timing of the indian summer monsoon onset during the early holocene evidence from a sediment core at linggo co central tibetan plateau the spatial and temporal variability effects and mechanisms of the indian summer monsoon ism have been investigated intensively during the past few decades the pattern of a relatively strong i

arid zone groundwater recharge and salinisation processes an example from the lake eyre basin australia in arid central australia the 1 14 m km2 endorheic lake eyre basin leb experiences sporadic floods and contains saline shallow groundwater in this basin where on ground physical and chemical data are very sparse new observations of major ion chemistry stable isotopes 2h 18o 13c radiogenic isotopes 3h 14c and remote sensing modis data were used to investigate groundwater recharge and salinisation processes in 2006 2007 in january 2007 there was a large and intense local rainfall event followed by flooding to the normally dry lake eyre resulting from heavy rainfall in the northern leb that took 2 months to arrive at lake eyre groundwater chemistry from this study show no evidence of recharge from the floodwaters or the local rainfall however this does not preclude the process low transit times and low infiltrating volumes may mean that the recharge event has not yet been detected over the longer term the stable isotope chemistry indicates that groundwater is predominantly diffusely recharged during heavy local rainfall events 100 150 mm month and radiogenic isotopes reflect an older shallow groundwater efficiently mixing with recent decadal recharge the high total dissolved solids tds of regional shallow groundwater up to 52 5 g l is intrinsically linked with these recharge processes where infiltrating diffuse rainfall is evaporated and heavy rainfall events transport saline pore water saline due to evaporation in the unsaturated zone to the groundwater system the high tds of shallow groundwater beneath the dry lake eyre bed up to 322 g l is also controlled by evaporation however although evaporite minerals are prolific in the lake area the non conservative behaviour of br in pore water limits analysis of the role of halite mineral dissolution and precipitation reactions controlling groundwater salinity evaporation driven salinisation of shallow groundwater in arid central australia is distinct from the transpiration driven salinisation of groundwater in the australian murray basin located in a semi arid climate and results in relatively high groundwater salinity values compared with many other large arid zone endorheic basins across the world

mid late holocene vegetation response to climatic drivers and biotic disturbances in the banni grasslands of western india abstract tropical grasslands and savannas are globally extensive and are of significant environmental economic and ecological importance these ecosystems are anticipated to be particularly sensitive to future changes in climate and understanding how these systems have responded to climatic changes in the past can provide us with insights into their potential responses to future global change in this study the temporal dynamics of c 3 c 4 vegetation changes in response to changes in moisture availability local fire events and changing levels of herbivory in a summer rainfall region of western india are reconstructed for the past 4600 cal yr bp paleodata such as stable carbon isotope of bulk organic matter 13 c org oxygen isotope from carbonate shells 18 o shell macro charcoal and herbivore dung fungal spores are reported from the retrieved cores of two wetland sites located in the banni grasslands of western india results show that vegetation in the banni was composed mostly of c 3 vegetation from 4600 to 2500 cal yr bp after which there was a decline in c 3 vegetation from the late holocene to the present there was a mix of both c 3 and c 4 vegetation with c 4 grasses being more abundant in the ecosystem these shifts were coincident with rainfall changes from more mesic conditions during 4600 to 2500 cal yr bp to more arid conditions towards the present as indicated by 18 o shell isotope data the period of increase in c 4 vegetation also coincides with a period of increased biotic disturbances in the ecosystem particularly fire given the current scenarios of global warming recurrent drought events and increased anthropogenic use of similar ecosystems such studies can provide us insights into potential future trajectories of these ecosystems

wet climate during the little ice age in the arid tarim basin northwestern china a relatively cold period the little ice age lia just prior to the current warm period has been documented from many regions of the globe however hydrological changes wet dry conditions during the lia appear to be very different across different climatic regimes suggesting that the position strength and or pattern of atmospheric circulation could have changed significantly in the past therefore paleohydrological studies may have some implications for potential future hydrological changes in an anticipated warming world in this study we investigated hydrological changes over the last 800 years in the arid tarim basin northwestern china we used carbon isotopes of plant remains mainly leaves from a 10 5 m long aeolian sand sediment section to evaluate changes in dry wet conditions the average value of carbon isotopes of plant remains during the lia period ad 1490 to 1890 is 26 0 ranging from 28 2 to 23 6 much lower than values before average of 24 3 from 25 5 to 22 4

an environmental reconstruction of the palaeo amazon river system middle late miocene nw amazonia abstract new sedimentological and palynological data from the tertiary sediments in the upper amazon river area suggest that these sediments are fluvio lacustrine deposits of middle to late miocene age they were generated as a result of the uplift of the eastern cordillera andes and constitute possibly the oldest relics of the amazon river system the palaeoenvironment in which these sediments were deposited is characterized by extensive wetlands environments formed by swamps shallow lakes crevasse splay channels and crevasse delta lakes where the channel environment is poorly represented the palaeovegetation was dominated by palms e g mauritia and grimsdalea riverine taxa e g bombacaceae amanoa and alchornea ferns and fern allies e g polypodiaceae and selaginellaceae floating meadows gramineae and aquatic taxa ceratopteris botryococcus and azolla the relative abundance of gramineae and the occurrence of andean type pollen taxa is related to the andean origin of the fluvial system the varzeas of the present upper amazon river flood basin are probably the best analogue for the middle to late miocene environment intervals rich in marine palynomorphs mangrove pollen brackish tolerant molluscs and ostracods and ichnofossils of the thalassinoides teichichnus association suggest that the palaeoenvironment was characterized by brackish conditions and marine influence these marine incursions are possibly related to the langhian and the serravallian global sea level rise although in the middle miocene a global cooling is known to have occurred no indicators of a cooler climate have been observed in the miocene palynoflora of the upper amazon river area finally four new sporomorph species are described belonging to the form genera psilatriletes clavainaperturites and psilaperiporites

isotopic paleontologic and ichnologic evidence for late miocene pulses of marine incursions in the central andes recognition of an inferred miocene marine incursion affecting areas from colombia through peru and bolivia and into argentina is essential to delineate the south american seaway in bolivia corresponding strata of inferred marine origin have been assigned to the late miocene yecua formation we carried out high resolution 13 c and 18 o isotopic studies on 135 in situ carbonates from 3 outcrops combined with detailed sedimentologic paleontologic and ichnologic analysis four less negative 13 c excursion levels were recorded that coincide well with beds containing marine body barnacle and trace ophiomorpha fossils these strata are interbedded with red green beds containing mudcracks plant roots gypsum and trace fossils of the continental scoyenia ichnofacies our data are significant in that they show for the first time four possible short lived marine incursions in the bolivian central andes during the late miocene the result is constrained by a new u pb date of 7 17 0 34 ma at the top of yecua strata

water salinization in arid regions observations from the negev desert israel abstract the processes affecting salinization of precipitation surface water vadose water and groundwater were studied in the negev desert israel observations spanning 18 years included the collection of rainfall at three rain sampling stations flood water at six flood stations vadose water from four coreholes penetrating chalk formations and groundwater from 16 monitoring wells tapping the chalk aquitard dissolved carbonate dust and evaporation of the falling raindrops result in ca hco 3 2 facies and increased ion concentration of the rainwater with respect to inland more humid regions the exposure of flood water to evaporation during flood events is minimal the observed ca hco 3 2 facies and salt enrichment by a factor of three to five in the flood water with respect to precipitation results primarily from interactions of the flood water with the chalk and limestone bedrock including ion exchange on na and k bearing minerals and the dissolution of calcite gypsum and halite the presence of these salts at and near land surface results from the complete evaporation of rainwater in land surface depression storage areas following most rain events except for a small portion moving through the low permeability chalk matrix most of the vadose water moves through preferential pathways and is typically not exposed to evaporation this dual movement of water accounts for the nacl facies of vadose water and the variable rates of isotopic depletion and salt dilution observed in the underlying heterogeneous groundwater in the saturated zone although the variable mixing with low salinity isotopically depleted water percolating from the fractures accounts for the depleted isotopic composition of the groundwater its relatively low solute content cannot modify the groundwater nacl facies consequently only groundwater salinity in the chalk is reduced by the preferentially flowing water but the ca hco 3 2 facies prevailing in the rainwater and flood water disappears and the nacl imprint from the vadose zone prevails

geology petrology and isotope geochemistry of massif type anorthosites from southwest madagascar four massif type anorthosite bodies 25 100 km2 in area occur within high pressure granulite facies supracrustal gneisses in southwestern madagascar two of these bodies ankafotia and saririaky appear to have been pulled apart by 40 km in a ductile shear zone but structural features such as sub vertical stretching lineations indicate an origin by intense west directed flattening and pure shear country rocks graphite series include abundant graphite schist some with 60 graphite marble quartzite and minor amphibolite and leucogneiss comagmatic granitoids e g charnockites are conspicuously absent the anorthosite bodies are dominated by coarse grained anorthosites and leuconorites feldspars typically 3 5 cm up to 1 m minor norites and oxide rich ferrogabbros occur near the margins but ultramafic rocks are absent typical mineralogy of the anorthositic rocks is plagioclase an41 54 orthopyroxene en38 66 augite mg 32 68 ilmenite magnetite apatite high alumina to 6 1 wt al2o3 orthopyroxene megacrysts are widespread most have exsolutions of calcic plagioclase an72 85 but some contain garnet lamellae metamorphism has produced abundant recrystallization and sporadic coronitic garnet mg 12 36 clinopyroxene assemblages rb sr isotopic analyses of whole rocks and minerals reveal no meaningful age relationships the age of late neoproterozoic metamorphism is best constrained at 559 50 ma by a 6 point sm nd mineral isochron whole rock plag pyx ilm apat gar from a saririaky oxide rich gabbro the igneous crystallization age of the anorthosites is estimated at 660 60 ma by a 19 point combined whole rock and mineral sm nd isochron for samples from both the ankafotia and saririaky bodies initial isotopic ratios calculated at 0 66 ga among 13 whole rocks are nd 2 6 to 5 2 mean 3 7 and isr 0 70328 0 70407 mean 0 70347 indicating derivation of the malagasy anorthosites from a depleted mantle source and little if any contamination with archean crustal material one anorthosite sample with nd 1 4 and isr 0 70344 calculated at 0 66 ga probably reflects the effects of assimilation of early to middle proterozoic crustal basement but typical surrounding graphite schist nd 0 3 isr 0 70636 both at 0 66 ga tdm 1131 ma represents only a minor potential contaminant for the anorthosite bodies tdm model ages of the malagasy anorthosites 797 1280 ma mean of 14 samples 949 ma as those of most other massif type anorthosites are older than the true crystallization age because of crustal contamination effects our isotopic data together with recent u pb data from the anorthosites and surrounding country rocks are consistent with emplacement of the malagasy anorthosite bodies at or before the start of a protracted high grade metamorphic event or series of events between about 630 and 550 ma this period coincides with the collision between and amalgamation of east and west gondwana

miocene semidiurnal tidal rhythmites in madre de dios peru comment comment hovikoski et al 2005 1 acknowledge that their results contradict campbell et al 2000 2 who described the madre de dios formation in sw amazonia as the last major cycle of cenozoic continental deposition yet they propose that their rhythmite statistics settle the debate also with hoorn

late holocene hydroclimatic variation in central asia and its response to mid latitude westerlies and solar irradiance abstract hydroclimatic variations in central asia are widely recognized to be tele connected with the north atlantic climate via the mid latitude westerlies however the long term hydroclimatic variation and its response to north atlantic climate changes are not fully understood here we report multi decadal and centennial hydroclimatic variations in central asia during the late holocene using high resolution oxygen and carbon isotopes of bulk carbonate from a remote hydrologically closed alpine lake in tianshan mountains northwestern china the hydroclimatic variations inferred from the covariance between 18ocarb and 13ccarb and published multi proxy in the lake sayram together agree well with the records from the central asia showing enhanced effective moisture at the intervals of 4000 3780 3590 3210 2800 2160 1700 1370 and 890 280 cal yr bp during the negative phase of north atlantic oscillation nao comparison with european hydroclimatic changes on centennial scale our records not only provide valuable insight into the hydroclimatic variations in central asia but also indicate all broadly contemporaneous changes with that of southern europe whereas antiphase with that of northern europe we then conclude that the observed antiphase hydroclimatic pattern between northern europe and southern europe central asia on centennial time scale during the late holocene were persistently controlled by the north south migration of mid latitude westerlies and changes of nao phase in response to solar irradiance forcing however further research is necessary to fully disentangle the natural and anthropogenic forcing mechanisms for enhanced effect moisture and or precipitation in central asia

water salinity and productivity recorded by ostracod assemblages and their carbon isotopes since the early holocene at lake qinghai on the northeastern qinghai tibet plateau china abstract lake qinghai the largest saline lake in china is a closed basin lake with a salinity of 16 g l and is situated in the sensitive semi arid zone between the asian monsoon controlled area and the westerly jet stream influenced area with the support of the international continental drilling program icdp lake qinghai was drilled in 2005 using the icdp glad800 drilling system two ostracod species i e limnocythere inopinata and eucypris mareotica were found only in the upper 5 15 m of the drilled core 1f covering 12 ka where the depths of 5 15 to 3 15 m 12 0 7 4 ka are dominated by e mareotica and the depths of 3 15 to 0 m 7 4 ka present are dominated by l inopinata the presence of the ostracod eucypris mareotica was related to the high salinity of the water exceeding 30 g l and the dominant species of ostracod limnocythere inopinata was related to the brackish water 3 16 g l in the lake qinghai area li et al 2010 the changes in the carbon isotope in the modern ostracod shells were related to the water salinity and productivity on the lake bottom in lake qinghai li et al 2012 on this basis this study evaluated the changes in lake salinity and productivity and their relation to climatic change using changes in the relative abundances of ostracod fossil species assemblages and the stable carbon isotope in ostracod shells from core 1f and other published data e g total organic carbon content 13 c toc and ice core 18 o the single occurrence of ostracod eucypris mareotica and the highest average 13 c values 0 2 in their shells indicated that the lake salinity and productivity were very high a phenomenon that was related to the high temperature and low lake level caused by intense evaporation even though the precipitation increased sharply in the early holocene the deceased abundance of ostracod e mareotica and the lowest average 13 c values 2 0 in ostracod shells showed that the lake salinity and productivity decreased because of the increased lake level and decreased temperatures in the middle holocene finally the lake level decreased but the water salinity and the lake productivity gradually increased because of the high e i ratio related to the increased temperature in the late holocene

u pb single zircon pb evaporation and sm nd isotopic study of a granulite domain in se madagascar madagascar is a poorly known precambrian domain at the eastern border of the mozambique belt strongly affected by the pan african orogeny this large island represents a key part of gondwanaland and the accurate dating of the major metamorphic event is critical for the reconstruction of that supercontinent in the southeastern zone of the island metamorphism has reached high temperature and low pressure conditions 850 c and 5 kbar with moderate retrogression a u pb conventional multigrain single zircon stepwise pb evaporation and sm nd geochronological study on meta felsic rocks has shown that basement of at least lower proterozoic age was strongly metamorphosed around 570 580 ma this tectometamorphic event nearly obliterated any pre pan african zircon isotopic memory the granulite facies metamorphism is associated with the syn metamorphic emplacement of the anosyan charnock ites and granites a strong channelized fluid contribution at 545 ma has produced the re crystallization of biotite apatite

holocene climate variability in arid asia nature and mechanisms abstract the papers in this special issue are derived from a selection of presentations given at the rachad workshop titled pattern of holocene climate change in central asia data synthesis held at lanzhou university people s republic of china from 25th to 27th july 2006 rachad is inqua palaeoclimate commission palcomm project 0502 concerned with rapid climate change in central asia s drylands and the 2006 workshop was its fourth gathering the rachad project was established in 2000 and has been led by prof fahu chen from lanzhou university rachad s initial objectives were to stimulate the reconstruction of holocene climatic and environmental changes in arid central asia at high resolution to intensify international research collaboration and to develop and refine techniques for environmental reconstruction and dating

evolutions of water stable isotopes and the contributions of cryosphere to the alpine river on the tibetan plateau the significant changes of cryosphere on the tibetan plateau tp are an important cause of concern for the huge population in asia which depends on the glacier permafrost feed rivers up to now little is known about the response of runoff to the cryospheric changes under a warming climate taking an example of a typical alpine river hereafter named klr river in kunlun mountains pass on the tp to investigate the hydrological processes and quantify the potential recharge sources using stable isotopes and electrical conductivities the results showed significantly temporal variations in isotopes of precipitation and river water deviations in the precipitation isotopes indicated that precipitation in kunlun mountains pass during summer months mainly originated from local recycled moisture and slightly influenced by monsoon the klr river was separated into three hydrological components which include precipitation meltwater of glacier and meltwater of subsurface ground ice on average the meltwater of glacier accounted for 56 64 of total flow whereas the meltwater of subsurface ground ice contributed 37 44 and only 5 92 was supplied by precipitation evidently the contributions of glacier and thawing permafrost are up to as high as 94 the cryosphere played a crucial role on the hydrological cycle on the tp which would be important to understand the water resource distribution in permafrost regions on the tp under the global warming

contamination of groundwater under cultivated fields in an arid environment central arava valley israel the purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment precipitation of 50 mm year due to cultivation additional aims were to study the fate of n k and other ions along the whole hydrological system including the soil and vadose zone and to compare groundwater in its natural state with contaminated groundwater through the drilling of several wells a combination of physical chemical and isotopic analyses was used to describe the hydrogeological system and the recharge trends of water and salts to the aquifers the results indicate that intensive irrigation and fertilization substantially affected the quantity and quality of groundwater recharge low irrigation efficiency of about 50 contributes approximately 3 5 4 million m 3 year to the hydrological system which corresponds to 0 65 m per year of recharge in the irrigated area by far the

holocene variations in asian monsoon moisture a bidecadal sediment record from the south china sea the east asian monsoon system involves extensive transport of sensible latent heat between land and sea and from low to high latitudes our high resolution bidecadal marine records present a first detailed history of monsoon climate change over the holocene the high amplitude perturbation in monsoon moisture centered at 8 150 years ago and the monsoon maximum in the early holocene show inter hemispheric teleconnections to both a cool episode in greenland and to the indian monsoon monitored in the arabian sea periodicities of 84 102 and especially near 775 years in monsoon variation suggest a climatic forcing both by long term oscillations in thermohaline circulation and possibly solar activity cycles

stable isotope and ostracode species assemblage evidence for lake level changes of nam co southern tibet during the past 600 years abstract ostracode species assemblages and stable oxygen and carbon isotopes of shells from two 210 pb dated short cores of 78 cm and 47 cm length taken from lake nam co southern tibet provide information about lake level history of the past approximately 600 years at decadal resolution a transfer function is applied to reconstruct paleo water depths from modern ostracodes ostracode assemblages and isotope data from five species allow a subdivision into phases of lake level evolution before 1600 ad relatively low oxygen isotope values and high abundances of deep water 30 m ostracodes i e leucocythere dorsotuberosa leucocythere dorsotuberosa f postilirata suggest a lake level 10 m higher than today between 1600 ad and 1800 ad more positive oxygen isotope values and higher abundances of shallow water ostracodes i e ilyocypris cf mongolica candona xizangensis suggest a lake level approximately 40 m below modern level between 1800 ad and 1920 ad oxygen isotopes are characterized by a trend to more negative values followed by a trend to more positive ones these trends are interrupted by several short term fluctuations but overall oxygen isotope values suggest a drop in lake level a clearer lake level picture is provided by species assemblages that suggest a continuously increasing lake level since 1900 ad precipitation data from meteorological stations nearby show an increase in precipitation in the last 30 years the low lake level between 1600 ad and 1800 ad is contemporary to the little ice age during that cold period meltwater input into the lake decreased this underlines the sensitivity of the level of lake nam co to temperature changes on the tibetan plateau

early to mid pleistocene ostracod δ18o and δ13c in the central tibetan plateau implication for indian monsoon change as one of the pioneering projects of the chinese environmental scientific drilling cesd program a 206 5 m long sediment core ce was retrieved from co ngoin co lake basin in the central tibetan plateau limnic records of the abundance of ostracod shells and their oxygen and carbon isotope measurements together with the geochemical and the sedimentological investigations were carried out on the interval between 143 and 52 m core depths corresponding to ca 2 01 0 84 myr distinct oscillations of the abundance and the chemical compositions of ostracod shells have yielded the original information about variations in lakewater chemistry in association with the change in the indian monsoon over the period of 2 01 to 0 84 myr the climate conditions during the early pleistocene were characterized by frequent oscillations and the ostracod records had expressed its synchronous response to these oscillations a major climate change occurred in the co ngoin area at about 0 93 myr a pronounced fluctuation in ostracod delta 18o and delta 13c during the mid pleistocene transition mpt is possibly associated with an increase in continental ice sheets the compositional and the sedimentological characters of the immediately overlying sediments imply a shallow aquatic environment and also a harsh salinity condition beyond the tolerance limits for ostracod survival resulting in the disappearance of the qinghaicypris crassa huang 1979 around 0 84 myr

determining the spatial and temporal patterns of climate changes in china s western interior during the last 15 ka from lacustrine oxygen isotope records china s western interior is a climatologically complex region where climatic conditions are primarily controlled by the westerly jet stream and the asian monsoon system observations reveal that the 18o signatures of these atmospheric elements as expressed in their meteoric waters are different and these differences are reflected in the lacustrine systems that are ultimately fed by the meteoric waters empirical orthogonal function eof decomposition of 17 lacustrine 18o records from this area clearly reveals the spatial and temporal structures of climate changes during the last 15 ka the first eof mode dominated by sites in the nw sector captures the temperature effect on the variability of the 18o dataset we interpret the variations through time in the amplitude of this mode to be indicative of changes in summer air temperature the second eof mode heavily weighted by sites in the se sector reveals the amount effect on 18o and thus its amplitude time series indicates changes in the intensity of the asian summer monsoon our eof based reconstructions of regional climate are generally consistent with the 18o records of ice cores cave speleothems and marine carbonates copyright 2008 john wiley sons ltd

late holocene isotope hydrology of lake qinghai ne tibetan plateau effective moisture variability and atmospheric circulation changes a sub centennial resolution record of lacustrine carbonate oxygen isotopes 18oc from the closed basin lake qinghai on the ne tibetan plateau shows pronounced variability over the past 1500 years changes in 18oc in hydrologically closed lakes are often interpreted in terms of changing effective moisture under this interpretation our record would imply increasing effective moisture during the little ice age lia compared to the medieval warm period mwp however independent evidence from other archives strongly suggests the asian summer monsoon was stronger during the mwp and weakened during the lia controls other than effective moisture the balance of water inputs over evaporative loss must therefore have contributed to the 18oc values we propose the lia signal in lake qinghai resulted from a reduction in evaporation caused by colder air temperatures coupled with a decrease in oxygen isotope composition of input waters as a result of an increase in the relative importance of westerly derived precipitation our results caution against simplistic interpretations of carbonate oxygen isotope records from hydrologically closed lakes and suggest all possible controlling factors must be taken into account in order to avoid misleading palaeoclimatic reconstructions

summer temperature reconstruction on the central tibetan plateau during 1860 2002 derived from annually resolved ice core pollen 1 we present a 140 year ice core pollen record with annual time resolution from the puruogangri ice field in the central tibetan plateau a linear regression model between the sum of the steppe and meadow pollen taxa and summer temperature at naqu accounts for 66 of the summer temperature variance for the period 1955 2002 on the basis of this model we reconstructed summer temperature history for the central tibetan plateau from 1860 to 2002 three marked warm periods during the 1870s 1890s and 1990s and five cold periods during the 1860s 1880s 1900s 1950s and 1960 1970s were identified within the last 100 years late 20th century warming is distinctive and may have had a major role in the present retreat of most glaciers on the tibetan plateau the pollen record is also significantly correlated with average annual temperatures over the whole tibetan plateau suggesting that these proxy data have the potential for reflecting large scale regional temperature change the statistically significant similarity between the puruogangri ice core pollen record and the 18o time series indicates that both are reliable indicators of temperature change at annual to multiyear timescales in this region

basin dimensions and morphology as controls on amplification of tidal motions the early miocene north hungarian bay following the late aquitanian sea level fall tide influenced deposition started in the north hungarian bay an embayment in the paratethys open to the north east the relatively narrow funnel shape of the bay supported amplification of tidal movements resulting in the generation of strong tidal currents the length and the depth of the north hungarian bay and the connecting seaway through east slovakia fell into the tidal amplification window and thus fulfilled the conditions needed for resonant amplification of semidiurnal m2 tides tide influenced deposits were formed at both sides of the north hungarian bay they reflect dominant currents in opposite directions and of different strengths at either side of the basin this difference was the result of bottom tide interactions cyclonic anticlockwise residual currents were induced above the asymmetrical central depression in the bay and were superimposed upon the tidal currents producing an anticlockwise time and velocity asymmetrical current system the north hungarian bay and other examples show that amplification of tidal motions and formation of tide influenced deposits may occur if basin dimensions pass through the tidal amplification window this window represents ideal conditions for resonant or amphidromic amplification of tidal currents it determines an ideal length depth or width depth ratio relative to the wavelength of the astronomical tides thus signs of strong tidal influence in fossil basin fills can be used to reconstruct the dimensions length depth and width of such basins

holocene east asian monsoon variation inferred from species assemblage and shell chemistry of the ostracodes from hulun lake inner mongolia a sediment core from hulun lake inner mongolia was analyzed for species assemblages and shell chemistry of ostracodes to investigate changes in the hydrology and climate of the east asian summer monsoon margin during the holocene darwinula stevensoni was abundant ilyocypris spp scarce littoral ostracodes absent and mg ca sr ca and 18o were low 11 100 to 8300 yr ago indicating high lake levels and cool fresh waters darwinula stevensoni declined largely ilyocypris spp throve littoral ostracodes were rare and chemical indicators remained in low values 8300 to 6200 yr ago suggesting that the lake continued high stands but water became warm the lake then contracted and water became cool brackish 6200 to 4300 yr ago littoral ostracodes flourished 4300 to 3350 yr ago marking the lowest lake levels of the entire holocene the lake level recovered and water salinity decreased 3350 to 1900 yr ago from 1900 to 500 yr ago the lake maintained the preceding status albeit lowered stands and increased salinities 1100 to 800 yr ago during the recent 500 yr the lake expanded and water salinity decreased the data imply that the east asian summer monsoon did not intensify until 8300 yr ago and weakened dramatically 4300 to 3350 yr ago

a 2700 year high resolution pollen record of climate change from varved sugan lake in the qaidam basin northeastern tibetan plateau abstract a 2700 year high resolution pollen record from annually varved sugan lake in the qaidam basin at 2793 m a s l was obtained to examine vegetation and climatic change on the ne tibetan plateau pollen data shows that sugan basin was constantly covered by open desert steppe vegetation dominated by chenopodiaceae artemisia poaceae and ephedra however large variations in artemisia chenopodiaceae a c ratios suggest regional moisture fluctuations over the last 2700 years including a dry and relatively stable climate prior to 300 ad relatively wet climate from 300 to 1200 ad with variability during 1100 1200 ad and unstable climate since 1200 ad with relatively moister climate during 1250 1400 ad and 1700 1800 ad however other proxies varve thickness chironomid taxa isotopes of oxygen in precipitated carbonate show fresher water when regional moisture was lower inferred from a c ratio this inconsistency suggests the possible difference of in lake lithology environment and regional moisture change fresh water into the lake from ice melting on the surrounding mountains might have contributed to the in lake lithology and environment variation the effective moisture changes in the basin are in opposite phases to snow accumulation records from dunde ice core 5325 m a s l and to the monsoon intensity inferred from dongge cave suggesting that the regional topography might have played an important role in mediating moisture changes at regional scale pollen data from sugan lake shows the shift of moisture at 1200 ad from stable to variable conditions this event is well correlated with other paleoclimate proxies in china and other parts of the world however the mechanisms behind these patterns require further investigation

late pleistocene paleoclimatic history documented by an oxygen isotope record from carbonate sediments in qarhan salt lake ne qinghai tibetan plateau late pleistocene paleoclimatic variability on the northeastern qinghai tibetan plateau ne qtp was reconstructed using a chronology based on ams 14 c and 230 th dating results and a stable oxygen isotopic record these are derived from lake carbonates in a 102 m long qarhan sediment core isl1a collected from the eastern qaidam basin previous research indicates that the d 18 o values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water which in turn is a function of regional p e balance and the proportion of precipitation that is monsoon derived on the ne qtp modern isotopic observations indicate that the d 18 o values of lake carbonates in hyper arid qaidam basin are more positive during the warm and wet period due to strong evaporation and continental effect in this basin the positive d 18 o values in the arid region indicate drier climatic conditions based on this interpretation and

a lateglacial and holocene lake record from the nianbaoyeze mountains and inferences of lake glacier and climate evolution on the eastern tibetan plateau abstract our 12 81 m long record from lake ximencuo provides insight into the lateglacial and holocene evolution of the lake and the nianbaoyeze glacier in its catchment and the regional climate history since 19 kyr lake ximencuo was a permanent deep lake throughout its history in contrast to numerous lakes on the tibetan plateau which experienced shallow lake levels or even desiccation during the lateglacial lake ximencuo was fed by large quantities of meltwater in the lateglacial the existence of glaciated upper catchment areas is apparently a prerequisite for lakes on the tibetan plateau which maintained relatively high water levels during the generally cold and dry periods following the global lgm 21 kyr a minor re advance of the nianbaoyeze glacier was recorded coeval with the greenland stadial 2a 16 4 and 14 5 kyr followed by rapid warming apparently synchronous with the greenland interstadial 1 warmest conditions were recorded at lake ximencuo during the early holocene which was punctured by a remarkable pulse of climate deterioration around 8 3 kyr this spell represents probably the 8 2 kyr event of the north atlantic region suggesting that it had a significant impact on the tibetan plateau colder conditions of longer duration occurred from 4 7 to 3 7 kyr apparently in phase with numerous records signalling colder and drier conditions on the tibetan plateau two minor spells of colder conditions and probably catchment erosion were recorded in the late holocene between 2 0 and 1 4 kyr and between 0 5 and 0 1 kyr with the latter representing the little ice age it is unclear whether human activities may have accelerated or even solely triggered the late holocene erosion events

effect of land use and urbanization on hydrochemistry and contamination of groundwater from taejon area korea abstract taejon metropolitan city located in the central part of south korea has grown and urbanized rapidly the city depends heavily on groundwater as a water resource because of ubiquitous pollution sources the quality and contamination have become important issues for the urban groundwater supply this study has investigated the chemical characteristics and the contamination of groundwater in relation to land use an attempt was made to distinguish anthrophogenic inputs from the influence of natural chemical weathering on the chemical composition of groundwater at taejon groundwater samples collected at 170 locations in the taejon area show very variable chemical composition of groundwater e g electrical conductance ranges from 65 to 1 290 s cm most groundwater is weakly acidic and the groundwater chemistry is more influenced by land use and urbanization than by aquifer rock type most groundwater from green areas and new town residential districts has low electrical conductance and is of ca hco 3 type whereas the chemical composition of groundwater from the old downtown and industrial district is shifted towards a ca cl no 3 so 4 type with high electrical conductance a number of groundwater samples in the urbanized area are contaminated by high nitrate and chlorine and exhibit high hardness the epco 2 that is the co 2 content of a water sample relative to pure water was computed to obtain more insight into the origin of co 2 and bicarbonate in the groundwater the co 2 concentration of groundwater in the urbanized area shows a rough positive relationship with the concentration of major inorganic components the sources of nitrate chlorine and excess co 2 in the groundwater are likely to be municipal wastes of unlined landfill sites leaky latrines and sewage lines chemical data of commercial mineral water from other jurassic granite areas were compared to the chemical composition of the groundwater in the taejon area factor analysis of the chemical data shows that the hco 3 and no 3 concentrations have the highest factor loadings on factor 1 and factor 2 respectively factors 1 and 2 represent major contributions from natural processes and human activities respectively the results of the factor analysis indicate that the levels of ca 2 mg 2 na cl and so 4 2 derive from both pollution sources and natural weathering reactions

quantifying closed basin lake temperature and hydrology by inversion of oxygen isotope and trace element paleoclimate records lake systems are important paleoclimate archives that preserve ecosystem and hydrologic responses to critical periods in earth history such as carbon cycle perturbations and glacial interglacial cycles geochemical measurements of biogenic carbonate for example 18o 13c 87sr 86sr li u sr and mg are indicators of hydrologic variability in lake systems throughout the geologic record in this study we present a new closed basin lake modeling approach hybim the hydrologic balance inverse model that employs a system of total differential equations and uses the measured 18o sr ca and mg ca of biogenic carbonate to determine changes in temperature runoff and lake evaporation using equally spaced time steps these equations are simultaneously solved to constrain the hydrologic parameters of the lake as recorded in biogenic carbonate we use a monte carlo approach to account for uncertainty in the input parameters such as 18o temperature relationships partition coefficient uncertainty and watershed solute chemistry for illustrative purposes we apply the model to two ostracod valve datasets covering different timescales 1 the cretaceous songliao basin northeast china and 2 holocene lake miragoane haiti modern water measurements of water isotopes and cation concentrations from each location are required as model inputs we compare our modeling results with author interpretations and geologic observations the modeling approach presented in this study can be applied to other closed basin lake records can be modified for other calcifying species for example gastropods or mollusks or with calibration to inorganic lacustrine carbonate in addition this approach holds promise for extension with additional proxy measurements that is d u ca or li ca and changing source area on tectonic timescales using proxies that reflect changing source lithology that is sr and pb isotopes future incorporation of age model uncertainty in the monte carlo approach will also provide utility by quantifying temporal uncertainty on the hydrologic response recorded by lake sediments

fluid flow vs scale of shear zones in the lower continental crust and the granulite paradox the external or internal origin of co2 and h2o in marbles and metabasites from a large scale granulite section is related to their structural setting outside shear zones within major shear zones 25 km wide by 340 km long or within minor shear zones 10 km wide by 150 km long outside shear zones marbles have isotopic compositions similar to their protholiths values and metabasites record mantle 13c signatures marbles from major shear zones show little variation of 18o but are depleted in 13c down to 3 due to exchange with mantle derived carbon in addition to an earlier input of mantle carbon related to mafic magmatism major shear zones act as conduits for mantle carbon influx they are probably mantle rooted oxygen was buffered by the crust marbles and their related skarns from minor shear zones were subjected to devolatilization reactions and water rich infiltration from crustal sources with no evidence for a mantle carbon contribution large isotopic variations at the metre scale in the shear zones reflect the heterogeneous distribution of fluid flow associated with heterogeneous deformation and contrasting petrologic features and permeabilities these geochemical structural relationships reconcile the conflicting arguments on the origin of fluids during granulite genesis

geochemical evolution of ground water in smith creek valley a hydrologically closed basin in central nevada u s a abstract smith creek valley is a hydrologically closed basin in which ground water is recharged by subsurface inflow from sorrounding mountains and infiltration of streamflow into alluvial fan deposits near the mountains ground water is discharged by evapotranspiration from shallow ground water areas in the central part of the basin dominant ions in the dilute recharge water are na ca and hco 3 dissolved solids concentration increases during flow through the basin fill sediments with na becoming increasingly dominant in the discharge area a bare soil playa sorrounded by phreatophytic vegetation ground water salinity dominated by na and cl increases markedly the main processe controlling geochemical evolution of ground water in the basin fill aquifer were identified using major ion chemistry mass balance calculations thermodynamic calculations stable isotopes and mineral identification these processes are 1 dissolution of volcanic tuff and tuff derived basin fill deposits 2 cation exchange of ca and mg in the water for na in clay minerals 3 weathering of plagioclase to montmorillonite 4 precipitation of zeolite minerals 2 concentration of dissolved constituents by evapotranspiration 6 dissolution of cl and so 4 evaporative salts 7 precipitation of calcite

circulation and sedimentation in a tidal influenced fjord lake lake mckerrow new zealand lake mckerrow is a tide influenced fjord lake separated from the open sea by a holocene barrier spit fresh oxygenated waters of the epilimnion overlie saline deoxygenated waters of the hypolimnion during winter water from the upper hollyford river interflows along the pycnocline depositing coarse silt on the steep delta and transporting finer sediment down lake an extensive sub lacustrine channel system on the foreset delta slope is possibly maintained by turbidity currents saline waters of the hypolimnion are periodically replenished during high tides and low lake levels saline water flows into the lake and downslope into the lake basin as a density current in a well defined channel

alkenone based reconstruction of late holocene surface temperature and salinity changes in lake qinghai china china the alkenone temperature proxy u k 0 37 indicates up to a 1 c change in mean annual air temperature or a 2 c change in summer lake water temperature during the late holocene oscillating warm and cold periods could be related to the 20th century warm period the little ice age the medieval warm period the dark ages cold period and the roman warm period the relative importance of c37 4 alkenone to total c37 alkenone production c37 4 fluctuated between 15 45 with higher values during warm periods suggesting that lake water was also fresher during these periods the coupled late holocene surface temperature and salinity changes suggest that asian monsoons strongly influenced the climate of the lake qinghai region citation liu z a c g henderson and y huang 2006 alkenone based reconstruction of lateholocene surface temperature and salinity changes in lake qinghai china geophys res lett 33 l09707 doi 10 1029 2006gl026151

basin morphology and seismic stratigraphy of lake donggi cona north eastern tibetan plateau china basin morphology and depositional stratigraphy of lake donggi cona on the north eastern tibetan plateau has been studied with echo depth sounding and shallow seismic sub bottom profiling the basin is a pull apart structure situated at the highly active kunlun fault it is characterised by a 92 m deep graben structure in the western part of the lake basin and a shallow eastern lake part the latter filled up with fluvial sediments from a large alluvial plain three prominent morphological levels were identified at 24 m 39 m and 57 m below present lake level they were partly created by basin subsidence while the deposition of prograding delta sediments primarily formed the morphological steps the inherited tectonic structures control on going neotectonic activity which seems to have only minor influence on present basin morphology the basin is filled by sediments of at least 30 m thickness in the depocentre three major depositional units can be distinguished in comparison with lithological changes in a sediment core they give evidence of pronounced lake level fluctuations and dramatic changes in lake volume a numerical age datum of w19 cal ka bp at the base of the sediment core allows a tentative reconstruction of late glacial to holocene lake development a very low base level preceded a time of delta formation during higher lake level i e w26 m lower than present during last glacial maximum creating a lake of only 18 of its present size at the transition to holocene the lake level rose very quickly changing to a deep lake environment thus transgression may have promoted maximum lake stands

holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in china a review and synthesis there has been much recent debate about holocene climate variation in the monsoon region of china especially the temporal pattern of variations in precipitation the time transgressive nature of the holocene precipitation maximum and the extent to which variations in regions influenced by the indian summer monsoon ism and the east asian summer monsoon easm have been synchronous we summarize and compare carbonate oxygen isotope records delta o 18 carb from ten lakes within the present day ism region we discuss their paleoclimate significance considering the present day moisture source isotopic composition of precipitation and the hydrological setting the delta o 18 carb records are controlled mainly by the isotopic composition of lake water which in turn is a function of regional precipitation evaporation p e balance and the proportion of precipitation that is monsoon derived we normalized the delta o 18 carb data and used these records to generate an integrated moisture index this index along with oxygen isotope records from speleothems and carbon isotope records delta c 13 org from peats within the monsoon region suggests that holocene climate was broadly synchronous across the monsoon region and within the limits of accuracy of the existing age models provides no strong evidence for previously proposed anti phasing of the ism and the easm stable isotope records from lake sediments and peat bogs have excellent potential for providing high quality paleoclimate data for monsoon asia and complement high resolution speleothem sequences which are only found in certain localities c 2011 elsevier ltd all rights reserved

oxygen isotopes in meteoric calcite cements as indicators of continental paleoclimate because meteoric water 18 o values decrease with decreasing ambient temperature and increasing latitude 18 o values of meteoric calcite cement should exhibit a similar relation with paleolatitude and be an indicator of continental paleotemperatures to test this we compiled isotopic and paleolatitude data for 20 meteoric cements and nine speleothems ranging in age from devonian to modern and in paleolatitude from 3 5 to 83 mean 18 o values for meteoric cements and speleothems both show the same negative correlation with paleolatitude the 18 o vs latitude trend for these carbonates is almost identical to that predicted for modern inland environments but differs from the trend for coastal environments this suggests that the ground water controlling the ultimate composition of meteoric cement is derived predominantly from inland recharge if it is assumed that the modern meteoric water 18 o vs temperature relation is valid for the past and that insignificant evaporation occurred prior to carbonate precipitation then coastal and inland paleotemperatures can be calculated from the 18 o values of meteoric calcite 18 o mcl and seawater 18 o sw by using the equations t coastal 13 3 32 6 0 231 0 0613 18 o mcl 18 o sw and t inland 17 8 16 2 0 572 0 1233 18 o mcl 18 o sw where t is temperature in c calcite precipitated from coastal meteoric water at temperatures between 0 and 25 c will exhibit a narrow range in 18 o 6 to 4 where 18 o sw 0 the 18 o of calcite precipitated from inland meteoric water will be sensitive to paleotemperature ranging from 14 to 5 where 18 o sw 0 for temperatures of 0 to 25 c

li ca ratios of ostracod shells at lake qinghai ne tibetan plateau china a potential temperature indicator acquiring continuous and high resolution natural records in recent 2 000 years is the hot issue in the palaeoclimate research recent studies revealed that li ca and mg li ratio of carbonate is a potential tracer of past environmental changes in the oceans and is seldom applied for palaeoclimate reconstruction in lakes to make full understanding of the potential of li ca ratios of carbonates in lakes li ca ratios of monospecific ostracod shell eucypris inflate with similar size in the lacustrine sediment core from lake qinghai ne tibetan plateau have been analysed for the first time single species can effectively avoid the interspecies effects in combination with the sedimentation rate that existed data derived from 210pb and 137cs downcore variations of li ca ratios of ostracod shells during the past 800 years in lake qinghai have been reconstructed successfully by comparing li ca ratios and temperature inferred from meteorological records and tree ring widths in dulan and qilianshan in adjacent regions li ca ratios of ostracod shells negatively correlate with temperature higher temperature corresponds with lower li ca ratios and vice versa indicating that li ca ratio of ostracod shells is an effective indicator for temperature variations therefore ongoing in depth investigation using li ca ratios of carbonates in more lakes to further reveal its palaeotemperature implications would be deserved

the nature of miocene amazonian epicontinental embayment high frequency shifts of the low gradient coastline a sedimentological and ichnological data set that covers the lower upper miocene sedimentary series of western amazonian foreland basin indicates that widespread restricted marine ingressions shaped western amazonia throughout the miocene the late lower early upper miocene sedimentary series pebas formation consists of stacked 3 to 10 m thick tidally influenced brackish to freshwater bay margin sequences the overlying upper miocene post pebas strata bear tidally influenced low salinity channel deposits that are interbedded with continental deposits the data suggest that several tens of high frequency ingressions reached the basin during the miocene the ingressions were shallow and restricted and were interspersed with rapid progradation along with the prograding shorelines the continental environments swamps lagoons floodplains and forests constrained the extent of the marginal marine embayment consequently the miocene marginal marine and continental strata are closely interbedded throughout the basin these results refine the recent depositional models for miocene amazonia and challenge the theory that marine ingressions shaped the area only during one brief time interval late middle early late miocene during the epoch much of recent literature has documented fossils of mangrove pollen brackish euryhaline fish and brackish water ostracods brackish water trace fossil assemblages and tidal deposits from various miocene stratigraphic levels commonly these data sets are collected from the same outcrops as those for which data sets imply freshwater conditions we propose that these seemingly contrasting data sets can be unified if the repetitive nature of the ingressions is considered and all the paleoenvironmental data are presented in a detailed lithological and stratigraphical context

origin of the high variability of water mineral content in the bedrock aquifers of southern madagascar this study assesses the causes of the high spatial variability of the mineral content of groundwater in crystalline bedrock of southern madagascar although many kilometres from the coast and at a mean altitude of 400 m a s l wells drilled in this area produce water with electrical conductivities in the range of 300 30 000 mu s cm 1 with a high spatial variability chemical and isotopic data are used to identify the processes involved in the groundwater mineralization it is shown that the chemical composition of the groundwater in this region has its origin in i normal silicate and carbonate weathering reactions and ii input of marine salts probably via rainfall recharge modified by evapo concentrative processes probably including precipitation and re dissolution of secondary evaporites in the unsaturated zone to obtain a better understanding of the spatial salinity distribution well parameters such as yields weathered zone thickness weathered materials and morphological positions upper slope mid slope lower slope or valley bottom are scrutinized a correlation was found between high salinity and low flow shallow groundwater environments flat hill tops valley bottoms weakly developed and clayey weathered zones and between low salinity and high flow environments granular well developed weathered zones and situation on valley slopes

lake qinghai china closed basin like levels and the oxygen isotope record for ostracoda since the latest pleistocene abstract in 1985 a sino swiss limnogeological expedition to china s largest inland lake recovered seismic profiles and piston cores to help calibrate palaeoclimatic models of monsoon and insolation fluctuations over the northern tibet qinghai plateau since the last glacial maximum lake qinghai a perennial lake with an area of 4278 km2 1985 at 3194 m above sea level receives drainage from 30 000 km2 of catchment near the northwest corner of the plateau the 26 5 m deep terminal lake 1985 with brackish alkaline magnesium sulphate rich waters 14 g 1 1 tds has not overflowed since the last glacial but its levels have responded to climatic and hydrologic changes seismic reflection profiles for the sub bottom sediment structures revealed a complex topography with channels relict terraces tectonic tilting and deformation in deposits buried under a 4 6 m packet of mainly flat bedded sediments from which core samples were recovered the lowermost cored material 14 500 yr b p comprises mainly water lain loess deposited in a smaller flood plain lake of up a few metres depth under cold arid climatic conditions ams radiocarbon dating indicates average sedimentation rates for latest pleistocene and holocene deposits in central basin regions of 0 3 0 5 mm yr 1 the 18o values of fossil ostracod valves provide a record of changes in the isotopic chemistry of the lake waters that can be related to the precipitation evaporation budgets which have controlled the palaeo levels for lake qinghai the precipitation evaporation budget for the lake qinghai region is largely determined by the asian monsoon system the lake qinghai sediment record shows that there was no large influx of glacoer melt waters into the lake basin during the post glacial the regional climate remained arid until at least 12 500 yr b p when an incipient monsoon was possibly initiated river transported silts first reached the basin centre at 11 800 yr b p when the lake depth may have increased to 5 m possibly a monsoonal weakening for several centuries after 10 800 yr b p europe younger dryas caused a further period of aridity at 10 200 yr b p the basin began filling towards modern lake dimensions in response to a permanent strengthening of the asian monsoon substantial lake level rises probably characterised the periods 10 200 9800 9500 8500 8300 7200 yr b p and through perhaps a century at about 6800 yr b p decreasing levels probably characterised the intervening intervals short term lake level fluctuations through the mid holocene climatic optimum were minimal indicating a very stable climatic hydrologic regime an isotopic steady state for the lake waters since 3000 500 yr b p obscures the climatic hydrologic regime dependent 18o gradient but there is little stratigraphic evidence to suggest that the lake level has been significantly below its present level since that time three negative 18o excursions for the lake waters may correspond to known glacier advances on the plateau at 3000 2000 and 1500 yr b p during china s neoglacial

late pleistocene paleolake evolution in the hetao basin inner mongolia china abstract the paleolake that once existed in the hetao basin china represents an important stage of the yellow river drainage system evolution in the region but it has not been studied in detail to date in particular the formation and driving forces of the paleolake evolution since the late pleistocene is still poorly understood in this study optically stimulated luminescence and radiocarbon dating were combined with multiproxy analysis of lacustrine sediments in the central hetao basin to reconstruct the paleolake evolution proxies included carbonate 18 o and 13 c isotopes grain size magnetic susceptibility and color in combination with stratigraphic records the proxies indicated the existence of a lake environment in the hetao basin between 150 and 18 ka bp the paleolake between 150 and 130 ka bp was an open system between 130 and 54 ka bp the paleolake basin closed with high lake levels at the beginning of the period and then a gradual decrease after 54 ka bp the paleolake began to outflow and gradually shrank in size and after 18 ka bp an alluvial fan covered the region and the paleolake disappeared we propose a combination of tectonic uplift and climate changes as the main drivers of paleolake formation and evolution since the late pleistocene

a 1700 year n alkanes hydrogen isotope record of moisture changes in sediments from lake sugan in the qaidam basin northeastern tibetan plateau we present a hydrogen isotopic record of long chain n alkanes in lake sugan to reconstruct regional moisture changes in the last 1700 years at a sampling resolution of 25 years the d values decreased by over 30 from the medieval warm period mwp c ad 600 1500 to the little ice age lia c ad 1500 1850 and indicated that the moisture pattern included a relatively humid climate before the mwp becoming drier overall in the mwp wetter in the lia and then tending towards drought in the post industrial era in the study region chenopodiceae shrubs were more abundant in dry climates than in wet meanwhile d values of shrubs were more positive than those of grasses therefore we suggest that the vegetation type shrub or grass which depends on moisture changes is the controlling factor for d variations in lake sugan

intra annual variability in the heavy metal geochemistry of ground waters from the deccan basaltic aquifers of india geochemical baseline geogenic anthropogenic and background geogenic levels of heavy metals in the ground waters from basaltic aquifers of deccan volcanic province of india depicted intra annual variability on spatial scale classified into group i fe mn zn pb and group ii mo ni cr cu metals depicted contrasting enrichment and depletion patterns seasonally attributable to geologic controls and water table fluctuations while fortification in mo ni in post monsoon high water table is on account of combined lithogenic anthropogenic contributions pre monsoon augmentation in fe mn low water table is entirely lithogenic positive values of normalised difference dispersal index replicates the dominant role of soil vadose zone as a chief supplier of metals to the groundwater during post monsoon while negative figures recommend host rock as a primary source of accretion of metals in pre monsoon higher ni cr ratios for wells in alluvial aquifer fertile agriculture plain than the basaltic and dyke aquifers further suggest enhanced input of the elements mo ni cu from soil and agriculture land use in post monsoon season values of ni cr ratio above unity for majority of the wells in post monsoon and nearly 50 wells in pre monsoon suggest privileged weathering of olivine followed by pyroxene plagioclase feldspar ni cr 1 as a major cause of heavy metal load to the groundwater pearson correlation coefficients authenticate these inferences by means of elemental associations the study unveils multi source derivation of heavy metals related to seasonal fluctuation in the water table conditions leading to range of heavy metals in the groundwater from the study area the target hazard quotient thq values of heavy metals closer to unity and above unity highlight the possible health risk hazard associated with the consumption of metal contaminated groundwater the study thus highlights the importance of baseline geochemical mapping to assess the state of near surface environment as heavy metals are closely linked to human health

general characteristics of temperature variation in china during the last two millennia three alternate china wide temperature composites covering the last 2000 years were established by combining multiple paleoclimate proxy records obtained from ice cores tree rings lake sediments and historical documents five periods of temperature variation can be identified a warm stage in ad 0 240 a cold interval between ad 240 and 800 a return to warm conditions from ad 800 1400 including the medieval warm period between ad 800 1100 the cool little ice age period between 1400 1920 and the present warm stage since 1920 regional temperature variation is found during ad 800 1100 when warm conditions occurred in eastern china and in the northeastern tibetan plateau and in ad 1150 1380 when the southern tibetan plateau experienced a warm interval in contrast evidence for cool conditions during the lia is more consistent among the proxy records the temperature reconstructions for china and the northern hemisphere show good agreement over the past millennium

paleogeography of miocene western amazonia isotopic composition of molluscan shells constrains the influence of marine incursions strontium oxygen and carbon isotope compositions of well preserved mollusks bivalves indicate a dominantly freshwater depositional setting for the lower miocene upper miocene pebas formation in western amazonia molluscan 87sr 86sr ratios identify different freshwater sources andean runoff was the dominant water source in miocene western amazonia though there was occasional influx of waters from cratonic catchments at only one stratigraphic level isotope signals indicate increased mesohaline aquatic salinities in concert with a clearly more saline molluscan faunal assemblage strontium isotope based salinity estimates are surprisingly low when compared to other paleosalinity estimates based on the interpretation of ichno faunal assemblages and sedimentological structures we propose that these seemingly contrasting observations can be unified if miocene western amazonia was occupied by a long lived lacustrine wetland system with a restricted connection via the los llanos basin to the caribbean sea abundant runoff supplied fresh water to this system which effectively blocked the influx of saline waters through the restricted marine connection to the north much like modern lake maracaibo such a system could have been the site of microtidal currents and thus could have hosted brackish water fauna in a dominantly freshwater depositional system

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

hydrochemical characteristics of aquifers near sutherland in the western karoo south africa the western karoo depends entirely on groundwater for domestic and agricultural use an understanding of the chemical evolution of the groundwater provides insight into the interaction of water with the environment and contributes to better resource management descriptive statistics correlation matrices and factor analysis together with stable isotope data were used to gain an understanding of the hydrochemical processes of the groundwaters in the fractured rocks around sutherland in the western karoo the main processes influencing the groundwater chemistry are salinisation mineral precipitation and dissolution cation exchange and human activity the stable isotope data indicate that the infiltration of evaporated water is partly responsible for the occurrence of saline subsurface waters the ionic oxygen and hydrogen stable isotope composition of the groundwaters suggests that the effects of localised topography are one of the overriding factors controlling the groundwater chemistry in higher lying areas ca hco3 2 type waters are prevalent while in topographical flat areas nacl type waters dominate in areas where water collects close to or at the surface saline soils are formed from these areas salts are leached to the subsurface during significant recharge periods these findings are important in that they contribute to the identification of suitable locations for developing groundwater resources that could yield a relatively better quality water q 2001 elsevier science b v all rights reserved

paleoclimatic implications of an 850 year oxygen isotope record from the northern tibetan plateau oxygen isotope records from the sediments of hydrologically closed lakes are commonly interpreted in terms of changing effective precipitation we compare an 850 year long oxygen isotope record derived from ostracode carbonate from the sediments of sugan lake in the northern tibetan plateau with tree ring and ice core evidence for changing temperature precipitation and isotopic composition of the lake s inflow taking into account all of these independent records we show that variations in the carbonate delta o 18 values could not have been the result of varying effective precipitation alone changes in water temperature and in the delta o 18 of source waters also played a significant role where independent records of temperature precipitation or the isotopic composition of input waters are unavailable care should be taken to avoid simplistic interpretations of carbonate stable isotope records as these may contribute to incorrect paleoclimatic reconstructions

forcing of the asian monsoon on the tibetan plateau evidence from high resolution ice core and tropical coral records 1 climatic influences on snow accumulation across the tibetan plateau are examined using records of net snow accumulation an and oxygen isotopic ratios 18o since 1801 from two ice cores from opposite sides of the plateau from 1880 to the 1990s summer monsoon precipitation has been a significant component of the annual accumulation on the dasuopu glacier in the himalayas but during the latter part of the little ice age 1810 to 1880 total an was 30 higher than the summer monsoon amounts in northern india this was possibly the result of increased early winter snowfall as westerly low pressure systems linked to the north atlantic pushed farther east along the himalayas than they normally do today the decades of high accumulation and the colder temperatures allowed excess snow and ice to persist late into each year which may have weakened the subsequent asian summer monsoon consequently precipitation in the northeast tibetan plateau where the dunde ice cap is located may have been affected primarily by eurasian continental processes rather than tropical meteorology during this time since the onset of the recent warming over the last century the south asian summer monsoon intensified and influenced summer climate farther to the north and west and expressions of tropical pacific and indian oceanic atmospheric processes are noticeable in the dunde net accumulation record the dunde and dasuopu glaciers which are located on the northern and southern rims of the tibetan plateau were situated in regions of environmental transition as the northern hemisphere climate shifted from a neoglacial to a warming climate mode which is something to consider when interpreting the longer ice core climate records

late holocene coupled moisture and temperature changes on the northern tibetan plateau the northern tibetan plateau involves complex interactions between the mid latitude westerly circulation and the subtropical asia monsoon circulation acting as a bridge communicating high and low latitude climatic processes previous studies from the region suggest relatively wet conditions in cold periods during the late holocene for instance the little ice age lia however the inference of such temperature moisture association is subject to the large uncertainty in lacustrine 14c chronology due to the particularly large lake reservoir effect in the region here we take a different approach by reconstructing paired temperature and moisture records from the same sediment cores to assess the temperature moisture association independent of chronology uncertainty we use alkenone indices uk 37 and c37 4 to reconstruct high resolution temperature and moisture changes simultaneously from two lakes in the qaidam basin northern tibetan plateau over the last 2500 years characterized by marked climatic variability our paired records confirm the warm dry and cold wet association in arid northwestern china during the late holocene opposite to the warm wet and cold dry association in subtropical asian monsoonal regions our moisture records further suggest substantially drier conditions during the medieval warm period mwp than the current warm period lastly the temperature and moisture changes inferred from our records can be well correlated with solar irradiance changes suggesting a possible link between solar forcing and natural climate variability during the late holocene on the northern tibetan plateau

miocene fish faunas from the northwestern amazonia basin colombia peru brazil with evidence of marine incursions new evidence indicates marine influences during the miocene in the northwestern amazonia basin this is the first major survey of the ichthyofauna from this area in the miocene fossil fish remains from taxa such as the dasyatoidea myliobatoidea characiformes siluriformes and sciaenidae are found conspicuous finds were two pharyngeal teeth of stephanodus minimus a species that so far had only ever been found in late cretaceous sediments the fish remains of freshwater brackish and marine taxa are deposited together throughout the area this is thought to be related to marine influences during the miocene these finds agree with earlier studies that suggest episodic marine influences which most likely lasted up to the late miocene and disagree with studies that suggest a connection between the atlantic and the caribbean sea over the south american continent the ichthyofaunas also indicate a warm climate as well as shallow and possibly torrential waters c 1998 elsevier science b v all rights reserved