lead isotopic evidence for an australian source of aeolian dust to antarctica at times over the last 170 000 years abstract systematic analysis of pb sr and nd isotopes of 32 fluvial clay samples 6 km 2 murray darling basin mdb located in semiarid southeastern australia displays similar isotopic values between some mdb clays and dust from several ice core samples from the epica dome c in antarctica close scrutiny of several ratios of the four pb isotopes and in particular 208 pb 207 pb versus 206 pb 207 pb shows that several samples from the darling sub basin of the mdb display similar values for the same isotopes for dome c samples from different ages and more particularly during wet phases in australia marine isotopic stages 5e 3 and 1 the combination of nd and sr isotopic ratios from the same mdb fluvial clays clearly eliminates the murray sub basin and supports the darling sub basin as a potential source of aeolian material to antarctica overall the australian dust supply to antarctica predominantly occurred during interglacial periods the work presented here shows that aerosols generated in southeastern australia can travel to parts of west antarctica and this is supported by atmospheric observations and models in addition evidence of australian dust in antarctic ice cores further implies dust deposition in the southern ocean would have occurred in the past current meteorological observations also imply that the western pacific and indian ocean sector of the southern ocean would frequently receive aeolian dust components originating from southeastern australia

seasonal variability in the origin of recent atmospheric mineral dust at northgrip greenland abstract isotopic sr and nd and mineralogical analyses of dust extracted from snow deposits from the last decade at the northgrip greenland ice camp 75 1 n 042 3 w confirm the eastern asian source for greenland dust and extend it to the present day the 1998 and 1999 samples which represent a 2 4 month resolution of dust deposition show that there are at least two east asian sources for the greenland dust that vary seasonally the provenance of dust during the major spring summer deposition is the takla makan desert of northwest china

site information and initial results from deep ice drilling on law dome antarctica the aim of deep ice drilling on law dome antarctica has been to exploit the special characteristics of law dome summit i e low temperature and high accumulation near an ice divide to obtain a high resolution ice core for climatic environmental studies of the holocene and the last glacial maximum lgm drilling was completed in february 1993 when basal ice containing small fragments of rock was reached at a depth of 1196 m accurate ice dating obtained by counting annual layers revealed by fine detail 18 o peroxide and electrical conductivity measurements is continuous down to 399 m corresponding to a date of ad 1304 sulphate concentration measurements made around depths where conductivity tracing indicates volcanic fallout allow confirmation of the dating for agung in 1963 and tambora in 1815 or estimates of the eruption date from the ice dating for the kuwae vanuatu eruption 1457 the lower part of the core is dated by extrapolating the layer counting using a simple model of the ice flow at the lgm ice fabric measurements show a large decrease 250 to 14 mm 2 in crystal size and a narrow maximum in c axis verticality the main zone of strong single pole fabrics however is located higher up in a broad zone around 900 m oxygen isotope 18 o measurements show holocene ice down to 1113 m the lgm at 1133 m and warm 18 o about the same as holocene ice near the base of the ice sheet the lgm holocene 18 o shift of 7 0 only 1 larger than for vostok indicates that law dome remained an independent ice cap and was not overridden by the inland ice sheet in the glacial

conductivity depth imaging of helicopter borne tem data based on a pseudolayer half space model helicopter borne time domain electromagnetic htem systems with a concentric horizontal coil configuration have been used increasingly in mineral exploration conductivity depth imaging cdi is a useful tool for mapping the distribution of geologic conductivity and for identifying conductive targets a cdi algorithm for htem systems with a concentric coil configuration is developed based on the pseudolayer half space model primary advantages of this model are immunity to altimeter errors and better resolution of conductive layers than other half space models effective depth is derived empirically from the diffusion depth and apparent thickness of the pseudolayer a table lookup procedure is established based on the analytic solution of a half space model to speed up processing this efficiency makes generation of real time conductivity depth images possible tests on synthetic data demonstrate that the pseudolayer conductivity depth imaging algorithm maps a wider range of conduc tivities and does a better job of resolving highly conductive layers compared with that of the homogeneous half space model effective depths are close to true depths in many circumstances field examples show stable and geologically meaningful conductivity depth images

seasonal variations in the origin of lead in snow at dye 3 greenland abstract the isotopic composition and concentration of lead has been measured in fresh and slightly aged snow collected at dye 3 in southern greenland during one full year the lead concentration displayed large variations ranging from 14 3016 pg g in april spring to 3 6 pg g in september summer while the isotopic ratios changed in regular manner during the year the 206 pb 207 pb ratios were 1 15 from spring to mid summer snow and increased in late summer to early autumn reaching 1 20 in winter these isotopic data indicate that the lead in the autumn to winter snow originated in north america while that in spring to mid summer snow is from eurasia

calibrating the ice core paleothermometer using seasonality high resolution oxygen isotope measurements on the dome summit south dss ice core from law dome antarctica provide a seasonal profile that is sufficiently stable and undistorted by biases in accumulation to permit comparison with measured temperature seasonality this comparison yields an isotope temperature relation with a gradient d dt of 0 44 0 02 c and provides a new method for exploring the isotope temperature relationship at high accumulation sites if applied to the observed isotope record from the dss core which extends through the last glacial and beyond this calibration suggests that at its coldest the last glaciation was 13 c colder than present at this site after correcting for elevation change this finding compares with a temperature difference of 8 c computed by using the local spatially derived calibration

how synchronous are neogene marine plankton events an electronic supplement of this material may be obtained on adiskette or anonymous ftp from kosmos agu org login toagu s ftp account using anonymous as the username andguest as the password go to the right directory by typing cdapend type ls to see what files are available type get and thename of the file to get it finally type exit to leave the system paper 94pa01456 how synchronous are neogene marine planktonevents by c spencer cervato h r thierstein d b lazarus andj p beckmann diskette may be ordered from american geophysicalunion 2000 florida avenue n w washington dc 20009 15 00 payment must accompany order we analyzed the synchrony and diachrony of commonly used neogene biostratigraphic events from data published in the initial reports of the deep sea drilling project dsdp and in the proceedings of the ocean drilling program odp on the basis of the combined biostratigraphic and magnetostratigraphic evidence new neogene age models were constructed for 35 globally distributed dsdp and odp holes biostratigraphic events from the four major plankton groups calcareous nannofossils diatoms planktonic foraminifera and radiolarians were compiled from dsdp and odp reports after the elimination of possible sources of error such as stratigraphic hiatuses and reworking of specimens 124 biostratigraphic events that occurred in at least four holes were analyzed in detail for each event a biochronologic age estimate was derived by projection of the depth of the event onto the line of correlation of each hole and from these a global mean age for each event was calculated together with its standard deviation average standard deviations for event ages by fossil group are calcareous nannofossil first appearance datums fads 0 57 m y 21 events calcareous nannofossil last appearance datums lads 0 60 m y 25 events diatom fads 0 57 m y 7 events diatom lads 0 85 m y 14 events planktonic foraminifera fads 0 88 m y 22 events foraminifera lads 0 68 m y 16 events radiolarian fads 0 30 m y 9 events radiolarian lads 0 31 m y 10 events since the average sample spacing in the sites used for this analysis is only 0 185 m y we have examined the data for true patterns of diachrony and for other biases diachrony is more frequent among cosmopolitan than among endemic taxa thus there is a general trade off between the obtainable age precision and the geographic extent of a bioevent precision of age calibrations also decreases with increasing age although some of these features may be due to investigator bias they appear in part to be real phenomena and thus could also provide opportunities for further exploration of important paleobiological processes such as change in environmental gradients through time evolutionary adaptation of species populations and migration due to water mass changes

climate changes lead pollution and soil erosion in south greenland over the past 700 years date of acceptance 05 06 2015 this research was made possible through funding provided by the leverhulme trust the spanish ministry of science and innovation project cgl2010 20672 and xunta de galicia grants r2014 001 and gpc2014 009 n silva sanchez is currently supported by a fpu pre doctoral grant ap2010 3264 funded by the spanish government kirsty golding andy mcmullen and ian simpson are thanked for their assistance with fieldwork alison sandison produced the maps pete langdon and two anonymous referees are thanked for comments that helped to improve the paper

features of meteorological events preserved in a high resolution law dome east antarctica snow pit snow pitandshallow firn corerecordsofoxygenisotoperatios d 18 o and traceionspeciesweregeneratedatahigh accumulationsiteonlaw dome eastantarctica concordancebetweenaccumulationeventsidentifiedin recordsupto 7 7kmapartconfirms that the observed glaciochemical variations are the result of regional rather than local sur face effects this allows calibration of the snow pit records with measured meteorological parameters netaccumulationperiodsthatcomprisethesnow pitrecordareidentifiedusing hourly snow accumulation measurements from a co located automatic weather station aws particular focus isgiventothreenetaccumulationperiods preservedduringaustral summer 1999 2000 that correspond to the top 0 5m of the snow pit local meteorological conditions recorded during the summer accumulation periods by the aws are combined with regional and synoptic scale meteorology derived from casey station 110km away and advancedvery high resolution radiometer satellite imagery to identify potential source regions forchemical signals preserved in summer snowat law dome

simmax a modern analog technique to deduce atlantic sea surface temperatures from planktonic foraminifera in deep sea sediments we present a data set of 738 planktonic foraminiferal species counts from sediment surface samples of the eastern north atlantic and the south atlantic between 87 n and 40 s 35 e and 60 w including published climate long range investigation mapping and prediction climap data these species counts are linked to levitus s 1982 modern water temperature data for the four caloric seasons four depth ranges 0 30 50 and 75 m and the combined means of those depth ranges the relation between planktonic foraminiferal assemblages and sea surface temperature sst data is estimated using the newly developed simmax technique which is an acronym for a modern analog technique mat with a similarity index based on 1 the scalar product of the normalized faunal percentages and 2 a weighting procedure of the modern analog s ssts according to the inverse geographical distances of the most similar samples compared to the classical climap transfer technique and conventional mat techniques simmax provides a more confident reconstruction of paleo ssts correlation coefficient is 0 994 for the caloric winter and 0 993 for caloric summer the standard deviation of the residuals is 0 90 c for caloric winter and 0 96 c for caloric summer at 0 m water depth the sst estimates reach optimum stability standard deviation of the residuals is 0 88 c at the average 0 to 75 m water depth our extensive database provides sst estimates over a range of 1 4 to 27 2 c for caloric winter and 0 4 to 28 6 c for caloric summer allowing sst estimates which are especially valuable for the high latitude atlantic during glacial times an electronic supplement of this material may be obtained on adiskette or anonymous ftp from kosmos agu org login toagu s ftp account using anonymous as the username and guestas the password go to the right directory by typing cd append typels to see what files are available type get and the name of the file toget it finally type exit to leave the system paper 95pa01743 simmax a modern analog technique to deduce atlantic sea surfacetemperatures from planktonic foraminifera in deep sea sediments uwepflaumann josette duprat claude pujol and laurent d labeyrie diskette may be ordered from american geophysical union 2000florida avenue n w washington dc 20009 payment mustaccompany order

iron and other transition metals in patagonian riverborne and windborne materials geochemical control and transport to the southern south atlantic ocean abstract the bulk of particulate transition metals transported by patagonian rivers shows an upper crustal composition riverine particulate 0 5 n hcl leachable trace metal concentrations are mainly controlled by fe oxides complexation of fe by dissolved organic carbon doc appears to be an important determinant of the phases transporting trace metals in patagonian rivers in contrast aeolian trace elements have a combined crustal and anthropogenic origin aeolian materials have fe mn and al contents similar to that found in regional topsoils however seasonal concentrations of some metals e g co pb cu and zn are much higher than expected from normal crustal weathering and are likely pollutant derived we estimate that patagonian sediments are supplied to the south atlantic shelf in approximately equivalent amounts from the atmosphere 30 10 6 t yr 1 and coastal erosion 40 10 6 t yr 1 with much less coming from the rivers 2 0 10 6 t yr 1 low trace metal riverine fluxes are linked to the low suspended particulate load of patagonian rivers inasmuch most of it is retained in pro glacial lakes as well as in downstream reservoirs based on our estimation of aeolian dust fluxes at the patagonian coastline the high nutrient low chlorophyll sub antarctic south atlantic could receive 1 0 to 4 0 mg m 2 yr 1 of leachable 0 5 n hcl fe past and present volcanic activity in the southern andes through the ejection of tephra must be highlighted as another important source of fe to the south atlantic ocean based on the 1991 hudson volcano eruption it appears that volcanic events can contribute several thousand fold the mass of leachable fe to the ocean as is introduced by annual patagonian dust fallout

joint inversion of surface and three component borehole magnetic data the inversion of magnetic data is inherently nonunique with respect to the distance between the source and observation locations this manifests itself as an ambiguity in the source depth when surface data are inverted and as an ambiguity in the distance between the source and boreholes if borehole data are inverted joint inversion of surface and borehole data can help to reduce this nonuniqueness to achieve this we develop an algorithm for inverting data sets that have arbitrary observation locations in boreholes and above the surface the algorithm depends upon weighting functions that counteract the geometric decay of magnetic kernels with distance from the observer we apply these weighting functions to the inversion of three component magnetic data collected in boreholes and then to the joint inversion of surface and borehole data both synthetic and field data sets are used to illustrate the new inversion algorithm when borehole data are inverted directly three component data are far more usefu

astronomic timescale for the pliocene atlantic δ18o and dust flux records of ocean drilling program site 659 high resolution benthic oxygen isotope and dust flux records from ocean drilling program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the atlantic from 2 85 ma back to 5 ma spectral analysis of the 18o record indicates that the 41 kyr period of earth s orbital obliquity dominates the pliocene record this is shown to be true regardless of fundamental changes in the earth s climate during the pliocene however the cycles of sahelian aridity fluctuations indicate a shift in spectral character near 3 ma from the early pliocene to 3 ma the periodicities were dominantly precessional 19 and 23 kyr and remained strong until 1 5 ma subsequent to 3 ma the variance at the obliquity period 41 kyr increased the timescale tuned to precession suggests that the pliocene was longer than previously estimated by more than 0 5 m y

multiple sources supply eolian mineral dust to the atlantic sector of coastal antarctica evidence from recent snow layers at the top of berkner island ice sheet the sr and nd isotopic composition of dust extracted from recent snow layers at the top of berkner island ice sheet located within the filchner ronne ice shelf at the southern end of the weddell sea enables us for the first time to document dust provenance in antarctica outside the east antarctic plateau eap where all previous studies based on isotopic fingerprinting were carried out berkner dust displays an overall crust like isotopic signature characterized by more radiogenic 87sr 86sr and much less radiogenic 143nd 144nd compared to dust deposited on the eap during glacial periods differences with eap interglacial dust are not as marked but still significant indicating that present day berkner dust provenance is distinct at least to some extent from that of the dust reaching the eap the fourteen snow pit sub seasonal samples that were obtained span a two year period 2002 2003 and their dust sr and nd isotopic composition reveals that multiple sources are at play over a yearly time period southern south america patagonia in particular likely accounts for part of the observed spring summer dust deposition maxima when isotopic composition is shifted towards younger isotopic signatures in the spring possible additional inputs from australian sources would also be supported by the data most of the year however the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in east antarctica which carry old crust like isotopic fingerprints whether the restricted east antarctic ice free areas produce sufficient eolian material has yet to be substantiated however the fact that large 5 mu m particles represent a significant fraction of the samples throughout the entire time series supports scenarios that involve contributions from proximal sources either in patagonia and or antarctica possibly including snow free areas in the antarctic peninsula and other areas as well this also indicates that additional dust transport which does not reach the eap must occur at low tropospheric levels to this coastal sector of antarctica

pb and sr isotopic compositions of snowpack from quebec canada inferences on the sources and deposition budgets of atmospheric heavy metals elemental concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained along two main transects from the province of quebec canada one north south between 47 n and 55 n 1994 and the other within the st lawrence valley 1997 median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from 300 to 42 000 and are indicative of an anthropogenic origin pb isotope ratios for snow samples retrieved in 1994 are highly variable 206pb 207pb 1 148 to 1 193 and are characterized by the most radiogenic sr isotope values 87sr 86sr 0 710 in contrast the pb and sr isotope results for 1997 snow samples collected along the st lawrence valley below latitude 47 n yield the most radiogenic pb isotope ratios 206pb 207pb 1 180 to 1 190 and 87sr 86sr ratios between 0 708 and 0 710 the former indicate that the atmospheric pollution in this region of quebec is dominated by a mixture of anthropogenic emissions from u s 206pb 207pb 1 20 and canadian 206pb 207pb 1 15 sources pb isotope ratios 206pb 207pb 1 160 to 1 180 for 1997 samples collected north of latitude 47 n indicate input of an additional anthropogenic component possibly that of eurasian pollution being transported over the high arctic during the winter season a comparison of the pb isotope results between lichens and snow samples from identical sample locations indicate that these either overlap along st lawrence valley or are significantly different north south transect the latter discrepancy may be attributed to either 1 different time scales for the integration of the atmospheric signal months for snow vs years for lichens 2 recording of the atmospheric signal at substantially different altitudes or 3 the presence of an important local point source of atmospheric pollution annual depositional budgets have been estimated for pb cd zn cu and mn and average values g km 2 yr 1 are 1500 130 196 000 1900 and 6400 respectively compared to previous depositional fluxes 1993 1994 estimated from adjacent regions in north america those reported here are slightly lower with the exception of mn and zn the nondecrease in depositional fluxes of mn may be attributed to combustion of mn bearing fossil fuels by automotive vehicles the exact cause for the elevated annual depositional values for zn however remains enigmatic

intensive pre incan metallurgy recorded by lake sediments from the bolivian andes the history of pre columbian metallurgy in south america is incomplete because looting of metal artifacts has been pervasive here we reconstruct a millennium of metallurgical activity in southern bolivia using the stratigraphy of metals associated with smelting pb sb bi ag sn from lake sediments deposited near the major silver deposit of cerro rico de potosi pronounced metal enrichment events coincide with the terminal stages of tiwanaku culture 1000 to 1200 a d and inca through early colonial times 1400 to 1650 a d the earliest of these events suggests that cerro rico ores were actively smelted at a large scale in the late intermediate period providing evidence for a major pre incan silver industry

mapping lateral changes in conductance of a thin sheet using time domain inductive electromagnetic data abstractwith the inductive electromagnetic geophysical method the laterally varying conductance of thin sheet models can be estimated either through a direct transform of the measured data or through inversion the direct transform called the simplified solution does not require grid or line data and is simple enough to be performed in the field because the conductance at a location is calculated directly from the ratio of two measured magnetic fields the vertical spatial and temporal derivative of the vertical magnetic field at that location however the simplified solution assumes that the secondary horizontal magnetic fields are zero and or that the sheet has a uniform conductance our nonapproximate solution called the full inversion does not make these assumptions but requires gridded data measurements of the secondary horizontal magnetic fields and more complicated inversion algorithms through forward modeling we found that the full inversion provides better results than the simplified

ranking of dissolution susceptibility of planktonic foraminifera at high latitudes of the south atlantic ocean surface sediment samples from the maurice ewing bank eastern falkland plateau south atlantic ocean have been analyzed to rank dissolution susceptibility of cool water planktonic foraminiferal species a dissolution index is formulated from quantitative analyses of sedimentological properties caco3 content frequency of planktonic foraminiferal fragments radiolarians mineral grains and ratio of a dissolution tolerant to a dissolution susceptible planktonic foraminiferal species this index is used to assess degrees of dissolution in the samples quantified differences in relative abundance of species between the two dissolution regimes less prominent and stronger dissolution formed the basis for differentiation the species were ranked in the following order from most resistant to least resistant sinistrally coiled variety ofneogloboquadrina pachyderma antarctic variety of this species globorotalia inflata g truncatulinoides globigerina bulloides andglobigerinita glutinata a tie dextraln pachyderma subantarctic variety globigerinita uvula andglobigerina quinqueloba fragmentation frequency of damaged tests increases with increasing dissolution in tolerant species but not in susceptible species this may be because susceptible species are completely dissolved under intense dissolution whereas tolerant species although damaged remain and increase in abundance

a two century record of lead isotopes in high altitude alpine snow and ice a 140 m snow ice core drilled at mont blanc france has been analysed for pb isotopes pb and ba concentrations the 206pb 207pb ratio which was measured by thermal ionisation mass spectrometry decreased steadily from 1 18 about two centuries ago to 1 17 in 1960 then fell rapidly to 1 15 by 1968 evidence of the italian turin isotopic lead experiment iile was found in samples dated 1977 where the ratio dipped to 1 117 by the early 1990s it had returned to mid 1960s values large seasonal variations were found in pb and ba concentrations summer samples were associated with smooth changes in the 206pb 207pb ratio while larger fluctuations were encountered in winter which is consistent with a low altitude inversion near mont blanc in the winter and free transfer of pollutants from lower to higher altitudes at other times a plot of 208pb 207pb versus 206pb 207pb ratios reveals three isotopic groupings associated with the periods pre 1923 1923 1968 and 1969 1991 in the first group the isotopic composition is consistent with local mining smelting and coal burning while in the second motor vehicle exhaust emissions dominate in the third group motor vehicle emissions also dominate but the pb is even less radiogenic during this period the iile occurred and there was a reduction in the use of leaded gasoline in europe a comparison of the mont blanc and summit central greenland records shows they contain similar 206pb 207pb ratios between 1960 and 1968 although small differences in isotopic composition can be detected by also considering the 208pb 207pb ratio however after 1969 the two records diverge markedly with the greenland ratios being dominated by the highly radiogenic mississippi valley type pb from the usa and with the mont blanc ratios moving to lower values particularly about the time of the iile

a climatology of southern hemisphere extratropical cyclones a climatology of extratropical cyclones determined by an objective automatic scheme applied to 15 years 1975 89 of once daily australian bureau of meteorology hemispheric analyses is presented contour maps of the positions of formation cyclogenesis dissipation cyclolysis together with other cyclone statistics are presented the distribution of cyclones through the hemisphere was found to be dominated by a permanent high latitude core coincident with the circumpolar trough during the winter and intermediate seasons two mid latitude branches are evident in the cyclone density originating in the tasman sea and south american sectors both spiraling poleward and merging with the circumpolar core in the southern oceans systems were observed to move in an castsouth east direction away from their location of formation exhibiting peak speeds of migration in the mid latitudes little seasonality was evident in the densitiy distribution of cyclones through the southern oceans but a considerable amount was found in their central pressure

pb and sr isotopic evidence for sources of atmospheric heavy metals and their deposition budgets in northeastern north america concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained during the 1998 winter season from northeastern north america median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from ca 50 to 36 000 and are indicative of an anthropogenic origin the pb isotope ratios correlate with geographic location because snowpack from eastern ontario and the northeastern usa are characterized by the most radiogenic 206pb 207pb ratios ca 1 18 1 19 and these decrease systematically in an easterly direction towards the atlantic coast ca 1 16 the pb isotope data for the 1998 samples of snowpack indicate that atmospheric pollution in this region of north america is dominated solely by a mixture of anthropogenic emissions from us 206pb 207pb ca 1 20 and canadian 206pb 207pb ca 1 15 sources this result contrasts with that obtained for 1997 snowpack from similar geographic regions because the pb isotope data for the latter suggest the involvement of an additional anthropogenic component possibly that of eurasian pollution transported over the high arctic this difference in the distribution pattern of atmospheric pollution over northeastern north america between the 1997 and 1998 winter seasons may be related to the el nino phenomenon sr isotope data for all the 1998 snowpack samples define a large range in 87sr 86sr values but most are between 0 709 to 0 710 similar to the value of present day seawater ca 0 7092 however the majority of snowpack samples from eastern ontario are characterized by lower 87sr 86sr ratios 0 709 and these correlate negatively with their enrichment factors of pb such trends suggest the presence of a relatively unradiogenic source of anthropogenic sr possibly related to emissions from coal fired power plants located in the western and midwestern regions of the usa annual depositional budgets estimated from 1998 snowpack indicate that those for pb cd and cu are highest in eastern ontario and significantly lower in the remaining regions the former reflect a meteorological corridor in northeastern north america which coincides with heavily industrialized and densely populated areas depositional budgets of zn are extremely high in all areas investigated and their exact source s remains enigmatic these may reflect either an increase in atmospheric industrial emissions since the 1980s a lower residence time in the atmosphere or particular chemical speciation that affects the deposition of zn from the lower troposphere depositional budgets for mn are also high and may be related to the combustion of mn bearing fossil fuels by automotive vehicles

trace metal suites in antarctic pre industrial ice are consistent with emissions from quiescent degassing of volcanoes worldwide abstract trace metals are more abundant in atmospheric load and deposition material than can be due to rock and soil dusts and ocean salt in pre industrial ice from coastal west antarctica dust and salt account for only a few percent of the lead cadmium and indium that is present in most samples less than half in any sample for these trace metals the deposition rate to the pre industrial ice is approximately matched by the output rate to the atmosphere by quiescent non explosive degassing of volcanoes worldwide according to a new estimate the basis of the match is the masses and proportions of the metals and the proportions of pb isotopes in ice and in volcano emissions the isotopic compositions of pb in ice are similar to those of a suite of ocean island volcanoes mostly in the southern hemisphere the natural baseline values for pre industrial atmospheric deposition fluxes of trace metal suites at taylor dome and the worldwide quiescent volcano emissions fluxes to which they are linked constitute a reasonably well constrained baseline component for deposition fluxes of metals in modern times

inductive electromagnetic data interpretation using a 3d distribution of 3d magnetic or electric dipoles abstractin inductive electromagnetics the magnetic field measured in the air at any instant can be considered to be a potential field as such we can invert measured magnetic fields at a fixed time or frequency for the causative subsurface current system these currents can be approximated with a 3d subsurface grid of 3d magnetic closed loop current or electric line current dipoles whose location and orientation can be solved for using a potential field style smooth model inversion because the problem is linear both inversions can be solved quickly even for large subsurface volumes and both can be run on a single data set for complementary information synthetic studies suggest that for discrete induction dominated targets the magnetic and electric dipole inversions can be used to determine the center and top edge of the target respectively furthermore the orientation of plate targets can be estimated from visual examination of the orientations of the 3d vector dipoles and or using the inte

new calibration of neogene radiolarian events in the north pacific abstract new age models for twelve deep sea drilling project sites in the north pacific have been produced based on in order of importance in our dataset a recompilation of previously published diatom calcareous nannofossil and foraminifer first and last occurrences and magnetostratigraphy the projected ages of radiolarian first and last occurrences derived from the line of correlation of the age depth plots have been computed from these sites and 28 radiolarian events have thereby been newly cross calibrated to north pacific diatom and other stratigraphy several of the north pacific radiolarian events are older than in previously published equatorial pacific calibrations and some may be diachronous within the north pacific these patterns may be due to complex latitudinal patterns of clinal variation in morphotypes within lineages or to migration events from the north pacific towards the equator

seasonality in late holocene climate from ice core records high resolution ice core 18o data from a site with well preserved seasonal cycles are used to extract seasonal temperature trends over the last 700 years with an effective resolution of a few mont

the lead pollution history of law dome antarctica from isotopic measurements on ice cores 1500 ad to 1989 ad abstract lead isotopic compositions and pb and ba concentrations have been measured in ice cores from law dome east antarctica covering the past 6500 years natural background concentrations of pb 0 4 pg g and ba 1 3 pg g are observed until 1884 ad after which increased pb concentrations and lowered 206pb 207pb ratios indicate the influence of anthropogenic pb the isotopic composition of natural pb varies within the range 206pb 207pb 1 20 1 25 and 208pb 207pb 2 46 2 50 with an average rock and soil dust pb contribution of 8 12 a major pollution event is observed at law dome between 1884 and 1908 ad elevating the pb concentration four fold and changing 206pb 207pb ratios in the ice to 1 12 based on pb isotopic systematics and pb emission statistics this is attributed to pb mined at broken hill and smelted at broken hill and port pirie australia anthropogenic pb inputs are at their greatest from 1900 to 1910 and from 1960 to 1980 during the 20th century ba concentrations are consistently higher than natural levels and are attributed to increased dust production suggesting the influence of climate change and or changes in land coverage with vegetation

seasonal variability in the input of lead barium and indium to law dome antarctica lead pb isotopic compositions and concentrations and barium ba and indium in concentrations have been determined at monthly resolution in five law dome coastal eastern antarctica ice core sections dated from 1757 ad to 1898 ad natural background pb concentrations in 1757 ad average 0 2 pg g 1 and can be attributed to mineral dust and volcanic emissions with 206pb 207pb ratios reaching up to 1 266 0 002 from 1887 ad to 1898 ad pb concentrations reached 5 pg g 1 and 206pb 207pb ratios decreased to 1 058 0 001 as a result of additional inputs of pb from anthropogenic sources seasonal variability in the late 1880s has been investigated by decoupling volcanic pb from the total measured pb concentrations revealing spring and autumn maxima and consistent winter minima in anthropogenic pb and mineral dust ba concentrations we link this variability to the annual cycle in the position and strength of the antarctic circumpolar trough and the southern ocean westerly winds to the north of the trough region during the autumn and spring seasons these systems increase in strength transporting more impurity laden air from the southern hemisphere continental regions to eastern antarctica and law dome as this pb is isotopically identical to that emitted from south eastern australia broken hill port pirie this implies a relatively direct air trajectory pathway from southern australia to law dome eastern antarctica

one hundred fifty year record of lead isotopes in antarctic snow from coats land a record of the concentrations of pb and ba and the isotopic composition of pb has been established for a remote low accumulation site in the atlantic sector of antarctica coats land by means of thermal ionization mass spectrometry the snow samples cover the period similar to 1840 to 1990 they were taken from the walls of a pit to a depth of 7 8 nu and as a core to 16 m ultraclean procedures were used detailed laboratory subsampling provided both long term secular scale and short term intra annual pb ba and pb isotope variations the results show that there have been significant variations in ph concentrations range 0 1 to 9 3 pg g and isotopic composition range 1 096 to 1 208 for pb 206 pb 207 ratio since the 1840s the data show evidence of pollution for this metal in antarctica as early as the 1880s several pb maxima were observed the first at the beginning of the 20th century and the last in the 1970s to 1980s with a clear decrease during recent years although the last maximum is clearly linked to the rise and fall in the use of leaded gasoline in the southern hemisphere especially in south america the reason for the first remains uncertain the pattern of changing isotopic composition of ph reveals the changing origin and character of the anthropogenic inputs to antarctica an interesting feature in this pattern is the relatively large contribution of unradiogenic pb in the similar to1890s possibly originating from australia another interesting feature is the pronounced intra annual variation in the isotopic composition of pb which illustrates the complexity of the changing inputs of pb to antarctica

a 220 kyr record of pb isotopes at dome c antarctica from analyses of the epica ice core pb isotopic compositions and pb and ba concentrations are reported in epica dome c ice core samples dating to 220 kyr bp indicating that pb isotopic compositions in antarctic ice vary with changing climate 206pb 207pb ratios decrease during glacial periods with the lowest values occurring during colder climatic periods stages 2 4 and 6 and the holocene low pb concentrations 10 pg g were found during cold climatic periods ba a proxy for mineral dust was used to determine that dust usually accounts for 70 of pb in dome c ice while the remaining 30 was attributed to volcanic emissions pb isotopic compositions at dome c differ from those reported in pre industrial ice from other antarctic locations due to greater proportions of dust pb at dome c

deposition of atmospheric heavy metals to the greenland ice sheet from the 1783 1784 volcanic eruption of laki iceland abstract in order to assess better the influence of major volcanic events on the large scale atmospheric cycles of heavy metals greenland ice dated from the time of the fallouts from the great 1783 1784 eruption of laki volcano in iceland has been analysed for pb cd cu zn and sulphate the concentrations of the four heavy metals investigated are found to be greatly enhanced in the ice layers which correspond to the fallouts from the eruption confirming that such events do modify the atmospheric cycles of heavy metals cumulative fallout of heavy metals to the whole greenland ice cap from the 1783 1784 laki eruption ranges from 1 t for pb and cd to 40 t for zn for cd cu and zn it represents a few percent of the cumulative anthropogenic fallout to the ice cap from the industrial revolution to the present

climate related variations in lead concentrations and sources in vostok antarctic ice from 65 000 to 240 000 years bp 1 pb has been measured in various sections of the 3 623 m vostok deep antarctic ice core dated from 65 000 to 240 000 years bp i e back to the beginning of the penultimate ice age and the preceding interglacial isotopic stage 7 5 pb concentrations were highly variable during this time interval with low values down to 0 5 pg g during warm climatic stages and much higher values up to 20 pg g during cold climatic stages especially isotopic stages 4 2 and 6 2 to 6 6 rock and soil dust accounts for virtually 100 of pb measured in the ice during cold climatic stages while the contribution from volcanoes might be significant during warm stages

isotopic identification of natural vs anthropogenic sources of pb in laramie basin groundwaters wyoming usa water well samples precipitation and leachates of aquifer rock samples from the laramie basin wyoming were analyzed to test the suitability of pb isotopes for tracing hydrologic processes in a basin where sr isotopes had proven effective leachable pb from host rocks to aquifers in this basin have isotopically distinct compositions and isotopic tracing would be effective in differentiating natural sources of pb however in almost all cases this natural signal is apparently swamped by anthropogenic pb sources in drilled water wells the isotopic compositions of these samples cannot be produced by any combination of pb in precipitation and leached pb from the aquifers alone but are consistent with mixtures of anthropogenic pb thorogenic 208pb vs uranogenic 206pb 207pb pb was especially useful for discriminating natural from anthropogenic sources for these samples it is strongly recommended that all four pb isotopes be reported in hydrologic and environmental studies that employ this approach

biochronology of the mid pliocene sphaeroidinella event abstract morphological evolution in the late neogene planktonic foraminifer sphaeroidinella lineage involves a sudden increase of the percentage of specimens equipped with supplementary apertures from 70 in the mid pliocene about 3 5 ma this evolutionary transition marked by the first occurrence of specimens with large supplementary apertures in the lineage is denoted the sphaeroidinella event changes in the proportions of the supplementary apertures in the lineage were studied in 24 samples from odp hole 926a drilled in the equatorial atlantic ocean in addition detailed chronological models have been compiled for this section as well as for pliocene sections from dsdp holes 214 502a and 503b where evolution in the lineage have been analyzed previously stratigraphic correlation of the studied sequences suggests that the sphaeroidinella event took place at about 3 6 ma in the eastern equatorial pacific hole 503b and at 3 5 3 6 ma in the caribbean hole 502a while in the atlantic ocean hole 926a and in the indian ocean hole 214 the event occurred after 3 5 ma the inferred diachrony of the mid pliocene sphaeroidinella transition which is considered to represent a prime example of punctuated anagenesis suggests that this evolutionary modality may have an allopatric component its short duration on average less than 50 kyr and the detailed biochronology that could be established for this event qualifies it as a useful biostratigraphic tool in the low latitude pliocene oceans

pb isotope record over one century in snow from victoria land antarctica pb and ba concentrations and pb isotopic compositions are reported for firn core and snow pit samples from victoria land antarctica dating from 1872 ad to 1994 ad from variations in pb ba ratios and pb isotopic compositions two periods of major pb enhancements were identified from 1891 to 1908 ad and from 1948 to 1994 ad the earlier pollution event is attributed to pb emissions from non ferrous metal production and coal combustion in the southern hemisphere and is in excellent agreement with coincident pollution inputs reported in firn ice cores from two other regions of antarctica at coats land and law dome using pb isotopic systematics it was calculated that 50 of pb deposited in victoria land in 1897 originated from anthropogenic emission sources the more recent period of pb enhancements from 1948 to 1994 ad corresponds to the introduction and widespread use of gasoline alkyl pb additives in automobiles in the southern hemisphere with anthropogenic pb inputs averaging 60 of total pb but with large uncertainty intra and inter annual variations in pb concentrations and isotopic compositions were evaluated in snow pits samples corresponding to the period 1991 1994 substantial variations in pb ba and 206pb 207pb ratios were detected but the absence of a regular seasonal pattern for these parameters suggests that the transport and deposition of aerosols to the antarctic ice sheet are complex and vary from year to year

metal emissions from kilauea and a suggested revision of the estimated worldwide metal output by quiescent degassing of volcanoes abstract measurements of a large suite of metals pb cd cu zn and several others and sulfur at kilauea volcano over an extended period of time has yielded a detailed record of the atmospheric injection of ordinarily rare metals from this quiescently degassing volcano representative of an important type we have combined the kilauea data with data of recent studies by others emissions from volcanoes in the indonesian arc the large laki eruption of two centuries ago etna estimates of total volcanic emissions of sulfur to form the basis for a new working estimate of the rate of worldwide injection of metals to the atmosphere by volcanoes the new estimate is that volcanoes inject a substantially smaller mass of ordinarily rare metals into the atmosphere than was stated in a widely cited previous estimate j o nriagu a global assessment of natural sources of atmospheric trace metals nature 338 1989 47 49 our estimate which is an upper limit is an annual injection mass of about 10 000 tons of the metals considered versus the earlier estimate of about 23 000 tons also the proportions of the metals are substantially different in our new estimate