climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

u th dating of freshwater travertine from middle velino valley central italy paleoclimatic and geological implications abstract six travertine bodies outcropping along the middle velino valley central italy have been studied and dated using the u th method in order to obtain new chronological constraints for the recent geological evolution of the area the lithological and sedimentological characteristics of travertines have been described showing that such deposits can be referred to waterfall pool terraces and gentle slopes environment travertines have formed during warm periods and can be referred to marine oxygen isotope stages 5 3 and 1 travertine deposition seems to stop around 5 ka bp according to other european and italian sites pollen stratigraphy and ostracod assemblages from the close sequence of valle di castiglione characterized by the same climatic conditions of velino valley have confirmed that periods of velino valley travertine deposition were effectively characterized by warm and wet climatic conditions seismic activity strongly active in the area since the middle pleistocene has deeply influenced the location and the discharge of springs which have deposited the travertines influencing in turn the shape and size of travertine bodies

geochemical characteristics of fluoride in groundwater of gimcheon korea lithogenic and agricultural origins the occurrence of fluoride in groundwaters can be influenced by many factors in korea the fluoride rich groundwaters are normally associated with rock types especially granite and gneiss in gimcheon high fluoride groundwaters up to a maximum of 2 15 mg l were observed with bimodal distribution of concentrations the groundwater in this area showed relatively high concentrations of anthropogenic chemicals such as nitrate chloride and sulfate statistical analysis showed that fluoride is positively correlated with ph alkalinity sodium and lithium indicating that the interaction with granite is the main cause enriching its concentration in gimcheon 18o data of groundwater showed a negative correlation with nitrate and can be used as an indicator of groundwater age the four samples of fluoride rich groundwater were plotted in the light d and 18o region showing that they were the result of long water rock reaction however other groundwater with a low fluoride concentration was evenly distributed throughout all d and 18o ranges and did not show a statistically significant correlation with nitrate indicating possible mixing with another source of fluoride considering the influence from the surface on the geochemical characteristics of groundwater in this area anthropogenic sources including phosphate fertilizer containing fluoride and pesticides may also have partly contributed to the concentrations of fluoride in the low fluoride groundwater the scattered distribution of fluoride rich groundwater and the significant correlation with lithium suggest that pegmatite is the main rock type increasing fluoride concentration in this area

the quaternary glacial history of the lahul himalaya northern india this paper presents the first glacial chronology for the lahul himalaya northern india the oldest glaciation the chandra glacial stage is represented by glacially eroded benches at altitudes greater than 4300 m above sea level this glaciation was probably of a broad valley type the second glaciation the batal glacial stage is represented by highly weathered and dissected lateral moraines which are present along the chandra valley and some of its tributaries this was an extensive valley glaciation the third major glaciation the kulti glacial stage is represented by well preserved moraines in the main tributary valleys of the chandra valley this represents a less extensive valley glaciation two minor glacial advances the sonapani i and ii are represented by small sharp crested moraines which are within a few hundred metres or few kilometres of the present day glaciers the change in style and extent of glaciation is attributed to an increase in aridity throughout the quaternary due either to global climatic change or uplift of the pir panjal mountains to the south of lahul which restricted the northward penetration of the south asian summer monsoon 1996 john wiley sons ltd

radium isotopes alkaline earth diagenesis and age determination of travertine from mammoth hot springs wyoming u s a abstract travertine from active springs former vents and drill core from mammoth hot springs wyoming was analyzed for ra isotopes 226 ra 228 ra other alkaline earth elements mg sr ba and mineralogical composition thermal water also was analyzed travertine presently being deposited contains 3 0 15 3 pci g 226 ra and has a 228 ra 226 ra ratio identical to that in thermal water travertine precipitates mostly as aragonite and experiences a complete diagenetic transformation to calcite within 9 a estimated from 228 ra 226 ra value of youngest completely calcite travertine systematic compositional changes associated with this diagenetic transformation are enrichment of mg and depletion of sr ba and ra apparent mineral water distribution coefficients for mg sr and ba in aragonite and calcite are within the range of those determined experimentally implying near equilibrium conditions and high water rock ratios during travertine diagenesis impure travertine from near the base of the travertine section in the u s geological survey y 10 drill hole at 72 9 m depth has a 230 th 234 u isochron age of 7700 440a the content of 226 ra in normal subhorizontally layered porous travertine decreases with depth in y 10 the observed 226 ra vs depth relation is consistent with continuous deposition of travertine at the y 10 site from 7700 a bp to near present at a mean rate of 1 0 cm a and indicates minimal exchange of ra between travertine and pore water after the early diagenetic transformation of aragonite to calcite these data imply that under favorable conditions 226 ra measurements may be useful in determining ages and deposition rates for other travertines

occurrence and hydrogeochemistry of fluoride in alluvial aquifer of weihe river china fluoride f has significant impacts on human health high fluoride groundwater up to 1 90 mg l has been found in upper confined aquifer underlying the first terrace of weihe river during a hydrogeological investigation for water supply in 2005 to reveal the occurrence and hydrogeochemistry of high f groundwater hydrogeochemical tools such as saturation index ionic ratios and correlation analysis were used in this study the study shows that the concentrations of most physiochemical parameters from phreatic water influenced by intensive evaporation and anthropogenic activities such as unregulated sewage and excreta disposal and agricultural practices in the area are higher than those of confined water the f concentration in phreatic water is within the acceptable limits set by china and the world health organization who while that of upper confined water shows a decreasing trend northwestward as the weihe river approaches with f concentration in the first terrace beyond the national and the who standards high f groundwater is observed in alkaline environment associated with high na ph hco3 and low ca2 and mg2 the enrichment of f is controlled by geologic and hydrogeological conditions fluorine bearing minerals presented in alluvial formations and their dissolution precipitation under the alkaline environment along groundwater flow ion exchange human activities and the mixing of different recharge waters may influence the enrichment of f as well

hydrochemistry of groundwater gw and surface water sw for assessment of fluoride in chinnaeru river basin nalgonda district ap india hydrochemical studies were conducted in chinnaeru river basin of nalgonda district andhra pradesh india to explore the causes of high fluorides in groundwater and surface water causing a widespread incidence of fluorosis in local population the concentration of fluoride in groundwater ranges from 0 4 to 2 9 and 0 6 to 3 6 mg l stream water ranges from 0 9 to 3 5 and 1 4 to 3 2 mg l tank water ranges from 0 4 to 2 8 and 0 9 to 2 3 mg l for pre and post monsoon periods respectively the modified piper diagram reflects that the water belongs to ca2 mg2 hco3 to na hco3 facies negative chloroalkali indices in both the seasons prove that ion exchange between na and k in aquatic solution took place with ca2 and mg2 of host rock the interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water rock interaction is responsible for major ion chemistry of groundwater surface water high fluoride content in groundwater was attributed to continuous water rock interaction during the process of percolation with fluorite bearing country rocks under arid low precipitation and high evaporation conditions the low calcium content in rocks and soils and the presence of high levels of sodium bicarbonate are important factors favouring high levels of fluoride in waters the basement rocks provide abundant mineral sources of fluoride in the form of amphibole biotite fluorite mica and apatite

effects of glacial ice on subsurface temperatures of hydrothermal systems in yellowstone national park wyoming fluid inclusion evidence hydrothermal quartz and fluorite crystals containing liquid rich fluid inclusions coexisting vapor rich fluid inclusions were not observed were found in drill cores from eight relatively shallow research holes drilled by the us geological survey in and near major geyser basins of yellowstone national park homogenization temperatures t sub h for mostly secondary fluid inclusions show variations in temperature that have occurred at give depths since precipitation of the host minerals within major hydrothermal upflow zones fluid inclusion t sub h values all were found to be equal to or higher commonly 20 50 c and up to 155 c higher than present temperatures at the depths sampled during periods when thick glacial ice covered the yellowstone national park region pore fluid pressures in the underlying rock were increased in proportion to the weight of the overlying column of ice accordingly theoretical reference boiling point curves that reflect the maximum temperature attainable in a hot water geothermal system at a given depth were elevated and temperatures within zones of major hydrothermal upflow drill holes y 2 y 3 y 6 y 11 y 13 and upper part of y 5 increased the thicknesses of ice required to elevate boiling point curves sufficiently to account for the observed fluid inclusion t sub h values are within the ranges estimatedmore by glacial geologic studies at the margins of major hydrothermal upflow zones drill holes y 4 and y 9 fluid inclusion t sub h values at given depths range from 57 c lower to about the same as the current temperature measurements because of a previous decrease in the rate of discharge of warm water and or an increase in the rate of recharge of cold water into the hydrothermal system less

a high resolution record of holocene climate change in speleothem calcite from cold water cave northeast iowa high precision uranium thorium mass spectrometric chronology and 18o 13c isotopic analysis of speleothem calcite from cold water cave in northeast iowa have been used to chart mid holocene climate change significant shifts in 18o and 13c isotopic values coincide with well documented holocene vegetation changes temperature estimates based on 18o 16o ratios suggest that the climate warmed rapidly by about 3 c at 5900 years before present and then cooled by 4 c at 3600 years before present initiation of a gradual increase in 13c at 5900 years before present suggests that turnover of the forest soil biomass was slow and that equilibrium with prairie vegetation was not attained by 3600 years before present

the flickering switch of late pleistocene climate change polar ice contains a unique record of past climate variations previous greenland ice cores have documented relatively warm interstadial periods during the last glaciation and short centuryscale returns to colder conditions during the glacial to interglacial warming see for example ref 1 these climate features have also been observed to varying degrees in ocean sediment cores2 4 and terrestrial pollen and insect records5 7 here we report electrical conductivity measurements from a new greenland ice core which confirm these previous observations and also reveal a hitherto unrecognized mode of rapid climate variation fluctuations in ice conductivity on the scales of 5 20 years reflect rapid oscillations in the dust content of the atmosphere this flickering between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation

uranium series age determination of calcite veins vc 1 drill core valles caldera new mexico uranium series analysis sup 238 u sup 234 u sup 230 th of 13 calcite veins from the hydrothermally altered madera limestone in the vc 1 drill core was performed to determine the ages of the veins and their relation to the valles hydrothermal system thermal water from vc 1 and two hot springs in san diego canyon was analyzed for u and sup 234 u sup 238 u to help evaluate the constancy of initial sup 234 u sup 238 u the sup 230 th sup 234 u age of one of the veins is similar to 95 kyr and those of two other veins are similar to 230 and similar to 250 kyr five of the veins have near equilibrium sup 230 th sup 234 u and are probably older than similar to 0 3 m y uranium concentrations in the remaining veins are too low for analysis by the cap alpha spectrometry techniques employed in this study of the five veins near sup 230 th sup 234 u equilibrium suggesting ages greater than similar to 1 0 m y but one has sup 234 u sup 238 u 1 15 suggesting an age between similar to 0 3 and similar to 1 0 m y calculated initial sup 234 u sup 238 u of the veins yielding relatively young ages are neither equal to each other nor to sup 234 u sup 238 u in thermal water from vc 1 indicating inconstancy of initial supmore 234 u sup 238 u tht may be related to variations in groundwater mixing proportions three of the four veins that yield relatively young ages consist of coarse sparry vuggy calcite suggesting that this may be the type of calcite vein which forms under conditions resembling those encountered presently in vc 1 the analytical data are consistent with closed system behavior of u and th in the vc 1 calcite veins copyright american geophysical union 1988 less

glacier fluctuations in the eastern andes of colombia south america during the last 45 000 radiocarbon years abstract major glacial advances in the eastern cordillera of colombia preceded the global ice volume maximum at ca 20 ka bp two glacial events are recognized for isotope stage 3 dated between probably 43 and 38 ka bp and between 36 and 31 ka bp the events are recorded in glacial deposits and strongly subdued morainic ramparts three glacial advances during isotope stage 2 are dated between 23 5 and 19 5 ka bp 18 0 and 15 5 ka bp and 13 5 and 12 5 ka bp the glacial landforms associated with the period 18 0 to 15 5 ka bp are most distinct the arcuate multiple morainic ridge system of up to tens of meters of height can be traced throughout the region the moraines that formed during the earlier isotope stage 2 advance are more subdued the youngest isotope stage 2 morainic complex consists of low winding ridges isotope stage 1 glaciations affected only the highest areas of the eastern cordillera where morainic complexes associated with at least three glacial events occur but remain poorly dated the glacial record of the colombian eastern cordillera registers high climatic variability in the tropical andes during the late quaternary period

fluoride contamination of groundwater in parts of eastern india and a preliminary experimental study of fluoride adsorption by natural haematite iron ore and synthetic magnetite incidence of high fluoride f in groundwater 1 5 mg l in two tribal belts of eastern india one around chukru in the palamau district of jharkhand and the other around karlakot in the nuapada district of odisha has been studied the maximum concentration of f in groundwater from dug wells and tube wells is 10 30 mg l in chukru and 4 62 mg l in karlakot the groundwaters are mildly alkaline with ph ranges of 7 52 8 22 and 7 33 8 20 in chukru and karlakot respectively the f concentration is positively correlated with ph electrical conductivity and so4 2 in both areas the high f in groundwater resulted mainly from dissolution of biotite and fluorapatite in quartzofeldspathic gneiss the ionic dominance pattern in meq l is mostly in the order ca2 na mg2 k among cations and hco3 so4 2 f among anions in the karlakot groundwater preliminary adsorption experiments were conducted on natural haematite iron ore and synthetic magnetite to evaluate their potential for f removal from water effects of different parameters such as contact time ph adsorbent dose and initial f concentration on the adsorption capacity of these materials were investigated strong dependence of f removal on ph was observed for both the adsorbents with natural haematite iron ore the maximum f removal of 66 occurred at an initial ph of 3 2 for a solution with f concentration of 3 mg l adsorbent dose of 7 g l and overnight contact time the haematite iron ore was observed to increase the ph of the f solution adsorption equilibrium was not achieved with this adsorbent even after a contact time of 45 2 h in the case of synthetic magnetite 84 f removal was achieved after 2 min of contact time for a solution with f concentration of 6 mg l adsorbent dose of 10 g l and initial ph of 7 the results indicate high potential of both natural haematite iron ore and synthetic magnetite as adsorbents of f in water

historical climatic record from flood sediments deposited in the interior of spiralka cave czech republic abstract magnetic susceptibility was measured on more than four hundred samples collected from a 5 m high section of fine grained sediments deposited during flood events in the interior of spiralka cave spiralka cave is located in the northeastern portion of the moravian karst czech republic in the upper 1 5 m of this profile mineral magnetic fe arm sirm s ratio t and other non magnetic measurements heavy mineral concentration loss on ignition and particle grain size indicate that variations are controlled by the concentration of magnetite and by magnetic grain size i e increased magnetic susceptibility results from increased concentration of coarse grained magnetite a positive correlation with ti and zr concentrations in this part of the profile with our magnetic susceptibility record is a detrital signal responding to changing environmental conditions in the catchment area furthermore a comparison of our susceptibility record to the record of winter temperature anomalies constructed from both instrumental and historical records collected at the klementinum observatory in prague shows a remarkable correlation the most probable explanation of these correlations is that during years with warmer winters positive winter temperature anomalies and less snow cover the floods were less intensive but probably had access to larger tracts of cultivated land as agriculture tended to expand during these warmer periods cultivation of the land provided flood waters with greater access to coarser grained magnetite like materials exposed by tilling of soils lower in the profile interpreting the environmental significance of magnetic susceptibility variations is more complex as remobilization of iron has occurred nevertheless the magnetic susceptibility record when coupled with non magnetic measurements can be shown to correlate to known environmental conditions present in central europe during the deposition of the lower portion of the profile

geochemical assessment of groundwater contamination with special emphasizes on fluoride a case study from midyan basin northwestern saudi arabia water samples for chemical analyses were collected in january 2012 a total of 72 samples of groundwater were collected from 72 boreholes in the midyan basin northwestern saudi arabia samples were collected in polyethylene bottles and preserved and the used analytical techniques were in accordance with the standard methods from american public health association geochemical analyses of the groundwater samples from midyan basin reveal the concentration of fluoride f between 0 98 and 2 1 mg l other parameters e g ph ec tds hco3 so4 no3 cl k na mg and ca have been found in a variable proportion among them the concentration of ec hco3 k na and mg is higher than the permissible limits according to thermodynamical considerations most of the analysed samples are graded under saturated with respect to calcite and fluoride while saturation has been observed in some samples the under saturation could probably be attributed to low concentration of calcite and fluoride in the studied wells fluoride concentration shows weak positive correlation with ec tds na cl and so4 factors controlling the concentration of fluoride f in the studied samples are the area climate water chemistry and the presence of accessory minerals in the rocks through which groundwater is circulating besides the anthropogenic activities in the area

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

calcite veining and feeding conduits in a hydrothermal system insights from a natural section across the pleistocene golemezli travertine depositional system western anatolia turkey abstract linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key factor in geothermal research a contribution to this achievement derives from the study of spring related travertine deposits but although travertine depositional systems occur widely their feeding conduits are only rarely exposed the integrated study carried out in the geothermal golemezli area nearby the well known pamukkale area denizli basin western anatolia turkey focused on onyx like calcite veins banded travertine and bedded travertine well exposed in a natural cross section allowing the reconstruction of the shallower part of a geothermal system the onyx like veins represent the thickest vein network 150 m so far known new field mapping and structural kinematic analyses allowed to document a partially dismantled travertine complex bedded travertine formed by proximal fissure ridges and distal terraced pools depositional systems the banded calcite veins wnw trending and up to 12 m thick developed within a 200 m thick damaged rock volume produced by parallel fault zones th u dating indicates a long lasting middle late pleistocene fluids circulation in a palaeo geothermal system that due to its location and chemical characteristics can be considered the analogue of the nearby still active pamukkale system the isotopic characteristics of the calcite veins together with data from fluid inclusions analyses allow the reconstruction of some properties i e temperature salinity and isotopic composition and processes i e temperature variation and intensity of degassing that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals elongated microsparite micrite bands controlled by changes fluctuations of the physico chemical fluid characteristics

milankovitch theory viewed from devils hole variations in the oxygen isotope content 18o of late quaternary deep sea sediments mainly reflect changes in continental ice mass1 and hence provide important information about the timing of past ice ages because these sediments cannot yet be dated directly beyond the range of radiocarbon dating 40 50 kyr ages for the 18o record have been generated2 3 by matching the phase of the changes in 18o to that of variations in the earth s precession and obliquity adopting this timescale yields a close correspondence between the time varying amplitudes of these orbital variations and those of a wide range of climate proxies4 lending support to the milankovitch theory that the earth s glacial interglacial cycles are driven by orbital variations recently winograd et al 5 reported a record of 18o variations in a fresh water carbonate sequence from devils hole nevada dated by u th disequilibrium6 they concluded that the timing of several of the features in the record which reflects changes in the temperature of precipitation over nevada as well as changes in the isotopic composition of the moisture source5 7 showed significant deviations from that predicted by milanko vitch theory here we demonstrate that applying the devils hole chronology to ocean cores requires physically implausible changes in sedimentation rate moreover spectral analysis of the devils hole record shows clear evidence of orbital influence we therefore conclude that transfer of the devils hole chronology to the marine record is inappropriate and that the evidence in favour of milankovitch theory remains strong

environmental hydrogeochemistry and genesis of fluoride in groundwaters of dindigul district tamilnadu india fluoride f is an indispensable element for the human s skeletal and dental health at prescribed levels and becomes lethal at higher levels spatial temporal variability of f and its geochemical control association with other dissolved ions in groundwater in the dindigul district of tamilnadu india were conducted to describe the geochemical dynamics of f in response to seasonal variability high concentrations of fluoride 1 5 mg l 1 were observed in the northern region of the district high levels of f were observed in non monsoon periods and low levels in monsoon because of dilution by precipitation bicarbonate was well correlated with f which explains that both ions were derived from the weathering while f has a very weak correlation with silica this implies that the silicate weathering does not supply f to the groundwater system the f pollution in dindigul groundwaters is mainly driven by two factors 1 the geogenic weathering inputs the geology of this area mainly comprises fluoride bearing minerals e g hornblende biotite gneiss and charnockite 2 the anthropogenic inputs agri fertilizers and tannery waste further f in the study area is mainly attributed to geogenic sources during pre and postmonsoons and anthropogenic sources in monsoon periods

kinematic elements of antarctic intermediate water in the western south atlantic the northward flowing antarctic intermediate water aaiw is a major contributor to the large scale meridional circulation of water masses in the atlantic together with bottom and thermocline water aaiw replaces north atlantic deep water that penetrates into the south atlantic from the north on the northbound propagation of aaiw from its formation area in the south western region of the argentine basin the aaiw progresses through a complex spreading pattern at the base of the main thermocline this paper presents trajectories of 75 subsurface floats seeded at aaiw depth the floats were acoustically tracked covering a period from december 1992 to october 1996 discussions of selected trajectories focus on mesoscale kinematic elements that contribute to the spreading of aaiw in the equatorial region intermittent westward and eastward currents were observed suggesting a seasonal cycle of the aaiw flow direction at tropical latitudes just offshore the intermediate western boundary current the southward advection of an anticyclonic eddy was observed between 5 degrees s and 11 degrees s farther offshore the flow lacks an advective pattern and is governed by eddy diffusion the westward subtropical gyre return current at about 28 degrees s shows considerable stability with the mean kinetic energy to eddy kinetic energy ratio being around one farther south the eastward deeper south atlantic current is dominated by large scale meanders with particle velocities in excess of 60 cm s 1 at the brazil falkland current confluence zone a cyclonic eddy near 40 degrees s 50 degrees w seems to act as injector of freshly mixed aaiw into the subtropical gyre in general much of the mixing of the various blends of aaiw is due to the activity of mesoscale eddies which frequently reoccupy similar positions c 1999 elsevier science ltd all rights reserved

high fluoride in groundwater of an industrialized area of eastern india odisha inferences from geochemical and isotopic investigation an assessment of fluoride distribution in groundwater of an industrialized area talchir odisha india was carried out to understand the potential sources and processes this study is significant as the water resources are being endangered by the mining and other industrial activities in this region high concentration of fluoride 4 4 mg l was observed in groundwater of this area which was attributed mainly to mining activities additional source for high fluoride is the basement granitic rock containing fluoride bearing minerals like amphibole biotite and fluorite the dominant chemical types are found to be na ca hco3 na mg hco3 ca mg hco3 and ca na hco3 the groundwater facies variation was found in accordance with the local lithology there was no marked difference in the fluoride concentration of groundwaters between near and far off mining zone geochemical modeling indicated precipitation of calcite and dolomite as the driving force for the release of fluoride from the formation in addition to the precipitation of calcite and dolomite evapotranspiration also contributes to high fluoride in groundwater environmental stable isotopes inferred that there was no clear isotopic distinction between high and low fluoride groundwater and the groundwater was found to be evaporated environmental tritium data suggested that the groundwater was modern and fluoride enrichment was facilitated by long residence time of groundwater statistical methods also corroborate the geochemical and isotopic inferences the study highlights that natural geogenic source is the main cause for high fluoride in groundwater refuting earlier theories that attribute mining activities as the only source for high fluoride in this region

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

major ion signatures for identification of geochemical reactions responsible for release of fluoride from geogenic sources to groundwater and associated risk in vaniyar river basin dharmapuri district tamil nadu india fluoride is a common constituent in most of the rocks and the release of fluoride into groundwater is the major problem in several parts of the world the present study was carried out with the objective of identifying sources and mechanism of release of fluoride from the rocks and its impact on human health in vaniyar river basin dharmapuri district tamil nadu groundwater samples were collected from 44 wells once in 2 months from june 2011 to august 2014 and analyzed for major cations and anions using an ion chromatograph the possible reasons for the increased concentration of fluoride in groundwater of the area were investigated by taking into account of the agricultural practises and the major rock types in the area the observed order of the dominance of cations in groundwater in the study area is na ca2 mg2 k and that of anions is cl hco3 so42 co3 f the fluoride concentration in groundwater of this region ranges from 0 15 to 6 14 mg l out of 569 samples analysed fluoride concentration exceeded the maximum permissible limit of the drinking water standards of bis 1 5 mg l in 396 samples many people living in this area are suffering from dental and skeletal fluorosis due to prolonged use of fluoride rich groundwater for drinking concentration of fluoride in groundwater is relatively low in wells located in charnockite region whereas the concentration of fluoride in groundwater is high in the deep wells in regions comprising of epidote hornblende biotite gneiss the major source of fluoride in groundwater in the area is due to leaching of fluoride bearing minerals fluoride ions from biotite and hornblende minerals leach into the groundwater and contribute high fluoride concentration in this region the concentration of fluoride in groundwater increases when the water level is deep indicating higher release of fluoride from greater depth the geochemical reactions that control the release of fluoride from fluoride bearing minerals such as biotite and hornblende into groundwater were identified removal of high concentration of fluoride from drinking water is necessary in this region and measures should be taken to supply water after removal of fluoride for the betterment of the livelihood in the area

factors controlling fluoride contents of groundwater in north central and northwestern sri lanka chemical characterization has been made of groundwater bodies at 294 locations in four village districts in north central and northwestern sri lanka with special focus on fluorine contamination high fluoride contents in groundwater are becoming a major problem in the dry zone of sri lanka and dental fluorosis and renal failures are widespread field measurements of temperature ph and electrical conductivity were made during sampling chemical analyses of the water samples were later made using atomic absorption spectroscopy spectrophotometry and titration fluoride concentrations in the study area vary from 0 01 to 4 34 mg l and depend on ph and the concentrations of na ca and hco3 basement rocks including hornblende biotite gneiss biotite gneiss and granitic gneiss seem to have contributed to the anomalous concentrations of fluoride in the groundwater longer residence time in aquifers within fractured crystalline bedrocks may enhance fluoride levels in the groundwater in these areas in addition elevated fluoride concentrations in shallow groundwater in intensive agricultural areas appear to be related to the leaching of fluoride from soils due to successive irrigation

isotopic evidence for holocene climate change in the northern rockies from a goethite rich ferricrete chronosequence abstract climate proxy records often show regional heterogeneity due to the complex interplay of large scale atmospheric circulation patterns and local topographic features this is especially prevalent in the mountainous regions of the western united states where the interaction of two seasonally distinct weather systems can result in locally abrupt climate boundaries here we establish oxygen isotope ratios of goethite from ferricrete chronosequences formed by natural acid rock drainage as a new source of spatially small scale holocene climate information systematic study of these deposits may prove useful in understanding regional variations in response to global holocene climate change oxygen isotope ratios of goethites from the mountainous northeastern yellowstone region show an increase of 3 over the past 9000 years we attribute this isotopic change to a local increase of isotopically heavier summer precipitation since the early holocene possibly augmented by seasonal temperature differences brought on by orbitally forced insolation changes over the past 9000 years our interpretation is compatible with palynology studies as well as holocene climate simulations which indicate a decrease in monsoon intensity from 9000 years b p to the present unlike the southwestern united states this change may have resulted in wetter summers in our study area

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

genesis and geochemistry of high fluoride bearing groundwater from a semi arid terrain of nw india occurrence of fluoride in natural water resources and the associated health hazards have been reported from many parts of india during the last decade with the objective of organizing a systematic scientific programme to understand the geochemical behaviour of fluoride in natural water resources in relation to the local hydrogeological climatic conditions and agricultural use a typical semi arid terrain in the northwestern part of india was chosen for detailed study the present work is an attempt to study the fluoride contamination in groundwater in parts of jaipur district rajasthan state and to assess the origin and genesis of fluoride in groundwater the area falling under the semi arid tract of central rajasthan is geologically occupied by alluvial formations and precambrian rocks gneisses and schists where groundwater occurs under unconfined to semi confined conditions a total of 66 groundwater samples was collected during the pre monsoon period and analysed which gave a concentration of fluoride in water in the range of 0 35 to 9 3 mg l with 62 of the samples in excess of permissible limit of 1 5 mg l as compared to alluvial formations fluoride enrichment in groundwater is higher in hard rock areas the samples collected from the granite gneissic terrain show higher values when compared to those in the schist the groundwater of the shallow aquifers soil clay complex weathered zone has a higher concentration of fluoride than the deep fractured hard rock aquifer does the possible sources of fluoride are chemical weathering and leaching of fluorine bearing minerals present in hard rocks and alluvial formations under the alkaline environment in arid to semi arid conditions high ph as well as alkalinity and low levels of ca mg and total hardness suggest favourable chemical conditions for the fluoride dissolution process a higher rate of evapotranspiration intensive and long term irrigation and heavy use of fertilizers are the supplementary factors that further increase the fluoride content in the groundwater a groundwater management programme is suggested

geomagnetic field control of 14c production over the last 80 ky implications for the radiocarbon time scale we have used a recent estimate of the geomagnetic dipole field strength over the last 80 ky to examine the extent to which changes in geomagnetic field intensity have affected the radiocarbon time scale the magnetic record was converted into a 14c production signal which was then used to produce a synthetic atmospheric 14c record using a two box model for the carbon cycle this calibration suggests that the geomagnetic field has been the main factor governing the production of cosmogenic 14c atoms over the period of time considered and that 14c changes due to other causes such as climatic changes have been of lesser importance the results indicate that the radiocarbon ages are 2 to 3 ky younger than true age in the interval 18 40 ky b p in good agreement with recent u th and 14c age comparisons moreover the results predict that a negligible difference between true and 14c ages should be observed around 45 50 ky

evaluation of hydrogeochemical characteristics of phreatic alluvial aquifers in southeastern coastal belt of prakasam district south india the assessment of hydrogeochemical processes that govern the water quality of inland freshwater aquifers in coastal environment especially in indian sub continent is occasionally attempted to bridge the gap a detail hydrochemical evaluation of groundwater occurring in coastal alluvium is attempted single set of high density water sampling is done from a limited area to gain an in depth knowledge of the processes that govern the water chemistry of the sandy aquifers the water is of weak alkaline nature and less mineralized ec being na ca2 hco3 so42 mg2 no3 na and cl are almost in similar proportions implying the influence of coastal climate on water quality the water shows modest variation in their ionic assemblage among different sample points as evident from schoeller scheme groundwater can be classified into three distinct facies viz cl ca2 mg2 na cl and ca2 mg2 hco3 types the ionic assemblages their indices ratios and cross plots substantiate that multiple processes were involved in the evolution of the water chemistry among them silicate weathering halite dissolution ion exchange and base exchange played prominent role in the ion enrichment of groundwater the aquatic chemistry is further influenced and modified by marine environment evapotranspiration and anthropogenic inputs which is authenticated by good correlation r2 1 among the na cl ec mg2 na and cl gibbs plots established that evaporation is more responsible for contribution of minerals to the groundwater than aquifer material nitrate contamination can be attributed for poor sewerage disposal mechanism which is aggravated by fertilizer inputs irrigation practices and agriculture activity a contrasting correlation r2 90 to 0 40 among select pairs of ions reassures dissimilar source of those ions involvement of multiple processes and limited interaction of formation water with aquifer material

fire and alluvial chronology in yellowstone national park climatic and intrinsic controls on holocene geomorphic processes we employed a systemwide approach a large and robust set of radiocarbon ages and modern process analogs to interpret the holocene history of forest fire related sedimentation and overall alluvial activity in northeastern yellowstone national park debris flow and flood events following the 1988 fires provided facies models for interpreting the stratigraphic record of fire related sedimentation within valley side alluvial fans of soda butte creek fire related deposits make up approximately 30 of the late holocene fan alluvium fifty 14 c ages on fire related events cluster within the intervals of 3300 2900 2600 2400 2200 1800 and 1400 800 yr b p and suggest earlier episodes of large fires and fan aggradation around 7500 5500 and 4600 4000 yr b p a major pulse of fire related debris flow activity between 950 and 800 yr b p coincided with the height of the widely recognized medieval warm period ca a d 1050 1200 instrumental climate records over the last 100 yr in yellowstone imply that the intensity and interannual variability of summer precipitation are greater during warmer periods enhancing the potential for severe short term drought major forest fires and storm generated fan deposition along lower soda butte creek fill cut terrace treads were created by lateral migration of channels and accumulation of overbank sediments ca 8000 yr b p terrace level t1a 7000 5600 t1b 3100 2600 t2 2000 1300 t3 and post 800 yr b p t4 these periods coincide with overbank sedimentation on slough creek and the lamar river but alternate with intervals of fire related fan deposition implying a strong climatic control local paleoclimatic data suggest cooler effectively wetter conditions during terrace tread formation in warmer drier intervals reduced average runoff in axial streams results in meander belt narrowing concurrent channel incision may be caused by infrequent large floods greater resistance to downcutting however allowed fewer terraces to be formed along slough creek and the lamar river alluvial systems in northeastern yellowstone show a clear response to millennial scale climatic cycles wherein alluvial fans aggrade and prograde over flood plains in drier periods axial streams widen their flood plains and trim back the fans during wetter periods small scale climatic fluctuations of the holocene thus had substantial impact on postglacial landscapes in northeastern yellowstone

fluoride occurrence and mobilization in geo environment of semi arid granite watershed in southern peninsular india plausible forms of fluoride f responsible for the persistence of fluoride toxicity in ground water of a granitic terrain of semi arid region which is the main source of drinking water have been studied the study area in anantapur district of andhra pradesh india is one of the chronic regions with excess fluoride in groundwater and the region is under transformation into aridity due to poor rainfall and over exploitation of groundwater geochemical analysis of soil groundwater and rock samples of the study area revealed the presence of other toxic elements also in addition to fluoride which need to be addressed in drinking water sector in near future soil fluoride leaching experiments demonstrated the probable mode of mobilization of f into the groundwater through natural recharge process during monsoon analysis of saturation indices indicates that the fluorite solubility alone is not attributable to the high fluoride content in groundwater the groundwater flow controls fluoride mobilization in the study area as it is evidenced through fluoride concentration and electrical conductivity increase from catchment to downstream region creation of lesser fluoride groundwater sources through rainwater harvesting and artificial recharge of groundwater in catchment areas is suggested as a long term sustainable safe drinking water strategy