the evolution of climatically driven weathering inputs into the western arctic ocean since the late miocene radiogenic isotope evidence highlights seawater hf nd pb isotopic evolution in the deep arctic ocean of the past 7 myr climatically driven changes in weathering inputs since 4 ma north american laurentide ice sheet runoff controlled the isotopic budget in the canada basin more congruent hf release due to glacial weathering conditions past arctic ocean water masses show larger isotopic differences than today abstract we present the first continuous records of dissolved radiogenic neodymium hafnium and lead isotope compositions of deep waters in the western arctic ocean spanning the time from the late miocene to the present the data were obtained from three hydrogenetic ferromanganese fe mn crusts recovered from seamounts along the northernmost edge of the northwind ridge in the canada basin from water depths of 2200 2400 and 3600 m dating the crusts using cosmogenic 10be documents undisturbed present day growth surfaces and yields growth rates between 27 and 2 2 mm myr the nd hf isotope time series of the three crusts show similar evolutions from endend ehf ehf of 8 5 4 in the oldest parts to 11 5 4 at the surfaces and a pronounced trend to less radiogenic values starting at 4 ma this coincided with a trend of the pb isotope evolution towards more radiogenic 206pb 204pb 207pb 204pb and 208pb 204pb it is inferred that climatically controlled changes in weathering regime and sediment transport along the north american continent were responsible for the major change of the radiogenic isotope composition of the arctic deep water adw in the canada basin based on these records we conclude that weathering inputs from the north american continent linked to enhanced glacial conditions started to increase and to influence the radiogenic isotope composition of adw 4 million years ago and were further intensified at 1 ma these new time series differ markedly from the radiogenic isotope evolution of arctic intermediate water recorded on the lomonosov ridge and suggest that much larger isotopic differences between the water masses of the arctic ocean than today prevailed in the past

geology geochemistry and genesis of the zankan iron deposit in the west kunlun orogen xinjiang china the zankan iron deposit taxkorgan county xinjiang is a recently discovered large fe deposit in western china the deposit is hosted in the bulunkuole metamorphic complex in the taxkorgan terrane of the west kunlun orogen the ores are uniquely composed of magnetite pyrite and anhydrite with variable contents and show massive disseminated and banded styles the ores contain widely varying al2o3 tio2 0 28 5 48 wt zr 3 0 83 ppm and hf 0 2 2 ppm indicating a terrigenous clastic material input detrital contamination is minor as demonstrated by poor correlations of y ho ratio vs zr th hf and al2o3 contents as well as zr vs tio2 the ores contain seawater like lree depletion positive la and y anomalies and occasional eu enrichment which suggest hydrothermal contributions in addition three samples show relatively high rey 604 1254 ppm negative eu anomalies eu eu paas 0 36 0 96 and mree enrichment sm ybpaas 1 25 2 81 suggesting a probable fluvial input and shallow precipitation the 34s ratios range widely 3 2 32 8 and show an alternating and or mixing source of two end members the seawater sulfate may have been an indispensable end member and the other end member may have been the volcanic host rocks in the bulunkuole complex which has likely contributed the ore forming metals integrating evidence from regional geology ore geology and geochemistry we conclude that the zankan fe deposit was the result of an early cambrian seafloor hydrothermal system

constraining erosional input and deep water formation in the north atlantic using nd isotopes many marine radiogenic isotope records show both spatial and temporal variations reflecting both the degree of mixing of distinct sources in the oceans and changes in the distribution of chemical weathering on the continents however changes in weathering and transport processes may themselves affect the composition of radiogenic isotopes released into seawater the provenance of physically weathered material in the labrador sea constrained through the use of ar ar ages of individual detrital minerals has been used to estimate the relative contributions of chemically weathered terranes releasing radiogenic isotopes into the labrador sea a simple box model approach for balancing observed nd isotope variations has been used to constrain the relative importance of localised input in the labrador sea and the subsequent mixing of labrador sea water into north atlantic deep water the long term pattern of erosion and deep water formation around the north atlantic seems to have been a relatively stable feature since 1 5 ma although there has been a dramatic shift in the nature of physical and chemical weathering affecting the release of hf and pb isotopes the modelled nd isotopes imply a relative decrease in water mass advection into the labrador sea between 2 4 and 1 5 ma accompanied by a decrease in the rate of overturning possibly caused by an increased freshwater input into the labrador sea

exchange of neodymium and its isotopes between seawater and small and large particles in the sargasso sea the concentrations and isotopic ratios of nd were measured in small 1 53 m and large 53 m in situ filtered particles sediment trap material sediment and aerosol samples collected during oligotrophic and productive conditions in the sargasso sea atmospheric input is the main source of exogeneous nd into the sargasso sea based on ndal ratios in trapped material we suggest that up to 50 of atmospheric nd could dissolve at the air sea interface the concentration and isotopic composition of nd vary with both depth and the particle size neodymium concentrations of small and large particles increase with depth from 2 9 12 g g and 5 8 11 8 g g respectively at 40 m the nd signature of large particles is significantly more negative nd 0 13 1 0 2 than that of the small ones nd 0 11 7 0 3 and the particles filtered deeper below 237 m the nd 0 values for small particles match the seawater whereas the nd 0 values of large particles remain less radiogenic these differences are related to the different behaviors of the particulate fractions small particles apparently exchange nd with seawater and then sink rapidly to depth as biologically formed aggregates large particles these aggregates isolate the small particles slowing the exchange with the water to produce different signatures between large particles and seawater since these exchange processes modify the particulate nd signature the shallow radiogenic nd 0 signature observed in the surface and subsurface waters in the nw atlantic is not due to external contributions and is likely of advective origin at depth below 800 m the magnitude of the aggregation disaggregation process varies significantly with season the fraction of small particles repackaged into large aggregates can vary from 0 8 to 80 100 in productive and oligotrophic conditions respectively this seasonal variation may correspond to sinking particles of different zooplanktonic origin vertical fluxes of nd into and out of the sargasso sea as well as exchange fluxes in the water column are examined about 50 of the particulate flux from the surface is remineralized at depth a net scavenging flux of 0 8 10 4 g m2 y is required this value corresponds to a scavenging nd residence time of 1900 y considerably longer than previous estimates of global oceanic residence time of nd on the order of 400 y

radiogenic nd isotope labeling of the northern ne atlantic during mis 2 paleoceanographic reconstructions rely on chemical proxies which are controlled by physical chemical and biological marine parameters the accurate interpretation of proxy records relies on the integrity of proxy environmental relationships through time and under changing conditions in this study we closely examine paleo controls on authigenic nd isotope records from five cores in the northern ne atlantic approximating a depth transect allowing spatial and temporal relationships to be reconstructed we compare our nd isotope records with other paleocirculation proxies and consider the sedimentalogical controls on nd isotope signals by comparing ice rafted detritus lithology and counts detrital sediment chemistry and redox sensitive element concentrations measured on foraminifera authigenic coatings with this suite of geochemical and sedimentalogical data we show that nd isotope records in the northern ne atlantic were labeled by radiogenic sediments however this modification did not occur in the pore waters of each core but instead likely reflects changes in the nd isotopic composition of deep waters caused by the input of ice rafted sediment during heinrich events and the last glacial maximum this study has implications for understanding how localized changes in the nd isotope signal can set a watermass end member composition decoupling chemical proxy circulation relationships locally but providing a signal which can be potentially traced along the deep water flowpath such scenarios must be considered in future interpretations of glacial nd isotope records taken from within the ice rafted detritus belt and downstream along watermass flowpaths

rare earth elements and neodymium isotopes in sedimentary organic matter abstract we report rare earth element ree and neodymium nd isotope data for the organic fraction of sediments collected from various depositional environments i e rivers n 25 estuaries n 18 open ocean settings n 15 and cold seeps n 12 sedimentary organic matter som was extracted using a mixed hydrogen peroxide nitric acid solution 20 h2o2 0 02 m hno3 after removal of carbonate and oxy hydroxide phases with dilute hydrochloric acid 0 25 m hcl a series of experimental tests indicate that extraction of sedimentary organic compounds using h2o2 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates however this contamination is expected to be minor for ree because measured concentrations in h2o2 leachates are about two orders of magnitude higher than in the above mentioned phases the mean ree concentrations determined in the h2o2 leachates for samples from rivers estuaries coastal seas and open ocean settings yield relatively similar levels with ree 109 86 ppm mean s n 58 the organic fractions leached from cold seep sediments display even higher concentration levels 285 150 ppm mean s n 12 the h2o2 leachates for most sediments exhibit remarkably similar shale normalized ree patterns all characterized by a mid ree enrichment compared to the other ree this suggests that the distribution of ree in leached sedimentary organic phases is controlled primarily by biogeochemical processes rather than by the composition of the source from which they derive e g pore river or sea water the nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions in contrast the som extracted from marine sediments display end values that typically range between the end signatures for terrestrial organic matter inferred from the analysis of the sedimentary detrital fractions and marine organic matter inferred from the analysis of local surface seawater a notable exception is the case of organic matter om fractions leached from cold seep sediment samples which sometimes exhibit end values markedly different from both terrigenous and surface seawater signatures this suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes recycling pore water ree characterized by a distinct isotopic composition overall our results confirm that organic matter probably plays an important role in the oceanic ree budget through direct scavenging and remineralization within the water column both the high ree abundances and the shape of shale normalized patterns for leached som also suggest that om degradation in sub surface marine sediments during early diagenesis could control to a large extent the distribution of ree in pore waters benthic fluxes of organic bound ree could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins neodymium isotopes could provide useful information for tracing the origin terrestrial versus marine and geographical provenance of organic matter with potential applications in paleoceanography in particular future studies should further investigate the potential of nd isotopes in organic compounds preserved in sedimentary records for reconstructing past variations of surface ocean circulation

neodymium isotopes in seawater from the barents sea and fram strait arctic atlantic gateways abstract the neodymium concentration c nd and isotopic composition e nd in seawater have been determined in the water column at five sites in the barents sea fram strait area where most of the water exchange between the arctic ocean and the north atlantic takes place in the main arctic ocean inflow branch across the barents sea the concentration and isotopic composition c nd 15 5 pmol kg and e nd 10 8 are similar to those reported for the northeastern nordic seas which is consistent with this region being a source area for the arctic inflow due to the addition of nd from svalbard shelf sediments the c nd in the surface waters above 150 m in the fram strait inflow branch is higher by a factor of 2 and the e nd is shifted to lower values 11 8 in the stratified nansen basin where cold low salinity water overlies warmer atlantic water the c nd and e nd do not vary with the vertical temperature salinity structure but are essentially constant and similar to those of the atlantic inflow throughout the entire water column down to 3700 m depth which indicates that the nd is to a large extent of atlantic origin compared to the atlantic inflow water the nd in the major arctic ocean outflow the fram strait show higher c nd in the surface waters above 150 m and a higher e nd 9 8 throughout the entire water column down to 1300 m depth sources for the more radiogenic nd isotopic composition in deep water of the fram strait outflow most likely involve boundary exchange with sediments on the shelf and slope as the water passes along the canadian archipelago river water is a possible source in the surface water but it also seems likely that pacific water nd modified by interactions on the shelf is an important component in the fram strait surface outflow changes in the relative proportions of inflow of river water and flow of pacific water through the arctic ocean could thus influence the isotopic composition of nd in the north atlantic

the leonard award address presented 1996 july 25 berlin germany the elemental composition of stony cosmic spherules five hundred stony cosmic spherules collected from deep sea sediments polar ice and the strato sphere have been analyzed for major and some minor element composition typical spherules are products of atmospheric melting of millimeter sized and smaller meteoroids the samples are small and modified by atmospheric entry but they are an important source of information on the composition of asteroids the spherules in this study were all analyzed in an identical manner and they provide a sampling of the solar system s asteroids that is both different and less biased than provided by studies of conventional meteorites volatile elements such as na and s are depleted due to atmospheric heating while siderophiles are depleted by less understood causes the refractory nonsiderophile elements appear not to have been significantly dis turbed during atmospheric melting and provide important clues on the elemental composition of millimeter sized meteoroids colliding with the earth typical spherules have cm like composition that is distinctively different than ordinary chondrites and most other meteorite types we assume that c type asteroids are the primary origin of spherules with this composition type s asteroids should also be an important source of the spherules and the analysis data provide constraints on their composition a minor fraction of the spher ules are melt products of precursor particles that did not have chondritic elemental compositions the most common of these are particles that are dominated by olivine the observed compositions of spherules are in consistent with the possibility that an appreciable fraction of the spherules are simply chondrules remelted during atmospheric entry

water mass transformation in the barents sea inferred from radiogenic neodymium isotopes rare earth elements and stable oxygen isotopes abstract nearly half the inflow of warm and saline atlantic water aw to the arctic ocean is substantially cooled and freshened in the barents sea which is therefore considered a key region for water mass transformation in the arctic mediterranean am numerous studies have focused on this transformation and the increasing influence of aw on arctic climate and biodiversity yet geochemical investigations of these processes have been scarce using the first comprehensive data set of the distributions of dissolved radiogenic neodymium nd isotopes expressed as nd rare earth elements ree and stable oxygen isotope 18o compositions from this region we are able to constrain the transport and transformation of aw in the barents sea and to investigate which processes change the chemical composition of the water masses beyond what is expected from circulation and mixing inflowing aw and norwegian coastal water ncw both exhibit distinctly unradiogenic nd signatures of 12 4 and 14 5 respectively whereas cold and dense polar water pw has considerably more radiogenic nd signatures reaching up to 8 1 locally formed barents sea atlantic water bsaw and barents sea arctic atlantic water bsaaw are encountered in the northeastern barents sea and have intermediate nd values resulting from admixture of pw containing small amounts of riverine freshwater from the ob 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

breakup of last glacial deep stratification in the south pacific stratification of the deep southern ocean during the last glacial maximum is thought to have facilitated carbon storage and subsequent release during the deglaciation as stratification broke down contributing to atmospheric co2 rise here we present neodymium isotope evidence from deep to abyssal waters in the south pacific that confirms stratification of the deepwater column during the last glacial maximum the results indicate a glacial northward expansion of ross sea bottom water and a southern hemisphere climate trigger for the deglacial breakup of deep stratification it highlights the important role of abyssal waters in sustaining a deep glacial carbon reservoir and southern hemisphere climate change as a prerequisite for the destabilization of the water column and hence the deglacial release of sequestered co2 through upwelling

detection and extraction of fault surfaces in 3d seismic data we propose an efficient method for detecting and extracting fault surfaces in 3d seismic volumes the seismic data are transformed into a volume of local fault extraction lfe estimates that represents the likelihood that a given point lies on a fault surface we partition the fault surfaces into relatively small linear portions which are identified by analyzing tilted and rotated subvolumes throughout the region of interest directional filtering and thresholding further enhance the seismic discontinuities that are attributable to fault surfaces subsequently the volume of lfe estimates is skeletonized and individual fault surfaces are extracted and labeled in the order of decreasing size the ultimate result obtained by the proposed procedure provides a visual and semantic representation of a set of well defined cleanly separated one pixel thick labeled fault surfaces that is readily usable for seismic interpretation

the isotopic composition of neodymium in the north pacific abstract we have determined the isotopic composition of neodymium in two water column profiles in the western north pacific and in bottom waters from three other locations in the north pacific the vertical profiles reveal that the water column is stratified with respect to isotopic composition mid depths associated with pacific deep water are uniform having nd 0 3 shallow waters are variable but deep waters are less radiogenic having md 0 4 4 to 5 in the western basin the more negative bottom waters in the western north pacific provide evidence for the advective transport of rare earth elements from antarctic sources to this region bottom waters in the eastern north pacific are more radiogenic nd 0 3 3 to 3 8 indicating very little transport of ree from antarctic sources to this basin overall the isotopic composition of nd in pacific bottom waters appears to be conservative when compared to the silica distribution in spite of evidence for nd removal the findings are generally compatible with other parameters such as temperature salinity and nutrient distributions the presence of nd isotopic signatures associated with antarctic sources in these waters provides evidence for a small component of rare earth elements of north atlantic origin in the bottom waters of the north pacific this is the first tracer evidence to corroborate the suggestion of reid and lynn 1971 that some of the temperature and salinity properties of the deep waters of the north pacific originated in the norwegian and greenland seas

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

numbers types and compositions of an unbiased collection of cosmic spherules abstract abstract micrometeorites collected from the bottom of the south pole water well spww may represent a complete well preserved sample of the cosmic dust that accreted on earth from 1100 1500 a d we classified 1588 cosmic spherules in the size range 50 800 pm the collection has 41 barred olivine spherules 17 glass spheres 12 cryptocrystalline spherules 11 porphyritic olivine spherules 12 relic grain bearing spherules 3 scoriaceous spherules 2 i type spherules 1 ca al ti rich cat spherules and 1 g type spherules we also found bubbly glass spherules spherules with glass caps and ones with sulfide coatings particles that are absent from other collections a classification sequence of the stony spherules scoriaceous relic grain bearing porphyritic barred olivine cryptocrystalline glass and cat is consistent with progressive heating and evaporation of fe from chondritic materials the modem day accretion rate and size distribution measured at the spww can account for the stony spherules present in deep sea collection through preferential dissolution of glass and small stony spherules however weathering alone cannot account for the high accretion rate of i type spherules determined for two deep sea collections the spww collection provides data to constrain models of atmospheric entry heating and to assess the effects of terrestrial weathering

indian ocean circulation and productivity during the last glacial cycle abstract the indian ocean is an important part of the global thermohaline circulation system receiving deep waters sourced from the southern ocean and being the location of upwelling and surface ocean current flow which returns warm and salty waters to the atlantic it is also an ideal location to reconstruct the link between thermohaline circulation and deep water nutrient contents no mixing occurs between major deep water masses along flow paths within the indian ocean so changes in water mass provenance reflect changes in deep ocean circulation while nutrient contents reflect addition and dissolution of organic matter we present neodymium nd and carbon c isotope records from an equatorial indian ocean core sk129 cr2 spanning the last 150 kyr the nd isotope record shows that an increased proportion of north atlantic deep water nadw reached the indian ocean during interglacials marine isotope stages mis 1 and 5 and a reduced proportion during glacials mis 2 4 and 6 and also that changes occurred during mis 3 the magnitude and timing of deglacial and some mis 3 variability is very similar to those in the rc11 83 tno57 21 south atlantic deep cape basin nd isotope record piotrowski et al 2005 since the deep cape basin is oceanographically upstream of the indian ocean from a deep water circulation perspective the nd isotopes suggest that atlantic meridional overturning circulation changes were effectively propagated from the southeastern atlantic into the central indian ocean via the southern ocean comparison of the nd and c isotope records shows that deep ocean circulation was decoupled from nutrient content changes on glacial interglacial timescales in particular suggesting higher productivity during mis 5 increased equatorial productivity during mis 5 is supported by benthic infaunal epifaunal foraminiferal 13 c gradients as well as benthic foraminiferal 13 c gradients along deep water flow concurrent warming indicated by planktonic foraminiferal mg ca during mis 5 at the site is consistent with changing thermocline temperature and may indicate a link to surface ocean hydrographic changes

neodymium isotopic variations in northwest pacific waters abstract four vertical profiles of the concentration and isotopic composition of nd in seawater were obtained in the western north pacific two profiles from the kuroshio current regime showed congruently that although the nd concentration increases gradually with depth its isotopic composition varies significantly with depth depending upon the water mass occupying the water column the high salinity kuroshio waters originating from the north pacific tropical water nptw carry the least radiogenic nd nd 7 4 to 8 7 to this region at 250 m from the western margin continental shelves most likely from the east china sea the nd isotopic compositions in the north pacific intermediate water npiw that occurs at 600 to 1000 m in the subtropical region are fairly uniform at nd 3 7 the profile data from the 38 to 40 n kuroshio oyashio mixed water region off sanriku of honshu japan also suggest that the newest npiw with nd 3 2 is formed there by the mixing of various source waters and the radiogenic component of nd is derived mainly from the oyashio waters in the pacific deep water pdw below 1000 m the nd isotopic composition is neither vertically nor horizontally homogeneous suggesting that it serves as a useful tracer for sluggish deep water circulation as well two profiles from the izu ogasawara trench showed a minimum nd value at 2000 m suggesting that there exists a horizontal advective flow in the vicinity of honshu japan there is some evidence from other chemical properties to support this observation the waters below 4000 m including those within the trench in the subtropical region have nd values of around 5 suggesting that the deep waters are fed from the south along the western boundary ultimately from the antarctic bottom water aabw in the south pacific this extends up to 40 n along the japanese islands in the subarctic region 42 n the waters have more radiogenic nd with nd 4 0 throughout the water column presumably due to the supply of nd by weathering in such igneous provinces as the kuril kamchatska aleutian island chain the lateral inhomogeneity of the nd isotopic composition in pdw suggests that there may be different circulation and mixing regimes in the north pacific basin

dissolved gallium in the northwest pacific and the south and central atlantic oceans implications for aeolian fe input and a reconsideration of profiles the distribution of dissolved gallium a less reactive analogue of aluminum has the potential to reveal information about the averaged dust input to the surface ocean and to complement studies using aluminum as a tracer new data are presented here on the distribution of dissolved ga including six profiles in the south and central atlantic as well as seven shallow and two deep profiles from the northwest pacific the atlantic data allow for an estimate of ga in antarctic bottom water 25 30 pmol kg 1 and show reasonably conservative behavior in deep waters in the northwest pacific surface water ga al ratios correlate with chlorophyll concentrations probably reflecting the biogenic removal of dissolved al and suggesting a possible means for estimating variation in surface water al removal times also in the northwest pacific low surface water ga in subpolar surface waters suggests low dust input thereby providing an explanation for the high nutrient low chlorophyll behavior of this environment this low ga subpolar water implies that north pacific intermediate water is low in ga and thus provides an advective explanation for the intermediate water ga minimum observed in the temperate north pacific surprisingly the deepest waters sampled in the north pacific have ga concentrations similar to that estimated for circumpolar waters thus indicating minimal reactivity of ga in its northward transit in the deep pacific

redistribution of rare earth elements thorium and uranium over accessory minerals in the course of amphibolite to granulite facies metamorphism the role of apatite and monazite in orthogneisses from southwestern norway the amphibolite to granulite facies transition has been studied in a high k calc alkaline hornblende biotite k feldspar megacrystic augen gneiss series from the rogaland vest agder rog va sector of the sveconorwegian province southwest norway hornblende begins to break down mainly to clinopyroxene at the cpx in isograd and biotite mainly to orthopyroxene at the opx in isograd abbreviations for minerals following kretz 1983 the magmatic accessory mineral association comprises titanite and allanite which begin to break down before the cpx in isograd titanite is preserved as relict inclusions in other minerals at higher grade monazite and thorite formed in the breakdown of allanite monazite abundance reaches a maximum between the cpx in and opx in isograds the middle and heavy rare earth element m hrees except eu content of apatite steeply increases with increasing metamorphic grade and is directly correlated to the decrease of the modal abundances of titanite hornblende and biotite the u contents of apatite are low and do not increase with metamorphic grade the light rare earth elements lrees and th content of apatite are not correlated to the breakdown of allanite around the cpx in isograd but increase around the opx in isograd a simplified equation is proposed for monazite crystallisation in the vicinity of the cpx in isograd that accounts for the allanite titanite and hornblende breakdowns and the m hree substitution in apatite 3 m hree 2o3in hornblende and litanite 3 lree 2in allaniteo3 2ca5 po4 3apatite f oh 6sio2quartz 6 lree pmonaziteo4 2ca2 m hree 3 sio4 3 f oh lessingite in apatite 6caoin plagioclase at the opx in isograd the increase of lrees and th content of apatite results either from the breakdown of some monazite 3 lree po4monazite 3sio2quartz 4caoin plagioclase f2 h2o fluid ca5 po4 3 f oh apatiteca2 lree 3 sio4 3 f oh less ingite in apatite or the breakdown of the remaining allanite 3 lree 2o3in allanite 6sio2quartz 4caoin plagioclase f2 h2o fluid 2ca2 lree 3 sio4 3 f oh lessingite in apatite the release of fluorine from the breakdown of biotite at the opx in isograd may increase apatite stability relatively to monazite in the granulite facies when compared to amphibolite facies the granulite facies augen gneisses do not show any u or th depletion this means that changes in the accessory mineral associations and the simultaneous breakdown of hydrous minerals at the amphibolite granulite facies transition do not inevitably result in depleted granulite facies rocks but rather to an isochemical element redistribution the coexistence of small amounts of metamorphic monazite and of relict inclusions of titanite in upper amphibolite facies augen gneisses suggests that high k calc alkaline orthogneisses are a suitable material to date with the u pb method prograde path of amphibolite facies regional metamorphism on monazite and the cooling path on titanite

importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern indian ocean vertical profiles of dissolved rare earth elements rees were obtained in the bay of bengal and the andaman sea the ree concentrations at various depths in the bay of bengal are the highest in the indian ocean this is attributable ultimately to the large outflow of the ganges brahmaputra and irrawaddy rivers but the dissolved ree flux to surface waters alone cannot explain the large and near constant ree enrichment throughout the entire water column the underlying fan sediments serve as not a source but a sink for dissolved ree iii s absence of excess 228ra in the deep waters suggests that lateral input of dissolved rees from slope sediments is also small in these regions partial 0 3 dissolution of detrital particles which are carried by the rivers and lateral surface currents and subsequently settle through the water column appears to be a predominant source for the dissolved rees vertical profiles showing an almost linear increase with depth are common features for the light and middle rees everywhere but their concentration levels are variable from basin to basin and from element to element this suggests that their oceanic distributions respond quickly to the variation of particle flux and its ree composition through reversible exchange equilibrium with suspended and sinking particles much like the case for th the relative importance of the vertical geochemical processes of reversible scavenging over the horizontal basin scale ocean circulation with passive regeneration like nutrients decreases systematically from the light to the heavy rees using a model the mean oceanic residence times of rees in the bay of bengal are estimated to range from 37 years for ce to 140 1510 years for the strictly trivalent rees in the deep water of the andaman sea isolated from the bay of bengal by the andaman nicobar ridge maximum sill depth of 1800 m the ree concentrations are almost uniform presumably due to rapid vertical mixing the ree iii concentrations are similar to that of 1250 m depth water in the bay of bengal consistent with other oceanographic properties however the ree composition of the deep water appears to be altered slightly by preferential scavenging of the light ree iii at the bottom boundary of the basin

neodymium isotopes and concentrations in caribbean seawater tracing water mass mixing and continental input in a semi enclosed ocean basin we present the first full water column nd isotope end and concentration data for caribbean seawater as well as for stations close to the orinoco river mouth and in the florida straits the surface inflow into the southeastern caribbean via the guyana current is characterized by an endsignature of 10 9 which is a consequence of the mixing of relatively unradiogenic endsignatures 13 6 supplied by the orinoco river with contributions from the amazon river 10 despite the proximity to land sub surface and intermediate waters within the caribbean largely retain the endsignatures of their source water masses in the atlantic in contrast the deep waters of the caribbean show endsignatures at least 3 endunits more radiogenic than the inflowing upper north atlantic deep water unadw a endshift from 13 to 9 7 can be explained by addition of radiogenic nd to the deep caribbean through weathering inputs from land however in order to balance such large shifts in endwith at the same time modest increases in nd concentrations nd must also be removed from seawater within the basin it is suggested that the long residence time of deep waters in the caribbean allows significant interaction of seawater with sinking particles and seafloor sediments resulting in more radiogenic values these findings have implications for the use of endas a proxy for paleocirculation in restricted basins in which the residence times of the deep waters are long

the distribution of neodymium isotopes in arctic ocean basins nd concentration and isotope data have been obtained for the canada amundsen and makarov basins of the arctic ocean a pattern of high nd concentrations up to 58 pm at shallow depths is seen throughout the arctic and is distinct from that generally seen in other oceans where surface waters are relatively depleted a range of isotopic variations across the arctic and within individual depth profiles reflects the different sources of waters the dominant source of water and so nd is the atlantic ocean with lesser contributions from the pacific and arctic rivers radiogenic isotope nd signatures up to epsilon nd 6 5 can be traced in pacific water flowing into the canada basin waters from rivers draining older terrains provide very unradiogenic nd down to epsilon nd 14 2 that can be traced in surface waters across much of the eurasian basin a distinct feature of the arctic is the general influence of the shelves on the nd concentrations of waters flowing into the basins either from the pacific across the chukchi sea or from across the extensive siberian shelves water shelf interaction results in an increase in nd concentration without significant changes in salinity in essentially all waters in the arctic through processes that are not yet well understood in estuarine regions other processes modify the nd signal of freshwater components supplied into the arctic basin and possibly also contribute to sedimentary nd that may be subsequently involved in sediment water interactions mixing relationships indicate that in estuaries nd is removed from major river waters to different degrees deep waters in the arctic are higher in nd than the inflowing atlantic waters apparently through enrichments of waters on the shelves that are involved in ventilating the deep basins these enrichments generally have not resulted in major shifts in the isotopic compositions of the deep waters in the makarov basin epsilon nd similar to 10 5 but have created distinctive nd isotope signatures that were found near the margin of the canada basin with epsilon nd similar to 9 0 the deep waters of the amundsen basin are also distinct from the atlantic waters with epsilon nd 12 3 indicating that there has been limited inflow from the adjacent makarov basin through the lomonosov ridge c 2009 elsevier ltd all rights reserved

radiogenic isotopic compositions of low concentration dust and aerosol from the gisp2 ice core abstract we have produced a record of radiogenic isotope compositions of particulate and soluble dust fractions from the gisp2 ice core from basal ice to the surface for each respective dust fraction we measured sr and nd isotope values to constrain the provenance of mineral dust and sea salt aerosol transported to the greenland ice sheet we have produced high precision measurements of end values on sub ng quantities of nd in ice core samples via tims with 1013 ohm resistors the range of measured end values of soluble material 12 9 2 6 to 7 3 0 9 is interpreted to represent sea salt aerosol based on sr isotope compositions that resemble seawater values 0 711007 0 000030 to 0 709416 0 000072 therefore the end potentially provides important insights to the atmospheric circulation patterns at high latitudes at least through mis 5 we compare end values of surface seawater from ocean basins and deltas at high latitudes to alternating relatively radiogenic and unradiogenic end at gisp2 we suggest these changes represent transitions between a climate system dominated by enhanced and persistent arctic oscillation positive anomalies as determined from sea level and ocean bottom pressure measurements and a state representative of modern atmospheric circulation which typically exhibits either negative anomalies or none altogether

crumbs from the crust of vesta achondritic cosmic spherules from the south pole water well ten glass cosmic spherules cs from the south pole water well collection were analyzed by electron microprobe nine of them have fe mn and fe mg ratios in the range typical of chondrites one of them sp37 3 along with up to six other previously analyzed cs have nonchondritic fe mn and fe mg ratios that agree well with values typical of either basaltic howardite eucrite and diogenite hed meteorites or martian basalts but not of lunar samples sp37 3 also contains an anorthite relic grain anorthite has not previously been reported in cosmic spherules but is well known in hed meteorites the much greater frequency of heds among hand sized meteorites suggests but does not prove that hed precursors are more likely for the nonchondritic spherules we estimate that hed like micrometeorites constitute 0 5 0 4 of the total population of micrometeorites in the south pole water well a fraction that translates to a flux of 1 6 0 3 x 10 8 g hed micrometeorites m 2 y the ratio of hed like objects to carbonaceous objects is about 100 times less in micrometeorites than among hand size specimens we infer that the comparative mechanical weakness of carbonaceous precursor materials tends to encourage spherule formation

temporal and tectonic evolution of the granulite eclogite association from the bergen arcs western norway the u pb and sm nd dating of deep crustal rocks from the bergen arcs system helps resolve enigmatic aspects of the tectonic evolution of the caledonian orogen in western norway and yields insights into the arrested stages of eclogite development within the granulites of the area the u pb dating of zircon from one of the eclogite facies shear zones yields an upper intercept age of 945 5 ma all errors two standard deviations 2 which is similar to other zircon ages from the granulite facies protolith the age is interpreted to represent the time of late proterozoic sveconorwegian granulite metamorphism the u pb ages of sphene and epidote show that the eclogites formed early in the evolution of the caledonian orogen pre scandian phase at about 460 ma an eclogite facies quartz vein yields a sm nd whole rock garnet isochron of 440 12 ma that may reflect the onset of cooling immediately after peak eclogite facies conditions although the sm nd systematics reveal some isotopic disequilibrium within the sample in tandem with previous 40ar39ar age determinations from an adjacent eclogite of 450 ma for hornblende and 430 ma for muscovite these data indicate that 30 ma elapsed between formation of the eclogites and the initial stages of cooling and exhumation to at least mid crustal levels this corresponds to minimum cooling rates of 14 c m y the timing relations suggest that the formation and exhumation of these eclogites from the overlying caledonian nappe wedge in western norway are related to an early phase of crustal subduction during or somewhat before the major phase of continent continent collision the short period of time between the formation of the eclogites and the initial stages of exhumation and rapid cooling is consistent with the only partial and localized transformation of the granulite to eclogite isolated occurrences of eclogite within the granulite the formation of eclogite along metasomatic fronts and the formation of hydrous eclogite facies minerals within the dry granulite all point to the importance of fluids in the transformation and re equilibration of the granulite to eclogite together field and isotopic data demonstrate that both the localized and limited access of fluids and the rapid cycling of continental crust through the deepest portions of the orogen to upper crustal levels resulted in the preservation of the arrested stages of eclogite formation and survival of the granulites metastably through eclogite facies conditions

changes in north atlantic deep water strength and bottom water masses during marine isotope stage 3 45 35kabp the strength of the north atlantic meridional overturning circulation during climatically highly variable marine isotope stage mis 3 has attracted much attention in recent years here we present highresolution nd isotope compositions of past seawater derived from authigenic fe mn oxyhydroxides recovered from drift sediments on the blake ridge in the deep western north atlantic odp leg 172 site 1060 3481 m water depth the data cover the period from 45 to 35 ka bp tracing circulation changes during major heinrich iceberg discharge event 4 h4 40 39kabp the nd isotope record suggests that there was no northern source water nsw mass like modern nadw at the deeper part of blake ridge at any time between 45 and 35 ka this is fundamentally different from the hydrographic situation during the holocene where nadw extends below 4500 m at this location the end of past deep water recorded in the blake ridge sediments was least radiogenic during dansgaard oeschger d o interstadial is 8 end 11 3 and most radiogenic immediately preceding is 9 end 9 8 more radiogenic compositions were also recorded during h4 10 2 end 9 9 the nd isotope variability in mis 3 matches that of a physical bottom current strength reconstruction from the same location neither record follows the pattern of northern hemisphere d o climatic cycles in our record reduced mixing with northern source waters started in stadial 12 and lasted until after h4 in stadial 9 followed by a rapid increase in nsw contribution thereafter this major change in the nd isotope record predates the iceberg discharge event heinrich 4 by more than 3 ka indicating a shallowing of the water mass boundary between glacial north atlantic intermediate water and southern source water beneath this early change in bottom water properties at the deep blake ridge suggests that north atlantic deep water advection may already have decreased several thousand years before the actual iceberg discharge event and associated freshening of the surface waters in the north atlantic the change can thus not be attributed to climatic events in the north atlantic but may be related to changes in flux of deep water from the south

3 d seismic attributes using a semblance based coherency algorithm seismic coherency is a measure of lateral changes in the seismic response caused by variation in structure stratigraphy lithology porosity and the presence of hydrocarbons unlike shaded relief maps that allow 3 d visualization of faults and channels from horizon picks seismic coherency operates on the seismic data itself and is therefore unencumbered by interpreter or automatic picker biases we present a more robust multitrace semblance based coherency algorithm that allows us to analyze data of lesser quality than our original three trace cross correlation based algorithm this second generation semblance based coherency algorithm provides improved vertical resolution over our original zero mean crosscorrelation algorithm resulting in reduced mixing of overlying or underlying stratigraphic features in general we analyze stratigraphic features using as narrow a temporal analysis window as possible typically determined by the highest usable frequency in the input seismic data in the limit one may confidently apply our new semblance based algorithm to a one sample thick seismic volume extracted along a conventionally picked stratigraphic horizon corresponding to a peak or trough whose amplitudes lie sufficiently above the ambient seismic noise in contrast near vertical structural features such as faults are better enhanced when using a longer temporal analysis window corresponding to the lowest usable frequency in the input data the calculation of reflector dip azimuth throughout the data volume allows us to generalize the calculation of conventional complex trace attributes including envelope phase frequency and bandwidth to the calculation of complex reflector attributes generated by slant stacking the input data along the reflector dip within the coherency analysis window these more robust complex reflector attribute cubes can be combined with coherency and dip azimuth cubes using conventional geostatistical clustering and segmentation algorithms to provide an integrated multiattribute analysis

interior textures chemical compositions and noble gas signatures of antarctic cosmic spherules possible sources of spherules with long exposure ages abstract the interior texture and chemical and noble gas composition of 99 cosmic spherules collected from the meteorite ice field around the yamato mountains in antarctica were investigated their textures were used to classify the spherules into six different types reflecting the degree of heating 13 were cryptocrystalline 40 were barred olivine 3 were porphyritic a 24 were porphyritic b 9 were porphyritic c and 10 were partially melted spherules while a correlation exists between the type of spherule and its noble gas content there is no significant correlation between its chemical composition and noble gas content fifteen of the spherules still had detectable amounts of extraterrestrial he and the majority of them had 3he 4he ratios that were close to that of solar wind sw the ne isotopic composition of 28 of the spherules clustered between implantation fractionated sw and air extraterrestrial ar confirmed to be present because it had a 40ar 36ar ratio lower than that of terrestrial atmosphere was found in 35 of the spherules an enigmatic spherule labeled m240410 had an extremely high concentration of cosmogenic nuclides assuming 4 exposure to galactic and solar cosmic rays as a micrometeoroid and no exposure on the parent body the cosmic ray exposure cre age of 393 myr could be computed using cosmogenic 21ne under these model assumptions the inferred age suggests that the particle might have been an edgeworth kuiper belt object alternatively if exposure near the surface of its parent body was dominant the cre age of 382 myr can be estimated from the cosmogenic 38ar using the production rate of the 2 exposure geometry and implies that the particle may have originated in the mature regolith of an asteroid

dynamic intermediate ocean circulation in the north atlantic during heinrich stadial 1 a radiocarbon and neodymium isotope perspective the last deglaciation was characterised by a series of millennial scale climate events that have been linked to deep ocean variability while often implied in interpretations few direct constraints exist on circulation changes at mid depths here we provide new constraints on the variability of deglacial mid depth circulation using combined radiocarbon and neodymium isotopes in 24 north atlantic deep sea corals their aragonite skeletons have been dated by uranium series providing absolute ages and the resolution to record centennial scale changes while transects spanning the lifetime of a single coral allow sub centennial tracer reconstruction our results reveal that rapid fluctuations of water mass sourcing and radiocarbon affected the mid depth water column 1 7 2 5 km on timescales of less than 100 years during the latter half of heinrich stadial 1 the neodymium isotopic variability 14 5 to 11 0 ranges from the composition of the modern northern sourced waters towards more radiogenic compositions that suggest the presence of a greater southern sourced component at some times however in detail simple two component mixing between well ventilated northern sourced and radiocarbon depleted southern sourced water masses cannot explain all our data instead corals from 15 0 ka and 15 8 ka may record variability between southern sourced intermediate waters and radiocarbon depleted northern sourced waters unless there was a major shift in the neodymium isotopic composition of the northern endmember in order to explain the rapid shift towards the most depleted radiocarbon values at 15 4 ka we suggest a different mixing scenario involving either radiocarbon depleted deep water from the greenland iceland norwegian seas or a southern sourced deep water mass since these mid depth changes preceded the bolling allerod warming and were apparently unaccompanied by changes in the deep atlantic they may indicate an important role for the intermediate ocean in the early deglacial climate evolution

accretion of extraterrestrial matter during the last 80 million years and its effect on the marine osmium isotope record the flux of particulate extraterrestrial et matter to the deep sea has been calculated using a four component mixing model based on osmium concentrations and isotope ratios in slowly accumulating pelagic sediments from the pacific ocean nineteen published bulk leach osmium isotope data pairs that cover the last 80 million years have been used for the calculation the calculated annual particulate flux averaged over several 100 ka by slow accumulation and bioturbation ranges from 18 000 to 67 000 tons with a mean value of 37 000 13 000 tons the data indicate no significant variability in the flux with time except at the k t boundary and are thus compatible with results based on ir accumulation in deep sea sediments the inferred constancy of the et matter flux is in contrast to recent results based on the et 3he flux that integrates only a small size fraction of the entire et matter flux 3he data indicate variability by a factor of 6 over the past 70 ma and a fivefold increase in the et flux between 3 ma and 1 ma that is not seen in the bulk et matter flux based on osmium isotope data the apparent constancy of the cosmic matter flux over the past 80 ma stands in marked contrast to the dynamic nature of the marine osmium isotope record and indicates that dissolution of cosmic matter does not drive changes in this record except at the k t boundary a comparison between osmium isotope and ir data from two pelagic sediment cores from the pacific dsdp site 596 and ll44 gpc3 indicates that the seawater soluble fraction of et os cannot exceed 36 kg a and most likely is significantly smaller the maximum value of 36 kg a can account for approximately one half of the seawater soluble et matter flux necessary to balance the radiogenic continental runoff of os without any additional unradiogenic source simple mass balance calculations indicate that an additional unradiogenic source of os to the oceans most likely alteration of oceanic crust is required to balance the present day seawater osmium isotopic composition this source is probably more important in balancing radiogenic continental runoff than is dissolution of cosmic matter in seawater

oxygen isotopic and chemical compositions of cosmic spherules collected from the antarctic ice sheet implications for their precursor materials abstract bulk chemical compositions and oxygen isotopic compositions were analyzed for 48 stony cosmic spherules melted micrometeorites collected from the antarctic ice sheet using electron and ion microprobes no clear correlation was found between their isotopic compositions and textures the oxygen isotopic compositions showed an extremely wide range from 28 to 93 in 18o and from 21 to 13 in 17o in 18o 17o space most samples 38 out of 48 plot close to the terrestrial fractionation line but 7 samples plot along the carbonaceous chondrite anhydrous mineral ccam line three samples plot well above the terrestrial fractionation line one of these has a 17o of 13 the largest value ever found in solar system materials one possible precursor for this spherule could be 16o poor planetary material that is still unknown as a meteorite the majority of the remaining spherules are thought to be related to carbonaceous chondrites

acquisition of the neodymium isotopic composition of the north atlantic deep water the north atlantic deep water nadw neodymium isotopic composition nd ic is increasingly used in oceanography and paleoceanography to trace large scale circulation and weathering processes notably to investigate past variations of the global thermohaline circulation although the present day nadw nd ic is well characterized at nd 13 5 the acquisition of this isotopic signature in other words the causes of this value has so far been very sparsely documented such an understanding is however fundamental to the interpretation of paleo records nd ic and rare earth element concentrations were measured at 9 stations within the north atlantic subpolar gyre signature cruise summer 1999 the comparison of this data set with our understanding of water mass circulation provides a description of how the three layers constituting the nadw the labrador sea water lsw nd 13 9 0 4 north east atlantic deep water neadw nd 13 2 0 4 and north west atlantic bottom water nwabw nd 14 5 0 4 acquire their nd ic through distinct water mass mixings and lithogenic inputs these different mechanisms acting upon water masses from very diverse sources seem to bring the nd ic of the three nadw layers to values close together and similar to that of the nadw it is suggested that sediment seawater interactions significantly lower the neadw and nwabw nd ic along the south east greenland margin since these interactions do not significantly modify the nd content of these water masses sediment remobilizations leading to the nd ic variations are probably associated with nd removal fluxes from the water mass toward the sediment a process called boundary exchange on the other hand lsw seems to acquire its nd ic from the subpolar mode waters from which it is formed by deep convection and no other mechanism needs to be invoked its unradiogenic signature could ultimately be linked to fresh water runoff from the canadian shield these conclusions should allow more precise interpretations of paleoceanographic nd ic records taking into account the distinct histories of the three nadw layers including distinct water mass mixings and distinct lithogenic inputs

rare earth elements of shallow water articulated brachiopods a bathymetric sensor abstract variations in environmental physicochemical parameters result in corresponding changes in seawater rare earth element ree distributions for an archive to be utilized in paleoceanographic and paleoenvironmental reconstructions it should record these variations therefore an archive s proxy potentiality should be assessed analogous to modern oceanic settings articulated brachiopods of several shallow water localities the mean ree sn pattern of shallow water brachiopods is significantly different from that of their deep water counterparts with lower enrichments in lrees and mrees and depletion in hrees depth exercises a major control on the lree and mree fractionation with a milder one on hree fractionation the ce ce anomaly is not affected by either of these parameters in shallow water settings but in deep settings the depth effect dominates due to the importance of depth on ree fractionation in the shells from shallow settings their lree sn to hree sn ratios l h were divided into six discrete intervals for the bathymetric sensor the bathymetric sensor was applied to some fossils and whole rock in order to estimate their paleodepths the evaluation was successful in placing the permian gyanyima the pennsylvanian naco boggy and the silurian chicotte becscie and jupiter formations in shallow depths

neoglacial change in deep water exchange and increase of sea ice transport through eastern fram strait evidence from radiogenic isotopes sediment core msm5 5 712 from the west spitsbergen continental margin has been investigated at high resolution for its seawater derived neodymium nd and lead pb isotope compositions stored in ferromanganese oxyhydroxide coatings of the sediment particles to reconstruct holocene changes in the sources and mixing of bottom waters passing the site the radiogenic isotope data are used in combination with a multitude of proxy indicators for the climatic and oceanographic development of the eastern fram strait during the past 8500 years to calibrate the downcore data seawater and core top samples from the area were analysed for their radiogenic isotope compositions core top leachates reveal relatively high more radiogenic nd isotope compositions between end 9 7 and 9 1 which are higher than present day seawater end in eastern fram strait 12 6 to 10 5 and indicate that the seawater values have only been established very recently the core top data agree well with the downcore signatures within the uppermost 40 cm of the sediment core end 9 1 to 8 8 indicating a reduced inflow of waters from the nordic seas concurrent with cool conditions and a south eastward shift of the marginal ice zone after ca 2 8 cal ka bp late holocene high sea ice abundances in eastern fram strait are coeval with the well known neoglacial trend in the northern north atlantic region in contrast warmer conditions of the late early to mid holocene were accompanied by lower less radiogenic end signatures of the bottom waters indicating an increased admixture from the nordic seas 10 6 to 10 1 a shift to significantly more radiogenic end signatures of the detrital material also occurred at 3 cal ka bp and was accompanied by a marked increase in supply of fine grained ice rafted material irf from the arctic ocean to the core site the most likely source areas for this radiogenic material are the shallow arctic shelves in particular the kara sea shelf the evolution of the pb isotope compositions of past seawater was dominated by local signatures characterized by high 208 207 206pb 204pb values during the warm early and mid holocene periods related to enhanced chemical weathering on svalbard and high glacial and riverine input derived from young granitic more radiogenic material to the west spitsbergen margin at 3 cal ka bp both detrital and seawater pb isotope data changed towards more kara sea like signatures

nd ca ratios in plankton towed and core top foraminifera confirmation of the water column acquisition of nd planktic foraminifera have been used as recorders of the neodymium nd isotopic composition of seawater although there is still controversy over the precise provenance of the nd signal we present an extensive multispecific plankton tow nd ca data set from several geographic locations se atlantic ne atlantic norwegian sea and western mediterranean together with core top samples from the mediterranean region the range of nd ca ratios in plankton towed foraminifera cleaned only of organic material from all regions 0 01 0 7 mol mol is similar to previously published analyses of sedimentary foraminifera cleaned using both oxidative and reductive steps with distribution coefficients kd ranging between 4 and 302 for the mediterranean where core top and plankton tow data are both available the range for plankton tows 0 05 0 7 mol mol is essentially identical to that for the core tops 0 1 0 5 mol mol readsorption of nd during cleaning is ruled out by the fact that the plankton tow samples underwent only an oxidative cleaning process we find a relationship between manganese mn and nd in plankton tow samples that is mirrored by a similar correlation in core top samples this relationship suggests that fe mn coatings are of negligible importance to the nd budgets of foraminifera as the nd mn ratio it implies is over an order of magnitude greater than that seen in other fe mn oxide phases rather since both plankton tows and core tops present a similar behavior the nd mn relationship must originate in the upper water column the data are consistent with the acquisition of nd and mn from the water column by binding to organic material and the fact that intratest organic material is shielded from both aggressive cleaning and diagenetic processes collectively the results help to explain two abiding puzzles about nd in sedimentary planktic foraminifera their high ree contents and the fact that they record a surface water nd isotopic signal regardless of the cleaning procedure used

accretion rate of extraterrestrial particles determined from osmium isotope systematics of pacific pelagic clay and manganese nodules abstract pelagic clay and mn nodules from domes sites in the north pacific and a varved glacial lake deposit from connecticut were analysed for os concentration and isotopic composition by isotope dilution secondary ion mass spectrometry after treatment by nis fusion or oxalic acid leaching bulk pelagic clay from domes site c has 187 os 186 os 6 5 and os 0 14 ng g oxalic acid leaches of this same sediment and of mn nodules from domes sites a and c have more radiogenic 187 os 186 os ratios which average 8 3 bulk glacial lake hitchcock sediment has 187 os 186 os 12 5 and os 0 06 ng g the total os flux to north pacific pelagic clay is 7 to 10 ng os cm2 106 y lake hitchcock sediment provides an integrated value for the local crustal 187 os 186 os ratio the oxalic acid leaches are assumed to attack hydrogenous phases selectively a simple model in which the only sources of os to the ocean are continental crust with the isotopic composition of lake hitchcock 187 os 186 os 12 5 and extraterrestrial particles with 187 os 186 os 1 1 results in a cosmic flux of osmium to the sediment of 4 9 ngos cm2 106 y of which 20 is hydrogenous a model in which the sources of os to the ocean are continental crust with an 187os 186os ratio of 30 from the model of palmer and turekian 1986 oceanic mantle or crust with 187 os 186 os 1 04 and extraterrestrial particles with 187 os 186 os 1 1 results in a cosmic flux of os to the sediment of 5 7 ngos cm2 106 y of which none is hydrogenous these extraterrestrial os fluxes correspond to maximum c 1 chondrite accretion rates of between 4 9 104 and 5 6 104 tonnes y

variations of north atlantic inflow to the central arctic ocean over the last 14 million years inferred from hafnium and neodymium isotopes the warm and saline north atlantic inflow to the arctic ocean is a major component of high northern latitude circulation and the main mechanism of deep water renewal in the arctic ocean knowledge of its past variability is critical for understanding the high latitude feedback mechanisms of the climate system here we present the first combined seawater hf and nd isotope compositions of past arctic intermediate water extracted from the authigenic fe mn oxyhydroxide fraction of two sediment cores recovered near the north pole to reconstruct changes in contributions from glacial brines of the eurasian shelf and past inflow of atlantic waters the hf and nd isotopic compositions obtained from leachates of the authigenic fraction show closely coupled and environmentally controlled variations over the past 14 million years an observed offset of these data from seawater ehf and end compositions from other ocean basins seawater array is interpreted as the result of continuously prevailing glacial weathering conditions on the high latitude eurasian continent in the late quaternary large amplitude hf and nd isotopic variations of arctic intermediate water aiw was characterized by more radiogenic isotope signatures generally prevailing under glacial conditions and less radiogenic values during interglacial periods on the basis of the close coupling between nd and hf isotopes we suggest that the evolution of hf isotope compositions of central arctic aiw has primarily been controlled by changes in ocean circulation and provenance of weathering inputs rather than changes in weathering regime

neodymium isotopic composition and concentration in the western north atlantic ocean results from the geotraces ga02 section the neodymium nd isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation the modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete here we present new observational data for nd isotopes and concentrations from twelve seawater depth profiles which follow the flow path of north atlantic deep water nadw from its formation region in the north atlantic to the northern equatorial atlantic samples were collected during two cruises constituting the northern part of the dutch geotraces transect ga02 in 2010 the results show that the different water masses in the subpolar north atlantic ocean which ultimately constitute nadw have the following nd isotope characteristics upper labrador sea water ulsw end 14 2 0 3 labrador sea water lsw end 13 7 0 9 northeast atlantic deep water neadw end 12 5 0 6 northwest atlantic bottom water nwabw end 11 8 1 4 in the subtropics where these source water masses have mixed to form nadw which is exported to the global ocean upper nadw is characterised by end values of 13 2 1 0 2sd and lower nadw exhibits values of end 12 4 0 4 2sd while both signatures overlap within error the signature for lower nadw is significantly more radiogenic than the traditionally used value for nadw end 13 5 due to the dominance of source waters from the nordic seas nwabw and neadw comparison between the concentration profiles and the corresponding nd isotope profiles with other water mass properties such as salinity silicate concentrations neutral densities and chlorofluorocarbon cfc concentration provides novel insights into the geochemical cycle of nd and reveals that different processes are necessary to account for the observed nd characteristics in the subpolar and subtropical gyres and throughout the vertical water column while our data set provides additional insights into the contribution of boundary exchange in areas of sediment resuspension the results for open ocean seawater demonstrate at an unprecedented level the suitability of nd isotopes to trace modern water masses in the strongly advecting western atlantic ocean

enhanced structural interpretation from 3d seismic data using hybrid attributes new insights into fault visualization and displacement in cretaceous formations of the scotian basin offshore nova scotia abstract meta or hybrid attributes extracted from seismic data through artificial neural networks enhance structural details in subsurface strata cretaceous units within the penobscot prospect are devoid of such interpretations although these units are plausible zones for hydrocarbon generation and accumulation the role of geologic structures responsible for such entrapment is poorly understood the present study enlightens these latter geological structures through a case study that uses 3d time migrated seismic data from the penobscot prospect in the scotian basin a modern data conditioning approach used together with multi attribute analyses and a supervised neural network have brought out the minute details of subsurface geologic structures through a hybrid attribute called the fault probability cube fpc the present fault displacement analysis reveals that the major fault of the prospect has evolved by the coalescence of different fault segments grown over space and time and has demonstrated a predominant nnw sse structural trend such a geometry has structurally modulated the cretaceous units the logan canyon the dawson canyon and the wyandot formations giving rise to different horst graben structures and fracture networks as shown by the fpc attribute this generates complicated structural deformation and accommodation space thereby enabling different trapping zones for hydrocarbon accumulation within these units such a detailed structural understanding will provide significant input to the future exploration and development programme in the penobscot prospect

plio pleistocene evolution of water mass exchange and erosional input at the atlantic arctic gateway water mass exchange between the arctic ocean and the norwegian greenland seas has played an important role for the atlantic thermohaline circulation and northern hemisphere climate we reconstruct past water mass mixing and erosional inputs from the radiogenic isotope compositions of neodymium nd lead pb and strontium sr at ocean drilling program site 911 leg 151 from 906 m water depth on yermak plateau in the fram strait over the past 5 2 myr the isotopic compositions of past bottom waters were extracted from authigenic oxyhydroxide coatings of the bulk sediments neodymium isotope signatures obtained from surface sediments agree well with present day deepwater end signature of 11 0 0 2 prior to 2 7 ma the nd and pb isotope compositions of the bottom waters only show small variations indicative of a consistent influence of atlantic waters since the major intensification of the northern hemisphere glaciation at 2 7 ma the seawater nd isotope composition has varied more pronouncedly due to changes in weathering inputs related to the waxing and waning of the ice sheets on svalbard the barents sea and the eurasian shelf due to changes in water mass exchange and due to the increasing supply of ice rafted debris ird originating from the arctic ocean the seawater pb isotope record also exhibits a higher short term variability after 2 7 ma but there is also a trend toward more radiogenic values which reflects a combination of changes in input sources and enhanced incongruent weathering inputs of pb released from freshly eroded old continental rocks

geochemical response of the mid depth northeast atlantic ocean to freshwater input during heinrich events 1 to 4 heinrich events are intervals of rapid iceberg sourced freshwater release to the high latitude north atlantic ocean that punctuate late pleistocene glacials delivery of fresh water to the main north atlantic sites of deep water formation during heinrich events may result in major disruption to the atlantic meridional overturning circulation amoc however the simple concept of an amoc shutdown in response to each freshwater input has recently been shown to be overly simplistic here we present a new multi proxy dataset spanning the last 41 000 years that resolves four heinrich events at a classic mid depth north atlantic drill site employing four independent geochemical tracers of water mass properties boron calcium carbon and oxygen isotopes in foraminiferal calcite and neodymium isotopes in multiple substrates we also report rare earth element distributions to investigate the fidelity by which neodymium isotopes record changes in water mass distribution in the northeast north atlantic our data reveal distinct geochemical signatures for each heinrich event suggesting that the sites of fresh water delivery and or rates of input played at least as important a role as the stage of the glacial cycle in which the fresh water was released at no time during the last 41 kyr was the mid depth northeast north atlantic dominantly ventilated by southern sourced water instead we document persistent ventilation by glacial north atlantic intermediate water gnaiw albeit with variable properties signifying changes in supply from multiple contributing northern sources

neodymium budget in the modern ocean and paleo oceanographic implications the oceanic nd budget is calculated using a steady state 10 box model and a compilation of field data this is the first attempt to propose consistent estimates of the nd fluxes entering the ocean as well as indicating possible nd sources and the proportion of nd fluxes exchanged between dissolved and particulate fractions with presently available nd data the best estimates give a total nd influx of 9 x 10 9 g yr which leads to an oceanic nd residence time of 500 years from modeling tests we suggest that the authigenic nd scavenged by particulates is 100 remineralized in the deep ocean the total exchanged nd flux may be as high as 2 x 10 10 g yr the epsilon nd 0 values of the influxes are 22 11 1 and 4 for the north atlantic surface atlantic north pacific and surface indo pacific regions respectively atmospheric and riverine nd fluxes are insufficient to explain the magnitude and regional variability of calculated nd influxes and epsilon nd 0 we propose continental margins as an additional source supplying nd to the ocean using the model calibrated for nd we examine the sensitivity of deep water epsilon nd 0 to variations of nd inputs to the ocean deep water nd concentrations and epsilon nd 0 vary with the changes in nd influxes and their epsilon nd 0 as nd sources to the ocean may change during glacial interglacial periods the epsilon nd 0 shifts recorded in ferromanganese nodules and crusts do not necessarily reflect changes in paleoceanic circulation the effects of continental erosion should be considered in reconstructing patterns of ocean circulation using nd isotopes

helium and neon isotopes in deep pacific ocean sediments helium and neon concentration measurements along with isotope ratio determinations have been made for particles collected in the deep pacific with a magnetic sled and they are believed to be of extraterrestrial origin analyses were made for samples consisting of composites of many extremely fine particles and for several individual particles large enough to contain sufficient gas for analysis but small enough to escape melting in their passage through the atmosphere step heating was employed to extract the gas cosmic ray spallation products or solar wind helium and neon if present were not abundant enough to account for the isotopic compositions measured in the case of the samples of magnetic fines the low temperature extractions provided elemental and isotopic ratios in the general range found for the primordial gas in carbonaceous chondrites and gas rich meteorites the isotopic ratios found in the high temperature extractions suggest the presence of solar flare helium and neon

generating a relative geologic time volume by 3d graph cut phase unwrapping method with horizon and unconformity constraints abstractconstruction of a relative geologic time rgt volume is vital to seismic geomorphological and sedimentological interpretation seismic instantaneous phase unwrapping provides an excellent approach for generating an rgt volume although several 2d or 3d seismic phase unwrapping results have been published there is a clear need for discussions on concrete methods for seismic phase unwrapping we have developed the graph cut phase unwrapping method which performs well in the interferometric synthetic aperture radar image processing it has advantages of strong discontinuity preserving ability and high computing efficiency to make it suitable for 3d seismic phase unwrapping the method is improved by extending it from 2d to 3d and by introducing the seismic horizon and unconformity constraints the strong and continuous conformable seismic events which can be easily tracked by certain autopicking methods are introduced as horizon constraints for guiding the phase unwrapping to ensure a constant

temporal stability of the neodymium isotope signature of the holocene to glacial north atlantic the neodymium isotopic composition of marine precipitates is increasingly recognized as a powerful tool for identifying changes in ocean circulation and mixing on million year to millennial timescales unlike nutrient proxies such as 13 c or cd ca nd isotopes are not thought to be altered in any significant way by biological processes and thus they can serve as a quasi conservative water mass tracer however the application of nd isotopes in understanding the role of thermohaline circulation in rapid climate change is currently hindered by the lack of direct constraints on the signature of the north atlantic end member through time here we present the first results of nd isotopes measured in u th dated deep sea corals from the new england seamounts in the northwest atlantic ocean our data are consistent with the conclusion that the nd isotopic composition of north atlantic deep and intermediate water has remained nearly constant through the last glacial cycle the results address long standing concerns that there may have been significant changes in the nd isotopic composition of the north atlantic end member during this interval and substantiate the applicability of this novel tracer on millennial timescales for paleoceanography research

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

a texture based region growing algorithm for volume extraction in seismic data we present a novel approach to automated volume extraction in seismic data and apply it to the detection of allochthonous salt bodies using a genetic algorithm we determine the optimal size of volume elements that statistically according to the u test best characterize the contrast between the textures inside and outside of the salt bodies through a principal component analysis approach this information was used to implement a seeded region growing algorithm to directly extract the bodies from the cube of seismic amplitudes we present the resulting three dimensional bodies and compare our final results to those of an interpreter showing encouraging results

neodymium isotopic composition and rare earth element concentrations in the deep and intermediate nordic seas constraints on the iceland scotland overflow water signature neodymium isotopic composition and rare earth element concentrations were measured in seawater samples from eleven stations in the nordic seas these data allow us to study how the iceland scotland overflow water isow acquires its neodymium signature in the modern ocean the waters overflowing the faroe shetland channel are characterized by nd 8 2 0 6 in good agreement with the only other data point published 19 years ago in the greenland and iceland seas the water masses leading to the formation of the isow display lower neodymium isotopic composition with nd around 11 and 9 respectively since no water masses in the nordic seas are characterized by nd 8 the radiogenic signature of the isow likely reflects inputs from the highly radiogenic norwegian basin basaltic margins jan mayen iceland faroe with nd 7 in addition to the neodymium isotopic composition the rare earth element patterns suggest that these inputs occur via the remobilization which includes resuspension and dissolution of sediments deposited on the margins whereas the neodymium isotopic composition behaves conservatively in the oceans in the absence of lithogenic inputs and can be used as a water mass tracer these results emphasize the role of interactions between sediments deposited on margins and seawater in the acquisition of the neodymium isotopic composition of water masses these results should allow a better use of this parameter to trace the present and the past circulation in the north atlantic

tracing papua new guinea imprint on the central equatorial pacific ocean using neodymium isotopic compositions and rare earth element patterns abstract the nd isotopic composition ic and rare earth patterns of hydrodynamic structures of the equatorial pacific ocean were characterized along 140 w the nd ic of antarctic intermediate water aaiw and of the lower layer of the equatorial undercurrent euc at 140 w 13 c water are much more radiogenic at the equator than at their origin in the south equatorial current 12 s revealing that these water masses have been in contact with the highly radiogenic papua new guinea png slope in both cases only a small fraction less than 9 of the sediment deposited on the png slope is required to be exchanged or dissolved to explain these nd ic variations whereas the hydrographic properties of the same water masses remain unchanged this confirms the usefulness of this tracer to identify pathways of water masses these results emphasize the importance of jets in transporting lithogenic material into the subsurface layers of remote areas where aeolian inputs are particularly weak and corroborate the previous results on fe and al maximum in this area m l wells g k vallis e a silver nature 398 1999 601 604 the nd ic of the upper layer of the euc contrasts strongly to that of the subpycnocline layer indicating that the equatorial upwelling only affects the surface waters and is not effective between 120 and 150 m we calculate that the nd imprint of the png input is likely to vanish from this surface layer as it traverses the basin due to the replacement of upwelled waters by non radiogenic ones

extracting foraminiferal seawater nd isotope signatures from bulk deep sea sediment by chemical leaching the seawater radiogenic neodymium 143nd 144nd isotope signature is an invaluable tool for the reconstruction of past deep water provenance sedimentary foraminifera or fish teeth are among the most reliable archives known for nd isotope based reconstructions of past seawater as the distribution and preservation of these archives are limited the extraction of hydrogenetic ferromanganese oxyhydroxides from bulk sediments provide an easily applicable alternative this method however implies the risk of generating artefacts due to the possible release of non seawater derived nd during the extraction procedure here we revisit and further investigate the reliability of the extraction of seawater derived nd isotope signatures via leaching of bulk deep sea sediments with two commonly used buffered acetic acid and acid reductive mix solutions repeated application of such stepwise leaching procedures to different non decarbonated sediments from distinct settings across the deep atlantic ocean shows pronounced elemental and nd isotope trends during the leaching process in the laboratory our results show that seawater nd isotope compositions are extracted together with carbonates and manganese oxides only at the beginning of the leaching series during chemical extraction the carbonates effectively work as a buffer preventing acid induced mobilisation of fe oxides and volcanogenic material once this buffer is consumed potentially present volcanogenic phases are considerably attacked leading to shifts in the extracted nd isotope signal of up to 12 epsilon units such volcanogenic phases are a significant source of contaminant nd reflected by markedly elevated al nd signatures we consequently propose a revised weak leaching protocol for carbonate bearing deep sea sediments which is simple to use provides excellent agreement with data obtained from uncleaned foraminifera and can be easily screened for contamination

the origin of norwegian sea deep water a nearly homogeneous water mass the norwegian sea deep water is found below 2000 m depth in the norwegian and lofoten basins of the norwegian sea recent observations indicate that this water is a mixture of relatively cold and fresh greenland sea deep water with warmer saltier eurasian basin deep water from the arctic ocean we have found this mixture along the western and southern periphery of the greenland sea near the level where the pressure compensated densities of the parent water masses are equal the along isopycnal mixing produces a remarkably uniform water mass which can be traced only a short distance away from its entry into the norwegian sea through gaps in the mid ocean ridge north of jan mayen island direct measurements of flow through these gaps confirm motion in the proper sense to accomplish this connection

size distribution of siderophile element concentrations in black magnetic spherules from deep sea sediments a size spectrum of black magnetic spherules which were collected from deep sea sediments was obtained siderophile element fe co ir and au concentrations in 100 spherules each of them larger than 100 m were determined with instrumental neutron activation analysis about 20 of the spherules showed ir fe and co fe ratios which cannot be explained clearly by an iron meteorite parent for the spherules further there was no strong correlation between the size and the chemical concentration ratios ir fe co fe and au fe of the spherules

ocean circulation and freshwater pathways in the arctic mediterranean based on a combined nd isotope ree and oxygen isotope section across fram strait the water masses passing the fram strait are mainly responsible for the exchange of heat and freshwater between the nordic seas and the arctic ocean the arctic mediterranean am disentangling their exact sources distribution and mixing however is complex this work provides new insights based on a detailed geochemical tracer inventory including dissolved nd isotope end rare earth element ree and stable oxygen isotope 18o data along a full water depth section across fram strait we find that nd isotope and ree distributions in the open am primarily reflect lateral advection of water masses and their mixing seawater particle interactions exert important control only above the shelf regions as observed above the ne greenland shelf advection of northward flowing warm atlantic water aw is clearly reflected by an end signature of 11 7 and a nd concentration nd of 16 pmol kg in the upper 500 m of the eastern and central fram strait freshening and cooling of the aw on its way trough the am are accompanied by a continuous change towards more radiogenic end signatures e g 10 4 of dense arctic atlantic water this mainly reflects mixing with intermediate waters but also admixture of dense kara sea waters and pacific derived waters the more radiogenic end signatures of the intermediate and deep waters reaching 9 5 are mainly acquired in the sw nordic seas through exchange with basaltic formations of iceland and se greenland inputs of nd from svalbard are not observed and surface waters and nd on the svalbard shelf originate from the barents sea shallow southward flowing arctic derived waters 200 m form the core of the east greenland current above the greenland slope and can be traced by their relatively radiogenic end reaching 8 8 and elevated nd 21 to 29 pmol kg these properties are used together with 18o and standard hydrographic tracers to define the proportions of pacific derived 30 based on nd isotopes and atlantic derived waters as well as of river waters 8 shallow waters 150 m on the ne greenland shelf share some characteristics of arctic derived waters but exhibit less radiogenic end values reaching 12 4 and higher nd up to 38 pmol kg in the upper 100 m this suggests local addition of greenland freshwater of up to 6 in addition to these observations this study shows that the pronounced gradients in end signatures and ree characteristics in the upper water column provide a reliable basis for assessments of shallow hydrological changes within the am

3 d seismic discontinuity for faults and stratigraphic features the coherence cube seismic data are usually acquired and processed for imaging reflections this paper describes a method of processing seismic data for imaging discontinuities e g faults and stratigraphic features one application of this nontraditional process is a 3 d volume or cube of coherence coefficients within which faults are revealed as numerically separated surfaces figure 1 compares a traditional 3 d reflection amplitude time slice with the results of the new method to our knowledge this is the first published method of revealing fault surfaces within a 3 d volume for which no fault reflections have been recorded

a workflow to skeletonize faults and stratigraphic features abstractimproving the accuracy and completeness of subtle discontinuities in noisy seismic data is useful for mapping faults fractures unconformities and stratigraphic edges we have developed a workflow to improve the quality of coherence attributes first we apply principal component structure oriented filtering to reject random noise and sharpen the lateral edges of seismic amplitude data next we compute eigenstructure coherence which highlights the stratigraphic and structural discontinuities we apply a laplacian of a gaussian filter to the coherence attribute that sharpens the steeply dipping faults attenuates the stratigraphic features parallel to the seismic reflectors and skeletonizes the unconformity features subparallel to the reflectors finally we skeletonize the filtered coherence attribute along with the fault plane the filtered and skeletonized seismic coherence attribute highlights the geologic discontinuities more clearly and precisely these discontinuous features can be colo

recirculating components to the deep boundary current of the northern north atlantic abstract the meridional overturning system of the north atlantic is conventionally thought of as transporting warm water 4 c to high latitudes and covd water to low latitudes the northern cold water sources for this system are dense overflow from the nordic seas and less dense water from the labrador sea lsw the overflow components are carried westward by a deep northern boundary current dnbc that is shown here actually to begin southeast of the overflow regions the dnbc lies along the southern side of a system of islands and submarine ridges that divides the nordic seas from the subpolar basins the overflows act to increase the transport of the dnbc and this transport is further increased through the entrainment of warm waters once inside the labrador sea the dnbc is joined by lsw before continuing south to low latitudes as a cold deep western boundary current dwbc however published transport estimates are larger than can be explained by warm water entrainment alone thus indicating entrainment also of recirculating cold components the subject of this paper their sources are shown to be the lsw and cold abyssal waters originating from the southern hemisphere the lsw is entrained downward into the denser part of the dnbc and laterally into the upper part of the dwbc whereas the cold abyssal waters are supplied by an eastern intensified northward flow in the eastern atlantic that serves as the initial source of the dnbc and by a similar northward flow in the western atlantic the meridional overturning system described includes recirculations and poleward transport of cold water in addition tothe components described by the conventional system the cold abyssal waters in both the eastern and western basins have relatively low levels of oxygen and high concentrations of silicate reflecting their southern origin but their influence in the northwestern atlantic is somewhat obscurred by strong recirculating cyclonic gyres in the newfoundland and labrador basins this influence is detected by a deep silicate maximum extending poleward from the mid latitude western atlantic through the two gyres with eastern concentration and recirculating back diluted toward the south in the dwbc within the respective basins such a maximum also extends northward through the irminger basin into the dnbc but there is an ambiguity as to whether this is a direct extension of the signal from the south in the western basin or if it comes from the mid latitude eastern basin by way of westward flow through the charlie gibbs fracture zone it is perhaps consequence of both estimates of the volume transports of the various recirculating cold components indicate that they supply about as much water to the deep boundary currents as do the combined cold water sources in the north

the neodymium isotopic composition of waters masses in the eastern pacific sector of the southern ocean the antarctic circumpolar current is one of the key components of ocean circulation and a knowledge of its isotopic composition is essential to the use of neodymium nd isotopes to trace circulation now and in the past here we present 57 new analyses of the nd isotopic composition of the water column in the eastern pacific sector of the southern ocean documenting both the variation in three dimensions as well as the controls on that variability nd isotopic data for the middle of the water column demonstrate the homogeneity of circumpolar deep water cdw at an end value of 8 7 0 1 this homogeneity reflects the large nd inventory in the acc flow and the degree to which this large inventory buffers the nd characteristics of the acc against extra oceanic inputs from the continents either via dust from the atmosphere or through dissolved and particulate material from the adjacent continents cdw upwells onto the amundsen sea shelf and even here its nd isotopic properties are close to conserved in the middle of the water column end 8 0 0 2 at 600 m at the top and bottom of the shelf water column however the nd isotopic and concentration characteristics are strongly modified to end as high as 4 5 all the shelf water column data obtained here are consistent with net addition of nd to bottom and surface waters with a contrasting isotopic composition that is matched by local sediment end 1 to 2 followed by conservative mixing of that water into intermediate levels mixing with this shelf composition also leads to significant modification of open ocean surface water nd isotopic shift around 1 epsilon unit in the acc as it flows eastwards modification of open ocean bottom waters by interaction with sediment is more subtle but there is marked non conservative removal of nd accompanied by significant changes in isotopic composition in waters within 10 m of the seabed the new data demonstrate the conservativity of nd in the middle water column especially for such large volume flows as the acc though boundary exchange type processes are clearly important in this region and their imprint on both the shelf and open ocean surface water is significant there is no observable impact on the main core of cdw this finding augurs well for the use of nd isotopes as a conservative water mass tracer now and in the past for example these data suggest that the only likely control on the temporal variability of southern component deep water exported northwards into the atlantic through the last glacial cycle is variations in the input of north atlantic deep water in the atlantic sector on the other hand the data also suggest caution in the use of sedimentary archives of bottom water nd as records of deep water nd isotopic characteristics given the dramatic modification of bottom waters on the shelf and the more subtly non conservative behaviour in the open ocean bottom water that are both suggestive of modification of the nd characteristics of bottom waters by sediment

neodymium isotopic characterization of ross sea bottom water and its advection through the southern south pacific since the inception of the international geotraces program studies investigating the distribution of trace elements and their isotopes in the global ocean have significantly increased in spite of this large scale effort the distribution of neodymium isotopes 143nd 144nd end and concentrations nd in the high latitude south pacific is still understudied specifically north of the antarctic polar front apf here we report dissolved nd isotopes and concentrations from 11 vertical water column profiles from the south pacific between south america and new zealand and across the antarctic frontal system results confirm that ross sea bottom water rsbw is represented by an endvalue of 7 and for the first time show that these nd characteristics can be traced into the southeast pacific until progressive mixing with ambient lower circumpolar deep water lcdw dilutes this signal north of the apf that is endbehaves conservatively in rsbw opening a path for studies of past rsbw behavior neodymium concentrations show low surface concentrations and a linear increase with depth north of the apf south of the apf surface nd is high and increases with depth but remains almost constant below 1000m this vertical and spatial nd pattern follows the southward shoaling density surfaces of the southern ocean and hence suggests supply of nd to the upper ocean through upwelling of nd rich deep water low particle abundance due to reduced opal production and seasonal sea ice cover likely contributes to the maintenance of the high upper ocean nd south of the apf this suggests a dominant lateral transport component on nd and a reduced vertical control on nd concentrations in the south pacific south of the apf

subpolar mode water formation traced by neodymium isotopic composition 1 the formation of subpolar mode water spmw is documented by combining neodymium isotopic composition nd ic as a conservative tracer with salinity temperature and o2 concentration nd ic reveals a more pronounced eastward extension of the labrador current particularly its subarctic intermediate water component than the other parameters nd ic also suggests that waters flowing through the denmark strait do not significantly contribute to the spmw formation a two end member mixing involving subarctic intermediate water and maybe ultimately labrador current water and north atlantic central water is proposed to explain spmw formation these results provide important insight into the processes controlling the nd ic in the north atlantic subpolar gyre which could provide a means for reconstructing the northward extension of the gulf stream in the past

on the relationship between nd isotopic composition and ocean overturning circulation in idealized freshwater discharge events using a cost efficient climate model the effect of changes in overturning circulation on neodymium isotopic composition nd is systematically examined for the first time idealized sequences of abrupt climate changes are induced by the application of periodic freshwater fluxes to the north atlantic na and the southern ocean so thus mainly affecting either the formation of north atlantic deep water nadw or antarctic bottom water aabw variations in nd reflect weakening and strengthening of the formation of nadw and aabw changes in ndof end members are relatively small relationships between nd and the strength of nadw or aabw are more pronounced for aabw than for nadw atlantic patterns of variations in nd systematically differ between na and so experiments additionally the signature of changes in nd in the atlantic and the pacific is alike in na but opposite in so experiments discrimination between na and so experiments is therefore possible based on the atlantic pattern of variations in nd and the contrariwise behavior of nd in the atlantic and the pacific in further experiments we examined the effect of variations in magnitudes of particle export fluxes within the examined range and although settling particles represent the only sink of nd their effects on nd are relatively small our results confirm the large potential of nd as a paleocirculation tracer but also indicate its limitations of quantitative reconstructions of changes in the atlantic meridional ocean circulation

fingerprinting northeast atlantic water masses using neodymium isotopes dissolved neodymium nd isotopic composition expressed as end has been analysed for 82 seawater samples collected from 13 stations stretching from the alboran sea to the iceland basin the distribution of the end values of water masses was thus investigated for the first time along the western european margin in order to explore whether the water masses flowing in the eastern subpolar and subtropical atlantic reveal distinct isotopic patterns the modified atlantic water maw in the alboran sea displays end values between 9 2 0 2 and 8 9 0 2 that are significantly more radiogenic than those reported in previous studies 10 8 0 2 to 9 7 0 2 suggesting temporal variations in the nd isotopic composition of the water that enters the mediterranean sea from the strait of gibraltar the end value of the underlying modified winter intermediate water wiw has been established for the first time 9 8 0 3 and is compatible with a nd signature acquired from the sinking of maw in the northwestern mediterranean sea within the gulf of cadiz southern mediterranean sea water msw 10 6 0 2 differs slightly from the northern msw 9 9 0 4 owing to a significant contribution of modified east antarctic intermediate water eaaiw 10 9 0 2 in the northeast atlantic the north atlantic current surface water located in the inter gyre region north of 46 n displays end values of between 14 0 0 3 and 15 1 0 3 reflecting the subpolar gyre signature along the western european margin end values of surface water decrease toward the north from 10 4 1 6 to 13 7 1 0 in agreement with the gradual mixing between subtropical and subpolar water at intermediate depth end values decrease from 9 9 0 4 within the gulf of cadiz to 12 1 0 3 within the porcupine seabight indicating a strong dilution of the msw with subpolar water within the rockall trough and the iceland basin the more negative end values at mid depth 13 5 0 3 indicate that the msw has no influence even during periods of low nao index water masses deeper than 1200 m in the northeast atlantic are clearly influenced by the less radiogenic labrador sea water lsw 13 2 0 3 and 14 5 0 3 that mixes locally end between 10 3 0 2 and 11 3 0 3 in the iceland basin with the iceland scotland overflow water isow

the potential of sedimentary foraminiferal rare earth element patterns to trace water masses in the past dissolved rare earth element ree concentration data from intermediate and deep seawater form an array characterized by higher middle ree enrichments mree mree in the north atlantic and a progressive increase in heavy to light ree ratios hree lree as water masses age the rees in foraminifera are fractionated towards higher mree mree and lower hree lree relative to seawater calculations based on a scavenging model show that the ree patterns in uncleaned core top foraminifera resemble those adsorbed onto calcite particulate organic material and hydrous ferric oxides but the full extent of the ree fractionation measured in foraminifera was not reproduced by the model however differences in the hree lree mree mree ratios and the cerium anomaly between ocean basins are preserved and are in agreement with the seawater ree distribution under oxic conditions the hree lree and mree mree compositions of uncleaned foraminifera at the sediment seawater boundary are preserved during burial but the cerium anomaly is sensitive to burial depth in suboxic sedimentary environments all uncleaned foraminiferal ree concentrations are elevated relative to core top values indicating addition of rees from pore waters the hree lree ratio is highest when sedimentation rates were greatest lippold et al 2009 and when high fe ca ratios in the uncleaned foraminifera indicate that fe was mobile in sediments that have not experienced suboxic conditions during burial uncleaned foraminifera preserve the seawater signal taken up at the sediment seawater interface and are therefore suggested to be a suitable archive of changes in the ree signal of past bottom waters this article is protected by copyright all rights reserved

magnetic spherules from recent fluvial sediments in alberta canada characteristics and possible origins magnetic spherules were recently recovered in recent fluvial sediments in alberta canada and have been studied using x ray diffraction electron microprobe scanning electron microscope and neutron activation analysis results show that these spherules are composed of magnetite wustite and hematite some of them contain iron metal cores the similarities in morphology mineralogy and internal structure of these spherules to spherules of extraterrestrial origin found in other environments suggest that some of these spherules from alberta might also be of extraterrestrial origin in spite of their unusual compositions

the concentration and isotopic composition of diffusible nd in fresh and marine waters abstract variations in the nd isotopic composition of ocean water through time recorded in marine deposits are suggested to document changes in erosional input and ocean circulation thus characterization of the dissolved nd component in seawater is important but few attempts have been made to directly measure truly dissolved nd here we report nd data obtained using the technique of diffusive gradients in thin films dgt designed to measure in situ diffusible labile trace metals in aqueous solutions the method samples free ions and possibly very small complexes the concentration and isotopic composition of nd in fresh brackish and seawater have been determined with dgt analyzed with thermal ionization mass spectrometry and compared with filtered and bulk water samples concentrations measured in water samples and with dgt show that the relative amount of diffusible nd increases with salinity from being about 10 in the fresh water to 42 in seawater at each sampled site the isotopic composition of nd in the water shows a similar isotopic composition within errors with nd sampled using the dgt method these results indicate that there is a complete exchange between the particulate colloidal fraction and the truly dissolved phase therefore our findings suggest that solute nd reflects both the isotopic composition of the marine sediments and the bulk water

pb isotopes and geochemical monitoring of arctic sedimentary supplies and water mass export through fram strait since the last glacial maximum 1 elemental and pb isotope measurements were performed on leachates and residues from surface sediments and two 50 cm cores mc04 and mc16 collected along a ne sw transect through fram strait geochemical and isotopic properties of residues from surface sediments define three distinct spatial domains within the strait 1 the easternmost edge of the strait 2 the eastern part of the strait off the svalbard margins and 3 the western part of the strait influenced by supplies from svalbard the nordic seas with possible contributions from northwestern siberian margins and sea ice and water outflow from the arctic respectively core mc16 in the third domain beneath the outflowing arctic waters spans the last glacial maximum present interval sediments from this core were leached to obtain detrital residues and exchangeable leachates fractions detrital supplies to core mc16 are believed to originate mainly from melting of the overlying sea ice and thus can be used to document changes in arctic sedimentary sources detrital 206pb 204pb and 208pb 206pb ratios illustrate two mixing trends trends a and b corresponding to the pre and post younger dryas yd intervals respectively these trends represent binary mixtures with a common end member canadian margins and either a siberian trend a or greenland trend b margin end member the yd is marked by an isotopic excursion toward the canadian end member suggesting a very active beaufort gyre possibly triggered by massive drainage of the laurentide ice sheet pb isotope compositions of leachates thought to represent the signature of the overlying water masses define a unique linear trend coincident with trend a this suggests that water masses acquired their signature through exchange with particulate fluxes along the canadian and siberian continental margins

modeling the neodymium isotopic composition with a global ocean circulation model abstract for the first time modeling of the neodymium nd isotopic composition expressed as end is performed in an ocean global circulation model opa orca2 0 model in the interest of simplicity nd concentration is not explicitly included and end is modeled as a passive tracer recent studies suggest that dissolved particulate exchanges between continental margin sediments and seawater termed boundary exchange be could be the dominant source sink terms that determine the distribution of neodymium isotopes in the global ocean to test this hypothesis we only included this be source sink term in the model be was parameterized as a relaxing term that forces end of seawater to the isotopic composition of the continental margin over a characteristic exchange time sensitivity tests were made using different exchange times and parameterizations the model reproduces most of the general trends of end composition in seawater at global scale inter basin gradient composition of some of the main water masses these results suggest that be process may account for the major sources and sinks of oceanic nd while indicating that the characteristic time of interaction between seawater and margins varies from about half a year in surface waters to several years at depth the disparities between the model and observations might reflect the typical shortcomings of utilizing a coarse resolution ocean model circulation fields or neglected sources of neodymium such as dissolution of aeolian inputs or dissolved river loads

delineation of tectonic features offshore trinidad using 3 d seismic coherence seismic coherence allows interpreters to quickly visualize and map complex fault systems calibration to well control adds the ability to recognize important stratigraphic features and potential gas water contacts applying coherence technology to an offshore trinidad 3 d survey reduced exploration cycle time and improved understanding of tectonic elements in the area the following shows some ways in which coherence may be used to identify complex fault systems and speed up interpretation

use of a computational fault extraction process with calibrations to characterize a fractured basement reservoir yufutsu japan the yufutsu oil and gas field located in hokkaido northern japan produces hydrocarbon from a typical fracture type reservoir composed of very tight cretaceous granitic basement and overlying conglomerate of the eocene here delineations of faults accompanying large open fractures are essential for optimal developments to capture fault distribution objectively various seismic attribute estimates ascribed to fault distributions are derived from three dimensional seismic data by computational procedures however to use the estimates properly calibrating them with independent observations other than seismic data is important we present a calibration scheme by coupling seismic data with microseismic data and in situ stress data to delineate active faults under a strike slip faulting stress regime in the yufutsu field active faults are interpreted to be fluid pathways formed by shear dilation in the calibration two kinds of parameter sets are tuned one controls linkages of fault responses fragmented by artificial noises caused by seismic acquisition and processing to adjust spatial continuities of fault surfaces properly another limits extracted fault strikes with respect to mohr coulomb failure criterion to highlight active faults the calibrated seismic attribute estimates show a qualitative consistency with the microseismic hypocenter distribution observed during a massive hydraulic stimulation in addition a large difference in gas productivity observed at four wells from very high productivity to no gas flowing is clearly related to an existence of distinct lineation with strong magnitudes of the calibrated seismic attributes it suggests that the calibrated estimate becomes a criterion to judge an economic viability of a well

nd and pb isotope signatures of the clay size fraction of labrador sea sediments during the holocene implications for the inception of the modern deep circulation pattern holocene on the basis of sediment supply variations for the last 12 kyr three sources have contributed to the sediment mixture the north american shield the pan african and variscan crusts and the mid atlantic ridge clay isotope signatures indicate two mixtures of sediment sources the first mixture 12 2 6 5 ka is composed of material derived from the north american shield and from a young crustal source from 6 5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the midatlantic ridge since the significant decrease in proximal deglacial supplies the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the western boundary undercurrent over the past 8 4 kyr the progressive intensification of the western boundary undercurrent was initially associated mainly with the transport of the northeast atlantic deep water mass until 6 5 ka and with the denmark strait overflow water thereafter the establishment of the modern circulation at 3 ka suggests a reduced influence of the denmark strait overflow water synchronous with the full appearance of the labrador seawater mass our isotopic data set emphasizes several changes in the relative contribution of the two major components of north atlantic deep water throughout the holocene index terms 4267 oceanography general paleoceanography 4558 oceanography physical sediment transport 1040 geochemistry isotopic composition chemistry 9325 information related to geographic region atlantic ocean 9604 information related to geologic time cenozoic keywords clay size fraction sedimentary mixings deep circulation nd and pb isotopes north atlantic labrador sea

rare earth element transport in the western north atlantic inferred from nd isotopic observations the isotopic composition of nd in the water column from several western north atlantic sites and formational areas for north atlantic deep water shows extensive vertical structure at all locations in regions where a thermocline is well developed large isotopic shifts 2 to 3 units are observed across the base of the thermocline regions without a thermocline are characterized by much more gradual shifts in isotopic composition with depth in general the data reveal an excellent correlation between the nd isotopic distribution in the western north atlantic water column and the distribution of water masses identified from temperature and salinity characteristics nadw as identified from t s properties is also characterized by a well defined isotopic composition having nd 0 13 5 0 5 this signature is associated with waters identified as nadw from high latitudes near formational areas in the labrador sea down to the equatorial region the isotopic signature of nadw would appear to be formed by a blend of more negative waters originating in the labrador sea nd 0 18 and more positive waters originating in the overflows from the norwegian and greenland seas nd 0 8 to 10 and is consistent with classical theories on the formation of nadw the isotopic signature of nadw is propagated southward to the equator where it is gradually being thinned out by mixing from above and below with more radiogenic nd associated with northward spreading antarctic intermediate and bottom waters the preservation of the isotopic signature of nadw over these large distances indicate that the ree undergo extensive lateral transport the isotopic composition of nd is largely conservative over the time scales of mixing within the atlantic in spite of the intrinsic nonconservative behavior of neodymium nd concentration gradients generally show surface waters to be depleted in nd relative to deep waters which must require vertical transport processes however isotopic differences in the water column preclude the local downward transport of ree from the surface into underlying deep waters as a simple explanation of the concentration gradient the apparent decoupling of ree in nadw from overlying local surface waters and the increasing concentration with depth provide a conflict with simple vertical transport mechanisms that is not yet resolved

measurement of53mn in deep sea iron and stony spherules abstract cosmic ray produced 53 mn t 1 2 3 7 10 6 years was measured in individual and groups of deep sea iron and stony spherules by highly sensitive neutron activation analysis the activities found were less than 20 dpm 53 mn kg fe 10 5 10 6 dpm 53 mn sample in iron spherules except one iron spherule whose activity was 241 73 dpm 53 mn kg fe these low activities may indicate evaporative loss of 53 mn due to heating in the earth s atmosphere on the other hand all stony spherules contained 200 260 dpm 53 mn kg fe which is similar to chondritic values these spherules may be ablation debris from large objects