constant elevation of southern tibet over the past 15 million years the uplift of the tibetan plateau an area that is 2 000 km wide to an altitude of about 5 000 m has been shown to modify global climate and to influence monsoon intensity mechanical and thermal models for homogeneous thickening of the lithosphere make specific predictions about uplift rates of the tibetan plateau but the precise history of the uplift of the plateau has yet to be confirmed by observations here we present well preserved fossil leaf assemblages from the namling basin southern tibet dated to approximately 15 myr ago which allow us to reconstruct the temperatures within the basin at that time using a numerical general circulation model to estimate moist static energy at the location of the fossil leaves we reconstruct the elevation of the namling basin 15 myr ago to be 4 689 895 m or 4 638 847 m depending on the reference data used this is comparable to the present day altitude of 4 600 m we conclude that the elevation of the southern tibetan plateau probably has remained unchanged for the past 15 myr

model based analysis of δ34s signatures to trace sedimentary pyrite oxidation during managed aquifer recharge in a heterogeneous aquifer the oxidation of pyrite is often one of the main drivers affecting groundwater quality during managed aquifer recharge in deep aquifers data and techniques that allow detailed identification and quantification of pyrite oxidation are therefore crucial for assessing and predicting the adverse water quality changes that may be associated with this process in this study we explore the benefits of combining stable sulphur isotope analysis with reactive transport modelling to improve the identification and characterisation of pyrite oxidation during an aquifer storage and recovery experiment in a chemically and physically heterogeneous aquifer we characterise the stable sulphur isotope signal 34s in both the ambient groundwater and the injectant as well as its spatial distribution within the sedimentary sulphur species the identified stable sulphur isotope signal for pyrite was found to vary between 32 and 34 while the signal of the injectant ranged between 9 06 and 14 45 during the injection phase of the experiment both isotope and hydrochemical data together suggest a substantial contribution of pyrite oxidation to the observed temporally variable 34s signals the variability of the 34s signal in pyrite and the injectant were both found to complicate the analysis of the stable isotope data however the incorporation of the data into a numerical modelling approach allowed to successfully employ the 34s signatures as a valuable additional constraint for identifying and quantifying the contribution of pyrite oxidation to the redox transformations that occur in response to the injection of oxygenated water

multifrequency full waveform sonic logging in the screened interval of a large diameter production well abstracta set of field experiments using multiple transmitter center frequencies was completed to test the application potential of low frequency full waveform sonic logging in large diameter production wells wireline logs were acquired in a simple open drillhole and a high yield large diameter production well completed with wire wound sand screens at an aquifer storage and recovery site in perth western australia phase shift transform methods were applied to obtain phase velocity dispersion images for frequencies of up to 4 khz a 3d representation of phase velocity dispersion was developed to assist in the analysis of possible connections between low frequency wave propagation modes and the distribution of hydraulic properties for sandstone intervals in the test well the highest hydraulic conductivity intervals were typically correlated with the lowest phase velocities the main characteristics of dispersion images obtained from the sand screened well were highly comparable with those obtained at t

palynological evidence for the latest oligocene early miocene paleoelevation estimate in the lunpola basin central tibet uplift of the tibetan plateau is ultimately driven by the cenozoic collision between the indian and eurasian plates and their continued convergence one approach for studying the tibetan plateau uplift is to verify the paleoelevation changes from collision to present day this is important for understanding both the tectonics and the climatic effects the new high resolution palynological record of the uppermost oligocene to the lowest miocene strata from the lunpola basin indicates that the vegetation types during the latest oligocene earliest miocene were dominated by mixed coniferous broadleaved forests being different from the modern steppe vegetation by using the coexistence approach to the fossil pollen records after calibration the effects of temperature difference and the lapse rate a maximum paleoelevation of 3190 100 m asl was estimated in the lunpola basin in the latest oligocene earliest miocene being 1500 to 2000 m lower compared with the previous oxygen isotope paleoelevation in the same region

oligocene koelreuteria sapindaceae from the lunpola basin in central tibet and its implication for early diversification of the genus abstract fossils are critical for understanding the uplift history of the tibetan plateau and its impact on the diversity and diversification of living organisms in eurasia however well preserved fossils especially plant megafossils are rare in the plateau in this paper we describe two species of koelreuteria namely k lunpolaensis sp nov and k miointegrifoliola based on exquisitely preserved capsular valves from the late oligocene of the lunpola basin central tibet koelreuteria lunpolaensis is distinguishable from all extant and fossil species of the genus in the strongly asymmetric form of the capsular valves the emarginate or lobed apex of the valves and zigzag lateral veins that are tapering towards the margin of the valves and is considered to represent an extinct lineage of the genus koelreuteria miointegrifoliola is most similar to k bipinnata type group of extant koelreuteria the diverse koelreuteria confirms a warm and humid environment with a low elevation in central tibet during the late oligocene based on their modern distributions fossil evidence indicates that the tibetan plateau was a center for diversity and diversification of koelreuteria in the oligocene miocene it also suggests that tibet might also serve as a refugium for the k bipinnata type group in the late oligocene

geochemical reconstruction of the provenance weathering and deposition of detrital dominated sediments in the perth basin the cretaceous leederville formation south west australia article i nfo the deep n10 km permian to present day perth basin in southwest western australia is composed of sedimentary successions of continental to shallow marine origin this study examines the compositional variation weathering and provenance of the early cretaceous leederville formation within the perth basin over 200 sediment samples were retrieved from two deep boreholes of 350 to 530 m in depth encompassing the leederville formation and analysed for major and trace element geochemistry and mineralogy the leederville formation is composed of subarkosic sands predominantly composed of quartz 64 and k feldspars 27 silts and clays composed of kaolinite 24 54 k feldspars 20 29 and quartz 18 40 with their compositional variation reflecting weathering hydraulic sorting during transport mostly subaqueous deposition and subsequent diagenesis most trace elements are associated with fine grained lithologies due to their occurrence within clays sulphide or zircon major and trace element geochemistry suggests a typical passive margin origin with minimal intrabasinal sediment recycling the regionally extensive yilgarn craton appears to be the main sediment source for the leederville formation within the study area

the andean type gangdese mountains paleoelevation record from the paleocene eocene linzhou basin abstract paleoelevation reconstruction using oxygen isotopes is making a significant contribution to understanding the cenozoic uplift of the himalayas and the tibetan plateau this paper presents new oxygen and carbon isotopic compositions from well dated tertiary paleosols lacustrine calcareous carbonates and marls from the nianbo 60 54 ma and upper pana formations 51 48 ma of the linzizong group in the linzhou penbo basin the sediments of the nianbo formation which are 180 m thick were deposited in alluvial fans braided rivers fan deltas and on nearshore to offshore lacustrine settings whereas those of the upper pana formation are 100 m thick and are comprised predominantly of proximal alluvial fan and braided river deposits correlations between the lithofacies and stable isotopic compositions suggest that the basin was mainly a hydrologically open environment it is confirmed that the 18 o c and 13 c c values from nianbo and pana formations have not yet been reset by late stage diagenesis based on petrographic examination oxygen isotope of the fossil ostracodes and tectonic deformation of strata the paleoelevations are reconstructed using the corrected most negative paleosurface water 18 o psw values these imply that the linzhou area had attained an elevation of 4500 400 m during the period of the indo asian collision i e achieved a near present elevation and may form an andean type mountain range stretching the gangdese arc before collision the gangdese mountains probably maintained high elevations since at least the paleocene and could play a crucial role in the climate change in the interior of the tibetan plateau during the early cenozoic the paleogeomorphic scenario of the eocene tibet is proposed to exist at two high mountains in excess of 4500 m that sandwiched a low elevation basin

nitrate reduction in an unconfined sandy aquifer water chemistry reduction processes and geochemical modeling nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of quaternary age ground water chemistry was studied in a series of eight multilevel samplers along a flow line deriving water from both arable and forested land results show that plumes of nitrate contaminated groundwater emanate from the agricultural areas and spread through the aquifer the aquifer can be subdivided into an upper 10 to 15 m thick oxic zone that contains o2 and no3 and a lower anoxic zone characterized by fe2 rich waters the redox boundary is very sharp which suggests that reduction processes of o2 and no3 occur at rates that are fast compared to the rate of downward water transport nitrate contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area the persistence of the high content of total dissolved ions in the no3 free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place nitrate is apparently reduced to n2 because both nitrite and ammonia are absent or found at very low concentrations possible electron donors in the reduced zone of the aquifer are organic matter present as reworked brown coal fragments from the underlying miocene and small amounts of pyrite at an average concentration of 3 6 mmol kg electron balances across the redoxcline based on concentrations of o2 no3 so42 and total inorganic carbon tic indicate that pyrite is by far the dominant electron donor even though organic matter is much more abundant groundwater transport and chemical reactions were modeled using the code phreeqm which combines a chemical equilibrium model with a one dimensional mixing cell transport model only the vertical component of the water transport was modeled since in contrast to rates along flow lines the vertical rates are close to constant as required by the one dimensional model average vertical transport rates of water in the saturated zone were obtained by tritium dating the modeling process is a two step procedure first the sediment column is initialized with natural water containing only oxygen as electron acceptor and subsequently agricultural waters containing both oxygen and nitrate are fed into the column the nitrate concentration of agricultural waters entering the saturated zone varies with time and an input function was therefore constructed by linear mixing of natural waters and agricultural waters this input function was fed into the column initialized with natural water and the model run forward in time to the year 1988 where field data are available comparison with field data shows that the variation in groundwater chemistry is well described by the model when reduction of oxygen and reduction of nitrate by pyrite oxidation are the only redox reactions occurring finally predictions are made for the distribution of water chemistry in the year 2003 downward progression of the redoxcline is accelerated by a factor of five due to nitrate pollution of the aquifer but absolute rates remain small of the order of a few centimeters per year the controlling factor for nitrate migration through the aquifer once it has reached the anoxic zone is the concentration and distribution of pyrite in the sediments

source rocks in mesozoic cenozoic continental rift basins east china a case from dongying depression bohai bay basin abstract lake basin evolution microscopic and organic geochemistry characteristics are investigated for the paleocene hydrocarbon source rocks of dongying depression bohai bay basin the upper e 2 3 s 4 and the lower e 2 3 s 3 are balanced filled lake basin sediments which show strong climate driven rhythmicity source rocks of these two units have relatively high organic matter content and are dominated by type i kerogen sedimentary and geochemical characteristics indicate there exist persistent lake water stratification and bottom anoxicity during the deposition process by contrast the middle e 2 3 s 3 is an over filled lake deposit dominated by uniform mudstones lacking obvious transgressive regressive cycles it indicates that the lake water lacks stratification and the bottom water is ventilated source rocks of this unit have relatively low organic abundance and are dominated by types ii and iii kerogen thermal evolution studies show that the upper e 2 3 s 4 has a relatively early and multi stage of hydrocarbon generation process and can generate immature oils while the lower e 2 3 s 3 and the middle e 2 3 s 3 have a relatively late and simple hydrocarbon generation process and mainly generate mature oils in addition the persistent increase of eom toc and total hydrocarbons toc indicates that the expelled hydrocarbons from the middle e 2 3 s 3 are in relatively small amounts compared with the other two units the middle e 2 3 s 3 acts as regional caprocks instead of significant source rocks as previously thought the viewpoint will be of great significance in future exploration

the nature and origin of late proterozoic high grade gneisses of the leeuwin block western australia abstract the leeuwin block consists predominantly of felsic gneisses ranging in composition from granodiorite to alkali granite field petrographic and geochemical evidence indicates derivation from igneous parents with the presence of na fe pyroxene and arfvedsonitic amphibole suggesting a type anorogenic affinities and development within a continental rift environment narrow lenses and blocks of massive mafic gneiss are widely distributed throughout the felsic units and are interpreted as remnants of original tholeiitic dolerite dykes emplaced in a continental setting a small area of layered plagioclase hornblende gneiss near augusta has a dioritic composition and is associated with anorthosite and hornblendite it may represent part of an original layered basic intrusion metamorphic parageneses reveal a progressive northward increase in grade from amphibolite to granulite facies developed under low pressure conditions two pyroxene geothermometry indicates that peak metamorphic temperatures attained 690 c there are no major geochemical changes with metamorphic grade and there is no evidence of large ion lithophile element depletion in the granulites zircon fractions obtained from a felsic granulite near dunsborough give u pb ages of 550 570 ma these are interpreted as dating igneous emplacement and together with earlier geochronological data establish that the leeuwin block developed as a separate crustal entity during the late proterozoic pan african event the terrane formed at the western edge of an earlier proterozoic mobile zone indicating progressive westward cratonization away from the archaean yilgarn craton it also indicates a termination of mobile belt activity and a change from a compressional to tensional regime by at least 570 ma ago shear zones bounding the major tectonic units became reactivated as normal faults during the phanerozoic and continental break up occurred along the western margin of the pan african terrane leaving the leeuwin block as the only intact fragment of late proterozoic crust in western australia

carbonate mineral water interactions in sulfide rich mine tailings the chemical composition and mineralogy of coatings on carbonate minerals from mine tailings have been studied using aqueous geochemical methods time of flight laser ionization mass spectrometry tof lims and transmission electron microscopy tem the goal is to study major and trace element partitioning between the aqueous and solid phase and to infer mechanisms that control the concentrations of elements in the pore water of sulfide rich mine tailings pore water samples and carbonate mineral grains were collected from four geochemically distinct zones within the tailings oxidation of sulfide minerals near the surface results in a large range in pore water ph 3 85 to 6 98 and aqueous concentrations of metals and sulfate with increasing depth in the tailings mineral water interactions lead to increasing ph and decreasing concentrations of metals and sulfate calculated mineral saturation indices trends in the abundance of ca fe mg and mn in tof lims profiles through the secondary coatings and electron diffraction patterns obtained from the coatings suggest that precipitation dissolution of jarosite group minerals gypsum goethite akaganeite amorphous fe oxyhydroxides and siderite control the aqueous ca fe na k and so4 concentrations the occurrence of secondary coatings on primary minerals is widespread and reactions with the secondary minerals rather than the primary mineral substrate probably represent the principal controls on trace element distributions in the pore water the data indicate that adsorption surface complexation and co precipitation reactions are important controls on the concentrations of trace elements in the pore water the occurrence of siderite coatings on the surface of ankerite grains suggests that fe bearing dolomite structure carbonate minerals dissolve incongruently this corroborates inferences made by previous workers that solubility differences between calcite and siderite lead to calcite dissolution and siderite precipitation during acid neutralization the accumulation of secondary coatings will diminish the rate of mineral dissolution reactions involving the primary minerals consequently the use of kinetic rate constants obtained from the literature for simulating the dissolution of primary mineral phases such as the carbonates and alumino silicates will likely overestimate the actual rates

reactive transport controls on sandy acid sulfate soils and impacts on shallow groundwater quality disturbance or drainage of potential acid sulfate soils pass can result in the release of acidity and degradation of infrastructure water resources and the environment soil processes affecting shallow groundwater quality have been investigated using a numerical code that integrates bio geochemical processes with water solute and gas transport the patterns of severe and persistent acidification ph 4 in the sandy carbonate depleted podzols of a coastal plain could be reproduced without calibration based on oxidation of microcrystalline pyrite after groundwater level decrease and or residual groundwater acidity due to slow vertical solute transport rates the rate of acidification was limited by gas phase diffusion of oxygen and hence was sensitive to soil water retention properties and in some cases also to oxygen consumption by organic matter mineralization despite diffusion limitation the rate of oxidation in sandy soils was rapid once pyrite bearing horizons were exposed even to a depth of 7 5 m groundwater level movement was thus identified as an important control on acidification as well as the initial pyrite content increase in the rate of fe ii oxidation lead to slightly lower ph and greater accumulation of fe iii phases but had little effect on the overall amount of pyrite oxidized aluminosilicate kaolinite dissolution had a small ph buffering effect but lead to the release of al and associated acidity simulated dewatering scenarios highlighted the potential of the model for risk assessment of bio geochemical impacts on soil and groundwater over a range of temporal and spatial scales

geochemical controls on sediment reactivity and buffering processes in a heterogeneous aquifer the injection and recovery of oxic water into deep anoxic aquifers may help to alleviate short and longterm imbalance between freshwater supply and demand the extent and structure of physical and geochemical heterogeneity of the aquifer will impact the water quality evolution during injection storage and recovery water sediment interactions within the most permeable parts of the aquifer where the bulk of the injectant will penetrate may dominate however water quality may also be impacted by interactions within the finer grained less permeable but potentially highly reactive media in this study the heterogeneity of the reductive capacity of an aquifer selected for water reuse projects was characterised the amount type and reactivity of the sedimentary reductants present determined and the relationship between reductive capacity and sedimentary lithologies quantified the average potential reductive capacities prctot based on total organic c and pyrite concentrations of the sediment were quantified for sands 382 lmol o2 g 1 clays 1522 lmol o2 g

a comparison of the geochemical response to different managed aquifer recharge operations for injection of urban stormwater in a carbonate aquifer abstract managed aquifer recharge mar is increasingly being considered as a means of reusing urban stormwater and wastewater to supplement the available water resources subsurface storage is advantageous as it does not impact on the area available for urban development while the aquifer also provides natural treatment however subsurface storage can also have deleterious effects on the recovered water quality through water rock interactions which can also impact on the integrity of the aquifer matrix a recent investigation into the potential for stormwater recycling via aquifer storage transfer and recovery astr in a carbonate aquifer is used to determine the important hydrogeochemical processes that impact on the recovered water quality an extensive period of aquifer flushing allows observation of water quality changes under two operating scenarios 1 separate wells for injection and recovery representing astr and 2 a single well for injection and recovery representing aquifer storage and recovery asr calcite dissolution produces the dominant inorganic chemical change to the quality of stormwater following storage in the carbonate aquifer independent of the mode of mar operation astr or asr the magnitude of calcite dissolution in response to the injection of urban stormwater exceeds that previously reported within the same aquifer using both stormwater and reclaimed wastewater while some dissolution is induced in response to redox processes the primary influence on dissolution is the reactivity of the source water itself as indicated by the sub saturation with respect to calcite cation exchange is evident through the astr mode of operation producing a marginal increase in the na concentration during freshening of the storage zone this increase in na concentration is not evident in the asr mode as cation exchange is limited to the initial pore flushes of the storage zone aquifer storage provides some treatment through nutrient removal mainly through removal of 35 of the dissolved organic c doc doc removal is greatest when the mar operation involves separate injection and recovery wells as astr allows enhanced removal by sorption asr can lead to nutrient recycling around the injection well which can produce water quality that is atypical of the quality in the bulk of the storage zone water recovered from asr shows some removal of doc through microbial oxidation coincident with removal of o2 from the source water which is considered to be a sustainable process during subsurface treatment during astr enhanced doc removal is attributed to adsorption but as with cation exchange this removal may be limited to the initial period of aquifer conditioning oxidation of pyrite is evident during the initial stages of injection until the pool of reactive pyrite within the storage zone is consumed affecting the quality of water recovered via the astr mode only

reactivity of organic matter in aquifer sediments geological and geochemical controls reduction rates in aquifers are commonly carbon limited but little is known about the molecular composition and degradability of sedimentary organic matter som in aquifer sediments the composition source and degradation status of som in aquifer sediments of fluvio glacial pleistocene and shallow marine pliocene origin were determined using flash pyrolysis gas chromatography mass spectrometry incubation experiments 106 d were used to assess the reactivity of som towards molecular oxygen a dominance of lignin derived components and long chain odd over even predominant alkanes indicate that terrestrial higher land plants were the main source of som even in the shallow marine sediments while bacterial lipid derived hopanoids and iso and anteiso c15 and c17 fatty acids indicate a minor contribution of microbial biomass no compositional difference was observed between som present in the fine 63 m and coarse fraction 63 2000 m a significant part of som was not present as low molecular weight compounds but was macromolecularly bound for the fluvio glacial sediments a relatively higher abundance of resistant macro molecular compounds was in agreement with stronger signs of aerobic lignin alkane and hopanoid oxidation the more degraded status of som in the fluvio glacial sediments was consistent with their significantly lower som mineralization 2 6 during incubation as compared with the shallow marine sediments 9 14 the reactivity towards oxygen of som was controlled by the extent of past aerobic oxidation not the age of som but the extent of oxygen exposure during syn and postdepositional conditions seems most important in affecting the degradation status of som in aquifer sediments and thus their ability to reduce oxidants copyright 2004 elsevier ltd

characterization of the reactivity of riverine heterogeneous sediments using a facies based approach the rhine meuse delta the netherlands large groundwater resources are found in densely populated lowland areas which consist often of young unconsolidated and reduced sediments when anthropogenic activities lead to oxygenation of the aquifer breakdown of the main reduced fractions i e sedimentary organic matter som and pyrite could lead to severe groundwater deterioration such as acidification heavy metal mobilization and increased hardness the characterization of the reactive properties of these sediments is important in predicting groundwater deterioration but is often complicated by the high degree of heterogeneity of these sediments in this study the potential reduction capacity prc based on som and pyrite content the potential buffer capacity pbc based on carbonate content potential acidification capacity pac based on the potential acid production by sulfide oxidation and the measured reduction capacity mrc of five facies which are typical of the riverine sediments in the rhine meuse delta the netherlands were determined a universal facies classification model was used to classify the deposits into more homogeneous sub units based on lithologic and geogenic properties with a further sub division into oxic or anoxic redox environment based upon groundwater data and field observations the bulk chemical data show strong variation across facies for the median values of prc 186 9093 mmol o2 kg 1 pbc 17 132 mmol o2 kg 1 and pac 36 1530 mmol h kg 1 the mrc was measured as reactivity to molecular o2 exposure and was 0 5 567 3 mmol o2 kg 1 steady state oxidation rates were in the wide range of 0 001 10 355 mmol o2 kg 1 day 1 but were typically about 3 8 times faster in fine facies than in coarse facies both the prc and mrc depend strongly on grain size but also on the syn post depositional environment and redox conditions the main part of the prc consists of som but pyrite reactivity is higher than som reactivity as shown by the relative depletion of pyrite in oxic subfacies and the preferential oxidation during the oxidation experiments some facies are very prone to acidification because the pac is higher than the pbc but the oxidation experiments also show that acidification could already start before the prc is fully exhausted this study is one of the few that combines bulk chemical data groundwater data and reactivity measurements and shows that a facies based approach is a practical tool in characterizing the reactivity of heterogeneous deposits 2007 elsevier ltd all rights reserved

synoptic reconstruction of a major ancient lake system eocene green river formation western united states numerous 40ar 39ar experiments on sanidine and biotite from 22 ash beds and 3 volcaniclastic sand beds from the greater green river piceance creek and uinta basins of wyoming colorado and utah constrain 8 m y of the eocene epoch multiple analyses were conducted per sample using laser fusion and incremental heating techniques to differentiate inheritance 40ar loss and 39ar recoil when considered in conjunction with existing radioisotopic ages and lithostratigraphy biostratigraphy and magnetostratigraphy these new age determinations facilitate temporal correlation of linked eocene lake basins in the laramide rocky mountain region at a significantly increased level of precision to compare our results to the geomagnetic polarity time scale and the regional volcanic record the ages of eocene magnetic anomalies c24 through c20 were recalibrated using seven 40ar 39ar ages overall the ages obtained for this study are consistent with the isochroneity of north american land mammal ages throughout the study area and provide precise radioisotopic constraints on several important biostratigraphic boundaries applying these new ages average sediment accumulation rates in the greater green river basin wyoming were approximately three times faster at the center of the basin versus its ramp like northern margin during deposition of the underfilled wilkins peak member in contrast sediment accumulation occurred faster at the edge of the basin during deposition of the balanced filled to overfilled tipton and laney members sediment accumulation patterns thus reflect basin center focused accumulation rates when the basin was underfilled and supply limited accumulation when the basin was balanced filled to overfilled sediment accumulation in the uinta basin at indian canyon utah was relatively constant at 150 mm k y during deposition of over 5 m y of both evaporative and fluctuating profundal facies which likely reflects the basin margin position of the measured section the most rapid sediment accumulation for the entire system 1 m k y occurred between 49 0 and 47 5 ma when volcaniclastic materials from the absaroka and or challis volcanic fields entered the green river formation lakes from the north our new ages combined with existing paleomagnetic and biostratigraphic control permit the first detailed synoptic comparison of lacustrine depositional environments in all the green river formation basins coupled with previously published paleocurrent observations our detailed correlations show that relatively freshwater lakes commonly drained into more saline downstream lakes the overall character of eocene lake deposits was therefore governed in part by the geomorphic evolution of drainage patterns in the surrounding laramide landscape freshwater overfilled lakes were initially dominant 53 5 52 0 ma possibly related to high erosion rates of remnant cretaceous strata on adjacent uplifts expansion of balanced fill lakes first occurred in all green river formation basins at 52 0 51 3 ma and again between 49 6 and 48 5 ma evaporative underfilled lakes occurred in various basins between 51 3 and 45 1 ma coincident with the end of the early eocene climatic optima and subsequent onset of global cooling defined from marine record however evaporite intervals in the different depocenters were deposited at different times rather than being confined to a single episode of arid climate evaporative terminal sinks were initially located in the greater green river and piceance creek basins 51 3 48 9 ma then gradually migrated southward to the uinta basin 47 1 45 2 ma this history is likely related to progressive southward construction of the absaroka volcanic province which constituted a major topographic and thermal anomaly that contributed to a regional north to south hydrologic gradient the greater green river and piceance creek basins were eventually filled from north to south with absarokaderived detritus at sedimentation rates 1 2 orders of magnitude greater than the underlying lake deposits

modeling of carbon cycling and biogeochemical changes during injection and recovery of reclaimed water at bolivar south australia 1 managed aquifer recharge is an increasingly popular technique to secure and enhance water supplies among a range of recharging techniques single well aquifer storage and recovery asr is becoming a common option to either augment drinking water supplies or facilitate reuse of reclaimed water for the present study a conceptual biogeochemical model for reclaimed water asr was developed and incorporated into an existing reactive multicomponent transport model the conceptual and numerical model for carbon cycling includes various forms of organic and inorganic carbon and several reactive processes that transfer carbon within and across different phases the major geochemical processes considered in the model were microbially mediated redox reactions driven by the mineralization of organic carbon mineral dissolution precipitation and ion exchange the numerical model was tested and applied for the analysis of observed data collected during an asr field experiment at bolivar south australia the model simulation of this experiment provides a consistent interpretation of the observed hydrochemical changes the results suggest that during the storage phase dynamic changes in bacterial mass have a significant influence on the local geochemistry in the vicinity of the injection extraction well farther away from the injection extraction well breakthrough of cations is shown to be strongly affected by exchange reactions and in the case of calcium by calcite dissolution

palaeo altimetry of the late eocene to miocene lunpola basin central tibet the elevation history of the tibetan plateau provides direct insight into the tectonic processes associated with continent continent collisions here we present oxygen isotope based estimates of the palaeo altimetry of late eocene and younger deposits of the lunpola basin in the centre of the plateau which indicate that the surface of tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years we conclude that crustal but not mantle thickening models combined with plate kinematic solutions of india asia convergence are compatible with palaeo elevation estimates across the tibetan plateau

cenozoic vertebrate evolution and paleoenvironment in tibetan plateau progress and prospects abstract due to its lofty height the tibetan plateau features some of the harshest environments in the world with extreme coldness low oxygen high uv radiation and in places severe aridity these harsh environments have served as the main driver of vertebrate evolution during the cenozoic that produced a low productivity low diversity high endemicity community environmental forcing seems to be a dominant mechanism for mammalian evolution in marginal habitats mammals have acquired special adaptations for thermal insulation oxygen transport dna damage repair and others while broadly similar to faunal assemblages in north china and central asia tibetan faunas often show initiation of cold adapted lineages that predate ice age megafauna our out of tibet hypothesis thus postulates that cold tolerant species in pliocene high tibet were pre adapted to conditions that were to become widespread during the subsequent pleistocene ice age and tibet had thus become a cradle for ice age megafauna the best examples of the out of tibet scenario include the tibetan woolly rhinoceros coelodonta thibetana tibetan bharal pseudois asian hunting dog sinicuon and ancestral snow leopard panthera blytheae our third pole to north pole linkage of an extinct pliocene tibetan fox vulpes qiuzhudingi with the late pleistocene and extant arctic fox vulpes lagopus is a subset of the out of tibet hypothesis one of the iconic tibetan mammals the endemic tibetan antelope pantholops has the longest residence in tibet going back to the late miocene suggesting a long history of perfecting its adaptations to cold environments stable carbon and oxygen isotope analyses of fossils from the tibetan plateau reveal significant spatial and temporal variations in the evolution of herbivores diets and environments during the late cenozoic the diets of modern tibetan herbivores consist primarily of c3 plants reflecting the present day c3 dominance in high elevation cold habitats the available carbon isotope data however show that warm climate c4 grasses were a significant dietary component of ancient herbivores in the gyirong basin central himalayas in the late miocene and in shangri la southeastern tibetan plateau in the pliocene and likely in the qaidam basin ne tibetan plateau from late miocene to early pliocene and in kunlun pass basin northeastern tibetan plateau in the pliocene this suggests that c4 grasses spread into the tibetan plateau in the late miocene and had persisted in some places to early pleistocene but have since disappeared or become insignificant in the region the retreat of c4 grasses from the tibetan plateau is most likely driven by decreases in local temperatures to below the cross over temperature unfavorable to c4 grasses as a result of tectonic uplift and or global climate change the available isotope data also show that high elevation cold climatic conditions that favor c3 over c4 grasses arrived earlier in southwestern tibetan plateau than in southeastern and northeastern parts of the plateau this would imply that the tibetan plateau had not uniformly reached its present height as recent as early pleistocene future research should focus on determining intra regional patterns of ecological and climatic changes in order to tease apart the effects of tectonic uplift and global climate change on local and regional environmental changes and to better understand the linkage between tectonics and climatic and biotic changes

depositional and paleohydrogeological controls on the distribution of organic matter and other reactive reductants in aquifer sediments abstract the reactivity of sedimentary reductants is the main control for the natural attenuation of common groundwater contaminants such as nitrate or chlorinated hydrocarbons middle miocene to late pleistocene 0 01 20 my old aquifer sands of marine fluvial fluvio glacial and aeolian origin were characterized to determine the control of sediment depositional environment sediment age and paleohydrology on the distribution and reactivity of sedimentary reductants in addition to the variability in the molecular composition of sedimentary organic matter som the reduction reactivity of these sediments was determined oxygen consumption and carbon dioxide production during sediment incubations indicated that som pyrite and ferrous iron bearing carbonates were the main reductants bulk 13 c org values 25 indicated that terrestrial higher land plants were the main precursor of som regardless of sediment origin however pyrolysis gc ms analysis showed that som in the marine tertiary sands contained lignin with preserved side chains while in the pleistocene fluvial and fluvio aeolian sediments highly degraded lignin and recalcitrant macromolecular aliphatic structures dominated som indicative of aerobic degradation the higher dynamics of these terrestrial depositional environments as compared with their marine counterpart likely allows for increased oxygen exposure times and thus more intense aerobic degradation of som the aquifer sediment that fills a large erosional valley created during the saale ice age likely consists of fluvio glacially reworked marine tertiary sediments as supported by carbonate isotopic evidence the more degraded status and decreased reactivity of som in this sediment than in its precursor is likely due to the increased oxygen exposure during dynamic fluvio glacial reworking despite the highly degraded nature of som and the absence of pyrite in the pleistocene fluvial and fluvio aeolian sediments oxygen consumption rates were high during the incubation of sediments from the shallowest part of the aquifer a reactive ferroan carbonate phase was inferred as the main source of oxidant demand in shallow fluvial and aeolian sands depleted oxygen and carbon isotopes indicated that this phase was groundwater derived aerobic degradation during sediment deposition appears to control the molecular composition and reactivity of som in aquifer sediments and to affect the potential of subsequent diagenetic pyrite formation in addition paleo hydrological conditions may result in the accumulation of a ferrous iron bearing carbonate phase precipitated during the exfiltration of fe ii containing anoxic groundwater

constraints on the early uplift history of the tibetan plateau the surface uplift history of the tibetan plateau and himalaya is among the most interesting topics in geosciences because of its effect on regional and global climate during cenozoic time its influence on monsoon intensity and its reflection of the dynamics of continental plateaus models of plateau growth vary in time from pre india asia collision e g 100 ma ago to gradual uplift after the india asia collision e g 55 ma ago and to more recent abrupt uplift 7 ma ago and vary in space from northward stepwise growth of topography to simultaneous surface uplift across the plateau here we improve that understanding by presenting geologic and geophysical data from north central tibet including magnetostratigraphy sedimentology paleocurrent measurements and 40ar 39ar and fission track studies to show that the central plateau was elevated by 40 ma ago regions south and north of the central plateau gained elevation significantly later during eocene time the northern boundary of the protoplateau was in the region of the tanggula shan elevation gain started in pre eocene time in the lhasa and qiangtang terranes and expanded throughout the neogene toward its present southern and northern margins in the himalaya and qilian shan