late miocene to pliocene palaeogeography of the paratethys and its relation to the mediterranean abstract the palaeogeographic evolution of the paratethyan and mediterranean realms are reconstructed with three maps ranging from the late miocene to the middle late pliocene the maps are based on the facial analysis of selected deposits clastic input slope slide process analyses as well as biogeographic data of the planktic benthic and terrestrial biota characteristic fossil assemblages are used for palaeobathymetric and palaeohydrologic interpretations restoration of palaeogeographic connections the palaeogeographic reconstructions are palinspastically restored after dercourt j ricou l e vrielynck b eds 1993 atlas tethys palaeoenvironmental maps gauthier villars paris pp 1 307 14 maps the paleogeographic atlas of northern eurasia 1997 inst tectonics lithospheric plates moscow 26 maps with modifications maps have been prepared for the terminal tortonian early messinian late pannonian early maeotian late messinian pontian salinity crisis time and piacenzian gelasian akchagilian they illustrate the neogene palaeogeographic evolution during and after the attic orogenesis though the emerging mountain system of the alpine foldbelt increasingly separated the paratethys from the mediterranean tethys paratethys connections remained extant and sufficiently effective for limited communication between both basins they governed many features of the cyclic depositional history and biogeographic evolution of the eastern paratethys

identification of hydrogeochemical zones in postglacial buried valley aquifer wielkopolska buried valley aquifer poland this article presents the difficulty in identifying the hydrochemical zoning of a semi confined aquifer characterised by a relative small spatial differentiation of groundwater chemistry it is shown that multivariate statistical methods can be used for the recognition and interpretation of the groundwater chemistry distribution in an aquifer the hydrochemical zonation caused by both natural and anthropogenic processes was identified using factor analyses in combination with a classical interpretation of the hydrogeological material the interpretation of the groundwater chemistry allows both identification of the aquifer recharge mechanism and verification of the groundwater flow system

hydrochemistry and isotopic composition of na hco3 rich groundwaters from the ballimore region central new south wales australia abstract groundwaters flowing under artesian pressure from the ballimore region central new south wales australia contain up to 95 na hco3 carbon dioxide effervesces from these groundwaters as they discharge from boreholes these groundwaters flow from a confined aquifer situated within fractured permian to jurassic sediments regional geological data and k ar dating of outcropping volcanic units indicate that magmatism occurred in this area between 12 and 14 ma ago radiometric and magnetic data supports the interpreted presence of intrusive bodies x ray fluorescence xrf data shows that the miocene magmatic units are sodium rich with the available samples being classified as either syenitic or trachytic hydrochemical and isotopic data indicate that these groundwaters are of meteoric origin and that this system is open with respect to co2 there is an external source of co2 feeding this groundwater system causing dic total alk the salinity of the na hco3 rich groundwaters range from 3000 to 8000 mg l and co2 aq concentrations are up to 1558 mg l log pco2 of 0 6 the ph of these samples range from 6 1 to 6 9 supporting the conclusion that the h2co3 hco3 couple control ph buffering the carbon 13 values 13c pdb of 5 to 3 indicate that the carbon source for these groundwaters is of inorganic origin it is inferred that this carbon source has a primary 13c similar to that typically quoted for mantle derived carbon 5 9 varying degrees of completeness of equilibrium isotopic fractionation resulting from the hydration dissociation of co2 into the groundwater forming hco3 co2 h2co3 hco3 leads to the observed range of carbon 13 data oxygen 18 18o smow and deuterium d smow isotopic data show a shift to the left of the meteoric water line supporting an interpretation of co2 exsolution gas exchange and fractionation resulting from incongruent silicate weathering reactions dissolved inorganic carbon carbon 13 and regional geological data suggest that the most plausible explanation for the high concentration of co2 in these effervescent sodium bicarbonate rich groundwaters is the mantle with this gas initially being delivered to the fractured strata by magmatic activity

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

middle to late miocene oxygen isotope stratigraphy of odp site 1085 se atlantic new constrains on miocene climate variability and sea level fluctuations abstract the middle miocene 18o increase represents a fundamental change in earth s climate system due to a major expansion and permanent establishment of the east antarctic ice sheet accompanied by some effect of deepwater cooling the long term cooling trend in the middle to late miocene was superimposed by several punctuated periods of glaciations mi events characterized by oxygen isotopic shifts that have been related to the waxing and waning of the antarctic ice sheet and bottom water cooling here we present a high resolution benthic stable oxygen isotope record from odp site 1085 located at the southwestern african continental margin that provides a detailed chronology for the middle to late miocene 13 9 7 3 ma climate transition in the eastern south atlantic a composite fe intensity record obtained by xrf core scanning odp sites 1085 and 1087 was used to construct an astronomically calibrated chronology based on orbital tuning the oxygen isotope data exhibit four distinct 18o excursions which have astronomical ages of 13 8 13 2 11 7 and 10 4 ma and correspond to the mi3 mi4 mi5 and mi6 events a global climate record was extracted from the oxygen isotopic composition both long and short term variabilities in the climate record are discussed in terms of sea level and deep water temperature changes the oxygen isotope data support a causal link between sequence boundaries traced from the shelf and glacioeustatic changes due to ice sheet growth spectral analysis of the benthic 18o record shows strong power in the 400 kyr and 100 kyr bands documenting a paleoceanographic response to eccentricity modulated variations in precession a spectral peak around 180 kyr might be related to the asymmetry of the obliquity cycle indicating that the response of the dominantly unipolar antarctic ice sheet to obliquity induced variations probably controlled the middle to late miocene climate system maxima in the 18o record interpreted as glacial periods correspond to minima in 100 kyr eccentricity cycle and minima in the 174 kyr obliquity modulation strong middle to late miocene glacial events are associated with 400 kyr eccentricity minima and obliquity modulation minima thus fluctuations in the amplitude of obliquity and eccentricity seem to be the driving force for the middle to late miocene climate variability

final closure of panama and the onset of northern hemisphere glaciation abstract the greenland ice sheet is accepted as a key factor controlling the quaternary glacial scenario however the origin and mechanisms of major arctic glaciation starting at 3 15 ma and culminating at 2 74 ma are still controversial for this phase of intense cooling ravelo et al 1 a c ravelo d h andreasen m lyle a o lyle m w wara regional climate shifts caused by gradual global cooling in the pliocene epoch nature 429 2004 263 267 proposed a complex gradual forcing mechanism in contrast our new submillennial scale paleoceanographic records from the pliocene north atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation nhg since it was linked to a 2 3 c surface water warming during warm stages from 2 95 to 2 82 ma these records support previous models g h haug r tiedemann effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation nature 393 1998 673 676 2 claiming that the final closure of the panama isthmus 3 0 2 5 ma j groeneveld s steph r tiedemann d nurnberg d garbe schonberg the final closure of the central american seaway geology in prep 3 induced an increased poleward salt and heat transport associated strengthening of north atlantic thermohaline circulation and in turn an intensified moisture supply to northern high latitudes resulted in the build up of nhg finally culminating in the great irreversible climate crash at marine isotope stage g6 2 74 ma in summary there was a two step threshold mechanism that marked the onset of nhg with glacial to interglacial cycles quasi persistent until today

closing of the central american seaway and the ice age a critical review 1 what role did the closing of the central american seaway play in enabling continental ice sheets to wax and wane over north america and fennoscandia a summary of relevant evidence presented here permits a causal relationship between them but can be interpreted to show none the common denominator of such evidence is the approximate simultaneity of that closing with global cooling and the first major ice advance at the resolution of paleoclimate however geologic evidence from central america places only weak constraints on when interchange between pacific and caribbean water ceased the strongest evidence for when north and south america became connected by a continuous land bridge the great american exchange of vertebrates assigns climate change the causal role for an arid central american climate typical of glacial times seems necessary for animals that inhabited savannas to pass through panama paleoceanographic and geochemical studies of environments and water masses in the eastern pacific western caribbean and atlantic in general call for continual change since 6 ma or earlier if evidence concurrent with global change near 3 5 3 ma seems more widespread than for other times hypothesized connections between a closed seaway and glaciation commonly call for profoundly different north atlantic ocean circulation but simulations using general circulation models provide a spectrum of differences in circulation for open and closed seaways might much not all of the evidence implicating the closing of the seaway in global climate change in fact be a consequence of that change and blind to central america s tectonic development

paleotemperatures and ice volume of the past 27 myr revisited with paired mg ca and 18o 16o measurements on benthic foraminifera 1 we explore the applicability of paired mg ca and 18o 16o measurements on benthic foraminifera from southern ocean site 747 to paleoceanographic reconstructions on pre pleistocene timescales we focus on the late oligocene through pleistocene 27 0 ma history of paleotemperatures and the evolution of the 18o values of seawater 18osw at a temporal resolution of 100 200 kyr absolute paleotemperature estimates depend on assumptions of how mg ca ratios of seawater have changed over the past 27 myr but relative changes that occur on geologically brief timescales are robust results indicate that at the oligocene to miocene boundary 23 8 ma temperatures lag the increase in global ice volume deduced from benthic foraminiferal 18o values but the smaller scale miocene glaciations are accompanied by ocean cooling of 1 c during the mid miocene phase of antarctic ice sheet growth 15 13 ma water temperatures cool by 3 c unlike the benthic foraminiferal 18o values which remain relatively constant thereafter temperatures vary by 3 c and reach maxima at 12 and 8 5 ma the onset of significant northern hemisphere glaciation during the late pliocene is synchronous with an 4 c cooling at site 747 a comparison of our 18osw curve to the haq et al 1987 sea level curve yields excellent agreement between sequence boundaries and times of increasing seawater 18o 16o ratios at 12 11 ma in particular when benthic foraminiferal 18o values do not support a further increase in ice volume the 18osw curve comes to a maximum that corresponds to a major mid miocene sea level regression the agreement between the character of our mg ca based 18osw curve and sequence stratigraphy demonstrates that benthic foramaniferal mg ca ratios can be used to trace the 18osw on pre pleistocene timescales despite a number of uncertainties related to poorly constrained temperature calibrations and paleoseawater mg ca ratios the mg ca record also highlights that deep ocean temperatures can vary independently and unexpectedly from ice volume changes which can lead to misinterpretations of the 18o record

a coastal upwelling seesaw in the atlantic ocean as a result of the closure of the central american seaway 1 based on coupled climate model experiments we suggest an antiphase relationship between the two major coastal upwelling zones in the atlantic ocean off northwestern and southwestern africa we describe this as an upwelling seesaw the state of the coastal upwelling seesaw is controlled by variations in the oceanic meridional heat transfer between south and north atlantic in particular we suggest that the pliocene closure of the central american seaway induced a large scale redistribution of heat in the atlantic ocean leading to an intensification weakening of upwelling off southwest northwest africa

proterozoic zircon from augen gneiss yukon tanana upland east central alaska u th pb analyses of zircons from an ortho augen gneiss body in the yukon tanana upland of east central alaska yield strong evidence for the presence of early proterozoic material in this area u pb data define a chord that intersects concordia at about 2 300 and 345 m y we consider two interpretations 1 the protolith was intruded during the proterozoic and was subsequently metamorphosed in the paleozoic or more likely 2 the protolith was intruded in the paleozoic and incorporated material of proterozoic age an sm nd model age of about 1 900 m y on a whole rock sample of augen gneiss is additional evidence for the presence of proterozoic material in the gneiss k ar and u th pb dating of mica and sphene respectively reveal that younger thermal events occurred at least as recently as 110 m y ago

hydrogeochemical characterization and isotope investigations of a carbonate aquifer of the northern part of the united arab emirates abstract this paper assesses a carbonate aquifer of the wadi al bih area in the northeastern part of uae using hydrogeochemical and isotope approaches analyses of groundwater samples showed that the tds and high concentrations of major cations and anions were encountered in the lower segment of the wadi al bih area most of the groundwater salinity was noticed downstream of the wadi and this may be attributed to the brines that underlie the groundwater and also to the over pumping of groundwater with mostly very low recharge nitrate concentrations observed in the groundwater of the study area may be ascribed to the nature of the karastic aquifer which could lead to the dominance of dissolved oxygen that makes no 3 the dominant form of nitrogen the presence of sulfate in collected groundwater samples is due to the gypsum bearing mudstone in the lower segment of the wadi al bih carbonate aquifer majority of the groundwater samples showed the presence of nacl which indicates the possible influence of the underlying brine the mixing process of brine water and freshwater was noted in the shift from cahco 3 facies to ca cl facies the piper plot showed a ca rich to na rich water type shift which could be explained by a cation exchange process the oxygen and hydrogen isotope compositions in the groundwater samples suggest that the main source of precipitation is the mediterranean sea with some possible effects of the arabian sea a trend of increasing chloride concentration with enrichment of hydrogen isotope compositions suggests that groundwater originated from evaporated raindrops or evaporated surface water the similarity of oxygen and hydrogen isotope compositions between the eastern gravel plain ophiolite and the northern carbonate aquifers indicates the presence of a common source of recharge

control of north atlantic deep water circulation by the greenland scotland ridge coherent bathymetric features along the reykjanes ridge indicate that there were significant changes in the flux of buoyant material within the icelandic hot spot during the neogene the radial extent of the topographic swell associated with this hot spot is of the order of 1000 to 2000 km and therefore these changes affected the greenland scotland ridge gsr at present sill depths along the gsr are generally less than 500 m with the deepest passage being less than 1000 m making the overflow water sensitive to even small changes in the ridge depths reconstructions of neogene mantle plume activity correlate with the deepwater circulation patterns in the north atlantic times of high mantle plume activity caused northern component water ncw production to cease ncw fluxes resumed once this phase of high mantle plume activity slowed the long term climate change during the neogene must be controlled by factors other than ncw production however climatic optima during the late early miocene and early pliocene appear to have been augmented by high ncw fluxes while subsequent middle miocene and middle pliocene coolings correlate with uplifts on the gsr and reduced ncw flux we suggest that reductions in ncw may have contributed to both of these cooling events

the formation of shallow fresh groundwater in the north of yanchi county ningxia china main influencing factors and mechanism shallow fresh groundwater is not common in the middle of basins in arid and semiarid areas with strong evaporation where shallow groundwater is often brackish water or saline water in this study the shallow fresh groundwater in the north area of yanchi county china was investigated for the main influencing factors and mechanisms of its formation the results showed that freshwater of hco3 and so4 types with mean salinity of 0 78 g l formed in the north of the study area while brackish and saline water of so4 cl na type with mean salinity of 2 28 g l formed in the west and south of the study area the fresh groundwater formed owing to the special physico chemical properties of the aeolian sand which has the good permeation of atmospheric precipitation the weak evaporation of the groundwater the low salt contents in the vadose zone and aquifer medium the weak water rock interaction and the good hydrodynamic condition the lateral recharge of low salinity groundwater also played a mixing and diluting role in the formation of the fresh groundwater the findings should provide a scientific basis for the exploitation and utilization of local groundwater resources and be of significance in the exploration and exploitation of fresh groundwater in arid and semiarid regions

neogene overflow of northern component water at the greenland scotland ridge in the north atlantic ocean flow of north atlantic deep water nadw and of its ancient counterpart northern component water ncw across the greenland scotland ridge gsr is thought to have played an important role in ocean circulation over the last 60 ma the iceland plume has dynamically supported an area which encompasses the gsr consequently bathymetry of the gsr has varied with time due to a combination of lithospheric plate cooling and fluctuations in the temperature and buoyancy within the underlying convecting mantle here we reassess the importance of plate cooling and convective control on this northern gateway for ncw flow during the neogene period following wright and miller 1996 to tackle the problem benthic foraminiferal isotope data sets have been assembled to examine 13c gradients between the three major deep water masses i e northern component water southern ocean water and pacific ocean water composite records are reported on an astronomical timescale and a nonparametric curve fitting technique is used to produce regional estimates of 13c for each water mass confidence bands were calculated and error propagation techniques used to estimate ncw and its uncertainty despite obvious reservations about using long term variations of 13c from disparate analyses and settings and despite considerable uncertainties in our understanding of ancient oceanic transport pathways the variation of ncw through time is consistent with independent estimates of the temporal variation of dynamical support associated with the iceland plume prior to 12 ma 13c patterns overlap and ncw cannot be isolated significant long period variations are evident which are consistent with previously published work from 12 ma when lithospheric cooling probably caused the gsr to submerge completely long period 13c patterns diverge significantly and allow reasonable ncw estimates to be made our most robust result is a dramatic increase in ncw overflow between 6 and 2 ma when dynamical support generated by the iceland plume was weakest between 6 and 12 ma a series of variations in ncw overflow have been resolved

the effect of a confining unit on the geochemical evolution of ground water in the upper floridan aquifer system in west central florida sections of the upper floridan aquifer system range in character from confined to leaky to unconfined the confining unit is the hawthorn formation a clay rich sequence the presence or absence of the hawthorn formation affects the geochemical evolution of the ground water in the upper floridan aquifer system mass balance and mass transfer models suggest that in unconfined areas the geochemical reactions are dolomite dissolution ion exchange mg for na k sulfate reduction calcite dissolution and co2 exchange in the areas in which the hawthorn formation is leaky the evolution of the ground water is accounted for by ion exchange sulfate reduction calcite dissolution and co2 exchange in the confined areas no ion exchange and only limited sulfate reduction occur and the chemical character of the ground water is consistent with dolomite and gypsum dissolution calcite precipitation and co2 ingassing the hawthorn formation acts both as a physical barrier to the transport of co2 and organic matter and as a source of ion exchange sites but the carbonate mineral reactions are largely unaffected by the extent of confinement of the upper floridan aquifer

geochemical modeling of the madison aquifer in parts of montana wyoming and south dakota stable isotope data for dissolved carbonate sulfate and sulfide are combined with water compo sition data to construct geochemical reaction models along eight flow paths in the madison aquifer in parts of wyoming montana and south dakota the sulfur isotope data are treated as an isotope dilution problem whereas the carbon isotope data are treated as rayleigh distillations all reaction models reproduce the observed chemical and carbon and sulfur isotopic composition of the final waters and are partially validated by predicting the observed carbon and sulfur isotopic compositions of dolomite and anhydrite from the madison limestone the geochemical reaction models indicate that the dominant groundwater reaction in the madison aquifer is dedolomitization calcite precipita tion and dolomite dissolution driven by anhydrite dissolution sulfate reduction ca mg2 ina cation exchange and halite dissolution are locally important particularly in central montana the groundwater system is treated as closed to c02 gas from external sources such as the soil zone or cross formational leakage but open to c02 from oxidation of organic matter coupled with sulfate reduction and other redox processes occurring within the aquifer the computed mineral mass transfers and modeled sulfur isotopic composition of madison anhydrites are mapped throughout the study area carbon 14 groundwater ages adjusted for the modeled carbon mass transfer range from modem to about 23 000 years b p and indicate flow velocities of 7 7 ftlyr 2 1 26 5 rnlyr most horizontal hydraulic conductivities calculated from darcy s law using the average 14 c flow velocities are within a factor of 5 of those based on digital simulation the calculated mineral mass transfer and adjusted 14 c groundwater ages permit determination of apparent rates of reaction in the aquifer the apparent rate of organic matter oxidation is typically 0 12 jlidol uyr sulfate and to a lesser extent ferric iron are the predominant electron acceptors the kinetic biochemical fractionation of 34 s between sulfate and hydrogen sulfide is approximately 44 o at 25 c with a temperature variation of

late miocene washhouse climate in europe abstract we present two eight million year long proxy records of precipitation for southwest and central europe covering the middle to late miocene 5 3 13 ma at a temporal resolution of about 60 kyr and 150 kyr respectively the estimates of precipitation are based on the ecophysiological structure of herpetological assemblages amphibians and reptiles from 13 0 ma until about 9 ma both records show a similar trend evolving from a long dry period 13 11 ma into a washhouse climate 10 2 9 8 ma characterized by global warm conditions and several times more precipitation than present the transition from washhouse to a dryer climate between 9 7 and 9 5 ma and the concomitant cooling episode appear to have triggered a severe biotic event known as the vallesian crisis which included the extinction of hominoids in western europe a second washhouse period 9 0 8 5 ma coeval with a global warm episode was unprecedentedly intense in southwest europe but less pronounced in central europe from 8 ma onward a divergence in the two precipitation records is observed with southwest europe staying wetter and central europe becoming dryer than present both precipitation records are combined into a common run off curve as a measure of the relative intensity of the hydrological cycle for moderate latitudes of continental europe the run off curve shows a remarkable positive correlation with atlantic deep water temperatures from ceara rise by lear et al 2003 which are significantly higher up to 3 c during the two washhouse periods and show no other positive excursion of comparable magnitude we discuss potential links and the role of the coeval temporary restriction of the central american seaway on ocean and atmosphere circulation

middle to late miocene fluctuations in the incipient benguela upwelling system revealed by calcareous nannofossil assemblages odp site 1085a middle to late miocene calcareous nannofossil data of odp site 1085 from the eastern south atlantic off namibia were analysed to document spatial and temporal changes in surface ocean circulation upwelling initiation and associated productivity our data show that calcareous nannofossils constitute a significant part of the carbonate fraction throughout the investigated interval from 12 5 to 7 7 million years ma highest numbers of calcareous nannofossils up to 38 000 10 6 nannofossils g 1 sediment were observed during the intervals 9 9 to 9 7 and 8 7 to 8 0 ma these elevated numbers of calcareous nannofossils may generally be linked to the initiation of upwelling at about 10 ma in the studied region in contrast diminished numbers of calcareous nannoplankton as in the interval 9 6 to 9 0 ma probably characterise time intervals of weaker productivity resulting in a decrease of nannofossil carbonate contents in the sediments of site 1085 this decrease in nannofossil production could be one possible explanation for the major caco3 depression in between 9 6 and 9 0 ma coccoliths of the genus reticulofenestra are the most abundant taxa their occurrences are characterised by changes in the investigated time interval in addition coccolithus pelagicus calcidiscus leptoporus and umbilicosphaera spp contribute a common part of the assemblage calcareous nannofossils account for more than half of the carbonate with peak contribution up to 80 at 8 8 ma d 2005 elsevier b v all rights reserved

isotopic paleoceanography of the caribbean and east pacific role of panama uplift in late neogene time comparisons of carbon isotopic data on benthic foraminifera from deep sea drilling project sites 502 western caribbean and 503 eastern pacific indicate that the difference between the atlantic and the pacific in the per mil enrichment in carbon 13 of total dissolved carbon dioxide increased about 6 million years ago and again 3 million years ago when the difference reached the modern level 1 per mil comparisons of planktonic foraminiferal oxygen isotopic data for the caribbean and the pacific suggest that the salinity of caribbean surface waters began increasing 4 million years ago possibly in response to shoaling of the panama isthmus these results suggest that modern circulation patterns in the caribbean and eastern pacific developed by 3 million years ago in concert with changing tectonic climatic and biogeographic patterns

the closing of a seaway ocean water masses and global climate change the late neogene witnessed various major paleoceanographic changes that culminated in intense northern hemisphere glaciation nhg the cause and effects of these changes are still debated we use a multiproxy approach to determine the relative timing of the closure of the panama gateway changes in atlantic circulation global cooling and ice sheet growth benthic foraminiferal mg ca records from a pacific and an atlantic site have been produced and are interpreted in terms of bottom water temperatures these mg temperature records are combined with published benthic 13c 18o and erosion records to reconstruct the flow of proto north atlantic deep water proto nadw over the past 12 ma the results suggest that between 12 5 and 10 5 ma and again between about 8 5 and 6 ma a nutrient depleted water mass that was colder by 1 2 c and fresher than the intervening deep water mass filled the atlantic basin this proto nadw became warmer by 1 c and saltier between 6 and 5 ma coincident with the restriction of surface water flow through the central american seaway the mg temperature records define a subsequent global cooling trend of 3 5 c between 5 ma and today early nhg in the late miocene was perhaps related to the formation of the relatively cold fresh proto nadw the formation of the warmer and saltier proto nadw in the early pliocene may have initially limited northern hemisphere ice growth however the increased moisture released at high northern latitudes associated with formation of warm proto nadw coupled with the global temperature decrease of deep and hence polar surface waters likely helped initiate the intense nhg of the plio pleistocene

new method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late miocene precipitation gradients in europe existing methods for determining paleoprecipitation are subject to large errors 6350 400 mm or more using mammalian proxies or are restricted to wet climate systems due to their strong facies dependence paleobotanical proxies here we describe a new paleo precipitation tool based on an indexing of ecophysiological groups within herpetological communities in recent communities these indices show a highly significant correlation to annual precipitation r 2 5 0 88 and yield paleoprecipitation estimates with average errors of 6250 280 mm the approach was validated by comparison with published paleopre cipitation estimates from other methods the method expands the application of paleo precipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database this method is applied to two high resolution time intervals from the european neogene the early middle miocene early langhian and the early late miocene early tortonian the results indicate that both periods show significant meridional precipitation gradients in europe these being stronger in the early langhian threefold decrease toward the south than in the early tortonian twofold decrease toward the south this pattern indicates a strengthening of climatic belts during the middle miocene climatic optimum due to southern hemisphere cooling and an increased contribution of arctic low pressure cells to the precipitation from the late miocene onward due to northern hemisphere cooling

hydro geochemical processes in an area with saline groundwater in lower shire river valley malawi an integrated application of hierarchical cluster and principal component analyses abstract our ability to adapt to changes in groundwater quality arising from a changing climate and or local pressures is dependent on comprehension of the governing controls of spatial variation in groundwater chemistry this paper presents results of an assessment of dominant hydro geochemical processes controlling groundwater chemical composition using an integrated application of hierarchical cluster analysis hca and principal component analysis pca of a major ion dataset of groundwater from lower shire river valley malawi the area is in the southernmost part of the western section of the east african rift system ears and has localised occurrence of saline groundwater hca classified samples into three main clusters c1 c3 according to their dominant chemical composition c1 dominant composition na cl median tds 3436 mg l 1 c2 dominant composition na hco 3 median tds 966 mg l 1 and c3 dominant composition alkali earths hco 3 median tds 528 mg l 1 these clusters were in turn described by the principal components pc1 pc3 and pc2 respectively resulting from the pca the results of the pca and geochemical interpretation suggest that the spatial variation of groundwater quality in the area is influenced by the following processes c3 samples result mainly from h 2 co 3 weathering of aluminosilicate minerals by percolating water supersaturated with co 2 in addition to aluminosilicate weathering c2 samples are influenced by the processes of cation exchange of ca 2 and mg 2 in the water for na on clay minerals and carbonate precipitation the increase in ionic strength of c2 samples is attributed to mixing with high tds groundwater in proximity with c2 samples the saline brackish c1 groundwater results from the processes of evaporation for samples with high water table close to the shire marshes and dissolution of cl and so 4 evaporative salts followed by mineralised seep from sedimentary karoo and cretaceous lupata sandstones

north atlantic deep water export to the southern ocean over the past 14 myr evidence from nd and pb isotopes in ferromanganese crusts the intensity of north atlantic deep water nadw production has been one of the most important parameters controlling the global thermohaline ocean circulation system and climate here we present a new approach to reconstruct the overall strength of nadw export from the north atlantic to the southern ocean over the past 14 myr applying the deep water nd and pb isotope composition as recorded by ferromanganese crusts and nodules we present the first long term nd and pb isotope time series for deep southern ocean water masses which are compared with previously published time series for nadw from the nw atlantic ocean these data suggest a continuous and strong export of nadw or a precursor of it into the southern ocean between 14 and 3 ma an increasing difference in nd and pb isotope compositions between the nw atlantic and the southern ocean over the past 3 myr gives evidence for a progressive overall reduction of nadw export since the onset of northern hemisphere glaciation nhg the nd isotope data allow us to assess at least semiquantitatively that the amount of this reduction has been in the range between 14 and 37 depending on location

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

late miocene climate in the circum alpine realm a quantitative analysis of terrestrial palaeofloras abstract selected mega and microfloras from central and southern europe have been analysed for the time interval tortonian pannonian mn 9 12 with the coexistence approach to obtain quantitative palaeoclimate data the results give a geographically differentiated picture of the late miocene climate in the circum alpine area spatial patterns are presented in maps for mean annual temperature temperature of the coldest month temperature of the warmest month mean annual precipitation and mean annual range of temperature the obtained data show an overall warm humid and homogenous climate with very low latitudinal and longitudinal gradients there is no indication of a mediterranean type of climate palaeogeographic influences on climate patterns are evident the pannonian lake caused mild winters and a lower seasonality of temperature in the pannonian basin

identification of indicators of groundwater quality formation process using a zoning model summary drinking water safety is a world wide focus in yinchuan plain of western china groundwater is mostly saline water and it has generated many problems for the life of local residents yinchuan plain exhibits differences from the mountain area to the plain in terrain and elevation and landforms and scales such differences resulted in hydro geological water storage structures with different water yield properties and permeabilities of the aquifers these water storage structures are the places where the groundwater moves and is retained as well as where the air water rock interaction and the migration and differentiation between substances in the water take place with the arid climate and intense irrigation in yinchuan plain the hydro chemical features of the groundwater exhibit distinct zonation to explore the formative mechanism of the groundwater quality in yinchuan plain a zoning model for the formation of groundwater quality is established in three layers the first layer shows the geological and hydrogeological conditions that express the landform and landscape geological age lithology and hydrodynamic features of the studied area the second layer indicates the zonation of the formation of groundwater quality according to the major hydro geochemical actions the plain is divided from west to east into lixiviation evaporation and evaporation mixing zones the third layer contains the hydrodynamic features that express the hydro chemical type salinity and the contents of the major ions as well as trace elements fluorine and arsenic the features of each zone are quantitatively expressed with thermodynamic hydrodynamic and hydro chemical indicators