u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

vegetation evolution based hydrological climate history since lgm in southern south china sea abstract the reconstruction of vegetation evolution and climate changes at low latitudes since the last glacial maximum lgm remains incomplete in this study we reconstructed the palynological history of vegetation changes since the lgm using a sediment core collected from the slope in the southern south china sea scs the chronology of the core was based on eight ams14c dates and 85 stratigraphic samples were palynologically analyzed our results denote that the vegetation reconstructed during the lgm in the southern scs was characterized by a relatively high percentage of herb pollen and a modest decrease in the number of fern spores suggesting a temperature decline and humidity change in this region further the preservation of a rich diversity of pollen from the tropical lowland rainforest indicated that the rainforests might have covered large areas of the exposed sunda shelf during the lgm the dynamic concentration of the pinus pollen in the core which is a proxy for the east asian winter monsoon eawm satisfactorily matched the changes in the atlantic meridional overturning circulation and australian indonesian summer monsoon especially during the heinrich stadial 1 this suggests that the climate at the high latitudes of the northern hemisphere can drive the intertropical convergence zone itcz southwards based on the enhanced eawm the southward shifting itcz may change the hydrological climate of the equator and the southern hemisphere the pteridophyte spores which are good regional precipitation indicators were positively correlated with the warm pool convection and inversely related with the eawm possibly indicating the considerable impact of the high latitude climate in the northern hemisphere on precipitation in the tropical regions our results indicate that during the last deglaciation the tropical hydrological changes were relatively moderate when compared with the drastic change observed at high latitudes and were attributed to the regulation of the el nino southern oscillation like state our sequence of pollen and spores from the southern scs can be used to observe the detailed dynamics of climatic evolution in tropical regions the results of this study are essential to understand the complicated climate processes and the relation between high and low latitudes

synchroneity of meltwater pulse 1a and the bolling warming new evidence from the south china sea a twofold decrease in long chain n alcane n nonacosane concentrations in a downcore record from the northern south china sea indicates a rapid drop in the supply of terrigenous organic matter to the open south china sea during the last deglaciation paralleled by an equally rapid increase in sea surface temperatures corresponding with the bolling warming at 14 7 ka the sudden drop in terrigenous organic matter delivery to this marginal basin is interpreted to reflect a short term response of local rivers to rapid sea level rise strongly implying that the bolling warming and the onset of meltwater pulse mwp 1a are synchronous this phase relation contrasts with the widely cited onset of this mwp 1a ca 14 ka and implies that previous studies postulating a weakening of deep water formation in the north atlantic due to massive meltwater discharge during mwp 1a need to be reevaluated

the old alluvium of singapore and the extinct drainage system to the south china sea in both sand quarry faces and boreholes the old alluvium of singapore is a matrix supported pebbly sand with minor beds of better sorted sands and clays the beds can be grouped into four textural classes pebbles coarse sand with fine pebbles medium to coarse sand clay and silt each with characteristic sedimentary structures the deposit appears to be the proximal facies of an ancient braided river alluvium of possible pleistocene age this widespread but scattered alluvium is found both on land and offshore on the sunda shelf in southeast asia it is believed to have been deposited during low sea levels in singapore the mineralogy of the grains forming the old alluvium suggests a mixed provenance of granitic and low grade metamorphic origin the volume and freshness of the deposited material indicate an environment of considerable relief seasonal rainfall and extremely active erosional processes conditions considerably different from the current ones the old alluvium was probably deposited by seasonal rivers which experienced periodic large floods such regional conditions could have prevailed over much of southeast asia at the time of deposition of the old alluvium

abrupt change of sediment records in the southern south china sea during the last glacial period and its environment significance abstract chemical compositions of sediments at core ns07 25 6 39 945 n 113 32 936 e water depth 2006 m are analyzed to discuss abrupt change of sediment records in the southern south china sea scs during the last glacial period and its environmental implications major and trace elements experienced three significant changes which occurred at 31 9 26 1 and 18 5 ka bp respectively at 31 9 ka bp when sea surface temperature remained relatively low terrigenous sediment flux increased but biogenic activities weakened greatly at 26 1 ka bp both terrigenous sediment flux and biogenic fractions number were steady however some elemental ratios changed noticeably at that time before 26 1 ka bp core sediments with low nb ta but high zr hf ratios were mainly derived from the paleo mekong and or molengraaff rivers exposed on the sunda shelf at that time after 26 1 ka bp sediments with high nb ta but low zr hf ratios probably relate to strengthened impact of deep water current since 18 5 ka bp sea level ascended rapidly from 110 m below the present terrigenous sediment flux decreased and biogenic activities strengthened continuously probably related with the east asian monsoon evolution

n alkane and pollen reconstruction of terrestrial climate and vegetation for n w africa over the last 160 kyr abstract proxy environmental records have been obtained for the last 160 kyr from the well studied odp site 658 ca 200 km west of cap blanc n w africa 20 5 n 18 35 w 2263 m water depth this collective assessment of several terrigenous proxies lithogenic fraction n alkane content and 13 c values and pollen counts provides a better understanding of the climate and vegetation history of the n w african hinterland the results indicate that for this site beneath the main dust pathway of the saharan air layer sal the dust flux increased during dry glacial periods but the amounts of pollen and n alkanes delivered were lower in accord with the decreased density of vegetation cover of their source areas the c 4 pollen was also very low but the heavy 13 c values of the n alkanes accorded with a mainly c 4 plant origin evidently the load of sal pollen was much reduced but not the sal wind strength

error analysis of paleosalinity calculations a detailed error analysis is performed for the calculation of open ocean salinity changes from carbonate oxygen 18 proxy data measurement errors are generally negligible however errors due to the goodness of fit of various regressions used in the calculation are significant depending on the method used and on the proxies available error bars 1 for the salinity range from 0 6 to 1 8 in particular expected errors for the midlatitude and tropical salinity differences at the last glacial maximum are around 1 1 to 2 5 the largest errors occur because of the differences between temporal and spatial seawater oxygen 18 salinity relationships and through the use of nonconcurrent temperature measurements methods of improving paleosalinity estimates should focus on eliminating these large sources of uncertainty

glacial interglacial organic carbon record from the makassar strait indonesia implications for regional changes in continental vegetation abstract recent studies convincingly show that climate in the western pacific warm pool and other equatorial tropical regions was significantly colder by 3 4 c during glacial periods prompting a reexamination of the late pleistocene paleoenvironments of these regions this study examines changes in continental vegetation during the last two deglaciations terminations i and ii using a sediment core md9821 62 recovered from the makassar strait indonesia evidence based on the lignin phenol ratios suggests that vegetation on borneo and other surrounding islands did not significantly change from tropical rainforest during the last two glacial periods relative to subsequent interglacial periods this supports the hypothesis that the winter monsoon increased in strength during glacial periods allowing indonesia to maintain high rainfall despite the cooler conditions

sea levels during late marine isotope stage 3 or older reported from the red river delta northern vietnam and adjacent regions abstract a 60 m long sediment core from the lower red river delta in northern vietnam contains three depositional sequences consisting mostly of regressive shallow marine sediments bounded by unconformities the youngest unit represents the modern red river delta the second unit a facies succession comparable to the overlying deltaic succession formed during an earlier sea level highstand as indicated by the marine isotope stage mis 3 age obtained by radiocarbon dating the third undated unit might reflect earlier high sea levels of the middle to late pleistocene the mis 3 ages derived from shoreline related sedimentary facies are supported by records from adjacent mega deltas and shelf sites with paleoshoreline facies proximal sites from the central indochina craton show high sea levels during late mis 3 whereas distal sites from the open continental shelf indicate much lower sea levels at the same time independent globally relevant sea level reconstructions suggest that both positions have been affected by later vertical movement this discrepancy between sea level records from central cratonic sites and the continental margin can be explained by a balanced response to locally differentiated sediment loading and compaction on the shelf as is supported by published seismic data however if the complete set of radiocarbon dates is contaminated by younger material then the second recorded sea level highstand may be associated with mis 5 as no marine deposits have yet been reported in any of the three indochinese mega deltas for this time interval

evolution of asian monsoon variability revealed by oxygen isotopic record of middle holocene massive coral in the northern south china sea a 40 year delta o 18 record of the similar to 5 4 ka bp porites lutea from the east coast of hainan island in the northern south china sea scs was analyzed to investigate evolution of asian monsoon variability during the middle holocene the mean maximum and minimum of the coral skeletal delta o 18 were 0 49 parts per thousand 0 69 parts per thousand and 0 14 parts per thousand higher than those of modern corals respectively thus the sea surface temperature sst for mean annual winter and summer at similar to 5 4 ka bp was 2 2 degrees c 3 1 degrees c and 0 6 degrees c lower and accordingly the surface salinity sss was 1 5 parts per thousand 2 parts per thousand and 1 parts per thousand higher than today the delta o 18 amplitude of the similar to 5 4 ka coral for winter summer similar to 26 higher than modern values winter similar to 23 higher and summer similar to 18 lower than that of the modern corals implied enhanced seasonality in winter but decreased seasonality in summer for sst sss and asian monsoon conditions at similar to 5 4 ka bp relative to today thus seasonal increment of coral delta o 18 mainly resulted from decrease of winter sst and increase of winter seawater delta o 18 during the middle holocene which possibly correlated with seasonal changes of insolation the similar to 5 4 ka coral delta o 18 values indicate that interannual variability of the asian monsoon was much stronger in winter summer and winter although much weaker in summer during the middle holocene relative to today spectral analysis revealed a significant variance with a period of 18 7 years and sub significant variances at interannual periods of 2 3 2 6 years which implies that enso variance and a teleconnection between the atmospheric enso and monsoonal rainfall during the middle holocene existed although they were much weaker than today the long term decrease trends of the coral delta o 18 minima mean and maxima are controlled by the long term trends of sst increase and sss and local insolation decreases from the middle holocene to the present c 2009 elsevier ltd and inqua all rights reserved

the last glacial interglacial transition lgit in the western mid latitudes of the north atlantic abrupt sea surface temperature change and sea level implications abstract high resolution reconstructions of sea surface temperature uk 37 sst coccolithophore associations and continental input total organic carbon higher plant n alkanes n alkan 1 ols in core d13882 from the shallow tagus mud patch are compared to sst records from deep sea core md03 2699 and other western iberian margin cores results reveal millennial scale climate variability over the last deglaciation in particular during the lgit in the iberian margin heinrich event 1 h1 and the younger dryas yd represent two extreme episodes of cold sea surface condition separated by a marine warm phase that coincides with the bolling allerod interval b a on the neighboring continent following the yd event an abrupt sea surface warming marks the beginning of the holocene in this region ssts recorded in core d13882 changed however faster than those at deep sea site md03 2699 and at the other available palaeoclimate sequences from the region while the sst values from most deep sea cores reflect the latitudinal gradient detected in the iberian peninsula atmospheric temperature proxies during h1 and the b a the tagus mud patch core d13882 experienced colder ssts during both events this is most certainly related to a supplementary input of cold freshwater from the continent to the tagus mud patch a hypothesis supported by the high contents of terrigenous biomarkers and total organic carbon as well as by the dominance of tetra unsaturated alkenone c37 4 observed at this site the comparison of all western iberia sst records suggests that the sst increase that characterizes the b a event in this region started 1000 yr before meltwater pulse 1a mwp 1a and reached its maximum values during or slightly after this episode of substantial sea level rise in contrast during the yd holocene transition the sharp sst rise in the tagus mud patch is synchronous with meltwater pulse 1b the decrease of continental input to the mud patch confirms a sea level rise in the region thus the synchronism between the maximum warming in the mid latitudes off the western iberian margin the adjacent landmasses and greenland indicates that mwp 1b and the associated sea level rise probably initiated in the northern hemisphere rather than in the south

an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years eleven sediment samples taken downcore and representing the past 26 kyr of deposition at manop site c 0 57 2 n 138 57 3 w were analyzed for lipid biomarker composition biomarkers of both terrestrial and marine sources of organic carbon were identified in general concentration profiles for these biomarkers and for total organic carbon toc displayed three common stratigraphic features in the time series 1 a maximum within the surface sediment mixed layer 4 ka 2 a broad minimum extending throughout the interglacial deposit and 3 a deep pronounced maximum within the glacial deposit using the biomarker records a simple binary mixing model is described that assesses the proportion of terrestrial to marine toc in these sediments best estimates from this model suggest that 20 of the toc is land derived introduced by long range eolian transport and the remainder is derived from marine productivity the direct correlation between the records for terrestrial and marine toc with depth in this core fits an interpretation that primary productivity at site c has been controlled by wind driven upwelling at least over the last glacial interglacial cycle the biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr b p diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr

contrast in surface water δ18o distributions between the last glacial maximum and the holocene in the southern south china sea abstract published core data of planktonic foraminiferal 18o and alkenone sea surface temperature sst are used to investigate seawater 18o w distributions in the south china sea scs during the last glacial maximum lgm and the holocene the holocene w distributions show a pattern correlated to modern salinity distributions displaying an increasing trend from the south to the north however the lgm w distributions show a different pattern displaying increasing values from the central to the southern scs and the lgm holocene differences in w w corrected by ice volume effect though negative in values display decreasing amplitude toward the south both of which could suggest increasing salinity toward the south by conventional approach this is somewhat counter intuitive because enhanced freshening could be expected for the southern scs due to extra discharge from the river systems on the emerged sunda land during the lgm here we propose an alternative explanation to reconcile the lgm w and w distributions with the above expectation in the proposal changes in w salinity relationship i e lowering the w salinity slope due to significant runoff contributions to freshwater input and less 18o depleted precipitation during the lgm are deeply discussed to reasonably explain the abnormity in lgm w distributions

no aridity in sunda land during the last glaciation evidence from molecular isotopic stratigraphy of long chain n alkanes molecular distribution and stable carbon isotopic composition n 13 c of n alkanes determined in a sediment core 17962 from the southern south china sea scs show that no obvious change has taken place in vegetation on sunda land from the last glacial period to the beginning of the holocene a shift in the accumulation rate of longchain n alkanes c27 to c33 was recorded at a depth of about 620 cm probably indicative of precipitation enhancement related to winter monsoon the n 13 c values are within the range of 333 7 to 327 1x for c29 n alkanes and 333 9 to 328 4 for c31 n alkanes in the whole core sequence such an isotopic composition is characteristic of n alkanes biosynthesized mainly by plants utilizing the c3 photosynthetic pathway continuous development of c3 plants on sunda land and its surroundings evidences that the climate during the last glacial period in the southern scs was not drier than what it is today 2003 elsevier b v all rights reserved

impact of the east asian monsoon rainfall changes on the erosion of the mekong river basin over the past 25 000 yr abstract paleohydrological changes in the southern south china sea scs combined with clay mineralogy have been investigated along core md01 2393 recovered off the mekong river mouth in order to assess the impact of sea level and east asian monsoon rainfall intensity on erosion and weathering during the last 25 000 yr ssts and 18 o values determined on globigerinoides ruber were used to estimate past changes of local seawater oxygen isotope 18 o w the close position of the studied core to the mekong river mouth at sea level lowstand likely played a role in the 18 o w fluctuations resulting from changes of the monsoon rainfall and runoff into the mekong river basin the smectite illite chlorite and kaolinite illite chlorite ratios combined with the illite chemistry index during the holocene show higher chemical weathering of detrital material originating mainly from the lower reach of the mekong river at shorter time scales periods of strong monsoon rainfall are associated with an intensification of erosion of the mekong river lowland favoured by the development of incised valley systems inducing higher inputs of detrital material from the lower relative to the upper reach of the mekong river our findings imply a rapid response of erosion processes of the mekong river basin to the monsoon rainfall intensity changes

rapid grain size analyses of clay and silt fraction by sedigraph 5000d comparison with coulter counter and atterberg methods research method paper

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

the late pleistocene history of surface water δ13c in the sulu sea possible relationship to pacific deepwater δ13c changes a reconstruction of late pleistocene surface water carbon isotopic 13c variability is presented from ocean drilling program odp site 769 in the sulu sea in the western tropical pacific the sulu sea is a shallowly silled back arc basin with a maximum sill depth of 420 m site 769 was drilled on a bathymetric high in 3643 m of water and has average late pleistocene sedimentation rates of 8 5 cm kyr the oxygen isotope record 18o of globigerinoides ruber at site 769 shows a strong correlation with the specmap stacked 18o record attesting to the continuity of sediment archive at the site surface 13c displays consistent glacial interglacial variability which averages 0 9 and has varied from 0 75 to 1 1 over the last 800 kyr comparison to surface water 13c records in the south china sea and western tropical pacific suggests that the glacial interglacial surface 13c variability is regional in scale planktonic 13c data from odp site 677 in the eastern pacific is also coherent with the site 769 additionally we have found that the site 769 surface 13c record is coherent at periods of 100 and 41 kyr with deepwater 13c records from the pacific the highest correlation occurs with the deep eastern pacific where benthic 13c data from cores rc13 110 and odp site 677 closely match the sulu sea surface water record we evaluate several possible controls of surface water 13c in the sulu sea that may explain the coherent timing with pacific deepwater 13c records these include variations in terrestrial organic matter flux to the basin the upwelling of subsurface water and productivity changes and the influx of western pacific intermediate water to the sulu sea our preferred explanation involves a region of upper intermediate water upwelling in the far western pacific which has been shown to outgas co2 from subsurface waters into surface waters upwelling also occurs in the area of panama basin site 677 these equatorial upwelling zones could potentially provide a route by which pacific intermediate water can modulate the 13c composition of certain pacific surface water locations future reconstructions of late pleistocene surface water 13c variability in the western pacific and indonesian seas will be required to further evaluate the source of the glacial interglacial surface water 13c change

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

marine and terrestrial biomarker records for the last 35 000 years at odp site 658c off nw africa several high resolution proxy environmental records have been obtained for the last 35 kyr from odp hole 658c a well studied site ca 200 km oa cap blanc nw africa the collective assessment based on the marine proxies u k 0 37 sst contents of toc and chlorins upwelling radiolarian index and the percentage of florisphaera profunda surprisingly indicates that the last glacial maximum lgm was characterized by warmer sea surface temperature sst weaker upwelling and lower marine productivity compared with the preceding older glacial and subsequent deglaciation periods of the terrigenous proxies the mean grain size of the non carbonate fraction and the terrigenous alkane content indicate that wind strength and aridity were high the weaker upwelling at the 658 site during the lgm may have resulted from changes in the strength and direction of the wind systems and or shifts in the position and geometry of the upwelling cell 2000 elsevier science ltd all rights reserved

depositional sequences on a late pleistocene holocene tropical siliciclastic shelf sunda shelf southeast asia this study describes and reviews the stratigraphic architecture of the world s largest but least known tropical siliciclastic shelf using the sequence stratigraphic concept the sunda shelf provides conditions particularly suited for reconstructing its depositional history due to a low gradient and extreme width the presence of huge paleo valley systems and abundant filled channels tectonic stability during the quaternary and high sediment input due to a large catchment area we investigated the subsurface along the most prominent paleo valley by shallow seismic surveying and 36 gravity cores controlled by 80 radiocarbon dates the deposits during sea level fall prior to the last glacial maximum lowstand and the subsequent deglacial rise correspond to four systems tracts a wide partly detached prograding deltaic clinoforms indicate forced regression related to a regressive systems tract b sparse shoreline deposits and widespread soil formation refer to a lowstand systems tract c rapidly backstepping coastline related deposits form a confined transgressive systems tract without stacking patterns and are mainly restricted to the paleo valley system d a thin marine mud cover extends as a condensed section over the whole shelf area the base of a highstand systems tract the stratigraphic architecture on the central sunda shelf strata over the past 50 000 years is the result of the interplay of three major factors 1 rapid sea level changes 2 locally pronounced physiography and 3 changes in sediment supply that determined the distribution and accumulation pattern c 2003 elsevier ltd all rights reserved

lacustrine deposits in the paleocene fort union formation northern bighorn basin montana abstract the fort union formation of the northern bighorn basin is a complex sequence of interbedded fluvial lacustrine and palustrine deposits a probable lacustrine facies is well developed near the center of the basin these tiffanian age sediments here designated the belfry member consist of thin laterally persistent beds of fine grained lenticular and tabular sandstones shale and mudstones lignite and argillaceous or fossiliferous limestone in general their lithologic characteristics particularly the abundance of sandstones are very different from those normally associated with lacustrine sequences and may be misinterpreted as fluvial deposits two sections cody road and silvertip were examined in detail sandstones are generally carbonate cemented phyllarenites compositional differences exist between the two sections with silvertip having better textural maturity and more chert most limestones are argillaceous micrites but biomicrudites are found in the upper silvertip section mudstones and shales contain smectite interstratified smectite vermiculite kaolinire illite and chlorite separable into 4 major assemblages these alternate irregularly throughout the sections but assemblages without an expandable clay occur only in the upper part of silvertip the belfry lakes were apparently shallow and of limited areal extent with fluctuating water levels and low energy muddy shorelines clastic input from the rising beartooth and bighorn mountains was high but composition of carbonates and clays suggests that the lake waters were alkaline slightly saline with generally sluggish circulation and mildly reducing bottom conditions

terrigenous n alkane input in the south china sea high resolution records and surface sediments abstract molecular abundances of n nonacosane are reported for a suite of 44 surface sediments and four deep sea cores distributed throughout the south china sea scs covering the last 220 ky at different time resolutions the patterns of glacial to interglacial variability of the concentrations of this terrigenous marker are parallel for all cores taking values linearly inversely correlated to the u37k index sea surface temperatures sst with high concentrations during cold glacial intervals and low concentrations during warm interglacial periods the oscillations of this terrigenous marker likely result from the emergence and flooding of the shelves caused by sea level variations which together with scs ssts have a clear dependency on the northern hemisphere climate evolution calculation of accumulation rates for the northernmost core together with the modern distribution of n nonacosane concentrations in surface sediments evidences the complexity of sedimentation patterns in the northern scs in particular and in agreement with recent studies terrigenous materials deposited there might originate from areas different than the highly loaded pearl river for paleoceanographic purposes the noticeable general pattern of the n alkane concentration down core profiles for the four cores studied a parameter apparently unaffected by changes in sedimentation rates prompts its use as a tracer of variations in terrigenous input into this basin over glacial to interglacial times

comparative molecular biomarker assessment of phytoplankton paleoproductivity for the last 160 kyr off cap blanc nw africa abstract we report high resolution molecular abundance data for alkenones dinosterol long chain diols and n alkanols from odp site 658 20 45 n 18 35 w 2263 m water depth these data are compared with previously reported data for toc chlorins opal and long chain n alkanes the contents and mass accumulation rates mars of chlorins are used as total phytoplankton productivity proxies while the contents and mars of opal dinosterol alkenones and diols are used as productivity proxies for diatoms dinoflagellates haptophytes and eustigmatophytes diatoms respectively five high productivity intervals hpis are identified two at the glacial interglacial transition boundaries of 132 122 and 15 8 ka two within the warmer periods of mis 3 50 30 ka and the late holocene 4 0 ka and one within the glacial period of mis 4 67 60 ka productivity was lowest during both the penultimate glacial maximum of mis 6 150 140 ka and the last glacial maximum 22 18 ka as revealed by both the total phytoplankton and individual phytoplankton productivity indicators phytoplankton community structure changed significantly over the last 160 kyr the termination i ii hpis were characterized by higher opal content possibly reflecting increased diatom contributions to total productivity eustigmatophyte diatom and haptophyte contributions were higher during mis 5 but decreased toward the holocene dinosterol revealed an opposite trend with the highest contribution in the holocene we ascribe such changes in phytoplankton communities to the effects brought about by the varying amounts and nature of nutrient inputs contributed regionally by eolian dusts river influxes ocean currents and upwelling water masses

terrigenous supplies variability over the past 22 000 yr in the southern south china sea slope relation to sea level and monsoon rainfall changes changing weathering intensity sediment transport and provenance variations over the past 22 0 lea bp have been investigated by high resolution clay mineralogy grain size and stable oxygen isotopes of planktonic foraminifera records along core cg2 recovered from the continental slope of the sunda shelf southern south china sea our results indicated that the reworking of older sediments outcropping on the sunda shelf exerted a great influence on the sediment supply during the last glacial and most of the last deglacial modulated by sea level and monsoon rainfall changes during the last 9 01 a bp relative increased kaolinite and heavier delta o 18 seawater values might reflect the higher influence of the tropical indonesian islands sources due to the reopen of southern straits implying the formation of modern oceanic circulation and depositional patterns high sediment fluxes in core cg2 during heinrich stadial 1 might be a synthetic result of the intensified monsoon rainfall originated from the southward shift of the intertropical convergence zone and the proximal location of the study core before the flooding of the sunda shelf fluctuations in smectite illite chlorite ratios correlated well with monsoon intensity and periods of strong monsoon rainfall lighter delta o 18 seawater values were associated with an intensification of erosion of pre existing more weathered materials on the sunda shelf finally we concluded that sediment composition and mineralogy in the southern south china sea slope were controlled by varying degrees of reworking on the sunda shelf as well as climatically modulated sediment supply from the mekong river and southern tropical islands over the last 22 0 ka bp c 2015 elsevier ltd all rights reserved

small changes in the sea surface temperature during the last 20 000 years molecular evidence from the western tropical pacific one of the most controversial problems of glacial paleoclimatology is the conservative change in tropical sea surface temperature sst in contrast with the large high altitude temperature change in the western tropical pacific in this report sst was estimated for the last 20 000 years using alkenones preserved in marine sediments recovered from a site 800 km north of new guinea the uk37 unsaturation degree of long chain alkenones synthesized by planktonic prymnesiophyte algae record suggests that sst decreased at most 1 5 c at the last glacial maximum this small changes in sst of the western tropical pacific is concordant with results previously reported in uk37 studies from the eastern equatorial pacific and the equatorial atlantic the uk37 based sst estimates are in good agreement with the climap results and planktonic foraminifera 18o but much smaller than those ca 5 c obtained from coral sr ca and 18o thermometries and glacial vegetation reconstruction

development and carbon sequestration of tropical peat domes in south east asia links to post glacial sea level changes and holocene climate variability abstract tropical peatlands of se asia represent a significant terrestrial carbon reservoir of an estimated 65 gt c in this paper we present a comprehensive data synthesis of radiocarbon dated peat profiles and 31 basal dates of ombrogenous peat domes from the lowlands of peninsular malaysia sumatra and borneo and integrate our peatland data with records of past sea level and climate change in the region based on their developmental features three peat dome regions were distinguished inland central kalimantan borneo kutai basin borneo and coastal areas across the entire region with the onset of the holocene the first peat domes developed in central kalimantan as a response to rapid post glacial sea level rise over the sunda shelf and intensification of the asian monsoon peat accumulation rates in central kalimantan strongly declined after 8500 cal bp in close relation to the lowering rate of the sea level rise and possibly influenced by the regional impact of the 8 2 ka event peat growth in central kalimantan apparently ceased during the late holocene in association with amplified el nino activity as exemplified by several truncated peat profiles peat domes from the kutai basin are all younger than 8300 cal bp peat formation and rates of peat accumulation were driven by accretion rates of the mahakam river and seemingly independent of climate most coastal peat domes the largest expanse of se asian peatlands initiated between 7000 and 4000 cal bp as a consequence of a holocene maximum in regional rainfall and the stabilisation and subsequent regression of the sea level these boundary conditions induced the highest rates of peat accumulation of coastal peat domes the late holocene sea level regression led to extensive new land availability that allowed for continued coastal peat dome formation until the present the time weighted mean holocene peat accumulation rate is 0 54 mm yr 1 for central kalimantan 1 89 mm yr 1 for kutai and 1 77 mm yr 1 for coastal domes of sumatra and borneo the mean holocene carbon sequestration rates amount to 31 3 g c m 2 yr 1 for central kalimantan and 77 0 g c m 2 yr 1 for coastal sites which makes coastal peat domes of south east asia the spatially most efficient terrestrial ecosystem in terms of long term carbon sequestration

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

a millennial scale u37k sea surface temperature record from the south china sea 8 n over the last 150 kyr monsoon and sea level influence we report 150 kyr records of u37 sea surface temperature sst and carbonate content with 150 200 year sampling resolution from the southern south china sea scs in the northern margin of the western pacific warm pool wpwp using images core md972151 the glacial interglacial sst change is about 5 c for termination ii 23 5 to 28 5 c and 4 c for termination i 24 to 28 c the simultaneous rise of sea level and u37 sst during termination i suggests that sea level change has played an important role in the scs sst variability by influencing the exchange of tropical ocean warm surface water with the scs through the sunda shelf region sill depth 30 50 m when sea level drop was less than 30 m relative to today s md972151 sst was constantly above 27 c a situation which occurred during mis 5e part of mis5c and 5a and over the last 11 kyr sea level change was also the main control on carbonate content in the scs this was lower during low sea level stands due to the dilution effect of enhanced terrigenous inputs within the limitations of our age model millennial scale sst oscillations 1 5 c over a few hundred years occurred frequently during the entire glacial period correlating reasonably well with the hulu monsoon record from eastern china and the dansgaard oeschger d o cycles recorded for high latitude regions in the northern hemisphere such correlations suggest a possible teleconnection between higher latitude atmospheric forcing and low latitude climate oscillations in the western pacific tropical region via the asian monsoon system carbonate content also reveals millennial scale oscillations during the glacial period with higher content correlated with higher sst millennial scale fluctuations of sst and carbonate contents at this low latitude scs provide additional evidence that high frequency climate changes are global phenomena

paleo sea surface salinities in the low latitude atlantic the δ18o record of globigerinoides ruber white on the basis of the comparison of 18o values of globigerinoides ruber white 18og ruber from modern sediments and measured sea surface temperatures sst and salinity sss 18og ruber values most clearly record summer sst and sss of the uppermost 50 m of water in the low latitude atlantic a new transfer equation is presented for estimating local summer paleo sss at 0 50 m depth using 18og ruber paleo sst and the global 18o ice effect of sea water with the standard error reaching 0 72 0 77 sss the equation was applied to a 35 kyr long 18og ruber record and paleo sst estimates based on planktonic foraminiferal assemblages to reconstruct the paleo sss changes along the east atlantic margin off the northwest sahara the resulting local sss show a general increase by 0 3 1 4 during the last glacial maximum lgm and large parts of glacial termination i suggesting a general increase in the upwelling of the highly saline north atlantic central water and or a reduced lateral advection of less saline canary current water two short salinity lows up to 0 35 less than today during and after the lgm are coeval with the heinrich meltwater events 1 and 2 in the north atlantic indicating the breakdown of coastal upwelling and meltwater advection from the north both events are followed by an extreme sss maximum 38 15 along with the restoration of the salinity conveyor belt at 9 0 5 5 ka the salinity minimum up to 0 65 less than today reflects the continental runoff linked to the phase of strong north saharan humidity during the early holocene climatic optimum

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

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

southwestward weakening of wyoming lithosphere during the laramide orogeny the mechanism of laramide deformation in the central rocky mountains remains enigmatic it is generally agreed that the deformation resulted from low angle subduction of the farallon plate beneath the north american plate during the latest cretaceous early eocene however recent studies have suggested the importance of slab removal or slab rollback in causing this deformation here we infer wyoming lithosphere structure and surface deformation pattern by conducting 2 d flexural subsidence modeling in order to provide constraints on the mechanism of laramide deformation we assume that wyoming lithosphere behaved as an infinite elastic plate subject to tectonic loading of mountain ranges and conduct 2 d flexural subsidence modeling to major laramide basins to document lithospheric stiffness and mountain load height our results show that the stiffness of wyoming lithosphere varied slightly in each basin during the 30 myr duration of the laramide deformation and decreased from northeastern wyoming te 32 46 km to southwestern wyoming te 6 9 km our results also imply that the increase of equivalent load height of major laramide ranges accelerated during the early eocene we propose that the bending stresses induced by the topographic load of the sevier fold and thrust belt combined with crust mantle decoupling initiated by the overthickened sevier hinterland and the end loads due to the low angle subduction at the western edge of the thick wyoming craton have caused the southwestward decrease of lithospheric stiffness in wyoming moreover we attribute the accelerated load height gain during the early eocene to both dynamic and isostatic effects associated with slab rollback

biological markers and their carbon isotopes as an approach to the paleoenvironmental reconstruction of nansha area south china sea during the last 30 ka paleoenvironmental changes over the last 30 ka have been documented for the nansha area south china sea from the biomarkers and their carbon isotopic composition of 314 sediment samples from core 17962 the concentrations of marine lipids indicate that the paleoceanographic and paleoclimatic conditions were not stable in the nansha area during the last glacial period the accumulation rates of c37 alkenones and c30 alkyl diols show that marine paleoproductivity was higher during the last glaciation than in the holocene and correlate well with those of terrestrial biomarkers simultaneous variations in accumulation rates of marine biomarkers and terrigenous long chain compounds during the last glacial period suggest that this enhancement of marine productivity was caused by an increase in terrestrial nutrient supply from the sunda shelf the stable carbon isotopic composition of terrigenous long chain compounds such as n alkanes 13 c 28 6 34 2 n alkanoic acids 13 c 27 1 31 8 and n alkanols 13 c 26 6 35 3 indicates that these compounds were derived from c3 plants and the surrounding area of southern south china sea was not dry during the last glacial 2002 elsevier science ltd all rights reserved

development of potential acid sulfate paleosols in paleocene floodplains bighorn basin wyoming usa abstract floodplain paleosols in the paleocene fort union formation in the bighorn basin are distinguished by a dark claystone interval with yellow jarosite mottles relatively high total organic carbon values and woody debris and leaves along bedding planes the paleosols also have various redoximorphic features including low matrix chromas grey root mottles and local concentrations of goethite and hematite especially associated with roots and other organic matter jarosite is usually an oxidation product of pyrite which forms under waterlogged conditions when sulfate and organic matter are available the former presence of pyrite and the redoximorphic features suggest that the fort union paleosols first developed as potential acid sulfate soils brinkman and pons 1973 the dark claystones with jarosite are interpreted as permanently reduced or gr horizons the gr horizon is overlain by mudstone that is lighter colored and lacks jarosite this represents an ancient bg horizon or a bg sequence the jarosite indicates that the paleosols underwent a subsequent episode of oxidation and acidification those processes require that the soils be drained which probably did not occur during paleocene time and may be a recent event rather the soils were probably buried as the fort union formation continued to aggrade and the waterlogged soils were pushed even farther below the groundwater table only with late cenozoic excavation of strata in the basin and exposure of the fort union deposits did jarosite precipitate pedogenic and paleobotanical features suggest that the soils formed in floodplain swamps dominated by coniferous trees the high organic content and clay rich nature of the gr horizons suggest that the floodplain swamps were not close to the active channel the bipartite nature to the profiles bg horizon or a bg sequence above a gr horizon probably resulted from two different kinds of floodplain deposition grain size trends indicate that the gr horizons formed on sediment deposited by overbank flooding the impermeable fine grained sediment and its low topographic position led to waterlogging the overlying a bg or bg horizons formed on coarser sediment that was probably deposited during channel avulsion the greater permeability and higher topographic position of this sediment caused it to be better drained than the gr horizon the paleosols are unusual because they formed in a freshwater setting whereas modern potential acid sulfate or acid sulfate soils form in coastal areas where sulfate is readily available the source of the sulfate may have been cretaceous marine shales exposed along the flanks of mountains rising around the bighorn basin during paleocene time other upper cretaceous and paleocene formations in the rocky mountain area contain similar rocks suggesting that sulfidic soils were relatively common in the mid continent at this time most of these other examples probably reflect deposition associated with the retreating western interior seaway and humid climates

low latitude hydro climatic changes during the plio pleistocene evidence from high resolution alkane records in the southern south china sea abstract high resolution records of long chain n alkane biomarkers from the southern south china sea reveal tightly response of n alkane distribution to hydro climate changes over the past 5 ma with increasing longer chain n c31 alkanes indicating a correlation with drier conditions and increasing shorter chain n c27 alkanes with wetter conditions the variations of the c31 c27 ratio or the alkane chain length index imply humid conditions before 2 9 ma progressively reduced moisture since then and to bigger fluctuations between wet and dry conditions since 1 2 ma this long term hydro climate trend is superimposed by glacial dry and interglacial wet patterns over the plio pleistocene glacial cycles combined with other proxy records our results indicate that precipitation over the tropical asia pacific strengthened before the onset of the northern hemisphere glaciation and the mid pleistocene climate transition at about 1 2 ma these dramatic humidity changes over major climate transitions imply a crucial role of tropical hydrology dynamics on global climate change in the late cenozoic

sedimentary characteristics of thick layer lacustrine beach bars in the cenozoic banqiao sag of the bohai bay basin east china abstract lacustrine beach bar reservoirs have become important exploration targets in the bohai bay basin in china especially in the banqiao sag within the huanghua depression where some typical thick layer beach bar reservoirs have been discovered recently the average single layer thickness of the beach bar sand bodies in the second member of the paleogene shahejie formation within the sag is greater than 10 m and the cumulative thickness of these sands reach up to 100 m the second member of the shahejie formation in the banqiao sag consists of a third order sequence of three systems tracts a lowstand systems tract a transgressive systems tract and a highstand systems tract beach bar sand bodies were deposited widely in the sag in the lowstand systems tract but were less deposited in the other systems tracts the sedimentary characteristics distribution patterns and formation mechanisms of the beach bar sand bodies in the lowstand systems tract of the second member of the shahejie formation were systemically studied using cores wireline logs and 3d seismic data the beach bar was divided into five sedimentary microfacies namely sandy bar centre sandy bar flank interbar deposit coastal beach and infralittoral beach based on the integrated analysis of the paleostructure and sedimentary environment it was inferred that the thick layer beach bars in this area resulted from the combination and joint control of the sediment source system hydrodynamic environment lake level variations and contemporaneous fault activity firstly the sands in the braided river delta of the beidagang buried hill structural belt served as the provenance that provided the material basis for the beach bars in the banqiao sag secondly the wave effects in the gentle slope belt controlled the scale and distribution of the beach bars under the control of waves various sedimentary microfacies were regularly distributed in particular the continuous activity of the contemporaneous dazhangtuo fault contributed to the formation of the thick layer beach bars in the banqiao sag the contemporaneous fault controlled the allocation of the sediments providing abundant sands in the downthrown side of the fault in addition there was a constant high energy hydrodynamic environment near the fault plane where the sand bodies experienced long term reworking by waves and gradually formed beach bars with large thickness the activity of the contemporaneous fault increased the accommodation space in the lowstand systems tract of the second member of the shahejie formation which resulted in continuous sand deposition and provided the necessary conditions for forming the thick layer beach bars

ranging performance of satellite laser altimeters topographic mapping of the earth moon and planets can be accomplished with high resolution and accuracy using satellite laser altimeters these systems employ nanosecond laser pulses and microradian beam divergences to achieve submetre vertical range resolution from orbital altitudes of several hundred kilometres in this paper the authors develop detailed expressions for the range and pulsewidth measurement accuracies and use the results to evaluate the ranging performances of several satellite laser altimeters currently under development by nasa for launch during the next decade the analysis includes the effects of the target surface characteristics spacecraft pointing jitter and waveform digitizer characteristics the results show that ranging accuracy is critically dependent on the pointing accuracy and stability of the altimeter especially over high relief terrain where surface slopes are large at typical orbital altitudes of several hundred kilometres single shot accuracies of a few centimetres can be achieved only when the pointing jitter is on the order of 10 mu rad or less

episode of strengthened summer monsoon climate of younger dryas age on the loess plateau of central china abstract the baxie loess section just east of the tibetan plateau contains evidence showing that the asian monsoon climate experienced an abrupt reversal near the end of the last glacial age rapid deposition of dust under cool dry full glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm moist summer monsoon a subsequent abrupt increase in dust deposition a response to a weakening of the summer monsoon was later followed by renewed soil formation as summer monsoon circulation again intensified during the early holocene by one interpretation the thin upper loess is a manifestation of the european younger dryas oscillation however in this case the available 14c ages require either that 1 onset of loess deposition lagged the beginning of the younger dryas event in europe by as much as 2000 calibrated 14c years or 2 all the 14c ages are too young possibly due to contamination alternatively the late glacial paleosol the top of which is synchronous with the abrupt end of the late glacial 18o anomaly in the dye 3 greenland ice core records the younger dryas event such an interpretation is consistent with general circulation model simulations of younger dryas climate that show strong seasonality and a strengthened summer monsoon and with marine cores from the western pacific ocean that contain evidence of pronounced cooling of surface waters during younger dryas time

burial of different types of organic carbon in core 17962 from south china sea since the last glacial period abstract total organic carbon toc black carbon bc and land derived organic carbon loc extracted from marine sediment core 17962 from the southern south china sea and analyzed by pyrolysis gas chromatography elemental analyzers and mass spectroscopy can be interpreted in terms of regional land biomass burning climatic conditions vegetation cover and ocean paleoproductivity carbon from terrestrial sources including bc and loc appears to be a significant component of toc 3 1 39 3 range 16 5 average for bc 4 4 56 6 range 14 6 average for loc the production of bc and loc was only slightly higher during the last maximum glaciation lgm than during the holocene therefore dramatic changes in climate and vegetation cover do not seem to have occurred at the pleistocene holocene boundary paleoproductivity data calculated from marine organic carbon proved to be more accurate than those calculated from toc and exhibit the same pattern of temporal variation however the glacial interglacial contrast in the refined palaeoproductivity is less evident than that calculated from toc

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition

nitrogen isotope and chlorin paleoproductivity records from the northern south china sea remote vs local forcing of millennial and orbital scale variability abstract variations in nitrogen isotopic composition 15n and total chlorin accumulation rate ar are employed as proxies to reconstruct oceanic nitrate inventory the balance between denitrification and n fixation and paleoproductivity in a rapidly accumulating sediment drift deposit beneath the western pacific warm pool for the last 145 kyr subsurface and deep waters of the northern south china sea scs are sourced from the shallow kuroshio current kc and pacific intermediate water respectively their relative importance in determining sedimentary 15n and paleoproductivity have been altered by changes in equatorial circulation summer and winter monsoon intensity and relative sea level the location and basin configuration of the marginal scs renders it especially sensitive to such changes assuming complete annual nitrate utilization low 15n values during glacial stages are interpreted as a reflection of reduced remote denitrification in the eastern tropical north pacific etnp source waters while much of marine isotope stage mis 3 and the last interglacial were characterized by high denitrification however intervals of anomalously low 15n values are interpreted as reflecting the contribution from regional n fixation in west pacific surface waters transmitted to the site by the shallow kc unusually the holocene is characterized by declining 15n values and an inverse correlation with organic matter content since ca 8 2 ka millennial scale variations during mis 3 indicate higher frequency variations in both etnp denitrification and local n fixation which may be coherent with a hemispheric response to dansgaard oeschger events recorded at high latitudes for much of the last 145 kyr paleoproductivity was decoupled from 15n and instead seems to reflect the extent of the global nitrate inventory stimulated by elevated dust fertilization and regional mixed layer deepening associated with the relative intensity of the se asian winter monsoon despite evaluation of possible conflicting influences on the record of each proxy we interpret our data as clear evidence of glacial interglacial changes in marine nutrient inventory across the whole of the north pacific with a corresponding biogeochemical response and important implications for global co2 drawdown via an invigorated biological pump the relative importance of local regional and global contributions to our records appears to be strongly modulated by relative sea level controlling trans and extra basinal circulation in the scs

high resolution palynological record of holocene climatic and oceanographic changes in the northern south china sea abstract for the first time palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern south china sea scs covering the last 12 500 years both terrestrial and marine palynomorph records show strong signals of the sea level change during the studied interval the highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea level stand during the younger dryas and early holocene the increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea level rise interval from 12 500 to 6800 or 6000 cal yr bp then the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded a high abundance of impagidinium in the period 12 000 10 400 cal yr bp possibly resulted from increased input of western philippine sea waters into the scs and the branching of the kuroshio current a short term decrease of impagidinium at 11 700 11 000 cal yr bp corresponding to the mwp 1b event might be associated with input of the east china sea waters through the taiwan strait the relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water dominant transport for pollen and spore dispersal prior to 6300 cal yr bp whereas wind transport became more prominent thereafter the timing of this change corresponds to the highest sea level stand at 6800 6000 cal yr bp when the present oceanographic setting was formed the mid holocene optimum can be seen by the highest abundance of subtropical tropical broad leaved arboreal pollen and by the highest abundances of dapsilidinium pastielsii three strengthened winter monsoon intervals at 5500 cal yr bp 4000 cal yr bp and 2500 cal yr bp are reflected by increases in pinus pollen content after the present oceanographic condition formed

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

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

hydrographic variability in the northern south china sea over the past 45 000 years new insights based on temperature reconstructions by uk 37 and texh86 proxies from a marine sediment core md972146 abstract millennial scale climate variability was persistent feature for greenland ice core and north atlantic marine records during the marine isotope stage mis 3 studying high quality climatic archives outside of the greenland and north atlantic with precise constraint of absolute dating and high resolution sampling is a prerequisite to understand how the millennial scale changes well expressed in north hemisphere nh high latitudes had been propagated out to the other regions here we generated the surface and subsurface hydrography u k 37 and tex h 86 temperatures and terrestrial material input n alkanes records with precise ams 14 c dated control for the 45 ka from a core md972146 retrieved from the northern south china sea scs then we compared our records to the oxygen isotope record from a greenland ngrip ice core and the mean grain size record from a loess sequence at gulang china we found that the millennial scale oscillations of hydrolography and terrestrial material inputs records during the time since the last deglaciation and of 33 45 ka share similar patterns in timing and amplitude of the nh high latitude climate however we found that a non nh pattern of millennial scale oscillations for the late mis 3 20 33 ka of our hydrography and terrestrial material inputs records our studies imply that the changes of obliquity also may be important in determining the timing and amplitude of millennial scale east asian monsoon eam variability expressed in the northern scs hydrography and terrestrial material inputs

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

paleoceanography of the last 500 kyrs in the central okhotsk sea based on geochemistry abstract analyses of geochemical constituents organic carbon nitrogen calcium carbonate and biogenic opal on core yk07 12 pc3b core pc3b provided detailed and useful information in biological productivity and paleoceanographic changes which occurred in the central okhotsk sea during the last 500 kyrs an age model for core pc3b was established based on changes in benthic foraminiferal 18 o the trend in organic carbon oc content represented the temporal change that can be correlated with the 18 o curve in core pc3b high during the interglacial periods mis 1 5 9 11 and 13 the trend in caco 3 content represented is similar to the trend seen in the oc content the high correlation between oc and caco 3 contents indicates an increase in coccolithophorid productivity during the early deglaciations the comparison between the changes in caco 3 and biogenic opal indicates that the dominant phytoplankton group was coccolithophorids during the early deglaciations which was subsequently replaced by diatoms during the late deglaciations it appears that such a temporal phytoplankton succession was caused by an increase in dissolved silicon supply to the euphotic layer possibly associated with a change in surface hydrography that subsequently caused an upward expansion of the intermediate layer such ecological changes probably played an important role in the uptake of atmospheric co 2

deepwater circulation variation in the south china sea since the last glacial maximum deepwater circulation plays a central role in global climate compared with the atlantic the pacific deepwater circulation s history remains unclear the luzon overflow a branch of the north pacific deep water determines the ventilation rate of the south china sea scs basin sedimentary magnetic properties in the scs reflect millennial scale fluctuations in deep current intensity and orientation the data suggest a slightly stronger current at the last glacial maximum compared to the holocene but the most striking increase in deep current occurred during heinrich stadial 1 h1 and to a lesser extent during the younger dryas yd results of a transient deglacial experiment suggest that the northeastern current strengthening at the entrance of the scs during h1 and the yd times of weak north atlantic deep water formation could be linked to enhanced formation of north pacific deep water

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

the flooding of sundaland during the last deglaciation imprints in hemipelagic sediments from the southern south china sea abstract during the last 30 ka the south china sea scs experienced pronounced palaeogeographic changes associated with the postglacial sea level rise which significantly modified the hydrography of this marginal sea the most crucial effects in the southern part of the basin were the submergence of sundaland and the opening of the southern channels connecting the scs to the tropical indo pacific isotopic sedimentological and organic geochemical parameters determined in two sediment cores from the southern scs one in the open sea and the other close to the continental shelf sites 17961 and 17964 respectively show that the main hydrographical changes during this period were related to critical thresholds in sea level rise the main changes occurred at about 15 13 5 ky bp coincident with meltwater pulse mwp ia when sea surface temperatures ssts at both sites experienced a rapid 1 5 c rise and the clay content and n nonacosane concentrations dropped significantly both trends reflect a rapid retreat of the coastline and an initial flooding of sundaland at that time a second important change starting with the beginning of mwp ib at about 11 5 ky bp and culminating at 10 ky bp involved the establishment of modern hydrographic conditions this is evident from the rapid convergence of the foraminiferal oxygen isotope records and the establishment of holocene sst values these results highlight the need to include the flooding emergence of sundaland as an important boundary condition in future modelling studies of asian palaeomonsoons

formation and fate of sedimentary depocentres on southeast asia s sunda shelf over the past sea level cycle and biogeographic implications abstract sea level variations are the major factor controlling sedimentation as well as the biogeographic patterns at continental margins over late quaternary times fluctuations on millennial time scales produce locally complex deposits in coasts and on shelves associated with short term influence on species development this article reviews the sedimentary and biogeographic history of the tropical siliciclastic sunda shelf as an end member of continental shelves regarding extreme width an enormous sediment supply and highest biodiversity in response to rapid sea level fluctuations we describe particular depositional segments as part of a genetic succession of zones from land to the deep sea based on literature data field observations and calculation of hydro isostatic adjustment effects on changing relative sea level these segments are characterized by individual sedimentary processes and deposits and by a specific potential for material storage and re mobilization long term regressive intervals led to overall sigmoidal promoting extremely thick and wide succeeding units in contrast rapid lateral shifts of defined depocentres over long distances took place in response to short term sea level fluctuations fully isolated small scale sediment bodies formed when sea level changed at exceptionally high rates as a result of the high availability of organic rich sediments mangrove and freshwater peats formed frequently over late quaternary times the appearance of thick massive and widespread peats is mainly linked to time intervals of a sea level rise at slow rates whilst organic matter appears much more dispersely in the sediments during episodes of rapidly changing sea level the preservation potential of the regressive units is generally high due to highest initial sediment supply stabilizing soil formation during exposure and rapid subsidence preservation of depositional elements from other periods is more exceptional and either restricted to local morphological depressions or to episodes of rapid sea level change besides complex channel incision an overall lowering of the sediment surface related to erosion as deep as 20 m or more over wide areas took place mainly during sea level lowering the final export of shelf material is documented by enormous mass wasting packages on the associated continental slope from a palaeogeographic perspective the rapid formation or disappearance of special habitat zones such as mangrove fringes and extended mud flats led to species establishment or truncation in distribution in addition the opening or closure of ocean passages as narrow bridges allowing limited species crossing or as fully colonized corridors had severe impact on eco fragmentation and the expansion or contraction of species independent of such particular conditions sea level changes have been too rapid over the past climatic cycle to allow full regeneration and mature development of coast related ecosystems

millennial scale dynamics of the east asian winter monsoon during the last 200 000 years the primary productivity dynamics of the last 200 000 years in the sulu sea was reconstructed using the abundance of the coccolithophore florisphaera profunda in the images md97 2141 core we find that primary productivity was enhanced during glacial periods which we suggest is due to a stronger east asian winter monsoon during the last 80 kyr eight significant increases in primary productivity pp in the sulu sea are similar to east asian winter monsoon changes recorded in chinese loess the pp maxima are not linked with heinrich events he in the north atlantic although four pp peaks are synchronous with he the pp oscillations have frequencies near those of the dansgaard oeschger cycles in northern hemisphere ice records and indicate a teleconnection of the east asian winter monsoon with greenland climate in this sulu sea record the east asian winter monsoon oscillates with periodicities of6 4 2 3 4 2 3 and 1 5 kyr in particular the 1 5 kyr cycle exhibits a strong and pervasive signal from stage 6 to the holocene without any ice volume modulation this stationarity suggests that the 1 5 kyr cycle is not driven by some high latitude forcing

the age and origin of the younger dryas climate event in greenland ice cores 230th 234u and 14c dating of barbados corals has extended the calibration of 14c years b p to calendar years b p beyond the 9200 year tree ring series bard et al 1990 this now permits the conversion of 14c chronozones which delimit major climate shifts in western europe to calendar years the younger dryas chronozone defined as 11 000 to 10 000 14c years b p corresponds to 13 000 to 11 700 calendar years b p this calibration affects the interpretation of an intensely studied example of the younger dryas climate event the 18o anomaly between 1785 and 1793 m in dye 3 ice core the end of the 18o anomaly in dye 3 ice core has been dated by measurements of 14c in air bubbles andree et al 1984 1986 and by annual layer counting hammer et al 1986 the older 14c dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the barbados 230th 234u calibration the 14ccorrected age for the end of the 18o event is 10 300 400 calendar years b p compared to the annual layer counting age of 10 720 150 years b p thus the younger dryas event in the dye 3 ice core ends in the preboreal chronozone 11 700 to 10 000 calendar years b p and is not correlative with the end of the younger dryas event identified in pollen records marking european vegetation changes the end of the dye 3 18o event is however correlative with the end of meltwater pulse ib fairbanks 1989 marking a period of intense deglaciation with meltwater discharge rates exceeding 13 000 km yr

investigating the history of east asian monsoon and climate during the last glacial interglacial period 0 140 000 years mineralogy and geochemistry of odp sites 1143 and 1144 south china sea abstract monsoon climate is an important component of the global climatic system a comprehensive understanding of its variability over glacial interglacial time scales as well as of its effects on the continent and in the ocean is required to decipher links between climate continental weathering and productivity a detailed multiproxy study including bulk and clay mineralogy grain size analysis phosphorus geochemistry sedex extraction organic matter characterization and nitrogen stable isotopes was carried out on samples from odp sites 1143 and 1144 leg 184 south china sea covering the past 140 000 years we tentatively reconstruct the complex sedimentation and climatic history of the region during the last glacial interglacial cycle when sea level variations linked to the growth and melting of ice caps interact with monsoon variability during interglacial periods of high sea level summer monsoon was strong and humid and warm climate characterized the adjacent continent and islands clay minerals bear signals of chemical weathering during these intervals high calcite and reactive phosphorus mass accumulation rates mars indicate high productivity especially in the southern region of the basin during glacial intervals strong winter monsoon provided enhanced detrital input from the continent as indicated by high detrital mar glacial low sea level resulted in erosion of sediments from the exposed sunda shelf to the south and clay mineral variations indicate that warm and humid conditions still prevailed in the southern tropical areas enhanced supply of nutrients from the continent both by river and eolian input maintained high primary productivity reduced circulation during these periods possibly induced active remobilization of nutrients such as phosphorus from the sediments intense and short cold periods recorded during glacial and interglacial stages correlate with loess records in china and marine climatic records in the north atlantic confirming a teleconnection between low and high latitude climate variability

millennial scale alkenone sea surface temperature changes in the northern south china sea during the past 45 000 years md972146 abstract millennial scale climate changes are well expressed in greenland ice core and north atlantic marine records the timing and the amplitude of the millennial scale changes outside greenland and the north atlantic are poorly known mainly due to the lack of high quality climatic archives with precise constraints of numerical dating here we report a new high resolution ams 14 c dated alkenone sea surface temperature sst record of the last 45 000 years from a marine sediment core md972146 retrieved from the northern south china sea scs the sst record shows millennial scale oscillations during the intervals of since the last glacial maximum lgm 21 000 bp to the present and 34 45 ka that are nearly in phase with those from the northern hemisphere nh sst oscillations during 21 34 ka do not match well with the nh patterns implying that a dominance of non nh mechanisms may have governed the sst changes outside the nh high latitudes during the particular time interval the non nh climatic pattern during 21 34 ka has been only reported from a sst record from the okinawa trough sediments md012404 and a grain size record from chinese loess sequences gulang but not from the other scs records which had been investigated using lower resolution sampling and age dating

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

on the significance of sea level variations and shelf paleo morphology in governing sedimentation in the southern south china sea during the last deglaciation abstract deglacial sedimentation on the outer sunda shelf the shelf margin and slope shows a close correlation with the stages of flooding of the emerged shelf it is mainly controlled by the relationship between shelf paleo physiography and changes in sea level and sediment supply based on the sedimentological and geochemical variability at five sites along a transect across the outer shelf and the continental slope covering the last 20 000 years four intervals of significant depositional changes are identified the first reorganization in the sedimentation regime which was established during sea level lowstand is associated with the drowning of the lower course of the north sunda river between 16 5 and 14 5 ka during and following the rapid rise in sea level at 14 5 14 ka sedimentation on the slope is characterized by an accelerated decrease in the supply of terrigenous material associated with the flooding of the middle part of the paleo valley this abrupt change in sedimentation is followed by a period of gradual decrease of terrigenous supply to the slope when the surrounding plains of the river valley were flooded 14 8 5 ka the final change occurred between ca 8 5 and 6 ka when the coastline reached its modern position and modern sedimentary patterns are established this change probably marks the end of reworking by transgression given the synchroneity of sedimentological changes along the transect across the sunda shelf and into the deep sea with the environmental shifts on the central shelf sedimentation on the margin and slope appears to be mainly controlled by the interrelationship of sea level shelf paleo physiography and sediment supply moreover the records display lateral changes through time associated with stages of the deglacial transgression which mask any potential sedimentological variability due to changes in precipitation vegetation or atmospheric circulation this fact cautions the interpretation of near shore sedimentary records as unequivocal recorders of local climate change e g se asian monsoon and highlights the need to include variations in shelf physiography and sea level in future paleoceanographic studies

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

geochronology and mammalian biostratigraphy of middle and upper paleocene continental strata bighorn basin wyoming the bighorn basin of northwestern wyoming preserves one of the most complete records of middle paleocene to lower eocene continental biota the geochronology of this important interval depends partly on numerical calibration of the geomagnetic polarity time scale gpts but the middle and late paleocene parts of the gpts have been poorly constrained radioisotopically a new volcanic ash from the northern bighorn basin provides the first radioisotopic age for upper middle paleocene strata upper selandian and is an important calibration point for the base of polarity chron c26n and the selandian thanetian stage boundary in the gpts sanidine from the ash has a weighted mean age of 59 00 0 30 2 ma based on twenty three 40 ar 39 ar bulk laser fusion analyses the ash corroborates the revised age estimate for the base of chron c26n in the most recent geomagnetic polarity time scale gpts 04 and confirms that c26n is older than depicted in the 1995 gpts we place paleocene mammalian biozones in the bighorn basin into a refined geochronologic framework these biozones are the primary basis for biostratigraphic correlation of middle and upper paleocene continental deposits in north america new paleomagnetic data provide synchronous tie points for correlation among three stratigraphic sections in the northern bighorn basin and to the gpts paleomagnetic correlation study of new fossil material review of known faunas and refined stratigra phy enable us to reevaluate several biozones we define three new zones based on first occurrences of taxa the phenacolemur ti 4b probathyopsis ti 5a revised and copecion cf 3 revised zones the phenacolemur zone includes some faunas previously placed in the plesiadapis churchilli and plesiadapis fodinatus zones ti 4 and ti 5a respectively the probathyopsis zone replaces the p fodinatus zone and the copecion zone replaces the phenacodus ectocion acme zone cf 3 seven of the biozones considered here are subdivisions of the tiffanian land mammalage thetiffanianwasoriginallytypifiedbythemasonpocketfaunainsouthwest ern colorado but it is now much better known from faunas in the northern bighorn basin biostratigraphic evidence and new paleomagnetic data from the bighorn basin indicate that mason pocket is considerably older than was previously recognized and occurs in chron c26r rather than c25r the geochronologic framework presented here helps to constrain the temporal ranges of species that occur in the middle and late tiffanian and it allows the bighorn basin record to be better compared to other faunal floral and paleoclimate records both regionally and globally

north pacific and north atlantic sea surface temperature variability during the holocene holocene climate variability is investigated in the north pacific and north atlantic realms using alkenone derived sea surface temperature sst records as well as a millennial scale simulation with a coupled atmosphere ocean general circulation model aogcm the alkenone sst data indicate a temperature increase over almost the entire north pacific from 7 cal kyr bp to the present a dipole pattern with a continuous cooling in the northeastern atlantic and a warming in the eastern mediterranean sea and the northern red sea is detected in the north atlantic realm similarly sst variations are opposite in sign between the northeastern pacific and the northeastern atlantic a 2300 year long aogcm climate simulation reveals a similar sst seesaw between the northeastern pacific and the northeastern atlantic on centennial time scales our analysis of the alkenone sst data and the model results suggests fundamental inter oceanic teleconnections during the holocene

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

holocene climate variability as derived from alkenone sea surface temperature and coupled ocean atmosphere model experiments holocene climate modes are identified by the statistical analysis of reconstructed sea surface temperatures ssts from the tropical and north atlantic regions the leading mode of holocene sst variability in the tropical region indicates a rapid warming from the early to mid holocene followed by a relatively weak warming during the late holocene the dominant mode of the north atlantic region sst captures the transition from relatively warm cold conditions in the eastern north atlantic and the western mediterranean sea the northern red sea to relatively cold warm conditions in these regions from the early to late holocene this pattern of holocene sst variability resembles the signature of the arctic oscillation north atlantic oscillation ao nao the second mode of both tropical and north atlantic regions captures a warming towards the mid holocene and a subsequent cooling the dominant modes of holocene sst variability emphasize enhanced variability around 2300 and 1000 years the leading mode of the coupled tropical north atlantic holocene sst variability shows that an increase of tropical sst is accompanied by a decrease of sst in the eastern north atlantic an analogy with the instrumental period as well as the analysis of a long term integration of a coupled ocean atmosphere general circulation model suggest that the ao nao is one dominant mode of climate variability at millennial time scales

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

an evaluation of 14c age relationships between co occurring foraminifera alkenones and total organic carbon in continental margin sediments 1 radiocarbon age relationships between co occurring planktic foraminifera alkenones and total organic carbon in sediments from the continental margins of southern chile northwest africa and the south china sea were compared with published results from the namibian margin age relationships between the sediment components are site specific and relatively constant over time similar to the namibian slope where alkenones have been reported to be 1000 4500 years older than co occurring foraminifera alkenones were significantly similar to 1000 years older than co occurring foraminifera in the chilean margin sediments in contrast alkenones and foraminifera were of similar age within 2 sigma error or better in the nw african and south china sea sediments total organic matter and alkenone ages were similar off namibia age difference toc alkenones 200 700 years chile 100 450 years and nw africa 360 770 years suggesting minor contributions of preaged terrigenous material in the south china sea total organic carbon is significantly 2000 3000 years older owing to greater inputs of preaged terrigenous material age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter physical characteristics of the depositional setting such as seafloor morphology shelf width and sediment composition may control the age of co occurring sediment components in particular offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions aging of organic matter is promoted by transport age offsets are correlated with organic richness suggesting that formation of organic aggregates is a key process