appears to be relatively thinner beneath the kazakh shield and tarim basin and thicker beneath the southern and northern flanks of the central tien shan the negative converted phases are observed at depths of 30 45 km beneath the central tien shan corresponding to the extremely low seismic velocities in the middle to lower crust revealed by seismic tomography the receiver function results coupled with a regional shear wave velocity model suggest that the lithosphere of the central tien shan has been significantly modified the thickening and thinning of lithosphere may be related to up warped and down warped of mantle and could be associated with the mantle upwelling triggered by bilateral underthrusting of the tarim basin and the kazakh shield respectively beneath the central tien shan

chronology of fracture sealing under a meteoric fluid environment microtectonic and isotopic evidence of major cainozoic events in the eastern paris basin france abstract a detailed reappraisal of the sequence of tectonic stages that has affected the eastern part of the paris basin from the late jurassic to the end of cainozoic is presented in order to improve knowledge of the relationships between tectonics and fluid mass palaeo transfers in that basin this goal was performed in two steps i establishing a relative tectonic chronology on the basis of numerous observations and detailed analysis of geometrical relationships between striated planes vertical and bedding stylolites and tension gashes and ii discussing the geochemical signatures 18 o and 13 c of calcite from fracture infillings well positioned within the relative tectonic chronology the resulting tectonic sequence agrees with the main events described by previous papers but the present work details the pyrenean s l eocene oligocene and alpine miocene pliocene convergence stages and explains the mechanisms of the oligocene miocene transition between the two previous events the different tectonic stages are as follows i late jurassic to early cretaceous extension starting with a wnw ese direction but changing to e w ii the pyrenean convergence eocene changing from nne ssw to ne sw and finally ene wsw compression iii oligocene transition from pyrenean to alpine convergence marked by a drastic evolution of main stress which swaps from a horizontal position to a vertical one and radial extension marked by a strong reactivation of bedding stylolitisation iv the alpine convergence late miocene to present day changing from wnw ese to nnw sse direction of shortening 18 o and 13 c values of calcite from tension gashes associated to each tectonic stage spread from 18 to 27 smow and from 0 8 to 3 pdb respectively according to the maximum thermal history of this part of the basin t max 40 c or 60 c according to the available published estimates the calculated 18 o values of fluids 7 to 4 involved in mass transfer processes are interpreted as meteoric the lowest 18 o values 18 20 are located around the main regional faults and associated with 13 c values that are rather different from those of host rocks in contrast calcites from non faulted area present a higher 18 o 20 and 13 c values close to those of host rocks these data are explainable in terms of differences in the fluid rock ratios prevailing during carbonate redistribution the highest ratios being associated to discontinuities faults sometimes with hydraulic breccias that were active during the tertiary tectonic events outside the fault zones the isotopic compositions of calcite from tension gashes are similar at the regional scale to those of calcite from geodes or cements analysed in previous studies on localized areas as a result we emphasize the fact that a significant part of the carbonate redistribution in the middle to upper jurassic limestones from the eastern paris basin occurred during the tertiary s l enlightening the influence of distant orogenic systems extensive or compressive in the matter redistribution within sedimentary basins at variance of models inferring a porosity cementation predominantly during burial

shear wave splitting at central tien shan evidence for rapid variation of anisotropic patterns at active collisional belts the fast polarization axis of shear wave splitting is generally aligned parallel to the strike of the belt which has been proposed to indicate mantle strain that is coherent with crustal deformation a notable exception is central tien shan where anomalous patterns of splitting have previously been observed we here analyze shear wave splitting of sks phases across north central tien shan using digital data from the kyrgyzstan broadband seismic network knet we find a pattern of short wavelength anisotropic heterogeneity that supports complex mantle flow due to small scale convection the along strike variations in mantle structure contrast with the coherent pattern of crustal shortening and indicate that mantle flow is not directly coupled to crustal deformation in this region

isotopic and geochemical characterization of fossil brines of the cambrian mt simon sandstone and ironton galesville formation from the illinois basin usa abstract geochemical and isotopic characteristics of deep seated saline groundwater provide valuable insight into the origin and evolving composition water rock interaction and mixing potential of fossil brines such information may yield insight into intra and interbasinal brine movement and relationships between brine evolution and regional groundwater flow systems this investigation reports on the 18o and d composition and activity values 87sr 86sr ratios and sr concentrations and major ion concentrations of the cambrian hosted brines of the mt simon sandstone and ironton galesville formation and discusses the evolution of these brines as they relate to other intracontinental brines brines in the illinois basin are dominated by na ca cl type chemistry the mt simon and overlying ironton galesville brines exhibit total dissolved solids concentrations of 195 000 mg l and 66 270 mg l respectively the d of brine composition of the mt simon ranges from 34 to 22 v smow and the ironton galesville is 53 2 v smow the 18o composition of the mt simon brine ranges from 5 0 to 2 8 v smow and the ironton galesville brine is 6 9 v smow the 87sr 86sr values in the mt simon brine range from 0 7110 to 0 7116 the less radiogenic ironton galesville brine has an average 87sr 86sr value of 0 7107 evaluation of 18o and d composition and activities and 87sr 86sr ratios suggests that the mt simon brine is likely connate seawater and recirculating deep seated brines that have been diluted with meteoric water and influenced by the dissolution of evaporites with a minimal halite contribution based on cl br ratios the ironton galesville brine is also likely originally connate seawater that mixed with other brines and meteoric waters including possibly pleistocene glacial recharge the ca excess vs na deficiency comparison with the basinal fluid line suggests the mt simon and ironton galesville brines have been influenced by the effects of albitization and plot very close to the basinal fluid line these cambrian hosted brines appear to have a different albitization history than other regional basin brines and a strong component of seawater the ironton galesville brine appears more geochemically associated with other illinois basin brines than the mt simon brine which appears more geochemically conservative comparisons with other extrabasinal north american brines suggest that the michigan basin brines are geochemically most similar to the mt simon brines with the exception of the influence from carbonates in the michigan basin analyses of 87sr 86sr values in the mt simon brine suggest that brine sr has isotopically equilibrated with clay minerals in the lower mt simon and underlying bedrock formations and not with whole rock suggesting the influence of recirculating brines from the crystalline basement overall the geochemistry of these cambrian hosted brines suggests an evolution from original seawater like compositions this investigation shows that intracratonic basins do not behave as closed systems but can be strongly affected by water rock interaction and regional groundwater flow systems that circulate deep crystalline basement brines and brines from nearby basins

sulphur and oxygen isotopes of dissolved sulphur species in formation waters from the dogger geothermal aquifer paris basin france isotopic analyses of the s in sulphides and sulphates from formation waters were made at 35 geothermal wells exploiting the dogger geothermal aquifer of the paris basin isotopic analyses of the o of the dissolved sulphates were also made on 12 of these the results show a distribution of the 34s of the sulphates according to geographic zones that also correspond to variations in the geochemistry of the fluids in particular the sulphide content samples taken in the seine st denis area and in the areas north and west of paris show high 34s values ranging from 26 3 to 48 9 values of 34s for sulphides range from 8 5 to 5 and are interpreted as reflecting the effect of bacterial reduction in a confined part of the basin modelling this reduction by a rayleigh distillation mechanism made it possible to calculate a value of 1 038 0 003 for the coefficient of fractionation between the sulphates and sulphides we show that an important part of the sulphides formed by bacterial reduction has been subtracted from the fluid by deposition south of paris and in the val de marne the 34s values for the sulphates are more uniform ranging between 22 4 and 26 6 despite the existence of bacterial activity this is most probably due to a higher rate of flow of the waters entailing renewal of the sulphate stock the isotopic composition of the o of the sulphates for the seine st denis area and the areas west and north of paris is very uniform between 16 1 and 17 1 despite the wide range in 34s 26 3 to 48 9 for the same samples the calculated isotopic temperatures are close to those measured in situ these results suggest either that sulphate water isotopic equilibrium was established after the reduction or that the coefficient of o fractionation is very low 1 003 during bacterial reduction

northwest pacific fundamental mode rayleigh wave group velocity and its relationship with tectonic structures the fundamental mode rayleigh wave generated by 27 earthquakes and recorded at 11 digital broadband seismic stations belonging to the ocean hemisphere project network in the northwest pacific region are analyzed to estimate the rayleigh wave group velocity for 160 paths at periods from 10 to 50 sec the inverted group velocity results suggest a quasi continental oceanic transitional structure of the north west pacific ocean with 21 km as an average crustal thickness the rayleigh wave group velocity tomography results for short time periods 10 50 sec showed a good correlation with known geological and tectonic features and were consistent with the tectonic complexities of the region slow velocity anomalies at varying periods correspond to ridges basins trenches and volcanic fronts of the northwest pacific ocean while the fast velocity anomalies show the effects of plate interactions at relatively longer periods 30 50 sec a triple junction formed by the subduction of the phillipine sea and pacific plates beneath the eurasian plate is imaged by a high velocity zone in this study

evolution of neoproterozoic wonoka shuram anomaly aged carbonates evidence from clumped isotope paleothermometry the wonoka shuram anomaly represents the largest negative carbon isotope excursion recognized in the geologic record and is associated with the emergence and diversification of metazoan life ca 580 million years ago ma the origin of the anomaly is highly debated with interpretations ranging from primary to diagenetic each having unique and potentially transformative implications for early life here we apply carbonate clumped isotope thermometry to three sections expressing the anomaly in order to constrain mineral formation temperatures and thus directly calculate water oxygen isotope compositions 18ow with which carbonate minerals equilibrated with 18ow known it is possible to address previous hypotheses for the origin of the anomaly in each section precipitation temperatures correlate positively with reconstructed 18ow previous hypotheses based on the covariance of 18ocarb vs 13ccarb uncorrected for temperature effects suggested a meteoric diagenetic origin for the anomaly however reconstructed 18ow values do not covary with carbon isotope compositions 13ccarb within anomaly facies rather the oxygen isotope and temperature data are consistent with carbonate recrystallization and equilibration under increasingly rock buffered conditions based on simple modeling and comparison to modern formation fluids recrystallization may have occurred in an environment far removed from the initial depositional or early diagenetic regime in addition although clumped isotope temperatures vary significantly and reach elevated values consistent with burial diagenesis it is unclear to what degree if at all carbon isotope values were reset during recrystallization ultimately these new data indicate that wonoka shuram aged carbonates experienced equilibration with fluids under increasingly closed system conditions the clumped isotope data do not provide a means to distinguish previous hypotheses outright but provide additional context for the evaluation of geochemical signatures within these ancient carbonate rocks

bedding parallel stylolites as a tool to unravel maximum burial depth in sedimentary basins application to middle jurassic carbonate reservoirs in the paris basin france in recent years stylolites which are rough dissolution surfaces commonly found in carbonates have been used for paleopiezometry estimates the stylolite roughness inversion technique srit applied on sedimentary bedding parallel stylolites bps grants access to the maximum principal vertical stress experienced by the host carbonates and thus to their maximum burial paleo depth this study reports the results of srit applied to a bps population hosted in carbonate platform reservoirs of the paris basin sub surface france middle jurassic carbonates from two well cores from the depocenter and margin of the basin for which the burial and thermal history are known based on a thermally calibrated 3 d basin model were analyzed by defining a consistency criterion and using two signal treatment methods we propose a new approach to select which bps can be reliably used to reconstruct the maximum vertical stress undergone by the host carbonates which then can be converted into maximum burial depth the study of a bps population shows that there is a control operated by the host rock texture and the stylolite morphology on the burial depth recorded especially suture and sharp peak bps are better suited to estimate the real maximum depth whereas seismogram pinning bps record preferentially intermediate depths median values of maximum depth derived from our data set 1300 and 1650 m for the margin and depocenter cores respectively are in line with maximum burial estimates provided by conventional basin modeling 1450 and 1800 m respectively thus showing that srit is a standalone robust depth gauge in sedimentary basins provided sample selection and data treatment are carried out in a rigorous and thoughtful manner

three dimensional elastic wave velocity structure of the western and central tien shan arrival times of compressional p and shear s waves generated by earthquakes at local and teleseismic distances and recorded by seismographs located in the western and central tien shan are used to determine one and three dimensional elastic wave velocity structures of the crust and upper mantle beneath the mountain belt the best fit one dimensional structures suggest that the average depth of the mohorovicic discontinuity in this area is 50 km the three dimensional structure of the upper crust reveals thick sediments within each of the major depressions in the region a 7 km thick wedge of sediment beneath the chu depression is outlined at depth by a south dipping plane of seismic activity suggesting the presence of an active decollemont these low velocities extend continuously to the southeast toward issyk kul suggesting a structural relationship between the two however rather than being consumed it appears that issyk kul is overthrusting the surrounding ranges the low velocity sediments in the fergana basin reach depths of 10 km and are bounded on three sides by amorphous bands of seismicity velocities at midcrustal depths generally are lower beneath the central tien shan than beneath the western tien shan this pattern becomes more evident in the uppermost mantle with p velocity contrasts of as much as 10 across a boundary that corresponds roughly to the geographical position of the talasso fergana fault the low velocities beneath the central tien shan exceed 150 km depth but do not appear to be deeper than 300 km depth there is no evidence for a lithospheric root beneath this part of the range rather the low velocities imply the presence of a positive buoyancy force uplifting the mountains evidence that this low velocity region existed before the collision suggests that the tien shan may not owe its rejuvenation simply to its location at the northern edge of a strong tarim basin but rather to an anomalous upper mantle that was easier to deform than the surrounding lithosphere

thermal evolution of the intracratonic paris basin insights from 3d basin modelling abstract the thermal evolution of the paris basin pb has been widely studied using 1d 2d and more rarely 3d thermal models it is well documented that the pb experienced higher temperatures in the past compared to what is currently observed however a quantitative analysis of the main processes and parameters that affect the temperature distribution at the basin scale and over time is still not available in this study through basin modeling which accounts for the main processes of the thermal evolution of sedimentary basins we analyze and quantify the role of the different geological mechanisms by discriminating the causes of abnormal temperatures during the late mesozoic this is done with a 3d basin model built from base moho to present day topography using the temisflow basin modelling software the model includes thermal processes within an evolving upper crust defined by three main structural domains each crustal sector presents radiogenic heat production conductivity and thickness values which are used as input parameters to reproduce the paleo and present day basal heat flow variations observed in the basin the model calculates heat flow through time in both crust and sedimentary column where the crust is coupled with the geological evolution of the basin this approach allows estimating the eroded thickness during the main tertiary uplift event and therefore the maximum temperature in the late cretaceous the model is constrained by different types of paleo thermo chronometers and by 52 wells that are regionally distributed over the entire basin resulting in a new regional thermal history of the pb the amount of missing section in the cretaceous chalk which mainly affected the eastern part of the basin is increased by up to 500m compared with previous studies and constitutes the key controlling factor of the temperature evolution this new regional thermal history of the paris basin may be important for further analysis of the hc generation from the lower jurassic toarcian source rock and bring new insights into the geothermal potential of the basin

calibration of the oxygen and clumped isotope thermometers for proto dolomite based on synthetic and natural carbonates abstract dolomite is a very common carbonate mineral in ancient sediments but is rarely found in modern environments because of the difficulties in precipitating dolomite in the laboratory at low temperatures the controls on its formation are still debated after more than two centuries of research two important parameters to constrain the environment of dolomitization are the temperature of formation and the oxygen isotope composition of the fluid from which it precipitated carbonate clumped isotopes expressed with the parameter 47 are increasingly becoming the method of choice to obtain this information however whereas many clumped isotope studies treated dolomites the same way as calcite some recent studies observed a different phosphoric acid fractionation for 47 during acid digestion of dolomite compared to calcite this causes additional uncertainties in the 47 temperature estimates for dolomites analyzed in different laboratories using different acid digestion temperatures to tackle this problem we present here a proto dolomite specific 47 temperature calibration from 25 to 1100 c for an acid reaction temperature of 70 c and anchored to widely available calcite standards for the temperature range 25 to 220 c we obtain a linear 47 t relationship based on 289 individual measurements with r2 of 0 864 47 cdes 70 c 0 0428 0 0020 10 6 t 2 0 1481 0 0160 t in kelvin when including two isotopically scrambled dolomites at 1100 c the best fit is obtained with a third order polynomial temperature relationship r2 0 924 47 cdes 70 c 0 0002 10 6 t 2 3 0 0041 10 6 t 2 2 0 0115 10 6 t 2 0 2218 applying a calcite 47 t relationship produced under identical laboratory conditions results in 3 to 16 c colder calculated formation temperatures for dolomites with formation temperature from 0 to 100 c than using the proto dolomite specific calibration presented here for the synthetic samples formed between 70 and 220 c we also determined the temperature dependence of the oxygen isotope fractionation relative to the water based on the similarity between our results and two other recent studies vasconcelos et al 2005 and horita 2014 we propose that a combination of the three datasets represents the most robust calibration for proto dolomite formed in a wide temperature range from 25 to 350 c 10 3 camg carbonates water 2 9923 0 0557 10 6 t 2 2 3592 0 4116 because of the uncertainties in the phosphoric acid oxygen and clumped isotope fractionation for proto dolomite we promote the use of three samples that are available in large amounts as possible inter laboratory reference material for oxygen and clumped isotope measurements a sample of the middle triassic san salvatore dolomite from southern switzerland the nist srm 88b dolomite standard already reported in other 47 studies and a lacustrine pliocene dolomite from la roda spain this study demonstrates the necessity to apply proto dolomite specific 47 t relationships for accurate temperature estimates of dolomite formation ideally done at identical acid digestion temperatures to avoid additional uncertainties introduced by acid digestion temperature corrections in addition the simultaneous analyses of dolomite reference material will enable a much better comparison of published dolomite clumped and oxygen isotope data amongst different laboratories

clumped isotope geochemistry the study of naturally occurring multiply substituted isotopologues clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials that is it examines the extent to which rare isotopes d 13 c 15 n 18 o etc bond with or near each other rather than with the sea of light isotopes in which they swim abundances of isotopic clumps in natural materials are influenced by a wide variety of factors in most cases their concentrations approach within ca 1 relative the amount expected for a random distribution of isotopes deviations from this stochastic distribution result from enhanced thermodynamic stability of heavy isotope clumps slower kinetics of reactions requiring the breakage of bonds between heavy isotopes the mass dependence of diffusive and thermo gravitational fractionations mixing between components that differ from one another in bulk isotopic composition biochemical and photochemical fractionations that may reflect combinations of these simpler physical mechanisms and in some cases other processes we do not yet understand although clumped isotope geochemistry is a young field several seemingly promising applications have already emerged most importantly it appears that proportions of 13 c 18 o bonds in carbonate minerals are sensitive to their growth temperatures independent of bulk isotopic composition thus clumped isotope analysis of ancient carbonates can be used as a quantitative paleothermometer that requires no assumptions about the 18 o of waters from which carbonates grew this approach has been used to reconstruct marine temperatures across the phanerozoic reaching back to the silurian terrestrial ground temperatures across the cenozoic thermal histories of aqueously altered meteorites among other applications clumped isotope geochemistry is also placing new constraints on the atmospheric budget and stratospheric photochemistry of co 2 and should be capable of placing analogous new constraints on the budgets of other atmospheric gases finally this field could be extended to encompass sulfates volatile hydrocarbons organic moieties and other materials

multi phase dolomitization and recrystallization of middle triassic shallow marine peritidal carbonates from the mecsek mts sw hungary as inferred from petrography carbon oxygen strontium and clumped isotope data abstract shallow marine to peritidal carbonates of the triassic csukma formation in the mecsek mts of sw hungary are made up of dolomites limestones and dolomitic limestones that show evidence of a complex diagenetic history integration of petrographic conventional stable oxygen and carbon isotope clumped isotope and strontium isotope data with the paleogeography paleoclimate and burial history of the region revealed four major diagenetic stages stage 1 the peritidal carbonates were dolomitized penecontemporaneously during the middle triassic by refluxing evaporatively concentrated brines stage 2 increasing burial during the late triassic jurassic resulted in recrystallization of the kan dolomite member in an intermediate burial setting stage 3 during the early cretaceous seawater was drawn down and circulated through rift related faults causing renewed recrystallization of the kan dolomite member as well as dolomitization of the kozar limestone member and the underlying limestones in a deep burial setting but only in the vicinity of the faults stage 4 during the late cretaceous and cenozoic thrusting resulted in tectonic expulsion of basinal fluids and precipitation of multiple saddle dolomite cement phases near the faults the results of this study imply that the clumped isotope method integrated with other geochemical data can successfully be applied to identify the nature and potential sources of extra formational diagenetic fluids responsible for dolomitization and recrystallization this study provides conclusive evidence for multi phase dolomitization and dolomite recrystallization over several millions of years middle triassic through early cretaceous and several thousands of meters of burial in the csukma formation in sw hungary furthermore this study is the first to identify fault controlled dolomitization by circulating cretaceous seawater within triassic carbonates of central europe further supporting the viability of the interpretation of dolomitization by seawater initially drawn down and then geothermally circulated through faults in extensional basins

impact of geodynamics on fluid circulation and diagenesis of carbonate reservoirs in a foreland basin example of the upper lacq reservoir aquitaine basin sw france abstract orogeny driven fluids that circulate in foreland basins can have strong impacts on petroleum systems and reservoir properties this applies to the upper cretaceous lacq reservoir of the aquitaine basin in southwestern france located north of the pyrenean mountains we study a drillcore from a 650 m deep oil reservoir to document how the evolution of a foreland basin which formed after a hyperextension phase affected fluid circulation and eventually reservoir diagenesis using drillcore samples petrographic observations fluid inclusion studies coupled with thermodynamic modeling isotopic and rare earth element geochemistry as well as basin modeling were performed to investigate and describe the fluid types and sources the pressure temperature evolution and the timing of diagenetic fluid flow early diagenesis involves some bacterial activity represented by micrite rims and framboidal pyrites as well as early dolomitization involving a mixture of meteoric and formation fluids during burial dolomite overgrowth saddle dolomites coarse blocky calcites and anhydrites precipitate the last products consist of iron oxide precipitation and meteoric recharge of the reservoir with groundwater our results indicate that after the deposition of the paleocene flysch formation mg rich low salinity hot and relatively deep clay released fluids migrated along thrust faults from deeper parts of the basin during the climax of the compressional pyrenean phase eocene they acted as dolomitizing hydrothermal fluids with a thermal disequilibrium in the order of 30 40 c hotter than the ambient host rocks another orogeny driven hydrothermal and mg poor fluid mixed with oil generated by jurassic barremian source rocks and precipitated calcites and anhydrites finally during uplift oxidizing fluids were laterally introduced as the present day groundwater hence by combining different petrographic geochemical and modeling proxies we document how the eocene orogenic phase played a crucial role in basin scale fluid flow and carbonate diagenesis

elevation of the 410 km discontinuity beneath the central tien shan evidence for a detached lithospheric root we analyzed p sv converted phases recorded by the kyrgyzstan broadband network knet to investigate the nature of phase transitions in the upper mantle beneath the central tien shan and the kazakh shield we find that p sv phases from the 410 km discontinuity recorded by several stations located along the range front are about 2 s earlier from beneath the tien shan than they are from beneath the kazach shield because the delay times at stations located on the kazakh shield are normal and seismic velocities in the upper mantle beneath this part of the tien shan apparently are low about 4 less than the kazakh shield to the north the early arrival of the conversion from 410 km implies that this discontinuity is elevated by about 20 km because the 410 km discontinuity can be elevated by the introduction of cold material our results are consistent with a model in which the lithosphere in this area developed a root during collision that later detached and is now residing near 410 km depth

hot summers in the bighorn basin during the early paleogene during the early paleogene climate in continental interiors is thought to have been warmer and more equable than today but estimates of seasonal temperature variations during this period are limited global and regional climate models of the paleogene predict cooler temperatures for continental interiors than are implied by proxy data and predict a seasonal range of temperature that is similar to today here we present a record of summer temperatures derived from carbonate clumped isotope thermometry of paleosol carbonates from paleogene deposits in the bighorn basin wyoming united states our summer temperature estimates are 18 c greater than mean annual temperature estimated from analysis of fossil leaves when coupled these two records yield a seasonal range of temperature similar to that in the region today with winter temperatures that are near freezing these data are consistent with our high resolution climate model output for the early eocene in the bighorn basin we suggest that temperatures in continental interiors during the early paleogene greenhouse were warmer in all seasons but not more equable than today if generally true this removes one of the long standing paradoxes in our understanding of terrestrial climate dynamics under greenhouse conditions

determining the diagenetic conditions of concretion formation assessing temperatures and pore waters using clumped isotopes carbonate 18 o paleothermometry is used in many diagenetic studies to unravel the thermal history of basins however this approach generally requires an assumed pore water 18 o 18 o pw value a parameter that is difficult to quantify in past regimes in addition many processes can change the original isotopic composition of pore water which further complicates the assignment of an initial 18 o pw and can lead to erroneous temperature estimates here we use clumped isotope thermometry a proxy based on the 13 c 18 o bond abundance in carbonate minerals to evaluate the temperatures of concretion formation in the miocene monterey formation and the cretaceous holz shale california these temperatures are combined with established carbonate water fractionation factors to calculate the associated 18 o pw results demonstrate that diagenetic processes can modify the 18 o of ancient pore water confounding attempts to estimate diagenetic temperatures using standard approaches clumped isotope based temperature estimates for monterey formation concretions range from 17 to 35 c up to 12 c higher than traditional 18 o carbonate water paleothermometry when 18 o pw values are assumed to equal miocene seawater values calculated 18 o pw values range from 0 3 to 2 5 vsmow higher than coeval miocene seawater likely due to 18 o pw modification accompanying diagenesis of sedimentary siliceous phases clumped isotope temperatures for the holz shale concretions range from 33 to 44 c about 15 to 30 c lower than temperatures derived using the traditional method calculated 18 o pw values range from 5 0 to 2 9 and likely reflect the influx of meteoric fluids we conclude that the use of clumped isotopes both improves the accuracy of temperature reconstructions and provides insight into the evolution of 18 o pw during diagenesis addressing a longstanding conundrum in basin evolution research

widespread cementation induced by inflow of continental water in the eastern part of the paris basin o and c isotopic study of carbonate cements abstract mesozoic limestones from the eastern part of the paris basin display mostly in strata rich in bioherms abundant macro cavities vugs and some connected micro fractures almost completely filled with euhedral calcite crystals late calcite spar the interparticle porosity of limestones is also filled with euhedral calcite spar cements similar to those observed in vugs and fractures and rarely displays the preservation of the structures typical of early marine cements these calcite spars both from vugs fractures infillings and from cemented porosity were studied in drilled cores cross cutting the kimmeridgian to bathonian series with the main objective of determining the nature and flow regime of the fluids responsible for the strong porosity reduction observed in that part of the paris basin mesozoic limestones the approach combined mineralogical and geochemical studies o and c stable isotopic compositions measured by conventional and sims methods with temperature estimates from fluid inclusion analyses the 13 c values of late calcite are close to those of the host limestones and correlate with the 13 c changes in host rocks indicating a local source of c by contrast late calcites from vugs fractures and also in the cemented interparticle porosity of limestones have 18 o values around 21 smow values which are distinct from those of bulk host limestones 25 to 27 the 18 o value of the fluid is estimated to be 6 8 to 2 5 for a crystallisation temperature between 32 and 42 c determined from fluid inclusion studies thus the parent fluid of cemented interparticle porosity and vug and fracture infillings likely contained a component of meteoric water in contrast to the previous belief that the reduction of porosity in those series was related to early marine diagenesis possible situations in which such meteoric fluid could have occurred are i a stage when the limestone aquifers were directly connected to surface water and or ii channelling of water from deeper zones in the basin through regional fault systems the o isotopic compositions of the calcite cements in the underlying 140 m thick callovo oxfordian argillites and those of the less recrystallised bathonian to kimmeridgian limestones are those expected for unmodified marine calcite 18 o ca 28 smow therefore from the isotopic point of view the callovo oxfordian argillites remained essentially unaffected by the paleo fluid circulation documented in the adjacent limestones series this indicates the argillites acted as an efficient permeability barrier in the past

gps velocity field for the tien shan and surrounding regions 1 measurements at 400 campaign style gps points and another 14 continuously recording stations in central asia define variations in their velocities both along and across the kyrgyz and neighboring parts of tien shan they show that at the longitude of kyrgyzstan the tarim basin converges with eurasia at 20 2 mm yr nearly two thirds of the total convergence rate between india and eurasia at this longitude this high rate suggests that the tien shan has grown into a major mountain range only late in the evolution of the india eurasia collision most of the convergence between tarim and eurasia within the upper crust of the tien shan presumably occurs by slip on faults on the edges of and within the belt but 1 3 mm yr of convergence is absorbed farther north at the dzungarian alatau and at a lower rate with the kazakh platform to the west the tarim basin is thrust beneath the tien shan at 4 7 mm yr with respect to eurasia the ferghana valley rotates counterclockwise at 0 7 myr 1 about an axis at the southwest end of the valley thus gps data place a bound of 4 mm yr on the rate of crustal shortening across the chatkal and neighboring ranges on the northwest margin of the ferghana valley and they limit the present day slip rate on the right lateral talas ferghana fault to less than 2 mm yr gps measurements corroborate geologic evidence indicating that the northern margin of the pamir overthrusts the alay valley and require a rate of at least 10 and possibly 15 mm yr

use of clumped isotope thermometry to constrain the crystallization temperature of diagenetic calcite we describe an approach to estimating the crystallization temperatures of diagenetic calcites using clumped isotope thermometry a paleothermometer based on the 13 c 18 o bond enrichment in carbonates application of this thermometer to calcified gastropod shells and calcite cements in an early eocene limestone from the colorado plateau reveals a record of calcite precipitation and replacement at temperatures varying from 14 to 123 c the early eocene host sediments were never deeply buried but they experienced a significant thermal pulse associated with the emplacement of a late miocene basalt flow the combination of independent constraints on thermal history with clumped isotope thermometry petrographic including cathodoluminescence observations and oxygen isotopic data provides an improved basis for estimation of the temperature and timing of diagenetic events and fluid sources the petrography and calcite 18 o values taken alone suggest that the aragonite to calcite transformation of gastropod shell material occurred simultaneously with early formation of cements and lithification of the matrix in the same sample however addition of clumped isotope thermometry demonstrates that this phase transformation of shell material occurred at temperatures of 94 123 c in a highly rock buffered microenvironment i e with the isotopic composition of fluid buffered by coexisting carbonate millions of years after lithification of the matrix and formation of initial low temperature 14 19 c calcite cements within shell body cavities clumped isotope temperatures in excess of reasonable earth surface conditions recorded by later formed cements demand that cement growth occurred in association with the lava emplacement our results illustrate the potential for clumped isotope thermometry to constrain conditions of diagenesis and guide interpretations that would not be possible on the basis of conventional stable isotopic and petrographic data alone and demonstrate how petrographic characterization of clumped isotope thermometry samples can benefit paleoclimate studies

water circulation control on carbonate δ18o records in a low permeability clay formation and surrounding limestones the upper dogger oxfordian sequence from the eastern paris basin france abstract upper dogger to oxfordian formations in the eastern part of the paris basin france are currently being investigated by the french nuclear waste management agency andra testing the feasibility of long term deep nuclear waste disposal in the callovo oxfordian claystones characterising the hydrogeological behaviour of the callovo oxfordian claystones is therefore essential in evaluating its potential as a geological barrier in order to evaluate and quantify water rock interactions experienced over geological time by these formations bulk carbonate 13 c and 18 o were measured and calculations of water rock ratios were used to explain carbonate 18 o changes meteoric porewater and a maximum temperature reached of about 40 c were considered the jurassic marine carbonate 13 c was preserved in the callovo oxfordian claystones and in the overlying limestones 0 28 to 3 39 pdb while the 18 o values are lower by 0 5 6 25 to 1 32 pdb calculations show that upper dogger and oxfordian limestone 18 o data i have random like distribution through theoretical 18 o w r curves and ii suggest that water rock ratios 0 08 0 4 needed to explain 18 o changes are higher by a factor of about 2 20 compared to the present day water rock ratio these features indicate advection in both aquifers according to the history of the paris basin this hydrogeological behaviour could have been effective since jurassic cretaceous transition times inversely the carbonate 18 o content trends observed for the callovo oxfordian data show that changes were controlled by post depositional fluid rock interaction with water rock ratio 0 02 0 15 similar to the present day porewater rock ratio the 130 m thick callovo oxfordian claystone appears remarkably homogenous regarding its hydrogeological properties this study suggests an initial marine porewater replacement by meteoric water only after porosity was reduced to its present value thus demonstrating that the callovo oxfordian clay has mainly been isolated from advective meteoric water circulation only the upper 20 m of the callovo oxfordian claystone formation underwent heterogeneous water rock exchange w r from 0 01 to 0 3 probably as a result of its mineralogical heterogeneity and proximity to the advective oxfordian limestone aquifer this study of carbonate 18 o confirms the hydrogeological barrier properties of the callovo oxfordian clay and suggests that it has been a natural hydrological barrier since the earliest times of its diagenesis

charge history of co2 in lishui sag east china sea basin evidence from quantitative raman analysis of co2 bearing fluid inclusions abstract the accumulation of carbon dioxide in natural gas reservoirs is common and co2 gas fields have been widely discovered in the world in the last decades three co2 pools were discovered in lishui sag east china sea basin geochemical proxies indicate that co2 in these gas reservoirs is dominated by mantle source volcano degassing although three volcanic events occurred in the formation of these reservoirs the co2 charging period is not clear in this study pure co2 co2 rich and h2o rich fluid inclusions were found in healed micro fractures and overgrowth zones of quartz in the reservoir of lishui sag the composition and density of two h2o rich inclusions two co2 rich inclusions and twenty three pure co2 inclusions were determined by raman quantitative analysis the burial depth of co2 fluid inclusion assemblages fia can be determined by the trapping pressure constrained from raman quantitative analysis and thermodynamic models the combination of c he isotope analyses pt entrapment conditions of co2 bearing inclusions feature of fault activity and simulation of burial history permits to assign periods of co2 fluid activity the low density 0 15 g cm 3 co2 gas inclusions recorded an early period of co2 activity eruption to be related with the late paleocene volcanic event the mid density 0 45 g cm 3 and high density 0 75 g cm 3 co2 inclusions were assigned to the miocene volcanic event and to a later co2 charging event during pliocene

basin scale thermal and fluid flow histories revealed by carbonate clumped isotopes δ47 middle jurassic carbonates of the paris basin depocentre the reconstruction of past diagenetic conditions in sedimentary basins is often under constrained this results from both the analytical challenge of performing the required analyses on the minute sample amounts available from diagenetic mineral phases and the lack of tracers for some of the diagenetic parameters the carbonate clumped isotopes thermometry 47 opens new perspectives for unravelling the temperatures of diagenetic phases together with the source of their parent fluids two parameters that are otherwise impossible to constrain in the absence of exploitable fluid inclusions here is reported the study of a large number of sedimentary and diagenetic carbonate phases from middle jurassic reservoirs of the paris basin depocentre by combining detailed petrographic observations with a large number of 47 data n 45 on a well documented paragenetic sequence including calcite and dolomite burial cements the data reveal carbonate crystallization at temperatures between 29 c and 98 c from fluids with 18owater values between 7 and 2 in response to the progressive burial and uplift of the paris basin throughout 165 myr of basin evolution coupled to the time temperature evolution previously estimated from thermal maturity modelling these temperatures allow determining the timing of four successive cementation episodes the overall dataset indicates a history of complex water mixing with a significant contribution of hypersaline waters from the triassic aquifers migrated upward along faults during the cretaceous subsidence of the basin subsequent large scale infiltrations of meteoric waters induced a dilution of these pre existing brines in response to the paris basin uplift in the tertiary overall the data presented here allow proposing an integrated approach to characterize the cementation events affecting the studied carbonate reservoir units based on temperature oxygen isotope composition and salinity of the parent fluids as well as on petrographic grounds this article is protected by copyright all rights reserved

an emerging thermochronometer for carbonate bearing rocks 47 u pb assessing the thermal evolution of sedimentary basins is critical for understanding the origin of natural resources including ores geothermal fluids or hydrocarbons and for deciphering larger scale tectonic and geodynamic evolutions modern reconstructions of past subsurface temperatures mostly rely on thermochronometers that are not applicable to carbonate rocks e g fission track and u th he analyses here by coupling carbonate clumped isotope 47 thermometry and laser ablation u pb geochronology on a complete paragenetic sequence we demonstrate the applicability of an emerging thermochronometer for carbonate bearing rocks paired 47 and u pb data were obtained for calcite and dolomite phases precipitated in a middle jurassic carbonate hydrocarbon reservoir of the paris basin depocenter france the absolute thermochronological data allow the precise reconstruction of the thermal history of these rocks from shallow burial temperatures 40 c occurring in the late jurassic toward a progressive burial and heating stage up to 87 c during the cretaceous followed by a cooling stage down to 69 c during the tertiary uplift of the basin the inferred time temperature path based on 47 u pb data is mostly consistent with the thermal scenario independently deduced from organic maturity indicators from the underlying lower jurassic shales the 47 u pb thermochronological data also highlight a thermal anomaly during aptian albian time that requires revisiting the accepted timing for hydrocarbon migration in the middle jurassic reservoir carbonates

crust and upper mantle structure beneath western china from p wave travel time tomography 1 three dimensional velocity images of the crust and upper mantle beneath western china are obtained through seismic tomography by using p wave arrival times of local regional and teleseismic events recorded in chinese and kyrgyzstan seismic networks at shallow depths most mountain belts and tectonically elevated areas are imaged as higher velocities relative to adjacent sediment filled basins and foreland depressions with lower velocities at mid lower crust depths the kyrgyz tian shan is underlain by lower velocity material and a distinct low velocity zone in the south north direction is observed between the eastern and western parts of the chinese tian shan the moho of the southern tarim basin has a greater depth over 50 km in front of the western kun lun compared to the northern and western tarim basin lateral heterogeneity within the upper mantle is apparent at depths from 71 to 571 km the uppermost mantle beneath the kyrgyz tian shan altay qi lian and eastern kun lun is characterized by low velocity material that is probably related to the upwelling of hot mantle the lithospheric thickness varies from 120 to 170 km beneath the chinese tian shan and northern tibetan plateau to 200 250 km beneath the tarim basin deep coupling pattern of the chinese tian shan with adjacent provinces can be classified into the embedding detaching and sinking and underthrusting of lithospheric roots in addition the lithosphere of the northern edge of the tibetan plateau seems to be thickened in contrast to the central part of the northern plateau north dipping low velocities exist in the upper mantle between the tibetan plateau and provinces to its north which might indicate mantle flow from the tibetan plateau toward surrounding areas but it has been blocked by the thick tarim lithosphere

atmosphere derived noble gas evidence for the preservation of ancient waters in sedimentary basins hydrological modeling of the middle jurassic carbonate aquifer of the paris basin indicated fluid residence time from 1 k y to 100 k y whereas the chemistry of waters suggested longer residence time here we report independent water age estimates on the basis of atmosphere derived noble gas recharge paleotemperatures the calculated paleotemperatures range from 15 to 26 c and are related to the stable isotope composition and the salinity of the waters and the distance from the recharge the spatial distribution of the paleotemperatures suggests 1 occurrence of old saline waters in the center of the basin which infiltrated during the warmer climate interval in the tertiary eocene and 2 dilution by recent fresh waters early pleistocene flowing from the recharge these results strongly suggest that deep aquifers in sedimentary basins can store waters for very long periods of time in contrast to the conclusions reached from hydrological modeling

three dimensional velocity structures of mount fuji and the south fossa magna central japan 1 we present the three dimensional structures of the p wave velocity vp s wave velocity vs as well as the p wave to s wave velocity ratio vp vs beneath mount fuji and the south fossa magna japan using arrival time data collected from 2002 to 2005 by a dense seismograph array the high resolution data set and improved methodology reveal not only several velocity features that are consistent with previous studies but also important new details that clarify the velocity structures associated with volcanic processes beneath mount fuji and the collision tectonics of the south fossa magna one such particular feature is a low vp low vs and low vp vs anomaly at depths of 7 17 km beneath mount fuji that corresponds with the locations of deep low frequency dlf earthquakes the coincidence of the velocity anomaly and the dlf locations suggests that supercritical volatile fluid such as h2o and co2 may be abundant in the low vp vs region and may play an important role in generating dlf earthquakes this anomaly overlies a deeper low vp low vs and high vp vs anomaly at depths of 15 25 km that may represent a zone of basaltic partial melt a low vp low vs and low vp vs anomaly is seen at depths of 6 14 km beneath mount hakone isovelocity surfaces vp 6 0 km s and vs 3 5 km s corresponding to the upper limit of hypocenter distribution below mount fuji may define the upper surface of the philippine sea plate whose existence in a seismic gap beneath mount fuji has been controversial

underplating in the himalaya tibet collision zone revealed by the hi climb experiment we studied the formation of the himalayan mountain range and the tibetan plateau by investigating their lithospheric structure using an 800 kilometer long densely spaced seismic array we have constructed an image of the crust and upper mantle beneath the himalayas and the southern tibetan plateau the image reveals in a continuous fashion the main himalayan thrust fault as it extends from a shallow depth under nepal to the mid crust under southern tibet indian crust can be traced to 31 n the crust mantle interface beneath tibet is anisotropic indicating shearing during its formation the dipping mantle fabric suggests that the indian mantle is subducting in a diffuse fashion along several evolving subparallel structures

origin of micropores in late jurassic oxfordian micrites of the eastern paris basin france porous micritic facies either primary chalks or resulting from secondary destructive micritization can constitute important hydrocarbon or water reservoirs characterization of reservoir properties and the understanding of factors which controlled the distribution of porosity are of primary interest to evaluate the prospective reserves middle and late oxfordian limestones of the eastern paris basin show several horizons with porosities higher than 20 the porosity is mainly microporous and located either within secondary micritized grains or in the micritic matrix using sem cathodoluminescence as well as confocal microscopy stable oxygen and carbon isotope ratios and petrophysical measurements a scenario for the evolution of the micropores is proposed lime mudstones to packstones constitute the majority of the high porosity facies hpfs inner lagoonal deposits are more micritized and thus more porous than grainstones and facies rich in leiolitic oncoids and echinoid clasts are less impacted by micritization micritization was responsible for an increase of the intragranular porosity in most grain types during both eogenesis and shallow burial mineralogical stabilization dissolved aragonitic particles and allowed precipitation of calcite rhombs this process was probably enhanced below surfaces of subaerial exposure during burial ostwald ripening allowed the growth of larger micrite crystals at the expense of smaller ones during early berriasian and late aptian recharges of deep aquifers when the northern margin of the basin was exposed overgrowths on micrite crystals were more important in intervals strongly affected by chemical compaction which favored oversaturation of waters with respect to calcite in low porosity horizons lpfs the dense micritic texture of oncoids and the monocrystalline architecture of echinoid clasts prevented an intense micritization while the strong chemical compaction enhanced poronecrosis telogenetic fracturing created new fluid pathways that favored inputs of meteoric fluid in porous micrite and allowed the continuation of ostwald ripening during cenozoic times as a whole mesogenetic inputs of waters undersaturated with respect to calcite in deep aquifers during exposure of basin margins are a more efficient process than early subaerial exposure for enhancing aggrading neomorphism and appearance of microporous micrites initial mineralogical heterogeneities also impact the intensity of chemical compaction and thus the stratigraphical distribution of microporous limestones

thermal evolution of tethyan surface waters during the middle late jurassic evidence from δ18o values of marine fish teeth 1 oxygen isotope compositions of phosphate from vertebrate tooth enamel were measured to determine the evolution of tropical sea surface 0 owing to limited growth of continental ice during the early middle oxfordian the resulting sea level fall is estimated to be at least 50 m and is compatible with a global regression stage the middle oxfordian thermal minimum is followed by a new warming stage of 3 4 c from the middle to the late oxfordian

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

tomographic image of the crust and upper mantle beneath the western tien shan from the manas broadband deployment possible evidence for lithospheric delamination abstract we combine teleseismic p arrival times from the recent manas deployment of broadband sensors with p and s arrival times from local events recorded by the genghis deployment and analog observations from the kyrgyz institute of seismology to generate a high resolution 20 km image of elastic wavespeeds in the crust and upper mantle beneath the western tien shan the total data set consists of 29 006 p and 21 491 s arrivals from 2176 local events recorded at 144 stations along with 5202 p arrivals from 263 teleseismic events recorded at 40 stations the most significant feature in our image of the mantle beneath the tien shan is a pair of large elongated high wavespeed regions dipping in opposite directions from the near surface to depths of at least 400 km these regions appear to be continuous and extend upwards to bounding range fronts where the tarim basin is being overthrust by the kokshal range on the south side and the kazach shield underthrusts the kyrgyz range on the north side while it is tempting to interpret these high wavespeed anomalies as evidence for contemporary subduction of continental lithosphere such a scenario is difficult to reconcile with both the timing of the orogen and the size of the wavespeed anomaly we suggest instead that they represent downwelling side limbs of a lithospheric delamination beneath the central part of the tien shan possibly by siphoning of the bordering continental lithosphere as the central part descends

aspects of hydrocarbon migration in the mesozoic in the paris basin as deduced from an organic geochemical survey abstract this paper describes the main results of a study of hydrocarbon migration in the mesozoic in the paris basin as obtained from the geochemical analysis of cuttings from 41 petroleum boreholes the analytical methods used were pyrolysis gas chromatography mass spectrometry and the determination of stable isotopes hydrocarbon formation and migration were simulated using the temispack mathematical model the following results were found concerning the primary migration pyrolysis of numerous samples of freshly cleaned cuttings allowed the computation of a migration efficiency ratio for each sample by comparing the hc contents actually produced with those remaining in the rock they also allowed the compilation of migration maps for each source rock level as indicated by the migration ratios the hc expulsion starts below the beginning of the oil window 2100 m at a depth of about 2350 m for a transformation ratio of the lias om of 25 these migration ratios increase strongly with depth reaching 88 at 2700 m migration maps served to locate the true source rocks at the base of the lias and to calculate the total quantity of oil expelled 2 billion tons of hc analysis of rock extracts from drained levels shows by comparison with the oil analyses that migration occurred without any variation in hc composition concerning the secondary migration the migration maps used to estimate the amounts of migrated hcs revealed lateral migration phenomena in some rocks toarcian with respect to the other secondary migration paths faults played an important role but failed to favor vertical downward migration by more than 50 m below the lias source rocks as shown by the temispack model the deep trias reservoirs could only be filled laterally when the faults like the bray fault placed the mature hettangian sinemurian source rocks in contact with the trias furthermore the hypotheses of a regional hydrodynamic flow trending ne sw were taken into account in the model to explain the lateral hc migrations to distances often far from their oil kitchen and the rarity of shows northeast of the bray fault

improving paleohydrological and diagenetic reconstructions in calcite veins and breccia of a sedimentary basin by combining δ47 temperature δ18owater and u pb age abstract in sedimentary basins the precise temperature and timing at which relatively shallow

calcite vein system and its importance in tracing paleowater flow and hydrocarbon migration in the ordovician carbonates of the tazhong area tarim basin china it is difficult to determine flow pathways of paleofluids in sedimentary basins petrography fluid inclusion and isotopic compositions from different phases of calcite veins in the ordovician in the tazhong area were studied our results reveal a complex diagenesis process with two importantly crossformational fluid movements coupled with three phases of calcite veins c1 c2 and c3 precipitation and thermochemical sulfate reduction by hydrocarbons fluids that precipitated c2 and c3 calcites were saline and enriched in 18o and thus may have originated from underlying evaporates whereas fluid that precipitated c3 had an additional contribution from 87sr rich ba rich and zn rich precambrian basinal clastic units fluid inclusion homogenization temperatures salinities and 18owater values of c2 veins show decreasing trends with increasing distances from strike slip faults this may indicate that c2 fluid might migrate into ordovician carbonate reservoirs through strike slip faults within 6 km during late hercynian orogeny late permian the similarly decreasing trends are observed in c3 veins indicating that the eastern part of no 1 fault seemed to be the main fluid flow pathway for c3 calcite precipitation during himalayan orogeny hydrocarbon may have migrated along the similar pathways as supported by 1 abundant primary hydrocarbon bearing fluid inclusions in the c2 and c3 calcites and 2 well documented hydrocarbon migration and mixing this is an ideal case showing how spatial variation in geochemical data from fracture fillings can be used to trace paleowater and likely hydrocarbon flows in sedimentary basins it thus may be useful in predicting fluid flow and distribution of hydrocarbons in the tarim basin and other basins

coupling δ47 and fluid inclusion thermometry on carbonate cements to precisely reconstruct the temperature salinity and δ18o of paleo groundwater in sedimentary basins abstract diagenetic minerals may provide information about the burial history of geological units and can have practical applications for instance for reconstructing the geochemical and thermal histories of sedimentary basins clumped isotope or 47 thermometry on carbonates opens a new avenue for interpreting carbonate formation temperature and thermal history of rocks yet most of current knowledge on 47 systematics has been acquired via theoretical or experimental studies with only limited validation by the rock record at geological conditions timescales here we investigate calcitic and dolomitic cements representative of three genetically different cementation phases from a well documented mineral paragenesis of a carbonate unit middle jurassic paris basin france we compare 47 with fluid inclusions microthermometry fim data that were independently obtained from the same calcite and dolomite crystal specimens the range of homogenization temperatures th found for cal1 cal2 and dol1 fluid inclusions fit remarkably well i e within 47 measurements t 47 for a temperature range between 60 and 100 c and salinities between 0 and 15 wt nacl eq this provides a consistent rock based validation of the experimentally determined 47 calibration with formation temperature for both calcite and dolomite mineralogy such findings also confirm the applicability of 47 thermometry in low temperature diagenetic environments i e below circa 100 c which provides higher precision than fim measurements i e typical uncertainties of 6 c with three 47 measurements though significantly less time consuming importantly this study underlines how the coupling of both techniques can help to evaluate the degree of preservation of the original temperature information captured by either fluid inclusions or 47 compositions and interpret each proxy as confidently accurately as possible moreover because both fim and 47 measurements can provide independent constraints on the geochemistry of diagenetic paleofluids via their salinity and 18 o composition this study also highlights the benefits of coupling both techniques to further unravel the nature of paleofuids finally we propose a practical guideline as a basis for future applications of combined fim and 47 thermometry

basin scale evolution of formation waters a diagenetic and formation water study of the triassic chaunoy formation paris basin abstract formation waters and their movements within basins are commonly attributed with responsibility for patterns of cementation and porosity loss within reservoirs and aquifers it is thus important to understand when and how waters move in the subsurface we have studied the evolution and movement of formation water in the triassic chaunoy formation of the paris basin nw europe to define the way in which the water has evolved and to interpret water movement patterns using mineral isotope and fluid inclusion data in conjunction with detailed formation water analyses the chaunoy formation is cemented with different types of dolomite calcite and quartz cement we have studied the evolution of waters in terms of oxygen carbon and strontium isotopes and salinity connate waters were meteoric in origin but strongly influenced by the proximity of a playa lake input of palaeo meteoric water which entered the chaunoy via eastern halite bodies resulted in highly saline formation water for the majority of the chaunoy formation from about 100 ma until and for some time after maximum burial saline waters spread into the aquifer initially taking a west north west trajectory and then switching to a west south west pattern in the eocene following the alpine orogeny and localised uplift of the basin margin the southern portion of chaunoy received fresh low salinity meteoric water it is likely that formation water was lost from the chaunoy in a more central part of the basin via sub vertical cross formational flow to the mid jurassic dogger formation to accommodate the influx of fresh water

teleseismic p wave tomography and the upper mantle structure of the central tien shan orogenic belt abstract in this study an updated version of the teleseismic tomographic method is applied to 7176 high quality first p wave arrivals from four combined seismic networks to determine the detailed deep structure under the central tien shan our high resolution tomographic model not only displays the general features contained in the previous models but also reveals some new features a much narrower tilted columnar high velocity anomaly with a diameter of about 60 km below 150 200 km depth under the tien shan extends down to the mantle transition zone suggesting the breaking and dropping off of the collided portions of the southward underthrusting kazakh shield and the northward underthrusting tarim basin prominent low velocity low v anomalies above 150 200 km depth beneath the tien shan may be related to two branches of ascending hot anomalies one rises upward from the lower mantle beneath the tarim basin while the other rises up from the top of the mantle transition zone beneath the western kazakh shield these results suggest that the underthrusting of the tarim basin and kazakh shield and the upwelling of hot anomalies indeed play an important role in the mountain building of the central tien shan these dynamic processes might be related to the collision of the indian plate with eurasian plate

reconstructing carbonate alteration histories in orogenic sedimentary basins xigaze forearc southern tibet abstract carbonate clumped isotope thermometry t 47 and the oxygen stable isotope record 18 o provide critical constraints on the temperature of carbonate mineral formation and isotopic composition of ancient waters used in reconstructions of past climate tectonics and ecological and environmental change the robust use of these proxies requires that carbonate minerals in the rock record retain primary isotopic compositions through often complex post depositional thermal histories new carbonate clumped isotope thermometry and sedimentology data are paired with existing thermochronology and isotope exchange reaction modeling to provide unique constraints on the alteration history of the carbon and oxygen isotopes in tethyan marine carbonates jialazi fm tso jianding group of the xigaze forearc southern tibet within the framework of the textural and isotopic data the effects of early and late burial alteration on 47 and 18 o values of marine rocks that were buried to 4 km above sea level are modeled the alteration products are considered within two well studied mechanistic frameworks water rock recrystallization and solid state reordering of 13 c 18 o bonds at high temperature the proposed alteration model is as follows 1 shallow early diagenesis with water of similar composition and temperature to formation waters infills primary porespace with microspar 2 high temperature rock buffered water rock exchange and partial solid state reordering at 3 4 km depth and 3 near surface low temperature water rock exchange on the exhumation pathway the 47 heterogeneity within individual samples 0 456 to 0 721 requires significant differential alteration on the retrograde path high to low temperature low water rock ratio in which primary compositions and compositions inherited during early burial diagenesis are overprinted with modern meteoric values a low t 47 value is often assumed to record the primary temperature of the depositional environment however samples yielding low t 47 values in the jialazi fm have undergone extensive high temperature water rock alteration and therefore require a mechanism for increasing 13 c 18 o bond ordering on the retrograde pathway while preserving many primary biogenic structures and micritic textures this study highlights the potential significance of late stage low temperature alteration of carbonates derived from orogenic sedimentary basins for studies of terrestrial paleoenvironments and tectonics this study also provides an example framework for combining observational and analytical data to reconstruct a carbonate alteration history of a buried sedimentary package

investigating the effect of burial histories on the clumped isotope thermometer an example from the green river and washakie basins wyoming abstract the 47 clumped isotope thermometer has been applied to multiple studies aimed at reconstructing the paleoelevation and paleoclimate of sedimentary basins and paleosol sequences ideally this technique directly preserves the temperature of carbonate formation avoiding any speculation on the composition of surface water from which the carbonate precipitated recently however concerns about post depositional alteration of the 47 isotope signature from the effects of burial and or diagenetic alteration have arisen potentially complicating the application of the 47 clumped isotope thermometer for determining paleo surface temperatures here we investigate the effect of burial history on mass 47 clumped isotope to this purpose we collected samples from the surface and from drill cores in two different areas of the greater green river basin the washakie basin near rock springs wyoming and the green river basin near pinedale wyoming both basins are filled with a thick sequence of eocene lacustrine strata and the thermal histories of both basins are well documented from petroleum prospecting studies clumped isotope 47 compositions were measured from lacustrine micritic limestones with a range of peak burial depths from 1 to 6 5 km for samples from the washakie basin that did not experience burial depths exceeding 2000 meters the measured 47 values vary from 0 623 to 0 684 yielding carbonate formation temperatures consistent with previously hypothesized paleocene eocene surface temperatures in contrast samples from the green river basin collected from greater burial depths demonstrate significantly lower 47 values higher temperatures the consistency of 18o values and lack of cl evidence for recrystallization suggest closed system resetting of the clumped isotope thermometer by either partial solid state re ordering or carbonate reprecipitation during burial the 47 values of the deeply buried samples have been compared to values derived from recrystallization and temperature history reordering models thrms both recrystallization and reordering models are successful at predicting 47 reordering at burial temperatures 100 c these observations from samples collected from a basin with a remarkably well constrained thermal history and geothermal gradient highlight the challenges in elucidating burial histories or diagenetic processes solely from clumped isotopic compositions

a high resolution opal and radiolarian record from the subpolar north atlantic during the mid pleistocene transition 1069 779ka palaeoceanographic implications abstract a high resolution record of radiolarian assemblages from site u1314 was studied to reconstruct hydrographic and climatic changes in the north atlantic ocean during the mid pleistocene transition period 1069 779 ka besides the faunal record absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity results show that the north atlantic arctic front shifted back and forth repeatedly at a glacial interglacial timescale bringing the site under the influence of both cold arctic glacial and much warmer atlantic interglacial waters during glacial intervals and ice rafted debris ird events the deep dwelling taxon cycladophora davisiana was the greatest contributor of the radiolarian assemblage suggesting cold surface conditions melt water discharge and changes in deep and intermediate circulation interglacial intervals were characterized by abundant shallow dwelling taxa like pseudodyctiophimus gracilipes and lithomelissa setosa increased opal accumulation and higher radiolarian diversities indicating a northward flow of warm atlantic surface waters to the site u1314 area a marked change in the structure of the radiolarian assemblage occurred after mis 22 860 ka with large taxa differences between warm and cold periods probably in response to changing ocean conditions due to the higher amplitude of glacial interglacial changes as the dominant periodicity of high latitude climate oscillations shifted from 41 kyr to 100 kyr thus we conclude that the radiolarian assemblage from the north atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial scale climatic variations that occurred in the early and mid pleistocene