late glacial to holocene planktic foraminifera bioevents and climatic record in the south adriatic sea quantitative analyses of planktic foraminifera sea surface temperatures ssts oxygen isotope and radiocarbon dating from a deep sea core recovered in the south adriatic sea have been used to reconstruct a subcentennial climatic and biochronological record since the late glacial the last 24 cal ka bp the identification and relative abundance of 25 species of planktic foraminifera along the core have provided a continuous record of the faunal changes over this time interval these results have permitted the establishment of 10 biozones in the south adriatic sea based on the appearance and or disappearance of the main specific taxa from peaks of abundance and or by modification in marine conditions the robust chronology of the south adriatic core allowed correlation of sst estimates to the gisp2 ice core record indicating that the main climate changes recorded in greenland ice cores over the last 24 ka are recorded and globally synchronous with those observed in the south adriatic sea this finding further allows comparison of the planktic foraminifera record with the event stratigraphic scheme proposed by the intimate group in order to better identify the relationship between past climatic changes and the response of microfaunal assemblages in the south adriatic copyright 2010 john wiley sons ltd

globorotalia truncatulinoides growth and chemistry as probes of the past thermocline 1 shell size this work identifies features of the life history of the deep living planktonic foraminifer globorotalia truncatulinoides that offer possibilities for reconstructing characteristics of the past ocean s main thermocline part 1 considers two aspects of variation in shell size the predictability of growth related size changes which we need to calculate changes in shell chemistry and a model for environmentally forced changes in shell size frequency which suggests how shell size may be a direct source of paleoceanographic information even though size variation among shells of g truncatulinoides at the same stage of growth same number of chambers exceeds the size difference between successive growth stages growth related size changes are predictable because shells tend to grow at the same rate variation in initial shell size is sufficient to account for the large size variation found among shells at the same stage of growth several lines of evidence suggest that g truncatulinoides reproduces at 600 m in the water column and it appears that vertical mixing to that depth is required to return juvenile shells to the surface anything that prevents this such as shallowing of the thermocline can interfere with g truncatulinoides life history in such a way that its shell size frequency distributions are altered among shells falling to the seafloor from a reproducing population are large numbers of both juvenile and adult sizes and if reproduction is inhibited the frequencies of those sizes are reduced and the relative frequency of intermediate sized shells increases a paleoceanographically useful result of this is that the topography of the main thermocline tends to be reflected in the size frequency distribution of g truncatulinoides shells from the underlying sediments in areas where the top of the main thermocline is shallower than 600 m production of juveniles 125 177 m and reproductive adults 425 m is reduced leaving predominantly intermediate sized 212 355 m shells

geochemical and petrographical characterization of fine grained carbonate particles along proximal to distal transects the origin of carbonate ooze particles is often poorly understood this is due to their polygenic origin and potential post depositional alteration here the outcome of a physical separation study with regard to different component classes of micritic carbonates is shown the focus is on grain size and morphology mineralogy and isotope signatures two contrasting proximal to distal transects were investigated 1 the miocene leeward margin of great bahama bank odp leg 166 and 2 the transition between the maiella platform and the umbria marche basin in central italy near the cenomanian turonian boundary in both case settings carbonate particles of biogenic origin include at least three groups of organisms i planktonic foraminifera ii calcareous nannofossils and iii fragments of unspecified neritic skeletal material two further particle types lack diagnostic structures and based on particle size and mineralogy are here referred to as iv macroparticles 5 20 m mainly xenomorphic and v microparticles 12 m mainly automorphic to sub automorphic macro and microparticles represent 50 to 80 of the carbonate phase in slope and toe of slope domains and share characteristic carbon and oxygen isotope signatures macro and microparticles are considered shallow water precipitation products subsequently exported into the slope and toe of slope domains macroparticles are probably related to the fragmentation of neritic skeletal components while microparticles point to inorganic and or bioinduced precipitation in the water column in some cases macro and microparticles may have an early diagenetic origin the identification of the origin of fine grained particles allows for a quantitative assessment of exported in situ and diagenetic carbonate materials in periplatform environments the data shown here represent an important step towards a more complete characterization of carbonate ooze and micrite

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

field examination of the oceanic carbonate ion effect on stable isotopes in planktonic foraminifera we determined the 18o and 13c of individual globigerinoides ruber and pulleniatina obliquiloculata from sediment traps located from 5 n to 12 s along 140 w in the pacific ocean to evaluate the effects of varying co3 on shell 18o and 13c variations in the offset between shell 13c and 13cdic 13cs dic are attributed to differences in co3 temperature and shell size between sample sites when 13cs dic of g ruber was corrected for variations in co3 using the experimental slope of bijma et al 1998 the residual 13cs dic was correlated with mixed layer temperature 0 10 0 04 c 1 the slope of this temperature effect is consistent with experimental results in p obliquiloculata 13cs dic and temperature were strongly anticorrelated 0 14 0 03 c 1 we are unable to separate the influences of co3 and temperature in this species without independent experimental data correcting for co3 variability on 18os of g ruber improves the accuracy of estimated sea surface temperatures

reconstructing past planktic foraminiferal habitats using stable isotope data a case history for mediterranean sapropel s5 abstract a high resolution stable o and c isotope study is undertaken on all planktic foraminiferal species that are reasonably continuous through an eemian sapropel s5 from the western side of the eastern mediterranean the data are considered within a context of high resolution isotope records for two further s5 sapropels from the central and easternmost sectors of the basin alkenone based sea surface temperature records for all three sapropels and planktic foraminiferal abundance records for the same sample sets through all three sapropels results are compared with similar data for holocene sapropel s1 the adopted approach allows distinction between species that are most suitable to assess overall changes in the climatic hydrographic state of the basin including depth related differentiations and the main seasonal developments and species that are most affected by variable biological controls or local regional and transient physico chemical forcings it is found that a priori assumptions about certain species palaeohabitats based on modern habitat observations may become biased when non analogue conditions develop in the case of mediterranean sapropel s5 these consisted of enhanced freshwater dilution elevated productivity shoaling of the pycnocline between intermediate and surface waters and stagnation of the subsurface circulation under these conditions some species are found to shift into habitat settings that differ considerably from those occupied today the present multiple species approach can identify such anomalous responses and thus offers a sound background for further shell chemistry investigations and quantitative interpretation of the isotopic profiles we capitalise on the latter potential and offer the first quantitative estimates of monsoon flooding into the mediterranean during the deposition of eemian sapropel s5

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

ventilation of the subtropical north pacific the shallow salinity minimum abstract the shallow salinity minimum of the subtropical north pacific is shown to be a feature of the ventilated wind driven circulation subduction of low salinity surface water in the northeastern subtropical gyre beneath higher salinity water to the south causes the salinity minimum variation of salinity along surface isopycnals causes variations in density and salinity at the minimum a model of ventilated flow is used to demonstrate how the shallow salinity minimum can arise the model is modified to account for nonzonal realistic winds it is also extended to examine the three dimensional structure of the western shadow zone the boundary between the subtropical and subpolar gyres is given by the zero of the zonal integral of ekman pumping the western shadow zone fills the subtropical gyre at the base of the ventilated layers and decreases in extent with decreasing density for parameters appropriate to the north pacific the eastern shadow zone is of very limited extent observations of salini

microstructural and geochemical perspectives on planktic foraminiferal preservation glassy versus frosty in recent years it has become apparent that the cool tropic paradox of paleogene and cretaceous greenhouse climates arises because of the diagenetic alteration of tropical planktic foraminiferal calcite near the seafloor yielding artificially high 18o values because the mg ca compositions of foraminiferal and inorganic calcite are thought to be quite different mg ca measurements should be a sensitive way of monitoring diagenetic alteration here we examine the extent of diagenetic alteration of eocene planktic foraminiferal calcite using scanning electron microscope imaging of foraminiferal test microstructures and geochemical 18o and mg ca analyses we compare microstructural and geochemical characteristics between given species exhibiting two contrasting states of preservation those that appear frosty under reflected light and those that appear glassy microstructural evidence reveals extensive diagenetic alteration of frosty foraminiferal tests at the micron scale while 18o analyses document consistently higher 18o and therefore lower paleotemperatures in this material yet we find that 18o offsets between species in these frosty foraminiferal assemblages appear to be generally preserved suggesting that frosty foraminifera remain valuable for generating relatively short approximately 1 myr paleoceanographic time series that do not demand absolute estimates of paleotemperature we also find that the observed increase in mg ca for planktic foraminifera exhibiting diagenetic alteration compared to glassy taphonomies is far smaller than would be expected from the addition of inorganic calcite based on laboratory derived mg2 partition coefficients our findings imply that a much lower mg2 partition coefficient controls inorganic calcite formation in deep sea sedimentary sections in accordance with the findings of baker et al 1982

seasonal variation in the oxygen isotopic composition of different sized planktonic foraminifer neogloboquadrina pachyderma sinistral in the northwestern north pacific and implications for reconstruction of the paleoenvironment 1 the oxygen isotope value 18o of planktonic foraminifer shells is one of the most commonly used proxies to reconstruct the paleoenvironment neogloboquadrina pachyderma sinistral n pachyderma sin is a dominant foraminifer in subpolar and polar region that is used extensively for high latitude paleoreconstruction the present study examined seasonal variation in 18o of n pachyderma sin using sediment trap samples collected over 3 5 years in the northwestern north pacific ocean the vital offset value was about 1 which agrees with previous plankton tow studies large shell individuals 180 250 m secrete their shells in a shallower and warmer environment than small ones 125 180 m and the difference in 18o between shell size showed seasonal variation although large individuals calcify at a slower rate with slightly heavier 18o than small individuals differences between size classes mainly reflect different habitation in the water column and are related to seasonal changes in stratification during summer large individuals would calcify mainly at 25 35 m depth while small individuals calcify near the pycnocline at 45 m during winter both size classes calcify at or slightly above the weak pycnocline at 45 65 m thus the shell 18o could record the oceanographic environment around pycnocline depth and size specific differences in 18o reflect water column stratification the annual flux weighted 18o corresponded to non flux weighted mean 18o value due to the equal contribution of two flux peaks and differences between size classes also related to the stratification it suggests that fossil 18o data could represent the annual mean environment around pycnocline and past stratification

simulation of barotropic and baroclinic tides off northern british columbia abstract the tidal response of northern british columbia coastal waters is studied through simulations with a three dimensional prognostic primitive equation model the model is forced at the boundaries with the leading semidiurnal and diurnal constituents and experiments with stratified and homogeneous fluid are compared the barotropic response shows good agreement with previously published studies of tides in the region a comparison with tide gauge measurements indicates that average relative rms differences between observations and the model surface elevation field are less than 5 for the largest constituents an internal tide is generated in cases where the model is initialized with a vertical stratification diagnostic calculations of the baroclinic energy flux are used to identify regions of generation and propagation of internal tidal energy with a representative summer stratification the integrated offshore flux is about 0 5 gigawatts higher than previously estimated from theoretical model

evidence for enhanced convection of north pacific intermediate water to the low latitude pacific under glacial conditions we provide high resolution foraminiferal stable carbon isotope 13c records from the subarctic pacific and eastern equatorial pacific eep to investigate circulation dynamics between the extratropical and tropical north pacific during the past 60 kyr we measured the 13c composition of the epibenthic foraminiferal species cibicides lobatulus from a shallow sediment core recovered from the western bering sea so201 2 101kl 58 52 52 n 170 41 45 e 630 m water depth to reconstruct past ventilation changes close to the source region of glacial north pacific intermediate water gnpiw information regarding glacial changes in the 13c of subthermocline water masses in the eep is derived from the deep dwelling planktonic foraminifera globorotaloides hexagonus at odp site 1240 00 01 31 n 82 27 76 w 2921 m water depth apparent similarities in the long term evolution of 13c between gnpiw intermediate waters in the eastern tropical north pacific and subthermocline water masses in the eep suggest the expansion of relatively 13c depleted nutrient enriched and northern sourced intermediate waters to the equatorial pacific under glacial conditions further it appears that additional influence of gnpiw to the tropical pacific is consistent with changes in nutrient distribution and biological productivity in surface waters of the glacial eep our findings highlight potential links between north pacific mid depth circulation changes nutrient cycling and biological productivity in the equatorial pacific under glacial boundary conditions

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

shell fluxes of solution resistant planktonic foraminifers as a proxy for mixed layer depth 1 shell fluxes of solution resistant planktonic foraminifera g scitula and n dutertrei collected by moored sediment traps are examined as a possible tool to reconstruct the surface water convection in the past subtropical western north pacific time series observation reveals that shell fluxes of these two species fluctuate in an opposite sense when surface water is warmed and well stratified n dutertrei fluxes reach a maximum in contrast g scitula increases in response to the deepening of the mixed layer to amplify the response of shell fluxes to climatological variables the shell flux ratio of g scitula to n dutertrei fg sci n dut is introduced the time series fg sci n dut pattern is similar to that of the monsoon index moi representing the strength of the east asian winter monsoon the fg sci n dut is also well correlated with the mixed layer depth these correlations allow reconstruction of the ancient moi and mld from the faunal ratio

lower cretaceous provenance and sedimentary deposition in the eastern carpathians inferences for the evolution of the subducted oceanic domain and its european passive continental margin

water mass conversion in the glacial subarctic pacific 54 n 148 w physical constraints and the benthic planktonic stable isotope record benthic uvigerina spp cibicidoides spp gyroidinoides spp and planktonic n pachyderma sinistral g bulloides stable isotope records from three core sites in the central gulf of alaska are used to infer mixed layer and deepwater properties of the late glacial subarctic pacific glacial interglacial amplitudes of the planktonic 18o records are 1 1 1 3 less than half the amplitude observed at core sites at similar latitudes in the north atlantic these data imply that a strong negative w anomaly existed in the glacial subarctic mixed layer during the summer which points to a much stronger low salinity anomaly than exists today if true the upper water column in the north pacific would have been statically more stable than today thus suppressing convection even more efficiently this scenario is further supported by vertical i e planktic versus benthic 18o and 13c gradients of 1 which suggest that a thermohaline link between pacific deep waters and the subarctic pacific mixed layer did not exist during the late glacial epibenthic 13c in the subarctic pacific is more negative than at tropical subtropical pacific sites but similar to that recorded at southern ocean sites suggesting ventilation of the deep central pacific from mid latitude sources e g from the sea of japan and sea of okhotsk still convection to intermediate depths could have occurred in the subarctic during the winter months when heat loss to the atmosphere sea ice formation and wind driven upwelling of saline deep waters would have been most intense this would be beyond the grasp of our planktonic records which only document mixed layer temperature salinity fields extant during the warmer seasons also we do not have benthic isotope records from true intermediate water depths of the subarctic pacific

reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer globorotalia truncatulinoides geochemical and morphological characteristics of globorotalia truncatulinoides a deep dwelling planktonic foraminifer have been used since the mid 1950s to infer paleo oceanographic conditions of the upper ocean the coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and or season here we show that the isotopic composition of single specimens covering termination iii of multiple size fractions of north atlantic g truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to g truncatulinoidesdextral as previously indirectly inferred in a plankton tow study furthermore the change in coiling ratio from dominantly g truncatulinoidesdextral 95 to brief episodes of dominantly g truncatulinoidessinistral 80 gives a strong indication of deepening of the permanent thermocline during periods in which g truncatulinoidessinistral was dominant the position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the atlantic meridional overturning circulation amoc dominated by interglacial glacial dynamics we demonstrate that glacial heinrich ice rafted debris events appear to proceed a permanent thermocline shoaling whereas interglacial heinrich events follow the shoaling of the permanent thermocline likely a result of a weakened amoc

alkenones and multiproxy strategies in paleoceanographic studies 1 we assess multiproxy strategies involving alkenone based and other paleoceanographic indicators in an effort to define uncertainties and to advance understanding of past oceanic and climatic changes looking to the future we recommend a parallel strategy of applying proxies to the geologic record while continuously seeking refinements in methods and understanding of mechanisms that control each proxy a multiproxy strategy increases confidence in results and provides oceanographic context for more effective interpretation of processes a combination of proxies allows derivation of additional properties such as upper ocean paleosalinity or paleo pco2 for a more complete view of the oceanographic and climate mechanisms involved in changing earth s environment

response of mallorca shelf ecosystems to an early holocene humid phase abstract benthic foraminiferal data as well as stable oxygen and carbon isotope records of different planktonic and benthic foraminifera from a shelf sediment core off southwest mallorca document major sedimentological hydrological and trophic changes during the holocene the holocene relative sea level rise resulted in the progradation of different sediment facies types characterized by specific benthic foraminiferal assemblages this succession reflects the evolution from an unstable shelf ecosystem with high energy conditions at the sea floor in the earlier holocene to a more stable shelf ecosystem in the middle and late holocene between approximately 10 3 and 5 5 kyr bp low 13c values of the surface dweller globigerinoides ruber white and high difference in 13c values between the epifaunal cibicides lobatulus and the infaunal bulimina aculeata document enhanced input of nutrients in surface waters and high remineralization rates at the sea floor the trophic change is associated with a change in sediment facies and can be attributed to higher precipitation and consequently higher nutrient supply via riverine runoff from the island mainly during the late summer early fall season this early holocene humid interval is nearly contemporaneous to the formation of sapropel s1 in the eastern mediterranean sea and the african humid period

the azores front since the last glacial maximum the spatial distribution of warm surface water in the atlantic ocean reflects the state of the thermohaline circulation the azores current front which is a recirculation of the gulf stream marks the northeastern boundary of the north atlantic subtropical gyre its position is therefore diagnostic of the width of the atlantic warm water sphere here we report high resolution stable isotope and faunal abundance records of planktonic foraminifera in a sediment core from the gulf of cadiz southwest spain which reflects shifting of the azores front since the last glacial maximum lgm today the azores front does not penetrate into the gulf of cadiz even though the front resides at the same latitude as the gulf of cadiz in the atlantic our results indicate that the azores front is a robust feature of the atlantic surface circulation and that is present both in interglacial times and during the lgm at roughly the same latitude however during the lgm prior to 16 ka bp and during the younger dryas the azores front did penetrate eastward into the gulf of cadiz

is methane venting at the seafloor recorded by δ13c of benthic foraminifera shells the research was supported by wcnurp grant pf806880 and by nsf grants oce 9731157 oce 9815186 and oce 9906944 curation of sediment cores at the osu norcor repository is supported by nsf

the evolution of the southern margin of the east european craton based on seismic and potential field data abstract this paper presents an integrated geophysical study of the southern margin of the east european craton eec in the karpinksy swell north caucasus area it presents new interpretations of deep refraction and wide angle reflection deep seismic sounding dss data as well as conventional seismic and cdp profiling and new analyses of potential field data including three dimensional gravity and magnetic modelling an integrated model of the physical properties and structure of the earth s crust and partially upper mantle displays distinct features that are related to tectonic history of the study area the voronezh massif vm the ukrainian shield and rostov dome rd of the eec as well as the donbas foldbelt df karpinsky swell ks scythian plate sp and precaspian basin pcb constitute the geodynamic ensemble that developed on the southern margin of the continent baltica there proposed evolutionary model comprises a stage of rifting during the middle to late devonian post rift extension and subsidence during carboniferous early permian times synchronous with and related to the southward displacement of the rostov dome and extension in a palaeo scythian back arc basin and subsequent mesozoic and younger evolution a pre ordovician possibly riphean mafic magmatic complex is inferred on a near vertical reflection seismic cross section through the western portion of the astrakhan dome in the southwest part of the precaspian basin this complex combined with evidence of a subducting slab in the upper mantle imply the presence of pre ordovician riphean island arc with synchronous extension in a precaspian back arc basin is suggested a middle palaeozoic back arc basin ensemble in what is now the western karpinsky swell was more than 100 km to the south from its present location the stavropol high migrated northwards dislocating and moving fragments of this back arc basin sometime thereafter linear positive magnetic anomalies reflect the position of associated faults which define the location of the eastern segment of the karpinsky swell these faults which dip northward are recognised on crustal dss profiles crossing the donbas foldbelt and scythian plate they are interpreted in terms of compressional tectonics younger than the hercynian stage of evolution i e post palaeozoic

living neogloboquadrina pachyderma sin and its distribution in the sediments from oman and somalia upwelling areas abstract microfaunal analysis of plankton nets collected offshore oman yemen and sediment traps offshore somalia shows that neogloboquadrina pachyderma sin is abundant during the sw monsoon upwelling the sediment traps recorded the highest flux 136 specimens m 2 day 1 and the highest relative frequency 3 55 of the total foraminifera assemblage of the species during this period during the intermonsoon it became less abundant and decreased in size and only very few n pachyderma sin were found in the water column during the ne monsoon sediment trap and recent sediment data collected along a downslope transect off somalia show that the species frequency decreases offshore the highest concentrations of n pachyderma sin in plankton nets off oman yemen were found at a depth of 300 500 m however the oxygen isotope compositions of n pachyderma sin at the depth of 300 500 m and from the surface 8 m are identical and also similar to that of globigerina bulloides which reflects properties of the upper 25 m of the water column the carbon isotope values are relatively consistent within the studied samples from both areas except for the specimens from the surface water samples offshore oman yemen the data show that the 18o ratio of n pachyderma sin is in equilibrium with the ambient water while the 13c values are at least 0 8 lower we infer that n pachyderma sin in the arabian sea reproduces grows and calcifies in the upper 25 m of the water column but possibly descends into deeper waters later during its life cycle

oceanographic variability in the southern gulf of california over the past 400 years evidence from faunal and isotopic records from planktic foraminifera abstract oceanographic conditions during the past four centuries sea surface temperature sst centennial and decadal variability and changes in the water column structure were reconstructed in high resolution from foraminiferal assemblages and stable isotope analyses completed on laminated sediments from two multicores mc15 415 m depth and mc26 600 m depth from the southern gulf of california eastern subtropical pacific total abundance counts and oxygen isotopic analyses were performed on two planktonic species globigerina bulloides a proxy for winter sst and pulleniatina obliquiloculata a proxy for late fall subsurface water temperature multidecadal oscillations in 18o values are considered to result primarily from extratropical forcing sea level pressure anomalies in the north pacific via northwesterly winds weakening strengthening in association with changes in the average position and intensity of the aleutian low the downcore evolution of both biological proxies revealed an increase in sst since the 1600s reflecting a gradual decline in upwelling activity during this period this temperature trend implies a long term change that cannot be explained by the same mechanisms associated with the multidecadal oceanographic variability we proposed that the progressive warming of the surface waters is linked to a general northward shift of the itzc resulted from increased solar irradiation which accounts for larger net surface shortwave fluxes affecting regional heating patterns and consequently the sensitive regional climate

ventilation of north pacific intermediate waters the role of the alaskan gyre hydrographic data tritium data and potential vorticity calculations suggest that although north pacific intermediate water is formed in the northwest the alaskan gyre might be an additional ventilation site the proposed ventilation is quantified by a vertical column tritium inventory which indicates an excess of 0 08 kg of tritium in the alaskan gyre an evaluation of the energy stored in the water column and of wind and buoyancy forcing shows that during winter conditions enough energy can be pumped into the system to force 26 80 to outcrop in the alaskan gyre model results suggest that relatively limited outcrops in time and space tens of days and several hundred kilometers in diameter can account for the excess tritium

why is the spreading of the north pacific intermediate water confined on density surfaces around σθ 26 8 abstract the north pacific intermediate water characterized by a salinity minimum confined to density surfaces of 26 7 26 9 exists throughout the subtropical gyre and has been observed to originate in the subarctic north pacific the physical processes that determine the density range on which the npiw resides are not yet well understood this study attempts to clarify these processes by combining observational data and a simple advection diffusion isopycnal model due to the regional excessive precipitation over evaporation the salinity in the upper layer subarctic north pacific generally decreases with decreasing water depth both alongisopycnal advection and diffusion work to carry this salinity depth characteristic into the subtropical circulation for the isopycnal surfaces overlying the npiw however this transport mechanism is hindered by the seasonal outcropping the outcropping not only blocks the fresh subarctic water from advecting and diffusing along these isopycnals into the subtropi

oxygen isotope fractionation in the ostracod eucypris mareotica results from a culture experiment and implications for paleoclimate reconstruction oxygen isotope analysis of the adult ostracod eucypris mareotica cultured at controlled temperatures 10 15 and 19 c was used to measure isotopic fractionation during shell calcification the ostracod shells that precipitated at experimental temperatures are almost in isotopic equilibrium with the culture water as compared to the oxygen isotope fractionation of inorganic carbonates moreover they had almost constant offsets from equilibrium based on the oxygen isotope fractionation of inorganic carbonates the 18o values of ostracod shells from the 10 c cultures were higher than those of the 15 and 19 c cultures by 1 6 and 2 7 respectively the observed fractionations are shown by the regression equations begin array 20 c 10 circ text c delta 1 8 text o text ostracod 1 1 7 0 5 7 delta 1 8 text o text water 1 5 circ text c delta 1 8 text o text ostracod 0 4 8 0 6 delta 1 8 text o text water 1 9 circ text c delta 1 8 text o text ostracod 1 6 0 6 delta 1 8 text o text water end array the fractionation factors are slightly lower for the 15 and 19 c cultures but slightly higher for the 10 c culture as compared to inorganic carbonates o neil et al in j chem phys 51 5547 5558 1969 the oxygen fractionation factors of e mareotica are very close to those of synthetic calcite formed in isotopic equilibrium the vital offsets of valve 18o for e mareotica is so small that we can neglect its effect when using the 18o of e mareotica living in lake waters with high ph and salinity to reconstruct the paleoenvironment the paleotemperature or paleoisotopic composition of lake water interpreted from a core of lacustrine sediment may be closer to the true values when the 18o data for e mareotica are used

upwelling filaments and motion of a satellite tracked drifter along the west coast of north america an argos tracked surface buoy deployed off vancouver island in july 1984 reached hawaii in july 1985 we present an analysis of the drifter track with particular emphasis on the equatorward leg seaward of the north american coast for the period july december 1984 a low pass filter is used to separate motions into mean and fluctuating components the mean track was consistently to the right of the direction expected according to the climatological geopotential topography relative to 1000 dbar and the average southward drift speed of 0 20 m s 1 exceeded the mean geopotential flow speed by a factor of 2 3 on the basis of 1 year of drifter positions we estimate that surface waters complete one circuit of the north pacific gyre in 4 5 years the amplitudes of the mesoscale buoy displacements about the mean path were approximately 43 10 km and the root mean square drift speed was 0 32 0 18 m s 1 motions at tidal and near inertial frequencies were negligible from august to october the buoy paralleled a major upwelling regime centered off northern california during this period the track underwent five sinuous zonal perturbations with characteristic amplitudes of approximately 50 km two of the perturbations were associated with abrupt temperature drops of 3 c and maximum seaward currents of 0 70 m s 1 national oceanic and atmospheric administration advanced very high resolution radiometer thermal imagery for these times reveals that the buoy had encountered seaward protruding cold water filaments squirts associated with 100 km length upwelling zones that constitute the large scale upwelling regime southward of the upwelling regime the equatorward drift speed of the buoy was only slightly greater than the equatorward advance of the surface isotherms suggesting that advection rather than winter cooling might be mainly responsible for the shift in the temperature pattern

shallow salinity minima in the north pacific abstract ctd std data from 24 cruises in the north pacific are studied for their vertical salinity structure and compared to bottle observations a triple salinity minimum is found in two separated regions in the eastern north pacific in the first region bounded by the northern edge of the subarctic frontal zone and the 34 n front between 160 and 150 w a middle salinity minimum is found below the permanent pycnocline in the density range of 26 0 and 26 5 this middle minimum underlies reid s shallow salinity minimum and overlies the north pacific intermediate water npiw in the second region southeast of the first a seasonal salinity minimum appears above the shallow salinity minimum at densities lower than 25 1 the shallow salinity minimum and the npiw can be found throughout year while the seasonal minimum only appears in summer and fall the middle and shallow salinity minima as well as the seasonal minimum originate at the sea surface in the northeast pacific the properties at the m

coccolith δ18o and alkenone records in middle pliocene orbitally controlled deposits high frequency temperature and salinity variations of sea surface water 1 the calcareous nannoplankton flora is strongly controlled by water masses and is sensitive to ambient nutrient levels in consequence fossil remains of calcareous nannoplankton are useful tools for paleoceanography although they are the major producers of carbonates in the pelagic realm their use as a seawater 18o recorder is not easy due to their small size and the difficulty in isolating them from the bulk carbonate using a granulometric separation technique minoletti et al 2001 it is now possible to concentrate coccoliths in monospecific fractions we applied this method on three precession cycles insolation cycles i 288 to i 282 from the mid pliocene punta piccola section south sicily which led to an almost pure pseudoemiliana lacunosa fraction it was then possible to measure the isotopic signatures 18o and 13c and alkenone unsaturation ratio on the same recorder p lacunosa this permits a precise reconstruction of environmental conditions temperature and salinity that prevailed in the upper photic zone during the cyclic deposition of these sediments our data provide a clear confirmation that sapropelic marl formation occurred during a wetter climate compared to the deposition of the marly limestones moreover these results point out that salinity variations are not as previously thought always the primary factor that controlled the deposition of these cyclic events this study is a step forward in the utilization of calcareous nannoplankton isotopic records in paleoenvironmental reconstructions

the effect of species on lacustrine δ18odiatom and its implications for palaeoenvironmental reconstructions the oxygen isotope composition of diatom silica 18odiatom is increasingly being used to reconstruct climate from marine and lacustrine sedimentary archives although diatoms are assumed to precipitate their frustule in isotopic equilibrium with their surrounding water it is unclear whether internal processes of a given species affect the fractionation of oxygen between the water and the diatom we present 18odiatom data from two diatom size fractions 3 38 and 38 m characterized by different species in a sediment core from heart lake alaska differences in 18odiatom between the two size fractions varies from 0 to 1 2 with a mean offset of 0 01 n 20 fourier transform infrared spectroscopy confirms our samples consist of pure biogenic silica sio2 and 18odiatom trends are not driven by contamination the maximum offset is outside the range of error but the mean is within analytical error of the technique 1 06 demonstrating no discernible species dependent fractionation in 18odiatom we conclude that lacustrine 18odiatom measurements offer a reliable and valuable method for reconstructing 18owater considering the presence of small offsets in our two records we advise interpreting shifts in 18odiatom only where the magnitude of change is greater than the combined analytical error

holocene influx of the tsushima current into the japan sea signalled by spatial and temporal changes in neogloboquadrina incompta distribution neogloboquadrina incompta is an optimal marker of the transitional water formed by mixing of the warm tsushima current with cold waters of the japan sea spatial and temporal changes in n incompta distribution have been analysed to reconstruct the timing and processes by which modern surface water conditions were established in the japan sea as a function of postglacial influx of the tsushima current resulting from rising sea levels the spatiotemporal distribution of n incompta suggests that transitional water formed in the eastern to southern marginal regions of the japan sea prior to the deposition of the k ah tephra 7 3 cal kyr bp and then expanded southwestward a northern cold water mass together with the cold liman current affected the southwestern part of the japan sea until 6 9 cal kyr bp which may have been a result of the weaker influence of the tsushima current during a time of lower sea level

paired δ18o signals of neogloboquadrina pachyderma s and turborotalita quinqueloba show thermal stratification structure in nordic seas abstract the vertical density gradients in the nordic seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter these gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera the isotopic signatures of which represent different calcification depths in the water column comparison of 18 o values from foraminiferal tests in plankton hauls sediment traps and nearby core top samples with the calculated 18 o calcite profile of the water column revealed species specific 18 o vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment on the basis of core top samples obtained along a west east transect across various hydrographic regions of the nordic seas 18 o values of turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25 75 m water depth the isotopic signatures of neogloboquadrina pachyderma s reflect water masses near and well below the pycnocline between 70 and 250 m off norway where the atlantic inflow leads to thermal stratification here temperatures in the calcification depth of n pachyderma s differ from sea surface temperature by approximately 2 5 c in contrast n pachyderma s calcifies very close to the sea surface 20 50 m in the arctic domain of the western nordic seas however further west n pachyderma s prefers somewhat deeper more saline water at 70 130 m well below the halocline that confines the low saline east greenland current this implies that the 18 o values of n pachyderma s do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on 18 o is too conservative because it overestimates sea surface salinity minimum 18 o differences n pachyderma s and t quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification whereas thermal stratification leads to 18 o differences of 0 4 to 1 5

paleoenvironmental conditions for the development of calcareous nannofossil acme during the late miocene in the eastern equatorial pacific repeated monospecific coccolithophore dominance intervals acmes of specimens belonging to the noelaerhabdaceae family including the genus reticulofenestra and modern descendants emiliania and gephyrocapsa occurred during the neogene such acme was recognized during the late miocene 8 6 ma at a time of a major reorganization of nannofossil assemblages resulting in a worldwide temporary disappearance of larger forms of the genus reticulofenestra r pseudoumbilicus and the gradual recovery and dominance of its smaller forms 5 m in this study we present a multiproxy investigation of late miocene sediments from the east equatorial pacific integrated ocean drilling program site u1338 where small reticulofenestrid type placoliths with a closed central area known as small dictyococcites spp 3 m formed an acme we report on oxygen and carbon stable isotope records of multispecies planktic calcite and alkenone derived sea surface temperature our data indicate that during this 100 kyr long acme the east equatorial pacific thermocline remained deep and stable local surface stratification state fails to explain this acme and thus contradicts the model based hypothesis of a southern ocean high latitude nutrient control of the surface waters in the east equatorial pacific instead our findings suggest that external forcing such as an extended period of low eccentricity may have created favorable conditions for the small dictyococcites spp growth

variability in vertical distributions of planktonic foraminifera in the california current relationships to vertical ocean structure 1 geochemical records from planktonic foraminifera are among the few means available to infer past changes in the upper ocean although interpretations can be confounded by variability in foraminifera habitat depths the principal environmental factors affecting foraminiferal vertical distributions were examined through 28 vertically stratified plankton tows taken off southern california in winter spring and summer each species has a dynamic range of preferred habitat depth from the mixed layer to the thermocline characterized by a unique relationship with environmental properties globigerina bulloides neogloboquadrina pachyderma dextral and neogloboquadrina dutertrei can live near the surface but frequently live deeper as stratification increases and a particular isotherm deepens globigerinoides ruber and orbulina universa vary more closely with the depth of the thermocline than the depth of a given isotherm the shifts in habitat depth are of sufficient magnitude to affect 18o records the effects of such shifts are observed for g bulloides and n pachyderma in santa barbara basin sediments geochemical signatures from multiple species of foraminifera each with a different predicted response to environmental change can permit the detection of changes in habitat depth of a given species and thus more accurately indicate past changes in hydrographic structure

palaeoecology of late middle eocene planktic foraminifera and evolutionary implications the late middle eocene is marked by accelerated global cooling representing part of the long transitional interval separating the early eocene greenhouse and later oligocene icehouse climatic regimes this time interval is also regarded as having witnessed a decline in planktic foraminiferal diversity following the extinction of most of the muricate clade genera acarinina and morozovelloides at approximately 39 ma here we examine planktic foraminiferal assemblages recovered at odp site 1052 blake nose nw atlantic and by recording a high level of taxonomic diversity including several previously undocumented morphotypes we suggest that the diversity of late middle eocene planktic foraminifera may have been underestimated depth habitats of every species within these late middle eocene assemblages are reconstructed using oxygen and carbon stable isotope ratios furthermore because stable isotope analyses suggest that species of globoturborotalita appear to have generally calcified during winter months these taxa offer in combination with predominantly summer surface dwellers such as morozovelloides the potential to reconstruct patterns of seasonality during the late palaeogene using extremely well preserved glassy planktic foraminiferal calcite from a contemporaneous hemipelagic drill site detailed sem imaging of test microstructures and wall textures confirm that many modern features of foraminiferal ecology and test architecture had already evolved by the late middle eocene the common occurrence of the cancellate wall texture combined with the wide variety of reconstructed foraminiferal depth habitats indicates that there is no necessary relationship between foraminiferal wall textures and habitat and that wall textures are evolutionary conservative features of the foraminiferal test

wildfire and abrupt ecosystem disruption on california s northern channel islands at the allerod younger dryas boundary 13 0 12 9 ka abstract sedimentary records from california s northern channel islands and the adjacent santa barbara basin sbb indicate intense regional biomass burning wildfire at the allerod younger dryas boundary 13 0 12 9 ka all age ranges in this paper are expressed in thousands of calendar years before present ka radiocarbon ages will be identified and clearly marked 14c years multiproxy records in sbb ocean drilling project odp site 893 indicate that these wildfires coincided with the onset of regional cooling and an abrupt vegetational shift from closed montane forest to more open habitats abrupt ecosystem disruption is evident on the northern channel islands at the allerod younger dryas boundary with the onset of biomass burning and resulting mass sediment wasting of the landscape these wildfires coincide with the extinction of mammuthus exilis pygmy mammoth the earliest evidence for human presence on these islands at 13 1 12 9 ka 11 000 10 900 14c years is followed by an apparent 600 800 year gap in the archaeological record which is followed by indications of a larger scale colonization after 12 2 ka although a number of processes could have contributed to a post 18 ka decline in m exilis populations e g reduction of habitat due to sea level rise and human exploitation of limited insular populations we argue that the ultimate demise of m exilis was more likely a result of continental scale ecosystem disruption that registered across north america at the onset of the younger dryas cooling episode contemporaneous with the extinction of other megafaunal taxa evidence for ecosystem disruption at 13 12 9 ka on these offshore islands is consistent with the younger dryas boundary cosmic impact hypothesis firestone r b west a kennett j p becker l bunch t e revay z s schultz p h belgya t kennett d j erlandson j m dickenson o j goodyear a a harris r s howard g a kloosterman j b lechler p mayewski p a montgomery j poreda r darrah t que hee s s smith a r stich a topping w wittke j h wolbach w s 2007 evidence for an extraterrestrial impact 12 900 years ago that contributed to the megafaunal extinctions and younger dryas cooling proceedings of the national academy of sciences 104 16016 16021

stable oxygen and carbon isotopes in planktonic foraminifera neogloboquadrina pachyderma in the arctic ocean an overview of published and new surface sediment data abstract a summary study on oxygen and carbon stable isotopes in planktonic foraminifera from arctic ocean floor appeared in marine geology 20 years ago spielhagen and erlenkeuser 1994 we revisit this topic with a wealth of new data focused on the western amerasian arctic a spotlight in the current climatic and oceanic change neogloboquadrina pachyderma the most abundant polar planktonic foraminiferal species is an important tool for reconstructing surface subsurface water changes in the arctic our new data on n pachyderma 150 250 m from the surface sediments show 18 o and 13 c values of 18 o and 13 c are both influenced by complex water sources water column structure and foraminiferal depth habitat the observed distribution of n pachyderma stable isotopes confirms a shallow habitat of this species in the sea ice covered central arctic especially in the canada basin probably in relation to the shallow chlorophyll maximum the associated light n pachyderma 18 o reflects the long term storage of fresh water at the shelf break a deeper dwelling of n pachyderma with heavier 18 o is supported by a more extensive photic zone and nutrient availability air sea exchange plays an important role in 13 c distribution and is consistent with heavy n pachyderma 13 c in the perennially ice covered central arctic ocean light 13 c composition at the shelf break is additionally influenced by shelf bottom waters enriched in isotopically light remineralized terrestrial carbon distribution of foraminiferal 13 c on the chukchi shelf reflects primary production patterns in the area

millennial scale variability to 735 ka high resolution climate records from santa barbara basin ca 1 determining the ultimate cause and effect of millennial scale climate variability remains an outstanding problem in paleoceanography partly due to the lack of high resolution records predating the last glaciation recent cores from santa barbara basin provide 2500 5700 year windows of climate with 10 50 year resolution ages for three cores determined by seismic stratigraphic correlation oxygen isotope stratigraphy and biostratigraphy date to 293 ka mis 8 450 ka mis 12 and 735 ka mis 18 these records sample the late pleistocene during which the 100 kyr cycle strengthened and the magnitude of glacial interglacial cyclicity increased thus these records provide a test of the dependence of millennial scale behavior on variations in glacial interglacial cyclicity the stable isotopic 18o composition of planktonic foraminifera shows millennial scale variability in all three intervals with similar characteristics duration cyclicity to those previously documented during mis 3 at this site stadial g bulloides 18o values are 2 75 1 75 average 2 25 and interstadial values are 1 75 0 5 average 1 with rapid decadal scale interstadial and stadial initiations of 1 2 as in mis 3 interstadials lasted 250 1600 years and occurred every 650 1900 years stadial paleotemperatures were 3 5 9 5 c and interstadial paleotemperatures were 7 5 13 c upwelling evidenced by planktonic foraminiferal assemblages and 13c increased during interstadials similar to mis 3 high productivity during some stadials was reminiscent of the last glacial maximum this study builds upon previous records in showing that millennial scale shifts were an inherent feature of northern hemisphere glacial climates since 735 ka and they remained remarkably constant in the details of their amplitude cyclicity and temperature variability

geochemical characteristics of the adakite like dodurga pluton central pontides n turkey implications for middle triassic continental arc magmatism in southern black sea region the tracing of triassic arc magmatism is much debated for a long time along the sakarya composite terrane in turkey and the southern black sea region the dodurga pluton is located in the central pontides n turkey one of the most complicated regions around the black sea region and represents the first documented middle triassic continental arc in the region this pluton comprises of dacite porphyry and granodiorite and displays calc alkaline signatures which is in agreement with arc related and i type magmas the pm normalized multi element and cn normalized ree patterns are akin to volcanic arc granites and characterized by liles and lrees enrichments relative to hfses and hrees coupled with negative nb anomalies which confirm derivation in a subduction related tectonic setting moreover the major and trace element systematics of the samples including higher sr y ratios 22 93 101 36 and lower yb contents 0 31 1 30 ppm are consistent with those from adakitic melts compared to classical arc magmas therefore this pluton also represents the first middle triassic adakite like magmatic occurrence in turkey overall petrographic and geochemical signatures reported here indicate that the dodurga pluton might have been derived from a heterogeneous source mixed by melts from subducted oceanic slab and lower continental crust in an active continental margin based on the tethyan evolution in the anatolian realm three geodynamic scenarios are possible for its formation and it could have been formed as a result of northward or southward subduction of the paleotethys ocean or northward subduction of the northern branch of neotethys ocean during the middle triassic

hydrographic conditions along the western iberian margin during marine isotope stage 2 the surface water hydrography along the western iberian margin as part of the north atlantic s eastern boundary upwelling system consists of a complex seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions such as during marine isotope stage mis 2 and how north atlantic meltwater events especially heinrich events affected them to help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern iberian margin md95 2040 md95 2041 md99 2336 and md99 2339 the records reveals that with the exception of the heinrich events and greenland stadial gs 4 hydrographic conditions along the western iberian margin were not much different from the present during the last glacial maximum lgm subtropical surface and subsurface waters penetrated poleward to at least 40 6 n site md95 2040 export productivity was in general high on the western margin during the lgm and low in the central gulf of cadiz in agreement with the modern situation during the heinrich events and gs 4 on the other hand productivity was high in the gulf of cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling heinrich event 1 had the strongest impact on the hydrography and productivity off iberia and was the only period when subarctic surface waters were recorded in the central gulf of cadiz south of lisbon 39 n the impact of the other heinrich events was diminished and not all of them led to a significant cooling in the surface waters thus climatic impacts of heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region

size dependent isotopic composition of planktic foraminifers from chukchi sea vs nw atlantic sediments implications for the holocene paleoceanography of the western arctic abstract in arctic and sub arctic seas shell growth and or secondary calcite overgrowth of neogloboquadrina pachyderma left coiled npl occur along the pycnocline and their 13c and 18o values are size and weight dependent however whereas the npl 18o data from the nw atlantic indicate near equilibrium conditions with ambient waters and a positive relationship between shell weight and 18o content assemblages from box cored sediments of the chukchi sea western arctic are depleted by 2 with respect to equilibrium values with modern conditions and depict a negative relationship between shell weight and its 18o value 0 15 0 03 g on vpdb scale a similar feature is also depicted by the dextral form of n pachyderma npd we associate the reverse shell size or weight vs 18o relationship to the reverse temperature gradient observed along the thermocline between the surface cold and dilute water layer and the underlying near 3 c warmer saline north atlantic water mass the analysis of two late to post glacial sedimentary sequences from the chukchi sea indicates that such a water mass stratification with a reverse thermocline persisted throughout the holocene thus reflecting an early onset of the modern like linkage between the arctic ocean and the north atlantic moreover lower 18o values in both npl and npd together with larger 18o gradients between the different shell sizes at ca 9 7 ka bp suggest 3 c higher temperatures in the upper north atlantic water mass in comparison with the present approximately 1 c at the study site thus likely a higher inflow rate of this water mass during the early holocene

changes in coiling direction habitat depth and abundance in two menardellid species abstract we present a detailed study of menardellid speciation abundance and coiling changes between 6 34 and 5 1 ma latest miocene and earliest pliocene menardellids are widely distributed in tropical to subtropical waters from miocene to modern time revealing a stable isotopic signature characteristic for the top of the thermocline and shallower rather than deeper habitat depth menardellid response to its environment reveals a tripartite pattern the first interval from 6 34 to 5 75 ma is marked by a dominance of menardella limbata frequent changes in coiling direction and variable abundance with strongest reductions during intervals of dextral dominance the onset of an interval of cooling and ice build up at 5 82 ma coincides with a weakening of the mixed layer leading to nearly 70 kyr of strongly reduced menardellid abundance at 5 75 ma menardella multicamerata replaces m limbata as the prevailing menardellid species at the same time as the overall abundance of menardellids stabilises initial stabilisation of sinistral coiling until the end of the cold interval at 5 49 ma suggests the development of a temperature preference in sinistral cold and dextral warm m multicamerata a strong increase in menardellid 13c values relative to the thermocline gradient difference between the 18o records of surface dwelling globigerinoides trilobus and menardella spp following 5 77 ma suggests a move to shallower habitat depths of both m multicamerata morphotypes initiated by mixed layer destabilisation both the development of a temperature preference and the move to shallower habitat depth in m multicamerata appear to identify its adjustment to a new niche driving the replacement of m limbata as the dominant menardellid species

alternating influence of northern versus southern sourced water masses on the equatorial pacific subthermocline during the past 240 ka the eastern equatorial pacific eep is a key area to understand past oceanic processes that control atmospheric co2 concentrations many studies argue for higher nutrient concentrations by enhanced nutrient transfer via southern ocean intermediate water soiw to the low latitude pacific during glacials recent studies however argue against soiw as the primary nutrient source at least during early marine isotope stage 2 mis 2 as proxy data indicate that nutrients are better utilized in the southern ocean under glacial conditions new results from the subarctic pacific suggest that enhanced convection of nutrient rich glacial north pacific intermediate water gnpiw contributes to changes in nutrient concentrations in equatorial subthermocline water masses during mis 2 however the interplay between soiw versus gnpiw and its influence on the nutrient distribution in the eep spanning more than one glacial cycle are still not understood we present a carbon isotope 13c record of subthermocline waters derived from deep dwelling planktonic foraminifera globorotaloides hexagonus in the eep which is compared with published 13c records around the pacific results indicate enhanced influence of gnpiw during mis 6 and mis 2 compared to today with largest contributions of northern sourced intermediate waters during glacial maxima these observations suggest a mechanistic link between relative contributions of northern and southern intermediate waters and past eep nutrient concentrations a switch from increased gnpiw decreased soiw to diminished gnpiw enhanced soiw influence on equatorial subthermocline waters is recognized during glacial terminations and marks changes to modern like conditions in nutrient concentrations and biological productivity in the eep

dansgaard oeschger cycles and the california current system planktonic foraminiferal response to rapid climate change in santa barbara basin ocean drilling program hole 893a high resolution planktonic foraminiferal census data from santa barbara basin ocean drilling program hole 893a demonstrate major assemblage switches between 25 and 60 ka that were associated with dansgaard oeschger cycles stadials dominated by neogloboquadrina pachyderma sinistral and globigerinoides glutinata suggest a strong subpolar california current influence while interstadials marked by abundant n pachyderma dextral and g bulloides indicate a relative increase in subtropical countercurrent influence modern analog technique and transfer function f 20rsc temperature reconstructions support 18o evidence of large rapid 70 years or less sea surface temperature shifts 3 to 5 c between stadials and interstadials changes in the vertical temperature gradient and water column structure thermocline depth are recorded by planktonic faunal oscillations suggest bimodal stability in the organization of north pacific surface ocean circulation santa barbara basin surface water demonstrates the rapid response of the california current system to reorganization of north pacific atmospheric circulation during rapid climate change supporting assemblage data are available on diskette or via anonymous ftp from kosmos agu org directory apend username anonymous password guest diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 or by phone at 800 966 2481 5 00 payment must accompany order

seasonal variability of δ18o and δ13c of planktic foraminifera in the bering sea and central subarctic pacific during 1990 2000 we evaluated a 10 year time series of 18o and 13c records from three planktic foraminifers neogloboquadrina pachyderma globigerina umbilicata and globigerinita glutinata in the bering sea and central subarctic pacific with a focus on their responses to environmental changes foraminiferal 18o followed the equilibrium equation for inorganic calcite with species specific equilibrium offsets ranging from nearly zero 0 02 for n pachyderma and 0 01 for g umbilicata to 0 16 g glutinata equilibrium offsets in our sediment trap samples were smaller than those from plankton tow studies implying that foraminiferal 18o was modified by encrustation during settling habitat calcification depths varied from 35 55 m n pachyderma and g umbilicata or 25 45 m g glutinata during warm stratified seasons to around 100 m during winter when the mixed layer depth increases unlike 18o foraminiferal 13c showed species specific responses to environmental changes we found a dependency of 13c in g umbilicata on co32 concentrations in ambient seawater that agreed reasonably well with published laboratory results suggesting that 13c of g umbilicata is subject to vital effects in contrast 13c of n pachyderma and g glutinata are likely affected by other species specific biological activities seasonal flux patterns reveal that fossil records of n pachyderma and g glutinata represent annual mean conditions whereas that of g umbilicata most likely indicates those of a specific season because none of these three taxa was abundant from december to february their fossil records likely do not reflect isotope signals from cold seasons

increasing seasonal upwelling in the subtropical south atlantic over the past 700 000 yrs evidence from deep living planktonic foraminifera abstract the distribution and character of deep living planktonic foraminifera such asgloborotalia truncatulinoides andg hirsuta are particularly sensitive to the structure of the upper ocean because of the wide range of water depths over which their life cycles extend like other planktonic foraminifera the deep living species begin growing in shallow surface waters but unlike the other species they continue growing while sinking into much deeper water their reproduction is synchronized with the seasonal deep mixing and upwelling of nutrient rich waters that precedes spring bloom where deep mixing is curtailed the abundances of the deeper dwelling species g hirsuta the deeper dwelling varieties e g left coilingg truncatulinoides and the larger presumably faster sinking shells are reduced leading to an apparent acceleration in shell development these changes are observed today in transects from the seasonally deep mixed subtropical gyres to the seasonally stable surface waters equatorward of the subtropical convergences past changes in the abundance and character of these deep living planktonic foraminifera have been measured in a late pleistocene record from the subtropical western south atlantic ocean over the past 700 kyrs abundances of these species have increased g truncatulinoides has changed from the predominantly shallower dwelling right coiling to the deeper dwelling left coiling variety and the accelerated shell development characteristic of shallow mixing has shifted toward the rates normally associated with deep mixing all this indicates that the structure of the upper ocean in the subtropical south atlantic before 700 kyrs ago was more like that nearer the equator today where mixing is limited to the upper 100 200 m since that time the scale of mixing has gradually increased to more than 400 m this implies a gradual increase through the late pleistocene in the seasonal upwelling of nutrients in the subtropical south atlantic and consequently in the intensity of the seasonal maximum in organic productivity

profiling planktonic foraminiferal crust formation planktonic foraminifera migrate vertically through the water column during their life thereby growing and calcifying over a range of depth associated conditions some species form a calcite veneer crust or cortex at the end of their lifecycle this additional calcite layer may vary in structure composition and thickness potentially accounting for most of their total shell mass and thereby dominating the element and isotope signature of the whole shell here we apply laser ablation icp ms depth profiling to assess variability in thickness and mg ca composition of shell walls of three encrusting species derived from sediment traps compositionally mg ca is significantly lower in the crusts of neogloboquadrina dutertrei and globorotalia scitula as well as in the cortex of pulleniatina obliquiloculata independent of the species specific mg ca of their lamellar calcite shell wall thickness accounts for nearly half of the total thickness in both crustal species and nearly a third in cortical p obliquiloculata regardless of their initial shell wall thickness crust thickness and crustal mg ca decreases toward the younger chambers in n dutertrei and to a lesser extent also in g scitula in contrast the cortex of p obliquiloculata shows a nearly constant thickness and uniform mg ca through the complete chamber wall patterns in thickness and mg ca of the crust indicate that temperature is not the dominant factor controlling crust formation instead we present a depth resolved model explaining compositional differences within individuals and between successive chambers as well as compositional heterogeneity of the crust and lamellar calcite in all three species studied here

seasonal variations in planktonic foraminiferal flux and oxygen isotopic composition in the western north pacific implications for paleoceanographic reconstruction abstract the oxygen isotopic composition 18o of planktonic foraminiferal shells in seafloor sediment provides information on past surface oceanography knowledge of seasonal and depth habitat as well as the 18o disequilibrium vital effect is essential to constrain the interpretation of sedimentary 18o here we present a 1 year time series of planktonic foraminiferal shell fluxes and 18o from a sediment trap moored in the northwestern margin of the north pacific the vital effect and calcification depth for four species were estimated by comparing shell 18o and the predicted values of equilibrium calcite calculated from temperature and estimated 18o in seawater six major species neogloboquadrina incompta neogloboquadrina dutertrei neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globorotalia scitula constituted 97 of the total foraminiferal flux most major species showed large fluxes in june and december corresponding to periods of the development and disruption of the seasonal thermocline implying the importance of nutrient injection and or circulation for foraminiferal fluxes additional peaks in n dutertrei and n pachyderma were observed in august the seasonal successions of foraminiferal fluxes corresponded to surface ocean stratification conditions and food availability which are closely related to circulation of local currents vital effect estimations suggest that shells calcified in equilibrium for g bulloides and n pachyderma sinistral s and with a 0 7 offset for n dutertrei dextral d a 1 0 offset for n incompta d and a 0 3 offset for n pachyderma d the calculation of flux weighted 18o values reveals that the sedimentary 18o values of g bulloides n dutertrei d and n incompta d reflect surface temperature in winter season and those of n pachyderma s and n pachyderma d reflect summer and annual mean subsurface temperature respectively the shallow calcification depths for the four species suggest that 18o between different species 18o in the western north pacific does not work for reconstructing past stratification conditions unlike in other regions rather the 18o between n pachyderma s and g bulloides n dutertrei d or n incompta d may be a more suitable proxy for past seasonality

fine fraction carbonate stable isotopes as indicators of seasonal shallow mixed layer paleohydrography we have measured stable isotopic compositions of miocene pelagic fine fraction 6 63 wm carbonates from oligotrophic deep sea sites in the pacific and atlantic oceans and compared them with those of coexisting foraminifers to test their utility as near sea surface indicators fine fraction carbonates primarily polyspecific nannofossils and surface dwelling planktic foraminiferal globigerinoides stable isotopes both have been considered to reflect surfacewater hydrographic conditions however our results indicate that fine fraction stable isotopes are offset from and do not correlate well with those of globigerinoides in contrast stable isotopic records of the deep dwelling planktic foraminifer globoquadrina are in good correspondence with the fine fraction records in terms of long term ca s 1 m y trends and temporal variability on the basis of a time series hydrography and flux study site in the oligotrophic subtropical north atlantic we interpret the isotopic discrepancies between fine fraction and globigerinoides as resulting primarily from season of calcification as well as possible vital effects we suggest that fine fraction stable isotope values from oligotrophic waters reflect late winter early spring relatively cool nutrient rich shallow mixedlayer conditions during the time of deep mixing i e spring bloom whereas globigerinoides stable isotope values record conditions that prevailed in the stratified surface waters in the warmer late spring fall this implies that paired analyses of fine fraction and surface dwelling planktic foraminiferal n 18 o could be applied to reconstruct paleoseasonality of the open oceans however because the fine fraction n 13 c values are not representative of the annual mean surface water n 13 c we recommend use of near surface dwelling planktic foraminiferal n 13 c as a proxy for n 13 c of stratified surface waters that are more or less in equilibrium with the atmosphere with respect to pco2

temperature δ18o relationships of planktonic foraminifera collected from surface waters abstract most of the isotopic paleotemperature equations used for paleoceanographic reconstructions have been derived from culture experiments or inorganic precipitates of calcium carbonate to test these equations in the modern ocean we measured the oxygen isotope composition of planktonic foraminifera globigerinoides ruber globigerinoides sacculifer globigerina bulloides and neogloboquadrina pachyderma collected from atlantic and southern ocean surface waters and added published plankton tow data from the pacific indian and arctic oceans the resulting species specific regression equations of the temperature 18o relationships for g ruber g sacculifer and g bulloides are statistically indistinguishable the equations derived for g sacculifer and g bulloides agree with relationships obtained from laboratory experiments in which these species were cultured at ph values close to modern surface waters the equation derived from n pachyderma has a significantly lower slope and offset than the other three species but produces a regression equation that is nearly identical to the one for the epifaunal benthic foraminifer cibicides sp our work on plankton tow and pumped samples indicates that culture derived equations appear to be more appropriate for predicting the absolute 18o of the species examined compared to equations derived from inorganic precipitates however over the oceanic temperature range the slopes of the equations we derive for living species agree with the slopes obtained from inorganic precipitates

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

upwelling and productivity along the peru chile current derived from faunal and isotopic compositions of planktic foraminifera in surface sediments abstract we report on the spatial distribution of isotopic compositions of the two planktic foraminifera species globigerina bulloides and neogloboquadrina pachyderma dex and the faunal assemblages of planktic foraminifera in 91 surface sediment samples along the chilean continental slope between 23 s and 44 s both 13c and 18o data of n pachyderma dex show little variability in the study area north of 39 s the isotopic values of n pachyderma dex are heavier than those of g bulloides whereas south of 39 s this relation inverses this is indicative for a change from a well mixed deep thermocline caused by coastal upwelling north of 39 s to well stratified water masses in a non upwelling environment south of 39 s in addition the faunal composition of planktic foraminifera marks this change by transition from an upwelling assemblage north of 39 s to a high nutrient non upwelling assemblage south of 39 s which is characterized by decreased contributions of upwelling indicators such as g bulloides n pachyderma sin and globigerinita glutinata in general we can conclude that food and light rather than temperature are the primary control of the planktic foraminiferal assemblage between 23 s and 44 s off chile our data point to higher marine productivity at upwelling centers north of 25 s and at 30 33 s south of 39 s significant supply of nutrients by fluvial input most likely boosts the productivity

deep dwelling planktonic foraminifera of the northeastern pacific ocean reveal environmental control of oxygen and carbon isotopic disequilibria abstract we assess the utility of four species of living planktonic foraminifera as tracers of thermocline and intermediate water masses in the northern pacific ocean based on their water column distribution and shell isotopic composition assuming oxygen isotopic equilibria with the water column we infer apparent calcification depths this allows an estimate of apparent carbon isotopic disequilibria we then relax the assumption of oxygen isotopic equilibrium to examine habitat effects on kinetic disequilibrium processes in the california current left coiling neogloboquadrina pachyderma and globigerina calida calcify in the upper thermocline globorotalia scitula resides within the shallow salinity minumum potential density 25 1 26 7 while globoquadrina hexagona is associated with the deeper north pacific intermediate water 26 7 26 9 apparent carbon isotopic disequilibria corrected for oxygen isotopic disequilibria range from 1 0 1 9 in these asymbiotic species the carbon isotopic disequilibrium can be modeled as a single exponential function of temperature or a logarithmic function of potential food supply we infer that carbon isotopic disequilibrium increases with metabolic rate related to temperature and or food supply kinetic processes of oxygen and carbon isotopic disequilibria yields reasonable depth habitats if the slope of the oxygen carbon isotopic shift is about 0 35 consistent with culture data our finding of a link between environment metabolism and isotopic disequilibrium observed in oceanic settings suggests the potential to better reconstruct the structure and biological processes of the upper water column from geologic data

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

anaerobic methane oxidation in low organic content methane seep sediments abstract sulfate dependent anaerobic oxidation of methane aom is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps in this study we investigate how the presence of low organic content sediment influences the capacity and efficiency of aom at bullseye vent a gas hydrate bearing cold seep offshore of vancouver island canada the upper 8 m of sediment contains

late palaeozoic to triassic evolution of the turan and scythian platforms the pre history of the palaeo tethyan closure abstract a number of en echelon arranged southwest facing arc fragments of palaeozoic to jurassic ages sandwiched between two fairly straight east northeast trending boundaries constitute the basement of the scythian and the turan platforms located between the laurasian and tethyside units they have until now largely escaped detection owing to extensive jurassic and younger cover and the inaccessibility of the subsurface data to the international geological community these units are separated from one another by linear gently curved faults of great length and steep dip those that are exposed show evidence of strike slip motion the arc units originally constituted parts of a single silk road arc located somewhere south of the present day central asia for much of the palaeozoic although by the late carboniferous they had been united into a continental margin arc south of the tarim basin and equivalent units to the west and east they were stacked into their present places in northern afghanistan turkmenistan caucasus and the northern black sea by large scale right lateral strike slip coastwise transport along arc slicing and arc shaving strike slip faults in the triassic and medial jurassic simultaneously with the subductive elimination of palaeo tethys this gigantic dextral zone the silk road transpression was a trans eurasian structure and was active simultaneously with another similar system the gornostaev keirogen and greatly distorted eurasia the late palaeozoic to jurassic internal deformation of the dniepr donets aulacogen was also a part of the dextral strain in southern europe when the emplacement of the scythian and turan units was completed the elimination of palaeo tethys had also ended and neo tethyan arcs were constructed atop their ruins mostly across their southern parts the western end of the great dextral zone that emplaced the turan and scythian units horsetails just east of north dobrudja and a small component goes along the tornquist teisseyre lineament

structure of the lithosphere below the southern margin of the east european craton ukraine and russia from gravity and seismic data abstract the present study was undertaken with the objective of deriving constraints from available geological and geophysical data for understanding the tectonic setting and processes controlling the evolution of the southern margin of the east european craton eec the study area includes the inverted southernmost part of the intracratonic dnieper donets basin ddb donbas foldbelt df its southeastern prolongation along the margin of the eec the sedimentary succession of the karpinsky swell ks the southwestern part of the peri caspian basin pcb and the scythian plate sp these structures are adjacent to a zone along which the crust was reworked and or accreted to the eec since the late palaeozoic in the bouguer gravity field the southern margin of the eec is marked by an arc of gravity highs correlating with uplifted palaeozoic rocks covered by thin mesozoic and younger sediments a three dimensional 3d gravity analysis has been carried out to investigate further the crustal structure of this area the sedimentary succession has been modelled as two heterogeneous layers mesozoic cenozoic and palaeozoic in the analysis the base of the sedimentary succession top of the crystalline precambrian basement lies at a depth up to 22 km in the pcb and df ks areas the residual gravity field obtained by subtracting the gravitational effect of the sedimentary succession from the observed gravity field reveals a distinct elongate zone of positive anomalies along the axis of the df ks with amplitudes of 100 140 mgal and an anomaly of 180 mgal in the pcb these anomalies are interpreted to reflect a heterogeneous lithosphere structure below the supracrustal sedimentary layers i e moho topography and or the existence of high density material in the crystalline crust and uppermost mantle previously published data support the existence of a high density body in the crystalline crust along the ddb axis including the df caused by an intrusion of mafic and ultramafic rocks during late palaeozoic rifting a reinterpretation of existing deep seismic sounding dss data on a profile crossing the central ks suggests that the nature of a high velocity density layer in the lower crust crust mantle transition zone is not the same as that of below the df rather than being a prolongation of the ddb df intracratonic rift zone the present analysis suggests that the ks comprises at least in part an accretionary zone between the eec and the sp formed after the palaeozoic

cadmium and delta13c paleochemical ocean distributions during the stage 2 glacial maximum changes in heat and salt transport by ocean currents have been implicated in ice age climate cycles weyl 1 968 newell 1 974 broecker et al 1 990b in addition to the direct physical effects of the ocean on climate the ocean carbon system controls atmospheric co2 and the co2 fluctuations documented in ice core bubbles barnola et a1 1 987 neftel et a1 1 988 are thought to be a significant factor in climate oscillations hansen et al 1 984 dramatic changes in oceanic circulation patterns and carbon system chemistry have occurred during the late quaternary glacial interglacial global climate cycles boyle keigwin 1 982 curry lohmann 1 983 shackleton pisias 1 984 boyle keigwin 1 987 duplessy et al 1 988 curry et al 1 988 broecker et al i 990a these changes in the ocean system may be significant driving forces in the progression of ice age co2 cycles toggweiler sarmiento 1 985 ennever mcelroy 1 985 wenk siegenthaler 1 985 boyle 1 988a b broecker peng 1 990 the oceanic distributions of c513c cd and other carbon system linked properties are controlled by the interaction between biological uptake and decomposition with the general circulation of the ocean because records of past oceanic cd and c5 1 3c are preserved in shells of planktonic and benthic foraminifera

the california current of the last glacial maximum reconstruction at 42 n based on multiple proxies multiple paleoceanographic proxies in a zonal transect across the california current near 42 n record modern and last glacial maximum lgm thermal and nutrient gradients the offshore thermal gradient derived from foraminiferal species assemblages and oxygen isotope data was similar at the lgm to that at present warmer offshore but average temperatures were 3 3 1 5 c colder observed gradients require that the sites remained under the southward flow of the california current and thus that the polar front remained north of 42 n during the lgm carbon isotopic and foraminiferal flux data suggests enhanced nutrients and productivity of foraminfera in the northern california current up to 650 km offshore in contrast marine organic carbon and coastal diatom burial rates decreased during the lgm these seemingly contradictory results are reconciled by model simulations of the lgm wind field which suggest that wind stress curl at 42 n and thus open ocean upwelling increased while offshore ekman transport and thus coastal upwelling decreased during the last ice age the ecosystem of the northern california current during the lgm approximated that of the modern gulf of alaska cooling and production in this region was thus driven by stronger open ocean upwelling and or southward flow of high latitude water masses rather than by coastal upwelling

triassic limestone turbidites and serpentinite the cimmeride orogeny in the central pontides the basement of the central pontides and by implication that of crimea consists of pre permian low grade metaclastic rocks intruded by latest permian early carboniferous 305 290 ma granitoids further up in the stratigraphic sequence are triassic limestones which are now preserved as olistoliths in the deformed upper triassic turbidites new conodont and foraminifera data indicate an anisian to carnian middle to late triassic age for these hemi pelagic hallstatt type limestones the siliciclastic turbidites surrounding the triassic limestone contain the norian late triassic bivalve monotis salinaria the same species is also found in the tauric series in crimea the upper triassic flysch in the central pontides is locally underlain by basaltic pillow lavas and includes kilometre size tectonic slices of serpentinite both the flysch and the serpentinite are cut by an undeformed acidic intrusion with an ar ar biotite age of 162 4 ma callovian oxfordian this indicates that the serpentinite was emplaced into the turbidites before middle jurassic time most probably during latest triassic or early jurassic time and that the deformation of the triassic sequence pre dates the middle jurassic regional geological data from the circum black sea region including widespread upper triassic flysch upper triassic eclogites and blueschists of oceanic crustal affinity and apparent absence of a cimmerian continent between the cretaceous and triassic accretionary complexes indicate that the latest triassic cimmeride orogeny was accretionary rather than collisional and is probably related to the collision and accretion of an oceanic plateau to the southern active margin of laurasia

constraining foraminiferal calcification depths in the western pacific warm pool highlights first apparent calcification depth assessment of living foraminifera in the se wpwp deep surface mixed layer causes deep apparent calcification depths deep dwelling g hexagonus traces nutrient conditions in equatorial water masses abstract insight into past changes of upper ocean stratification circulation and nutrient signatures rely on our knowledge of the apparent calcification depth acd and ecology of planktonic foraminifera which serve as archives for paleoceanographic relevant geochemical signals the acd of different species varies strongly between ocean basins but also regionally we constrained foraminiferal acds in the western pacific warm pool manihiki plateau by comparing stable oxygen and carbon isotopes 18ocalite 13ccalcite as well as mg ca ratios from living planktonic foraminifera to in situ physical and chemical water mass properties temperature salinity 18oseawater 13cdic our analyses point to globigerinoides ruber as the shallowest dweller followed by globigerinoides sacculifer neogloboquadrina dutertrei pulleniatina obliquiloculata and globorotaloides hexagonus inhabiting increasing greater depths these findings are consistent with other ocean basins however absolute acds differ from other studies the uppermost mixed layer species g ruber and g sacculifer denote mean calcification depths of 95 m and 120 m respectively these western pacific acds are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region our results indicate that n dutertrei appears to be influenced by mixing waters from the pacific equatorial divergence while p obliquiloculata with an acd of 160 m is more suitable for thermocline reconstructions acds of g hexagonus reveal a deep calcification depth of 450 m in oxygen depleted but nutrient rich water masses consistent to other studies as the 13c of g hexagonus is in near equilibrium with ambient seawater we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra topical regions

shell structure patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells this study investigates 13c and 18o variations in the shells of modern brachiopods representing all extant groups of calcite precipitating brachiopods collected live from 8 locations sem examinations determined the ultrastructural characteristics of each species prior to isotope analyses 13c and 18o analyses of shell carbonate were carried out with samples representing disparate morphological features and ultrastructural shell layers of both ventral and dorsal valves generally 18o values from the fibrous secondary or prismatic tertiary shell layers of the articulated terebratulida and rhynchonellida species were in oxygen isotopic equilibrium with ambient seawater isotopic temperatures extrapolated from these values are close to measured annual mean seawater temperatures 18o values were relatively unaffected by shell specialisation the only exception was antarctic species liothyrella uva which did not have a complete tertiary shell layer typical of this genus and had 18o values of the innermost layer strongly correlated with 13c and mostly not in oxygen isotopic equilibrium with ambient seawater with the exception of the rhynchonellid notosaria nigricans the outer primary layer material was depleted in 13c and 18o and highly variable inclusion of this material even as part of a whole shell sample could lead to misinterpretation of seawater temperature therefore only fossil secondary layer material should be used the anomalous articulated thecideidine brachiopod thecidellina barretti is composed of mainly primary shell material and was not in oxygen isotope equilibrium 18o values from the laminar secondary layer material of the inarticulated craniida are highly variable therefore these species are not recommended for use as palaeoenvironmental proxies this study suggests caution when employing fossil brachiopod shells with similar ultrastructures to modern craniid and thecideidine brachiopods the carbon isotope composition is highly variable in all of the brachiopods studied analysis of samples from specialised regions of the secondary shell layer show a pattern of depletion in 13c relative to non specialised secondary material the carbon isotope variability is independent of 18o and is repeated in most of the articulated species regardless of geographical location this is possibly a vital effect produced by metabolic prioritisation

population dynamics of living planktic foraminifers in the hemipelagic southeastern bay of biscay abstract population dynamics of planktic foraminifer species are discussed in relation to environmental factors across the continental slope onto the shelf of the southeastern bay of biscay along a bathymetric transect from 2000 m to 145 m water depth 154 vertical plankton tows were obtained during different seasons on five cruises between june 2006 and july 2008 the distribution of live specimens 100 m sampled at distinct intervals down to 700 m water depth is compared to changes in temperature salinity and chlorophyll a concentration the overall seasonal variability and depth distribution of species in the hemipelagic southeastern bay of biscay has been similar to open ocean faunas in the pelagic north atlantic each species examined occurred at considerable variability in habitat depth and seasonal distribution the vertical distribution of planktic foraminifer species was mainly driven by the depth of the deep chlorophyll maximum dcm and hence linked to the development of the thermocline the seasonal variation of river discharge could have had differential effects on the distribution of planktic foraminifers and may have inhibited or triggered the production of species low standing stocks at onshore stations in spring and high standing stocks in july both in low saline waters indicate that salinity in itself did not control the distribution of planktic foraminifers instead factors which co vary with salinity such as turbidity and organic matter possibly affected the distribution of planktic foraminifers on a species specific scale in general the distribution of planktic foraminifer species on a seasonal vertical and regional scale along the offshore onshore transect was related to surface water salinity and turbidity and to the availability of food

partial delamination of continental mantle lithosphere uplift related crust mantle decoupling volcanism and basin formation a new model for the pliocene quaternary evolution of the southern east carpathians romania abstract a geodynamic model is proposed for the mid miocene to quaternary evolution of the southern east carpathians in order to explain the relationships between shallow and deep geological phenomena that occurred synchronously during late collision tectonics in this area an active volcanic zone cross cuts since 2 my the suture between the overriding tisza dacia and subducting european continental plates mafic calc alkaline and alkaline magmas south harghita and persani volcanoes erupted contemporaneously these magmas were supplied by partial melting of the mantle lithosphere of the subducting and not of the overriding plate in an effort to decipher this geodynamically a typical setting of magma generation the spatial and temporal distribution of shallow and deep phenomena was successively examined in order to establish the degree of their interdependence our model indicates that intra mantle delamination of the subducting european plate is the principal cause of a succession of events it caused upwelling of the hot asthenosphere below a thinned continental lithosphere of the carpathians inducing the uplift of the lithosphere and its internal decoupling at the moho level by isostatic and mostly thermal effects during this uplift the crust deformed flexurally whilst the mantle deformed in a ductile way this triggered decompressional partial melting of the uppermost mantle lithosphere flexural deformation of the crust induced its fracturing allowing for the rapid ascent of magmas to the surface as well as reactivation of an older detachment horizon at the base of the carpathian nappe stack above which the brasov ciuc and gheorghieni hinterland basins formed by extension and gravity spreading the rapid subsidence of the focsani foreland basin is controlled by the load exerted on the lithosphere by the delaminated mantle slab that is still attached to it in this model crust mantle decoupling magma genesis and volcanism local near surface hinterland extension are consequences of uplift induced by asthenospheric upwelling triggered by intra mantle delamination this model enables to conceive that delamination induced decoupling began to be efficient 9 4 my ago at the northern end of the east carpathians when the mantle slab dipped westwards since then intra mantle delamination migrated laterally normal to the slab strike and follows the arcuate shape nw se sw of the carpathians nowadays whereas the mantle slab is still actively foundering below the vrancea seismic zone to the se of the most recent volcanic area south harghita persani a significant southwestward shift of the delamination process can be discerned

triassic volcanism in the eastern fore caucasus evolution and geodynamic interpretation abstract the aim of this paper is to describe the triassic regional geodynamic framework of the eastern fore caucasus area from data on volcanics and related sedimentary deposits these deposits only known by drilling represent the lowermost horizons of a slightly deformed mesozoic and cenozoic cover and rest unconformably on folded mainly devonian to carboniferous series they are thought to be for the most part postcollisional the sedimentary record of early to middle triassic evolution allows visualisation of uplift events associated with continental basin formation preceding and following the opening of a deep passively subsiding marine basin tectonic instability indicated by tilted strata prevailed throughout the whole period the subsidence maximum corresponding with a total immersion below sea level occurred during the olenekian early triassic during middle triassic times the area was continuously uplifted and progressively emerged to become strictly continental with a fluvio lacustrine sedimentation during the late triassic two periods of intense volcanic activity occurred during early middle and late triassic times the former comprises 1 subaerial explosive eruptions of rhyolitic magma the vents of which are presumably located about 50 100 km southwest of the study area and 2 submarine effusive eruptions of basalts and rhyolites within an actively subsiding trough the numerous unconformities within the volcano sedimentary sequence testify to a tectonically active setting during the late triassic eruptions were subaerial mainly explosive nuees ardentes and rhyo dacitic basaltic and andesitic lava flows and domes were minor in both eruptive periods mafic magmas had a calc alkaline affinity and their diversity would have been the result of partial melting of a heterogeneous metasomatized subcontinental mantle several compositional gaps within the acidic group reflect melting of distinct components of the continental crust fractional crystallisation or even partial melting trends can be deciphered within mafic and rhyolitic groups the geodynamic background of early middle triassic volcanism was one of extension the precise nature of the extension is unclear but could include active rifting back arc extension or even transtension in a strike slip fault zone with their great contribution of felsic rocks about 90 the late triassic subaerial volcanics can trace an important crustal partial melting event they could belong to an overheated zone of an andean type volcanic belt

temperature dependent remineralization and carbon cycling in the warm eocene oceans metabolic rates in heterotrophic bacteria are more sensitive to temperature than rates of primary production e g lopez urrutia et al 2006 regaudie de gioux and duarte 2012 consequently faster bacterial respiration rates in a warmer ocean may result in more efficient remineralization of sinking organic matter higher in the water column with implications for carbon and nutrient cycling during warm climate states this is supported by a series of reconstructed 13cdic depth profiles based on well preserved planktonic foraminifera assemblages from tanzania from the warm eocene epoch 55 5 33 7 ma when global surface and deep ocean temperatures exceeded those of the modern day john et al 2013 these results indicate relatively sharp 13cdic gradients in the upper water column which supports the hypothesis that high metabolic rates in warm eocene oceans led to more efficient recycling of organic matter and reduced burial rates of organic carbon olivarez lyle and lyle 2006 shallower remineralization depths would also cause an upward displacement and intensification of the oxygen minimum zone which is consistent with evidence for a pelagic ecosystem that was focused in a narrow depth range near the surface during the warm early and middle eocene here we use the earth system model cgenie that incorporates a new temperature dependence of remineralization rates to illustrate the potential effects of temperature on particulate organic carbon fluxes and hence vertical 13cdic gradients modeled 13cdic vertical profiles off the coast of tanzania for the eocene agree well with the reconstructed 13cdic profiles supporting our interpretations based on temperature dependent remineralization

controls on stable isotope and trace metal uptake in neogloboquadrina pachyderma sinistral from an antarctic sea ice environment article the polar foraminifera neogloboquadrina pachyderma sinistral dominates assemblages from the high latitude southern ocean which plays a key role in determining past climate due to the tight linkage between antarctic temperature and atmospheric co2 here we use n pachyderma s harvested from sediment traps off the west antarctic peninsula to construct a seasonal time series for the calibration of calcite proxies in a high latitude seasonal sea ice environment where temperature is decoupled from other environmental parameters we have used a combination of 18 ocaco3 and 13 ccaco3 to decipher the calcification temperature and salinity which reflect that n pachyderma s live in surface waters throughout the year and at the ice water interface in austral winter further our results demonstrate that the uptake of trace metals into n pachyderma s calcite is influenced by secondary environmental conditions in addition to temperature during periods of sea ice cover we propose an elevated carbonate ion concentration at the ice water interface resulting from biological utilisation of co2 could influence calcification in foraminifera our calculations suggest that for n pachyderma s mg ca sr ca ratios and li ca ratios are linear functions of calcification temperature and co3 2 n pachyderma s mg ca ratios exhibit temperature sensitivity similar to previous studies 10 20 c and a sensitivity to co3 2 of 1 mol kg 1 sr ca ratios are less sensitive to environmental parameters exhibiting 5 increase c and 0 5 10 mol kg 1 the relationship between li ca ratios and both temperature and co3 2 is less significant with 10 increase in li ca ratio c and 10 mol kg 1 we show how a multi proxy approach could be used to constrain past high latitude surface

oxygen isotope ecology of recent planktic foraminifera at the central walvis ridge se atlantic 1 above the walvis ridge in the se atlantic ocean we collected living plantkic foraminifera from the upper water column using depth stratified plantkon tows the oxygen isotope composition 18oc in shells of foraminifera and shell concentration profiles show seasonal and depth habitats of individual species the tow results are compared with the average annual deposition 18oc from sediment traps and the interannual average 18oc of fossil specimens in top sediments at the same site the species globigerinita glutinata best reflects the austral winter spring sea surface temperature sst its 18oc signal in top sediments remains pristine in contrast tow results also show that globigerinoides ruber continues to calcify below the surface mixed layer sml i e down to the deep chlorophyll maximum dcm hence its 18oc signature of exported specimens reflects the sst only when sml incorporates the dcm deep tow and sediment trap results show that both globorotalia truncatulinoides and globorotalia inflata record the temperature between 150 and 350 m depending on the season and the shell size however for all fossil taxa in sediments apart from globigerinita glutinata we observe a positive 18oc shift with respect to the sediment trap and plankton tow values likely related to the interannual flux changes and deep encrustation

isotopic composition and morphology of living globorotalia scitula a new proxy of sub intermediate ocean carbonate chemistry abundance isotopic composition and morphological imprints of the planktonic foraminifera globorotalia scitula brady were closely examined for possible use as a novel reconstruction tool of chemical environments in sub intermediate depth seawater in the past based on the mocnes plankton tow observation of dwelling depths of g scitula and the isotopic compositions together with hydrochemistry data the empirical relations between isotopic disequilibria in carbon 13c 13cg scitula 13cdic and oxygen 18o 18og scitula 18ow isotopes in the carbonate tests and the seawater 18o and 13c of dissolved inorganic carbon dic respectively are introduced the morphological information such as pore density and porosity is also examined for significant relations to carbonate chemistry shell porosity is strongly correlated saturation state of calcite the dissolution of living g scitula tests may promote the observed isotopic differences as well as the increases in porosity 18o of g scitula is found effectively to be linear function of both water temperature and calcite saturation state and thereby temperature equation for g scitula is provided while 13c of g scitula is a linear function of only calcite saturation state the equation was validated by using globorotalia scitula collected by a sediment trap in intermediate water depths satisfactory agreements were found between observed and calculated 18o from the empirical equations based on temperature and hydrochemistry data at sediment trap deployment site indicating that the equation may be useful in paleo environmental reconstruction of sub intermediate water the sediment trap observation further suggests that the abundance of g scitula does not necessarily correspond to surface water productivity and to poc flux but instead it correlates well with the supply of fine organic matter which appears to be a result of water convection thus g scitula may be an unambiguous and excellent paleo environmental recorder for carbonate chemistry and for fine organic matter transport to the depths if isotopic and morphological observations are combined