microbe clay interactions as a mechanism for the preservation of organic matter and trace metal biosignatures in black shales abstract organic rich fine grained sedimentary rocks such as black shales are important geochemical archives providing information on the evolution of seawater composition and biological activity over the past 3 billion years while biological productivity and sedimentation rates greatly affect the organic matter content in these rocks mechanisms linking these two processes remain poorly resolved here we examine the interactions of clay minerals with the marine planktonic cyanobacterium synechococcus sp pcc 7002 we suggest that clays settling through the water column could influence carbon and trace metal burial in three ways 1 the interaction of reactive clay surfaces with the bacterial cells increases organic matter deposition via mass increase in a seawater growth medium by several orders of magnitude 2 reactive bacterial cells become completely encased within a clay shroud enhancing the preservation potential of this organic matter and 3 the trace metal content of the biomass buried along with metals sorbed to the clay particles contributes to the trace metal concentrations of the black shale precursor sediments significantly our findings imply that the chemical composition of ancient organic rich fine grained deposits are not only archives of ancient seawater composition and redox state but they also provide a record of the degree of biological activity in the water column through geological time

eolian deposition of trace elements onto taylor valley antarctic glaciers abstract the major ion and trace element chemistry in four 60 110 cm deep snow pits was examined from three antarctic taylor valley glaciers commonwealth canada and howard all located within 20 km of the ross sea taylor valley tv 77 30 s 163 15 e is part of the mcmurdo dry valleys mdv the largest ice free area in antarctica snow chemistry of these glaciers is strongly influenced by cross valley sw ne and ne sw winds that deposit eolian materials including mineral dust and soluble salts arsenic cd cu mo pb sb and sn in recent tv glacier snow are almost exclusively derived from eolian dust the relative magnitude of element variations with depth relate to the exposure of snow sites to prevalent winds eolian deposition is a primary source of these elements to canada glacier snow and supra and proglacial streams eolian processes are likely very important to the delivery and availability of nutrients and potentially toxic elements to dry valley antarctic ecosystems

the occurrence of lead in antarctic recent snow firn deposited over the last two centuries and prehistoric ice concentrations of lead have been measured by ultraclean isotope dilution mass spectrometry in snow cores covering the last two centuries collected at an inland site in east antarctica using an ultra clean all plastic hand operated auger and in a prehistoric blue ice block collected at an antarctic coastal site lead contamination of 16 to 200 pg pb g existed on the outside of the snow cores but the measured concentrations decreased more or less abruptly along a radius from the outside to the centers of the snow cores establishing interior values in the 1 to 5 pg pb g range some of these interior values are however possibly still slightly affected by lead contamination which could have intruded to the center of the cores because of slight melting of some of the snow cores before laboratory analysis the interior of the blue ice block appears not to have been significantly contaminated and contains about 1 7 pg pb g these new data show that most previously published data on lead in antarctic snow and ice were in high positive error because of contamination during field sampling laboratory analysis or both they show that lead concentrations could not have increased in antarctic snows or ice from prehistoric times to present more than 2 to 3 fold confirming that the remote polar areas of the southern hemisphere are still little affected by industrial lead pollution prehistoric antarctic ice is shown to contain about 1 pg pb g natural excess lead above silicate dust lead this excess cannot be entirely accounted for by volcanoes or sea spray which suggests the possible existence of some other unknown natural source of prehistoric excess lead present day mean eolian fallout flux of lead in antarctica is estimated to be about 0 07 ng pb cm 2 yr 1 which stands in about the same proportion to that in the south pacific westerlies about 1 30 as the flux in greenland is observed to stand to those in the north pacific and north atlantic westerlies

past and recent changes in the large scale tropospheric cycles of lead and other heavy metals as documented in antarctic and greenland snow and ice a review abstract the investigation of the occurrence of lead and other heavy metals in antarctic and greenland ancient ice and recent snow is of great interest in reconstructing the past natural tropospheric cycles of these metals and determining to what extent these cycles have now been altered by man because concentrations to be measured are exceedingly low down to the sub pg g level reliable data can however be obtained only if full control of contamination is achieved from field sampling to laboratory analysis the available data show that the past natural concentrations of pb cd zn cu and hg in antarctic ancient ice are highly dependent upon climatic conditions the highest values occurring during the coldest periods of the ice ages especially during the last glacial maximum about 18 000 years ago human activity has led to an increase in lead concentrations during recent centuries both in antarctica tenfold increase and in greenland two hundredfold increase this last increase was followed by a 7 5 fold decrease during the past two decades mainly as a consequence of the rapid fall in the use of lead alkyl additives in the usa as confirmed by recent isotopic data

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

storm surge versus turbidite origin of the coniacian to santonian sediments in the eastern part of the bohemian cretaceous basin a flyschoid facies occurs in the b ezno formation coniacian up to santonian of the eastern marginal part of the bohemian cretaceous basin according tojerzykiewicz 1970 1971 this facies is of deep water turbidite origin he based his interpretation on the study of sedimentary structures new palaeogeographic reconstruction of lithofacies relations investigation of deep drillings and detailed sedimentological analysis however allowed new results concerning the sedimentary environments and depositional mechanism of this facies according to the new model presented here this flyschoid facies was deposited in a shallow marine environment clayey sedimentation was the natural response to normal environmental conditions whereas sandstone intercalations reflect anomalous conditions during heavy storms during these events sands were transported basinwards up to distances of 25 km with normal bottom currents as well as turbidity currents acted as transporting mechanisms this flyschoid facies corresponds to other examples of clayey sequences with sandy storm layers

changes in atmospheric heavy metals and metalloids in dome c east antarctica ice back to 672 0 kyr bp marine isotopic stages 16 2 cu zn as cd pb and bi were determined by inductively coupled plasma sector field mass spectrometry icp sfms in seventy seven sections of the 3270 m deep ice core drilled at dome c at an altitude of 3233 m on the east antarctic plateau as part of the european program for ice coring in antarctica epica the depth of the section ranged from 2368 85 m 263 6 kyr bp to 3062 13 m 672 0 kyr bp when combined with data previously obtained for the upper part of the core it gives a detailed record of past natural variations in the concentrations of these heavy metals during the last eight climatic cycles from the holocene back to marine isotopic stage mis 16 2 concentrations of all metals are found to have strongly varied for cu pb bi and possibly zn concentrations appear to be closely linked with climate conditions with high values during glacial maxima and much lower values during interglacials the situation is less clear for as and cd for which variations are less clearly linked with climate conditions rock and soil dust appears to be the main source of cu zn bi and pb during glacial maxima and a significant source for these metals during interglacials while as cd and bi present a more complex inputs from several sources with a particularly significant impact of volcanism

sediment transport in the new york bight north american atlantic shelf vincent c e swift d j p and hillard b 1981 sediment transport in the new york bight north american atlantic shelf mar geol 42 369 398 aanderaa current meter data collected during the course of noaa s new york bight project are sufficiently extensive in time 135000 observation hours and space 41 stations to permit an estimate of the sediment transport in this area the analysis is based on mean flow observations the role of wave oscillatory currents in resuspending sediment is considered but not explicitly included in the sediment transport calculations an estimate of the potential sediment transport rate qb at each station for three different threshold velocities uth 12 16 and 20 cm s 1 were made using a bagnoldtype transport equation qb const uc uth 3 for uc uth qb 0 for uc uth where uc is the mean current speed comparison was made between the results from this simple equation and other bedload and suspended load transport rates which include wave data for a limited subset of the bight data this comparison indicates that the bagnold results are reasonable for the along isobath transport estimates but are not reliable for the cross isobath transport in the cross isobath direction waves appear to play a dominant role in determining the transport rate the comparison also indicates that the bagnold approach tends to overestimate transport in deep water in shallow water resuspension of sand and rotor pumping of current meters both may become important and sediment transport calculations may not be accurate fine sediment suspended transport is approximately double the potential bedload transport for fine sand 0 02 cm but does not dominate the total transport as is believed to occur on the washington shelf smith and hopkins 1972 the data show that the new york bight is a storm dominated shelf with the general southwestward drift of water 6 cm s 1 modulated by more intense storm induced flows the transport calculations indicate that the bulk of sediment transport occurs during the winter months when wind stress is at a maximum and the water column is well mixed two major transport provinces are present a the hudson shelf valley and b the rest of the shelf the shelf valley acts as a sink and a barrier to the continuity of the mainly southwestward transport of sediment 104 g cm 1 yr 1 along the shelf within the valley the potential transport of material is of the order of l05 g cm 1 yr 1 along the valley axis progressive vector transport paths for fine sediment indicate that removal of sediment out of the ends of the valley can occur rapidly however consider ation of the finesediment budget for the whole hudson shelf valley and of the attenua tion of wave activity with depth show that these results are not inconsistent with the presence of high mud concentrations in the valley up valley sediment rates predominate during the period for which data are available

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

cadmium copper cobalt nickel lead and zinc in the water column of the weddell sea antarctica abstract this paper presents results from the first complete investigation of the dissolved and suspended trace metals cadmium copper cobalt nickel lead and zinc in the water column of the weddell sea antarctica a total of 35 stations was covered in the central weddell sea and the shelf areas around the filchner depression and dronning mauds land snow samples were collected from the sea ice and from the antarctic continent to evaluate the importance of the fresh water influence on the weddell sea oceanographic data i e salinity temperature and nutrients are used to link the trace metal results to the different water masses the general range found is for cadmium 0 5 0 8 nm copper 2 0 2 9 nm cobalt 20 40 nm nickel 6 7 nm lead 10 pm zinc 3 7 nm the suspended trace metals are a small fraction but considerably higher than in other oceans the lowest concentrations of cadmium copper and zinc are found in the surface layer and in the whole water column at the filchner depression cobalt shows an increase in the surface water compared to the deep water this is suggested to be generated by the terrogent material from the antarctic continent from the melting of the ice no evidence of anthropogenic lead can be seen in the lead profile nutrient trace metal relations found show poor statistical correlation in contrast to what is found in other oceans this assumes that cadmium copper and zinc are not directly linked to the bioproduction cycle however the nutrient trace metal ratios found support the theory that the weddell sea is the ultimate source for generation of the nutrient trace metal ratios in the pacific ocean

high resolution swath sonar investigation of sand ridge dune and ribbon morphology in the offshore environment of the new jersey margin abstract sand ridges on the northeast us atlantic shelf form in the near shore environment most likely in response to storm driven flows as the holocene transgression has continued the ridges have been transferred to an offshore hydrodynamic regime where currents are not constrained by the coast and storms do not influence bottom currents as frequently or as strongly here we qualitatively and quantitatively investigate the morphology of offshore sand ridges and smaller scale features in an effort to place constraints on bedform development in these deeper waters a recent high resolution swath sonar survey mapped a portion of the new jersey shelf from 20 m water depth to the shelf break 120 m imaging both sand ridges and smaller scaled dunes and ribbons in far greater detail than has been previously possible using a robust statistical analysis we find that the gross morphology of ridges height width length does not change with depth beyond 20 m water depth and changes in ridge orientation generally mirror changes in regional contour orientation hence ridges have not continued to grow since transgression has brought them into the offshore hydrodynamic regime however on the inner shelf 20 m water depth to the mid shelf shore we do find evidence in the ridge shape which has an asymmetry opposite to that seen near shore and in the complex backscatter response that some important modifications to ridges are taking place at these water depths in contrast on the mid shelf from the mid shelf shore to the franklin shore ridges tend to have higher backscatter at the crests implying that these are largely winnowed relict features lineated smaller scale 100 500 m wavelength

direct evidence for organic carbon preservation as clay organic nanocomposites in a devonian black shale from deposition to diagenesis abstract the burial of marine sourced organic carbon oc in continental margin sediments is most commonly linked to oceanographic regulation of bottom water oxygenation anoxia and or biological productivity here we show an additional influence in the devonian woodford shale in which oc occurs as nanometer intercalations with specific phyllosilicate minerals mixed layer illite smectite that we term organo mineral nanocomposites high resolution transmission electron microscopic hrtem images provide direct evidence of this nano scale relationship while discrete micron scale organic particles such as tasmanites algal cysts are present in some lamina a strong relation between total organic carbon toc and mineral surface area msa over a range of 15 toc indicate that the dominant association of organic carbon is with mineral surfaces and not as discrete pelagic grains consistent with hrtem images of nanocomposites where periods of oxygenation are indicated by bioturbation this relationship is modified by a shift to lower oc loading on mineral surfaces and reduced msa variability likely resulting from biological mixing and homogenization of the sediment oxidative burn down of oc and or stripping of oc from minerals in animal guts the toc msa relationship extends across a range of burial depths and thermal maturities into the oil window and persists through partial illitization where illitization occurs the loss of mineral surface area associated with the collapse of smectite interlayer space results in a systematic increase in toc msa and reorganization of organic carbon and clays into nano scale aggregates while the woodford shale is representative of black shale deposits commonly thought to record heightened marine productivity and or anoxia our results point to the importance of high surface area clay minerals for oc enrichment given that the vast majority of these clay minerals are formed in soils before being transported to continental margin settings their mineralogy and attendant preservative potential is primarily a function of continental climate and provenance making these deposits a sensitive recorder of land as well as oceanographic change

organic carbon carbonate and clay mineral distributions in eastern central arctic ocean surface sediments abstract results from a detailed sedimentological investigation of surface sediments from the eastern arctic ocean indicate that the distribution of different types of sediment facies is controlled by different environmental processes such as sea ice distribution terrigenous sediment supply oceanic currents and surface water productivity in comparison to other open ocean environments total organic carbon contents are high with maximum values in some deep basin areas as well as west and north of svalbard in general the organic carbon fraction is dominated by terrigenous material as indicated by low hydrogen index values and high c n ratios probably transported by currents and or sea ice from the eurasian shelf areas the amount of marine organic carbon is of secondary importance reflecting the low productivity environment described for the modern ice covered arctic ocean in the area north of svalbard some higher amounts of marine organic matter may indicate increased surface water productivity controlled by the inflow of the warm westspitsbergen current wsc into the arctic ocean and reduced sea ice cover this influence of the wsc is also supported by the high content of biogenic carbonate recorded in the yermak plateau area the clay mineral distribution gives information about different source areas and transport mechanisms illite the dominant clay mineral in the eastern central arctic ocean sediments reaches maximum values in the morris jesup rise area and around svalbard indicating north greenland and svalbard to be most probable source areas kaolinite reaches maximum values in the nansen basin east of svalbard and in the barents sea possible source areas are mesozoic sediments in the barents sea and franz josef land in contrast to the high smectite values determined in sea ice samples smectite contents are generally very low in the underlying surface sediments suggesting that the supply by sea ice is not the dominant mechanism for clay accumulation in the studied area of the modern central arctic ocean

the occurrence of zinc in antarctic ancient ice and recent snow concentrations of zinc zn have been measured in various sections of the dome c and vostok deep antarctic ice cores whose ages range from 3850 to 155 000 years bp and in several large size surface antarctic snow blocks collected in adelie land and at the geographic south pole all the samples were mechanically decontaminated and detailed outside inside variation profiles were drawn for most of them then allowing us to clearly establish the accuracy of the data obtained from the analysis of the most central parts of each individual core section or snow block natural zn concentrations are found to have strongly varied in antarctic ice during the past 155 000 years the highest values up to about 100 pg zn g being observed during the last glacial maximum and possibly during the end of the next to last ice age wind blown dust from crustal rock and soil appears to be the main natural source of zn during the glacial periods especially the last glacial maximum zn concentrations in present day antarctic snow from central east antarctica about 5 pg zn g are found to be comparable with those in holocene ice several thousand years old which evidences that the antarctic tropospheric cell is still little affected by anthropogenic zn

change of the point of zero net proton charge phpznpc of clay minerals with ionic strength abstract in a system where protons and hydroxide ions are the only aqueous species the point of zero net proton charge phpznpc of a mineral defines the ph at which the positively and negatively charged functional groups on its surface are equal drever 1997 ascertaining the phpznpc of clay minerals a ubiquitous component in soils sediment and rivers is useful in predicting its electrostatic interactions with charged aqueous species colloids and bacteria while the phpznpc values of most clays have been reported the variation of phpznpc with changing solution ionic strength is and the mathematic relationship between them are not well understood but critical in assessing the surface reactivity of clays in aqueous solutions ranging from freshwater to brines to address this gap we studied the relationship of the phpznpc of three clay minerals kaolinite illite and montmorillonite at seven ionic strengths from 0 001 to 0 1 m titration data for each clay were used to calculate the phpznpc by two methods previously documented in literature 1 using the difference between the blank titration and clay titrations and 2 by the difference between the number of protons added during titration and the number of protons remaining in solution the results show that 1 unlike simple metal oxides e g hematite gibbsite quartz titration curves of clay minerals at different is do not intersect at a common phpznpc value 2 the phpznpc for kaolinite is around 5 6 to 6 6 while the phpznpc for illite and montmorillonite is in the range of 9 to10 3 the phpznpc value decreases systematically with increasing is for all three clay minerals studied and 4 the change of phpznpc is linear with log is a third method using surface complexation modeling scm approach was applied to calculate the phpznpc of the clay minerals and the results match well with method 2 our results allow for a more accurate estimation of clay surface charge property in aqueous environment which in turn will improve model predictions of the adsorption of charged species in systems in which ionic strength changes

an undulatory discontinuity surface on a gently inclined muddy ramp possible evidence of secondary helical flow from the geological record an unusual somewhat cryptic undulatory discontinuity has been recognized near the basal contact of the wanakah shale member of the middle devonian ludlowville formation in western new york it is in part marked by undulating diagenetic limestone beds and concretionary horizons but can be traced continuously by subtle surfaces of fossil and pyritic lags this surface marks the top of parallel elongate mud ridges trending approximately n s perpendicular to the inferred e w depositional strike of the appalachian basin in western new york these ridges are observed in the field as irregularly spaced mud swells which have up to 1 5 m of relief and vary from 30 to 50 m or more in width the intervening broad flat channel floors are characterized by dense concentrations of diminutive brachiopods with gastropods and styliolinids which are gradually replaced by thin styliolinid horizons with abundant pyrite nodules and pyritized burrows over the tops of the swells traceable shelly horizons are observed to pinch out over the swells suggesting a period of relatively undisturbed sediment filling following the formation of the channellized surface the interval of nearly barren shale below this irregular surface however contains concretionary horizons and rare styliolinid pavements which are themselves irregular possibly indicating a changing topography for this surface through time previous taphonomic and palaeoecological studies of the lower wanakah shale member have disclosed a well defined regressive transgressive cycle with more subtle superimposed subcycles the undulatory surface described here occurs within the early regressive part of this cycle and appears to record an accentuated regressive kick of a lower order subcycle the formation of this surface is therefore interpreted to be a consequence of regressive submarine erosion and sediment bypass together with redeposition from suspension the development of the channels and parallel longitudinal mud ridges was probably controlled by helical flow cells within offshore directed bottom currents they may be the first recorded instance of sedimentary furrows described from the geological record taphonomic and biofacies data indicate relative depths below average storm wave base suggesting that sediment winnowing and redeposition occurred at depths only rarely affected by the direct impact of storm wave agitation

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

acid base properties of kaolinite montmorillonite and illite at marine ionic strength abstract in marginal marine settings understanding the role that clay minerals play in the transfer of metal cations from the water column to the seafloor is important if the composition of modern muds is to be used as a proxy for the precursors of ancient shale deposits in this study we conducted potentiometric titrations of three naturally abundant clay minerals kaolinite montmorillonite and illite in 0 56 m nacl electrolyte solutions to ascertain the surface reactivity of each clay mineral at seawater ionic strength our results demonstrate that all three clay minerals were increasingly anionic as ph increases from 3 to 9 with montmorillonite having the highest negative charge the potentiometric titrations and adsorption data were modeled using both non electrostatic nem and electrostatic constant capacitance model ccm surface complexation models scms a two site surface complexation model that included one basal siloxane surface site x and one amphoteric edge site soh provided an excellent fit for the protonation data of each mineral cd ii adsorption experiments were conducted to quantify the magnitude of cation adsorption which showed that 10 g montmorillonite illite and kaolinite powder could bind an equivalent of 4 7 10 4 g 4 3 10 4 g and 4 0 10 4 g of cd respectively under conditions relevant to seawater initial cd concentration of 8 9 10 6 m and ph 8 to place this value into the context of modern riverine clay inputs to the ocean 13 5 109 tons of total suspended sediment are deposited annually milliman and meade 1983 of which 10 to 25 is clay manheim et al 1970 schroeder et al 2015 the total amount of cd adsorbed to suspended clay minerals entering the modern oceans could then amount to approximately 104 to 105 tons per year the results of this study highlight the potential role of clay minerals in transporting metals from the ocean water column to the seafloor

distribution of metals between particulate and gaseous forms in a volcanic plume in order to gain information on the distribution of metals between particles and gaseous forms in the plume of kilauea volcano a filter designed to collect metals associated with particles was followed in series by two other collectors intended to trap metals present in gaseous atomic molecular or complexed form first an acid bubbler bath and then a cold trap of the six metals measured all of the in tl and bi and almost all of the cd pb and cu were found on the filter none of any of the metals was detected in the acid bubbler bath masses equivalent to 0 3 of the amount of cd on the filter 0 4 of the amount of pb and 9 3 of the cu were measured in the cold trap the results indicate that all or nearly all of the six metals were partitioned to the particulate portion of the physical mixture of gases and particles that constitutes a volcanic plume but that there may be systematic differences between chalcophile metals in the ways they are partitioned between particulate and gaseous phases in a cooled plume and possibly differences in the acidity or other chemical properties of the molecular phases

changes in cadmium concentrations in antarctic ice and snow during the past 155 000 years changes in cd concentrations in antarctic ice and snow during the last full climatic cycle the past 155 000 yrs have been investigated by analysing various sections of the dome c and vostok deep antarctic ice cores and several blocks of recent antarctic snow each sample was mechanically decontaminated using ultraclean procedures and then analysed for cd by the new ultrasensitive laser excited atomic fluorescence technique cd concentrations are found to have been highly variable in ancient antarctic ice and therefore in the past pristine south polar atmosphere during the last climatic cycle the highest values being observed during the cold terminal stages of the last and next to last ice ages concentrations measured in recent antarctic snows are comparable with those in antarctic holocene ice several thousand years old which suggests that the anthropogenic influence is probably still negligible for this heavy metal in the south polar atmosphere for some of the samples measured cd concentrations can be simply accounted for by rock and soil dust and volcanic emissions while for others there is a significant excess over the contributions from these two sources

ice age storm trajectories inferred from radar stratigraphy at taylor dome antarctica the taylor dome ice core east antarctica provides a climate record that extends through the previous interglacial we use ice dynamics modeling and geochemical records to infer the local accumulation rate history a pronounced accumulation reduction occurred during the last glacial maximum lgm the spatial gradient of accumulation across the surface of taylor dome indicates the modern local prevailing storm direction radar internal layering shows that this gradient was reversed during the lgm suggesting a reorganization of synoptic weather systems occurred possibly linked to the advance and retreat of the west antarctic ice sheet

cenozoic changes in atmospheric lead recorded in central pacific ferromanganese crusts the possible sources of pre anthropogenic pb contributed to the world s oceans have been the focus of considerable study the role of eolian dust versus riverine inputs has been of particular interest with better calibration of isotopic records from central pacific ferromanganese crusts using os isotope stratigraphy it now appears that deep water pb isotopic compositions were effectively homogeneous over a distance of 5000 km for the past 80 myr the composition shifted slightly from high 206pb 204pb ratios in the range of 18 87 0 02 before 65 ma to lower values of 18 62 0 02 by 45 ma and then gradually increased again very slightly to the present day ratio of 18 67 0 02 the regional homogeneity provides evidence of a dominant well mixed atmospheric source the most likely candidate for which is volcanic aerosols contributed either directly or as soluble condensates on eolian dust the slight shift in pb isotope composition of deep waters in the central pacific between 65 and 45 ma may be the result of a regional or perhaps global scale change in the sources of volcanic exhalations and volcanic activity caused by an increase in the importance of melting and assimilation of older continental crustal components over the cenozoic

climate related variations in atmospheric sb and tl in the epica dome c ice east antarctica during the past 800 000 years 1 a record of antimony sb and thallium tl from the european project for ice coring in antarctica epica dome c antarctic ice core provides the characteristics of climate related natural changes in concentrations and fluxes of these toxic elements over the time period back to marine isotope stage 20 2 800 kyr b p a strong variability in concentrations and fluxes are observed for both elements with considerably higher values during glacial maxima and lower values during intermediate and warm periods rock and soil dust accounts for on average 58 of sb and 76 of tl in ice during glacial maxima this contribution remains significant during warm periods accounting for 21 for sb and 27 for tl the contribution from volcanoes appears to be very important particularly for tl when climatic conditions become warmer with an estimated volcanic contribution of 72 for tl during interglacials the sea salt contribution is significant for sb particularly during intermediate climatic periods with an average contribution of 17 this sea salt contribution is most likely caused by greater production of sea salt from highly saline frost flowers and relatively more efficient transport of sb enriched sea ice salt from source areas on the east antarctic plateau our ice core data along with snow data recently reported from the antarctic snow layers at dome fuji shows that the present day sb flux 6 6 ng m2 yr is approximately double the highest natural level 2 8 ng m2 yr during glacial maxima throughout the last successive eight glacial interglacial cycles this result indicates that human activity has induced the greatest perturbation of the atmospheric cycle of sb ever experienced over a period of 800 kyr in the most remote area on earth

past natural changes in cu zn and cd in vostok antarctic ice dated back to the penultimate interglacial period 1 improved ice core decontamination procedures have allowed us to obtain the first reliable data on cu zn and cd in ancient antarctic ice drilled in a fluid filled hole at vostok station dated back to the beginning of the next to last ice age 240 000 years ago cu zn and cd concentrations and fallout fluxes display very large natural variations by up to a factor of 35 with high values obtained during the coldest climatic stages and much lower values during warm climatic stages crustal dust was an important source of cu and zn during the coldest climatic stages and volcanic emissions were probably an important source of cd both during warm and cold periods

changes in natural lead copper zinc and cadmium concentrations in central greenland ice from 8250 to 149 100 years ago their association with climatic changes and resultant variations of dominant source contributions abstract we present here the first reliable time series of pb cu zn and cd in greenland ice for the last climatic cycle they were obtained by analysing various sections of the 3028 8 m grip deep ice core drilled at summit central greenland our results show that climatic changes have led to large variations in the concentrations of natural pb cu zn and cd in the high latitude troposphere of the northern hemisphere between the interglacial and glacial periods concentrations have varied by factors of 320 for pb 100 for cu 36 for zn and 13 for cd based on a good correlation between each heavy metal and al pb and cu are found to have mainly originated from soil and rock dust for both glacial and interglacial periods on the other hand continental biogenic emissions were the main source of cd and to a lesser extent zn in the arctic troposphere during the warm eemian and the pre boreal to holocene transition whereas wind blown dust was the predominant source for these two metals during the cold glacial climatic stages this characteristic change of relative cd and zn contributions from different sources in contrast to that for pb and cu is well documented in the ice from the last deglaciation period 15 000 to 8250 yrs ago after the younger dryas event ended a remarkable increase of cd al and zn al ratios occurred from 13 000 to 9300 yrs ago which is consistent with the progressive expansion of vegetation following the retreat of the north american and north eurasian ice sheets the subsequent decrease of these ratios to holocene values can be explained by the stabilization of atmospheric circulation in the northern high latitude regions which became similar to that for the holocene due to further reduction of the laurentide ice sheet finally the observed variations of the metal al ratios suggest changes in the soil and rock dust source regions in parallel with climatic changes which have altered the mean composition of the crustal particles transported to the arctic

discovery of two new large submarine canyons in the bering sea abstract the beringian continental margin is incised by some of the world s largest submarine canyons two newly discovered canyons st matthew and middle are hereby added to the roster of bering sea canyons although these canyons are smaller and not cut back into the bering shelf like the five very large canyons they are nonetheless comparable in size to most of the canyons that have been cut into the u s eastern continental margin and much larger than the well known southern california canyons both igneous and sedimentary rocks of eocene to pliocene age have been dredged from the walls of st matthew and middle canyons as well as from the walls of several of the other beringian margin canyons thus suggesting a late tertiary to quaternary genesis of the canyons we speculate that the ancestral yukon and possibly anadyr rivers were instrumental in initiating the canyon cutting processes but that due to restrictions imposed by island and subsea bedrock barriers cutting of the two newly discovered canyons may have begun later and been slower than for the other five canyons

lead ba and bi in antarctic law dome ice corresponding to the 1815 ad tambora eruption an assessment of emission sources using pb isotopes lead ba and bi concentrations and pb isotopic compositions have been measured in antarctic law dome 66 8 s 112 4 e ice dated from 1814 ad to 1819 ad by thermal ionisation mass spectrometry to investigate the possible deposition of heavy metals from the 1815 ad eruption of tambora volcano 8 5 s 117 4 e in indonesia although volcanic s emissions from tambora observed as so42 are present in the antarctic ice core record there are grounds to question the origin of the pb and bi also deposited at law dome from late 1817 as the pb isotope data suggest this pb originated from mount erebus 77 5 s 167 2 e on ross island antarctica it is shown that at least 97 of any pb and bi emitted from tambora was removed from the atmosphere within the 1 6 year period required to transport aerosols from indonesia to antarctica consequently increased pb and bi concentrations observed in law dome ice about 1818 ad are attributed to either increased heavy metal emissions from mount erebus or increased fluxes of heavy metals to the antarctic ice sheet resulting from climate and meteorological modifications following the tambora eruption elevated ba concentrations observed from mid 1816 to mid 1818 indicate increased atmospheric loading of rock and soil dust also occurred at the time

isotopic constraints on the source of argentinian loess with implications for atmospheric circulation and the provenance of antarctic dust during recent glacial maxima we present rare earth element ree and sr nd isotopic data for argentinian loess 28 38 s with two aims 1 to examine the source regions of argentinian loess and the constraints that these put on palaeo wind directions 2 to further investigate the source of antarctic ice core dust and to test the hypothesis that some of it could be derived from a region to the north of patagonia into which the dry dusty westerly dominated patagonian climate expanded during quaternary glacial maxima sr nd isotopic data for argentinian loess from north of 37 s are distinct from patagonian loess compositions in that they have more radiogenic sr 87sr 86sr 0 7059 0 7123 and less radiogenic nd nd 0 8 to 6 4 ree patterns and sr nd isotopic values are relatively homogeneous for multiple samples taken from single loess sections but show significant differences between sections in general there is a northward change from patagonia like ree patterns and isotopic values away from volcanogenic signatures and towards those that are more like the continental crust the latitudinal nd isotopic pattern is remarkably similar to that for andean volcanic rocks and suggests derivation of loess from the andes by more or less direct westerly transport for loess sections in the north the data imply a contribution from palaeozoic gneisses to the northwest in the chilean altiplano sr nd data for extra patagonian argentinian loess north of 37 s do not support a significant role for this source region in supplying dust to antarctica at the last glacial maximum this conclusion contrasts with previous studies that suggest a significant northward shift in the climatic belts and in particular the westerlies and the antarctic polar front during quaternary glacial maxima very systematic relations between the sr nd isotopic composition of loess and their andean source highlights shifts in the sr isotopic composition of loess to more radiogenic values and strongly suggests that the slight offset between patagonian loess and ice core dust identified by previous workers is due to grain size differentiation effects

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

a comparison of deep antarctic ice cores and their implications for climate between 65 000 and 15 000 years ago abstract three ice cores drilled in the central part of the antarctic continent extend back to the last glacial period one from west antarctica byrd and two from east antarctica vostok and dome c this period is also partly covered by a few cores from the coastal areas in these cores climatic information is mostly derived from the isotopic profiles d or 18 o from which surface temperature and more indirectly precipitation rate can be estimated the main objective has been to compare thoroughly the three deep ice cores for the main part of the last glacial period from ca 65 000 15 000 yr b p the time scales have been examined in detail and a new 40 000 yr chronology for the dome c core adopted special emphasis is placed on the link between the concentration of 10 be and past accumulation changes and on the use of peaks in the concentration of this cosmogenic isotope as stratigraphic markers elevation changes of the ice sheet derived from gas content and isotopic data bear directly on interpretations of past temperature and precipitation rate changes

synchronous climate changes in antarctica and the north atlantic central greenland ice cores provide evidence of abrupt changes in climate over the past 100 000 years many of these changes have also been identified in sedimentary and geochemical signatures in deep sea sediment cores from the north atlantic confirming the link between millennial scale climate variability and ocean thermohaline circulation it is shown here that two of the most prominent north atlantic events the rapid warming that marks the end of the last glacial period and the bolling allerod younger dryas oscillation are also recorded in an ice core from taylor dome in the western ross sea sector of antarctica this result contrasts with evidence from ice cores in other regions of antarctica which show an asynchronous response between the northern and southern hemispheres

the hudson shelf valley its role in shelf sediment transport abstract freeland g l stanley d j swift d j p and lambert d n 1981 the hudson shelf valley its role in shelf sediment transport mar geol 42 399 427 the hudson shelf valley was deeply incised by pleistocene lowstands of the sea during the holocene transgression fluvial estuarine and estuary mouth depositional environments were displaced landward and sedimentation in these environments partially filled the valley holocene sediment thickness in the seaward half of the valley is about the same as on the shelf to either side but in the landward half of the valley 22 m of sediment is present versus 5 10 m on the adjacent shelf sediment volume calculations in the upper shelf valley show that there is about three times the infill volume east of the thalweg as compared to the infill to the west this configuration indicates that the valley has served as a sediment trap and records the westward migration of the thalweg during the holocene most of the infill was the result of littoral drift which transported sand westward along the south shore of long island during the holocene transgression modern sediment transport as calculated from current meter observations and inferred from bedform observations is mainly south westward along the regional trend of the isobaths and across the shelf valley therefore infill on the eastern side of the shelf valley is continuing at present observations of the regional distribution of sediment types indicate that the asymmetrical valley fill is part of a pattern of bottom response to flow the former drainage divides on both sides of the shelf valley are surfaced by coarse lag deposits on slopes facing northeast into the direction from which the major storm flows come while the down current sides are mantled with fine sand

fluxes of clay minerals in the south china sea abstract in order to assess dominant settling processes that change the composition of the detrital clay fraction during transport from neighboring estuaries to a deep sea basin we studied relative clay mineral abundances and absolute clay mineral fluxes of clay sized sinking particulate matter collected by eight sediment trap systems deployed from shallow to deep water depth in the south china sea this is the first basin wide study on recent sedimentation processes in the western pacific marginal seas annual averages of relative clay mineral abundances at the shallow traps are temporally more variable and regionally more diverse resembling those of surrounding drainage basins in contrast higher fluxes of material reach the deeper traps their characteristics trend temporally and spatially towards uniformity and are enriched with smectite in the entire deep basin sinking particulate matter that reaches the shallow traps spends less time in pelagic transport and is affected by monsoonal current reversals the enrichment in smectite in the deeper traps is a result of longer duration in transport at low velocities which may increase the effect of differential settling during transport the trend is caused by lateral advection driven by the cyclonic deep circulation and this is considered as the main transport process in the northern and central deep basin the high fluxes in the south western deep basin could be the result of laterally advected re suspended sediments from the neighboring shelves the effects on the composition of the detrital clay fraction caused by oceanographic control which indirectly include those by differential settling mask the climatic signal from surrounding drainage basins in the deep basin sediments this strongly affects the interpretation of the clay mineralogical record in sediments deposited under recent conditions in the south china sea deep basin

dating the vostok ice core by an inverse method using the chronological information available in the vostok records we apply an inverse method to assess the quality of the vostok glaciological timescale the inversion procedure provides not only an optimized glaciological timescale and its confidence interval but also a reliable estimate of the duration of successive events our results highlight a disagreement between orbitally tuned and glaciological timescales below 2700 m i e 250 kyr b p thousands of years before present this disagreement could be caused by some discontinuity in the spatial variation of accumulation upstream of vostok moreover the stratigraphic datings of central greenland ice cores grip and gisp2 appear older than our optimized timescale for the late glacial this underlines an unconsistency between the physical assumptions used to construct the vostok glaciological timescale and the stratigraphic datings the inverse method allows the first assessment of the evolution of the phase between vostok climatic records and insolation this phase significantly varies with time which gives a measure of the nonlinear character of the climatic system and suggests that the climatic response to orbital forcing is of different nature for glacial and interglacial periods we confirm that the last interglacial as recorded in the vostok deuterium record was long 16 2 2 kyr thousands of years however midtransition of termination ii occurred at 133 4 2 5 kyr bp which does not support the recent claim for an earlier deglaciation finally our study suggests that temperature changes are correctly estimated when using the spatial present day deuterium temperature relationship to interpret the vostok deuterium record

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

composition and sources of atmospheric dusts in snow at 3200 meters in the st elias range southeastern alaska usa abstract dusts in snow from the accumulation zone in the st elias range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition these dusts with respect to their composition and to the moderate degree of variation that occurs through a depositional year are similar those deposited in greenland the high portion of the st elias range is isolated from dominance by any local dust source terranes because of altitude and the extent of the surrounding glacierized and snow covered region in greenland the altitude is typically lower but local sources are even less likely to dominate the character of the dusts deposited into the ice record there the similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial period conditions are uniform and representative of a broad regional or even hemispheric background dust the dusts in the snow were measured by means of a suite of major minor and trace rock forming metals chosen to give information about rock types their constituent minerals degree of degradation weathering and energies of atmospheric uptake from source the variations in amounts of rock dust through the year in the st elias range snowpack have no time stratigraphic correspondence to the also large variations in concentrations of other species that are not constituents of rock derived dusts such the anions chloride sulfate and nitrate the highs and lows of the two types of materials are apparently completely independent the structure revealed by the moderately fine scale sampling of the present study 10 increments y serves as a background for the interpretation of analysis of ice core samples in which annual layers may be too compressed to permit analysis of sub annual samples

ultra low rare earth element content in accreted ice from sub glacial lake vostok antarctica this paper reports the first rare earth element ree concentrations in accreted ice refrozen from sub glacial lake vostok east antarctica ree were determined in various sections of the vostok ice core in order to geochemically characterize its impurities samples were obtained from accreted ice and for comparison from the upper glacier ice of atmospheric origin undisturbed disturbed and glacial flour ice ree concentrations ranged between 0 8 56 pg g 1 for ce and 0 0035 0 24 pg g 1 for lu in glacier ice and between 0 1 24 pg g 1 for ce and 0 0004 0 02 pg g 1 for lu in accreted ice interestingly the ree concentrations in the upper accreted ice ac1 characterized by visible aggregates containing a mixture of very fine terrigenous particles and in the deeper accreted ice ac2 characterized by transparent ice are lower than those in fresh water and seawater respectively we suggest that such ultra low concentrations are unlikely to be representative of the real ree content in lake vostok but instead may reflect phase exclusion processes occurring at the ice water interface during refreezing in particular the uneven spatial distribution on the order of a few cm and the large range of ree concentrations observed in ac1 are consistent with the occurrence absence of the aggregates in adjacent ice and point to the presence of solid phase concentration exclusion processes occurring within separate pockets of frazil ice during ac1 formation interestingly if the lree enrichment found in ac1 was not produced by chemical fractionation occurring in lake vostok water this may reflect a contribution of bedrock material possibly in combination with aeolian dust released into the lake by melting of the glacier ice collectively this valuable information provides new insight into the accreted ice formation processes the bedrock geology of east antarctica as well as the water chemistry and circulation of lake vostok

fractionation of families of major minor and trace metals across the melt vapor interface in volcanic exhalations chemical families of metals fractionate systematically as they pass from a silicate melt across the interface with the vapor phase and on into a cooled volcanic plume we measured three groups of metals in a small suite of samples collected on filters from the plumes of kilauea hawaii usa etna sicily and merapi java volcanoes these were the major minor and trace metals of the alkali and alkaline earth families k rb cs ca sr ba a group of ordinarily rare metals cd cu in pb tl that are related by their chalcophile affinities and the radon daughter nuclides 210po 210bi and 210pb the measurements show the range and some details of systematic melt vapor fractionation within and between these groups of metals in the plumes of all three volcanoes the alkali metals are much more abundant than the alkaline earth metals in the kilauea plume the alkali metals are at least six times more abundant than the alkaline earth metals relative to abundances in the melt at etna the factor is at least 300 fractionations within each family are commonly also distinctive in the kilauea plume in addition to the whole alkaline earth family being depleted the heaviest metals of the family sr ba are progressively more depleted than the light metal ca in plumes of fumaroles at merapi k cs ratios were approximately three orders of magnitude smaller than found in other earth materials this may represent the largest observed enrichment of the light ion lithophile lil metals changes in metal ratios were seen through the time of eruption in the plumes of kilauea and etna this may reflect degree of degassing of volatiles with which metals complex from the magma bodies at kilauea the changes in fractionation were seen over about three years fractionation within the alkaline earth family increased and that between the two families decreased over that time all of the ordinarily rare chalcophile metals measured are extremely abundant in volcanic plumes and cd and tl are enriched relative to the others indium is much more abundant in the plume of the hotspot volcano kilauea than in the etna plume probably non hotspot in character it may be a useful indicator of the tapping of deep mantle zones or could aid in the interpretation of reports of pt group metals in exhalations from hot spot volcanoes indium in old glacial ice strata could help assess magnitude and variability of exhalations from hotspot volcanoes in past time strong melt vapor fractionation of the alkali and alkaline earth metals may only be observed in plumes during quiescent degassing of volcanoes when large amounts of ash or spatter undifferentiated lava enter the plume its alkali and alkaline earth metal composition may approach that of the melt ratios among the chalcophile metals may not be much changed by addition of ash because their concentrations in melt are so small and masses of them in any plume may remain dominated by transfer across the melt vapor interface radon daughter nuclides give information about state of volcanic activity at time of sampling the precisely known origins ultratrace detectability decay systematics and wide variations in volatility of these species provide information about residence times degassing and travel histories and identities of melt bodies in volcanic systems

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

bedforms of the canadian eastern seaboard a comparison with global occurrences this paper presents a compilation of sedimentary bedforms identified from acoustic and seismic records collected over the southeastern canadian continental shelf in order to make the compilation it was found necessary to firstly review and synthesise the various terminologies used to describe the bedforms found and thereafter to relate the subsequent terminology to any diagnostic generic characteristic identifiable from the records sand waves are considered to be those forms that are composite in nature and are generated solely by the action of superimposed megaripples these latter features are identifiable adopting the classification of dalrymple et al 1978 which proves adequate for the acoustic differentiation of 2 d and 3 d types though we observed a greater coherence in bedform spacing of the 2 d types than reported hitherto sand ridges were adequately defined and recognised using the description of swift et al 1978 with respect to storm generated ridges and that of off 1963 and others with respect to tidal current ridges such ridges appear not to be uniquely described by ratios of their metrics the bedforms on the southeastern canadian continental shelf are abundant and wide spread virtually all types of bedforms recognisable on the u s shelf are present to the north the majority of these bedforms appear to be storm generated and are considered intermittently active many of the sand waves s s have no measureable relief though retaining their distinctive spatial geometry both active and moribund sand ridges were found of these ridges both tidal and storm generated types were identified the storm generated ridges were further broken down into shoreface connected ridges and offshore ridges a metrical analysis of the various bedforms show that a differentiation into stable bed phases can be made using height length ratios provided the bedforms are active and fully developed there is some overlap between megaripples and small sand waves and indeed between 2 d and 3 d megaripples yet the distinction is good between sand waves and sand ridges even moribund types sand ribbons in general can be confused with moribund sand waves and megaripples a detailed morphological examination is required to distinguish each feature data from sand ridges of the eastern canadian shelf combined with data from similar features found globally shows that ridge heights tend to cluster into three distinctive modes these modes are at heights of 7 13 and 27 m the first mode is correlated with storm generated ridges the second with tidal current ridges and the third possibly with submerged barrier islands

atmospheric regime of dust and salt through 75 000 years of taylor dome ice core refinement by measurement of major minor and trace metal suites measurement of absolute and relative amounts of dust and salt deposited in the polar ice record is central to several fields of study including nutrient delivery atmospheric deposition of trace elements past wind strengths dust provenance and other aspects of climate and geochemical history we present a method intended to give a more accurate picture than has been possible before of the total amounts and relative proportions of the dust and salt deposited by the atmosphere into polar ice it also permits us to distinguish different compositional types of dust in the ice the method is based on precise measurement of a suite of several metals whose proportions contrast strongly between dust and salt and vary substantially between dust types we apply the method to a small suite of ice samples from the taylor dome core in coastal west antarctica in full glacial times when total impurities were high and dust dominated over salt wind strength in the west antarctic region was apparently high and extensive sea ice cover prevented incorporation of salt into the atmospheric load at the termination of the glacial period increased salt in the dust salt mixture indicates that sea ice diminished but wind strength continued high and unchanged dust composition indicates unchanged source areas at about 10 000 11 000 y b p sea ice cover appears to have briefly returned to glacial conditions but wind conditions remained in the milder postglacial condition soon after sea ice retreated and an abrupt change in dust composition indicates changed source materials or terranes if extended by analysis of more samples from more sites such information on salt and dust could provide firm constraints on past wind strengths extent of sea ice cover deposition fluxes of salt and dust and changing continental source areas of dust for both polar regions of the earth

anthropogenic lead isotopes in antarctica we report the first measurements of pb isotopes in antarctic snow which show that even recent snow containing 2 3 pg g is highly polluted with anthropogenic pb this follows from a comparison of isotope abundances of pb in surface snow and terrestrial dust extracted from ancient antarctic ice dome c depth 308 m approximate age 7 500 a bp the latter being distinctly more radiogenic this result is independent of geochemical arguments based on measurements of al na and so 4 south america is suggested as a likely source of this anthropogenic pb the presence of significantly less radiogenic pb in the snow adjacent to two antarctic base stations indicates that there is contamination from station emissions although emission from australia is an alternative explanation for a site 33 km from dumont d urville

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

stratigraphic analysis of a sediment pond within the new england mud patch new constraints from high resolution chirp acoustic reflection data abstract the new england mud patch nemp is an anomaly on the atlantic coast of north america this 13 000 km2 area located south of cape cod between the 60 m and 160 m isobaths is a region of active fine grained deposition on a shelf that is predominantly non depositional or erosional prior studies theorized that nemp sediments are derived from fines winnowed from georges bank transported westward by coastal currents and then settled in more quiescent conditions a chirp seismic reflection 2015 and coring 2016 survey of part of the nemp was conducted in support of a planned acoustic experiment for the office of naval research the survey focused on a 30 km e w by 8 km n s region between the 70 m and 85 m isobaths encompassing a sediment pond 12 m thick the dense 250 m survey lines allow a pseudo 3d stratigraphic interpretation the sediment pond occupies an embayment eroded into pre lgm substrate sediments perhaps by glacial outwash marine sands beneath the mud are organized into oblique sand ridge morphology the sense of obliquity morphologic asymmetry and internal dipping reflectors indicate that the sand ridges formed under east directed transport however as evidenced by westward prograding depocenters and onlap nemp deposition occurred under west directed transport consistent with modern shelf conditions the onset of fine grained deposition was therefore contemporaneous with a significant shift in the hydrologic regime muds deposited immediately above the sand ridges include a significant sand component whose modal grain size is identical to that of the sand ridges this admixture may indicate that during the early stages of mud deposition the tops of the sand ridges remained unburied and exposed to reworking episodic storm driven transport of sand to the muddy deposits may account for some of the sand component of nemp sediments

changes in heavy metals in antarctic snow from coats land since the mid 19th to the late 20th century v cr mn cu zn co ag cd ba pb bi and u have been measured in a series of dated snow samples covering the period from 1834 to 1990 collected at remote low accumulation sites in coats land antarctica they were determined by ultrasensitive inductively coupled sector field mass spectrometry in ultraclean conditions concentrations are found to be extremely low down to 3 10 15 g g for most metals then confirming the high purity of antarctic snow the results show contrasting time trends for the different metals for mn co ba and possibly v and cd no clear time trends are observed for cr cu zn ag pb bi and u on the other hand pronounced enhancements are observed during the recent decades they are attributed to emissions of heavy metals to the atmosphere from human activities in southern america southern africa and australia especially non ferrous metal mining and smelting in chile peru zaire zambia and australia it shows that atmospheric pollution for heavy metals in the remote antarctic continent is not limited to pb and cu as previously thought but also affects several other metals it is a further indication that atmospheric pollution for heavy metals is really global

synchronous volcanic eruptions and abrupt climate change 17 7 ka plausibly linked by stratospheric ozone depletion glacial state greenhouse gas concentrations and southern hemisphere climate conditions persisted until 17 7 ka when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the southern hemisphere with many changes ascribed to a sudden poleward shift in the southern hemisphere westerlies and subsequent climate impacts we used high resolution chemical measurements in the west antarctic ice sheet divide byrd and other ice cores to document a unique 192 y series of halogen rich volcanic eruptions exactly at the start of accelerated deglaciation with tephra identifying the nearby mount takahe volcano as the source extensive fallout from these massive eruptions has been found 2 800 km from mount takahe sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface uv radiation indicate that the eruptions led to stratospheric ozone depletion rather than a highly improbable coincidence circulation and climate changes extending from the antarctic peninsula to the subtropics similar to those associated with modern stratospheric ozone depletion over antarctica plausibly link the mount takahe eruptions to the onset of accelerated southern hemisphere deglaciation 17 7 ka

natural concentrations of lead in ancient arctic and antarctic ice concentrations of pb and k were determined in a series of veneer layers chiseled in sequence from the outside toward the center of each of the five 1500 5500yr old ice core sections that had been drilled in greenland and antarctic ice they were analogs of very old ice samples analyzed earlier by herronet al 1977 and craginet al 1975 who reported high concentrations of pb in them lead contamination existing at exterior concentrations of about 10 6 ng kg ice had intruded to the centers of the cores establishing interior values of at least 1 4 ng kg ice in three electromechanically drilled camp century core sections taken from fluid filled drill holes corresponding pb concentration changes were 3 10 4 ng kg ice to 1 2 ng kg ice in two thermally drilled new byrd station core sections taken from non fluid filled drill holes contamination made the lowest center concentrations serve only as upper limits to the original concentrations of pb in the ice potassium concentrations decreased from exterior values of about 5 10 5 ng kg ice to an interior value of 2 10 3 ng kg ice in the camp century core sections and from 8 10 4 ng kg ice to 9 10 2 ng kg ice in new byrd station core sections potassium contamination effects were not large within the central portions of the cores these data verify earlier findings by murozumiet al 1969 and extend to a broader geographical significance the general validity of their observation of a 300 fold increase of pb concentrations in the greenland ice sheet during the past 3000 yr our findings refute claims by herronet al 1977 and craguinet al 1975 that 100 fold excesses of natural pb exist in 800 yr old greenland ice above levels contributed by silicate dusts our new data also show that average pb concentrations of 26 ng pb kg ice claimed by boutron and lorius 1979 to be natural and present for 60 yr in snow strata in antarctica did not exist in old antarctic ice and that pb concentrations have increased at least 10 fold in that ice during the past century virtually all of the present day 300 fold excess of pb above natural levels in greenland ice can be shown to be caused by industrial pb emissions to the atmosphere on the basis of the following factors 1 the historic increase of pb in snow strata coincides with the historic increase of industrial pb production and atmospheric emissions 2 mass inventories of industrial emissions can account for the excess pb in polar snow 3 new quantitative measurements of pb emissions from volcanic plumes by buat menard and arnold 1978 pattersonet al 1981 and buat menardet al 1981 and from sea spray by ng and patterson 1981 and settle and patterson 1981 show that these natural sources cannot account for 99 of the excess pb above contributions by silicate dusts observed today in the atmosphere and 4 the historic increase of pb in snow strata is paralleled by analogous increases of excess pb shown by isotopic tracers to be industrial in water laid sediments in a remote continental region shirahataet al 1980 it is now known however that snows display about a 10 fold greater excess of industrial pb above crustal silicate concentrations than exists in the air above the snows

temporal variability of cd pb and pb isotope deposition in central greenland snow 1 we present a decade long 1981 1990 high resolution subseasonal record of pb and cd concentrations and pb isotopic composition in a series of 119 snow samples from a 6 m snow pit at summit greenland both metals show order of magnitude seasonal variability with maxima in spring of every year coinciding with sulfate peaks these short term features complicate attempts to quantify secular decadal scale trends associated with anthropogenic source changes e g phasing out of leaded gasoline a small 50 decrease during the decade is estimated for pb but no significant trend is observed for cd mean concentrations for the snow pit pb 216 cd 11 pmol kg 1 are indistinguishable from mean values for nearly continuous samples of the 1 6 m section of a firn core drilled 1 km away suggesting freedom from contamination artifact an evaluation of potential sources confirms that pb and cd are dominated by anthropogenic inputs isotopic ratios 206pb 207pb and 208pb 207pb determined on a subset of snow pit samples of varying ages within the decade indicate that springtime pb concentration maxima are consistent with a mixture of eastern european former soviet union and western european sources while seasonal pb minima especially from the early portion of the decade plot along a different mixing line suggesting a mixture of u s and european sources the combination of pb concentration and isotopic composition are consistent with an estimated decrease in u s pb contributions of about twofold over the decade which predicts a decadal concentration decrease in the snow of 30 however the secular trends in both concentration and isotopes are barely detectable against seasonal and interannual variability the evidence for seasonally distinct source regions may be useful for interpretation of high resolution records of other chemical species in greenland snow and ice analyses of two deep core sections dated at 1699 1700 and 1780 1788 compared to the snow pit data indicate that both pb and cd deposition in central greenland roughly doubled during the eighteenth century then doubled again by the 1980s

late quaternary loess in northeastern colorado part ii pb isotopic evidence for the variability of loess sources a new application of the pb isotopic tracer technique has been used to determine the relative importance of different silt sources for late wisconsin loess in the central great plains of eastern colorado samples of the peoria loess collected throughout the study area contain k feldspar derived from two isotopically and genetically distinct sources 1 glaciogenic material from early and middle proterozoic crystalline rocks of the colorado province and 2 volcaniclastic material from the tertiary white river group exposed on the northern great plains pb isotopic compositions of k feldspar in loess from two dated vertical sections at beecher island and last chance colorado vary systematically implying climatic control of source availability we propose a model whereby relatively cold conditions promoted the advance of front range valley glaciers discharging relatively little glaciogenic silt but strong winds caused eolian erosion of white river group silt due to a decrease in vegetation cover during warmer periods valley glaciers receded and discharged abundant glaciogenic silt while surfaces underlain by the white river group were stabilized by vegetation isotopic data from eastern colorado loess sections record two warm cold warm cycles during late wisconsin time between about 21 000 and 11 000 radiocarbon yr b p similar to results from other studies in the united states and greenland

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

rock forming metals and pb in modern alaskan snow metal concentrations in annual and subannual increments of snowpack from the accumulation zone of a south central alaska glacier indicate that the deposition of pb with and upon snow is decoupled from that of rock dusts rock dusts accumulate apparently as dry deposition on the topmost exposed surfaces of snowpacks in spring and summer whereas pb does not pb concentration is elevated throughout the latest one third of an annual snowpack whereas that of rock dusts is not for whole year snowpacks there is a generally sympathetic relationship among concentration of pb concentration of rock dust degree of dominance of rock dusts over ocean solutes and ferromagnesian character of the rock dusts however the fractional abundance of pb in whole year samples may decrease when rock dust masses become large and or when rock dusts dominate most strongly over salts the metal suite chosen to characterize rock dusts and to distinguish them from ocean solutes gives detailed information about rock type of dust source areas and about the nature of the degraded rock products that are taken up transported and deposited by the atmosphere rock dusts are present at concentrations of only about 300 nanograms ng of dust per gram of snow in the alaskan snowpacks concentrations of pb in the alaska snow samples are moderate ranging from 0 1 to 0 3 ng pb g snow this contrasts with larger pb concentrations of 0 4 to 0 9 ng pb g snow in whole year snowpack samples from the sierra nevada california with similar to smaller concentrations from north and south greenland of about 0 04 ng pb g snow or less and about 0 2 ng pb g snow or less respectively and with much smaller concentrations from antarctica now believed to range from a minimum of about 0 001 to a maximum of 0 005 or 0 01 ng pb g snow

the local and global dimensions of metalliferous pollution derived from a reconstruction of an eight thousand year record of copper smelting and mining at a desert mountain frontier in southern jordan abstract this paper establishes an eight thousand year history of anthropogenic metal pollution at one of the oldest most important and longest sustained sites of the extraction and smelting of copper ores in the old world the faynan orefield in jordan which is located between the hyper arid southern desert and the front of the wetter mountains of edom the modern land surface is shown in significant part to be a complex palimpsest of archaeological sites metal pollution of various ages and ore processing deposits quantitative and qualitative observations of the storage and cycling of heavy metals through the local natural and domestic systems have produced a body of information on processes with which the past has been interpreted heavy metal concentrations in semi continuous sedimentary bodies indicate that over the last 1500 years metals were removed by natural processes at a comparatively slow rate given the scale of the original anthropogenic metal burden the proportions of lead with respect to copper have increased as the overall metal burden has been lowered distinctive anthropogenic metal pollution signatures have been detected in ash and charcoal rich deposits that were discarded onto the banks of a perennial stream in the late neolithic at present the nature of the human activities that might have produced these pollution signatures is unknown substantial metal pollution from industrial scale smelting activity was present from the early bronze age the intensity of heavy metal pollution produced in classical times locally exceeded that recorded at major european copper smelting centres in the nineteenth century a d the pollution evidence indicates that intensive copper smelting at the immediate area took place until approximately the end of the byzantine period with the exception of one further minor episode of smelting radiocarbon dated to cal bp 530 330 an observed partial but perhaps significant parallelism is also noted between this local record and the records of the metal burdens of the northern hemisphere determined at mire or ice sheet sites at high altitudes or high latitudes the paper discusses the extent to which this parallelism might be a geochemical indicator of the actual existence of economic systems of a geographical scope and scale to have both exercised substantial pull upon the resources of such isolated and difficult locations at the wadi faynan and to have generated sufficient overall metal pollution to have materially altered the chemistry of the global atmosphere the comparative absence of quantitative information upon the nature spatial scale and impacts of human industrial and natural processes affecting metal pollution in other metal rich arid lands provides a significant impediment to such approaches that seek to research locally and think globally

relative levels of natural and anthropogenic lead in recent antarctic snow concentrations of lead have been measured by ultraclean isotope dilution mass spectrometry in large blocks of surface snow collected along a 433 km coast interior axis in east antarctica and near the geographic south pole slight contamination existed on the outside of the blocks but concentration profiles from their exteriors to their interiors indicate that lead concentrations in the innermost parts of the blocks do represent the original concentrations in present day antarctic snow geographical variations of lead concentrations appear to be mainly due to local emissions from dumont d urville and amundsen scott stations the globally significant lead concentration in present day antarctic snow is found to be about 2 pg pb g the corresponding value in antarctic air is estimated to be about 7 pg pb m 3 stp which is approximately fivefold larger than total natural lead contributed by soil dusts volcanoes and sea salts a tentative temporal curve of globally significant lead concentrations in antarctic ice and snow for the last 13 000 years is given it shows concentrations of about 0 4 pg pb g throughout most of the holocene with recent fivefold increases to about 2 pg pb g today the general picture is then that four fifths of total lead in the antarctic troposphere today is anthropogenic

the impact of ionic strength on the proton reactivity of clay minerals abstract the reactivity of clay mineral surfaces exerts a fundamental control on elemental cycling in environmental systems however the effect of solution ionic strength is on their reactivity is poorly understood here we quantified the effect of changes in is on clay mineral reactivity through the application of surface complexation modeling scm based on acid base titration data for three different clay minerals kaolinite illite and montmorillonite the results demonstrate that the acidity constants ka values for proton interactions on the clay surface vary linearly as a logarithmic function of solution is and that proton binding ability is inversely related to solution is two possible explanations for the observed relationship are proposed 1 solution electrolytes e g na competitively bind to clay surface sites relative to protons and 2 that the surface electrostatic field is attenuated by solution electrolytes we conclude that the impact of increasing solution is on clay surface reactivity is the result of a weakening negative surface electric field that impacts the surface potential this mechanism ultimately leads to different adsorption behavior for cations and anions under changing is conditions the empirical relationship between k values and is provided here can be applied to predict clay surface reactivity under varied environmental is conditions and has specific implications for trace metal behavior in environments such as estuaries where changes in is can be significant

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

trace elements in vostok antarctic ice during the last four climatic cycles li v cr mn co as rb sr ba bi and u were determined by inductively coupled plasma sector field mass spectrometry icp sfms in various sections of the 3623 m vostok deep antarctic ice core dated from 4600 to 410 000 years bp which corresponds to the last four climatic cycles back to isotopic stage 11 3 concentrations of all elements were found to be highly variable with low values during interglacial periods and warm interstadials and much higher values during the coldest periods of the last four ice ages crustal enrichment factors suggest various sources for the different elements rock and soil dust is the dominant source of v mn rb ba and u whatever the period and of li cr co sr and as during cold periods sea salt aerosol together with aeolian dust also contributes significantly to sr whereas volcanic emissions could provide a significant input for as and bi especially during warm periods