zn sr isotope records of the ediacaran doushantuo formation in south china diagenesis assessment and implications abstract recent studies show that zinc isotopes could provide valuable clues to environmental change and biogeochemical cycle of the past oceans this study reports a modified procedure for leaching the carbonate fractions in sedimentary rocks a thorough evaluation of diagenetic effects and systematic variations of zn and sr isotope ratios in lower part of the ediacaran stratigraphic unit deposited in the aftermath of the marinoan glaciation in south china the influence of post depositional diagenesis on zn isotope compositions of the studied samples is assessed by comparing 66zn to other geochemical indexes 87sr 86sr 13c 18o and mn sr ratios in the five studied cap carbonate sections member i of the doushantuo formation dolostones from four sections have 66zn values positively correlated with 18o values and negatively correlated with 87sr 86sr ratios 0 7081 0 7204 these correlations suggest that these cap dolostone samples have been modified by post depositional diagenesis the light 66zn value 0 02 suggests that initial zn isotope ratios of cap dolostones could have been reset by hydrothermal fluids with relatively high zn concentration and low 66zn values by contrast carbonates from member ii of the doushantuo formation above cap dolostones are relatively pristine based on their low 87sr 86sr ratios 0 7079 0 7086 being indistinct from the proposed early ediacaran seawater 87sr 86sr values chemical and isotopic variations in these samples are interpreted to reflect primary signals that record paleo environmental changes of the early ediacaran ocean a rapid increase of 66zn from 0 3 to 1 1 occurs in the middle part of member ii accompanying by relatively invariant 87sr 86sr ratios that imply insignificant changes in input from continental weathering considering the limited change in atmospheric oxygen during this period the rapid 66zn raise indicates an increase in buried organic matters which is consistent with the coupled positive shift of 13ccarb as well as the fossil records found in the same strata these results provide insights into zn cycling in the post marinoan oceans and facilitate the application of zn isotopes in carbonates as a proxy for the fate of marine organic matter

extraction of pb and zn from crude oil for high precision isotopic analysis by mc icp ms abstract radiogenic and stable isotopic tracing of crude oils has not so far been undertaken largely because of the difficulties of dealing with the low trace element contents of oil samples for high precision isotopic measurements here we present a novel analytical protocol that allows for precise and accurate determination of radiogenic pb and stable zn isotopic compositions on as little as 5 ml of crude oil from a variety of geographically geologically and environmentally diverse settings the 41 pb and zn samples measured to validate the new protocol were separated from their respective crude oils by liquid liquid extraction into an aqueous phase readily handled in a clean laboratory for subsequent purification of pb and zn by standard anion exchange column chromatography lead and zn isotopic compositions on the same 5 ml sample of crude oil were obtained by mc icp ms on 95 of the total extracted pb and zn while elemental concentrations were measured by q icp ms on 5 aliquots to the best of our knowledge the present technique is the first efficient procedure for pb and zn isotopic analysis of crude oil which owing to the elimination of the organic fraction at the liquid liquid extraction stage does not require any specialized equipment neither for the wet chemistry nor for the mass spectrometry the high extraction yields of the method and the low detection limits and high sensitivity of respectively q icp ms and mc icp ms permit analysis of very small sample quantities down to 2 ng and 100 ng respectively of pb and zn for isotopic analysis and a few hundred pg for abundance measurements reproducibility is on a par with routine state of the art pb and zn isotopic measurements of other types of geological materials while total procedural blanks for both elements are negligible relative to the amounts of pb and zn typically separated from crude oil

deglacial warming of the northeastern atlantic ocean correlation with the paleoclimatic evolution of the european continent abstract isotopic micropaleontologic and pollen analyses of deep sea cores from the bay of biscay and the northeastern atlantic ocean show that the deglacial warming of this oceanic area was closely correlated with the paleoclimatic evolution of the adjacent european continent temperatures were at least as warm as those of today in the bay of biscay between 13 300 and 11 000 b p coinciding with the combined bolling allerod warm continental events a major spread of polar water occurred between 11 000 and 10 000 b p during this event which coincides with the younger dryas continental cold event marine temperatures were almost as low as those of the last glacial maximum the final deglacial warming of the norteastern atlatntic ocean occurred during the following 3000 yr

rapid changes in the oceanic fronts in the norwegian sea during the last deglaciation implications for the younger dryas cooling event abstract two high resolution cores enam93 21 north of the faeroe islands and troll 89 03 off southwest norway from the se norwegian sea have been investigated for downcore variations in planktic foraminifera ird content and oxygen isotopes in a period from 15 to 9 ka the results exhibit frequent and large amplitude changes in sea surface temperature during the last deglaciation a sudden and profound increase in sst at 12 8 ka is followed by three abrupt and short lived cooling events terminated by the younger dryas cooling the presence of strong temperature gradients in the norwegian sea region during the bolling younger dryas period have implications for the heat flux towards the north a possible time lag may exist between enam93 21 and troll 89 03 at the beginning of the younger dryas cooling these findings indicate that polar waters migrated eastwards at the beginning of the younger dryas period

last interglacial and holocene climatic development in the norwegian sea region ocean front movements and ice core data planktonic foraminiferal evidence suggests that the ocean front systems between polar and atlantic surface waters in the norwegian sea generally were located closer to greenland during oxygen isotope substage 5e than in the holocene during both these periods oscillations have occurred in the position of the fronts in the western norwegian sea region the substage 5e influence of warm atlantic waters was interrupted by a return to polar conditions these findings support both ice core data and evidence from europe that the last interglacial was a period of rapid climatic shifts

warm atlantic surface water inflow to the nordic seas 34 10 calibrated ka b p a number of short lasting warm periods interstadials interrupted the otherwise cold climate of the last glacial period these events are supposedly linked to the inflow of the warm atlantic surface water to the nordic seas however previous investigations of planktonic foraminifera from the nordic seas have not been able to resolve any significant difference between the interstadials and intervening cold stadials as the faunas are continuously dominated by the polar species neogloboquadrina pachyderma s here we examine the planktonic foraminifera assemblages from a high resolution core link17 taken at 1500 m water depth off northern scotland below the warmest part of the inflowing atlantic water the core comprises the time period 34 10 calibrated ka b p the coldest period of the last glaciation and the deglaciation the results reveal a hitherto unknown faunistic variability indicating significant fluctuations in both surface water inflow and in summer sea surface temperatures during the interstadials relatively warm atlantic surface water 4 7 c flowed north into the eastern norwegian sea during the stadials and heinrich events the surface inflow stopped and the temperatures in the study area dropped to 2 c the last glacial maximum was nearly as warm as the interstadials but the inflow was much more unstable the data reveal two previously unrecognized warming events each lasting more than 1600 years and preceding heinrich events he3 and he2 respectively by destabilizing the ice sheets on the shelves the warmings may have played a crucial role for the development of heinrich events he2 and he3

a role for scavenging in the marine biogeochemical cycling of zinc and zinc isotopes zinc zn and cadmium cd are important biologically active trace metals in the ocean to date the marine distributions of these elements have been understood primarily in terms of biological assimilation by growing phytoplankton and regeneration of sinking biological material initial studies of zn and cd concentrations and stable isotope ratios 66zn and 114cd have therefore focused on their use as simple tracers of assimilation and regeneration in the oceans however these two processes are insufficient to explain new data on the marine distribution of zn and 66zn here using the first high resolution paired marine depth profiles of zn cd 66zn and 114cd we suggest that scavenging of zn onto organic matter plays a major yet largely unconsidered role in the marine cycling of zn this hypothesis is supported by culture experiments which show that zn released from degrading phytoplankton is rapidly scavenged back onto organic matter and that adsorbed zn is isotopically heavier than the dissolved phase by 0 58 in contrast very little cd or phosphate was scavenged and cd isotopes were not significantly fractionated during degradation our hypothesis is further supported by one dimensional modeling which reproduces observed marine 66zn profiles with 1 of zn adsorbed to particles understanding how zn cycling in the oceans is a balance between assimilation scavenging and regeneration is necessary in order to investigate 66zn as a tracer of marine productivity we anticipate that paired analyses of 66zn and 114cd will prove to be valuable new tools in constraining patterns of global primary productivity providing key information for the marine carbon cycle during periods of past and present global climate change

zn isotopic evolution in early ediacaran ocean a global signature abstract the zn isotope composition of sedimentary archives reveals key biosphere lithosphere interactions throughout geologic history a recent zn isotope study of ediacaran cap carbonates from south australia revealed that the local isotopic profile reflects global changes in oceanic chemistry to examine this critical assumption this study investigates a high resolution zinc isotope profile of marinoan post glacial cap carbonates from the yangtze platform south china stratigraphic variations in zn isotope data from this study are similar to previously reported sections in south australia and south china the remarkable isotopic similarity between the two sections that were deposited on distant geographically separated continental blocks demonstrates that the zn isotopic variations reflect changing global signatures of the early ediacaran ocean this study highlights the value of zn isotopes in sediments as a global proxy for paleoceanographic studies we interpret the systematic stratigraphic changes in the zn isotope composition of the studied post glacial marinoan carbonates as a global oceanic trend controlled mainly by varying inputs and outputs of zn to the ocean decreasing 66zn values in the lowermost part of the section are attributed to the global precipitation of carbonate enriched in the heavier zn isotope a positive shift in the middle part of the section is explained by the non quantitative removal of isotopically lighter zn by sulfide minerals lower 66zn values in the uppermost part likely reflect the changing contributions of continental weathering and sulfide precipitation our data suggest that non quantitative removal of zn by sulfides is a previously unrecognized sink for zinc in the oceans

a 120 yr record of widespread contamination from mining of the iberian pyrite belt a metal enriched seawater plume entering the western mediterranean sea through the strait of gibraltar originates 300 km to the west in the rio tinto estuary of southwestern spain mining of rio tinto ore one of the largest metal rich sulfide deposits in the world started well before roman times contemporary rio tinto waters draining the region are highly acidic ph 2 5 with dissolved cadmium zinc and copper concentrations 10 5 10 6 times higher than in uncontaminated surface water of the gulf of cadiz two dated sediment cores from the spanish continental shelf show that metal inputs to the region increased with the onset of intensive mining activities during the second half of the 19th century although the impact of mining may have decreased over the past few decades the tinto river and estuary remain highly contaminated

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

the cycling of iron zinc and cadmium in the north east pacific ocean insights from stable isotopes abstract dissolved stable isotope ratios of the transition metals provide useful information both for understanding the cycling of these bioactive trace elements through the oceans and tracing their marine sources and sinks here we present seawater dissolved fe zn and cd concentration and stable isotope ratio 56fe 66zn and 114cd profiles from two stations in the pacific ocean the safe station 30 n 140 w in the subtropical north east pacific from the geotraces ic2 cruise and the marginal san pedro basin 33 8 n 118 4 w within the south california bight these data represent to our knowledge the first full water column profiles for 66zn and 56fe from the open ocean north pacific and the first observations of dissolved 66zn and 114cd in a low oxygen marginal basin at the safe station 56fe is isotopically lighter throughout the water column 0 6 to 0 1 relative to irrm 014 compared to the north atlantic suggesting significant differences in fe sources or fe cycling between these two ocean basins a broad minimum in 56fe associated with the north pacific oxygen minimum zone omz

total dissolved zinc in the upper water column of the subarctic north east pacific abstract total dissolved zn concentrations are reported for winter and summer along the e w line p transect and for summer along s n line z transect extending from ocean station papa osp 50 n 145 w to the respective shelf waters surface water 10 m concentrations ranged from 0 04 nm in the open ocean to 0 9 nm at the canadian shelf station a clear gradient is evident with dissolved zn concentrations decreasing with increasing distance from shore along the e w transect in both summer and winter no consistent trend was observed along the s n transect low concentrations of zn 0 05 0 07 nm were observed in near surface water at osp in winter the vertical distribution of dissolved zn is oceanographically consistent showing a silicon like vertical profile concentrations of silicic acid and dissolved zn at depth are higher than those at equivalent depths in the atlantic as expected from deep water circulation patterns and build up in concentration of these elements dissolved zn si ratios in the upper 200 m indicate a trend of decreasing with distance from shore which infers a decoupling between dissolved zn and silicic acid in the upper ocean we hypothesise that the silicon like profile of dissolved zn is a result of recycling from relatively biologically resistant organic particulate phases that leads to profiles very similar to those of dissolved silicon other than at two stations where there is very high primary production there is no apparent horizontal relationship between total dissolved zn and chlorophyll a or production

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

the zn abundance and isotopic composition of diatom frustules a proxy for zn availability in ocean surface seawater we have developed cleaning methods for extracting diatomopal from bulk marine sediment samples for measurement of both zinc zn abundance and isotope composition this cleaning technique was then applied to a set of holocene core top samples from the southern ocean the measured 66zn reported relative to the jmclyon standard and zn si ratios from the southern ocean diatomopal samples range from 0 7 to 1 5 and from 14 to 0 9 mol mol respectively the zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters in common with previous work we interpret the systematic changes in the zn si ratio to be linked to the variability in the concentrations of bioavailable zn in the ambient surface seawater where the diatom opal is formed this variability is likely to be primarily controlled by the degree to which zn is taken up into phytoplankton biomass the observed systematic pattern in the 66zn compositions of the diatomopal core top samples is similarly likely to reflect changes in the 66zn composition of the ambient zn in the surface waters above the core top sites which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material thus the systematic relationship between zn isotopes and abundance observed in the core top diatomopal samples suggests a potential tool for investigating the biogeochemical cycling of zn in the past surface ocean for down core diatomopal material in this respect it may be possible to test hypotheses that attribute variations in atmospheric co2 on glacial interglacial timescales to the degree to which trace metals limited primary productivity in hnlc zones

comparison between radiocarbon ages obtained on coexisting planktonic foraminifera as a test of the reliability of paleocean ventilation rates reconstructed from radiocarbon age differences between planktonic and benthic foraminifera measurements have been made on coexisting species of planktonic foraminifera while ideally no differences should exist we do find them in this paper we discuss the possible causes for these differences and attempt to evaluate their impact on the interpretation of benthic planktonic age differences

biogeochemical cycling of dissolved zinc along the geotraces south atlantic transect ga10 at 40 s the biogeochemical cycle of zinc zn in the south atlantic at 40 s was investigated as part of the uk geotraces program to date there is little understanding of the supply of zn an essential requirement for phytoplankton growth to this highly productive region vertical zn profiles displayed nutrient like distributions with distinct gradients associated with the water masses present surface zn concentrations are among the lowest reported for the world s oceans 2 0 97 n 460 our results suggest that the use of a global zn si relationship would lead to an underestimation of dissolved zn in deeper waters of the south atlantic by utilizing si and a new tracer zn our data indicate that the preferential removal of zn in the southern ocean prevented a direct return path for dissolved zn to the surface waters of the south atlantic at 40 s and potentially the thermocline waters of the south atlantic subtropical gyre the importance of zn for phytoplankton growth was evaluated using the zn soluble reactive phosphorus srp relationship we hypothesize that the low zn concentrations in the south atlantic may select for phytoplankton cells with a lower zn requirement in addition a much deeper kink at 500m in the zn srp ratio was observed compared to other oceanic regions key points dissolved zinc biogeochemical cycle investigated in the south atlantic ocean 2014 american geophysical union all rights reserved

biogeochemical cycling of cadmium isotopes along a high resolution section through the north atlantic ocean abstract cadmium cd is a bioactive trace element in the oceans with a nutrient like distribution that closely matches dissolved phosphate seawater dissolved stable cd isotope ratios 114cd are a relatively new parameter which show much promise for furthering our understanding of the biogeochemical cycling of cd in the oceans here we present a high resolution paired section of dissolved cd concentrations and dissolved 114cd from 21 open ocean stations along the us geotraces ga03 transect through the north atlantic ocean dissolved cd concentrations along the section are strongly influenced by water mass distribution and the cycling of cd the highest dissolved cd concentrations 400 540 pmol kg 1 are associated with antarctic sourced water masses whilst biological uptake in the surface ocean results in a strong vertical gradient in dissolved cd towards the surface reaching as low as 0 03 pmol kg 1 in western surface waters dissolved 114cd is also characterized by a vertical gradient from 0 2 in the deep ocean to 2 to 5 in the cd depleted surface ocean relative to nist srm 3108 this variability in 114cd can be ascribed to mixing of antarctic and north atlantic water masses together with fractionation due to in situ biological uptake of light cd in the very surface ocean subtle deviations from this overall pattern of dissolved cd concentration and dissolved 114cd are observed within low oxygen waters off north africa where a dissolved cd deficit relative to phosphate is associated with higher dissolved 114cd values together with elevated particulate cd and ba this suggests that cd sulfide precipitation is occurring within the water column of the north atlantic constituting a potentially important sink for isotopically light cd additionally the first measurements of dissolved 114cd within a hydrothermal plume at the mid atlantic ridge show that cd is scavenged from the dissolved phase leaving the remnant dissolved cd isotopically heavier constraining the significance of these marine sinks for dissolved cd is important not only for our understanding of the marine biogeochemical cycling of cd in the modern oceans but also for the successful application of the microfossil cd ca proxy and the development of 114cd as a tracer for past ocean biogeochemical cycling

zinc and strontium isotope evidence for climate cooling and constraints on the frasnian famennian 372 ma mass extinction abstract the frasnian famennian f f mass extinction is one of the big five biotic crises during the phanerozoic whereas the cause of this catastrophic event still remains debated here we present for the first time high resolution zn and sr isotope data obtained by a sequential leaching procedure for carbonate rocks across the f f boundary from the fuhe section in south china both 66zn and 87sr 86sr values rapidly increase in the lower and upper kellwasser horizons and palmatolepis delicatula platys to p minuta minuta conodont zones and the positive isotope shifts are exactly located in the same horizons characterized by low 13c values equivalent to low atmospheric pco2 level reflecting climate cooling and sea level fall stages the strong temporal coupling of 66zn values raise with elevated 87sr 86sr ratios is most likely to have been caused by input of isotopically heavy zn and radiogenic sr from carbonate dominated weathering and or uptake of isotopically light zn into primary producers during climate cooling climate cooling could cause relative sea level falls resulting in widespread exposure of carbonate platform enhance carbonate influx proportion through differential weathering of carbonate and silicate rocks and cause greater productivity by promoting oceanic thermohaline circulation and enhancing upwelling of bio limiting nutrients all of these processes would have contributed to the positive shifts of 66zn as observed this proposed scenario is in accordance with the fact that the f f mass extinction was almost limited to the shallow water tropical stenothermal faunas whereas the high latitude and deep water faunas were less affected our data support and represent the composite effect of a series of events linked to climate cooling which may have induced this catastrophic event

high resolution alkenone sea surface temperature variability on the north icelandic shelf implications for nordic seas palaeoclimatic development during the holocene the palaeoceanography of the northern icelandic shelf for the holocene period was reconstructed from alkenone indices measured in core jr51 gc35 this contains a continuous record of holocene sedimentation spanning 0 10 2 cal kyr bp with a resolution of 20 yr cm we have identified a general holocene cooling trend that has superimposed millennial scale oscillations of 28c their timing is in close agreement with the timing of glacier advances in northern iceland for the later half of the holocene the alkenone sea surface temperature sst record from jr51 gc35 correlates with proxy data for the strength of nadw formation recorded in cores south of iceland this is interpreted as evidence of a close connection existing between north icelandic sea surface temperatures and the north atlantic meridonal overturning circulation the timing of the millennial scale sst variability in our core off north iceland is found to be out of phase or anti phased with the sst variability of a record in the eastern nordic seas md952011 this suggests that the evolution of holocene climate in the nordic seas was more complex than previously proposed and it is likely to be caused by differential responses of the irminger and norwegian currents and modulated by changes in atmospheric circulation analogous to the north atlantic oscillation

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

zn and cu isotopic variability in the alexandrinka volcanic hosted massive sulphide vhms ore deposit urals russia abstract copper and zn isotope ratios of well characterized samples from three ore facies in the devonian alexandrinka volcanic hosted massive sulphide vhms deposit southern urals were measured using multi collector icp ms mc icp ms and show variations linked to depositional environment and mineralogy the samples analysed derived from a hydrothermal metasomatic vein stockwork b a hydrothermal vent chimney and c reworked clastic sulphides as the deposit has not been significantly deformed or metamorphosed after its formation it represents a pristine example of ancient seafloor mineralization variations in 65 cu where 65 cu 65 cu 63 cu sample 65 cu 63 cu standard 1 1000 and 66 zn where 66 zn 66 zn 64 zn sample 66 zn 64 zn standard 1 1000 of 0 63 and 0 66 respectively are significantly greater than analytical uncertainty for both isotope ratios 0 07 2 very limited isotopic fractionation is observed in primary cu minerals from the stockwork and chimney whereas the zn isotopic composition of the stockwork varies significantly with the mineralogy chalcopyrite bearing samples from the stockwork have lighter 66 zn by 0 4 relative to sphalerite dominated samples which may be due to equilibrium partitioning of isotopically light zn into chalcopyrite during its precipitation 66 zn also showed significant variation in the chimney with an enrichment in heavy isotopes toward the chimney rim of 0 26 which may be caused by changing temperature hence fractionation factor or raleigh distillation post depositional seafloor oxidative dissolution and re precipitation in the clastic sediments possibly coupled with leaching led to systematic negative shifts in cu and zn isotope compositions relative to the primary sulphides copper shows the most pronounced fractionation consistent with the reduction of cu ii to cu i during supergene mineralization however the restricted range in 65 cu is unlike modern sulphides at mid oceanic ridges where a large range of cu isotope of up to 3 has been observed rouxel o fouquet y ludden j n 2004 copper isotope systematics of the lucky strike rainbow and logatchev sea floor hydrothermal fields on the mid atlantic ridge econ geol 99 585 600 zhu x k o nions r k guo y belshaw n s rickard d 2000 determination of natural cu isotope variation by plasma source mass spectrometry implications for use as geochemical tracers chem geol 163 139 149

the zinc isotopic composition of siliceous marine sponges investigating nature s sediment traps article i nfo the zinc zn content and isotopic composition of marine biogenic opal have the potential to yield informa tion about the nutrient availability utilization and export of particulate organic matter from surface to deep waters here we report the first measurements of the zn isotopic composition of deep sea marine sponge skeletal elements spicules collected in the southern ocean our results highlight different zn uptake and isotopic fractionation behavior between the two major siliceous sponge clades hexactinellids and demosponges which is most likely linked to sponge feeding strategy hexactinellid spicule zn isotopic com positions are not fractionated with respect to seawater most likely due to zn transport via the open internal structure of the sponges in contrast demosponge spicules exhibit a wide range of zn isotopic compositions that are related to the opal zn concentration most likely reflecting variable zn isotope compositions in the organic matter particles on which they feed and internal fractionation processes

zinc isotope variations in deep sea carbonates from the eastern equatorial pacific over the last 175 ka the carbonate fraction of sediment core odp 849 leg 138 located in the eastern equatorial pacific mostly consisting of coccoliths was separated and analyzed for its zn isotopic composition the overall variation in zn isotopic composition as determined by multiple collector magnetic sector inductively coupled plasma mass spectrometry was found to be on the order of 1 expressed in 66zn where xzn xzn 64zn sample xzn 64zn standard 1 103 and x 66 67 or 68 over the last 175 ka the analytical precision was 0 04 and the overall reproducibility was usually better than 0 07 the zn isotopic composition signal exhibits several marked peaks and a high frequency variability a periodogram of the 66zn signal showed two periodicities of 35 2 and 21 2 ka we suggest that the latter is caused by the precession of the earth s axis of rotation the periodogram exhibits a minimum at 41 1 ka thus showing that the zn isotopic composition is independent of the obliquity in the eastern equatorial pacific the range of 66zn values observed for the carbonate fraction of odp 849 overlaps with the range observed for fe mn nodules in the world s oceans which suggests that seawater carbonate zn isotope fractionation is weak we therefore assume that most of the zn isotope variability is a result of the selective entrainment of the light isotopes by organic matter in the surface ocean the odp 849 66zn record seems to follow the changes in the insolation cycles changes in the late summer fall equatorial insolation modulate the intensity of the equatorial upwelling hence the mixing between deep and surface waters we propose that during decreased summer fall equatorial insolation when a steep thermocline can develop el nino like conditions the surface waters cannot be replenished by deep waters and become depleted in the lighter zn isotopes by biological activity thus resulting in the progressive increase of the 66zn values of the carbonate shells presumably in equilibrium with surface seawater

zinc and cadmium stable isotopes in the geological record a case study from the post snowball earth nuccaleena cap dolostone abstract zinc and cadmium are important biologically cycled nutrients in the modern ocean recent analytical advances and sampling efforts such as geotraces have led to measurements of the global distribution of zn and cd and their stable isotope ratios 66zn and 114cd providing an understanding of how biological processes cycle these elements and their isotopes in the modern ocean this opens the door to better application of 66zn and 114cd as tracers of biogeochemical processes archived in the geological record here we present new measurements of cd and 114cd on samples from the nuccaleena cap dolostone in south australia which was deposited during deglaciation of the ca 635 ma old marinoan snowball earth our new data are combined with previously measured 66zn data from the same samples the combined record of 114cd and 66zn is used to explore various hypotheses about the sources and sinks of cd and zn in the post marinoan ocean key features of this record are that zn and cd remain relatively similar throughout that 66zn and 114cd change at the same stratigraphic level and in the same direction and that 66zn changes are about four times larger than 114cd changes even though both quantities reflect a similar fractional mass difference we suggest that both zn and cd concentration and isotopic data are consistent with a change in the sink by which zn and cd are removed from the oceans we propose that no isotope fractionation is expressed during removal of zn and cd as sulfides while zn and cd removed with biological material are about 0 6 and 0 2 lighter than deep ocean 66zn and 114cd respectively many previous studies attribute the burial of isotopically light biological zn to preferential assimilation of isotopically lighter zn by phytoplankton in contrast we propose that lighter biological 66zn occurs mostly because isotopically heavy zn was scavenged by organic matter which causes dissolved 66zn in the surface ocean to be lighter than deep ocean 66zn the organic matter originated from primary producers that thrived in the surface ocean during deglaciation for cd whose isotope cycling in the modern ocean is dominated by preferential assimilation of isotopically lighter cd by phytoplankton much less biological fractionation is expressed the combined analyses of 66zn and 114cd provide insight into the biogeochemical processes which occurred after the marinoan snowball earth glaciation and may be a useful new tool to explore the history of life on earth in other geological records as well

pervasive sources of isotopically light zinc in the north atlantic ocean abstract in this study we report seawater dissolved zinc zn concentration and isotope composition 66 zn from the geotraces ga01 geovide section in the north atlantic across the transect three subsets of samples stand out due to their isotopically light signature those close to the reykjanes ridge those close to the sediments and those pervasively in the upper ocean similar to observations at other locations the hydrothermal vent of the reykjanes ridge is responsible for the isotopically light zn composition of the surrounding waters with an estimated source 66 zn of 0 42 this isotopically light zn is then transported over a distance greater than 1000 km from the vent sedimentary inputs are also evident all across the trans atlantic section highlighting a much more pervasive process than previously thought these inputs of isotopically light zn ranging from 0 51 to 0 01 may be caused by diffusion out of zn rich pore waters or by dissolution of sedimentary particles the upper north atlantic is dominated by low 66 zn a feature that has been observed in all zn isotope datasets north of the southern ocean using macronutrient to zn ratios to better understand modifications of preformed signatures exported from the southern ocean we suggest that low upper ocean 66 zn results from addition of isotopically light zn to the upper ocean and not necessarily from removal of heavy zn through scavenging though the precise source of this isotopically light upper ocean zn is not fully resolved it seems possible that it is anthropogenic in origin this view of the controls on upper ocean zn is fundamentally different from those put forward previously

key role of continental margin sediments in the oceanic mass balance of zn and zn isotopes zinc is an essential micronutrient and its concentration and isotopic composition in marine sediments represent promising tracers of the ocean carbon cycle however gaps remain in our understanding of the modern marine cycle of zn including an explanation of the heavy zn isotopic composition of seawater relative to the known inputs and the identity of a required missing sink for light zn isotopes here we present zn isotope data for organic rich and trace metal rich continental margin sediments from the east pacific margins that together provide the first observational evidence for the previously hypothesized burial of light zn in such settings in turn this light zn output flux provides a means to enrich the seawater dissolved pool in heavy isotopes the size and isotopic composition of the margin sink are controlled by the uptake of zn into organic matter in the photic zone and the fixation of this pool probably in the form of zn sulfides in sediments an estimate of its significance to the overall zn oceanic mass balance both in terms of flux and isotopic composition indicates that such settings can fulfill the requirements of the missing zn sink taken together these observations have important implications for the interpretation of zn isotope data for marine sediments in the geologic record

the relationship between zinc its isotopes and the major nutrients in the north east pacific abstract trace metal micronutrients play key roles in photosynthesis by oceanic phytoplankton though they are required in much smaller amounts than the major nutrients p n si their bioavailable forms are also present in the seawater solution at much lower levels relationships between the dissolved chemistry of the nutrient type trace metals their stable isotope variations as well those of the major nutrients have highlighted the importance of biological and physical processes in the southern ocean in controlling their oceanic biogeochemistry however the first order southern ocean processes are overprinted by vertical cycling in other parts of the ocean particularly upwelling regions remote from the southern ocean with the north pacific standing out in particular here we present new zinc zn concentration and isotope as well as major nutrient data for the ne pacific and couple these new data with a compilation of published data from across the region with the objective of better understanding the impact of this important region on oceanic biogeochemical cycles the new zn isotope data for two stations along line p p04 and p26 show a large range in 66 zn in the upper ocean 0 4 up to 1 associated with a very small isotope fractionation but extreme depletion of the dissolved pool during photic zone biological uptake and the regeneration of this cellular zn at very shallow depths 50 m beneath this the two profiles approach the 66 zn value of 0 5 seen throughout the deep ocean by about 500 m the minimum 66 zn resulting from regeneration is associated with very high zn concentrations particularly at the marginal p04 station where diatoms dominate the phytoplankton ecology combining the new data with published zn and major nutrient concentrations from across the north pacific emphasises the role of vertical biological cycling in controlling regional biogeochemistry in the north pacific resulting in the partial overprinting of biogeochemical signatures transported out of the southern ocean by the ocean circulation zinc isotope data document the uptake of this metal into diatoms and the co regeneration of zn with phosphate in the upper water column silica in contrast is regenerated at greater depth resulting in a decoupling of the zn si correlation that is set in the southern ocean and that dominates the atlantic previous work has suggested that the decoupling of zn and si in the subarctic north pacific results from removal of zn and other metals to water column particulate sulphide in our dataset and in the compilation of data documenting relationships between zn and the major nutrients across the north pacific this decoupling is clearly due to the different lengthscales of regeneration for organic matter zn and p and diatom opal si

oceanic and atmospheric variations during the last deglaciation in the fram strait arctic ocean a coupled high resolution organic geochemical and sedimentological study abstract from a high sedimentation rate core obtained from the yermak slope arctic ocean we deduced short term climatic fluctuations of the last deglaciation lasting from 17 000 to 9000 years bp by using a coupled organic geochemical and sedimentological approach we reconstructed near bottom current conditions and assessed their significance in relation with comparable global thermohaline circulation patterns and surface water conditions highest concentrations and fluctuations of specific marine phytoplankton biomarkers were obtained in the bolling allerod when the major deglaciation of the svalbard barents sea ice sheet sbis occurred the marine biomarker record and the sedimentological record are consistent with climate reconstructions obtained from greenland ice cores and thermohaline circulation variations however beginning with the younger dryas yd episode bottom currents decreased during this time period but surface waters remained very productive the atmospheric conditions of the western fram strait reconstructed from biomarker data and thermohaline circulation signals reconstructed from sedimentological data were decoupled in the yd maximum insolation values of solar radiation and fohn like winds enabled open water conditions and increased productivity values in the northern fram strait at least in summer

abundance of zinc isotopes as a marine biogeochemical tracer 1 the zn isotopic compositions of ferromanganese nodules sediment trap samples sediments and organic reference samples have been analyzed by multiple collector inductively coupled plasma mass spectrometry icp ms the range of isotopic variations 1 for 66zn 64zn is significant with respect to the analytical precision 0 04 at the 95 confidence level marine argillaceous sediments show rather constant values consistent with those of continental shales and loess and with the value of a basalt from reunion island we infer that the depletion of the light zn isotopes in marine particles and in ferromanganese nodules presumably equilibrated with seawater results from biological activity in the upper water column the 66zn values of sediment trap samples collected near the upwelling off the coast of mauritania central atlantic show a seasonal isotopic fluctuation consistent with biological pumping during the high productivity period higher values of 66zn in nodules appear to be associated with the amplitude of seasonal variations rather than with the mean values of the biological productivity

zinc and cadmium isotope evidence for redox driven perturbations to global micronutrient cycles during oceanic anoxic event 2 late cretaceous abstract this study uses organic rich sediments from the tarfaya basin morocco to assess the cd and zn isotope response to dramatic global palaeoenvironmental change during the cenomanian turonian interval late cretaceous these organic rich continental margin deposits include an expression of oceanic anoxic event 2 oae 2 94 ma an interval associated with the spread of low oxygen marine environments and widespread burial of organic rich sediments due to placement of the tarfaya basin in a region of upwelling and relatively constant local environmental conditions the stratigraphic variations in 114 cd and 66 zn values largely reflect changes in the seawater isotopic composition of the sub surface proto north atlantic ocean positive shifts of 0 2 0 3 away from background values in 114 cd and 66 zn are observed during the main phase of the positive carbon isotope excursion associated with oae 2 these isotopic shifts are coeval with decreases in cd toc and zn toc ratios and thus imply that drawdown of isotopically light cd and zn from seawater inventories was a result of extensive burial of these metals in organic rich marine sediments globally low 66 zn values during the plenus cold event a cooler episode during oae 2 are similar in timing and magnitude to variations found in the english chalk eastbourne uk and support the inference of a global control on these isotopic excursions the 66 zn values during the plenus cold event are taken to record global oxygenation possibly including the remobilization of isotopically light zn from continental margin sediments a considerably smaller change in 114 cd values for this interval implies that the cd and zn isotope systems can provide information about slightly different environmental processes with global seawater composition with respect to zn also being influenced by the magnitude of oxic removal sinks and isotopically light zn input fluxes from sediments and hydrothermal fluids

determination of molybdenum isotope fractionation by double spike multicollector inductively coupled plasma mass spectrometry 1 molybdenum isotopic compositions are precisely determined by mc icp ms measurements using a mo double spike the double spike is added prior to chemical purification so that laboratory and instrumental mass fractionations are separated from natural mass dependent fractionation fractionation is determined on four mo mass ratios providing an internal consistency check the external standard reproducibility is at 0 06 per mil on the 98mo 95mo ratio 2 standard deviation using a normal microconcentric nebuliser with a cyclonic spray chamber the minimum quantity of mo is 1 g for high precision results a hydrothermal molybdenite shows fractionation of 0 3 per mil on the 98mo 95mo ratio relative to our standard johnson matthey 1000 g ml 0 3 icp standard solution lot 602332b fine grained sediments show fractionation of 0 1 and 0 3 per mil on the 98mo 95mo ratio the observed mo isotope fractionation is small but resolvable with the presented high resolution technique

the biogeochemical cycling of zinc and zinc isotopes in the north atlantic ocean zinc zn is a marine micronutrient with an overall oceanic distribution mirroring the major macronutrients especially silicate seawater zn isotope ratios 66zn are a relatively new oceanographic parameter which may offer insights into the biogeochemical cycling of zn to date the handful of published studies of seawater 66zn show the global deep ocean to be both remarkably homogeneous approximately 0 5 and isotopically heavier than the marine sources of zn 0 1 to 0 3 here we present the first high resolution oceanic section of 66zn from the u s geotraces ga03 north atlantic transect from lisbon to woods hole throughout the surface ocean biological uptake and release of isotopically light zn together with scavenging of heavier zn leads to large variability in 66zn in the ocean below 1000 m 66zn is generally homogeneous 0 50 0 14 2 sd though deviations from 0 5 allow us to identify specific sources of zn the mediterranean outflow is characterized by 66zn of 0 1 to 0 3 while margin sediments are a source of isotopically light zn 0 5 to 0 8 which we attribute to release of nonregenerated biogenic zn mid atlantic ridge hydrothermal vents are also a source of light zn close to 0 5 though zn is not transported far from the vents understanding the biogeochemical cycling of zn in the modern ocean begins to address the imbalance between the light 66zn signature of marine sources and the globally homogeneous deep oceans 66zn of 0 5 on long timescales with overall patterns pointing to sediments as an important sink for isotopically light zn throughout the oceans

the oceanic mass balance of copper and zinc isotopes investigated by analysis of their inputs and outputs to ferromanganese oxide sediments abstract the oceanic biogeochemical cycles of the transition metals have been eliciting considerable attention for some time many of them have isotope systems that are fractionated by key biological and chemical processes so that significant information about such processes may be gleaned from them however for many of these nascent isotopic systems we currently know too little of their modern oceanic mass balance making the application of such systems to the past speculative at best here we investigate the biogeochemical cycling of copper cu and zinc zn isotopes in the ocean we present estimates for the isotopic composition of cu and zn inputs to the oceans based on new data presented here and published data the bulk isotopic composition of dissolved cu and zn in the oceans 65cu 0 9 66zn 0 5 is in both cases heavier than their respective inputs at around 65cu 0 6 and 66zn 0 3 respectively implying a marine process that fractionates them and a resulting isotopically light sedimentary output for the better known molybdenum isotope system this is achieved by sorption to fe mn oxides and this light isotopic composition is recorded in fe mn crusts hence we present isotopic data for cu and zn in three fe mn crusts from the major ocean basins which yield 65cu 0 44 0 23 mean and 2sd and 66zn 1 04 0 21 thus for cu isotopes output to particulate fe mn oxides can explain the heavy isotopic composition of the oceans while for zn it cannot the heavy zn in fe mn crusts and in all other authigenic marine sediments measured so far implies that a missing light sink is still to be located these observations are some of the first to place constraints on the modern oceanic mass balance of cu and zn isotopes

transport of the north atlantic deep western boundary current about 39 n 70 w 2004 2008 abstract begun in spring 2004 a sustained measurement program line w is returning high resolution observations of the north atlantic s deep western boundary current dwbc southeast of new england the study focuses on the cold limb of the atlantic meridional overturning circulation near the boundary between the subpolar and subtropical gyres the field study consists of a 6 element continental slope spanning moored array on a line underlying an altimeter satellite ground track and periodic reoccupations of a full depth hydrographic section along the line extending from the continental shelf towards bermuda here data from the first 4 years of the array may 10 2004 april 9 2008 are analyzed along with 9 realizations of the section the array a mix of moored profiler and discrete fixed depth instrument moorings returned temperature salinity and horizontal velocity data with various temporal and depth resolutions after averaging to filter inertial tidal and other high frequency motions the combined moored data set was binned to the lowest common temporal resolution of 5 days the nominal burst sample interval of the moored profilers and interpolated to 2 dbar vertical resolution temperature salinity dissolved oxygen tracer chemical concentrations and direct velocity data were acquired on the hydrographic cruises the present work focuses on the 4 year mean and time varying meridional transport in 4 layers bounded by neutral density surfaces upper and classical labrador sea waters iceland scotland overflow waters and denmark strait overflow waters the 5 d 4 layer summed meridional transport estimates range between 3 5 and 79 9 sv with a record mean average transport of 25 1 sv and standard deviation of 12 5 sv bias adjustment to account for the finite width of the moored array increases the 4 layer mean transport estimate to 28 7 sv at time scales longer than about 1 month the variations in equatorward dwbc transport appear correlated with meridional position of the gulf stream north wall with stronger transport observed when the stream is displaced south

the isotopic composition of some common forms of anthropogenic zinc abstract anthropogenic sources account for much of the zinc zn in the environment constraining the isotopic composition of anthropogenic zn is therefore essential to understanding the environmental biogeochemical cycling of zn isotopes this study examines the isotopic variability in several different categories of anthropogenic zn pure zn metal and zn dust are the raw materials used in many zn containing products we have measured 66 zn for zn dust purified by thermal distillation electrochemically purified zn metal and us pennies which are made from the most common grade of zn metal special high grade zn in galvanized steel and electroplated hardware was studied because this is a common use of zn and zn in these products may be easily released into the environment through corrosion vitamins were studied because they are more highly purified than typical zn metals and are made from processed chemical compounds such as zn oxide or zn gluconate the isotopic composition of samples measured in this study are as follows reported as 66 zn compared to lyon jmc zn laboratory standards seven samples 9 15 to 0 17 zn metal dust purified by thermal distillation three samples 0 09 to 0 19 zn metal shot purified by electrochemically one sample 0 22 special high grade zn as represented in us pennies six samples 0 14 to 0 31 galvanized steel three samples 0 12 to 0 58 electroplated hardware three samples 0 56 to 0 20 and health products five samples 0 09 to 0 24 based on these results we suggest that the isotopic composition of common anthropogenic zn products ranges from 0 1 to 0 3 all samples studied here had 66 zn values within this range except four laboratory standards all electroplated hardware samples and a single galvanized steel sample the isotopic range for common anthropogenic zn is much smaller than the total 66 zn range found in zn ore field hydrothermal samples demonstrating the effects of zn isotope homogenization during ore processing and purification laboratory standards may have anomalously light 66 zn values because they undergo extra purification steps and zn recovery during these steps is not quantitative electroplated hardware was also isotopically light consistent with previous studies showing that lighter isotopes are electroplated more quickly than heavy isotopes our results suggest that isotopically heavy zn may be incorporated into the waste stream during the electroplating process by defining the range of 66 zn values that is typical for some common zn products and discovering some kinds of products that fall outside this range we will be better able to use zn isotopes to trace different anthropogenic zn sources

impact of diagenetic alteration on brachiopod shell magnesium isotope δ26mg signatures experimental versus field data due to their thermodynamically stable low mg calcite mineralogy the shells of brachiopods are often counted among the most reliable archives of the physicochemical conditions that occurred during the phanerozoic in marine waters consequently traditional and non traditional isotope and elemental proxy data from brachiopod valves have been analyzed in numerous studies and results obtained have been placed in context with ancient seawater properties this paper tests the sensitivity of brachiopod shell magnesium isotope 26mg data to diagenetic alteration we apply a dual approach by i performing hydrothermal alteration experiments using meteoric marine and burial reactive fluids and ii comparing these data to naturally altered ancient brachiopod shells the degree of alteration of individual shells is assessed by a combination of fluorescence and cathodoluminescence microscopy the absence of luminescence might indicate both well preserved shell material but also the secondary enrichment of quenching elements such as iron along diagenetic pathways complementary oxygen isotope data provide insight into the question of open versus closed system behavior of brachiopod shells brachiopod shell magnesium isotope values respond to differential fluid temperature chemistry and experiment durations the patterns observed are complicated by the interplay of kinetic and thermodynamic patterns and the presence of variable amounts of water soluble and water insoluble organic matter within these biominerals generally the range in bulk 26mg from experimentally altered 1 52 and that of bulk samples from ancient diagenetically altered brachiopod valves 1 53 exceed the geochemical variability of 26mgbrachiopod bulk values of most recent specimens 1 26 in the lower and upper range more 26mg enriched 0 8 and more 26mg depleted 0 7 values respectively are found in altered shells in comparison to unaltered ones the data shown here are considered significant for those aiming to reconstruct palaeoenvironmental parameters based on brachiopod archives consequently we propose tentative guidelines for magnesium isotope research applied to ancient carbonates

review of the field data base for longshore sediment transport abstract a literature search was undertaken to collect field data on longshore sediment transport this yielded a large number of data sets 273 points for bulk transport rates from a variety of sites around the world data are especially lacking for transport rates exceeding 0 2 106 m3 year significant wave heights higher than 1 8 m sediment grain sizes coarser than 0 6 mm and beach slopes steeper than 0 06 1 14 a point rating system was devised whereby the quality of the data could be assessed the recording method and the accuracy thereof as well as the representativeness of the data were taken into account it was found that the evaluation was done reasonably objectively and consistently the data were divided into three categories the highest score achieved in the evaluation was only 71 thus reflecting the difficulty of measuring longshore transport accurately it is recommended that longshore transport formulae be calibrated against the data in the higher category 60 and better and then be tested against all the other data this will ensure that the formulae will be tested in as many different conditions and sites as possible without the lower quality data contributing to the calibration constants

zn isotope fractionation during uptake into marine phytoplankton implications for oceanic zinc isotopes abstract the extreme scarcity of zinc zn in the euphotic zone coupled to deep enrichments is consistent with biological uptake at the surface and regeneration at depth in the context of a nutrient type depth profile so clearly shaped by uptake into phytoplankton the growing dataset for zn isotopes presents a challenge these data either show very minor isotope effects associated with extreme depletion or enrichment of the light isotopes in the upper ocean in contrast culturing of eukaryotes in the laboratory suggests that light zn isotopes are preferentially taken up into diatoms and coccoliths implying that zn depletion at the surface should be associated with extremely heavy residual dissolved signals here we present the first zn isotope measurements for cultured marine cyanobacteria and compare these data to those for eukaryotic diatoms grown under identical conditions of the four cyanobacteria cultured belonging to the genera synechococcus and prochlorococcus three preferentially take up light zn into the cell with a variability that is not fundamentally different between pro and eukaryotic phytoplankton we also observe only very subtle differences between zn p and fe p uptake ratios for these three cyanobacteria groups relative to diatoms grown under the same conditions a fourth strain exhibits preferential uptake of heavy zn isotopes and very high zn p ratios overall we speculate that the observed variability among cyanobacteria may be related to the molecular structure of their photosynthetic light harvesting apparatus adapted to significantly different light niches these new and published culture data support the hypothesis that cellular 66zn in culture might largely be controlled by the organic ligands that bind zn in the medium given that the zn binding ligands in the ocean have thermodynamic stability constants that are orders of magnitude smaller than the edta used in culture media the surprisingly subtle zn isotope variability in some parts of the surface ocean may be reconciled with culture data by the lesser near zero preference of these weaker complexes for heavy zn isotopes this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

coupled response of the late glacial climatic shifts of northwest europe reflected in greenland ice cores evidence from the northern north sea the climatic regimes of the land areas adjacent to the north sea are controlled by the influx of atlantic water north of the british isles and into the north sea a high resolution record from the norwegian channel off western norway covering the past 15 ka 14 c shows that prior to the younger dryas there were three periods of sea surface conditions there similar to those of the present interspersed with arctic conditions these changes corresponding to an increase of approx 5 c in summer sea surface temperatures took place on the scale of

zinc stable isotopes in seafloor hydrothermal vent fluids and chimneys many of the heaviest and lightest natural zinc zn isotope ratios have been discovered in hydrothermal ore deposits however the processes responsible for fractionating zn isotopes in hydrothermal systems are poorly understood in order to better assess the total range of zn isotopes in hydrothermal systems and to understand the factors which are responsible for this isotopic fractionation we have measured zn isotopes in seafloor hydrothermal fluids from numerous vents at 9 10 n and 21 n on the east pacific rise epr the tag hydrothermal field on the mid atlantic ridge and in the guaymas basin fluid 66zn values measured at these sites range from 0 00 to 1 04 of the many physical and chemical parameters examined only temperature was found to correlate with fluid 66zn values lower temperature fluids 250 c had both heavier and more variable 66zn values compared to higher temperature fluids from the same hydrothermal fields we suggest that subsurface cooling of hydrothermal fluids leads to precipitation of isotopically light sphalerite zn sulfide and that this process is a primary cause of zn isotope variation in hydrothermal fluids thermodynamic calculations carried out to determine saturation state of sphalerite in the vent fluids support this hypothesis with isotopically heaviest zn found in fluids that were calculated to be saturated with respect to sphalerite we have also measured zn isotopes in chimney sulfides recovered from a high temperature 383 c and a low temperature 203 c vent at 9 10 n on the epr and in both cases found that the 66zn of chimney minerals was lighter or similar to the fluid 66zn the first measurements of zn isotopes in hydrothermal fluids have revealed large variations in hydrothermal fluid 66zn and suggest that subsurface zn sulfide precipitation is a primary factor in causing variations in fluid 66zn by understanding how chemical processes that occur beneath the seafloor affect hydrothermal fluid 66zn zn isotopes may be used as a tracer for studying hydrothermal processes

zinc and nickel isotopes in seawater from the indian sector of the southern ocean the impact of natural iron fertilization versus southern ocean hydrography and biogeochemistry abstract the southern ocean is the site of 20 of global ocean carbon export and the origin of water masses that significantly impact the chemistry of the global ocean much of the southern ocean is a high nutrient low chlorophyll hnlc region iron is the primary limiting nutrient for phytoplankton growth and may also be an important control on the biogeochemistry of the water masses emanating from the southern ocean here we investigate the response of zn and ni and their isotopes to natural fe fertilization from southern ocean islands using samples collected during the keops 2 oct nov 2011 program in the early austral spring near the kerguelen plateau indian sector of the southern ocean zinc and ni concentrations show depth distributions and relationships to major nutrients that are very similar to published data from the atlantic sector of the southern ocean away from island fertilization as in the atlantic sector and other regions outside the southern ocean there is a slight minimum in 66zn at about 100 150 m depth and a slightly heavier value at the surface at the keops 2 sites the light sub surface zn isotopes occur at the depth level where measured chl a has declined to near zero the heaviest zn isotope values in either the atlantic or indian sectors occur in bottom waters are associated with samples that show high dissolved si relative to zn these latter represent possible evidence for a heavy input directly to deep water or from sediment and the zn si 66zn systematics are consistent with a source in diatom opal nickel concentrations show much less variation than those of zn with the most depleted surface value only 15 20 lower than those in upwelled deep water in the southern ocean these small variations in ni concentration are associated with no significant variability in ni isotopes as also previously observed in the atlantic sector overall the key feature of the dataset is the apparent absence of any significant impact of natural fe fertilization on the distribution of zn and ni with the dominant control being the station location relative to the polar front in both the atlantic and indian sectors zinc and ni isotopes are invariant in surface waters whether inside or outside the fertilized zone and whether south or north of the polar front this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

the north atlantic atmosphere sea surface 14c gradient during the younger dryas climatic event abstract we attempt to quantify the 14c difference between the atmosphere and the north atlantic surface during a prominent climatic period of the last deglaciation the younger dryas event yd our working hypothesis is that the north atlantic may have experienced a measurable change in 14c reservoir age due to large changes of the polar front position and variations in the mode and rate of north atlantic deep water nadw production we dated contemporaneous samples of terrestrial plant remains and sea surface carbonates in order to evaluate the past atmosphere sea surface 14c gradient we selected terrestrial vegetal macrofossils and planktonic foraminifera neogloboquadrina pachyderma left coiling mixed with the same volcanic tephra the vedde ash bed which occurred during the yd and which can be recognized in north european lake sediments and north atlantic deep sea sediments based on ams ages from two norwegian sites we obtained about 10 300 yr bp for the atmospheric 14c age of the volcanic eruption foraminifera from four north atlantic deep sea cores selected for their high sedimentation rates 10 cm kyr 1 were dated by ams 21 samples for each core the raw 14c ages assigned to the ash layer peak is significantly older than the 14c age obtained on land part of this discrepancy is due to bioturbation which is shown by numerical modelling nevertheless after correction of a bioturbation bias the mean 14c age obtained on the planktonic foraminifera is still about 11 000 11 100 yr bp the atmosphere sea surface 14c difference was roughly 700 800 yr during the yd whereas today it is 400 500 yr a reduced advection of surface waters to the north atlantic and the presence of sea ice are identified as potential causes of the high 14c reservoir age during the yd

the behaviour of cu and zn isotopes during soil development controls on the dissolved load of rivers abstract the stable isotopes of copper cu and zinc zn are finding increasing applications in surface earth geochemistry an important early observation is that aqueous pools of cu rivers and oceans are isotopically heavier than rocks of the continental crust for zn the global average 66 zn for rivers is identical to estimates of the upper continental crust but the oceans are slightly heavier here we study cu and zn abundances and isotopes in soils to assess how processes in the weathering environment control isotopic values of rivers and ultimately the oceans we investigated a range of soils developed on granitoid scotland and basaltic hawaiian islands rock substrates representing soil development times from 0 1 to 400 kyr mean annual temperatures of 6 16 c and mean annual precipitation map of 1060 5050 mm soils developed on the island of maui over 400 kyr and under high rainfall show the clearest chemical weathering signatures here in oxic soils cu and zn are both depleted by 50 90 with preferential loss of heavy cu 65 cu up to 1 2 lower than parent material and small shifts in 66 zn we attribute this to equilibrium fractionation between aqueous organic species that are removed from the soil versus sorption to residual fe oxyhydroxides in soils that are 0 1 150 kyr old in scotland and hawaii this same pattern is overprinted by biological cycling and the addition of mineral aerosol cu and zn with heavier isotope compositions in reducing soils on maui developed under the highest rainfall cu and zn are almost completely stripped from the soil leaving a very small residual pool with 65 cu and 66 zn values that range from those for the oxic soils back to and beyond parent material this removal of the light sorbed cu seen in oxic soils is attributed to the dissolution of fe oxides under anaerobic conditions perhaps microbially mediated leaving a very small residual isotopically heavier pool overall these data suggest that processes in soils create significant variability in cu isotopes with the heavy isotope exported from oxic soils in contrast small isotope fractionations of zn are generated in the soil environment these observations are consistent with those made previously for cu and zn isotopes in rivers but the maximum amount of cu and zn stored by world soils equates to only 30 130 years of the dissolved riverine flux soils cannot be the ultimate repository of the residual cu and zn required balancing the riverine flux and this must ultimately reside in the erosive products of soil formation in continental and ocean margin sediments

biogeochemical cycling of zinc and its isotopes in the southern ocean abstract we report zn concentration and isotope data for seawater samples from the atlantic sector of the southern ocean collected during the ipy geotraces ant xxiv iii cruise along the greenwich zero meridian data are reported for the full depth range of the water column at three stations as well as a transect of surface samples using a new analytical approach that is presented in detail here zn concentrations increase with depth though due to proximity to upwelling sites surface concentrations are not as low as in some parts of the ocean such as further northward into the sub antarctic zone for two depth profiles south of the polar front zone the physical stratification of the upper water column is reflected in sudden near surface changes in zn concentration with depth in contrast beneath 100 300 m zn concentrations barely change with depth zn isotopic data beneath 1000 m for the southern ocean data presented here as well as published data from the north atlantic and north pacific are strikingly homogeneous with an average 66zn 0 53 0 14 2sd 2se 0 03 n 21 the surface southern ocean is more variable with 66zn ranging from 0 07 to 0 80 between the two is a thin horizon at 40 80 m which in the southern ocean as well as the north atlantic and north pacific is characterised by distinctly light isotopic signatures with 66zn about 0 3 lower than surface waters strong correlations between si and zn concentrations seen here and elsewhere coupled to the lack of any systematic relationship between si and zn isotopes in the southern ocean suggest that the removal of zn associated with diatom opal involves little or no isotopic fractionation regeneration of this zn also explains the homogeneous zn isotopic composition of the global deep ocean so far sampled however the low zn content of opal requires that deep ocean zn does not directly come from the opal phase itself but rather from associated organic material external to the diatom frustule during growth experimental data are consistent with little or no fractionation during incorporation of zn into this material on the other hand the light zinc at 40 80 m is most consistent with the regeneration of an intra cellular pool that both culturing experiments and field data suggest will be isotopically light the data thus imply two processes by which zn is taken up in the surface ocean that these pools have very different regeneration lengthscales and that physical mixing of the oceans cannot eradicate their isotopic signatures finally the deep 66zn ocean value is significantly higher than the current best estimate of the input to the oceans the most obvious candidate for the required light sink is the survival of some of the cellular zn to be buried in sediment

zinc isotope variation in hydrothermal systems preliminary evidence from the irish midlands ore field little is known about the range or controls on the zinc isotope composition of terrestrial materials and no systematic studies have been carried out on ore forming systems we have obtained zinc isotope data from 19 sphalerite samples formed over a range of well constrained precipitation conditions from the irish zn pb ore field the results reveal variation in 66zn where 66zn 66zn 64zn sample 66zn 64zn standard 1 1000 from 0 17 to 1 33 per mil relative to the lyon jmc 3 0749l zinc standard this variation is significant compared to the external reproducibility 0 12 2 and the data show very good mass dependency with 67zn and 68zn values thus natural variations in the zinc isotope composition of these ore minerals can be resolved our results span the entire range of 66zn values measured on terrestrial geologic samples to date the data suggest that variations in the primary source rock composition or precipitation temperature are unlikely to be important controls on the zinc isotope composition of sphalerite in the ore field we suggest that the variation is most likely due to a kinetic fractionation involving the preferential incorporation of light zinc isotopes in sphalerite precipitated rapidly under disequilibrium conditions however we cannot rule out the possibility of mixing of zinc derived from two isotopically distinct sources the significant variation in zinc isotope compositions we have observed in the irish ore field confirms that such fractionations can provide new insights into mineralizing processes in the earth s crust

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

climatic instability ice sheets and ocean dynamics at high northern latitudes during the last glacial period 58 10 ka bp abstract oxygen isotope magnetic susceptibility and foraminiferal distribution data are presented for a high resolution core enam93 21 located at the northeast faeroe margin this core recorded a rapid succession of faunistic sedimentologic and isotopic variations which paralleled the greenland ice core isotopic records with their typical succession of abrupt temperature rises and gradual coolings the dansgaard oeschger cycles the most notable feature was the contemporaneous changes in surface and bottom water conditions and circulation that appeared tightly coupled with the rapid climate fluctuations warm episodes interstadials were appeared with higher sea surface temperatures and thermohaline convection in the norwegian greenland sea the polar front was located north of the enam93 21 site cold episodes stadials were associated with an increase in the input of melting fennoscandian icebergs low sea surface temperature and salinity and no thermohaline convection in the norwegian greenland sea intermediate waters changed to an estuarine mode at the faeroe margin with a reversed flow pattern through the faeroe shetland channel the polar front was located south of the enam93 21 site

zinc isotope evidence for intensive magmatism immediately before the end permian mass extinction the end permian extinction is typically ascribed to massive volcanic eruptions but direct geochemical evidence linking the two independent events is generally lacking zinc is an important micronutrient of marine phytoplanktons and zn isotope 66zn ratios of seawater are markedly higher than those of volcanic rocks and riverine waters we conducted high resolution zn concentration and zn isotope analyses on carbonate rocks across the permian triassic boundary ptb in the meishan section of south china an abrupt increase of zn concentration and a concomitant 0 5 decrease in 66zn occur 35 k y before the mass extinction and carbon isotope 13c minima mass balance calculation demonstrates that a 0 5 negative shift in 66zn within thousands of years requires rapid and massive input of isotopically light zn from volcanic ashes hydrothermal inputs and or extremely fast weathering of large igneous provinces a positive 66zn shift of as much as 1 0 following the mass extinction demonstrates that primary productivity recovered and reached a maximum in fewer than 360 k y our finding provides insights into the marine zn cycling across the ptb and clarifies the temporal relationship and duration of events including intensive volcanism carbon isotope excursion mass extinction and widespread ocean anoxia

cadmium isotope fractionation in seawater a signature of biological activity investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element here we present the results of cd isotope and concentration analyses for 22 seawater samples from the atlantic southern pacific and arctic oceans the results reveal for the first time large and well resolved cd isotope fractionations in the marine environment the majority of the seawater samples display an inverse relationship between dissolved cd contents and isotope compositions which range from e114 110cd 3 0 5 for cd rich waters 0 8 1 0 nmol kg to e114 110cd 38 6 for surface water with a cd concentration of only 0 003 nmol kg all e114 110cd data are reported relative to the jmc cd munster standard this suggests that the cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater cd by phytoplankton a few samples do not follow this trend as they exhibit extremely low cd contents 0 008 nmol kg and nearly un fractionated cd isotope compositions such complexities which are not revealed by concentration data alone require that the cd distribution at the respective sites was affected by additional processes such as water mass mixing atmospheric inputs of cd and or adsorption uniform isotope compositions of e114 110cd 3 3 0 5 1 s d were determined for seawater from 900 m depth despite of cd concentrations that display the expected increase along the global deep water pathway from the atlantic 0 3 nmol kg to the pacific ocean 0 9 nmol kg this indicates that the biomass which is remineralized in the deeper ocean is also characterized by a very constant cd isotope composition this observation is in accord with the interpretation that the cd distribution in surface waters is primarily governed by rayleigh fractionation during near quantitative uptake of dissolved seawater cd

the oceanic biogeochemistry of nickel and its isotopes new data from the south atlantic and the southern ocean biogeochemical divide abstract nickel ni is important for a number of enzymes in oceanic phytoplankton it has received less attention than some other bioactive metals because it is not reduced to extremely low dissolved concentrations in the photic zone however there are strong indications in previous studies that this residual pool is not bio available oceanic ni isotope data are still scarce but have great potential for understanding this issue as well as for understanding the ni mass balance of the oceans now and in the past here we present new concentration and isotope data for the uk geotraces section at 40 s in the atlantic ga10 nickel concentration data show typical nutrient like profiles slightly modified by variable pre formed concentrations in sub surface water masses e g north atlantic deep water nickel isotopes in common with findings in previous studies are homogeneous beneath 500 m at about 1 3 in 60 ni in samples with ni concentrations above 3 3 5 nm the surface south atlantic however has concentrations below 3 nm and shows significantly higher 60 ni up to 1 74 that are closely anti correlated with ni concentrations the data for the deep south atlantic dissolved pool with a 60 ni 1 31 0 12 average and 2sd confirm the homogeneity of the global deep ocean which previous data demonstrate extends all the way to the surface in the upwelling zone of the southern ocean south of the polar front this ni isotope composition is significantly heavier than known inputs to the oceanic dissolved pool this mass balance requires an isotopically light sink that may be represented by sedimentary mn oxide associated ni the magnitude of the isotope fractionation implied by the upper ocean data is not consistent with plausible potential abiotic removal processes rather these data are best explained by biological uptake however consideration of the detailed relationships between ni concentrations and isotope compositions requires that a substantial portion of the oceanic dissolved ni pool is not bio available the data are consistent either with a small preference for the light isotope during uptake about 0 1 or two distinct pools of dissolved ni one bio available and one strongly bound in organic complexes with limited isotopic exchange between them patterns of co variation in ni concentrations and isotopes with the major nutrients point to strong contrasts across the polar front of the southern ocean contrasts that exhibit both similarities and differences with those for the major nutrients and other trace metal micronutrients south of the polar front ni is taken up in modest amounts by diatoms without isotope fractionation north of the polar front the data are most consistent with cyanobacteria as the dominant control on ni uptake leading to significant coupled abundance and isotope variation

new radiocarbon dates for the vedde ash and the saksunarvatn ash from western norway abstract the vedde ash bed mid younger dryas and the saksunarvatn ash early holocene are important regional stratigraphic event markers in the north atlantic the norwegian sea and the adjacent land area it is thus essential to date them as precisely as possible the occurrence of the saksunarvatn ash is reported for the first time from western norway and both tephras are dated precisely by ams analyses of terrestrial plant material and lake sediment at krakenes the vedde ash has been previously dated at sites in western norway to about 10 600 yr b p it is obvious in the younger dryas sediments at krakenes and its identity is confirmed geochemically the mean of four ams dates of samples ofsalix herbacealeaves adjacent to the tephra is 10 310 50 yr b p the saksunarvatn ash is not visible in the early holocene lake sediment at krakenes after removal of organic material and diatoms the identity of the tephra particles was confirmed geochemically and their stratigraphic concentration was estimated from curve matching of a series of seven ams dates of terrestrial plant macrofossils and whole sediment the radiocarbon age of the ash is 8930 9060 yr b p corresponding to an age of 9930 10 010 cal yr b p 7980 8060 cal yr b c

high resolution stratigraphy of the faeroe shetland channel and its relation to north atlantic paleoceanography the last 87 kyr abstract two piston cores from the faeroe shetland channel have been investigated for stratigraphic and paleoceanographic correlation with atlantic ocean and norwegian sea records the high resolution cores have been analyzed for the downcore distribution of planktic and benthic foraminifera and oxygen isotopes ams 14 c dates and the position of ash layers i and ii form the basis for the correlation core na81 10 covers the period from isotope stage 3 to recent stage 1 while core na81 04 covers isotope stages 5a to 1 the holocene is well represented in core na81 10 by 2 m of sediment whereas it is only 50 cm in core na81 04 which is situated directly under the main core of the norwegian sea deep water outflow the transition of isotope stage 2 to stage 1 is affected by dissolution and thus is less clearly represented ams 14 c dates show that termination ia begins at 16 ka and ends at about the 13 ka level the last glacial maximum lgm defined at 19 16 ka is characterized by an ird peak faunal planktic foraminifera maxima dated at 17 3 and 18 25 ka and a high percentage of globigerina quinqueloba apparently open water conditions and circulation within the norwegian sea prevailed at least from 22 5 to 14 8 ka during the greatest part of stage 2 including the lgm and well onto termination ia a preservation maximum is observed throughout stage 2 isotope stage 3 with a nearly complete record of isotope substages is well represented in both cores oxygen isotope depletion peaks correlate with fauna minima and in time to north atlantic heinrich events h5 h1 faunal data indicate that deep water is generated within the norwegian greenland sea repeatedly since 26 ka with stops prior to 26 ka 22 5 20 8 20 5 ka and between 14 9 and 13 ka h3 h2 and h1 all isotope depletion peaks since ca 50 ka are anticorrelated with fauna and are mainly controlled by surface salinity changes isotope stages and substages are directly correlated to fauna peaks and temperature between 87 and ca 50 ka the faeroe shetland channel record shows that repeated presences of atlantic surface water and deep convection alternating with convection shutdowns have occurred within the norwegian sea greenland sea from the beginning of stages 5a to 1

paleoceanographic reconstructions of surface ocean conditions in the greenland iceland and norwegian seas through the last 14 ka based on diatoms prior reconstructions of the last glacial maximum and the holocene did not include detailed paleoclimate data from the greenland iceland and norwegian gin seas which cover sensitive areas for oceanographic boundaries sea ice distribution and deep water formation in order to fill this gap we studied nine well dated sediment cores from this area and reconstructed the paleoceanographic conditions of the surface gin seas at 2000 year intervals since 13 400 bp based on the diatom record results show that a n s extending sea ice free corridor had opened along norway already at 13 400 bp indicating a northward flow of a branch of the north atlantic drift possibly caused by a change in the jet stream flow due to the decreased height of the north american ice sheet a major change of climatic conditions occurred over the gin seas as the insolation anomaly reached its maximum around 9000 bp when the sea ice cover and the oceanic fronts retreated to a northwesterly position along greenland and the ocean temperatures rose the first half of the holocene is recorded as the warmest period during the last 13 400 bp in the gin seas the duration of this climatic optimum decreased both toward the north and toward the margins of the area the second half of the holocene is characterized by a cooling trend in step with the decreasing insolation these results support the proposal of imbrie et al 1992 that the gin seas region acts as an initial responder to insolation changes