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

palaeoceanographic and environmental changes in the eastern fram strait during the last 14 000 years based on benthic and planktonic foraminifera abstract benthic and planktonic foraminifera stable isotopes and other geochemical and sedimentological parameters have been investigated in a sediment core from vestnesa ridge 79 n nw svalbard margin 1300 m water depth in order to reconstruct the palaeoceanographic and palaeoenvironmental evolution of the eastern fram strait during the last 14 000 years our multiproxy data and in particular our high resolution benthic foraminiferal record allow a detailed reconstruction of the intermediate water flow in the eastern fram strait during the bolling allerod warm interstadials the high proportion of the benthic atlantic species cassidulina neoteretis suggests the presence of chilled atlantic derived water at the bottom of the vestnesa ridge while the dominance of the polar planktonic species neogloboquadrina pachyderma s indicates cold polar surface conditions during the younger dryas cold stadial the inflow of atlantic derived water was weakened and of lower temperature compared to the previous interval as suggested by the increase in the glacio marine indicator cassidulina reniforme and the lower percentages of c neoteretis after 11 000 cal yr bp the abrupt increase in relative abundance of the benthic species cibicides wuellerstorfi and oridorsalis umbonatus indicates a shift to interglacial conditions with deep convection and generation of cold intermediate water warm surface water conditions were finally established at about 10 300 cal yr bp when turborotalita quinqueloba became the dominant planktonic species generally warmer conditions than today were recorded in the middle holocene with a mild cooling at about 8200 cal yr bp and a more pronounced cool interval with an abrupt decrease in t quinqueloba between 7000 and 6200 cal yr bp cold climatic conditions were established around 4100 cal yr bp when n pachyderma s became again the dominant species and the polar benthic species cribroelphidium excavatum appeared

changes in the water column structure and paleoproductivity in the western south atlantic ocean since the middle pleistocene evidence from benthic and planktonic foraminifera abstract based on an integrated approach planktonic and benthic foraminifera and stable isotopes carried out in two cores collected on continental slope of santos basin central brazil the paleoceanographic oscillations of the last 570 ka are documented benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show 100 ky long term oscillation in the superficial productivity along the middle pleistocene these long term oscillations are interrupted by 30 ky short term changes that mark the transition periods of higher productivity 425 400 ka and 190 160 ka and lower 290 260 ka the planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus opportunist benthic taxa epistominella exigua and alabaminella weddellensis

a late glacial early holocene multiproxy record from the eastern fram strait polar north atlantic the paleoceanographic development of the eastern fram strait during the transition from the cold late glacial and into the warm early holocene was elucidated via a multiproxy study of a marine sediment record retrieved at the western svalbard slope the multiproxy study includes analyses of planktic foraminiferal fauna bulk sediment grain size and caco3 content in addition to mg ca ratios and stable isotopes delta c 13 and delta o 18 measured on the planktic foraminifer neogloboquadrina pachyderma furthermore paleosubsurface water temperatures were reconstructed via mg ca ratios ssst mg ca and transfer functions ssst transfer enabling comparison between the two proxies within a single record the age model was constrained by four accelerator mass spectrometry ams c 14 dates from 14 000 to 10 300 cal yr b p n pachyderma dominated the planktic fauna and cold polar sea surface conditions existed the period was characterized by extensive sea ice cover iceberg transport and low subsea surface temperatures ssst transfer similar to 2 1 degrees c ssst mg ca similar to 3 5 degrees c resulting in restricted primary production atlantic water inflow was reduced compared to the present day and likely existed as a subsurface current at ca 10 300 cal yr b p atlantic water inflow increased and the arctic front retreated north westward resulting in increased primary productivity higher foraminiferal fluxes and a reduction in sea ice cover and iceberg transport the fauna rapidly became dominated by the subpolar planktic foraminifer turborotalita quinqueloba and summer ssst transfer increased by similar to 3 5 degrees c concurrently the ssst mg ca recorded by n pachyderma rose only similar to 0 5 degrees c from ca 10 300 to 8600 cal yr b f the average ssst mg ca and ssst transfer were similar to 4 0 degrees c and similar to 55 degrees c respectively the relatively modest change in ssst mg ca compared to ssst transfer can probably be tied to a change of the main habitat depth and or shift in the calcification season for n pachyderma during this period

changes in planktic foraminiferal faunas temperature and salinity in the gulf stream during the last 30 000 years influence of meltwater via the mississippi river abstract variations in the distribution of planktic foraminiferal faunas temperature and salinity in the surface water of the gulf stream during the last 30 000 years have been reconstructed based on a sediment core from the blake ridge subtropical western atlantic ocean temperatures and salinities were calculated using planktic foraminiferal transfer functions and previously published oxygen isotope values productivity was estimated using the 106 m size fraction of planktic foraminifera the reconstructed values show that temperature variations have been small during the investigated period with a total range of only 3 c the highest temperatures about 1 5 c above the present temperature in the area occurred during the late glacial heinrich event 1 and the mid holocene time periods the lowest temperatures about 1 5 c below the present temperatures occurred during the bolling interstadial the early holocene period was relatively cool the low temperatures during the bolling interstadial and during the early holocene are in contrast to the northeastern atlantic where the bolling interstadial was the warmest period of the deglaciation and the early holocene the warmest during the holocene we attribute the lower temperatures during the bolling and early holocene periods to colder meltwater from the laurentide ice sheet flowing into the gulf of mexico through the mississippi river system and carried to the blake ridge via the gulf stream

signature of the brazil malvinas confluence argentine basin in the isotopic composition of planktonic foraminifera from surface sediments we explored the potential to use the stable isotopic compositions of planktonic foraminifera as a proxy for the position of the brazil malvinas confluence bmc in the argentine basin for this purpose we measured the oxygen and carbon isotopic compositions of globigerinoides ruber pink and white varieties measured separately globigerinoides trilobus globigerina bulloides globorotalia inflata and globorotalia truncatulinoides left and right coiling forms measured separately from a latitudinal transect of 56 surface sediment samples from the continental slope off brazil uruguay and argentina between 20 and 48 s lowest oxygen isotopes values were found in g ruber pink followed by g ruber white and g trilobus reflecting the highly stratified near surface water conditions north of the bmc globigerina bulloides was present mainly south of the bmc and records subsurface conditions supporting earlier plankton tow studies globorotalia inflata and g truncatulinoides left and right were both available over the whole transect and calcify in the depth level with the steepest temperature change across the bmc accordingly the 18 o of these species depict a sharp gradient of 2 at the confluence with remarkably stable values north and south of the bmc our data show that the oxygen isotopic composition of g inflata and g truncatulinoides left and right are the most reliable indicators for the present position of the bmc and can therefore be used to define the past migration of the front if appropriate cores are available

planktic foraminifera from the southwestern atlantic 30 60 s species specific patterns in the upper 50 m abstract planktic foraminifers were studied in 96 samples collected in the southwestern atlantic 30 60 s along 53 w in november 1993 mainly from depths between 0 and 50 m very high proportions of juveniles unidentified were present throughout the area especially north of 37 s where they accounted for up to 70 80 of all shells recorded for most species no clear vertical specific stratification was detected in the 0 50 m layer zoogeographic grouping of the 18 species identified allowed the defining of 5 distinct zones along the transect subtropical north of 31 s 80 warm water individuals warm transitional 34 37 s 35 warm water transitional 37 49 s 99 cold water subantarctic 49 55 s 100 cold water and antarctic south of 56 s 100 cold water boundaries between foraminiferal assemblage zones are in good agreement with hydrological fronts described for the area comparison of the present data with planktic collections from the north atlantic show large differences in the proportions of various taxa in the 14 24 c range g bulloides is much more abundant in the northern hemisphere than in the southern one whereas g quinqueloba g inflata and g rubescens show the opposite trend on the other hand temperature related percentage contributions within the 14 24 c range indicate that the preferred thermic regimes of the 9 species considered are remarkably similar in the north and south atlantic collections compared the southernmost planktic distributional ranges of selected warm water taxa are roughly coincident with those established previously on the basis of surface sediments disagreements being chiefly attributable to selective dissolution on the bottom in contrast at the bottom percentages of cold water foraminifers g bulloides g pachyderma are significantly enhanced with respect to their planktic populations and their sedimentary northward limits extend well beyond their maximum ranges in the upper layer plankton it is suggested that submergence of these cold water species and northward displacement at subsurface depths is chiefly responsible for the mismatching patterns observed dissimilar species proportions in both hemispheres and plankton sediment uncoupling can conceivably engender erroneous conclusions when distributional data are used for paleoecologic reconstructions with the aid of numerical analyses such as the imbrie kipp transfer function technique

are productivity and stratification important to sapropel deposition microfossil evidence from late pliocene insolation cycle 180 at vrica calabria we present the results of a micropaleontological study performed on the sapropel sequence associated with insolation cycle 180 from the plio pleistocene vrica sequence calabria italy we performed a high resolution study on the 3 38 m thick layer c from a core drilled close to the classical outcrop section in which we analyze fluctuations in the abundance and composition of calcareous nannofossils and planktic and benthic foraminifera changes in the fossil assemblages reveal at least three major paleoenvironmental phases in layer c the base of the sapropel contains an abrupt decrease in benthic fauna that continues through all of layer c it also has an increase of the coccolithophorids species coccolithus pelagicus planktic foraminifera show at the same depth a peak of the cold species globorotalia scitula these changes are followed by decreases in the carbonate preservation index and in abundances of globigerinita glutinata globigerinita uvula and neogloboquadrina pachyderma sinistral which suggest cold and highly productive upwelling waters a short interval in the middle of the sapropel is characterized by low values of c pelagicus a fluctuating increase of pseudoemiliania lacunosa and among the foraminifera an increase of globigerinoides ruber together with the presence although decreased of g glutinata g uvula and n pachyderma sinistral we interpret these features as suggesting high seasonality with warm stratified and probably oligotrophic waters during summer and relatively cold conditions during winter finally the topmost interval of the vrica layer c exhibits the re appearance of p lacunosa together with abundant siliceous phytoplankton planktic microfauna show the disappearance of the cold species g glutinata g uvula and n pachyderma sinistral thus this interval appears to be characterized by warmer temperature the transition from the laminated to the massive sediment displays a sequence of events including a decrease of the carbonate preservation index and peaks of globorotalia inflata and g scitula suggesting again upwelling and mixing of the whole water column and thus transition to the oxygenated conditions characterizing the massive layer neither increased productivity nor stratification appear to characterize the whole sapropel interval which is however always dysoxic

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

the sedimentary record of pelagic biogeography abstract sedimentary remains of fossilizable marine organisms chiefly microplanktonic ones coccolithophorids silicoflagellates diatoms dinoflagellates radiolarians foraminifers have long been used for biogeographic surveys usually with the aim of unravelling paleoenvironmental settings utilization of bottom deposits rather than plankton samples has some advantages for this purpose thanatocoenoses require smaller sample sizes materials are more readily available and they eliminate the small time scale variability which obscures long term trends on the other hand the sedimentary imprint of planktonic distributional patterns is often severely distorted by fragmentation and dissolution of the biogenic remains reworking of sediments winnowing and lateral advection of shells especially toward lower latitudes seasonally and interannually variable output rates and the integration of vertically heterogeneous assemblages the biases derived from these processes are reviewed and the need for more information on selective dissolution vertical distribution patterns and planktonic reproduction and output rates is stressed given the assumptions used in paleoenvironmental studies distributional information drawn from sediment samples is less prone to yielding biased information when applied to these surveys than to bio or paleobiogeographic investigations albeit the former can also be significantly affected as a result of changes in the traits that govern the formation of biogenic sediments

distribution of rare earth elements and oxyhydroxide phases within a weathered felsic igneous profile in hong kong abstract variation in type and abundance of oxyhydroxide phases and the fractionation of rare earth elements ree within a weathered felsic pyroclastic profile in hong kong were investigated in order to assess the key factors and micro environmental conditions controlling their distribution during weathering at rock and mineral scales three types of oxyhydroxide phases fe mn and ce rich were recognized based on their most abundant elements the fe rich types appeared in all samples at different stages of weathering the mn rich types however were limited to samples at advanced stages of weathering while the ce rich types were found solely in samples from oxyhydroxide rich zones fractionation of ree likely started at the early stages of weathering but became evident only at the advanced stages characteristics of ree patterns especially the direction negative or positive and extent of ce anomalies correlated very well with the appearance and abundance of mn oxyhydroxides and were attributed to the co existence of distinct micro environmental conditions within the profile these conditions resulted from two major competing processes leaching and fixation and oxidation precipitation and reduction dissolution which operated simultaneously within the profile at any given stage of weathering

paleoproductivity from benthic foraminifera abundance glacial to postglacial change in the west equatorial pacific surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep sea floor as a rule of thumb for each 1 mg of organic carbon arriving at the sea floor one benthic foram shell 150 m is deposited the correlation can be used to reconstruct organic flux to the sea floor in the past and hence the productivity of past oceans applying the appropriate equations to box core data from the ontong java plateau in the western equatorial pacific we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1 5 and 2 0 with intermediate values for the mid transition period accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period presumably because increased winnowing removed part of the food supply

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

calcareous dinoflagellate cysts in south and equatorial atlantic surface sediments diversity distribution ecology and potential for palaeoenvironmental reconstruction several marine peridiniphycidean dinoflagellate species produce calcareous cysts during their life cycle which are relatively resistant to chemical and physical degradation and are therefore often found in large quantities in oceanic bottom sediments although the use of these calcareous cysts as proxies for palaeoenvironmental and palaeoclimatic reconstructions has seen many advances over the last decade until now only relatively patchy and regional information was available on their recent distribution patterns and ecology especially at the species level in this paper comprehensive calcareous cyst diversity and distribution data have been compiled from published and unpublished work for 167 south and equatorial atlantic ocean surface sediments ranging from 20 n to 50 s and 30 e to 65 w the main aim has been to focus on the complex often non linear relationships between individual species distributions and the physicochemical and trophic conditions of the overlying sub surface waters through the use of x y graphs of cyst abundance vs sub surface water environmental parameters and detrended correspondence analyses ten cyst species and the calcareous vegetative coccoid species thoracosphaera heimii were observed in the bottom sediments each species showing its own characteristic distribution pattern in relation to the environmental conditions of the upper water masses above them e g sea surface temperature productivity stratification the sensitive reactions of various species to unique combinations of environmental parameters shows that each species has its own specific ecological traits thus rejecting the bundled use of calcareous cyst accumulation as a general proxy for oligotrophy or stratification in future palaeoenvironmental analyses the acquired reference data set of this study is large and diverse enough to allow its future application in quantitative palaeoenvironmental reconstruction models and shows that there is still an enormous reconstruction potential concealed in many fossil calcareous dinoflagellate cyst assemblages

in situ calibration of mg ca ratio in planktonic foraminiferal shell using time series sediment trap a case study of intense dissolution artifact in the south china sea this study examines mg ca temperature equations through the use of planktonic foraminifers collected from continuous time series sediment traps at four water depths in the south china sea this deployment provides an opportunity to refine partial dissolution artifacts and to identify responses of shell chemistry to changes in ambient seawater conditions paired mg ca and 18o measurements on shells are strongly correlated with seasonal variability in terms of temperature at specific habitat depths however partial dissolution can significantly alter mg ca ratios even at depths well above the calcite lysocline or carbonate compensation depth of the three species studied neogloboquadrina dutertrei is the most sensitive species to dissolution relative to the other surface dwelling species globigerinoides ruber and globigerinoides sacculifer differences between the mg derived temperature equation here and those from previously established core top or sediment trap calibrations can be attributed to various degrees of dissolution and lateral advection thus highlighting the need for in situ empirical calibration for different ocean basins

sea surface temperature reconstruction of the quaternary western south atlantic new planktonic foraminiferal correlation function abstract we provide a new multivariate calibration function based on south atlantic modern assemblages of planktonic foraminifera and atlas water column parameters from the antarctic circumpolar current to the subtropical gyre and tropical warm waters i e 60 s to 0 s therefore we used a dataset with the abundance pattern of 35 taxonomic groups of planktonic foraminifera in 141 surface sediment samples five factors were taken into consideration for the analysis which account for 93 of the total variance of the original data representing the regional main oceanographic fronts the new calibration function f141 35 5 enables the reconstruction of late quaternary summer and winter sea surface temperatures with a statistical error of 0 5 c our function was verified by its application to a sediment core extracted from the western south atlantic the downcore reconstruction shows negative anomalies in sea surface temperatures during the early mid holocene and temperatures within the range of modern values during the late holocene this pattern is consistent with available reconstructions

seasonal succession vertical distribution and dissolution of planktonic foraminifera along the subarctic front implications for paleoceanographic reconstruction in the northwestern pacific abstract the regional spatial and depth distribution of planktonic foraminifera were studied through sediment trap observations at two stations stations wct 5 about 41 n 150 e and wct 6 about 42 n 155 e along the subarctic front in the northwestern pacific ocean the sediment traps were moored at 1000 and 4500 m depths at station wct 5 and 1091 2051 and 4871 m depths at station wct 6 the samples were collected from 17 august 1998 to 10 august 1999 at station wct 5 and from 15 august 1999 to 6 august 2000 at wct 6 at station wct 5 two distinct annual periods of increased total foraminiferal and species production were evident the period of highest production was in autumn with a secondary period in early summer at station wct 6 high total foraminiferal shell fluxes occurred in april may and september october the april may spring bloom of planktonic foraminifera apparently began each year as the sea surface temperature sst increased after winter and the decrease of thickness of the mixed water layer during june july in every year following the cessation of bloom the most common foraminiferal species in the study region were globigerina quinqueloba neogloboquadrina pachyderma neogloboquadrina dutertrei neogloboquadrina incompta globigerinita glutinata globigerina bulloides globigerina falconensis globorotalia theyeri globorotalia scitula and globigerinella calida foraminiferal fluxes displayed a distinct seasonality at all trap depths at both stations at station wct 5 in 1998 1999 foraminiferal species were scarce in the surface water during spring and summer and the dominant foraminiferal species were most productive during winter and autumn at station wct 6 the dominant foraminiferal species were most productive during late winter to spring and all species showed a peak in middle spring may a comparison of seasonal patterns of dominant foraminiferal species between the northwestern and northeastern pacific demonstrated that foraminiferal productivity was a good proxy for sea surface temperature and mixing of water column significant dissolution of foraminiferal tests was evident in the deepwater column and was used to estimate the foraminiferal lysocline depth 4500 m in the northeastern pacific basin

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

alkenone temperature anomalies in the brazil malvinas confluence area caused by lateral advection of suspended particulate material alkenone temperatures derived from suspended particulate organic material which was collected in austral summer 2001 from surface waters 5 m south of the brazil malvinas confluence deviate from measured temperatures by 4 to 7 c when uk 37 ratios are converted to temperature using the muller et al 1998 calibration and up to 3 c when using the calibration of conte et al 2006 in contrast alkenone temperatures determined from particulate material sampled north of the confluence reveal close correspondence to in situ temperatures or show slightly higher values we suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing malvinas current whereas the northern samples carry an uk 37 signal of tropical subtropical origin transported southward with the brazil current on the basis of surface ocean transport pathways and velocities simulated with the large scale geostrophic lsg ocean general circulation model we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents

planktonic foraminifera in the sediment of a western boundary upwelling system off cabo frio brazil abstract the distribution of planktonic foraminifera in box core tops under the influence of a western boundary upwelling system along the southeastern brazilian continental margin was examined to evaluate the similarity percentage simper and to create a biofacies model for paleoenvironmental applications species associated with warm and oligotrophic water were distributed in the rio de janeiro sector of the campos basin while productive water species were most abundant in the rio de janeiro sector of the santos basin and cold water species were most abundant in the cabo frio upwelling system cfus four major biofacies are associated with the oceanographic setting of the cfus one from the campos basin a brazil current front one from the santos basin b mixture of coastal and oceanic waters and two associated with the cabo frio high in the northern biofacies c and southern biofacies d the distribution of biofacies c and d was associated with temperature differences biofacies c represents a mixture of upwelling and tropical waters while biofacies d represents a mixture of cold nutrient rich and santos basin waters these biofacies were also defined in core cf10 01b in which six main paleoceanographic phases were characterized during the last 9 cal kyr predominantly showing alternating dominance between biofacies c and d from 9 0 to 5 0 cal kyr before the present bp the system was dominated by biofacies c between 4 0 and 3 5 cal kyr bp biofacies d was dominant between 3 5 and 2 5 cal kyr bp a strong influence of coastal waters and weakened upwelling activity were indicated by the dominance of biofacies b c d the last 2 5 cal kyr was dominated by biofacies d the sst in this core was reconstructed using the modern analog technique mat which revealed 0 35 c of variability indicating no sst changes during the holocene the weak sensitivity of the mat was due to the interplay among different oceanographic features

thermohaline fronts and baroclinic flow in the argentine basin during the austral spring of 1984 thermohaline fronts structure and baroclinic flow in the central argentine basin are investigated on the basis of a 1984 field experiment the brazil current after initial overshoot meanders northeastward toward subtropical latitudes with speeds of the order of 0 3 m s 1 the meanders have a wavelength of about 400 km and an amplitude of 200 km brazil current signatures as expressed by dynamic height are recognizable to depths of several kilometers the brazil and antarctic circumpolar currents do not meet in the central argentine basin to form common eastward flow as was expressed in classical descriptions but instead diverge sharply near 42 w this is seen also in the trajectories of satellite tracked drifters the region between the currents is marked by cyclonic and anticyclonic eddies strong thermohaline fronts accompany the boundaries of these currents the brazil current and subantarctic fronts are well separated in the central basin brazil current density fronts are deep and extend from the surface to 3000 m while the associated temperature and salinity fronts are intermittent over this depth interval temperature fronts virtually vanish at the interface between the antarctic intermediate water and the north atlantic deep water salinity fronts reverse their polarity beneath the core of the former at depths between 3000 and 4000 m abyssal temperature and salinity fronts are observed which are largely density compensating at the subantarctic and cold core eddy fronts horizontal temperature and salinity gradients in the upper mixed layer compensate each other in such a way that no density front is found deep subpycnocline mixed layers occur in the poleward lobes of the brazil current during austral spring suggestive of previous winter convection

regional and interannual productivity of biogenic components and planktonic foraminiferal fluxes in the northwestern pacific basin abstract time series sediment trap experiments at subtropical wct 1 and subarctic wct 2 stations in the northwestern pacific indicate seasonal latitudinal and depth variations in total particulate biogenic and foraminiferal fluxes at the subtropical station the average total mass flux was 19 4 mg m 2 day 1 in the shallow trap 1060 m and 21 5 26 1 mg m 2 day 1 in the deep trap 3930 m during the sampling period at subarctic station these values were 91 5 176 9 mg m 2 day 1 in the shallow and 68 6 112 3 mg m 2 day 1 in the deep trap we recognized 12 and 15 planktonic foraminiferal species at station wct 1 and station wct 2 respectively the planktonic foraminiferal flux and species turnover are related to seasonal and interannual changes in source water and water column conditions at both stations at station wct 1 the highest flux was recorded during the summer with a peak in mid to late june associated with similar flux patterns of the dominant species globigerinoides ruber and globigerinita glutinata the total flux of foraminiferal tests at the shallow and deep traps is similar in numbers and magnitude at station wct 2 the peaks of total flux of foraminiferal tests at the two trap depths differ in number and their magnitude in the deep trap is almost half of that in the shallow trap a distinctive seasonal pattern occurred in the shallow and the deep trap with a peak in total foraminiferal flux in mid june to mid july globigerina quinqueloba neogloboquadrina pachyderma and neogloboquadrina dutertrei dominate the planktonic population throughout the year subtropical station wct 1 was characterized by low total foraminiferal fluxes and low total mass flux which is dominated by calcium carbonate and depleted in opal whereas high foraminiferal fluxes and a high total mass flux dominated by high biogenic opal and less calcium carbonate and organic matter characterize subarctic station wct 2 the foraminiferal carbonate that reaches the seafloor accounts for an average 20 27 and 22 23 of the total calcium carbonate at station wct 1 and station wct 2 respectively the primary reason for the difference in flux at both stations thus lies in the different contributions of siliceous and calcareous planktonic assemblages the seasonal variation in biogenic particulate flux at both stations implies that temporal changes in biological productivity are governed by large scale seasonal climatic variability and local hydrography

paleoceanographic evolution of the sw svalbard margin 76 n since 20 000 14c yr bp abstract two cores from the southwestern shelf and slope of storfjorden svalbard taken at 389 m and 1485 m water depth have been analyzed for benthic and planktic foraminifera oxygen isotopes and ice rafted debris the results show that over the last 20 000 yr atlantic water has been continuously present on the southwestern svalbard shelf however from 15 000 to 10 000 14c yr bp comprising the heinrich event h1 interval the bolling allerod interstades and the younger dryas stade it flowed as a subsurface water mass below a layer of polar surface water in the benthic environment the shift to interglacial conditions occurred at 10 000 14c yr bp due to the presence of a thin upper layer of polar water surface conditions remained cold until ca 9000 14c yr bp when the warm atlantic water finally appeared at the surface neither extensive sea ice cover nor large inputs of meltwater stopped the inflow of atlantic water its warm core was merely submerged below the cold polar surface water

glacial deep water properties in the west equatorial pacific bathyal thermocline near a depth of 2000 m abstract the stable isotope stratigraphy of planulina wullerstorfi in three box cores from ontong java plateau in the western equatorial pacific shows that there existed a bathyal thermocline near the depth of 2000 m during glacial time waters below the boundary were colder by about 1 c those above were about the same as now the deep waters were slightly enriched and the upper waters depleted in nutrients compared with present values the differences in 13 c to the present after correcting for the global change are of the order of 0 1 more positive above 2000 m and 0 1 more negative below corresponding to changes in phosphate of the order of 0 1 mol kg less phosphate above and more below the boundary

some paleomagnetic constraints on the tectonic evolution of the coastal cordillera of central chile paleomagnetic samples collected from 19 sites in radioisotopically dated jurassic mafic dykes and plutons in the coastal cordillera of chile between latitude 32 15 and 33 30 s yield paleomagnetic poles calculated by averaging the virtual geomagnetic poles from approximately coeval sites at latitude 85 9 s longitude 36 7 e n 8 a95 11 9 for sites dated at close to 170 ma and at latitude 80 3 s longitude 207 8 e n 10 a95 9 5 for sites dated at close to 145 ma these paleomagnetic poles from the coast of chile coincide with poles from coeval sequences within the south american craton some of the igneous rocks that constitute these sampling sites crosscut a high grade metamorphic complex that is distinct from other segments of the coastal cordillera in age structural style and metamorphic grade this complex cannot be correlated with metamorphic rocks anywhere else in central western south america and could be considered a potentially exotic allochthonous terrane if this terrane has been added to the western south american margin then accretion occurred prior to 170 ma paleomagnetic results presented here indicate that no major rotation or large scale latitudinal translation of crustal blocks has taken place in this part of central chile since middle jurassic time