provenance of sediments from mesozoic basins in western shandong implications for the evolution of the eastern north china block abstract this paper reports la icp ms u pb dates and in situ hf isotope analyses of detrital zircons from the mesozoic basins in western shandong china with the aim to constrain the depositional ages and provenances of the mesozoic strata as well as the mesozoic tectonic evolution of the eastern north china block ncb the mesozoic strata in western shandong from bottom to top include the fenghuangshan fangzi santai and wennan formations most of the analyzed zircon grains exhibit oscillatory growth zoning and have relatively high th u ratios generally 0 2 3 4 suggesting a magmatic origin zircons from the fenghuangshan formation in the zhoucun basin yield six main age populations 2489 1854 331 305 282 and 247 ma zircons from the fangzi formation in the zhoucun and mengyin basins yield eight main age populations 2494 1844 927 465 323 273 223 and 159 ma and ten main age populations 2498 1847 932 808 540 431 315 282 227 and 175 ma respectively whereas zircons from the santai formation in the zhoucun and mengyin basins yield nine main age populations 2519 1845 433 325 271 237 192 161 and 146 ma and six main age populations 2464 1845 853 277 191 and 150 ma respectively five main age populations 2558 1330 609 181 and 136 ma are detected for zircons from the wennan formation in the pingyi basin based on the youngest age together with the contact relationships among formations we propose that the fenghuangshan formation formed in the early middle triassic the fangzi formation in the middle late jurassic the santai formation after the late jurassic and the wennan formation after the early cretaceous these results together with previously published data indicate that 1 the sediments of the fenghuangshan formation were sourced from the precambrian basement and from late paleozoic to early mesozoic igneous rocks in the northern part of the ncb 2 the sediments of the fangzi and santai formations were sourced from the precambrian basement late paleozoic to early mesozoic igneous rocks in the northern part of the ncb and the sulu terrane as well as from middle late jurassic igneous rocks in the southeastern part of the ncb and 3 the wennan formation was sourced from the tongshi intrusive complex the sulu terrane and minor precambrian basement and early cretaceous igneous rocks the evolution of detrital provenance indicates that in the early middle triassic the northern part of the ncb was higher than its interior during the late triassic to early jurassic the eastern ncb was uplifted resulting in a period of non deposition and an important transition from a compressional to an extensional tectonic regime occurred during the middle late jurassic the presence of neoproterozoic and triassic detrital zircons in the fangzi formation sourced from the sulu terrane suggests that large scale sinistral strike slip movement along the tan lu fault zone did not occur after the middle jurassic ca 175 ma

wetland expansion on the continental shelf of the northern south china sea during deglacial sea level rise abstract to identify environmental causes for past changes in vegetation in subtropical east asia we present carbon isotope compositions of plant wax n alkanes and provide estimates of the c4 plant contribution across the past four glacial terminations and interglacials based on cores recovered from the northern south china sea our results show a comparable c4 plant contribution between the last glacial maximum lgm and the holocene an increase of the c4 plant contribution by 15 20 is found for terminations iv ii and i relative to subsequent interglacial peaks coeval with an expansion of cyperaceae and poaceae in contrast termination v reveals a lower c4 plant contribution than marine isotope stage mis 11c the data exhibit a long term trend with a stepwise increase of the c4 plant contribution across interglacials mis 11c 9e 7e and 1 we suggest that no substantial changes in humidity levels over glacial interglacial cycles occurred facilitating a similar c3 c4 plant ratio for the lgm and the holocene instead deglacial sea level rises caused an extensive development of floodplains and wetlands on the exposed continental shelf providing habitats for the spread of c4 sedges and grasses the progressive subsidence of chinese coastal areas and the broadening of the continental shelf over the late quaternary explains the nearly absence of c4 plant occurrence during termination v and a gradual increase of the c4 plant contribution across interglacial peaks taken together changes in coastal environments should be considered when interpreting marine based vegetation reconstructions from subtropical asia

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

deep sea records of the continental weathering and erosion response to east asian monsoon intensification since 14 ka in the south china sea we analyzed sediment from ocean drilling program odp site 1144 in the northern south china sea to examine the weathering response of se asia to the strengthening of the east asian monsoon eam since 14 ka our high resolution record highlights the decoupling between continental chemical weathering physical erosion and summer monsoon intensity mass accumulation rates ti ca k rb hematite goethite and sr 87 sr 86 show sharp excursions from 11 to 8 ka peaking at 10 ka clay minerals show a shorter lived response with a higher kaolinite illite chlorite ratio at 10 7 9 5 ka however not all proxies show a clear response to environmental changes magnetic susceptibility rises sharply between 12 and 11 ka grain size becomes finer from 14 to 10 ka and then coarsens until similar to 7 ka but is probably controlled by bottom current flow and sealevel sr and nd isotopes show that material is dominantly eroded from taiwan with a lesser flux from luzon while clay mineralogy suggests that the primary sources during the early holocene were reworked via the shelf in the taiwan strait rather than directly from taiwan erosion was enhanced during monsoon strengthening and caused reworking of chemically weathered pleistocene sediment largely from the now flooded taiwan strait which was transgressed by similar to 8 ka cutting off supply to the deep water slope none of the proxies shows an erosional response lasting until similar to 6 ka when speleothem oxygen isotope records indicate the start of monsoon weakening although more weathered sediments were deposited from 11 to 8 ka when the monsoon was strong these are reworked and represent more weathering during the last glacial maximum lgm when the summer monsoon was weaker but the shelves were exposed c 2012 elsevier b v all rights reserved

sedimentary responses to sea level rise and kuroshio current intrusion since the last glacial maximum grain size and clay mineral evidence from the northern south china sea slope abstract we analyzed the terrigenous fraction of a sediment core from the northern slope of the south china sea to better understand the depositional history of the region since the last glacial maximum lgm temporal variations in the grain size and clay mineral composition revealed a complex set of overlapping controls approximately 90 of terrigenous sediment throughout the core ranged in size from 5 5 to 8 5 with the 5 25 6 25 size class being particularly sensitive to environmental changes the proportion of this fraction decreased during deglacial indicating a reduction in the supply of coarser grains due to coastline retreat as the sea level rose toward its present position the relative proportion of clay derived from taiwan increased however the mass accumulation rate of taiwan derived clay decreased suggesting a reduction in the westward bottom current intensity in contrast the relative contribution of clay from the pearl river decreased from 40 during the lgm to 5 when the sea level reached 70 m below its present position the pearl river contribution has remained consistently low throughout the holocene indicating that shore parallel circulation patterns on the shelf resembled their present configuration by 13 ka compared to taiwan and the pearl river the proportion of clay derived from the area east of pearl river epr was relatively minor and less variable a local peak in the relative contribution from this area occurred during a melt water pulse event mwp 1a suggesting that a reservoir of smectite rich clays residing in coastal bays was remobilized by this marine transgression spectral analysis of the relative contributions of the three major clay sources revealed a significant periodicity of 380 years which may reflect changes in solar insolation modulating the flux of clay minerals from taiwan and the pearl river to the deposition site on a centennial scale

late glacial diatom accumulation at 9 s in the indian ocean a continuous 10 m long section consisting of roughly two thirds ethmodiscus rex a diatom and one third mixed planktonic foraminifera was identified in a core from 3800 m depth at 9 s on the indian ocean s 90 e ridge radiocarbon dates place the onset of deposition of this layer at 30 000 years b p and its termination at close to 11 000 years b p however precise dating of the foraminifera from the ethmodiscus layer itself proved to be impossible owing to the presence of secondary calcite presumably precipitated from the pore waters during the holocene high calcium carbonate content ooze free of diatoms was deposited at this locale as the site currently lies beneath the pathway taken by upper ocean waters entering the indian ocean from the pacific via the indonesian straits it appears that during glacial time thermocline waters moving along this same path provided the silica and other nutrients required by these diatoms

occurrence of thick ethmodiscus oozes associated with a terminal mid pleistocene transition event in the oligotrophic subtropical south atlantic abstract within generally calcareous sediment sequences layers of variable thickness of the giant diatom ethmodiscus were found in five cores recovered in the subtropical south atlantic between 23 and 33 s from both sides of the mid atlantic ridge two types of oozes occur almost monospecific layers of ethmodiscus and layers dominated by ethmodiscus with several accompanying tropical subtropical oligotrophic water diatoms the two thickest ethmodiscus layers occur in geob3801 6 around 29 s and accumulated during late mis 14 and mis 12 respectively downcore concentrations of ethmodiscus valves range between 3 4 104 and 2 3 107 valves g 1 we discuss the ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation the occurrence of ethmodiscus oozes in sediments underlying the present day pelagic low nutrient waters is associated with a terminal event of the mid pleistocene transition at around 530 ka when the ocean circulation rearranged after a period of reduced nadw production

sediment provenance in the western pacific warm pool from the last glacial maximum to the early holocene implications for ocean circulation and climatic change abstract sedimentary records including clay minerals major elements rare earth elements ree and 14c ages were analyzed in one core from the western pacific warm pool wpwp in order to identify the sources of sediments in the warm pool region from the last glacial maximum lgm to the early holocene the results showed that the sedimentation rate at the studied core site has decreased continuously since the lgm both major elements and clay minerals experienced staged changes in the study area in the studied core most major elemental concentrations decreased prior to 22 kyr bp but increased gradually after 13 kyr bp sediment provenance based on clay minerals and rees further revealed that sediments were likely a mixture of dominant new guinea sediments and asian dust the south equatorial current was the main force transporting new guinea particles while the east asian winter monsoon and the correlated north equatorial countercurrent might have loaded the asian dust into the study area moreover heinrich events were well imprinted in the western pacific and another cold climatic event that occurred at approximately 21 kyr bp was also recorded in the study area these events were similarly documented in ice from greenland but were undistinguished in ice from the antarctic and stalagmites from the hulu cave china a frequency analysis of multi proxies confirmed that sun irradiance essentially controlled the variation in sedimentary records in the western pacific from the lgm to the early holocene

upward flow of north pacific deep water in the northern south china sea as deduced from the occurrence of drift sediments 1 reflection seismic profiles show that drift sediments occur in the depth range of 1200 2800 m on the continental margin off southeast china these drift deposits were generated by upward flow near the dongsha islands of the north pacific deep water npdw which enters the south china sea via the bashi channel sill depth 2500 m this flow results in deposition of slope sediments resuspended off east and south taiwan on the slope southeast of the dongsha islands at 1200 m water depth this upward flow probably terminates and the npdw mixes with the surface water sediment ages from odp site 1144 southeast of the dongsha islands show that this process started at least 1 1 m y ago indications for mass wasting in the area of upslope water flow document the simultaneous occurrence of current and gravity controlled sedimentation processes however bottom current related drift sedimentation dominates

increased contribution of terrigenous supply from taiwan to the northern south china sea since 3 ma seismic profiles provide evidence that there has been strong transport by deep water bottom currents and drift deposition on the northern slope of the south china sea earlier geochemical studies suggest that the drift sediments originated primarily from taiwan however the transport process history and origin of the deep water bottom deposition in the northern south china sea on both glacial interglacial and tectonic time scales remain unclear here we show new high resolution records of clay minerals grain size and mass accumulation rate mar of terrigenous materials from ocean drilling program odp site 1144 together with trace element concentrations in siliciclastic sediments from odp site 1146 combined with other published data we find that the primary source for sediments at odp sites 1144 1148 since 3 ma is from taiwan and not from pearl river as previously thought before 3 ma however sediment source to odp sites 1146 and 1148 was mainly from the pearl river increased contribution of terrigenous supply from taiwan to the northern south china sea since similar to 3 ma may be related to the formation of the taiwan orogen and strengthening of deep water bottom current transport in the northern south china sea variations in clay mineralogy and sedimentology at odp site 1144 located on a sediment drift shows strong glacial interglacial cyclicity this suggests that bottom current deposition is highly dependent on sea level fluctuations which control the terrigenous supply to the deep sea c 2010 elsevier b v all rights reserved

geochemistry of core sediments along the active channel northeastern indian ocean over the past 50 000 years sources and climatic implications abstract major and trace elements of sediments from two gravity cores 10ydy09 and 12i712 in the northeastern indian ocean have been analyzed for sediment provenance and the relationship of the sediments with climate change since 50 ka the rare earth element ree compositions were analyzed and the sediment contributions were estimated for the major potential sources including the ganges brahmaputra g b godavari krishna g k and mahanadi rivers our results showed that the sediments in the study area were a mixture of sediments discharged from the above three rivers the sediment contribution of the g k rivers increased notably during the holocene when the rainfall increased which may be caused by the strengthening of the east indian coastal current eicc and the resulting large amounts of sediments supplied by the g k rivers the higher sediment contribution from the g b rivers demonstrated the role of the active channel in transporting sediments to the distal bengal fan during the last glacial maximum lgm especially in the late period the indian summer monsoon weakened but the winter monsoon strengthened resulting in a decrease in chemical weathering and elemental enrichment in the northeastern indian ocean conversely when the rainfall was low the chemical weathering strengthened and k2o tio2 ratios were lowered due to the longer weathering time and resulting sediment potassium loss however when the sea level reached a certain height during the holocene the fluvial sediments could not easily enter deep water environments through submarine channels which were well developed in the bengal fan

morphogenesis of a late pleistocene delta off the south western hainan island unraveled by numerical modeling abstract a paleo river delta off the south western sw hainan island has been identified based on seismic and core evidence dating results suggest its initial development in 65 kyr bp during a global sea level lowstand 85 m below modern level and termination in 56 kyr bp during a sea level highstand 50 m below modern level analysis of the delta internal architecture indicated a dominant offshore transport pathway from the sw hainan island in order to unravel possible driving mechanisms for morphogenesis of the delta 3 dimensional numerical modeling was applied to investigate oceanographic and morphodynamic scenarios corresponding to the initial delta development results indicate that sediment dynamics in the study area is controlled by a compound effect of monsoon driven circulation river plumes tides and typhoons contribution of the red river to the delta development is smaller than local rivers in sw hainan due to a combined effect by regional circulation and tides which causes a detour of the buoyancy driven plume around the delta despite of its larger runoff and sediment discharge compared to those from the local rivers of hainan on the other hand simulation results suggest at least ten times higher sediment supply rate from sw hainan during the developing phase of the river delta than the modern condition such enhanced sediment supply might be caused jointly by 1 increased local river runoff from sw hainan and 2 alongshore transport from eastern hainan which was connected to the main land during the sea level lowstand

rare earth element geochemistry of laminated diatom mats from tropical west pacific evidence for more reducing bottomwaters and higher primary productivity during the last glacial maximum rare earth elements ree along with selected major and trace elements were measured in laminated ethmodiscus rex diatom mats and associated sediments diatomaceous clay and pelagic clay in two sediment cores collected from the parece vela basin of the eastern philippine sea ree distributions are characterized by strong enrichment of middle ree mree and heavy ree hree over light ree lree and slight enrichment of mree over hree this distribution pattern suggests that ree compositions of the laminated e rex diatom mats were not the product of e rex blooms an inference also supported by the fact that ti normalized ree concentrations are not clearly different from those in the diatomaceous clay and pelagic clay comparison of ree patterns with the vertical distribution of authigenic phases in the sediment indicates that lree were dominantly associated with detrital materials whereas mree and hree were selectively enriched by mn oxyhydroxides and authigenic phosphates in the pelagic clay a weak negative ce anomaly cannot be linked to oxic depositional conditions but instead is attributed to the retention of a negative ce anomaly associated with authigenic phosphates in the laminated e rex diatom mats a weak positive ce anomaly is consistent with depositional sulfidic anoxic conditions and is interpreted to represent enhanced scavenging of reduced aqueous ce3 by barite in a strongly reducing environment moreover variably negative to positive ce anomalies in the diatomaceous clay may reflect the concurrent operation of the two processes controlling ce accumulation in the laminated e rex diatom mats and pelagic clay the study cores show a ubiquitous positive eu anomaly owing to the presence of volcanic materials the smaller eu anomaly in the laminated e rex diatom mats and diatomaceous clay relative to that in the pelagic clay may be attributed to the release of reduced eu2 from mineral phases to the sediment pore water under strongly reducing conditions previous studies have shown that the advection of lower circumpolar water lcpw strengthened during the last glacial maximum lgm which should have resulted in better ventilation of the deep eastern philippine sea evidence presented here for more reducing bottomwater conditions during the laminated e rex diatom mats formation implicates elevated primary productivity and enhanced organic sinking fluxes as primary controls on redox changes in the eastern philippine sea during the lgm enhanced primary productivity and more reducing bottomwaters during the laminated e rex diatom mats deposition resulted in a larger respired carbon pool in the deep eastern philippine sea which may have been part of a larger scale modulation of atmospheric co2 variation during pleistocene glacial interglacial cycles by deep ocean carbon storage c 2011 elsevier b v all rights reserved

clay minerals sr nd isotopes and provenance of sediments in the northwestern south china sea abstract the clay mineralogy and sr nd isotopic composition of sediments collected in the northwestern south china sea scs were investigated to understand sediment provenance and changes in the scs since the late pleistocene our results show that the clay mineral assemblages of the surface sediments are characterized by high amounts of illite and smectite and low amounts of kaolinite and chlorite the 87sr 86sr ratios of the surface sediments vary from 0 709617 to 0 734416 and end values range from 11 6 to 8 3 the clay minerals and sr nd isotope records suggest that sediments in the northwestern scs are derived from multiple sources the sediments deposited in the eastern shelf offshore of hainan originate predominantly from hainan island and south china whereas sediments in the western shelf offshore of hainan are derived mainly from indochina and hainan island however sediment source and transport mechanisms in the northwestern slope of the scs are more complicated our results suggest that input from the west may be the major sediment source but regions in the east taiwan and luzon also contribute part of the terrigenous materials downcore variations of sr nd isotopic composition in core sediments show clear glacial interglacial fluctuations higher 87sr 86sr ratios occur during glacial period indicating that the input of terrigenous materials from old continental rocks becomes one of the important sediment sources during these periods the exposure of continental shelf and southward migration of the coastline during the glacial sea level lowstand led to an increase of terrigenous supply to the northwestern slope of the scs the paleo red river and indochina are also potentially important contributors

precession and glacial cycle controls of monsoon precipitation isotope changes over east asia during the pleistocene abstract precipitation isotope reconstructions derived from speleothems and plant waxes are important archives for understanding hydroclimate dynamics their climatic significance in east asia however remains controversial here we present terrestrial plant wax stable hydrogen isotope dwax records over periods covering the last four interglacials and glacial terminations from sediment cores recovered from the northern south china sea scs as an archive of regionally integrated precipitation isotope changes in southeast china combined with previous precipitation isotope reconstructions from china we find that the scs dwax and southwest central china stalagmite 18 o records show relatively enriched and depleted isotopic values respectively during interglacial peaks but relatively similar isotopic variations during most sub interglacials and glacial periods over the past 430 thousand years during interglacial peaks strong summer insolation should have intensified the convection intensity the isotopic fractionation along moisture trajectories and the seasonality which are all in favor of causing isotopically depleted rainfall over the east asian monsoon regime these effects in combination with a relatively high proportion of indian ocean versus pacific sourced moisture influx should have resulted in strongly depleted precipitation isotopes stalagmite 18 o over most parts of china however southeast china should have been affected by a relatively low ratio of indian ocean versus pacific sourced moisture influx which dominated over effects yielding depleted precipitation isotopes and led to enriched precipitation isotopes dwax it is thus concluded that glacial boundary conditions and insolation forcing are the two most important factors for causing regional differences in precipitation isotope compositions over subtropical east asia on orbital timescales

assessing effective provenance methods for fluvial sediment in the south china sea sediment is delivered by the rivers of se asia to the south china sea where it provides an archive of continental environmental conditions since the eocene interpreting this archive is complicated because sediment may be derived from a number of unique sources and the rivers themselves have experienced headwater capture that also affects their composition a number of methods exist to constrain provenance but not all work well in this area anthropogenic impacts most notably agriculture mean that the modern rivers contain more weathered materials than they did up until about 3000 years ago the rivers have also changed their bulk chemistry and clay mineralogy in response to climate change so that these proxies as well as sr isotopes are generally unreliable provenance indicators nd isotopes resolve influx from luzon but many other sources in se asia have similar values and clear resolution of end members can be difficult instead thermochronology methods are best suited especially apatite fission track which shows more diversity in the sources than either u pb zircon or ar ar muscovite dating nonetheless even fission track is best used as part of a multiproxy approach if a robust quantitative budget is desired

reinterpretation of dinosaur footprints from the lower cretaceous of huanglonggou zhucheng shandong province china comment on tracking the yellow dragons implications of china s largest dinosaur tracksite cretaceous of the zhucheng area shandong province china by lockley et al 2015 abstract zhucheng located in eastern shandong province china is well known for its abundant early cretaceous dinosaur footprints and late cretaceous dinosaur bone fossils recently lockley et al 2015 presented a sketch study on the huanglonggou tracksite in the zhucheng area and critically commented on our paper h xu et al 2013 which conducted a detailed and comprehensive study of the tracksite here we demonstrate that some of their assumptions and comments on our work are subjective and incorrect tracks at the huanglonggou tracksite including a dominant theropod large theropod grallator yangi paragrallator corpulentapus lilasia and subordinate sauropod suspected ornithopod and turtle tracks were preserved in the yangjiazhuang formation with estimated ages of 129 to 122 ma rather than in the longwangzhuang formation as proposed by lockley and his associates contrary to lockley et al 2015 our mapping of the huanglonggou tracksite exhibits the previous work by li et al 2011 and focuses on the 50 well preserved trackways and their orientations based on the stride length to footprint size index diagram and the grallator anchisauripus eubrontes gae plexus our statistical constraints on the three species of theropods are better than those of lockley et al 2015 lockley argued that tracks at the site were preserved on at least five levels of which the majority on level 4 were of excellent preservation in fact the tracks identified throughout the site have been from only one level the false appearance of multiple levels is interpreted as the result of sedimentation at the shoreline and differential excavation of the tracksite

punctuated eustatic sea level rise in the early mid holocene whether eustatic sea level rise through the holocene has been punctuated or continuous has remained controversial for almost two decades resolving this debate has implications for predicting future responses of remaining ice sheets to climate change and also for understanding the drivers of human settlement and dispersal patterns through prehistory here we present a sea level curve for the past 8900 yr from singapore a tectonically stable location remote from ice loading effects we also present critical and unique sedimentation rate organic 13c and foraminiferal 13c proxy records of sea level change derived from a shallow marine sediment core from the same area over the same time interval the sea level curve corroborated by the independent proxy records suggests rapid rise at a rate of 1 8 m 100 yr until 8100 cal calibrated yr b p a near cessation in the rate of sea level rise between 7800 and 7400 cal yr b p followed by a renewed rise of 4 5 m that was complete by 6500 cal yr b p we suggest that this period of relatively stable sea level during the early to mid holocene enabled modern deltas to advance providing a highly productive environment for the establishment of coastal sedentary agriculture periods of rapid sea level rise before and after may have catalyzed significant postglacial episodes of human dispersal in coastal regions

new pterosaur tracks pteraichnidae from the late cretaceous uhangri formation southwestern korea numerous footprints of dinosaurs pterosaurs and birds together with arthropod tracks have been discovered in the upper cretaceous uhangri formation which crops out along the south western coastline of south korea this ichnofauna contains the first pterosaur tracks reported from asia the digitigrade tridactyl manus impressions exhibit features of a typical pterosaur hand print the pes impressions however show features that are different from pterosaur footprints reported pre viously there is no visible trace of impressions of individual digits and the toes are triangular or rounded in shape distally without distinct claw impressions as these features clearly distinguish the uhangri tracks from pteraichnus and purbeckopus we assign them to a new genus haenamichnus which accommodates the new ichnospecies haenamichnus uhangriensis the prints are five to six times larger than those of pteraichnus and are currently the largest pterosaur ichnites known they show virtually no trace of the 5th phalange of the pes indicating that they were made by pterodactyloids moreover features of the tracks suggest that they can be attributed to azhdarchids the commonest pterosaur of the late cretaceous the longest pterosaur trackway yet known from any track site length 7 3 m and consisting of 14 pairs of foot impressions was also found in the uhangri formation and suggests that azhdarchids at least were competent terrestrial locomotors the fossil track site at uhangri represents the first occurrence of the tracks of pterosaurs dinosaurs and web footed birds all on the same level this demonstrates that pterosaurs and birds visited the same habitat but the large size disparity suggests that they occupied different ecological niches

anomalous south atlantic lithologies confirm global scale of unusual mid pleistocene climate excursion abstract carbonate rich nannofossil oozes are the typical sediments deposited under the low productivity regime of the subtropical gyre in the south atlantic surface productivity has remained virtually constant during the late pleistocene schmiedl and mackensen palaeogeogr palaeoclimatol palaeoecol 130 1997 43 80 increasing slightly only during the most extreme glacial periods recently the puzzling occurrence of thick monospecific diatom layers ethmodiscus rex has been reported within the carbonaceous sequences of two sediment cores in the south atlantic gyre schmieder et al earth planet sci lett 179 2000 539 549 the layers dated 544 534 ka are isochronous and record a period of increased organic carbon flux above them at 530 524 ka unusually high carbonate contents are recorded this double feature of anomalous lithologies is unique in the sediment record of the last 1500 kyr and can be related to the terminal event of the mid pleistocene climate transition mpt the mpt is characterized by reduced thermohaline circulation and stronger carbonate dissolution schmieder et al earth planet sci lett 179 2000 539 549 reduced circulation and a more stratified water column may have trapped nutrients in deep nitrate pools and may have fostered favorable conditions for the development of deep dwelling populations of e rex the onset of more turbid conditions led to the rapid settling of diatom populations subsequently introduced nutrients to the surface layer and improved calcite preservation thus creating a biogenic silica carbonate double peak the carbonate peak is synchronous with an unusual mid pleistocene sapropel observed in the mediterranean which is attributed to a massive odd monsoon over central africa rossignol strick et al nature 392 1998 269 272 since summer insolation was relatively low during this time the formation of this thick sapropel cannot be explained in terms of current understanding of astronomical forcing rossignol strick et al nature 392 1998 269 272 a non linear response to a 400 kyr low frequency climatic cycle as discussed for the mediterranean sapropel is not confirmed by data from our south atlantic core records

a new regional mid holocene palaeoprecipitation signal of the asian summer monsoon the dongge cave speleothem 18o record which lies in the pearl river basin china has been interpreted as recording a regional decline in asian summer monsoon precipitation over the last 6 5 ka the same overall trend is seen in the bulk sedimentary organic 13corg record from a core in the pearl river estuary however the two records differ in detail and the regional nature of the dongge palaeoprecipitation signal has therefore been questioned our study re evaluates both records by constructing for the same estuarine core biomarker and compound specific 13c records which have better constrained terrestrial and marine end members than 13corg providing additional insights into the evolution of the asian summer monsoon the branched isoprenoidal tetraether bit index reflects the ratio of soil versus marine organic matter the bit record from the estuarine core co varies with the dongge cave 18o record suggesting the two share a common control which is likely to be driven by regional climate by contrast the sterols n alcohols and n fatty acid ratios show the same overall trend as dongge but parallel the 13corg record s variability between 6 5 and 2 ka indicating a partial decoupling between soil and land plant organic matter fluxes in the pearl river basin there is clear divergence between the biomarker and 13corg records from 2 ka to present analysis of the leaf wax 13c suggests that this results from an abrupt change in vegetation probably resulting from local anthropogenic cultivation two thousand years ago the basin scale of these estuarine records equates to up to 15 grid cells in typical earth system models used for simulating global climate this permits comparison of palaeoclimate model intercomparison project simulations of the mid holocene with spatially equivalent data relating to the summer asian monsoon for the first time

sea level induced variations in clay mineral composition in the southwestern south china sea over the past 17 000 yr variations in clay mineral composition of sediment cores from the margin and continental slope of the sunda shelf southern south china sea se asia covering the past 17 000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters we identify the deglacial sea level rise as the principal factor driving these changes during the late glacial high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed sunda shelf and in the southern archipelagos of indonesia at this time core sites were located in close proximity to the mouths of the sunda shelf palaeo drainage systems on the emerged shelf sundaland the progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite rich southern sources when the coastline had retreated closely to its present day position in mid holocene times the former dominance of southern sources was replaced by a stronger influence of illite rich sources e g borneo the overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic monsoonal changes in such highly dynamic sedimentary environment

source to sink transport processes of fluvial sediments in the south china sea the south china sea offers an excellent case for studying source to sink transport processes of fluvial sediments among the global marginal seas this study synthesizes existing clay mineralogical and geochemical data from similar to 1500 samples from the seafloor and surrounding rivers deepwater mooring observation results and high resolution glacial cyclic clay mineralogy records from six high quality sediment cores source to sink sediment transport from the river mouth to the continental shelf and then to the abyssal basin is investigated at two time scales modern process and late quaternary glacial cycles the results firstly show the high diversity of clay mineralogical and geochemical compositions in riverbed surface sediments surrounding the south china sea e g dominant illite and chlorite in taiwan overwhelming majority of smectite in luzon dominant kaolinite in south china and similar amounts of the four clay mineral species in red and mekong river systems the formation of these fluvial sediments through chemical weathering in surrounding drainage systems is controlled principally by the east asian monsoon climate with warm temperature and high precipitation and subordinately by tectonic activity and specific lithological character the basin wide distribution of clay mineral assemblages combined with neodymium and strontium isotopic compositions reflects strong provenance control and differential settling effects the differential settling of kaolinite in slightly saline and proximal regions relative to smectite in more saline and distal regions is well demonstrated in the south china sea through combining clay mineralogical distributions on the seafloor with observed oceanic current systems the modern transport pathways can be well established e g in the northern south china sea illite and chlorite from taiwan are mainly carried by contour currents with the strong influence of mesoscale eddies high resolution sediment dynamic analysis for the late quaternary reveals different sediment transport patterns in the northern western and southern south china sea when the land sea configuration dramatically changed during glacial conditions in the north the terrigenous dispersal is mainly controlled by provenance supply and oceanic current transport in the west the clay mineral assemblage reflects variations of the prevailing surface current influenced by monsoon winds in the south the clay mineral input indicates intensive chemical weathering during interglacial periods and strengthened physical erosion during glacial periods the transport of terrigenous sediments since the last glaciation is quantitatively reconstructed through studying two deepwater sediment cores located in the northern south china sea the relative contributions from three provenances south china luzon and taiwan highlight their distinct variability over the last 28 ka implying that the southward shift of the inter tropical convergence zone itcz at 16 ka bp caused an increased sediment contribution from south china the intensified influence of the kuroshio current intrusion controls more efficient westward transport of luzon sediments and the stronger deepwater current transports taiwan sourced sediments further westward from the last glaciation to the holocene c 2015 elsevier b v all rights reserved

new interpretation for the main sediment source of the rapidly deposited sediment drifts on the northern slope of the south china sea abstract the slope of the northern south china sea scs is one of the world s most active areas of modern marine sedimentary processes a rapidly deposited sediment drift rdsd was identified on the slope near dongsha island the sources of this body have been studied and discussed by several authors but no consensus has been achieved based on multi channel seismic profiles interpretation and data analysis of long term observation of bottom currents we identified that although the amounts of sediments input from the pearl and hanjing rivers and from kao ping and tseng wen rivers are large considering the current situation of northern scs none of the pearl river the hanjiang river the kao ping river and the tseng wen river can maintain the deposition pattern of the northern scs margin as the single source especially to maintain the supper high sedimentation rate at the rdsd area the miocene drape formation mdf calmly draped over an unconformity after rifting stage resulting in a relatively constant thickness of about 2000 m throughout the overall northern scs continental margin and followed by a standard configuration of a clinoform the pliocene formation and another clinoform of about another 700 m in total thickness due to dongsha uplift since 3 ma roughly 1 2 of mdf and the n2 formation in the dongsha area measures 150 km by 200 km were denudated resulting in an average annual denudation rate of 60 106 t y if these sediments were deposited on a slope region within an area measuring 100 km by 100 km the sedimentation rate could reach 250 cm ky this is clearly an impressive new sediment source that has never been discussed before moreover the rdsd is near the dongsha uplift and on the adjacent slope we believe that this new sediment source should be the main contributor for the rdsd development

the climate response of the indo pacific warm pool to glacial sea level growing climate proxy evidence suggests that changes in sea level are important drivers of tropical climate change on glacial interglacial time scales these paleodata suggest that rainfall patterns over the indo pacific warm pool ipwp are highly sensitive to the landmass configuration of the maritime continent and that lowered sea level contributed to large scale drying during the last glacial maximum lgm ca 21 000 years before present using the community earth system model version 1 2 cesm1 we investigate in detail the mechanisms by which lowered sea level influenced the climate of the ipwp during the lgm the cesm1 simulations show that in agreement with previous hypotheses changes in atmospheric circulation are initiated by the exposure of the sunda and sahul shelves ocean dynamical processes amplify the changes in atmospheric circulation by increasing the east west sea surface temperature sst gradient along the equatorial indian ocean the coupled mechanism driving this response is akin to the bjerknes feedback and results in a large scale climatic reorganization over the indian ocean with impacts extending from east africa to the western tropical pacific exposure of sahul shelf and the associated changes in surface albedo play a key role because it is more effective at exciting the positive feedback than exposure of the sunda shelf this mechanism could explain the pattern of dry wet eastern western indian ocean identified in climate proxies and lgm simulations however this response also requires a strengthened sst gradient along the equatorial indian ocean and it is currently unclear whether this is detectable in marine paleoreconstructions strategies to resolve this issue are discussed

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

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

sediment supply to the continental shelf by the major rivers of china the yalu luan the yellow changjiang and pearl rivers discharge 90 of china s total annual input of 20 14 10 8 t of sediment to the sea this huge volume of sediment is deposited in the river mouths and in the vicinity of the inner shelves in the form of deltas or submarine sandy ridges depending upon the dominant processes or dynamics of the area even though the continental shelves of the china seas were coastal plains during the late pleistocene modern river sediments rarely extend to the outer shelves except in response to changes in sea level

clay mineral compositions in surface sediments of the ganges brahmaputra meghna river system of bengal basin bangladesh abstract clay minerals are significant indicators that can be used to identify sources and transport patterns of both fluvial and marine sediments the ganges brahmaputra and surma meghna sm rivers are the most important rivers of the bengal basin bb loading a large amount of sediments from the himalayas into the bay of bengal clay minerals of 132 surface sediment samples from the ganges brahmaputra meghna gbm river system have been analyzed with x ray diffraction xrd to show the variation of clay mineral assemblages in the sediments from upstream to downstream for the major rivers of the bb and to verify the validity of clay minerals as an important index for sediment provenance in the bay of bengal after these sediments are discharged into the neighboring seas the results show that the clay mineral assemblage in the gbm river system consists dominantly of illite average 66 with smaller amounts of smectite kaolinite and chlorite 8 8 and 17 respectively smectite is diagnostic in the ganges river sediments with a higher content 23 than that in the brahmaputra 2 and the sm river 1 however chlorite 21 is high in the sm river sediments and the brahmaputra river sediments have a high illite percentage 77 downstream the smectite percentages in the ganges river increase significantly but the kaolinite percentages in sediments of the sm river increase slightly due to the continuous mixture of first the brahmaputra river and then the sm river discharge the clay mineral assemblages of this river system s sediments change greatly e g smectite percentages decrease from 23 in the ganges river to 8 in the gbm river via the stretch with 12 in the ganges brahmaputra confluence river

on the occurrence of the giant diatom ethmodiscus rex in an 80 ka record from a deep sea core southeast of sumatra indonesia implications for tropical palaeoceanography environmental changes recognised in a 80 ka record obtained from a deep sea core taken at a water depth of 2542 m offshore southeast sumatra conclusively indicate for the first time that blooms of the giant diatom ethmodiscus rex occurred in the indian ocean during the last glacial period with the largest numbers coinciding with the last glacial maximum previous occurrences of e rex in both the indian and the western pacific oceans could not be dated due to the paucity of foraminifers and contamination by diagenetic carbonate found in association with the diatoms we use a reliable n 18 o record to date the core the interpretation of terrigenous clays and trace metals in the core sediments together with carbon isotopes measured on planktic foraminifers suggests that conditions that favoured the diatomaceous blooms were a combination of changes in hydrological regime in the region caused by a substantial increase in salinity near the surface and coinciding with a rise in nitrate levels near the surface no major upwelling was recorded during glacial times during the glacial period the indonesian archipelago as other tropical regions was much drier thus preventing a low salinity cap to occur at the surface of the oceans in contrast with the holocene in addition monsoonal winds were absent thus permitting the ocean to be permanently stratified with high levels of silica and nutrients near the surface the glacial mode of productivity represented by the blooms of e rex added considerable amounts of biogenic silica to the sediment but is not reflected by classic productivity proxies like biogenic barium therefore we have to distinguish between a classic productivity mode as observed in the photic zone today and a glacial deep productivity dominated by e rex which may have utilised nutrients from a wider depth range 9 2002 elsevier science b v all rights reserved

temporal and spatial patterns of sediment deposition in the northern south china sea over the last 50 000 years abstract sediment depositional patterns along the upper continental slope of the northern south china sea scs have been studied using two sediment cores geob16601 6 20 09 07 n 116 14 38 e 1012 m water depth and geob16602 4 18 57 12 n 113 42 64 e 951 m water depth recovered during rv sonne cruise so 221 invers sediment cores were analyzed for bulk sediment element composition by x ray fluorescence xrf core scanning and clay mineral assemblage by x ray diffraction xrd the bulk sediment element and the clay mineral compositions of the two cores suggest similar depositional patterns between 50 kyr bp and 29 kyr bp and 14 kyr bp to present but a clear difference in depositional patterns during the last glacial and deglacial 29 14 kyr bp when sea level was below 90 m between 29 14 kyr bp a higher kaolinite percentage in core geob16602 4 in comparison to core geob16601 6 is interpreted to reflect a higher contribution of clay supplied by the pearl river to core site geob16602 4 in contrast core geob16601 6 received less pearl river supplied clayey material during the same period when the sea level was below 90 m during the last glacial lowstand the detrital fine grained materials supplied by the pearl river were mostly transported by coastal currents to the southwest resulting in a higher contribution of pearl river discharged material at site geob16602 4 than at site geob16601 6 we suggest that sea level induced modifications of the land ocean distribution together with changes in the palaeo physiographic conditions such as the proximity of the palaeo rivers to the individual core sites might be responsible for the different sediment depositional patterns in the study area thus the overriding control of sea level induced changes on the sediment depositional environment might mask climate related changes in sediment depositional pattern in the northern scs

more reducing bottom water redox conditions during the last glacial maximum in the southern challenger deep mariana trench western pacific driven by enhanced productivity abstract the modern southern mariana trench is characterized by oligotrophic surface waters resulting in low primary productivity and well oxygenated bottom waters this study investigates changes in the redox conditions of bottom waters in the southern mariana trench during the last glacial maximum lgm and their potential causes we measured major trace and rare earth elements ree in three gravity cores gc03 gc04 and gc05 and one box core bc11 retrieved from the southern challenger deep at water depths from 5289 to 7118 m the upper sediment layers of both gc05 and bc11 are dominated by valve fragments of the giant diatom ethmodiscus rex forming laminated diatom mats ldms 14c ams dates of bulk organic matter show that the ldms accumulated between 18 4 and 21 8 kyr b p corresponding to the lgm modest enrichments of u and mo along with weak or absent ce anomalies in the ldm point to suboxic conditions during the lgm in contrast non ldm samples exhibit little to no enrichment of redox sensitive elements as well as negative ce anomalies indicating deposition under oxic bottom water conditions the ce anomalies are considered valid proxies for bottom water redox conditions because ree signatures were acquired in the early diagenetic environment as indicated by strong p ree correlations and middle ree enrichment associated with early diagenetic cycling of fe mn oxyhydroxides in the sediment column followed by capture of the ree signal by biogenic and or authigenic apatite we postulate that the more reducing bottom water conditions during the lgm were linked to increased primary productivity induced by enhanced asian dust input as shown in earlier studies the increased primary productivity associated with ethmodiscus rex blooms in the eastern philippine sea played a significant role in capturing atmospheric co2 during the lgm consequently the magnitude of atmospheric co2 sequestration by giant diatom blooms during the lgm may have been greater than previously envisaged

a 35 000 year record of changes in the eastern indian ocean offshore sumatra article i nfo we have examined the upper 276 cm of deep sea core bar9403 taken at a water depth of 2034 m offshore the southern portion of sumatra in the eastern indian ocean using several micropalaeontological proxies faunal counts and stable isotopes of oxygen and carbon of planktic and benthic foraminifers as well as floral counts of dinoflagellates were obtained to reconstruct conditions in the oceans over the last 35 000 years at times we found that when benthic foraminifers indicate high organic content values at the bottom of the ocean this is not paralleled by high productivity signals at the sea surface but instead must relate to changes in bottom water circulation as a result of slower water circulation the marine isotopic stages mis 3 1 are clearly differentiated by benthic and foraminiferal assemblages as well as dinoflagellates and their cysts mis 3 is characterised by a much sharper than today thermocline that was closer to the sea surface and by the absence of a low salinity barrier layer which today results from high monsoonal rains the absence of the latter persisted during the last glacial period mis 2 when bottom circulation must have been reduced and high percentages of organic matter occurred on the sea floor combined with low dissolved oxygen levels the deglaciation is marked by a change in salinity at the sea surface as seen by the dinoflagellates and planktic foraminifers and progressive alteration of the thermocline was detected by foraminifers suggesting a less productive deep chlorophyll maximum in contrast with mis 3 and 2 monsoonal activity commenced around 15 000 cal years ago and was well established 2000 years later the holocene is marked by a significant increase in river discharge to the ocean pulsed by the delivery of organic matter to the sea floor despite overall oligotrophic conditions at and near the sea surface induced by a permanent low salinity cap we did not identify obvious and persistent upwelling conditions offshore sumatra for the last 35 000 years

influence of the kuroshio current intrusion on depositional environment in the northern south china sea evidence from surface sediment records the influence of the kuroshio current kc intrusion on the depositional environment of the northern south china sea scs is discussed based on multi proxies of surface sediments including planktonic foraminifera clay minerals and geochemical elements the results reveal that four typical planktonic foraminifera globigerinoides ruber g sacculifer neogloboquadrina dutertrei and pulleniatina obliquiloculata can be used to trace the kc flow route in the northern scs globigerinoides ruber is mainly distributed in shallower water than the south china sea branch of the kuroshio scsbk flow route while p obliquiloculata is mostly distributed in deeper water than the scsbk flow route there are high percentages of g sacculifer and n dutertrei at the scsbk flow route along the 1000 m isobath where bottom sediments consist of clayey silt and silty clay the scsbk also affects sediment distribution of various sources taiwan sourced sediments characterized by high illite and chlorite contents are transported southwestward into the deep sea environment by the scsbk and or deep water current the pearl river sediments characterized by high kaolinite and titanium ti contents are mostly transported southwestward to be distributed in the sea environment between the pearl river mouth and southeast of hainan island but hardly entered the abyssal basin the luzon island sediments characterized by high smectite content are generally deposited at the northwest of luzon island under the effect of an eddy west of luzon island these sediments were hardly transported northwestward onto the northern shelf of the scs throughout the scsbk flow route the sedimentary environment at the northwest of luzon island is relatively oxidized and higher in salinity than the northern scs which is probably connected with the kc intrusion through the luzon strait

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

cyclone driven deep sea injection of freshwater and heat by hyperpycnal flow in the subtropics china 973 program 2009cb421200 program of introducing talents of discipline to universities b07034 academia sinica thematic program afobi taiwan nsc 98 2116 m 001 005

implications of late eocene to early miocene clay mineral assemblages in mcmurdo sound ross sea antarctica on paleoclimate and ice dynamics abstract the clay mineral assemblages of upper eocene to lower miocene sediments recovered at the ciros 1 and mssts 1 drill sites on the mcmurdo sound shelf antarctica were analyzed in order to reconstruct the cenozoic antarctic paleoclimate and ice dynamics the assemblages are dominated by smectite and illite with minor amounts of chlorite and kaolinite the highest smectite amounts and best smectite crystallinities occur in the upper eocene part of ciros 1 below 425 445 mbsf they indicate that during their deposition chemical weathering conditions prevailed on the nearby continent large parts of east antarctica were probably ice free at that time but some glaciers reached the sea and contributed to the glaciomarine sedimentation in contrast only minor total amounts of smectite are present in oligocene and younger sediments due to the shift to mainly physical weathering on an ice covered antarctic continent however relative smectite percentages rise to more than 60 during two late oligocene intervals ca 27 5 26 2 and 25 0 24 5 ma and during one early miocene interval starting at ca 23 3 ma these intervals are characterized by ice masses coming probably from the south where volcanic rocks acted as a source as also indicated by the composition of the sand and gravel fractions during the other intervals the ice came from the west where the physical erosion of basement rocks and sedimentary rocks of the beacon supergroup in the transantarctic mountains provided high illite concentrations because the two drill sites are only 4 km apart their clay mineral records can be correlated this led to a new interpretation of the oligocene paleomagnetic data of the mssts 1 site and to a more detailed lithostratigraphic correlation of the miocene parts of the cores

geochemistry of the surface sediments of the sulu and south china seas abstract the chemical and mineralogical composition of the surface sediments of the sulu sea a deep hydrographically restricted basin in the indonesian archipelago and the neighbouring area of the south china sea have been examined the aim of the study was to characterize the geochemistry of the sediments of the isolated oxygen deficient basin and to compare them with sediments at equivalent water depths outside the basin as a prelude to a further study of the response of the composition of the sediments to oceanographic changes including possible anoxia during the last glacial maximum the concentrations of most of the chemical constituents in the surface sediments along four transects change markedly with water depth in the sulu sea ss and the south china sea scs thus caco 3 decreases from around 60 by weight in the shallowest samples 800 1000 m to around a few percent in the deepest sample at 4203 m in the scs where the ccd lies at around 4000 m in the ss however the ccd lies much deeper so that the caco 3 contents are still approximately 40 at 4500 m depth organic c also decreases with depth in both basins from values of around 1 2 in the shallowest samples to less than 1 in the deepest samples the ratios of si mg na k co cr cu ni pb rb y zr and zn to al all decrease with increasing water depth because of the change in mineralogy and sediment texture with water depth the p al is higher in shallower water in both areas because of the higher abundance of detrital phosphorite or phosphatized limestone in these sediments the sr al ratio is also higher in shallower water reflecting the supply of aragonitic shell debris from the shallow banks and shelves around the basin the ba al ratio has a maximum at 2000 m depth in the scs due to higher primary production in overlying surface waters whereas it is uniformly low in the ss manganese is also enriched at intermediate water depths in both the ss and the scs because of the presence of oxyhydroxides and this also produces a slight enrichment in mo in the same samples because of their association in this authigenic phase the concentration of i and the i c organic ratio decreases with water depth in both areas due to the higher abundance of fresh marine organic matter at the shallow water sites which scavenges proportionally more i from sea water finally the 13 c organic values tend to decrease irregularly with increasing water depth probably reflecting a higher contribution of terrestrial organic matter in deeper water a discriminant analysis of the full data set reveals that compared with the scs samples the oxygen deficient ss sediments have higher caco 3 contents lower n and s contents and lower i c organic ba al fe al k al pb al rb al ti al v al y al and zn al ratios these contrasts are brought about by the different depths of the ccd differences in the nature of the organic matter and different types of aluminosilicate detritus in the two areas although the i c organic ratios are slightly but significantly lower in the ss which may be due to the low dissolved oxygen contents of the waters of this basin the mn and mo contents and other minor elements that respond significantly to ambient bottom water oxygen levels are not significantly different in the ss and the scs moreover the organic c contents are also indistinguishable in the two areas hence the low bottom water oxygen levels in the ss do not lead to higher organic carbon contents in the surface sediments the composition of sediments in contact with waters having even lower oxygen concentrations should be evaluated in order to conduct a more definitive test of the effect of low oxygen conditions on carbon preservation comparison of glacial interglacial sediment sections from this area must take particular care to separate the effects of source variations on those potentially caused by low oxygen levels

north america s largest dinosaur trackway site implications for morrison formation paleoecology little known exposures of the upper jurassic morrison formation from the purgatoire valley of southeastern colorado have yielded the world s largest continuously mapped assemblage of dinosaur trackways body fossils include plant invertebrate and vertebrate remains indicative of predominantly fresh water conditions the tracks occur in a lacustrine sequence characterized by 1 shallow water shales 2 micritic shoreface limestones with ooids intraclasts ripple marks mud cracks and 3 minor quartzose sandstone with salt crystal casts analysis of these sedimentary facies suggests that in southeastern colorado lakes were larger and longer lived than in other morrison paleoenvironments trackway orientations and footprint depth contours pinpoint the location of the paleoshoreline at successive levels in the section detailed mapping of 1 300 footprints in bed 2 has revealed more than 100 trackways which testify to the activity of both quadrupedal and bipedal dinosaurs the respective ratio based on trackway counts is 40 60 the quadrupedal tracks are attributed to sauropods and represent the first ever discovered in north america they also exhibit the first known manus claw impressions and are in need of formal description more than 90 of the bipedal tridactyl prints lack claw impressions and are tentatively therefore referred to the ornithopoda cf gypsichnites possibly a camptosaurus the small proportion with distinct claw impressions may represent allosaurus resulting estimates of species diversity 5 and predator prey ratio 1 30 are in general agreement with the estimates of other authors based on skeletal remains and they suggest that the purgatoire river tracks may accurately reflect the composition of the dinosaur fauna distinctive groupings of parallel non overlapping trackways suggest gregarious behavior among sauropods and tridactylous forms

sedimentary evidence of late holocene human activity in the pearl river delta china this study examines the sedimentary evidence of human activities during the last 4000 years in the pearl river deltaic area the analyses are focused on indentifying agricultural signatures present in the sedimentary record and establishing the timing of a change from a simple rice based agriculture to a more advanced diverse agriculture the examination is based on modern sediment and plant samples and a sediment core collected from the deltaic area the analyses include particle size and diatom analysis to determine the environmental conditions that were associated with the period of human activities organic carbon isotope ratios and major metal elements reveal an expansion in commercial crop production and metal smelting in the pearl river delta area about 2000 years ago the input of organic matter from introduced sugarcane a c4 plant elevates the bulk organic carbon isotope values in the estuarine sediments above that represented by other common agricultural crops in the study area including rice banana and lotus which are all c3 plants the increase in bulk organic isotopic value coincides with the rise in the concentration of copper iron and lead in the sedimentary sequence suggesting a wider use of metal tools these results indicate that advanced agriculture started about 2000 years ago as an expansion in human population took place in the area this record also provides sedimentary evidence that help ascertain the timing and type of human activities that are linked to subsequent land reclamation on the deltaic plain resulting in rapid shoreline advancement in the last 2000 years copyright 2010 john wiley sons ltd

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

diatom mats in gulf of california sediments implications for the paleoenvironmental interpretation of laminated sediments and silica burial preservation of laminations in hemipelagic and pelagic sediments is routinely attributed to reduced oxygen conditions that inhibited benthic activity as such the degree of preservation of laminae is used commonly as a paleo oxygenation indicator recent evidence from deep sea pelagic sediments in the eastern equatorial pacific and north atlantic however demonstrates that preservation of laminae may occur by rapid deposition of ungrazed thalassiothrix longissima diatom mats that overwhelm the benthos in otherwise oxic bottom waters here we report that similar diatom mat laminae are common in hemipelagic sediments of the guaymas basin in the gulf of california have aided preservation of the laminated sediment sequence and have also enhanced opal burial examples of diatom mats influencing sediment preservation are also described from the northern california margin and from the miocene monterey formation southern california thus even in classical settings of laminated sediment occurrence caution needs to be taken in correlating degree of lamina preservation with paleo oxygen levels such studies must be underpinned by detailed microfabric and micropaleontological analyses

the silicon isotope composition of ethmodiscus rex laminated diatom mats from the tropical west pacific implications for silicate cycling during the last glacial maximum the cause of massive blooms of ethmodiscus rex laminated diatom mats ldms in the eastern philippine sea eps during the last glacial maximum lgm remains uncertain in order to better understand the mechanism of formation of e rex ldms from the perspective of dissolved silicon dsi utilization we determined the silicon isotopic composition of single e rex diatom frustules 30sie rex from two sediment cores in the parece vela basin of the eps in the study cores 30sie rex varies from 1 23 to 0 83 average 1 04 a range that is atypical of marine diatom 30si and that corresponds to the lower limit of reported diatom 30si values of any age a binary mixing model upwelled silicon versus eolian silicon accounting for silicon isotopic fractionation during dsi uptake by diatoms was constructed the binary mixing model demonstrates that e rex dominantly utilized dsi from eolian sources i e asian dust with only minor contributions from upwelled seawater sources i e advected from subantarctic mode water antarctic intermediate water or north pacific intermediate water e rex utilized only 24 of available dsi indicating that surface waters of the eps were eutrophic with respect to silicon during the lgm our results suggest that giant diatoms did not always use a buoyancy strategy to obtain nutrients from the deep nutrient pool thus revising previously proposed models for the formation of e rex ldms

reconstruction of holocene monsoon history from the pearl river estuary southern china using diatoms and carbon isotope ratios this study employs a multiproxy approach in the reconstruction of holocene monsoon history from sedimentary sequences obtained from the pearl river estuary southern china a set of modern surface sediment samples were collected within and outside the estuary and a sediment core was obtained from the mouth of the estuary a range of modern environmental variables were recorded including water salinity summer winter and annual average and water depth the diatom results show a good relationship with water salinity with marine diatoms dominating the more distal samples from outside the main estuary and freshwater diatoms dominating the proximal samples influenced by higher freshwater flux this pattern is matched by the bulk organic carbon isotopes the isotope values vary between 21 1 0 3 0 for samples from the fully marine environment between 23 2 0 8 and 23 7 0 8 for samples from the mid to outer estuary brackish water environment and less than 24 7 1 3 for samples from the inner estuary close to the freshwater sources similarly the c n ratios vary from below 7 0 6 in the marine end members to over 14 8 3 0 in the freshwater end members both the diatom and carbon data from the sediment core reveal a significant increase in freshwater flux from 8500 cal yr bp resulting from the enhanced summer monsoon regime in early holocene the strength of freshwater flux reached its highest between 7500 and 6000 cal yr bp in the last 6000 years freshwater flux decreased towards present reflecting a gradual weakening of the summer monsoon

history of the south java current over the past 80 ka a sediment core located below the present south java current sjc was used to reconstruct paleoclimate and paleoceanography on the basis of biogenic and terrigenic proxy records the core spans the past 80 ka of environmental change and shows considerable contrasts from the glacial to the holocene presently the core site is situated beneath a seasonally varying low salinity tongue which is advected from the java sea via the sunda strait it carries terrigenous matter of a characteristic signature during the last glacial period stage 4 2 when sea level was lower than during the holocene the sunda strait was closed and the terrigenous supply from that source ceased as the core site is close to the equator our results indicate that atmospheric and oceanographic circulation was alternatively dominated by the northern hemisphere east asian monsoon system and the southern hemisphere australian monsoon system between 20 and 12 ka the australian se winter monsoon reached its maximum and intensified the westward flowing sjc increased mixing of the surface waters led to a slight rise in paleoproductivity a similar but much weaker situation prevailed from 74 to 70 ka during most of the glacial period from 70 to 20 ka strong northeasterly winds associated with the east asian winter monsoon intensified the indian monsoon current and the eastward flowing sjc and may have also carried dust across the equator to our core site during this glacial phase populations of the giant diatom ethmodiscus rex were thriving and may indicate a reduced deep and intermediate thermohaline circulation at the site the monsoonal system as we know it today with distinct dry and wet seasons may not have been active before v12 ka 2002 elsevier science b v all rights reserved

new archive of another significant potential sediment source in the south china sea abstract sediment provenance is an important part of the sediment source to sink transport process from land to sea however we sometimes cannot explain some contradictory problems well when assessing sediment sources in certain areas the northern south china sea scs is currently considered to be dominantly supplied with sediments from the pearl river taiwan and luzon for smectite one type of clay mineral luzon is normally thought to be a significant source when considering only the high smectite percentages in luzon derived sediments and neglecting their limited sediment discharge into the sea and longer transport distance of its sediments from this island recently clay mineral compositions of the pearl river originated sediments were reported to change from rich in smectite from 2500 years ago due to the anthropogonic activities by contrast the wide area in the east of the pearl river epr is similarly characterized by sediments with high smectite percentages and a shorter transport distance than those from luzon however a previous study showed that surface sediment samples with high smectite percentages were occasionally distributed in bays here we present a sediment archive of 16 gravity cores from neighboring bays harbors along the northern scs coast unlike surface sediments with low smectite percentages core sediments from the coastal bays harbors of the epr show high smectite percentages indicating that the epr besides the pearl river and or luzon might be as another potential sediment source for the northern scs in south china widely distributed igneous rocks volcanic materials are prodigious sources for sediments in the northern scs slope in future work weathering of local materials must be considered when differentiating various sediment sources

magnetic susceptibility variations and provenance of surface sediments in the south china sea magnetic susceptibility ms and grain sizes of surface sediments are measured to characterize sediment sources and their distribution in the south china sea scs distribution characteristics of ms of bulk samples msb fine grained fraction msf and coarse grained fraction msc are examined to explore the factors affecting ms values in sediment transport and deposition processes affected by dilution of quartz and carbonate abundance msc is not suitable for tracing sediment sources in the region instead msf provides a good parameter for tracking transport and deposition of complex and coarse grained sediments such as those from luzon island volcanics and from the pearl and mekong rivers which often have high msf values showing a decreasing trend with water depth on the continental shelf water depth 200 m to the west of luzon island kuroshio intrusion into the scs is the predominant factor for sediment transport after high msf volcanic materials from the luzon island are discharged into the sea sediments from the pearl river are transported southwestward under the china coastal current and then deposited between the pearl river mouth and hainan island to the southwest of taiwan island in the northeastern scs where sediments are mainly derived from taiwan island and or the yangtze river both the kuroshio intrusion and the china coastal current are significant in determining sediment transport and deposition in the south most of high msf sediments from the mekong river are transported eastward under the influence of northeastward currents in summer after entering the sea and then deposited on the northern sunda shelf c 2010 elsevier b v all rights reserved

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

sediment sources and east asian monsoon intensity over the last 450 ky mineralogical and geochemical investigations on south china sea sediments a coupled approach based on clay mineral assemblages and isotopic data sr and nd of sediment from ocean drilling program odp site 1145 has been used to trace the sources of sediment feeding the northern part of the south china sea and to investigate the evolution of east asian monsoon intensity over the last 450 ky clay mineral assemblages are dominated by illite and smectite with lesser abundance of chlorite and kaolinite 87 sr 86 sr and end 0 isotopic data combined with the smectite illite chlorite ratio indicate that the pearl river is the main contributor for detrital material to the northern margin of the scs with variable continental input of volcanic material derived from the erosion of the luzon arc these inputs follow the low latitude solar insolation with a 23 ky periodicity as recorded by a periodic change of the clay mineralogy for the first time this study presents a scs deep sea sediment high resolution record of climatic changes in the last 450 ky showing that smectite illite chlorite variations are mainly related to changes in the east asian summer monsoon intensity because the mineralogical record is independent of other external forcing phenomena such as global glacial interglacial oscillations the smectite illite chlorite ratio has been used here as a proxy to reconstruct past changes of the south east asian summer monsoon intensity d 2005 elsevier b v all rights reserved

toba ash layers in the south china sea evidence of contrasting wind directions during eruption ca 74 ka two cores from the southern south china sea contain discrete ash layers that mainly consist of rhyolithic glass shards on the basis of the specmap time scale the ash layers were dated to ca 74 ka the age of the youngest toba eruption in northern sumatra this link is supported by the chemical composition of the glass which is distinct from volcanic glass supplied from the philippines and the northern south china sea but is almost identical with the chemistry of the toba ash the youngest toba ash layers in the south china sea expand the previously known ash fall zone over more than 1800 km to the east the dispersal of ashes from sumatra in both western and eastern directions indicates two contrasting wind directions and suggests that 1 the toba eruption probably happened during the southeast asian summer monsoon season and 2 the volume of erupted magma was larger than previously interpreted

late pleistocene nutrients and sea surface productivity in the south china sea a record of teleconnections with northern hemisphere events surface nutrient variations during the last 200 000 years have been reconstructed based on the cd ca ratios in the tests of planktonic foraminifera neogloboquadrina dutertrei and the biogenic opal content from two gravity cores retrieved from the northern and northwestern parts of the south china sea scs the cd ca ratios obtained from n dutertrei in recent sediments from fourteen box cores distributed over the scs basin reflect present nutrient levels in the overlying surface waters areas with relatively high cd ca values in the surface sediments are in the region of high chlorophyll a in the northern south china sea near the dongsha islands consistent with previous observation high values of cd ca found in sediments east of vietnam and east of the nansha islands may be a result of increased nutrients due to local upwelling induced by the summer monsoon core 17940 2 raised from the northern continental slope of the scs exhibits exceptional high sedimentation rates 25 85 cm kyr for the last 35 kyr the cd ca ratios in this core are relatively higher during the periods of late d 18 o stage 3 and the mid holocene core 17950 2 with an average sedimentation rate of 5 cm kyr offers a continuous long record back to d 18 o stage 7 in general cd ca values in the downcore records are higher during interglacials and progressively increase as the interglacials proceed values peak around the times of optimum climate conditions and correlate with periods of increased opal wt correlations in the interval of overlap between the two records support the interpretation that variations in cd ca ratios in core 17940 2 are not an individual signal but can be replicated of special interest in this study is the tentative correlation between cd ca peaks in the scs record and the timing of iceberg discharge events heinrich events in the north atlantic mass accumulation rate mar of opal data from core 17950 2 indicate high surface productivity during glacial intervals corresponding to oxygen isotope stages 6 4 and 2 the increase in surface productivity during glacials from the northern scs is contemporaneous with an intensified winter monsoon as recorded by the terrestrial loess deposits the agreement with wind strength recorded in the loess plateau from mainland china supports the

changes in monsoon and ocean circulation and the vegetation cover of southwest sumatra through the last 83 000 years the record from marine core bar94 42 abstract we present the palynological record from deep sea core bar94 42 taken offshore of southwest sumatra in the indian ocean refinement of a previous age model for the core has been made using 7 additional radiocarbon ages and 29 additional oxygen isotope measurements these analyses have substantially improved the previously published chronology which has enabled revision of the results of sedimentological studies of the core the pollen and re interpreted biogenic and terrigeneous data were used to reconstruct monsoon circulation and vegetation of southwest sumatra over the last 83 000 years 83 kyr during marine isotope stage mis 5a southwest sumatra was covered by rainforest with open herbaceous swamps lining river courses and surrounding lakes the se component of the monsoon was stronger than the nw component resulting in a humid climate with a short dry season during mis 4 conditions were drier fire activity increased and the monsoon was generally weaker this latter pattern persisted until mis1 the vegetation was most open during mis 3 between 52 and 43 kyr identifying this phase as the driest of the last glacial an increase in montane trees from 52 kyr indicates the onset of cooler conditions which lasted until the transition to mis 1 at about 11 9 kyr after 43 kyr an everwet climate gradually developed as monsoonal circulation intensified and the se monsoon component became stronger during this time closed canopy rainforest became dominant regionally over southwest sumatra increased monsoonal activity during the early holocene resulted in increased precipitation river runoff sediment discharge and offshore sediment transport from the continental shelf

chemical weathering in luzon philippines from clay mineralogy and major element geochemistry of river sediments clay mineralogy and major element geochemistry of 35 surface sediment samples collected in 21 major to moderate rivers of luzon philippines are used to evaluate the present chemical weathering process the clay mineral assemblage consists mainly of smectite average 86 with minor kaolinite 9 and chlorite 5 and very scarce illite 1 and does not show strong island wide differences the major element results of both bulk and clay fraction sediments indicate that the formation of clay minerals is accompanied by leaching of ca and na first and of fe and mn thereafter during the chemical weathering process a low moderate chemical weathering degree of bulk sediments and a moderate intensive degree of clay fraction sediments are obtained in luzon rivers based on proxies of chemical index of alteration cia and smectite crystallinity it is suggested that the majority of andesitic basaltic volcanic and sedimentary rocks along with the tectonically active geological setting and sub tropical east asian monsoon climate are responsible for the predominance of smectite in the clay mineral assemblage

tracking the yellow dragons implications of china s largest dinosaur tracksite cretaceous of the zhucheng area shandong province china abstract surfaces with more than 2200 dinosaur footprints from the huanglonggou yellow dragon valley site near zhucheng in shandong province were excavated for scientific study and with a view to future development as an educational site suitable for further research and tourism although geographically close to spectacular and historically famous upper cretaceous sites yielding vast bone assemblages representing giant hadrosaurs and other dinosaurs from the wangshi group the tracksite is in the lower cretaceous yangjiazhuang formation equivalent in part to the longwangzhuang formation represents an entirely different dinosaurian fauna dominated by small theropods in contrast to a recent pre excavation study of a localized outcrop which identified only three theropod track morphotypes in a sample of 135 tracks the present study has identified at least 2000 additional tracks including those of sauropods and turtles it is therefore possible to present a more complete interpretation of the site based on the larger and more diverse track assemblage presently exposed three theropod track morphotypes are identified as grallatorid morphotypes a and b with the latter assigned to grallator yangi comb nov and corpulentapus lilasia tracks have been identified from at least 5 levels of which level 4 exhibits the vast majority in an excellent state of preservation other recent studies which we re evaluate suggest the tracks help define an ene wsw shoreline with the lake center to the sse in terms of number of tracks documented the huanglonggou site is one of the largest dinosaur tracksites in china or indeed in the world

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

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

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

climatic and tectonic controls on weathering in south china and indochina peninsula clay mineralogical and geochemical investigations from the pearl red and mekong drainage basins 1 results of clay mineralogy major element geochemistry and sr and nd isotopes in 93 argillaceous samples collected from drainage basins of the pearl red and mekong rivers reveal different degrees of chemical weathering in southeast asia despite similar climate conditions across these regions the kaolinite illite ratio illite chemistry index and illite crystallinity can be used as indicators of chemical weathering intensity these mineralogical proxies combined with the k2o na2o cao molar ratio chemical index of alteration cia and weathering trends observed from major element results indicate intensive silicate weathering in the pearl river basin moderate to intensive in the mekong river basin and moderate in the red river basin although a significant modification of epsilon nd 0 values in our riverine sediments during chemical weathering and transport is unlikely sr 87 sr 86 ratios are controlled by various states of chemical weathering of high sr minerals such as plagioclase rich in na and ca with a linear decrease trend from the pearl mekong to red river basins our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south china and indochina peninsula strong physical erosion caused by tectonic activities and river incision along the eastern margin of the tibetan plateau and along the red river fault system is responsible for high contents of primary minerals in the lowlands of red and mekong river basins

detrital fine grained sediment contribution from taiwan to the northern south china sea and its relation to regional ocean circulation article i nfo results of clay mineralogy in 140 samples collected in major rivers and lakes in southwestern taiwan and on the seafloor off taiwan in the northeastern south china sea scs combined with clay mineral records of the pearl river drainage basin rivers in luzon and the south china shelf and slope are used to semi quantitatively evaluate the detrital fine grained sediment contribution of taiwan to the northern scs the clay mineral assemblage of the taiwan sourced sediments consists dominantly of illite average 56 and chlorite 41 with very scarce kaolinite and smectite their respective distribution from the rivers and lakes to the seafloor off taiwan does not show obvious basin wide differences linear correlations of illite chemistry index with illite crystallinity and of illite crystallinity with kaolinite present two end members of provenances the pearl river and taiwan for the south china shelf and slope assuming that kaolinite in the northern scs is provided completely from the pearl river the contribution of taiwan in clay minerals is evaluated as 29 to the south china shelf and 23 to the south china slope respectively accordingly the contribution of the pearl river to the south china shelf and slope is 52 and 31 respectively the luzon arc accounts for the rest of clay mineral components for the northern scs mainly by providing smectite the bashi strait crossed branches of the southward deep north pacific deep water and the northward surface kuroshio current in the western pacific may transport taiwan sourced suspended sediments westwards to the northern scs

influence of the kuroshio current intrusion on holocene environmental transformation in the south china sea numerous studies have been conducted on the evolutionary history of the kuroshio current kc and other extensions however the history of the kc intrusion into the south china sea scs through the luzon strait has been little studied here we trace the holocene developmental history of the kc intrusion and its impact on environmental transformation in the northern scs this study involved a comprehensive analysis of planktonic foraminifera clay minerals and geochemical elements of core 05e306 sediments from the northeastern scs ams c 14 dates indicated that the sedimentation rate at the core site was most rapid 1000 cm ka before similar to 6 0 ka relatively rapid similar to 65 cm ka between 6 0 and 4 6 ka and slow similar to 24 cm ka since 4 6 ka the pulleniatina minimum event pme occurred between 4 6 and 2 7 ka together with high percentages of neogloboquadrina dutertrei and globorotalia menardii planktonic foraminifera indicated that the kc intrusion experienced three significant changes at 6 0 4 6 and 2 7 ka in turn depositional environments including input of terrigenous materials and development of biogenic materials similarly underwent three important transformations at 6 0 4 1 and 3 0 ka respectively abrupt changes in sedimentary records at the study core are contemporary with records from the tropical pacific during the holocene this indicates that development of the kc intrusion and its impact on depositional environments in the scs can be correlated with tropical factors from the low latitude oceans

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

clay mineral distribution in surface sediments of the northeastern south china sea and surrounding fluvial drainage basins source and transport clay mineralogy of surface samples throughout the northeastern south china sea scs and surrounding fluvial drainage basins has been investigated to reveal source and transport of detrital fine grained sediments three characteristic end members in clay mineral compositions were observed from three major provenances respectively major kaolinite and moderate illite and chlorite from the pearl river predominant illite and chlorite from taiwan and principal smectite from the luzon arc system the transport of four clay mineral species in the northeastern scs is influenced by various mechanisms smectite derived from the luzon arc system is transported mainly by surface current with significant influence of the kuroshio intrusion illite and chlorite from taiwan are mainly carried by deep water current while kaolinite from the pearl river is affected obviously by the westward guangdong coastal current and longshore current a westerly tongue shaped distribution of high contents of illite and chlorite mainly from taiwan on the eastern shelf may result from the westward guangdong coastal current during the winter the results suggest that clay mineral assemblages in the northeastern scs are mainly controlled by provenance supply and current transport and their downcore records do not bear contemporaneous paleoclimatic features the implication of clay minerals for proxies of the late quaternary east asian monsoon evolution is realized through both the provenance supply and current transport processes c 2010 elsevier b v all rights reserved

distal mud deposits associated with the pearl river over the northwestern continental shelf of the south china sea abstract continental shelf mud deposits represent an important archive of the holocene earth history such deposits are usually associated with large rivers that transport a large quantity of suspended sediment the pearl river has formed a distal shore parallel holocene mud deposit on the northwestern continental shelf of the south china sea investigations into its spatial distribution and evolutionary history are necessary for an improved understanding of such sedimentary systems seabed sediment sampling in situ tidal cycle measurements seismic survey and the associated data analyses reveal that the distal mud deposit associated with the pearl river occupies an area of approximately 8 87 10 3 km 2 with a modern deposition rate of 1 27 to 5 66 mm yr 1 evidence from sediment balance environmentally sensitive components sediment transport processes and regional shelf circulation patterns indicates that the pearl river is a major sediment source for the mud deposit this distal mud deposit represents an initial stage of its development the fining upward pattern and the negative skewness values in the layer are indicative of the pearl river influence and the 210 pb age is younger than 10 2 yr the main body of the holocene deposit of the region is not related directly to the modern pearl river sediment for most of the holocene periods the pearl river has been trapping the sediment to fill its extensive estuarine waters and therefore the formation of the distal mud is a recent event a regional characteristic is that the timing of the formation of distal muds associated with large rivers depends on the estuarine morphological evolution and the quantity of sediment discharge

holocene changes in biome size and tropical cyclone activity around the northern south china sea abstract the south china sea scs characterized by a large continental shelf is located at the edge of the asian monsoon domain in this study two marine sediment cores from the northern scs nscs continental slope were investigated to construct composite vegetation and precipitation isotopic composition records based on the 13c and d values of plant wax n alkanes throughout the holocene last 11 200 years i e 11 2 ka the composite 13cwax record indicates an overall predominance of c3 vegetation over the last 11 2 ka before 8 ka bp higher 13cwax values are attributed to preferential wax input from grassland and wetland biomes on the exposed continental shelf after the inundation of the shelf by eustatic sea level rise until ca 8 ka bp grassland and wetland biomes suffered a major size reduction and arboreal vegetation became better represented in the 13cwax record the composite temperature corrected dwax t record suggests that moisture source variability drove precipitation isotopic composition changes during the holocene lower dwax t values before 8 3 ka bp are interpreted as a larger moisture contribution by pacific ocean tropical cyclones whereas higher dwax t values after 8 5 ka bp are interpreted as a larger moisture contribution from the indian ocean summer monsoon higher incidence of tropical cyclones in the nscs during the early holocene was related to a temporary westward shift of the western pacific warm pool and enhanced insolation over the northern hemisphere both external and internal forcing mechanisms regulated moisture source changes in east asia during the holocene

major pleistocene stages in a carbon perspective the south china sea record and its global comparison 1 carbon isotope sequences at ocean drilling program site 1143 south china sea reveal a long term cyclicity of 500 kyr that is superimposed on the glacial cycles and is present in long 13c sequences from all oceans the quaternary 13c record is punctuated by four 13c maximum events 13cmax i which began in marine isotope stage mis 3 around 50 60 kyr ago 13cmax ii mis 13 0 47 0 53 ma 13cmax iii mis 27 29 0 97 1 04 ma and 13cmax vi mis 53 57 1 55 1 65 ma as the same cyclicity is also found in carbonate curves the 13cmax events must denote major reorganization in the carbon reservoir of the global ocean they also are associated with major changes in glacial cyclicity such as the mid brunhes event following 13cmax ii and the mid pleistocene revolution following 13cmax iii which in turn were associated with expansion of the ice sheets from a carbon perspective therefore the quaternary period has passed through three major stages and each appears to represent a further step in ice cap development

staged fine grained sediment supply from the himalayas to the bengal fan in response to climate change over the past 50 000 years abstract the bengal fan as the largest submarine fan in the world receives a large amount of sediments discharged from the himalayas through the ganges brahmaputra g b river system however previous studies of this system seldom focused on the role of channels which are widely developed in the bengal fan in sediment transportation over the last glacial cycle here we discuss the coupled sedimentary archive in two gravity cores along the active channel in the bengal fan our findings are based on grain size clay minerals and sr and nd isotope compositions of these two sediment cores end member modeling of grain size data reveals that the intermediate end member represents the flux of distal fluvial particles from the g b river system the fine end member denotes regional sediment supply of weathered volcanic materials especially from the eastern indian peninsula and the coarse end member probably reflects nearby terrigenous input aeolian input and or volcanic glass sediment provenance analysis based on clay minerals and sr and nd isotopes confirmed sediment supply from the g b river system which was characterized by high illite percentage high 87sr 86sr ratios and low end values especially during five stages 50 45 ka 42 37 ka 31 28 5 ka 24 20 ka and 14 9 ka during these stages heavy fine grained sediment supply from the g b river system was discharged into the study area under the influence of climate change rather than sea level fluctuation additionally emphasizing the importance of channels in the sediment transport process moreover we find a significant alteration of sediment sources at 26 ka which may be related to conversion of the deep water currents in the bay of bengal

holocene evolution in weathering and erosion patterns in the pearl river delta sediments in the pearl river delta have the potential to record the weathering response of this river basin to climate change since 9 5 ka most notably weakening of the asian monsoon since the early holocene approximate to 8 ka cores from the pearl river delta show a clear temporal evolution of weathering intensity as measured by k al k rb and clay mineralogy that shows deposition of less weathered sediment at a time of weakening monsoon rainfall in the early mid holocene 6 0 2 5 ka this may reflect an immediate response to a less humid climate or more likely reduced reworking of older deposits from river terraces as the monsoon weakened human settlement of the pearl river basin may have had a major impact on landscape and erosion as a result of the establishment of widespread agriculture after around 2 5 ka weathering intensity sharply increased despite limited change in the monsoon but at a time when anthropogenic pollutants e g cu zn and pb increased and when the flora of the basin changed sr 87 sr 86 covaries with these other proxies but is also partly influenced by the presence of carbonate the sediments in the modern pearl river are even more weathered than the youngest material from the delta cores we infer that the spread of farming into the pearl river basin around 2 7 ka was followed by a widespread reworking of old weathered soils after 2 5 ka and large scale disruption of the river system that was advanced by 2 0 ka

the influence of oceanographic processes on contourite features a multidisciplinary study of the northern south china sea abstract this study examines how multiscale oceanographic processes interact with the seafloor to influence the development of contourite features in northern part of the south china sea the multidisciplinary approach used in this study combines physical oceanographic monitoring numerical simulation multibeam echosounding seismic reflection profiling and sediment core interpretation the contourites detected and interpreted herein include depositional drifts and sediment waves erosional channels moats and furrows and mixed erosional and depositional features terraces and irregular depressions this study finds that climatic variation influences the intensity of quasi steady along slope regional water circulation which in turn influences the long term development of primary 10 100 km contourite depositional systems energetic but intermittent oceanographic processes such as eddies and internal waves generate smaller secondary features within the contourite depositional systems resulting in a complex local seafloor morphology westward to south westward migrating mesoscale eddies locally enhance regional water mass circulation and trigger sub mesoscale flows which can generate 1 10 km irregular depressions along their paths westward propagating internal solitary waves form sedimentary waves with the aid of numerical modelling results a sedimentary model is proposed to explain how oceanographic processes influence sedimentary processes and determine a hierarchy of associated feature formation this model can help advance understanding of how bottom currents influence sedimentary processes along continental margins and abyssal plains

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