a synthesis of lead isotopes in two millennia of european air four airborne particulate records from ombrotrophic peat bogs in southern norway extending back 300 years have been measured for chronology lead concentration and lead isotope composition since southern norway receives an airborne lead signal that accumulates emissions from the european continent the trend in the four bog records can be used to correlate previously reported measurements from france switzerland england and greenland that cover different ranges of time when these are compiled the integrated european record that emerges spans the last 2300 years of human influence on lead in the air over europe and suggests human control of lead in airborne particulates over the entire period from 366 bc through the first half of the 20th century lead isotopic compositions in european air have fallen within the range of compositions in european ore bodies since 1950 isotopic compositions have been beyond the range in those ore body compositions and have fallen within the array of lead isotope compositions typical of gasoline from western industrial nations a mixing line between us and australian lead in gasoline the overlap between the european record and the range in modern european air suggests an average isotopic composition of 206 pb 207 pb ca 1 13 and of 208p b 207 pb ca 2 41 in air over europe during the last 20 years 1999 elsevier science b v all rights reserved

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

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

climatic change and caco3 preservation an 800 000 year bathymetric reconstruction from the central equatorial pacific ocean sixteen deep sea cores from the central equatorial pacific are used to reconstruct a continuous 800 000 year 800 kyr record of bathymetric variations in carbonate preservation as measured by calcium carbonate caco3 content the depth of the sedimentary lysocline has fluctuated markedly in conjunction with late pleistocene climate cycles while the carbonate critical depth ccrd which is the water depth where the sediments contain 10 caco3 has remained relatively constant as a result the depth of the lysocline controls the bathymetric position and thickness of the caco3 transition zone defined as the depth from the lysocline to the ccrd modern and interglacial aged sediments show poor caco3 preservation and thick caco3 transition zones glacial aged sediments show good preservation and deep thin zones due to the deepening of the lysocline detailed comparison of the caco3 preservation and oxygen isotope records from the central equatorial pacific confirms the observation that preservation maxima and minima tend to occur during the latter half of glacial and interglacial stages and on climate transitions rather than during the middle of climatic stages during the nine major glacial stages of the last 800 kyr the lysocline deepened by at least 400 to 800 m this deepening indicates an increase in the abyssal carbonate ion concentration co3 and a depression of the calcite saturation horizon best explained by the deeper presence of a more carbonate saturated water mass the bottom of the transition zone has remained at a relatively constant depth during the brunhes chron indicating a balance between caco3 sedimentation and dissolution in the deepest waters of the central equatorial pacific

geomagnetic paleointensity dating of south china sea sediments for the last 130 kyr relative paleointensity records from the northern south china sea northwest pacific ocean were studied in two gravity piston cores continuous mineral magnetic and paleomagnetic measurements were made using discrete sediment samples detailed rock magnetic parameters such as thermomagnetic and high field hysteresis data indicate that pseudo single domain magnetite in a narrow range of grain size and concentration is the main contributor to the remanent magnetization the uniform magnetic mineralogy meets the commonly accepted criteria for establishing relative paleointensity records the relative paleointensity rpi curves were constructed by normalizing the natural remanent magnetization nrm with isothermal remanent magnetization irm both in the 20 60 mt demagnetization state dating constraints have been provided by radiocarbon ages in the upper 400 cm of both cores furthermore we have correlated our paleointensity records with napis 75 s atlantic 1089 sint 200 and nopapis 250 to determine the chronological rpi framework for the south china sea scs pis although some temporal offsets of paleointensity features between the different records have been recognized their similar shape suggests that relative paleointensity on the 10 3 10 4 year scale is globally coherent and can provide an age framework for sediments independent of delta 18 o ages c 2009 elsevier b v all rights reserved

planktonic foraminifera in the western north pacific during the past 150 000 years comparison of modern and fossil assemblages abstract planktonic foraminiferal abundance variations in 186 deep sea piston core tops from the western north pacific were used to create a calibration set to characterize the present day kuroshio gyre system q mode factor analysis helped identify six faunal assemblages 93 variance related to modern water masses two tropical assemblages differing in relative dissolution three assemblages representing subtropical subpolar and transitional conditions and a gyre margin assemblage lying between the kuroshio current and the mainland of asia multivariate regression produced transfer functions relating observed summer august and winter february sea surface temperatures sst to the assemblages with standard errors of estimate of 1 5 c and 2 5 c respectively data from 24 piston cores was used to interpret variations of the kuroshio gyre system during the past 150 000 yr stratigraphic control is based on oxygen isotopic measurements the extinction of pink pigmented globigerinoides ruber at 120 000 b p coiling direction changes in neogloboquadrina pachyderma north of 30 n and dissolution variations between resistant and fragile taxa major dynamic changes in the circulation of the kuroshio gyre occurred during the last two glacial maxima at 15 20 000 b p isotopic stage 2 and at 140 150 000 b p isotopic stage 6 these intervals are characterized by 1 lowered sea levels which reduced flow into the sea of japan and sea of okh okhotsk 2 advance of the polar front from its modern position at about 42 n to 35 38 n 3 southward penetration of the oyashio current along the pacific coast of japan to tokyo 4 2 3 c lowered sst in tropical areas little or no change in subtropical areas and a 4 6 c decrease in transitional areas and 5 an overall decrease in carbonate dissolution relative to interglacial stages the maximum interglacial at 120 000 b p isotopic substage 5e shows a retreat of the polar front north of its modern position and an overall relative increase in interglacial carbonate dissolution that does not become severe until substage 5d

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

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

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

paleoceanography of the south china sea since the middle miocene evidence from planktonic foraminifera late middle miocene to pleistocene planktonic foraminifera pf in fairly continuous hemipelagic sediments recovered at ocean drilling program odp site 1143 from the southern south china sea scs were studied with sampling intervals of 10 to 150 cm a total of 16 pf events are revised for the 516 m long section providing an age model for the last 12 ma at this site on the basis of benthic foraminiferal d 18 o stratigraphy and the smoothed planktonic age model new ages are assigned to three pf events last occurrence lo globorotalia multicamerata sensu lato s l at 2 18 ma first occurrence fo sphaeroidinella dehiscens sensu stricto s s at 3 6 ma and fo globigerinoides conglobatus at 6 6 ma in the south china sea distinct pf faunal transition from globorotalia siakensis g mayeri group to mixed layer species occurred during the early late miocene 9 6 ma the transition reflects a deepened upper water thermocline possibly corresponding to the closure of the indonesian seaway and intensification of equatorial pacific warm currents abundance variations of neogloboquadrina spp indicate a marked shoaling of the thermocline in the northern south china sea after 3 2 5 ma affected possibly by a strengthened asian winter monsoon while a deeper thermocline existed in the southern south china sea since the late miocene characterizing the west pacific bwarm poolq wpwp a deepening thermocline influenced by consistently warm surface water since the late miocene in the southern south china sea is also evidenced by a two stepwise increase of pulleniatina group by a gradually decreasing sphaeroidinella sphaeroidinellopsis spp and abundant globorotalia menardii and related species the fo globigerinoides ruber pink at approximately 1 ma and an abrupt increase in the pink to all ratio of g ruber at 0 4 ma at site 1143 provide two additional pf events for deciphering pleistocene biostratigraphy and paleoceanography d 2004 elsevier b v all rights reserved

millennial scale dynamics of the winter cold tongue in the southern south china sea over the past 26 ka and the east asian winter monsoon millennial scale variations of the east asian winter monsoon eawm remain elusive due to sparse and controversial reconstructions by compiling a variety of alkenone based sea surface temperature sst estimates we find that the west east sst gradient in the southern south china sea scs well documents the temporal dynamics of the winter cold tongue off the southern vietnam and by inference variations in the eawm intensity over the past 26 ka our results reveal that the winter cold tongue ssts were significantly colder during heinrich event 1 and the younger dryas event resulting in an increased west east sst gradient in the southern scs due to a strengthened eawm within dating uncertainties an intensified eawm during cold stadials was coeval with the shutdown or a reduction in strength of the atlantic meridional overturning circulation amoc exhibiting a strong linkage between the amoc and the eawm system the west east sst gradient also indicates an enhanced eawm during the early holocene which may be induced by postglacial ice sheet dynamics and a strong seasonal contrast in solar insolation our findings suggest that the eawm was probably modulated by a complex interplay between the amoc solar insolation and ice sheet dynamics on sub orbital time scales

pleistocene paleoceanography of the south china sea progress over the past 20 years article i nfo the south china sea scs has become one of the foci in paleoceanographic research and hydrocarbon explora tions over the last 20 years over the period at least 16 international cruises including odp ocean drilling pro gram leg 184 have investigated the scs and more than 2000 exploratory wells have been drilled the present paper attempts to synthesize progress in pleistocene paleoceanography because of the high depositional rates and favorable carbonate preservation the scs keeps valuable paleoceanographic archives for the low latitude pacific region which have helped to uncover potential ties between the low latitude oceanic biogeochemical evolution and step wise development of the boreal ice sheet it has been found that the 1 6 ma event marked a reorganization of the oceanic carbon reservoir associated with the restructuring of the southern and the tropical pacific ocean the mpt mid pleistocene transition and mbe mid brunhes event centered at 0 9 ma and 0 4 ma respectively were preluded by carbon isotope maxima 13 cmax iii and 13 cmax ii suggesting that major steps in the ice sheet development were preceded by significant changes in oceanic biogeochemistry the late pleistocene records have demonstrated the amplifying role of the scs in responding to glacial cycles as the amplitudes of sst and 18 ov ariations have been significantly amplified in the scs as compared with the open ocean at the same latitudes the amplification is ascribed to its semi enclosed morphology and the prevail ing monsoon climate the closure of the southern margin during glacial times led to stratification of the upper waters and specific faunal changes in the southern scs the seasonally reversing monsoon winds not only drive the surface circulation but also the biological production the n s gradient in oceanography and the sed iment transportdynamics such asthe asymmetric growth of the mekong river delta becauseof its distinguished position in the low latitudes between the largest continent and the largest ocean the scs provides important insight into the mechanism of environmental evolution with regards to ocean continent or high low latitude interactions

seasonal variations of modern planktonic foraminifera in the south china sea although foraminiferal census and isotope analyses from sediment cores have been widely applied to paleoceanographic reconstructions in the south china sea scs their modern counterparts i e foraminiferal shells from sediment traps and plankton tows have been the subjects of few studies in this region in this investigation relative abundances of the most popular species used to reconstruct late quaternary tropical sea surface conditions have been studied in plankton tows from the scs in order to offer better constraints on the interpretation of downcore records in addition to the seasonal differences the spatial variations in the faunal assemblage are evident from south to north in the scs basin based on contemporary tows for example the species globigerinella aequilateralis is found to be relatively dominant in the southern lower latitude basin but its relative abundance is significantly higher in planktonic tows than in sediments indicating its proneness to burial dissolution pulleniatina obliquiloculata an index taxon for the kuroshio current is only abundant in the northern part of the scs basin the measured oxygen isotope compositions 18o of globigerinoides ruber globigerinoides sacculifer neogloboquadrina dutertrei and p obliquiloculata all show a good relationship with temperature in the mixed layer tmix the carbon isotope compositions 13c also display a positive distribution pattern relative to tmix but with a less significant correlation in winter months than 18o differences of 18o between shallower g sacculifer and g ruber and deep dwellers n dutertrei and p obliquiloculata accurately record the temperature gradient between the surface mixed layer and 100 m water depth supporting application of this proxy to the reconstruction of upper water column stratification

analysis of vegetation and climate change during late pleistocene from ziro valley arunachal pradesh eastern himalaya region abstract vegetation and climate during later part of late pleistocene have been reconstructed from ziro valley arunachal pradesh eastern himalaya based on pollen data along with carbon isotope and magnetic susceptibility data the study reveals that the area and the vicinity is occupied by mixed broad leaved conifer forest and pine grass savanah at variable densities at least since 66 000yr bp the phases of expansions and declines of oaks with decline and increase of pines and grasses probably occurred under increase warm moist and decrease cool dry of s w monsoon precipitation respectively the increasing trend of s w monsoon and temperature is recorded during 44 000 to 34 000 cal yr bp synchronizing with the peat development and which peaked at around 35 000 cal yr bp this may link to the interstadial phase during the last major glacial cycle in the himalayan region it is also reflected in the decline of 13c value indicating dominance of c 3 type of vegetation the increased values of fd and lower values lf magnetic susceptibility recorded during the phase of the peat deposit further advocate s higher monsoon intensity impact of expansion of glacier felt with peak lgm around 20 000 cal yr bp is perceived tree line had moved to lower altitudes due to increased aridity and low temperature during this time existence of savannah type of vegetation is also evident by the increase of c4 taxa decreased fd and increased lf susceptibility also indicate reduced s w monsoon intensity

last glacial maximum in china comparison between land and sea abstract as a result of the sea level drop at the last glacial maximum about 100 120 m in the south china sea and 130 150 m in the east china sea the size and configurations of the china seas changed greatly the east china sea with the yellow sea and bohai gulf was reduced into an elongated trough while the south china sea became a semi enclosed gulf due to the southern shift of the polar front in the north pacific and the reorganization of the surface current system the winter temperature in the south china sea was 6 10 c colder and the seasonality was much stronger than it is now the reduced sea area and thus the increased distance to the coast together with the declined sea surface temperature led to intensified aridity on the land the enhanced eolian processes related to the intensification of the winter monsoon caused an expansion of the loess deposition area reaching the southeastern part of china to the south of the yangtze river and off the modern sea coast vegetation zones greatly shifted to the southeast in north china deserts and steppes were much more extensive than they are now and the modern areas of warm temperate broad leaved forests were occupied by steppes or woodland in south china the deciduous broadleaved forests were developed in areas now covered by evergreen forests and the monsoon rain forest completely disappeared the changes in the climate on land and the configurations of seas altered the sediment supply and sedimentation rate in the china seas giving rise to the atlantic type late quaternary caco3 curve there

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

clay mineral assemblages in the northern south china sea implications for east asian monsoon evolution over the past 2 million years abstract clay mineral assemblages at odp site 1146 in the northern south china sea are used to investigate sediment source and transport processes and to evaluate the evolution of the east asian monsoon over the past 2 myr clay minerals consist mainly of illite 22 43 and smectite 12 48 with associated chlorite 10 30 kaolinite 2 18 and random mixed layer clays 5 22 hydrodynamic and mineralogical studies indicate that illite and chlorite sources include taiwan and the yangtze river that smectite and mixed layer clays originate predominantly from luzon and indonesia and that kaolinite is primarily derived from the pearl river mineral assemblages indicate strong glacial interglacial cyclicity with high illite chlorite and kaolinite content during glacials and high smectite and mixed layer clay content during interglacials during interglacials summer enhanced monsoon southwesterly currents transport more smectite and mixed layer clays to site 1146 whereas during glacials enhanced winter monsoon northerly currents transport more illite and chlorite from taiwan and the yangtze river the ratio smectite mixed layers illite chlorite was adopted as a proxy for east asian monsoon variability higher ratios indicate strengthened summer monsoon winds and weakened winter monsoon winds during interglacials in contrast lower ratios indicate a strongly intensified winter monsoon and weakened summer monsoon during glacials spectral analysis indicates the mineral ratio was dominantly forced by monsoon variability prior to the development of large scale glaciation at 1 2 myr and by both monsoon variability and the effects of changing sea level in the interval 1 2 myr to present

comparison and implication of tex86 and u37k temperature records over the last 356kyr of odp site 1147 from the northern south china sea abstract proxy records from the south china sea scs have played an important role in understanding late quaternary scs environmental changes and the east asian monsoon eam variations but few long sea surface temperature sst records have been generated from the scs the recently established tex86 index provides an opportunity to generate long sst records especially for tropical oceans but the applicability and climatic interpretation of the tex86 index for the scs need further study we report and compare orbital scale resolution ca 5 3 kyr tex86 and u37k temperature records of the past 356 kyr for odp site 1147 from the northern scs both records display clear and similar glacial interglacial patterns the u37k sst fluctuated between 22 3 c and 28 3 c with a glacial interglacial difference of 4 5 c while the tex86 temperature fluctuated between 20 3 c and 25 4 c with a slightly smaller glacial interglacial difference of ca 4 c the tex86 temperature has been consistently lower than the u37k temperature over the past 356 kyr consistent with previous studies suggesting that the u37k index is a proxy for sst but the tex86 index is a proxy for subsurface temperature thus it is proposed that the temperature difference t between the u37k and tex86 records reflects mixed layer depth mld changes in the northern scs which fluctuated between 0 3 and 4 0 c with high values mostly during interglacials and lower values mostly during glacial stages mld changes in the northern scs are interpreted to be driven by eam changes with stronger winter monsoon resulting in a deeper mld and a smaller t thus the combination of u37k and tex86 records and their t can be used to reconstruct east asian winter monsoon variations as well as their influences on the hydrographic structure of the scs

summer monsoon induced upwelling dominated coastal sea surface temperature variations in the northern south china sea over the last two millennia the south china sea scs situated to the north of the indo pacific warm pool ipwp is under the strong influence of the asian monsoon system however coastal sea surface temperature sst reco

palaeoceanographic change in the northeastern south china sea during the last 15000 years the sedimentary succession of piston core rc26 16 dated by 14 c accelerator mass spectrometry provides a nearly continuous palaeoceanographic record of the northeastern south china sea for the last 15 000 yr planktic foraminiferal assemblages indicate that winter sea surface temperatures ssts rose from 18 c to about 24 c from the last glacial to the holocene a short lived cooling of 1 c in winter temperature centred at about 11 000 14 cy r ago may reflect the younger dryas cooling event in this area summer ssts have remained between 27 c and 29 c throughout the record the temperature difference between summer and winter was about ca 9 c during the last glacial much higher than the holocene value of ca 5 c during the late holocene a short lived cooling event occurred at about 4000 14 cy r ago oxygen and carbon isotopic gradients between surface 0 50 m and subsurface 50 100 m waters were smaller during the last glacial than those in the holocene the fluctuation in the isotopic gradients are caused most likely by changes in upwelling intensity smaller gradients indicate stronger upwelling during the glacial winter monsoon the fauna derived estimates of nutrient content of the surface waters indicate that the upwelling induced higher fertility and biological productivity during the glacial the winter monsoon became weaker during the holocene the carbonate compensation depth and foraminiferal lysocline were shallower during the holocene except for a short lived deepening at about 5000 14 c yr ago a preservation peak of planktic foraminifera and calcium carbonate occurred between 13400 and 12 000 14 c

global nature of the younger dryas cooling event inferred from oxygen isotope data from sulu sea cores the younger dryas an approximately 1 000 year long return to near glacial conditions interrupted the glacial holocene climate transition during which most of the northern hemisphere ice sheets melted evidence for the younger dryas event has been found mainly in sediments from the north atlantic ocean and northwest europe and this has led to the idea that the event was caused by an injection of meltwater into the north atlantic ocean1 3 this model however has been recently questioned in the light of coral reef data on the rate of sea level changes during this transition4 here we present high resolution oxygen isotope records from benthic and planktonic foraminifera from two radiocarbon dated cores in the sulu sea showing that the younger dry as occurred synchronously in the surface and deep waters of the sulu sea and the northern atlantic ocean by combining our results with other palaeoclimate data we suggest that the younger dry as event was a global phenomenon and we believe it to have been caused by low atmospheric co2concentrations

carbonate deposition and benthicδ13c in the subarctic pacific implications for changes of the oceanic carbonate system during the past 750 000 years abstract carbonate deposition at two core sites in the subarctic pacific 48 n 133 w 2 9 km and 3 7 km water depth follows the standard pacific carbonate cycles with glacial values being increased over interglacial values benthic 13c follows the global trend that is glacial values are more negative than interglacial values comparison with the benthic 13c record of north atlantic dsdp site 552 56 n 23 w 2 3 km water depth shows the north pacific records to be nearly in phase with and continuously more negative relative to the north atlantic record this suggests that concentrations of co2 org were permanently higher in the north pacific than in the north atlantic during the past 750 000 years conceivably supporting the hypothesis that there was no deep water forming in the late pleistocene north pacific whereas one would expect that the north pacific deep waters were continuously more corrosive to carbonates than deep waters in the north atlantic carbonate deposition at the deep north pacific core sites is enhanced during glacial periods and occasionally higher than at shallow north atlantic site 552 even though site 552 was probably above lysocline depth during most of the late pleistocene this apparent paradox can be resolved only by invoking an increase in alkalinity in the glacial north pacific which would have increased the degree of carbonate ion saturation and thereby improved the state of carbonate preservation

a test of different factors influencing the isotopic signal of planktonic foraminifera in surface sediments from the northern south china sea abstract the stable isotope composition of planktonic foraminifera is one of the most important proxies in paleoenvironmental research in this study three parameters affecting the stable isotope values of globigerinoides ruber from surface sediment from the northern south china sea were tested different cleaning methods different morphotypes and different size fractions our results show that in the small size fraction there is a small but significant effect on 13c by oxidizing the tests prior to measurement our data also confirm a small but significant difference between different morphotypes of g ruber however the variability caused by the seasonal effect stable isotope value is larger than the effect caused by different cleaning protocols or different morphotypes the large spread of the isotope values up to 2 have some implications to paleoceanographic reconstructions when measurements are performed on a small number of foraminiferal tests the isotope value does not necessarily reflect yearly average or a certain season but is a random value of the seasonal variability in that region

rate of production dissolution and accumulation of biogenic solids in the ocean the equatorial current system by its response to global circulation changes provides a unique recording mechanism for long range climatic oscillations a permanent record of the changes in rate of upwelling and organic production is generated in the equatorial deep sea sediments particularly by such biogenic components which are unaffected by secondary dissolution in order to determine the rates of accumulation of various sedimentary components a reliable differential measurement of age of the strata must be obtained various approaches to this problem are reviewed and sources of error discussed secondary dissolution of calcium carbonate introduces a substantial and variable difference between the dissolution modified and hence a priori unknown rate of deposition on one hand and the rate of accumulation derivable from the observed concentration on the other the cause and magnitude of these variations are of importance particularly since some current dating schemes are based on assumed constancy in the rate of accumulation of this and in some cases also all other sedimentary components the concepts used in rate evaluation are discussed with emphasis on the difference between the state of dissolution an observable property of the sediment and the rate of dissolution a parameter that requires deduction of the carbonate fraction dissolved and of the time differential as a most likely cause of the enhanced state of dissolution of the interglacial carbonate sediments is proposed the lowered rates of biogenic production and deposition which cause longer exposure of the carbonate microfossils to corrosion in the bioturbated surface layer of the sediment historical perspective is included in the discussion in view of the dedication of the symposium to hans pettersson the leader of the swedish deep sea expedition 1947 1948 an undertaking that opened a new era in deep sea research and planetary dynamics

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

development of the east asian monsoon and northern hemisphere glaciation oxygen isotope records from the south china sea abstract oxygen isotope records of the surface dwelling foraminifer globigerinoides ruber from odp site 1143 in the southern south china sea scs are presented for the last 5 ma the g ruber 18o of site 1143 for the past 500 ka is lighter by 0 5 1 0 in interglacial and by 0 1 0 5 in glacial periods than the site 806b record from the ontong java plateau we infer the light glacial interglacial g ruber 18o at site 1143 compared with the open western pacific to have been caused by stronger monsoon induced precipitation over the scs while glacial interglacial planktonic 18o values remained stable over the 3 3 2 5 ma period the benthic cibicidoides wuellerstorfi 18o gradually became positive leading to an obvious slope in their 18o difference 18ob p the stable glacial interglacial g ruber 18o over this period is probably caused by the decrease of sea surface salinity which counteracted the effects of global ice volume and sea surface temperature on the g ruber 18o we interpret that the intensification of the east asian monsoon winds coupled with the northern hemisphere glaciation 3 3 2 5 ma ago likely brought frequent and strong precipitation over the scs and or caused large scale intrusions of borneo alongshore low salinity waters to the southern scs which greatly freshened the scs and decreased its salinity after 2 5 ma especially in the quaternary period the planktonic and benthic 18o show similar variations over glacial interglacial cycles in responding to the waxing and waning of the northern hemisphere continental ice sheet and their relatively stable 18o difference 18ob p indicates a period of steady fluctuations of the east asian monsoon winds the more positive values of 18ob p probably suggest stronger east asian winter monsoon during quaternary glacials whereas the more negative values of 18ob p may imply stronger east asian summer monsoon during quaternary interglacials

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr