characterisation of ottnangian middle burdigalian palaeoenvironments in the north alpine foreland basin using benthic foraminifera a review of the upper marine molasse of southern germany abstract considerable facies changes and varying foraminiferal assemblages have been described from the lower miocene sediments of the upper marine molasse in the north alpine foreland basin of southern germany and have resulted in the distinction of a western molasse and eastern molasse however the causes and processes leading to these local differences have largely remained unexplored to date the aim of this study is to explore possible explanations in order to better understand the palaeogeographic stratigraphic and environmental setting the study focuses on the ottnangian middle burdigalian segment of the upper marine molasse in southern germany and includes a review of previously published data together with new data from the borehole stockhausen which is located between the areas of the eastern and western molasse methods include quantitative analysis of benthic foraminiferal assemblages qualitative studies of planktonic foraminifera and calcareous nannoplankton as well as palaeoenvironmental considerations based on the actualistic approach the results of these studies demonstrate that the lower and middle ottnangian upper marine molasse include a single transgressive regressive sedimentary cycle with gradual changes of foraminiferal assemblages in the eastern molasse on the other hand two sedimentation cycles are recognizable in the western molasse and in the borehole stockhausen where the lower and middle ottnangian sediments are separated from one another by an unconformity and display an abrupt change in lithofacies and foraminiferal content the benthic foraminiferal assemblages from the area of the western molasse are indicative of a rather shallow sea but indicative of a much deeper facies in the basin area of the eastern molasse it can therefore be concluded that the shallow sea to the west was more sensitive to minor changes in sea level than the area of the eastern molasse either because of global sea level variation or as a result of regional tectonics this means that the occurrence of two sedimentary cycles in the western molasse and absence of the second cycle in the eastern molasse may be the result of shallower water depths and a lower subsidence rate in the area of the western molasse another interesting result from our studies relates to the sea level highstand and maximum extension of the upper marine molasse sea that based on our studies has occurred during the early ottnangian rather than during the middle ottnangian as suggested previously during this highstand the area of the eastern molasse displays a differentiation into a deep neritic basin facies characterised by high organic flux and moderate oxygen depletion at times and a marginal marine facies with well oxygenated environments the latter facies remained poorly understood until recently the entire region of the south german molasse basin was affected by a regression during the middle ottnangian this phase is characterised by unstable environmental conditions in the eastern molasse i e salinity fluctuations and temporarily strong oxygen depletion of bottom waters in the western molasse life conditions became even worse and as a result a drastic decline in marine life is observable

precisely dated ams 14c marine cores reveal the complexity of millennial scale asian monsoon variability in the northern south china sea md972146 md972148 abstract high sedimentation rate sr cores retrieved from the south china sea scs form the basis for studying the marine components of millennial scale asian monsoon am variability and for comparison with the am reconstructions from cave records on land e g dongge and hulu however carefully correlating the scs sedimentary records to the cave records that are precisely dated by u th methods with resolution of decadal scale has not been completed such a correlation is essential when comparing am influences expressed over land and sea but requires a construction of marine ams 14c age models that are precise enough to be compared to the cave u th age models for the purpose of establishing such a correlation this study presents new data from intensive ams 14c dated marine cores retrieved from the northern scs md972146 md972148 the discrepancy of marine and cave 18o record for the interval of 18 30 ka might be due to the change of marine 14c reservoir age in scs surface water during the glacial period and to the change in interhemispheric dominance of the am systems with the new ams 14c dating on md972146 and md972148 we examined the millennial scale records of planktonic foraminifer 18o and carbonate contents of md972146 md97248 and sonne 17940 2 and compared those records with dongge hulu 18o record of the past 30 ka our results show that in the intervals corresponding to the high latitude northern hemisphere nh younger dryas yd and heinrich i event h1 the ams 14c dated millennial scale oscillations show relatively heavy 18o and low carbonate contents but h2 and h3 are in the opposite direction our results indicate the complexity for the marine cores which were used in interpreting the millennial scale am variability

late quaternary benthic foraminifera and deep water paleoceanography in the south china sea abstract recent and late quaternary deep sea benthic foraminifera in the south china sea scs have been quantitatively studied in order to approach some disputable questions about the glacial deep circulation of the pacific from the paleoceanographic records of a marginal sea for example whether or not there existed the north pacific deep water npdw during glacials based on the quantitative data of deep sea benthic foraminiferal faunas from sixty six surface sediment samples of the scs a q mode factor analysis indicates that the globocassidulina subglobosa assemblage the astrononion novozealandicum and bulimina aculeata assemblages and the eggerella bradyi assemblage are associated with the intermediate water mass iwm deep water mass dwm and the deep water below ccd in the scs respectively the factor assemblages resulted from surface sample data were then applied to the quantitative analysis of late quaternary deep sea benthic foraminifera in eight cores from the scs and western pacific the results show a generally increased contribution of the dwm assemblage relative to that of the iwm assemblage during glacials which implies that the influence of the dwm increased and that of the iwm decreased in the scs and western pacific however there were two major deep water paleoceanographic changes during the late quaternary 1 the deep sea carbonate dissolution of the scs and western pacific was intensified during 18 0 stages 4 5 evidenced by the higher arenaceous calcareous ratios of benthic foraminifera and relative abundance of eggerella bradyi 2 the influence of the pacific dwm above 2500 m greatly increased during the last glacial maximum lgm inferred from the increased abundances of the pacific dwm benthic foraminiferal assemblage as compared to those of the pacific iwm and pacific bottom water mass assemblages in the western pacific particularly the water in which favocassidulina favus was distributed could not enter the scs since the lgm meanwhile the great changes had taken place in the dwm of the scs during the lgm reflected in the occurrence of a clearly cooled and ventilated dwm and the replacement of a novozealandicum and b aculeata assemblages by b aculeata melonis barleeanum assemblage at water depths of 1000 2500 m these significant changes during the lgm may be related to the formation of the npdw

proxy dependence of the temporal pattern of deglacial warming in the tropical south china sea toward resolving seasonality abstract sea surface temperatures ssts reconstructed from two globigerinoides ruber white morphotypes g ruber sensu stricto s s g ruber sensu lato s l mg ca and alkenones uk 37 from core md01 2390 from the tropical south china sea scs during the last deglaciation reveal a proxy dependent discrepancy in the temporal pattern of the deglacial warming alkenone data suggest that the deglacial warming is punctuated by a decrease in temperature between 17 and 15 ka bp corroborating previously published alkenone uk 37 sst records from the southern scs within dating uncertainties this cooling is coeval with the heinrich event 1 h1 time interval in the north atlantic region underscoring the imprints of northern hemisphere forcing on tropical scs ocean temperatures the deglacial uk 37 sst minimum is also paralleled by a maximum in g ruber morphotype specific 18o g ruber mg ca sst estimates suggest a morphotype specific record of ssts during the time interval of h1 whereas g ruber s s imply a continuous warming starting around 18 ka bp without any marked response to h1 g ruber s l based mg ca sst estimates reveal a cooling around 17 15 ka bp similar to the h1 interval cooling seen in the alkenone sst record similar proxy dependent differences in deglacial surface water warming have been recorded in the eastern equatorial pacific implying a common pattern on both sides of the tropical pacific ocean we submit that this discrepancy could be due to differences in seasonality of planktonic foraminifera g ruber morphotypes and alkenone producing algae

foraminiferal responses to upwelling variations in the south china sea over the last 220 000 years abstract late quaternary benthic and planktonic foraminiferal and isotopic data were obtained from two sediment cores in the present upwelling areas of the south china sea core 17928 off northwestern luzon and core 17954 off eastern vietnam quantitative analyses of foraminifera in the two cores revealed the foraminiferal responses to paleoceanographic changes over the last 220 000 years high productivity species such as neogloboquadrina dutertrei bulimina acculeata uvigerina peregrina melonis barleeanus and chilostomella oviodea displayed high abundance during interglacial periods in core 17954 and during glacial periods in core 17928 correspondingly variations in benthic foraminifera accumulation rates the ratio of infaunal to epifaunal benthic foraminifera and the presence of the benthic foraminifers cibicidoides miloilids and oridorsalis umbonatus all indicate that bottom water was oxygen rich and oligotrophic during glacial periods off vietnam core 17954 but such bottom conditions occurred during interglacial periods off luzon core 17928 sea surface temperature results from planktonic foraminifera transfer function and variations in the abundance of planktonic foraminifera typical tropical species globigerina sacculifer tropical subtropical species globorotalia menardii globigerinoides ruber and pulleniatina obliquiloculata transition species globorotalia inflata and arctic species neogloboquadrina pachyderma indicate an increase in cool waters during marine isotope stage mis 5 except for mis 5 5 and glacial intervals in the cores 17954 and 17928 respectively the ratios of mixed layer thermocline dwelling species and depth of thermocline dot estimates using transfer function suggest that the dot was shallower during the interglacial than the glacial periods off vietnam core 17954 but the dot was shallower during the glacial periods off luzon core 17928 our results show that in the glacial periods lower sea surface temperature shoaled thermocline and high productivity increased off northwestern luzon core 17928 and that on the contrary similar event occurred in the interglacial off vietnam core 17954 these differences in the upper water column structure and productivity in the two areas were induced by coastal upwelling which in turn is driven by monsoons the intensity of upwellings is also closely related to the evolution of the eastern asian monsoon therefore we conclude that differences in the upwelling intensity in the two sites indicate strengthening of winter and summer monsoon during the glacial and interglacial periods respectively

response of planktonic foraminifera to glacial cycles mid pleistocene change in the southern south china sea a high resolution study 2 ka of planktonic foraminifers in 997 samples from odp site 1143 9821 72vn 113817 11ve water depth 2772 m in the southern south china sea scs reveals faunal response to glacial cycles in the last 2 1 ma most distinctive is the contrasting variations in the abundance of two tropical subtropical species that exhibit similar resistance to dissolution in modern oceans the relative and absolute abundances of globorotalia menardii are high in interglacials and low in glacials and covary with d 18 o fluctuations over the studied interval pulleniatina obliquiloculata however follow oxygen isotopes only before the mid pleistocene revolution mpr showing high abundances during glacials and low during interglacials after 850 ka three abundance maxima of p obliquiloculata are observed corresponding to three major glacial episodes marine isotope stages mis 2 12 and 16 respectively this change in abundance patterns of p obliquiloculata appears to be unique to the southern scs as in late pleistocene records from other western pacific regions including the okinawa trough and the northern scs all show co varying patterns with d 18 oa sg menardii does cross spectral analyses performed between percentages of globorotalia menardii and d 18 o records show high coherency at 41 ka obliquity and then at 100 ka eccentricity bands we suggest that the high abundances of g menardii during interglacials in the past 2 1 ma reflect warmer temperatures percentages of pulleniatina obliquiloculata vs oxygen isotope records show quite large phase difference at 41 ka obliquity band before the mpr as a contrast there are negligible phase differences in the vicinity of 100 and 41 ka after the mpr which means reverse trend between percentages of p obliquiloculata and d 18 o fluctuations the differences of p obliquiloculata from g menardii in abundance and orbital forcings are interpreted as resulting from a profound change in the regional upper ocean structure during the mpr time probably relating to a final glacial cut off of the southern scs from the indian water at 850 ka and to higher salinity during glacial times after 850 ka we speculate that this change is related to the decreased connection between the pacific and indian ocean d 2004 elsevier b v all rights reserved

tracing the nd isotope evolution of north pacific intermediate and deep waters through the last deglaciation from south china sea sediments abstract the intermediate and deep waters of the pacific ocean play a crucial role for regulating global climate changes on the millennium timescale however due to poor preservation of carbonate sediments in the deep pacific little attention has been received to better understand deep ocean circulation and its relationship with abrupt climate events here we present the first authigenic nd isotope e nd record extracted from fe mn oxyhydroxides of the south china sea scs sediments so17940 2 1727 m water depth in order to investigate changes of intermediate and deep water circulations in the pacific ocean since the last glacial maximum lgm in general the seawater e nd record extracted from the scs sediments paralleled the existing nd isotopes of fish teeth debris from the eastern north pacific core during the last deglaciation demonstrating that our authigenic e nd can faithfully record the seawater e nd evolution in the deep pacific ocean at the onset of the deglacial period our data exhibit a clear negative shift in e nd towards a gradually increased component of antarctica intermediate water aaiw and reached a maximal influx during the mid heinrich stadial 1 hs1 16 kyr bp between the hs1 and younger dryas deep water circulation gradually shifted back to the modern condition during the bolling allerod warm interval a pronounced negative e nd excursion had occurred during the pre boreal pb suggesting a rapid reorganization of deep water ventilation in the pacific ocean and was predominated by aaiw this is most likely due to poor ventilation in the western north pacific associated with an intensified summer monsoon during the pb early holocene warm period after the pb period the seawater e nd values were once again dominated by pacific deep water at the study site

evidence for warming of atlantic water in the southern canadian basin of the arctic ocean results from the larsen 93 expedition potential temperature and salinity s data obtained along the perimeter of the southern canadian basin north of the east siberian sea in 1993 aboard the ccgs henry larsen show higher temperatures in waters of atlantic origin than in available climatological data for the canadian basin in particular a front is observed near the mendeleyev ridge which separates the cooler atlantic waters of the canada basin from the warmer atlantic waters observed in the makarov basin the front is further characterized by a change in the s slope of arctic thermocline water and by thermohaline intrusions and s reversals within the atlantic layer the idea that this warm variety of atlantic water has come recently from the eurasian basin is supported by its higher level of the tracer cfc 11

unchanged nitrogen isotopic composition of organic matter in the south china sea during the last climatic cycle global implications the 15n of surface and down core sediments spanning the last 20 200 kyr from the entire south china sea scs ranges only from 3 0 to 6 5 with no correlation with discernible paleoclimatic oceanographic changes detailed profiles of the uppermost sediment column including fluff samples indicate a minor diagenetic overprint of 0 3 1 2 at the sediment water interface the absence of any correlation with reconstructed glacial interglacial changes in primary production terrigenous input and or sea level related basin configuration is attributed to a complete consumption of nitrate during primary production in this marginal basin during at least the last 140 000 years this in turn implies that the 15n of the nitrate used during primary production remained approximately constant during the last climatic cycle the proposed scenario infers an unchanged nitrogen isotopic composition of the western pacific subsurface nitrate between glacial and interglacial stages as well as during terminations and thus constrains proposed changes in the oceanic n inventory

glacial holocene biogenic sedimentation patterns in the south china sea productivity variations and surface water pco2 a bathymetric transect of cores in the south china sea extending from 4200 m to less than 1000 m water depth has been examined for glacial interglacial changes in carbonate and organic carbon sedimentation typical pacific carbonate cycles high carbonate content during glacials and low carbonate content during interglacials characterize cores from water depths deeper than 3500 m in contrast atlantic carbonate cycles low carbonate during glacials and high carbonate during interglacials are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level glacial interglacial changes in the carbonate chemistry of south china sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth ccd and the aragonite compensation depth acd during the last glacial the ccd and acd were at least 400 and 1200 m deeper respectively than at present organic carbon accumulation rates in the south china sea were approximately 2 times higher during the last glacial than the holocene carbon isotopic analyses and c n ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon on the basis of this we conclude that surface water productivity in the south china sea was approximately 2 times higher during the last glacial maximum this is consistent with previous studies which have demonstrated that glacial productivity was higher in low to mid latitude regions of the atlantic and eastern pacific the deglacial decrease in organic carbon accumulation is accompanied by a decrease in 13corg using the relationship between 13corg and co2 aq developed by popp et al 1989 we estimate that surface water pco2 values in the south china sea during the last 25 000 years were very similar to atmospheric co2 concentrations

radiolarian responses to paleoceanographic events of the southern south china sea during the pleistocene abstract a quantitative radiolarian study at core 17957 2 from the south china sea scs allows reconstructing two paleoceanographic events occurring during the last 1500 ka based on the abundance variations of siliceous microfossils radiolarian diatom and sponge spicule the definitions of the productivity and thermocline indexes dar diatom accumulation rate and tsr thermocline surface radiolarian indexes as indicators for productivity and thermocline changes as well as changes in the species composition two distinct changes at 900 ka and 600 ka could be detected being related to the multiple transition phenomena of the mid pleistocene revolution mpr the change in the species composition at 900 ka indicated by an increase in subtropical radiolarians and a decrease in tropical radiolarians exhibits a lowering of the sea surface temperatures in the scs that can be related to a southward shift of the north equatorial current induced by variations in the northern trade wind system increasing subsurface and intermediate species and dar and tsr indexes at 700 600 ka may reflect higher sea surface productivity and shallowing thermocline caused by stronger upwelling and nutrient supply the comparison of the radiolarian signal recovered from core 17957 2 with the magnetic susceptibility signal obtained from the chinese loess plateau reveals the close connection of the climatic transitions at 700 600 ka in the southern scs to strengthening of the east asian summer monsoon circulation the spectral analyses indicate that ice mass fluctuations oxygen isotope record have clear 100 ka eccentricity dominated and processional signals after the mpr but with a more significant obliquity related response before the mpr the surface productivity e g dar and thermocline depth e g tsr index show the 100 ka dominant cyclicity before the mpr the 32 ka significant regional cyclicity for the last 1500 ka responds to the surface productivity e g dar and thermocline depth e g tsr index signals

carbonate dissolution fluctuations in the western equatorial pacific during the late quaternary planktonic foraminiferal test fragmentation in three cores along a depth transect from the western equatorial pacific erdc 93p 1619 m rc17 177 2600 m v28 238 3120 m thompson 1976 were examined for the last 500 kyr at sample intervals from 2 5 to 5 kyr to study the fluctuations of dissolution in the western equatorial pacific the age models were constructed by correlating the 18o records with the specmap stack imbrie et al 1984 results showed that intermediate and deep waters experienced the same patterns of dissolution through climatic cycles fragmentation varied with a greater amplitude and the carbonate ion concentration changed less in the deep than in the intermediate water dissolution has significant variance distributions and coherencies with 18o over the 100 41 and 23 kyr periods of orbital variations dissolution maxima lag ice volume minima by 6 to 20 kyr the dissolution variability was consistent with recent geochemical models which seek to explain the reduction of atmospheric co2 concentration at the last glacial maximum broecker 1982 boyle 1988

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

millennial scale glacial variability versus holocene stability changes in planktic and benthic foraminifera faunas and ocean circulation in the north atlantic during the last 60 000 years two piston cores ds97 2p from the reykjanes ridge in the central north atlantic ocean 1685 m water depth and enam33 from southwest of the faeroe islands in the ne atlantic 1217 m water depth have been investigated for their planktic and benthic foraminiferal content ds97 2p is situated near the subarctic front and productivity measured by accumulation rates of benthic and planktic foraminifera has been generally high during the holocene the productivity shows a clear decrease from an early holocene maximum to a late holocene minimum coeval changes in the benthic faunas indicate that the food supply changed from large irregular pulses during the early holocene to a more sustained flux during the late holocene presumably in concert with decreasing bottom current activity oxygen conditions in the bottom water became poorer another feature of the late holocene is an increasing instability of the north atlantic thermohaline circulation regime nevertheless the changes in faunal composition and productivity during the holocene were gradual as compared to the discontinuous distribution patterns and abrupt productivity shifts during the glacial the glacial shifts were on a millennial time scale and correlate with the interstadial stadial phases of the dansgaard oeschger cycles in the greenland ice cores the faunas of the warm interstadial phases resembled the holocene faunas and both surface and bottom productivity was high the faunas suggest that the interstadial circulation pattern was very similar to the modern system with convection in the nordic seas and generation of north atlantic deep water the planktic faunas during the cold stadials and heinrich events were completely dominated by the polar species neogloboquadrina pachyderma s and surface conditions were cold and the productivity low the benthic faunas were dominated by species that presently thrive in areas with a low amount of food and reduced oxygen content the water column was probably stratified with low saline cold surface water overlying poorly aerated intermediate water masses

variations of the last glacial warm pool sea surface temperature contrasts between the open western pacific and south china sea 1 high resolution paleoceanographic records from the southern south china sea scs and the tropical open western pacific reveal multicentennial to millennial scale variations of the western pacific warm pool wpwp over the last 40 kyr during the last glacial maximum lgm in marine isotope stage mis 2 planktonic globigerinoides sacculifer do 18 in core ns93 5 from the southern scs and in core wp92 5 from the central wpwp registered a similar average value of about 1 5p however the average do 18 value was about 0 5p more negative in the scs than in the central wpwp as was their difference before and after the lgm in the later part of mis 3 and early portion of mis 1 these results indicate weaker monsoonal and fluvial effects on the southern scs during the last glacial than during pleniglacial and postglacial periods owing to different oceanic circulation modes and regional topography the calculated seasonal temperature differences of summer and winter sea surface temperatures ssts between the open wpwp and the southern scs were up to 3 4 5 d c during the lgm but only slightly over 3 d c in the southern scs and less than 2 d c in the open wpwp during other periods from about 29 to 25 ka the mis 2 3 transition was marked by a sudden sst increase in the southern scs but a decrease in the open wpwp over this 4 kyr period the average annual sst appeared to be only 28 d c in the central wpwp but more than 28 d c in the southern scs indicating a shift of the central wpwp toward the far west during that time furthermore our results imply a period of nearly 6 kyr from 22 5 to 16 5 ka without an apparent warm pool of 28 d c in the western pacific

oxygen minimum expansion in the sulu sea western equatorial pacific during the last glacial low stand of sea level the sulu sea in the western equatorial pacific is presently a shallowly silled dysaerobic deep marine basin deep waters in the sulu sea are ventilated through a single sill at 420 m depth which connects it to the china sea benthic and planktonic foraminiferal oxygen and carbon isotope records benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the sulu sea between the last glacial maximum 18 000 yrs b p and the present day an increase in the abundance of the planktonic foraminiferaneogloboquadrina dutertrei and relatively light planktonic foraminiferal 18o values suggest that during the last glacial maximum surface water salinities were reduced in the sulu sea enhanced isolation of the basin due to glacio eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid water oxygen minimum layer increased organic carbon preservation at mid water depths occurs at this time benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen minimum expansion at mid water depths during the last glacial maximum at water depths greater than 4000 m bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum stronger pacific ocean trade winds at this time may have caused the influx of denser celebes sea surface water into the southern part of the sulu sea the slow sinking of this water would have then ventilated bottom waters in this part of the basin at the transition from glacial to interglacial conditions rising sea level caused denser water to flow over the deepest sill into the sulu sea vertical circulation increased resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum continued post glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

the importance of the oxygen minimum zone and sediment geochemistry in the distribution of recent benthic foraminifera in the northwest indian ocean abstract the relationship between the distribution of benthic foraminifera and sediment type and depositional environment in the arabian sea is discussed the benthic foraminiferal fauna were sampled in nineteen recent surface sediment samples and geochemical variables of the sediment of the same samples were measured the water depths for the box core samples varies from 440 to 4040 m a total of 103 species and six species complexes were identified the geochemical properties were found to correspond well to the sediment type and depositional environment and six different sediment depositional environment types could be distinguished analysis of the benthic foraminiferal fauna reveals specific faunal assemblages that are closely related to these sediment depositional environment types

systematic biotic responses to palaeoenvironmental change in the late pleistocene southern south china sea a preliminary study oxygen and carbon isotopes from the planktonic foraminifer globigerinoides sacculifer trace element contents calcium carbonate biogenic silica grain size and abundances of diatoms radiolarians and foraminifera in a deep sea core from the southwestern south china sea were analysed to investigate the response of various marine ecological communities to environmental changes over the last 200 ka the synthesised results show that the quality of the palaeoecological environment for biological growth is primarily affected by nutrient supply and terrigenous disturbance ba and p are important nutrient elements for the growth of diatoms radiolarians and planktonic foraminifera together with dissolved silica and calcium carbonate in sea water these elements may control microbiotic development however variations in fe content appear to affect diatom and radiolarian abundance optimal biotic growth occurs when nutrients are abundant and when there is minimal terrigenous disturbance biotic growth decreases when sea water is highly oligotrophic and terrigenous input is high maximum biological growth occurred in the mid holocene but deteriorated soon afterwards owing to increased terrigenous input causing a decrease of biological abundance and productivity in the late holocene the results also indicate how the toba volcanic eruption ca 74 ka ago contributed to changing the ecological environment in the southern south china sea copyright c 2008 john wiley sons ltd

a pollen record of the last 37 ka in deep sea core 17940 from the northern slope of the south china sea this paper presents the palynological record of deep sea core 17940 from the south china sea 20 07 n 117 23 e water depth 1727 m this core is about 13 30 m long and covers the last 37 ka a total of 103 samples were counted at 10 cm intervals with a time resolution of ca 360 yr three pollen zones are recognized zone p1 14c age ca 37 0 15 0 ka b p 13 06 8 70 m is characterized by the expansion of montane conifers tsuga picea and abies and colonization by temperate grassland mainly artemisia on the exposed northern continental shelf as well as by frequent natural fires indicated by high values of charcoal concentrations this implies that the climate of this period was cool and dry frequent alternations of montane conifers and grassland dominated by artemisia indicate that oscillations of comparatively cool and humid conditions with temperate and dry conditions occurred according to the oxygen isotope data the period corresponds to stage 3 and the last glacial maximum climatic warming p2 a 8 70 7 23 m 15 0 11 3 ka b p associated with a rapid rise in sea level from ca 14 ka b p is inferred by expansion of tropical subtropical broad leaved forest with a replacement of grassland by mangroves mainly rhizophora and sonneratia this time interval may be assigned to the bolling allerod warming stage subsequently climatic cooling reflected by expansion of both montane conifers and upper montane rain forests mainly podocarpus and dacrydium during the period of ca 11 3 10 0 ka b p p2 b 7 23 6 6 m may be correlated with the younger dryas cold spell the similarity of pollen assemblages during the holocene and in the surface sediment from the northern south china sea implies that the vegetation and climate during the last 10 000 years was close to those of the present during the last 1400 years human activities are reflected in the sharp increase of dicranopteris fern spores

allochthonous ostracods in the south china sea and their significance in indicating downslope sediment contamination abstract the modern distribution pattern of allochthonous ostracods in the south china sea was analyzed and their palaeoceanographical significance in indicating downslope sediment contamination was testified using the sediment record of a core general characteristics of allochthonous ostracods in surface sediments of the south china sea include 1 a distribution limited to the shelf and slope off southern china and around coral reef studded shoal areas 2 a distinct depth range and assemblage composition of allochthonous forms between the areas on the continental slope and around coral reefs and 3 a downslope decline of assemblage abundance mean shell size and adult to juvenile ratio although this tendency is reversed at depths below 2000 m probably due to the increased carbonate dissolution and lowered productivity of indigenous ostracods in the deep sea the distribution patterns confirm the idea that post mortem transport of marine ostracods occurs in a downslope manner and at the same time suggests that allochthonous ostracods are suitable indicators of sedimentary source an analysis of ostracods from the core of sonne 95 cruise site 17940 taken from the northern slope of the south china sea reveals markedly higher accumulation rates and abundance of allochthonous forms in the transitional phases from cold to warm periods than in the quiet periods in between implying that downslope sediment transport from the shelf area was significantly intensified during transgression and regression

deep sea benthic foraminifera and biogenic opal glacial to postglacial productivity changes in the western equatorial pacific the accumulation rate of benthic foraminifera in deep sea sediments is strongly correlated with the productivity of the surface ocean core tops from diverse deep sea settings straddling different export production levels are used in this study for the calibration between the organic carbon flux to the seafloor jsf flux and the benthic foraminifera accumulation rate bfar the correlation can be used to reconstruct organic carbon flux to the seafloor in the past and hence the productivity of past oceans these results are compared with the accumulation rates of carbonate and biogenic opal in the sediments it is found that biogenic opal is more sensitive to productivity changes in the modern ocean than is carbonate the appropriate equations are derived for the equatorial pacific using core material fromeurydice erdc indomed inmd andpleiades plds expeditions these equations are then applied to two selected time horizons in sediments from the ontong java plateau a western equatorial pacific pelagic depth transect the last transition lt and the last glacial lg it is found that productivity was higher during the last glacial relative to the late holocene by a factor between 1 6 and 2 during the last transition productivity was intermediate between glacial and recent values we do not see any corresponding increase in the rates of accumulation of carbonate or biogenic opal during the last glacial this observation questions the importance of ocean productivity as the main controlling factor of carbonate and biogenic opal accumulation rates back through geological time

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

the controlling mechanism of mid to late holocene carbon isotopic variations of tridacnidae in the south china sea abstract the carbon isotopic fractionation process in biogenic carbonate is very complex and the mechanism for seasonal and long term variations in biogenic carbonate 13c remains a matter of debate in this study 5 tridacnidae samples were collected from the south china sea and analyzed in detail to study seasonal variations the high resolution 13c records exhibited cyclic variations likely related to seasonality in environmental parameters e g chl a concentration salinity sst rainfall 57 tridacnidae were collected and analyzed to study the millennium scale changes of tridacnidae 13c during the mid to late holocene and the controlling mechanism the tridacnidae 13c over the period 500 5500 bp is statistically significantly correlated with solar activity tsi and sunspot number likely attributed to the presence of symbiotic zooxanthellae within tridacnidae s mantle lobes solar activity could significantly affect the metabolic activity of zooxanthellae tridacnidae s microenvironment and thus tridacnidae s 13c composition the decoupling between the tridacnidae 13c and solar activity over the past 200 years is most likely due to increased amount of anthropogenic co2 and the oceanic 13c suess effect this study improves our understanding about the seasonal and long term variations of 13c in tridacnidae

pliocene pleistocene stable isotope and paleoceanographic changes in the northern south china sea abstract based on the stable isotopic analysis of planktonic and benthic foraminifers from ocean drilling program core 1148 of the northern south china sea scs pliocene pleistocene isotope stratigraphy and events have been reconstructed the benthic foraminiferal 18o record shows that the pacific intermediate water had a greater influence upon the scs or the pacific deep water above 2600 m was warmer before 3 2 ma than at present after that the benthic 18o conspicuously increased during the 3 2 2 5 ma period in correspondence to the formation of the northern hemisphere ice sheet whereas the planktonic 18o signal suggests a stepwise overall decrease of sea surface temperature during the 2 2 0 9 ma period compared to the equatorial pacific records the decrease in planktonic globigerinoides ruber 13c during the 3 2 2 2 ma period is particularly striking suggesting that fertility of surface water increased noticeably according to the modern 13c distribution of g ruber in the northern scs it is inferred that the east asian winter monsoon strengthened during this interval afterwards there were several conspicuous decreases of g ruber 13c at 1 7 1 3 0 9 0 45 and 0 15 ma bp that is about every 0 4 ma suggesting that the east asian winter monsoon became episodically stronger this is confirmed by changes in relative abundance of planktonic foraminifer species neogloboquadrina dutertrei a typical east asian winter monsoon proxy the deep water 13c of the scs is close to that of the pacific but lighter than that of the atlantic implying that the pattern of deep water originating mainly from the atlantic and through the pacific entering the scs existed at least since the early pliocene after 1 4 ma the benthic 13c signal decreased conspicuously but with a periodicity of 100 ka suggesting that the deep water ventilation of the scs was reduced probably corresponding to a decrease of the north atlantic deep water and or further isolation of the scs deep basin from the pacific during glaciations

palaeoproductivity linked to monsoon variability in the northern slope of the south china sea from the last 290 kyr evidence of benthic foraminifera from core sh7b

foraminiferal end in the deep north western subtropical pacific ocean tracing changes in weathering input over the last 30 000 years abstract this study focuses on the neodymium isotopic composition end of mixed planktonic foraminifera species in sediment cores collected on the north western margin of the south china sea scs and in the western equatorial pacific the aim was to identify temporal changes in the end of the upper circumpolar deep water ucdw during its northward penetration in the western subtropical pacific and to re evaluate the significance of deep water end changes at the northern margin of the scs over the past 25 kyr the past seawater end record derived from sediments of the subtropical western pacific displays a narrow range from 2 9 0 3 to 1 6 0 4 this suggests that the end of the ucdw is greatly modified during its northward penetration through the process of boundary exchange along the western volcanic margin of the south pacific and that the unradiogenic end signature of the ucdw observed in the south pacific about 6 has not been propagated beyond the equatorial pacific at least not over the last 25 kyr seawater end values obtained from the northern scs display large variations with values that are lower 6 8 0 3 to 5 6 0 2 for the last glacial period than for the late holocene 5 7 0 3 to 4 1 0 2 such glacial end cannot be attributed to a higher proportion of southern sourced water ssw as end values of the ucdw in the equatorial western pacific are more radiogenic than those observed in the scs the evolution of the seawater end values of the northern scs during the last glacial period and the last climatic transition is coeval with variations in the contribution of sediments from the pearl river the low sea level stand of the last glacial period resulted in a more proximal position of the pearl river mouth relative to core md05 2904 which a higher input of freshwater and in particular detrital sedimentary particles originating from the pearl river that partially dissolved during sinking led to a decrease in the seawater end along the north western margin of the scs enhanced rainfalls associated with intensified monsoon and more frequent typhoon activities during the early holocene climatic optimum from 9 to 7 cal kyr bp are linked to a decrease in sea surface salinity lower 18o values of planktonic foraminifera and a decrease in end values 6 2 0 3 induced by lithogenic nd input from pronounced freshwater and sediment discharge from distal rivers

ocean ventilation during the last 12 000 years hypothesis of counterpoint deep water production abstract available radiocarbon data on selected planktonic foraminifera species suggest that differential dissolution reduces the 14 c c ratio in planktonic tests removing 14c rich specimens from assemblages of surface dwelling species the effect is analogous to that observed for stable isotope composition in planktonic foraminifera other disturbing factors apparently affect benthic radiocarbon data as well thus radiocarbon stratigraphies are difficult to interpret in terms of history of deep water ages that is deep ocean mixing the best data at hand south china sea after corrections for differential dissolution and benthic vital deviations suggest a high variability of deep water mass ages in the late glacial period which is explained in terms of vertical motion of deep water mass boundaries across the recording sites the fluctuations are ascribed to sporadic increases in deep water production in the north pacific during cold periods and to the presence of a glacial bottom water mass which resisted mixing during deglaciation

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

circulation and oxygenation of the glacial south china sea abstract degree of oxygenation in intermediate water modulates the downward transferring efficiency of primary productivity pp from surface water to deep water for carbon sequestration consequently the storage of nutrients versus the delivery and sedimentary burial fluxes of organic matter and associated biomarkers to better decipher the pp history of the south china sea scs appreciation about the glacial interglacial variation of the luzon strait ls throughflow which determines the mean residence time and oxygenation of water mass in the scs interior is required based on a well established physical model we conducted a 3 d modeling exercise to quantify the effects of sea level drop and monsoon wind intensity on glacial circulation pattern thus to evaluate effects of productivity and circulation induced oxygenation on the burial of organic matter under modern climatology wind conditions a 135 m sea level drop results in a greater basin closeness and a 24 of reduction in the ls intermediate westward throughflow consequently an increase in the mean water residence time from 19 0 to 23 0 years however when the wind intensity was doubled during glacial low sea level conditon the throughflow restored largely to reach a similar residence time 18 4 years as today regardless its closeness comparing with present day scs surface circulation pattern in glacial model exhibits 1 stronger upwelling at the west off luzon island and 2 an intensified southwestward jet current along the western boundary of the scs basin superimposed hypothetically by stronger monsoon wind the glacial scs conditions facilitate greater primary productivity in the northern part manganese a redox sensitive indicator in images core md972142 at southeastern scs revealed a relatively reducing environment in glacial periods considering the similarity in the mean water residence time between modern and glacial cases the reducing environment of the glacial southeastern scs was thus ascribed to a productivity induced rather than ventilation induced consequence

no analog planktonic foraminiferal faunas in the glacial southern south china sea implications for the magnitude of glacial cooling in the western pacific warm pool sea surface temperature sst estimates in the sediment core md01 2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern south china sea scs during the last glacial maximum lgm relative to modern temperatures these results are in contrast to substantial cooling of 2 5 c inferred by geochemical uk 37 mg ca ratios and terrestrial proxies from the western tropical pacific region using multivariate statistics we show that the glacial southern scs harboured unique planktonic foraminiferal assemblages that have no modern analogs analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from mg ca data but that this signal is subdued by superimposed variations in the relative abundance of pulleniatina obliquiloculata and neogloboquadrina pachyderma dextral these species occur in glacial samples at proportions that are not observed in the calibration data set the glacial high abundance of n pachyderma dextral are interpreted to reflect a seasonal winter inflow of cold surface water from the northeast via the bashi strait due to the combined effects of an intensified winter monsoon a southward shift of the polar front and the eastward migration of the kuroshio current in contrast processes controlling the high relative abundances of p obliquiloculata during the lgm may be unique to the southern scs we propose a scenario involving a stronger winter mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow dwelling warm indicators to establish larger populations during the lgm our results indicate that a no analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical mg ca ratios alkenone unsaturation index marine proxies is a more likely scenario

millennial scale climate variability during the mid pleistocene transition period in the northern south china sea abstract stable isotopes of foraminiferal multispecies surface dwelling globigerinoides ruber thermocline dwelling pulleniatina obliquiloculata and benthic uvigerina peregrina and mg ca ratios of g ruber shells were analyzed with an average time resolution of 370 yr for reconstructing the orbital and millennial scale changes in the east asian monsoon and associated upper water structure during the mid pleistocene period of 800 1060 ka at odp site 1144 in the northern south china sea scs it has been found that generally the sea surface temperature sst were lower and the depth of thermocline dot was deeper during glacial stages and vice versa during interglacial stages indicating a strengthened winter monsoon and weakened summer monsoon during glacial stages the sea surface salinity sss was relatively lower during glacials induced by the greatly reduced distance of this site to the shore during times of low sea level further spectral analyses have revealed significant semi precessional and or precessional cycles in the planktic 18 o sst and the proxies of sss and dot showing the typical characteristics of tropical climate change this means that during the mid pleistocene climate transition mpt period the east asian monsoon evolution and associated changes of upper water column structure in the northern scs were probably driven partly by tropical forcing like in the southern scs and should not be related only to the high latitude ice sheet changes particularly millennial scale climate fluctuations mainly 1 4 kyr cycle were found to exist throughout the glacial and interglacial stages during the mpt period in the northern scs but slightly different from the sawtooth like d o events recorded in late quaternary greenland ice cores during the mid pleistocene terminations the sst warming was synchronous with the northern ice sheet retreat indicated by benthic 18 o in the northern scs which is consistent to the previous findings in the late quaternary scs and apparently different from that in the western equatorial pacific ocean providing new insights into the studies of east asian monsoon evolution and rapid climate change

new evidence from the south china sea for an abrupt termination of the last glacial period abrupt changes in climatic conditions have been seen at high latitudes in the north atlantic1 and the antarctic2 3 at 13 kyr bp it is important to determine whether this abrupt change was confined to high latitude regions or whether it was global here we present results demonstrating an abrupt change in the rate and character of sedimentation in the south china sea at the close of the last glacial period radiocarbon dating and its position in the oxygen isotope shift suggest that this change may be coincident with the changes found at high latitudes

neogene and quaternary paleoceanographic changes in the southern south china sea site 1143 the benthic foraminiferal record deep sea benthic foraminiferal assemblages from ocean drilling program odp site 1143 located in the southern south china sea scs were investigated to evaluate the relationship between faunal composition patterns and paleoceatiographic changes during the last 6 million years late miocene to holocene we used multivariate statistics correspondence analysis to analyze carbon flux related changes in assemblage composition of benthic foraminifers additional proxies for carbon flux and deep water ventilation include delta 13 c records of epifaunal cibicidoides wuellerstoifi and infaunal uvgefina peregrina var dirupta and melonis pompilioides benthic foraminiferal accumulation rates bfarss diversity indices and relative abundances of indicator species we observe three significant benthic faunal changes in the southern south china sea during the last 6 million years strong fluctuations in bfar and relative abundance of productivity indicator species between glacial and inter glacial stages after the mid pleistocene revolution mpr at approximately 0 9 ma indicating stronger seasonal carbon flux fluctuations are accompanied by the extinction of such species as stilostomella spp increases in carbon flux indicator species are coupled with an overall deer ease in benthic foraminifer diversity around 3 0 ma in the late pliocene this may indicate increasing carbon flux in a period of productivity maximum caused by enhanced offshore upwelling from intensified winter monsoon wind strength c 2004 elsevier b v all rights reserved

bioturbational structures record environmental changes in the upwelling area off vietnam south china sea for the last 150 000 years the sediments in the upwelling area off central vietnam are totally bioturbated and display a low diverse assemblage of bioturbational structures during interglacial times marine isotope stage mis 1 5a 5c 5e summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic matter on the seafloor these deposits are characterized by a 4 tier bioturbated zone with zoophycos zoophycos producers used this seasonal food source and show a cache behavioral strategy during glacial periods upwelling was weak and oxygenation of bottom water decreased as evidenced by bioturbational structures that show a decrease in size penetration depth and diversity enlarged freshwater influx during glacial times fuelled primary production and led to estuarine circulation the resultant oxygen minimum layer favored an increased deposition of organic matter that in turn affected sediment properties during mis 2 and 5b oxygenation was probably a little lower than today during mis 3 and 5d chondrites like burrows point to a stronger oxygen deficiency during mis 4 bottom water oxygenation was even lower and only biodeformational structures occur in soft sediment rich in benthic food based on these findings an ichnofabric model for food rich fairly soft deposits experiencing oxygen deficiency is suggested having biodeformational structures as low oxygen end member

globorotalia truncatulinoides as indicator of upper ocean thermal structure during the quaternary evidence from the south china sea and okinawa trough abstract globorotalia truncatulinoides is shown to be indicative of upper ocean thermal structure and sensitive to the thermocline fluctuations and the thickness of the north pacific subtropical mode water npstmw thermostads for the quaternary in the south china sea scs and okinawa trough during the last 1 5 ma the relative abundance percentage of g truncatulinoides displayed long term oscillations on a time scale longer than the glacial interglacial cycle but with two major changes around 550 400 ka and 115 55 ka bp it decreased to near zero during 550 400 ka bp and then disappeared from the equatorial indian and pacific oceans this suggests that the thermocline depth and the scale of winter deep mixing decreased at that time interval and since then the linkage between the scs and the equatorial oceans at intermediate depths remarkably weakened and the npstmw strongly influenced the scs the predominance of left coiling g truncatulinoides together with the occurrence of globoquadrina conglomerata in the western north pacific between 115 and 55 ka bp indicates a deep thermocline and very thick npstmw thermostads a decreasing trend in the relative abundance of g truncatulinoides from marine isotopic stages 7 to 1 is evident in the scs indicating a progressive reduction of the npstmw thermostads after the last glacial maximum g truncatulinoides increased in abundance but abruptly disappeared between 8 and 4 ka bp from the scs and okinawa trough implying a mid holocene reduction in the npstmw thermostad thickness

glacial to interglacial contrasts in the northern indian ocean differences between the 18o 16o ratios of planktonic foraminifera deposited during the last glacial maximum about 18 000 yr ago and those deposited during the holocene show that in the indian ocean the south west monsoon was weaker than today but that the north east monsoon was stronger the upwelling observed in modern conditions along the southern coast of arabia had disappeared because of the low speed of the southwestern winds during glacial summers the reduction in rainfall and runoff over the continent caused a reduction of the salinity gradient in the bay of bengal and along the western coast of india increased precipitation fell on the sea south of 10 n while strong evaporation over the northernmost arabian sea produced an enhanced salinity gradient in that area

late quaternary upwelling intensity and east asian monsoon forcing in the south china sea foraminifera from two cores off eastern vietnam and the northwestern philippines where modern summer and winter monsoon driven upwelling occurs in the south china sea respectively were analyzed to evaluate the changes in paleoproductivity and upper water structure over the last 220 000 yr we observed enhanced organic carbon flux and a shoaled thermocline when upwelling intensified off eastern vietnam during interglacial ages and off the northwestern philippines during glacial ages this indicates that the east asian summer monsoon increased while the winter monsoon decreased during interglacial ages particularly the upwelling reached a maximum off eastern vietnam during late marine isotopic stage mis 5 and off the northwestern philippines during mis 2 implying that the summer monsoon decreased gradually since mis 5 while the winter monsoon displayed an opposite trend the variations in upwelling proxies exhibit a distinct cyclicity with frequencies near 41 000 yr and 23 000 yr off eastern vietnam in contrast to a strong frequency peak near 100 000 yr off the northwestern philippines we suggest that the east asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity while ice volume forcing is probably a primary factor in determining the strength and timing of the east asian winter monsoon but with less important insolation forcing

sensitive grain size records of holocene east asian summer monsoon in sediments of northern south china sea slope changes in paleoenvironments over the last 17 500 yr have been documented by a high resolution clay mineralogy and grain size records of core kng5 from the northern slope of the south china sea our results indicate that clay minerals are mainly from the pearl river from 17 500 to 12 500 cal yr bp and the south china sea modern current system began to form since 12 500 cal yr bp as a result taiwan turns to be the major contributor of clay minerals after 12 500 cal yr bp two grain size populations with high variability through time were identified in the 13 28 mu m and 1 2 2 mu m grain size intervals the 1 2 2 mu m grain size population are mainly controlled by provenance supply and current transport the 13 28 mu m grain size fraction could be controlled mainly by the sea level change the 1 2 2 mu m grain size population record demonstrates that east asian summer monsoon intensity generally follows changes in insolation and that the response is similar for a large area of china and other northern low latitude records implying the globality of the monsoon evolution since holocene the anomalous environmental conditions in the northern south china sea may imply intensified enso activity during the late holocene c 2011 university of washington published by elsevier inc all rights reserved

diatom response to changes in palaeoenvironments of the northern south china sea during the last 15 000 years changes in palaeoenvironments over the last 15000 years have been documented by a high resolution diatom record of core 17940 from the northern slope of the south china sea four diatom assemblage zones each characterized by different diatom components are distinguished by cluster analysis t nitzschioides var parval t nitzschioides t nitzschioides var parva tnp tnp tn and the brackish littoral species used as the proxies for temperature and salinity are compared with previously published sea surface temperature fp 12e sstw and sea surface salinity sss data from the same core and with the dongge cave delta 18 o record the bolling allerod warm phase the younger dryas cold event the holocene climate optimum and three holocene cooling events 7150 6250 4150 3450 and 1800 1350 cal yr bp are clearly distinguished by changes in the abundance of the brackish littoral species and or in tnp tnp tn data a marked increase in the abundance of the coastal species paralia sulcata during the interval 11150 8050 cal yr bp indicates a strong coastal water influence probably due to both enhanced freshwater discharge from the pearl river and the opening of the taiwan strait this palaeoceanographic change might be caused partly by climate induced sea level lowering during the late pleistocene and the early holocene the palaeoceanography during most of the holocene appears to be primarily controlled by fluctuations in the east asian summer monsoon intensity c 2009 elsevier b v all rights reserved

hemipelagic sediment accumulation rates in the south china sea related to late quaternary sea level changes sediments of 13 piston cores from opposite continental slopes of the south china sea off southern china and sabah northern borneo were analyzed by sedimentological methods and dated by oxygen isotope stratigraphy sediments mostly consist of hemipelagic clay with 20 carbonate off sabah and 40 off china we calculated terrigenous and carbonate accumulation rates for up to 11 time slices from the holocene to oxygen isotope stage 6 terrigenous accumulation rates generally increase with water depth and reach a maximum at the middle slope off sabah and at the lower continental slope off china during glacial and interglacial times this distribution pattern did not markedly change despite an increase of accumulation rates for glacial periods by a factor of 2 to 5 compared to interglacial periods rates are negatively correlated with positions of sea level which controls the partition of fluviatile terrigenous material for deposition on shelf slope and abyssal plain carbonate accumulation rates are higher off china by a factor of 2 compared to sabah probably indicating higher calcareous plankton productivity

northeastern atlantic benthic foraminifera during the last 45 000 years changes in productivity seen from the bottom up we studied benthic foraminifera from the last 45 kyr in the 63 mu m size fraction in biogeochemical ocean flux studies bofs cores 5k 50 degrees 41 3 n 21 degrees 51 9 w depth 3547 m and 14k 58 degrees 37 2 n 19 degrees 26 2 w depth 1756 m at a time resolution of several hundreds to a thousand years the deepest site showed the largest fluctuations in faunal composition species richness and benthic foraminiferal accumulation rates the fluctuations resulted from changes in abundance of epistominella exigua and alabaminella weddellensis in the present oceans these species bloom opportunistically when a spring plankton bloom results in seasonal deposition of phytodetritus on the seafloor the phytodetritus species had very low relative abundances and accumulation rates during the last glacial maximum a strong increase in absolute and relative abundance of e exigua and a weddellensis during deglaciation paralleled the decrease in abundance of the polar planktonic foraminifer neogloboquadrina pachyderma s and the increase in abundance of warmer water planktonic species such as globigerina bulloides this strong increase in relative abundance of the phytodetritus species and the coeval increase in benthic foraminiferal accumulation rate were thus probably caused by an increase in the deposition of phytodetritus to the seafloor and thus probably of surface productivity when the polar front retreated to higher latitudes the abundance of phytodetritus species decreased during the younger dryas but not to the low levels of fully glacial conditions during heinrich events periods of excessive melt water formation and ice rafting benthic accumulation rates were very low as were the absolute and relative abundances of the phytodetritus species supporting suggestions that surface productivity was very low during these events in both cores pullenia and cassidulina species were common during isotope stages 2 3 and 4 as were bolivinid buliminid and uvigerinid species high relative abundances of these species have been interpreted as indicative either of sluggish deep water circulation or of high organic carbon fluxes to the seafloor in our cores relative abundances of these species are negatively correlated with benthic foraminiferal accumulation rates and we can thus not interpret them as indicative of increased productivity during glacials the percentage of these low oxygen species calculated on a phytodetritus species free basis decreased slightly at deglaciation at 5k but not at 14k this suggests that decreased production of north atlantic deep water during the last glacial might have slightly affected benthic foraminiferal faunas in the eastern north atlantic at 3547 m depth but not at 1756 m in conclusion major changes in deep sea benthic foraminiferal faunas over the last 45 000 years in our cores from the northeastern atlantic were the result of changes in surface water productivity not of changes in deep water circulation productivity was lower during the glacial probably because of extensive ice cover

quantitative composition of benthic foraminiferal assemblages as a proxy indicator for organic carbon flux rates in the south china sea abstract the organic carbon flux signal embedded in the distribution data of benthic foraminifera from 43 box core surface samples from the south china sea scs is compared to data from two gravity cores on the northern core 17940 2 and southern core 17964 3 slope of the scs surface sampling stations cover almost the entire area of the south china sea including areas with preferential summer monsoonal upwelling or winter monsoonal upwelling as well as a wide range of water depths 300 4000 m we use correspondence analysis afc to examine the relation between the quantitative composition of benthic foraminiferal assemblages water depth and organic carbon flux rates we find a clear correlation between benthic foraminiferal assemblage composition factor 1 of the afc and organic carbon flux rates in the surface samples and use the same model to calculate paleo flux rates for the two cores significantly increased carbon flux rates are observed in the southern scs sunda shelf margin during the last glacial maximum lgm whereas the organic carbon flux rates along the northern slope of the scs seem to be highest during the early holocene

radiocarbon age of last glacial pacific deep water one of the most important projects envisaged ever since the possibility emerged of making tandem accelerator mass spectrometric radiocarbon determinations has been that of investigating changes in the radiocarbon age of the deep ocean1 initial attempts to achieve this2 were thwarted by difficulties imposed by bioturbation because these workers used core v28 238 with an accumulation rate of only 1 5 cm kyr 1 thus emphasizing the need to work in a core with a higher accumulation rate working in the glacial section of core tr163 31b with an accumulation of 10 cm kyr 1 we show here that the ventilation age of pacific deep water was about 500 years greater in last glacial times than it is today

benthic foraminiferal paleoceanography of the south china sea over the last 40 000 years benthic foraminifera in gravity and piston cores from two sites of the northern and southern slopes of the south china sea scs were analyzed to evaluate changes in surface productivity and deep water mass characteristics over the last 40 000 years our observations suggest that changes in organic carbon flux that is food supply and chemical and or physical properties of the ambient water mass may be the two primary and intercorrelated factors controlling the distribution patterns of benthic foraminifera when organic carbon flux increased above 3 5 g c m 2 yr 1 in the southern scs during the last glacial maximum and in the northern scs during the first part of the holocene around 10 ka b p a group of detritus feeders including bulimina aculeata and uvigerina peregrina dominated the benthic foraminiferal assemblage as shown by relative abundance and accumulation rates this may reflect episodes of increased surface productivity possibly induced by increased input of nutrients from nearby river runoff suspension feeders such as cibicidoides wuellerstorfiand a group of opportunistic species including oridorsalis umbonatus melonis barleeanum and chilostomella ovoidea gradually became more abundant than detritus feeders as soon as the organic carbon flux decreased to 2 5 3 5 g c m 2 yr 1 similar glacial to interglacial changes in relative abundance and accumulation rates were observed in both cores for a number of species including eggerella bradyi globocassidulina subglobosa astrononion novozealandicum sphaeroidina bulloidesand cibicidoides robertsonianus these changes were not correlated to the distribution patterns of organic carbon in both cores and may have been related to yet unspecified changes in chemical and or physical properties of the ambient water mass independent of changes in organic carbon flux 1999 elsevier science b v all rights reserved

high resolution elemental records from the south china sea and their paleoproductivity implications 1 the biogenic related elements ca sr ba p cd scavenged al and ti were analyzed by inductively coupled plasma mass spectrometry icp ms and inductively coupled plasma atomic emission spectrometry icp aes for core ns93 5 from the west slope of the south china sea terrestrial input as estimated from the accumulation of ti was higher during glacials than during interglacials carbonate accumulation rates are inversely related to those of terrestrial input suggesting higher production of calcareous phytoplankton during interglacials the accumulation patterns of authigenic sr ba p and cd match that of carbonate further indicating higher calcareous phytoplankton production during interglacials scavenged al and excess sio2 which is related to biogenic opal exhibit higher accumulation rates during glacials and correspond with changes in terrestrial input this indicates that terrestrial input driven is important to siliceous phytoplankton production but not for calcareous phytoplankton production as calcareous phytoplankton is the dominant component of the biogenic sediments in the south china sea particularly during interglacials previous inference of higher productivity in the south china sea during glacials based on only the biogenic opal proxy needs to be reconsidered

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

foraminiferal responses to major pleistocene paleoceanographic changes in the southern south china sea a detailed age model for core 17957 2 of the southern south china sea was developed based on delta 18 o coarse fraction magnetostratigraphy and biostratigraphy for the last 1500 kyr the delta 18 o record has clear similar to 100 kyr cycles after the mid pleistocene revolution mpr at the entrance of marine isotopic stage mis 22 planktonic foraminifera responded to the mpr immediately showing the increased sea surface temperature sst and dissolution after the mpr benthic foraminifera did not respond to it until the brunhes matuyama boundary since the mpr the depth of thermocline gradually became shallower until miss 6 5 this major change within miss 6 5 was also reflected in the decreased ssts and increased productivity and deep water mass thus two major pleistocene paleoceanographic changes were found one was around the mpr the other occurred within miss 6 5 which speculatively might be ascribed to the reorganization of surface and deep circulation possibly induced by tectonic forces

atmospheric summer circulation and coastal upwelling in the arabian sea during the holocene and the last glaciation accumulation rates of biogenic and lithogenic components were studied in 39 turbidite free well dated sediment cores from the northern indian ocean to define the proportions of fluvial and eolian input and to reconstruct quaternary patterns of coastal upwelling the majority of dust deposited in the western arabian sea during the holocene about 100 106 t yr 1 is advected from arabia by northwesterly winds which overlie the low level southwest monsoon the glacial increase in dust flux to 160 106 t yr 1 culminated in the northern arabian sea most probably due to i entrainment of dust rich in chlorite dolomite and lithogenic carbonate in the then dry persian gulf and ii a southward shift of the mean position of the southwest monsoon during glacial summer this shift is recorded in reduced accumulation rates of biogenic opal and increased rates of marine carbonate off somalia and oman both the terrigenous and biogenic sediment records show that the northwesterly winds and the southwest monsoon persisted over the last 27 000 yr as well as the asian continental summer heat low however the glacial seasonal time span of the southwest monsoon season was much reduced most likely because of a delay in the seasonal onset of the southwest monsoon

early interglacial carbonate dilution events in the south china sea implications for strengthened typhoon activities over subtropical east asia abstract a compilation of many late quaternary marine sediment records from the northern south china sea scs continental slope confirms 15 50 reductions in sedimentary calcium carbonate concentrations between 11 0 and 8 5 ka bp in the early holocene this low carbonate event occurred at a time when the regional sea level rose from 50 m to 10 m which drowned large areas of continental shelves especially those near and within the taiwan strait this event is associated with a significant increase in bulk sedimentation rates on the upper continental slope and the relative abundance of fine grained detritus sediment provenance analyses suggest a dominant terrigenous input from taiwan and a minor contribution from luzon during the low carbonate event similar to the background terrigenous deposition in other periods of the holocene two comparable low carbonate events respectively from the beginning of marine isotope stages 5 5 and 7 3 have also been recognized pointing to similar causal factors while carbonate dissolution and carbonate accumulation rate should not have been responsible increased terrigenous input and dilution is considered as the main cause for the recurrent low carbonate events in early interglacials we further hypothesize that during early interglacials fluvial sediment discharge from taiwan and luzon intensified due to stronger typhoon activities and massive fine grained sediments from these two end members may have been transported to the northern scs continental slope via surface and deep ocean currents the conjecture of strengthened typhoon activities over east asia during the early holocene is supported by high ocean heat contents in the west pacific warm pool area with the prevailing la nina like conditions

late quaternary paleoceanography of the south china sea glacial interglacial contrasts in an enclosed basin the sea surface paleotemperature of the south china sea scs is estimated quantitatively based on the quantitative analysis of planktonic foraminiferal faunas recovered from piston cores v36 06 3 v36 06 5 and so49 kl8 on the northern continental slope the results lead to a reconstruction of the history of paleocirculation patterns during the last 200 000 years the postglacial and interglacial transbasinal circulation pattern was replaced by a semienclosed basin flow pattern during glacial episodes lowered sea level transformed the scs into a semienclosed basin with the only passageway to the open ocean in its northeastern corner the east asian monsoon which governs circulation patterns in the scs both today and during the late quaternary created both clockwise summer and counterclockwise winter surface gyres during glacials the inflow of tropical surface water masses from both the pacific and indian oceans decreased or was completely cut off from this marginal sea causing a greater decrease in glacial sea surface temperature than in the open ocean of the same latitude inferred increased influence of pacific temperate waters and decreased influence of tropical subtropical waters are confirmed by changes in the planktonic foraminiferal assemblages glacial interglacial fluctuation in sea surface temperature sst 6 8 9 3 c for winter and 2 3 c for summer as well as the seasonality 4 6 c for postglacial and interglacials and 9 10 c for glacials are much greater than the adjacent open western pacific reflecting the amplification of the climatic signal in the marginal sea

impact of productivity events on the benthic foraminiferal fauna in the arabian sea over the last 150 000 years we have studied the sediment geochemistry and benthic foraminiferal fauna in a piston core from the northwest arabian sea covering the last 150 000 years and compared the results with the stable isotopic record from both benthic uvigerina peregrina and planktonic globigerinoides sacculifer foraminifera the 18o record of the planktonic foraminiferal species shows excursions towards heavier 18o values when compared to the benthic record and the specmap stack particularly in stage 3 between approximately 30 and 45 50 kyr we call this the stage 3 event species diversity and relative abundance data on benthic foraminifera reveal that some species e g cibicidoides wuellerstorfi oridorsalis umbonatus pullenia bulloides pyrgo spp and the uvigerinids increased in relative abundance during glacial stages 2 and 4 and during the stage 3 event whereas other e g astrononion novozealandicum cibicidoides bradyi eggerella bradyi gyroidina altiformis hoeglundina elegans pullenia subcarinata and sigmoilina edwardsii decreased using correspondence analysis we determined that approximately 50 of the total sample variation may be accounted for by three first factors which all are interpreted as primarily related to surface water productivity and the quality of the organic matter that reaches the seafloor the relative abundance of some species appears to vary on a precessional cycle perhaps responding to monsoon driven upwelling and associated increased food supply whilst the abundances of other species are related to the 100 kyr ice volume cycle and may be responding to changes in intermediate and deep water chemistry geochemical paleoproductivity tracers such as the ba content of the sediment have a very similar distribution to specific foraminiferal factors in both time and frequency domains certain planktonic foraminifera e g globigerina bulloides also display obvious maxima in the stage 3 event the stage 3 event occurs at a time of reduced rate of amplitude change in both solar radiation and monsoon pressure index we conclude that there was a period 15 to 20 kyr duration during stage 3 with cooler than normal surface waters enhanced productivity and rapid settling of biogenic matter

deep water exchanges between the south china sea and the pacific since the last glacial period deep ocean circulation is widely considered as one of the important factors for increasing co2 concentration and decreasing radiocarbon activity 14c of the atmosphere during the last deglaciation the ams 14c ages of benthic and planktonic foraminifers from 18 samples of core md05 2904 water depth of 2066 m in the northern south china sea scs and 15 samples of core md05 2896 water depth of 1657 m in the southern scs were analyzed in this study for reconstructing the intrabasin deep oceanic processes and hence exploring the deep water exchanges between the scs and the pacific since the last glacial period the results show that during the holocene the average apparent ventilation age of deep water was younger in the southern scs 1350 years than in the northern scs 1850 years due to relatively strong vertical mixing and advection consistent with modern observations however during the last glacial period and deglaciation the deep water was older in the southern scs 2050 years and 1800 to 1200 years respectively than in the northern scs 1600 years and 670 years respectively indicating reduced deep mixing and advection moreover the northern scs deep water was significantly younger during the last deglaciation than during the holocene and the last glacial period implying the existence of northern sourced newly formed and relatively young north pacific deep water our records do not support the intrusion of anomalously 14c depleted deep water to the middepth of the low latitude western pacific and the scs during the mystery interval 17 5 14 5 kyr b p

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

spatial distribution and controlling factors of planktonic foraminifera in the modern western pacific abstract studies of the spatial distribution of living planktonic foraminifera in modern water columns are still lacking in the western pacific in this study 40 plankton tows at 8 stations were conducted focusing on the terminus of the north equatorial current nec and its two bifurcated branches in the western pacific the results show that planktonic foraminifera were in high abundance around the kuroshio current kc source region and the mindanao current mc system but in low abundance in the nec the planktonic foraminiferal assemblage was dominated by g sacculifer and g ruber with relative abundances of 44 0 and 27 3 respectively according to a cluster analysis of the results of seven stations the stations can be divided into three groups namely group nec group kc and group mc which displayed different features of planktonic foraminiferal assemblages the low abundance of planktonic foraminifera that characterized the nec stations may be induced by the thick mixed layer and deep thermocline nutricline in this region however stations in the kc region which also had thick mixed layers and deep thermoclines showed higher abundances of planktonic foraminifera than the nec stations this result was probably caused by the higher terrigenous input the planktonic foraminifera show the highest abundance at the mc stations which may be the result of existing upwelling conditions

high resolution benthic foraminifer δ13c records in the south china sea during the last 150 ka abstract high resolution 13c ratios of benthic foraminifer cibicidoides wuellerstorfi in core md97 2151 from the southern south china sea scs and core so50 31kl from the northern scs indicate deep water variations in the scs during the last 150 ka the 13c records of both show a general variation pattern with higher 13c during interglacial periods than glacial periods and rapid increases during terminations this variation pattern resembles those of the west pacific intermediate deep water the sources of the scs deep water and the general variation of global deep water indicating that the variation of the scs deep water is largely controlled by global factors such as carbon cycles and global deep water circulation spectra analysis exhibits robust milankovitch cycles in the scs deep water 13c again supporting global controls significant semi precession cycles can also be seen in the spectra implying that changes of local surface productivity also influence the scs deep water 13c

palaeoproductivity evolution in the centre of the western pacific warm pool during the last 250 ka to reconstruct the palaeoproductivity evolution history of the centre of the western pacific warm pool wpwp over the last 250 ka multi proxies were analysed in sediment core wp7 recovered from the ontong java plateau palaeoproductivity evolution at the centre of the wpwp during the last 250 ka is closely related to glacial interglacial cycles and the insolation controlled by precession the glacial higher primary productivity relative to the interglacial conditions could have resulted from both thermocline shoaling associated with persistent el nino like conditions and the increased influx of dust resulting from intensified winter monsoon together with important changes in the thermocline the minimum primary productivity values during the last three terminations could be resulted from deglacial thermocline deepening and intensified stratification associated with persistent la nina like conditions and the concurrent neogloboquadrina dutertrei delta c 13 minimum events probably reflect the chemical signatures of subantarctic mode water and antarctic intermediate water in addition primary productivity values are also controlled by the thermocline variations resulting from el nino la nina southern oscillation processes responding to precession forcing and lead the delta o 18 by about 4 ka the 33 1 ka 19 ka and half precession periods are prominent in the palaeoproductivity records copyright c 2011 john wiley sons ltd

evidence for a bathyal front at 2000 m depth in the glacial pacific based on a depth transect on ontong java plateau data on oxygen and carbon isotope compositions of the benthic foraminifer planulina wullerstorfi from 18 cores 17 box cores and one piston core from ontong java plateau provide proxy depth profiles for temperature water mass and nutrient content for the late holocene the last transition and the last glacial the 18o profile during glacial time shows an increased gradient at a depth near 2000 m the corresponding 13c data suggest that a bathyal nutricline existed close to the same depth level the 13c values provide limits on the global change in carbon content of the glacial ocean which may be estimated as distinctly less than 1 atmospheric carbon mass 1 acm 700 gtc the greater co2 content of glacial deep waters which is reflected in the more negative 13c values may be at least in part due to a more sluggish renewal of abyssal deep waters if so the water of the deep pacific was up to 400 years older than now in turn ventilation in the upper waters above 2000 m may have been more vigorous than today

can co2 hydrate assist in the underground storage of carbon dioxide the sequestration of co2 in the deep geosphere is one potential method for reducing anthropogenic emissions to the atmosphere without necessarily incurring a significant change in our energy producing technologies containment of co2 as a liquid and an associated hydrate phase under cool conditions offers an alternative underground storage approach compared with conventional supercritical co2 storage at higher temperatures we briefly describe conventional approaches to underground storage review possible approaches for using co2 hydrate in co2 storage generally and comment on the important role co2 hydrate could play in underground storage cool underground storage appears to offer certain advantages in terms of physical chemical and mineralogical processes which may usefully enhance trapping of the stored co2 this approach also appears to be potentially applicable to large areas of sub seabed sediments offshore western europe

dynamics of primary productivity in the northern south china sea over the past 24 000 years in this study paleoproductivity on millennial scales was precisely reconstructed from core md12 3428cq in the northern south china sea scs over the past 24 kyr based on a transfer function derived from the strong exponential negative correlation between relative abundance of florisphaera profunda fp in core top sediments and basin wide satellite based primary productivity pp in the scs to detect the potential driving mechanisms of pp correlation analyses were carried out among our pp records and other paleoenvironment parameters pp peaked during 18 15 ka in parallel with the strong east asian winter monsoon eawm from 15 ka to the early holocene a decrease in pp coincided with sea level progradation and weakening of eawm which ultimately reduced fluvial nutrient levels and wind driven upper water column mixing since the middle holocene gradually more frequent el nino southern oscillation enso events have taken place further decreasing pp by injecting oligotrophic kuroshio water masses into the northern scs associated findings conclusively indicated that the main controlling factors of pp in the northern scs have shifted from eawm glacial to enso interglacial over the past 24 kyr this article is protected by copyright all rights reserved

late quaternary paleoceanography as recorded by benthonic foraminifera in strait of sicily sediment sequences at specific times during the late quaternary a widespread low salinity surface water layer was produced over the eastern mediterranean which created stagnant conditions and associated deposition of sapropelic muds in the deep basins the strait of sicily has been positioned above the anoxic deeper water masses and is therefore devoid of sapropel deposits sediment sequences in the region contain a valuable record of upper bathyal 200 1000 m benthonic foraminiferal change during times of deep basin stagnation quantitative examiniation of benthonic foraminiferal assemblages in strait of sicily quaternary cores generally reveals changes coeval with sapropels s1 s2 s4 s5 and s6 the benthonic foraminiferal expression is seen as increases in frequency ofglobobulimina affinis globobulimina pseudospinescens chilostomella mediterranensis bolivina dilatata and otherbolivina species during intervals corresponding to the episodic abyssal stagnation events some cores also display a decrease incassidulina carinata and an increase inarticulina tubulosa similar assemblage changes have been previously documented to be closely associated with the sapropel layers in the deep basins of the eastern mediterranean the actual sapropel layers usually do not contain benthonic foraminifera however in the strait of sicily area the species exhibit less drastic changes than in the deep eastern basins because of the less severe anoxic conditions in the deep eastern basins benthonic foraminifera almost totally disappeared in sapropel layers at the same time there was a general reduction in foraminiferal numbers in the shallower strait area

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

planktonic foraminiferal records of east asia monsoon changes in the southern south china sea during the last 40 000 years planktonic foraminiferal assemblages and benthic foraminiferal oxygen isotopes were obtained in a gravity core n507 25 6 degrees 39 945 n 113 degrees 32 9361 e water depth 2006 m collected from the southern south china sea scs to investigate east asia monsoon changes during the last 40 000 years four cold events identified from four peaks of the relative abundance of neogloboquadrina pachyderma dex and globigerina quinqueloba correlate well with those in the hulu monsoon record within age uncertainty and can be linked to heinrich events in the northern atlantic high latitudes we suggest that the relative abundance of n pachyderma dex and g quinqueloba in the southern scs can be used as a direct proxy for east asia winter monsoon eawm changes during glacial periods in contrast to its low abundance in the northern scs and okinawa trough the relative abundance of pulleniatina obliquiloculata shows high values during the last glacial in the southern scs caused likely by the combined impact of optimum winter sea surface temperature sst and stronger mixing enhanced upwelling at that time a p obliquiloculata minimum event pme found in the okinawa trough and the northern and southern scs during the h1 period was possibly related to a large drop in winter sst due to the intensified eawm we propose that this pme can be also used as a reliable regional stratigraphic marker as the holocene one a 9 cm sandy silt layer deposit in core ns07 25 during the hi period probably related to the enhanced current that was caused by the especially strengthened eawm at that time the last deglacial warming recorded in the relative abundance of warm and cold species of planktonic foraminifer reveals that changes between the easm and eawm were not in phase but alternating between a winter monsoon dominated northern hemisphere influence and a summer monsoon dominated influence of the tropical dynamics and or southern hemisphere climate changes c 2009 elsevier b v all rights reserved

compositions of foraminifera rich turbidite sediments from the shenhu area on the northern slope of the south china sea implication for the presence of deep water bottom currents abstract the sediments in gravity core dh 1 collected from shenhu area on the northern slope of the south china sea are composed of two dark grey clay silt layers a1 and a3 and two foraminifera rich layers a2 and a4 a1 is the top layer and a4 is the bottom layer major and trace metal contents along with grain size and mineralogic data suggest that these silt layers represent background hemipelagic sedimentation unlike silt layers the intervening foraminifera rich layera4 exhibits a fining upward trend is distal turbidite grain size cm diagram and the sharp contacts between the foraminifera rich layer a2 and the upper and lower layers suggest layer a2 is the result of depositional interaction between turbidite and bottom currents ams 14c dating of planktonic foraminifera indicate the age of the turbidite in a2 is between15 3 ka and 22 6 ka we hypothesize that turbidite formation in this period was related to the increase supply of terrigenous matter since the last glacial maximum the rapid deposition of each turbidite led to reduced rates of oxygen diffusion into the sediment allowing anoxic conditions develop in sediments and fostering u enrichment 3 1 g g in foraminifera rich layer a4b in contrast decrease concentration of u and u mo ratios in foraminifera rich layera2 which is possibly due to u remobilization as a consequence of downward penetration of the oxidation front from the oxygen rich bottom currents these new data suggest that authigenic u was quite sensitive to the inflow of bottom currents and u mo ratios may indicate the depositional environmental change in relation to the bottom current action on the turbidite

late quaternary deep ocean circulation a review of paleoceanographic studies dealing with late quaternary deep water circulation in the oceans is presented these studies which are based on the analysis of deep sea benthic foraminiferal faunal and geochemical data and sedimentological data are discussed in light of physical oceanographic conditions in the modern ocean we include in this review a re evaluation of benthic foraminiferal data from north atlantic and southern ocean piston cores and suggest that the dominance of uvigerina during glacial intervals reflects increased amounts of organic carbon at the sea floor compared to modern values a number of geochemical studies have suggested that the production or characteristics of north atlantic deep water nadw changed during glacial times although these changes have been thought to result from a cessation of overflow water from the norwegian greenland seas it is suggested here that seasonal sea ice cover was possible over southern portions of the norwegian sea during glacial intervals the presence of seasonally open water would have allowed norwegian sea overflow water to have been produced although perhaps at lower volumes and with different hydrographic properties than at present the record of antarctic bottom water aabw circulation does not show a simple relationship with paleoclimatic oscillations indicating that changes in oceanographic conditions in the southern ocean had little effect on aabw formation the aabw record contrasts with the glacial interglacial cycles of nadw suggesting no direct link between aabw and nadw circulation a variety of data suggests that changes in pacific deep water circulation occurred as a result of glacial production of north pacific deep water or from an increased flux of southern ocean water

late quaternary paleoceanography of the south china sea surface circulation and carbonate cycles paleoceanographic information from 34 sediment cores is summarized to investigate the glacial interglacial variations in sea surface circulation and late quaternary carbonate cycles in the south china sea judging from the distribution pattern of deposition rates the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods paleotemperature maps based on transfer function temperature estimates have revealed a e w gradient of sst for glacial summer and a s n gradient for glacial winter and this agrees well with the clockwise surface circulation in summer and counterclockwise in winter during glacials as shown by a preliminary computer modelling the high resolution paleotemperature curves of core v36 3 from the northern slope show an abrupt cooling event which may belong to the younger dryas carbonate percentage in sediments and preservation of foraminifers and pteropods are used to study the carbonate cycles in the marginal sea it turns out that two mechanisms are functioning there being a basin with large drainage areas vast amount of river borne terrigenous input dilutes carbonate and its intensification during glacial decreases the glacial cac03 being a basin connected with the pacific the fluctuations of lysocline ccd and acd in the scs are related to those in the pacific ocean and dissolution is strengthened at interglacial thus above the present ccd the dilution factor predominates and the atlantic cycles are produced below the present ccd the dissolution factor prevails resulting in the pacific pattern of carbonate cycles

late quaternary changes in surface water and deep water masses of the nordic seas and north eastern north atlantic a review quantitative and semiquantitative proxy data based on more than 200 core top samples and 100 deep sea cores lead to important new insights about late quaternary changes in paleo oceanography climate and microfaunal habitats in the north eastern north atlantic and nordic seas insights resulting from a detailed investigation by the kiel research project sfb 313 132 summarized in this paper planktonic foraminifera species provide reliable tracers of past sea surface temperatures and currents the genus beella in particular was found to trace subtropical water masses up to the far north benthic foraminifera species served as sensors of bottom currents and local flux rates of organic matter new orders of time resolution are reached via stable isotope stratigraphy and accelerator mass spectrometry carbon 14 dating allowing the identification of meltwater events lasting a few hundred years and shorter a time range where however the yet unquantified role of bioturbation presents a growing problem based on this high resolution stratigraphy a number of time slices synoptic time intervals are defined to reconstruct the incursion of atlantic water masses to map paleocurrent patterns within the nordic seas and the north eastern north atlantic and to test alternative circulation models for example for the last glacial maximum lgm and various meltwater episodes these are clearly coeval with dansgaard oeschger events found in greenland ice cores with the actual cause of the flickering climate as yet unknown likewise there is ongoing controversy about the extent of past sea ice cover and about possible changes from the present anti estuarine to estuarine mode of deep water exchange between the north atlantic and the nordic seas during the lgm south of iceland however the history of deep water renewal over the last glacial cycle covering the last 30000 years was largely deciphered

foraminiferal isotopic evidence for monsoonal activity in the south china sea a present lgm comparison abstract the relationship between planktonic and benthic foraminiferal stable isotope values and oceanographic conditions and factors controlling isotopic variations are discussed on the basis of oxygen and carbon isotopic analyses of 192 modern surface and last glacial maximum lgm samples from the south china sea scs the harmonic variation of benthic 18o in surface sediments with water depth and temperature implies that the temperature is the main factor influencing benthic 18o variations planktonic 18o fluctuates with sea surface temperature sst and salinity sss the n s temperature gradient results in planktonic 18o decreasing from the northeast to the south cool saline waters driven by the winter monsoon are interpreted to have been responsible for the high 18o values in the northeast scs the east asian monsoons not only bring nutrients into the south china sea and maintain high nutrient concentration levels at the southwestern and northeastern ends which cause depleted 13c both in planktonic surface and benthic bottom samples but also reduce planktonic benthic 18o differences the distribution of 18o and 13c in the surface and lgm samples are strikingly similar indicating that the impact of sst and sss has been maintained and nutrient inputs mainly from the northeastern and southwestern ends have been controlled by monsoons since the lgm comparisons of the modern and lgm 18o indicate a difference of about 3 6 c in bottom water temperature and a large surface to bottom temperature gradient during the lgm as compared to today

coccolith evidence for quaternary nutricline variations in the southern south china sea abstract nutricline variations during the last 1560 ka in the southern south china sea are reconstructed using the relative abundance of the coccolithophore florisphaera profunda in odp site 1143 nutricline depth shows both long term large magnitude variation and high frequency glacial interglacial variation on the long term scale the nutricline experienced four significant changes which occurred at 900 480 250 and 50 ka respectively according to these changes five stages could be recognized during the last 1560 ka from 1560 to 900 ka the nutricline depth increased gradually around 900 ka the nutricline abruptly shallowed and then remained stable until 480 ka the nutricline was shallow during the time interval between 480 and 250 ka at 250 ka it deepened again and increased gradually until 50 ka after 50 ka the nutricline depth decreased gradually to modern values on the glacial interglacial scale the variations in nutricline depth show different patterns before and after 900 ka before 900 ka the nutricline was deep during glacial periods and shallow during interglacials however after 900 ka the nutricline was deep during interglacials and shallow during glacials spectral analysis of the relative abundance of f profunda shows a similar trend in addition to the eccentricity 113 76 ka obliquity 55 39 ka and precession 24 19 ka we also find a 431 ka cycle the former three periods reflect glacial interglacial variations in nutricline and the period of 431 ka reflects long term variations in nutricline we suggested that the variations in nutricline in the southern south china sea were caused by global and regional climate changes glacial interglacial variations in nutricline are mainly controlled by the east asian monsoon and the long term variations might be related to the global climatic events such as the mid pleistocene revolution and the mid brunhes event

environmental distribution of recent benthic foraminifera on the northeast united states continental slope several bathymetrically consistent recent benthic foraminiferal biofacies have been recognized from the continental slope south east of cape cod faunal assemblages are dominated by globobulimina bulimina upper slope less than 1 000 m and uvigerina peregrina lower slope uppermost rise water depths between 1 000 and 2 500 m the globobulimina bulimina assemblage coincides with the oxygen minimum zone this agrees with the occurrence of globobulimina in mediterranean sapropels organic rich sediments deposited under anoxic conditions previous studies have noted the association of u peregrina with bathyal water depths deep water temperatures of 3 to 4 c and water of low oxygen content however correlations between abundance of u peregrina and water depth or temperature are not the same everywhere and no correlation with dissolved oxygen in the water column is seen on the united states continental slope and rise the highest abundances of u peregrina coincide with maxima of organic carbon and silt within the slope sediments this suggests that the distribution of u peregrina in this region may be influenced more by low oxygen in the sediments rather than by low oxygen content of the overlying water

western equatorial pacific productivity and carbonate dissolution over the last 550 kyr foraminiferal and nannofossil evidence from odp hole 807a we analyzed foraminiferal and nannofossil assemblages and stable isotopes in samples from odp hole 807a on the ontong java plateau in order to evaluate productivity and carbonate dissolution cycles over the last 550 kyr kilo year in the western equatorial pacific our results indicate that productivity was generally higher in glacials than during interglacials and gradually increased since mis 13 carbonate dissolution was weak in deglacial intervals but often reached a maximum during interglacial to glacial transitions carbonate cycles in the western equatorial pacific were mainly influenced by changes of deep water properties rather than by local primary productivity fluctuations of the estimated thermocline depth were not related to glacial to interglacial alternations but changed distinctly at similar to 280 kyr before that time the thermocline was relatively shallow and its depth fluctuated at a comparatively high amplitude and low frequency after 280 kyr the thermocline was deeper and its fluctuations were at lower amplitude and higher frequency these different patterns in productivity and thermocline variability suggest that thermocline dynamics probably were not a controlling factor of biological productivity in the western equatorial pacific ocean in this region upwelling the influx of cool nutrient rich waters from the eastern equatorial pacific or of fresh waters from rivers have probably never been important and their influence on productivity has been negligible over the studied period variations in the inferred productivity in general are well correlated with fluctuations in the eolian flux as recorded in the northwestern pacific a proxy for the late quaternary history of the central east asian dust flux into the pacific therefore we suggest that the dust flux from the central east asian continent may have been an important driver of productivity in the western pacific c 2007 elsevier b v all rights reserved

recent deep sea benthic foraminiferal distributions in the south china and sulu seas thirty nine surface sediment samples collected from the south china and sulu seas were examined to determine the bathymetric distribution of benthic foraminifera in these two basins and the factors responsible for these distributions the benthic foraminiferal faunas of both basins are highly diverse but have low absolute abundances benthic number and species diversity systematically decrease with increasing water depth four faunal assemblages were identified for each basin byq mode principal component analysis theglobocassidulina subglobosa uvigerina assemblage 1500 m and theuvigerina assemblage 1400 m represent the shallowest assemblages in the south china sea and sulu sea respectively and are found within the oxygen minimum zone of each basin where the sedimentary organic carbon content is highest and the pore water oxygen penetration depth zo is shallowest thebulimina aculeata assemblage occurs at water depths between 1700 and 2000 m in the southeastern south china sea and is also associated with relatively high sedimentary organic carbon content theastrononion pusillum assemblage is found in south china sea at the depths between 1500 and 3200 m below the lysocline 3200 m in the south china sea this assemblage is replaced by the agglutinatedrhabdammina abyssorum assemblage this assemblage reflects the presence of a water mass that is highly undersaturated with respect to calcite in the sulu sea thepyrgo murrhina assemblage occupies water depths from 1400 to 2200 m below 2200 m two deep water assemblages are present that are both dominated byoridorsalis umbonatus a correlation between various environmental and benthic foraminiferal variables indicates that salinity temperature sediment grain size water depth and bottom water oxygen concentration are not key factors controlling the benthic foraminiferal distribution in either the south china sea or the sulu sea rather organic carbon content and oxygen penetration depth in sediments appear to play important roles in determining the distribution of benthic foraminifera in both basins