contributions of diffusion dissolution ion exchange and leakage from low permeability layers to confined aquifers 1 in this paper the evolution of the groundwater chemical composition in aquifers from large sedimentary basins over geological timescale is investigated the solutes upon which we focus are sulfate chloride and sodium because they often display concentration gradients at the regional scale and they are largely undersaturated with respect to any mineral to explain these gradients several phenomena are studied leakage dissolution of minerals or ion exchange within an aquifer and dissolution of minerals or ion exchange from an overlying aquitard assuming local equilibrium the study of dissolution within the aquifer shows that the minerals containing sulfate and chloride must have been leached out rapidly after aquifer flushing and should not exist after one million years of water flow in addition a simplified model of leakage shows that dissolution of minerals embedded in an aquitard could deliver a flux of ions able to explain significant gradients within the aquifer without water transfer from aquitard to aquifer diffusion from the aquitard can also lead to significant concentration gradient along the aquifer a detailed study of ion exchange shows that the clays existing in the aquifer are rapidly thousands of years saturated with calcium and will not release sodium later on the other hand exchange from the aquitard clays followed by diffusion is able to change sodium and calcium concentrations significantly over geological time intervals in the aquifer the intensities of each process studied are compared it is shown that given the assumptions made the influence of each process can be differentiated where the aquifer aquitard system is well enough characterized analysis of aquifers with clay beds detailed in the discussion suggests that these layers may play a secondary role over geological timescales however they can lead to disconnected parts of the aquifer that can show different water chemistry our work suggests that the composition of major aquitards may have a significant effect on the chemistry of the aquifer water

transient features of the erosion of shales in the mackenzie basin canada evidences from boron isotopes abstract in order to refine our knowledge of the mechanisms that drive the weathering reactions and the rate at which elements are exported out of a shale basin we have analyzed the boron concentrations and isotopic compositions of 24 rivers contributing to the mackenzie basin canada boron has been chosen to conduct this study because of the relatively high sensitivity of its isotopic system to water rock interactions after examination of the chemical composition of the mackenzie river samples boron appears to be regulated in the largest part by reactions involving silicate rocks the other contributions of rainwaters and the dissolution of carbonate and evaporite rocks can locally control the b budget but they remain of second importance at the regional to continental scales it also appears that dissolved b in rivers is regulated by input of groundwaters the comparison between the isotopic composition of the b being exported by rivers soluble and particulates and of its bulk source indicates that it is behaving out of steady state in most of the mackenzie tributaries and particularly in rivers draining the plain a model of transport reaction is proposed in this study which demonstrates that b is controlled by rapid ion exchanges at the mineral water interface and by long term dissolution of shales the responses of the model to tested conditions reveal that the b isotopic ratio of river waters is highly sensitive to hydrological conditions and to changes of the weathering rate of shales of its partition coefficient with adsorbing surface and of the water velocity the departure of the b geochemical cycle from a steady state is interpreted as the record of changes in the weathering regime in the mackenzie basin the temporal evolution of the b cycle modeled here implies an increase of the weathering rate of shales in the mackenzie basin and or an increase of the partition coefficient between soluble b and adsorbing surfaces it also appears that these changes are consistent with timescales of the recent deglaciation of the basin this study demonstrates that the present b fluxes are actually responding to past changes of the water rock interactions and that the weathering history is a key parameter to interpret the modern geochemical fluxes this conclusion is valid for any other element that has similar chemical properties with solid surfaces

the oligo miocene qom formation iran evidence for an early burdigalian restriction of the tethyan seaway and closure of its iranian gateways in the central iranian esfahan sirjan and qom basins sedimentation of the oligo miocene qom formation took place on extensive mixed carbonate siliciclastic ramps during this time both basins were positioned at the eurasian margin of the tethyan seaway which connected the western and eastern regions of the tethys ocean at least until the late burdigalian during the so called terminal tethyan event the tethyan seaway was then closed due to the collision of the african arabian and iranian eurasian plates facies analysis of the sedimentary record of both basins indicates paleoenvironments ranging from terrestrial to open marine settings including mangrove restricted inner shelf lagoon seagrass meadow reefal and deeper offshore environments recognition of eight depositional sequences and elaboration of an integrated biostratigraphic framework calcareous nannoplankton planktic and larger benthic foraminifers gastropods and pectinids allow us to construct a basin spanning stratigraphy the assignment of the recognized sea level lowstands to the ru 3 to bur 3 lowstands of the global sea level curve enables a comparison with time equivalent sections from the zagros basin which was part of the african arabian plate on the opposing southern margin of the tethyan seaway the so calibrated sections display restrictions of the tethyan seaway and interruption of the south iranian gateways between the qom basin and the proto indopacific in relation to ongoing plate collision during the early burdigalian

boron isotope signatures in the coastal groundwaters of french guiana 1 drinking water used by the population of french guiana comes mostly from rivers and can induce major health impacts consequently groundwaters are being studied in terms of an alternative drinking water supply in this context boron isotopes were applied to the coastal aquifers to better constrain the water rock interactions we found that the 1 1 b signatures vary between 2 98 and 49 35 o in the groundwaters and between 36 35 and 42 41 o in the river waters and that the local seawater gave a value of 40 76 o we also noted an inverse correlation between groundwater ph and 1 1 b this relationship previously demonstrated experimentally is particularly well defined in the french guiana coastal aquifer because of the wide ph range 4 18 to 7 64 naturally present in the groundwaters it would appear that the variations in 1 1 b values are linked to water rock interaction processes e g dissolution precipitation of silicates

rear flank outflow dynamics and thermodynamics in the 10 june 2010 last chance colorado supercell abstracton 10 june 2010 the second verification of the origins of tornadoes experiment vortex2 armada observed a supercell thunderstorm near last chance colorado tempest unmanned aircraft system uas data collected in the rear flank outflow revealed what appeared to be an elevated outflow head turbulent wake and a cold rear flank internal surge rfis surface thermodynamic and kinematic data collected by the sticknet and mobile mesonet indicated that the outflow wake may have extended to or very near the surface perhaps modifying or outright replacing the leading edge of the outflow at times single doppler data collected by the noaa x pol mobile polarimetric doppler radar noxp were supportive of the possibility of a downdraft in the outflow wake associated with low level divergence a conceptual model of the hypothesized rear flank outflow structure in the nontornadic phase of the last chance supercell is presented the observed turbulent wake is consistent with mixing associated with the rel

the cause of internal outflow surges in a high resolution simulation of the 8 may 2003 oklahoma city tornadic supercell abstracta high resolution simulation of the 8 may 2003 oklahoma tornadic supercell is analyzed to determine the origin of internal outflow surges within the low level cold pool the analyzed simulation has 50 m horizontal grid spacing and is quadruply nested within larger lower resolution domains that were initialized via three dimensional variational data assimilation 3dvar of radar and other observations the high resolution simulation produces two tornadoes that track in close proximity to the observed tornado on 8 may 2003 the authors previous study determined that an internal outflow surge instigated tornadogenesis for the first tornado in this simulation but the cause of this internal outflow surge was unclear in this study the vertical momentum equation is analyzed along backward trajectories that are initialized within the tornado triggering internal outflow surge the analysis reveals that the internal outflow surge is forced by the dynamic part of the vertical pressure gradient further ex

using geochemical data and modelling to enhance the understanding of groundwater flow in a regional deep aquifer aquitaine basin south west of france abstract in deep aquifers the complex flow pattern originating from the geological structure often leads to difficult predictions of water origin determination of the main flow paths potential mixing of waters all these uncertainties prevent an efficient management of the resource in the context of the aquitaine basin an original modelling approach suggests that geochemical data can be used to identify flow directions where geological and hydrogeological data are too scarce to provide sufficient information in the eocene sands aquifer the major patterns of groundwater geochemistry suggest the presence of two distinct areas within the aquifer in the north and the east waters exhibit sodium bicarbonate or sodium sulphate facies and moderate total dissolved solids related to high sulphate concentrations in the south waters are characterised by calcium bicarbonate facies and low total dissolved solids sulphur isotopic ratios provided key information on the origin of sulphur in solution meteoric gypsum dissolution pyrite oxidation and also on the intensity of the geochemical processes involved in the dissolution of minerals and the concentration evolution a geochemical model was developed to analyse the processes generating the chemical composition of each sampled water at the aquifer scale four main geochemical processes dissolution redox acid base reaction exchange of varying intensity could explain most of the observed spatial variability in groundwater composition among several potential reaction schemes at each point only one allowed to reproduce the independent variables ph and 13c the developed model was used to select the most probable water pathways at the aquifer scale in this context geochemistry clearly demonstrates the role played by subsurface structures on water flow velocities and residence time in their vicinity in addition the concentrations of several ions could only be justified by the aquitard aquifer interactions

controls on the δ34s and δ18o of dissolved sulfate in the quaternary aquifers of the north china plain summary the north china plain ncp is a typical cenozoic sedimentary basin and one of the largest alluvial plains in eastern asia it consists of piedmont alluvial plain central alluvial lacustrine plain and littoral alluvial plain from west to east where quaternary aquifer systems developed in different depths groundwater from these aquifers is the most important water resource and supports a population of 200 million in the ncp currently the quaternary groundwater is depleting fast due to both human and natural factors characterizing biogeochemical processes in groundwater is central to understanding groundwater chemistry to identify the sources of dissolved sulfate so 4 2 and address subsequent biogeochemical processes in groundwater we conducted a study of spatial distributions of 34sso4 and 18oso4 in the quaternary aquifers in the northern part of the ncp the so 4 2 34sso4 and 18oso4 along the west east groundwater flowpaths in the three alluvial plains are analyzed and examined the quaternary groundwater 20 c has a so 4 2 of 37 25 177 41 mg l with so 4 2 cl ratios ranging from 0 12 to 2 79 the 34sso4 and 18oso4 range from 4 9 to 30 9 and from 4 7 to 14 0 respectively supported by other geochemical and isotopic parameters such as total dissolved solids tds concentrations d and 18o of groundwater d and 18oh2o and 14c contents in groundwater our study concludes that 1 the shallow groundwater in the piedmont area is characterized by higher so 4 2 concentration of 153 22 mg l with 34sso4 of 10 0 14 5 and 18oso4 of 4 7 9 0 whereas the groundwater in the piedmont area is characterized by lower so 4 2 concentration of 37 25 mg l with 34sso4 of 4 9 7 3 and 18oso4 of 5 8 7 5 therefore the so 4 2 in the shallow groundwater is dominated by weathered sulfate minerals from the taihang mountains and sulfate derived from oxidation of sulfides in infiltration paths whereas the so 4 2 in the deep groundwater is dominated by atmospheric sulfate from precipitation and sulfate derived from decomposition of organic matter during its recharge processes 2 dissimilatory microbial sulfate reduction dmsr occurred in the deep confined aquifers in both central and littoral plains where 34sso4 and 18oso4 increase along the groundwater flowpaths and present specific patterns for each aquifer which imply variable contributions from dmsr processes 3 the deep confined aquifer in the littoral plain has a lower dmsr rate than the other aquifers probably due to the effect of its lower permeability on physical exclusion of bacteria from the aquifer matrix this study can provide a biogeochemical background for assessing groundwater evolution and its quality in the ncp

vortex lines within low level mesocyclones obtained from pseudo dual doppler radar observations abstract vortex lines passing through the low level mesocyclone regions of six supercell thunderstorms three nontornadic three tornadic are computed from pseudo dual doppler airborne radar observations obtained during the verification of the origins of rotation in tornadoes experiment vortex in every case at least some of the vortex lines emanating from the low level mesocyclones form arches that is they extend vertically from the cyclonic vorticity maximum then turn horizontally usually toward the south or southwest and descend into a broad region of anticyclonic vertical vorticity this region of anticyclonic vorticity is the same one that has been observed almost invariably to accompany the cyclonic vorticity maximum associated with the low level mesocyclone the vorticity couplet straddles the hook echo of the supercell thunderstorm the arching of the vortex lines and the orientation of the vorticity vector along the vortex line arches compared to the orientation of the ambient barotrop

the north pyrenean aquitaine basin france evolution and hydrocarbons the mesozoic tertiary aquitaine basin overlaps the aquitaine block and the northern edge of the iberian margin both units are situated in the southwesternmost part of the european continent the aquitaine shelf is a stable platform overlying a relatively thin crustal segment it underwent extensional block faulting and many of its folded structures are related to salt tectonism the iberian block is a thicker lithospheric unit that acted as a buttress at the junction of these two structural domains the south aquitaine or north pyrenean area developed where crustal stretching rifting wrenching and orogenic compression were maximal from the mesozoic to the tertiary the history of the basin has been a suite of rifting attempts in the context of the progressive opening of the bay of biscay which never completely succeeded the relative plate motions and the later convergence led nevertheless to the formation of the aquitaine basin and to the emergence of the pyrenean fold belt the mesozoic tertiary sedimentary infill of the basin is mostly marine with thick evaporites stable platform carbonates subsiding platform shaly calcareous deposits and a characteristic diachronous turbiditic flysch and molasse complex events during the basin forming extensional and translational periods contributed more to the generation of the hydrocarbon accumulations than did the effects of the subsequent compressive structural regime the latter however may have enhanced thermal flow and thus maturation of hydrocarbon source rocks

boron concentration and isotopic composition of halite from experiments and salt lakes in the qaidam basin abstract the concentration and isotopic abundance of boron in salt can be used to trace paleosalinities and depositional environments for marine and non marine evaporites however the mechanism of incorporating boron into halite during evaporation of salt lake brines is subject to dispute and there have been few studies of boron concentrations and isotopic compositions during this process due to the low boron concentration in halite a group of evaporation experiments from artificial solutions and salt lake brines have been analyzed in this study the results of boron concentration and isotopic analyses demonstrate that the boron in halite comes mainly from fluid inclusions with a lesser amount from coprecipitation the isotopic fractionation factors between the brine and halite are from 0 9857 to 1 0000 for the evaporation experiments and 0 9945 to 1 0009 for natural samples from the salt lake the 11b values of halite from the qaidam basin salt lakes vary from 4 7 to 25 8 compared to 4 7 to 31 4 in the salt lake brines these values are controlled by the boron isotopic composition of the boron sources ph values and na ca ratios in the salt lake brines the variation of boron isotopes in halite may be used to trace the hydrochemical evolution and paleoevaporation environment in salt lakes

an example of mixed carbonate pyroclastic sedimentation miocene central basin iran abstract depositional environments of the f member of the qum formation in the central basin of iran have been reconstructed by two approaches 1 a detailed petrographic analysis of microfacies mf 2 an analysis of the vertical superposition of the microfacies using contingency tests both approaches reveal a vertical sequence of eight microfacies designated by letters a h based on petrographic characteristics and environmental significance the studied mf were interpreted in terms of depositional environments as follows mf a basin mf b lower slope mf c reef flank mf d proximal talus mf e organic reef mf f lagoon mf g restricted marine shoal mf h restricted shelf the f member carbonates were deposited in shallow water high energy conditions mostly as reef and fore reef facies carbonate deposition took place on a carbonate ramp under conditions of periodic to almost continuous influx of pyroclastic material the presence of pyroclastic material throughout the studied sections indicates that at the time of deposition an island arc volcanic complex was active nearby the absence of a wide range of typical lagoonal facies indicates that reefal facies developed as a narrow elongated strip close to the shoreline the immediate increase in depth off the reef edge prevented its seaward expansion because the volume of the produced reef talus material was insufficient to provide a shallow foundation for seaward expansion the sedimentary build up of the f member at the studied area evolved from fringing reef to barrier reef through time and space

groundwater in the broken hill region australia recognising interaction with bedrock and mineralisation using s sr and pb isotopes the supergiant pb zn ag broken hill orebody and numerous other minor mineral deposits occur within the limited outcrop of the proterozoic curnamona province of australia the vast majority of this province is concealed by up to 200 m of transported regolith hampering conventional exploration strategies approximately 300 groundwater samples were collected over the southern curnamona province to test whether this medium could be helpful in the search for hidden mineral deposits sulphur sr and pb isotope composition of the groundwaters were determined and s excess s xs i e the amount of s that can be ascribed neither to evaporation nor to mixing was calculated many samples were recognised to have undergone an addition of 34 s depleted s which can be attributed to oxidation of sulfides with a broken hill type 34 s signature average 0 v cdt furthermore sr isotopes identify the broad types of bedrock that the groundwater has been interacting with from the less radiogenic adelaidean rocks and minerals in the west groundwater 87 sr 86 sr ratio as low as 0 708 to the highly radiogenic willyama supergroup in the east 87 sr 86 sr ratio up to 0 737 the groundwaters have 207 pb 204 pb and 206 pb 204 pb ratios comparable to or intermediate between various mineralisation types recognised in the area broken hill rupee thackaringa etc types the few samples taken in the vicinity of known mineralisation yield positive indicators positive s xs low 34 s 87 sr 86 sr signature of bedrock type and pb isotope fingerprinting of mineralisation type this study also highlights several new locations under sedimentary cover where these indicators suggest interaction with mineralisation

early miocene benthic foraminifera and biostratigraphy of the qom formation deh namak central iran abstract a total of 165 samples were collected from the qom formation investigated in a stratigraphic section north of deh namak in central iran from these 35 genera and 47 species of benthic foraminifera were identified the age of the studied section is early miocene aquitanian to early burdigalian based on the occurrence of borelis melo curdica meandropsina anahensis meandropsina iranica elphidium sp 14 peneroplis farsensis and triloculina tricarinata the thickness of the qom formation is 401 m of which 161 2 m is early burdigalian in age foraminiferal assemblages in the deh namak section are referable to the borelis melo group meandropsina iranica assemblage zone and miogypsinoides archaias valvulinid assemblage zone of adams t d bourgeois f 1967 asmari biostratigraphy iranian oil operating companies geological and exploration division report1074 unpublished 1 37 described originally from the asmari formation

heterogeneities and interconnections in groundwaters coupled b li and stable isotope variations in a large aquifer system eocene sand aquifer southwestern france abstract the study of stable isotope of the water molecule and elemental data for groundwater in the large eocene sand aquifer system of sw france showed that the 18 o values of groundwater fall in the range 5 6 to 10 6 vs smow with 2 h values varying between and 34 3 to 72 3 vs smow there is no relationship between 18 o and 2 h values and the salinity but the stable isotopes data plot on or near the global meteoric water line taken as a whole the enriched samples clearly correlate with present day recharge while the most depleted samples reflect an old recharge groundwaters in the present study display large ranges of both boron concentrations 7 to 2550 g l 1 and boron isotopic compositions the lowest 11 b value being close to 18 0 and the highest one near 36 2 the scatter of b concentrations and 11 b values reflects the different rock types contributing to the supply of dissolved boron carbonates evaporites and silicates as well as an input from rainwater and fractionation during water rock interaction with clay minerals lithium concentrations in groundwater also span a wide range 0 6 to 253 g l 1 as do the lithium isotopic signatures that range between 6 5 and 28 6 we can evidence there that the b isotopic compositions are controlled by water rock interactions while li and 7 li variations are also controlled by water rock interaction processes dissolution and formation of alteration minerals that can occur at different temperatures within the groundwater system

boron sr o and h isotope geochemistry of groundwaters from mt etna sicily hydrologic implications combined b o h and sr isotopic studies of groundwaters from mt etna provide new constraints on their origin and the consequences of fluid rock interaction within this hydrologic system variations in d 18 o 29 7 to 27 2 and d d 262 to 223 mainly lie along the regional meteoric water line and suggest that most waters originated as local precipitation however small shifts in d 18 o and variable 87 sr 86 sr 0 70355 to 0 70879 and d 11 b 25 2 to 125 8 indicate that subsequent interactions occurred between the fluids and local rocks high b cl ratios in all samples seemingly preclude direct involvement of seawater in the hydrologic system despite the proximity to the coast and in some samples elevated 87 sr 86 sr and d 11 b two general end member water types are recognized on the basis of their chemistry these apparently are produced by interactions of local meteoric waters with the dominant reservoir rocks either basaltic lavas of etna or the underlying sediments respectively high d 11 b in the sediment hosted end member points to a significant marine carbonate contribution subsequent mixing between these or similar end members produced a range of intermediate composition groundwaters certain anomalous water compositions require the presence locally of a distinct component with high b and moderate d 11 b ca 110 but relatively low 87 sr 86 sr an anthropogenic source for this component is plausible one unusual sample has b and sr isotopic compositions similar to the other volcanic rock hosted waters but anomalously high cl content that likely reflects local magmatic outgassing near this sampling locality in general this study indicates that groundwater b and sr isotopic compositions are rock dominated these data provide useful constraints on the origin and evolution of groundwaters copyright 2000 elsevier science ltd

contribution of water geochemistry and isotopes δ18o δ2h 3h 87sr 86sr and δ11b to the study of groundwater flow properties and underlying bedrock structures of a deep landslide a comprehensive understanding of bedrock lithology and groundwater circulation is necessary to identify areas prone to landslide initiation and reactivation this necessity is particularly required in the case of outcroppings of weak rocks such as gypsum that due to their high solubility and low mechanical strength can promote slope deformation with the development of caves and collapses in the upper secchia river valley where gypsum outcrops extensively and is covered by landslide deposits an accurate identification of the gypsum outcrops and their distribution is needed to reduce the damage to urbanized slopes in this paper a hydrologic and geochemical approach is used in the montecagno landslide to identify the origin flow paths and transit time of groundwater circulating inside the landslide body and to identify gypsum deposits and their distribution in the bedrock the results of groundwater level monitoring 18o 2h and 3h isotope analyses and flowpc modelling suggest a local and recent origin of the groundwater hosted in shallow flow paths inside the landslide chemical and isotope 87sr 86sr 11b analyses offer evidence of the presence inside the landslide of small blocks of gypsum that due to their dimensions probably have a minor influence on landslide stability this research demonstrates that the methodology used can provide satisfactory information about bedrock structures and their hydrological aspects

boron isotopic composition of marine and nonmarine evaporite borates abstract here we present the results of the boron isotopic analysis of borates from some well known marine and nonmarine evaporite deposits combining new analyses with analyses from the literature yields a mean 11 b value for nine marine evaporite borate analyses of 25 4 permil 11 b 10 b 4 15 0 02 and a mean for twenty five nonmarine evaporite borates of 7 10 permil 11 b 10 b 4 02 0 04 previous studies have shown that the boron isotopic composition of seawater 11 b 40 permil 11 b 10 b 4 20 is about four percent heavier than the boron isotopic composition of most crustal rocks and minerals we suggest that our results for marine and nonmarine evaporite borates reflect this difference thus it should be possible to use boron isotopic composition as a tracer for boron of marine evaporitic origin applications include borate bearing evaporite deposits and perhaps borate and or borosilicate bearing metamorphic rocks

insights from the salinity origins and interconnections of aquifers in a regional scale sedimentary aquifer system adour garonne district sw france contributions of δ34s and δ18o from dissolved sulfates and the 87sr 86sr ratio abstract the multi layered eocene aquifer is a regional scale sedimentary aquifer system occupying 120 000 km 2 within the adour garonne district france local authorities have recently identified the aquifer as being at risk from extensive irrigation abstractions threatening the sustainability of this key resource because large water abstractions for human activities can significantly influence the natural functioning of such aquifer systems e g with leakage between aquifer layers which can lead to water quality degradation the characterization of such large systems constitutes a key point to protect and prevent further deterioration of aquatic ecosystems this study provides further insight on this large aquifer through a geochemical approach which addresses the limited number of groundwater wells where sampling is possible for that purpose a geochemical analysis combining two isotope systems 34 s so4 18 o so4 and 87 sr 86 sr has been applied the eocene sedimentary aquifer system detrital to carbonate deposits is made up of four aquifer layers eocene infra molassic sand early eocene middle eocene and late eocene and has a mineralized area north of the aquitaine basin where groundwater shows strong mineralization and anomalous levels of critical substances so 4 f etc increasing the difficulty of resource exploitation the extreme heterogeneity of the geochemical composition of the groundwater between the aquifers and within a single aquifer is discussed in terms of the lithological control induced by the lateral variation of facies and interconnections between aquifer layers geochemical tools especially the 34 s and 18 o from dissolved sulfates and the 87 sr 86 sr ratio suggest that evaporite dissolution both sulfate and halite is the main process controlling the high salinity levels observed in the groundwater explaining the spatial variations observed at the aquifer system scale isotopic tools also provide new information regarding the interconnections between aquifer layers supporting the hypothesis that the eocene aquifer system integrates groundwater from the oligocene miocene aquifer through leakage effects these new insights will likely help decision makers adjust their choices when managing quality problems in particular in the mineralized area of the entre deux mers where targeted groundwater wells used for drinking water display anomalous levels of critical substances

oligocene and early miocene coral faunas from iran palaeoecology and palaeobiogeography oligocene and early miocene coral assemblages from three sections of central iran are investigated with respect to their palaeoecological and palaeobiogeographic implications these corals are compared with faunas from the mediterranean tethys and the indopacific associated larger foraminifers are used for biostratigraphy and to support the palaeoecological interpretation the studied sections are situated in the foreland basins of the iranian plate which is structured into a fore arc and a back arc basin separated by a volcanic arc the coral assemblages from abadeh indicate a shallowing upward trend infrequently distributed solitary corals at the base of the section indicate a turbid environment above a distinct horizon characterised by a leptoseris stylophora assemblage associated with lepidocyclinids and planktonic foraminifers is interpreted as maximum flooding surface small patch reefs with a porites faviidae assemblage are a common feature of late oligocene to early miocene coral occurrences and indicate water depths of less than 20 m the diversity of the coral faunas shows marked differences oligocene corals from the esfahan sirjan fore arc basin comprise more than 45 species of 32 genera and occur in a wide range of environments early miocene corals from the qom back arc basin are less frequent show a lower diversity 13 genera with 15 species and occur in single horizons or small patch reefs

comment on revision of the age of the qom formation in the central iran basin iran by zhu et al journal of asian earth sciences 2007 vol 29 715 721

geochemical and boron oxygen and hydrogen isotopic constraints on the origin of salinity in groundwaters from the crystalline basement of the alpine foreland abstract the b isotopic composition in combination with o and h isotopes and hydrochemical tracers is utilized to constrain the evolution of basement hosted groundwaters via water rock interactions and fluid infiltration from external sedimentary reservoirs two distinct groundwater types have been identified in the central european crystalline basement n switzerland sw germany 1 fresh groundwaters characterized by low values of 11b 3 5 to 0 6 18o 12 0 to 10 0 and d 86 8 to 71 9 and 2 brackish groundwaters with distinctly heavier b o and h isotopic compositions 11b 6 4 to 17 6 18o 9 4 to 5 6 d 67 6 to 60 8 fresh groundwaters show a systematic decrease in 11b related to an increase in b concentrations and degree of total mineralization along the pathway of groundwater migration which can only be interpreted in terms of leaching of crystalline host rocks a 11b value of 3 3 is inferred for the crustal b source mainly hercynian granites involved in the leaching process in agreement with the known 11b range of granitic rocks the evolution of brackish groundwaters derived from crystalline basement reservoirs with little water circulation is more complex as indicated by b o h stable isotope and hydrochemical e g b cl na cl and br cl constraints brackish groundwaters from the study area are influenced by admixture of sediment derived fluids which infiltrated from late paleozoic permo carboniferous and early mesozoic lower triassic sedimentary strata the data presented show that b isotopes are sensitive to mixing processes of fluids derived from different crustal reservoirs and hence may be utilized as a tracer for constraining the internal autochthonous vs external allochthonous origin of salinity in basement hosted groundwaters

cyclic variations of sulfate and boron concentrations and isotopes in deep groundwaters in the aquitaine basin france abstract concentrations and isotope contents of major and trace elements are principal factors in determining the origin of the chemical composition of groundwater this paper focuses specifically on the use of sulfur and boron isotopes to characterize the origin of cyclic variations in the deep eocene aquifer in the aquitaine sedimentary basin southwest of france it is part of a multi layer system mainly composed of sands and sandstone deposits groundwater contained in this deep reservoir is known to present stable chemical compositions allowing its use for various purposes like drinking water geothermal energy thermal activity and agricultural irrigation however among the dozens of wells exploiting this aquifer and despite the reservoir s substantial depth variations in sulfate concentration have been identified in a limited area of the reservoir these fluctuations are cyclic and they seem to be correlated with water level variations due to gas storage activities nearby in the same aquifer regular water samplings and analyses of major and trace elements and their isotopes have identified that bore concentration variations are correlated with sulfate variations a geochemical modelling approach based on water mixes elucidates the causes of these variations in chemical composition especially the boron and sulfate concentrations and their respective 11b and 34sso4 values from these numerical results we identify that different sources explain the variations of boron concentration one part coming from the silicates alteration present in sub layers of the exploited aquifer and the other part coming from the evaporites alteration present in the underlying molasse unit these results also confirm the existence of mass and potentially water transfers between the different sub layers of the reservoir and with the underlying molasse aquitard implying new constraints for the future hydrogeologic modelling

the influence of environmental low level shear and cold pools on tornadogenesis insights from idealized simulations abstractidealized dry simulations are used to investigate the roles of environmental vertical wind shear and baroclinic vorticity generation in the development of near surface vortices in supercell like pseudostorms a cyclonically rotating updraft is produced by a stationary cylindrical heat source imposed within a horizontally homogeneous environment containing streamwise vorticity once a nearly steady state is achieved a heat sink which emulates the effects of latent cooling associated with precipitation is activated on the northeastern flank of the updraft at low levels cool outflow emanating from the heat sink spreads beneath the updraft and leads to the development of near surface vertical vorticity via the baroclinic mechanism as has been diagnosed or inferred in actual supercells that have been simulated and observed an intense cyclonic vortex forms in the simulations in which the environmental low level wind shear is strong and the heat sink is of intermediate strength relative to the