low concentration of heavy metals in the yangtze estuarine sediments china a diluting setting abstract an examination of the spatial and temporal distribution of 17 major heavy metals i e fe zn ni mg co mn etc was made in the yangtze estuarine sediments revealed by a number of vibrocores taken from the different sediment zones including delta front prodelta and delta shelf transition the results obtained from the numerous core samples which were also measured for pb 210 and cs 137 show that 1 the silty clay comprising the prodelta facies serves as a depositional sink attracting high concentrations of heavy metals delivered from the river mouth 2 after being normalized to aluminum as a proxy for grain size most heavy metals presented in the prodelta facies have lower concentrations than in the other adjacent sediment zones 3 also after normalization concentrations of most heavy metals in the vibrocore sediments tend to increase up core and 4 sedimentation rates in the study area range from 2 0 to 6 0 cm a hence the vibrocores contain a sedimentary record of metal deposition covering more than 50 years it has previously been assumed that sediments off the river mouth were heavily polluted due to industrialization of the shanghai metropolitan area which peaked about 50 years ago however the low concentrations of heavy metals in the study area before and after normalization do not support this assumption the yangtze estuary is characterized largely by the tremendous runoff and unpolluted sediments derived from the upper drainage basin to constitute a unique diluted setting in which the dispersal behavior of heavy metals from the adjacent industrialized coast is influenced substantially as a result the heavy metals in the study area are obviously lower than those previously determined along the coast

detrital sediment supply in the southern okinawa trough and its relation to sea level and kuroshio dynamics during the late quaternary abstract during leg 195 of the ocean drilling program site 1202 was drilled in the subtropical northwestern pacific ocean beneath the kuroshio black current between northern taiwan and the ryukyu island arc on the northern flank of the i lan ridge at 1274 m water depth the upper 110 m of the site 1202 section composed of dark grey calcareous silty clay provide an expanded record of environmental changes during the last 28 kyr the sediments were deposited at high sedimentation rates between 3 0 and 5 0 m kyr and peak values of 9 0 m kyr between 15 1 and 11 2 ka bp variations in the modes and sources of detrital sediment input as inferred from sediment granulometry mineralogy and elemental xrf scanner data reflect changes in environmental boundary conditions related to sea level changes kuroshio variability and the climate driven modes of fluvial runoff the provenance data point to increased sediment supply from northwestern taiwan between 28 and 19 5 ka bp and from east china sources between 19 5 and 11 2 ka bp the change in provenance at 19 5 ka bp reflects increased fluvial runoff from the yangtze river and strong sediment reworking from the east china sea shelf in the course of increased humidity and postglacial sea level rise particularly after 15 1 ka bp the holocene was dominated by sediments that originated from rivers in northeastern taiwan for the pre holocene period prior to 11 2 ka bp low portions of sortable silt 63 10 m show that the kuroshio did not enter the okinawa trough because of low sea level in turn high proportions of sortable silt and sediment provenance from northeastern taiwan point to strong ocean circulation under the direct and persistent influence of the kuroshio during the holocene the reentrance of the kuroshio to the okinawa trough was heralded by two pulses in relative current strengthening at 11 2 and 9 5 ka bp as documented by stepwise increases in sortable silt in the lower holocene section from a global perspective environmental changes in the southern okinawa trough show affinities to climate change in the western pacific warm pool with little influence of climate teleconnections from the north atlantic realm otherwise seen in many other marine and terrestrial palaeoclimate records from southeastern asia

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

clay sized sediment provenance change in the northern okinawa trough since 22kyrbp and its paleoenvironmental implication provenances of clay sized terrigenous sediments and a comprehensive interpretation of their high resolution variations in the northern okinawa trough since the late last glaciation remain unclear especially in regard to the huanghe and taiwan derived matter grain size clay mineralogy typical elemental ratio oxygen isotope and ams c 14 dating of core pc 1 in the northern okinawa trough were investigated to trace clay sized sediment provenance and transport process and thus to recover their forcing mechanisms over the last 22 kyr variations in linear sedimentation rate grain size delta o 18 ti ca ratio and clay minerals can be clearly divided into three distinct intervals consistent with changes in sediment provenance that can be close related to sea level fluctuation evolution of the tsushima warm current as well as influence from the east asian monsoon climate evolution during the late last glaciation period interval 1 22 16 kyr bp when the tsushima warm current was absent in the east china sea the paleo huanghe mouth was situated close to the study area and thus the paleo huanghe could have played major role in sedimentation therein in interval 2 16 7 3 kyr bp global sea level rise led to gradually retreating of the paleo huanghe mouth and thus decreasing terrigenous sediment supply from it to the study area since 73 kyr bp interval 3 some clay minerals from taiwan might have been transported northward to the study area by the fully evolved tsushima warm current characterized by higher chlorite kaolinite ratios in contrast the decreasing influence of the huanghe derived sediments during the strengthening of the tsushima warm current periods was probably caused by the blocking effect of the tsushima warm current particularly chlorite kaolinite ratio and smectite content in the okinawa trough sediment might be good proxies for indicating the tsushima warm current related sedimentary environment c 2014 elsevier b v all rights reserved

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

mineralogical and geochemical investigations of sediment source region changes in the okinawa trough during the past 100 ka images core md012404 abstract we present a mineralogical and geochemical study of core md012404 retrieved from the central okinawa trough ot of the east china sea our studies reveal that the sediment sources of the core have been changed through time during the past 100 ka our mineralogical proxies indicate that the sediments source from the yangtze river correlates well sea level changes before 24 ka our ti al ratios otherwise indicate an increase of sediment supply from eastern taiwan after 26 ka the cooler climate of the last glacial maximum lgm 23 19 ka led to a reduction in fluvial sediments from the yangtze river however subsequent climate warming after 19 ka resulted in an abrupt increase in fluvial sediments after the lgm the kuroshio intrusion flow into the ot may have increased we also infer anomalous changes in eolian sources transported by winter monsoons during the lgm and at 80 ka based on an eolian mineralogical indicator feldspar we conclude that the sediment source of core md012404 is primarily of terrestrial origins but influenced by sea level changes and variations in the east asian monsoon

monsoon forcing hydrodynamics of the kuroshio current and tectonic effects on sedimentary carbon and sulfur cycling in the okinawa trough since 90 ka 1 monsoon forcing and hydrodynamic effects controlled carbon and sulfur biogeochemistry over the last 90 ka in a 43 m core from the okinawa trough ot total organic carbon toc contents co vary with summer insolation at 30 n suggesting monsoon forcing of primary productivity and organic carbon burial before the last glacial maximum lgm total sulfur ts contents varied concomitantly with toc however sea level rise and intensified kuroshio inflow during the holocene enhanced deepwater ventilation which resulted in ts depleted sediments with low degree of pyritization dop by contrast dop values were high during the previous highstand at 80 ka bp when sea level was similar to that in the holocene as well as during the lgm when deepwater circulation was relatively weak a topographic barrier is proposed to have sufficiently blocked the kuroshio current out of the ot during the previous sea level highstand which weakened deepwater ventilation and led to reducing diagenetic conditions tectonic rifting in the southern ot at 60 30 ka bp enabled the major change in hydrodynamics and sediment biogeochemistry

an analysis of storm induced landslides in colluvial soils overlying mudrock sequences southeastern ohio usa in late june 1998 a series of thunderstorms dropped 16 5 cm 6 5 in of rain in a 72 h period over southeastern ohio causing extensive flooding six deaths and 179 million dollars in property damage the storms also triggered more than 60 shallow landslides along a 64 km 40 mi stretch of interstate 77 between buffalo and marietta ohio almost all of the landslides were translational occurring along the contact between colluvial soils and the underlying bedrock shales claystones mudstones six sites were selected in the affected area for a detailed study of the shallow landslides at each site a record was made of the stratigraphy slope geometry number of landslides landslide dimensions hydrologic conditions and influence of vegetation on landslide distribution both colluvial soils and underlying bedrock were sampled for laboratory investigations which included determination of natural water content grain size distribution atterberg limits permeability slake durability and shear strength parameters data from laboratory tests were used to perform sensitivity and stability analyses with respect to varying slope angles strength parameters and thicknesses of saturated colluvial soil the results of the study indicate that the shallow landslides along interstate 77 occurred when the colluvial soils reached 90 to 100 saturation depending upon the slope angles

deep countercurrent beneath the kuroshio in the okinawa trough 1 the okinawa trough is geographically separated into the northern and southern parts by the kerama gap and the northern part is composed of the northern central and southern subbasins formed by bights of the continental slope previous observations have indicated that a deep countercurrent is present beneath the kuroshio on the continental slope in the northern okinawa trough however its persistence over time and its spatial structure over the entire basin have not been clarified to date the present study examines moored current meter data on the continental slope in the southern and central subbasins of the northern okinawa trough for november 2004 to november 2006 deep flows on the continental slope have a clear seasonality in the southern subbasin eddy motions due to kuroshio meanders are organized into a persistent countercurrent below the kuroshio in the winter spring period during this time high frequency kuroshio meanders with periods near 10 d are likely to diminish in the southern subbasin while low frequency kuroshio meanders with periods of 1 3 months tend to dominate in the northern subbasin in addition a high resolution ocean general circulation model is used to explore the deep flow field over the entire okinawa trough the model indicates that the deep flow field is stable in the southern okinawa trough over the year whereas it is unstable in the northern okinawa trough particularly in the winter spring period this results in a persistent countercurrent driven by cyclonic eddies on the continental slope in the northern okinawa trough

surface water evolution of the eastern east china sea during the last 36 000 years abstract planktic foraminifera have been studied in two high resolution cores raised from the continental slope of the eastern east china sea ecs to reconstruct the surface water history ams 14c dating on fifteen horizons revealed that the two cores kh82 4 14 and rn80 pc3 contain continuous records of the last 36 and 17 thousand cal years respectively thirty one planktic foraminiferal species which are commonly found in the present western north pacific and the ecs are recognized in down core samples three faunal phases iii ii and i distinguished by characteristic planktic foraminiferal assemblages suggest three major paleoenvironmental stages of the surface water of the eastern ecs since 36 000 yr b p 1 a stage influenced by coastal water from 36 000 to 19 500 yr b p 2 a stage also influenced by coastal water and extremely low salinity from 19 500 to 10 500 yr b p and 3 a stage controlled by the modern open sea water related to the kuroshio with both higher temperature and higher salinity since 10 5 8 5 thousand years b p oxygen isotope records of the planktic foraminiferal species g bulloides show that the three planktic foraminiferal faunal phases correspond to the last glacial deglacial and postglacial stages respectively the planktic foraminiferal assemblage during the deglacial stage which is represented by high percentages of g quinqueloba is quite different from those during the glacial and postglacial stages linked to a large amount of river discharge from the chinese continent a negative oxygen isotope excursion in g bulloides during the same period is highly correlated to the g quinqueloba anomaly also indicating a decrease in surface water salinity furthermore the sedimentation rate of core kh82 4 14 during 19 15 thousand years b p is much higher than the rates during the glacial and postglacial stages suggesting a great increase in the supply of terrigenous material related to an increased river and sediment discharge during the early deglaciation the coastal water influenced stage of the eastern ecs terminated gradually at 10 5 8 5 thousand years b p since the warm kuroshio current and its branches flowed in the eastern ecs as today the formation of the postglacial surface water circulation pattern in the eastern ecs was closely related to the flow patterns of the kuroshio current

late quarternary paleoceanographic record from the middle ryukyu trench slope northwest pacific abstract a piston core kt84 14 p1 from the middle ryukyu trench slope contains many paleoceanographic indicators of the past ca 150 000 years the age assignment is based on such criteria as the abundance change between gephyrocapsa ericsoni and emiliania huxleyi the datum of which is here substantiated by tephrochronology of an ash bed and the planktonic foraminiferal 18 o measurements the abundance change of florisphaera profunda which prefers the deepest habitat among calcareous nannoplankton species coincides with fluctuation of the planktonic foraminiferal 18 o the benthic foraminiferal fauna also changes in response to the latest quaternary climatic change particularly during the deglaciation period from the emiliani stages 6 to 5 as well as from 2 to 1 the presence of a counter current of the kuroshio current is inferred during the last interglacial period based upon the distributional pattern of the ata tuff in this and two other cores all recovered east of the southern ryukyu island arc the ash originating from the southern tip of kyushu should have been transported eastwards not southwards by the westerly winds therefore we infer that the ash was transported southwards by the counter current

two unique weathering regimes in the changjiang and huanghe drainage basins geochemical evidence from river sediments the present research reconstructs the histories of chemical weathering in the drainage basins of the changjiang and huanghe based on the chemical compositions of the river sediments the silicate weathering of the changjiang basin is strong and naand ca silicate minerals are considerably dissolved while other silicate minerals are less attacked in comparison the huanghe basin is characterized by very weak silicate weathering and the weathering degree corresponds well with that of the loess which is the predominant source of the huanghe sediment overall the changjiang and huanghe basins constitute a consistent weathering spectrum from the early to intermediate stage the similarity of chemical compositions between upper continental crust and the huanghe sediments as well as the low degree of chemical weathering in the huanghe basin imply that the river sediments can be considered to be the representative of ucc and are suitable for studying the evolution of continental crust our observations indicate that climate is the predominant factor controlling silicate weathering in both river basins while controls by source rocks and relief are subordinate highly erosive river basins such as the huanghe produce poorly weathered materials which casts doubt on the idea that strong physical weathering naturally contributes much to chemical weathering differences in silicate weathering processes between the changjiang and huanghe basins may provide more constraints in estimating atmospheric co2 budget in china d 2003 elsevier b v all rights reserved

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

a multiproxy lake record from inner mongolia displays a late holocene teleconnection between central asian and north atlantic climates in order to study how the holocene central asian climate is coupled to the global climate system a 4 24 m long lake core from western inner mongolia in china was studied using a multiproxy approach sedimentology and geochemical parameters such as gypsum and dolomite content presence of lakeshore sand changing to aeolian sand and changes in paleomagnetic properties bear witness to a trend toward a generally drier climate over the late holocene aridification is linked to the southward retreat of the northern boundary of the asian summer monsoon leaving central asia under the influence of the westerly belt the weakening of the asian summer monsoon in turn was caused by an orbitally driven decrease in summer insolation the weakening summer insolation also likely increased the intensity of the siberian high pressure system further promoting aridification of central asia on a shorter time scale the multiproxy record shows the climate to have been relatively dry during the medieval warm period ad 800 1100 with the ensuing humid environment at the end of this period gradually turning to become extremely dry ad 1100 1550 at the little ice age maximum switches in the north atlantic oscillation caused these changes through a teleconnection in the form of westerlies these westerlies provided most of central asia s moisture after the retreat of the asian summer monsoon the central asian climate therefore corresponds closely with late holocene european climate changes

observations of kuroshio flow variations in the east china sea 1 kuroshio velocity structure and transport in the east china sea ecs were investigated as part of a 23 month study using inverted echo sounders and acoustic doppler current profilers adcps along the regularly sampled pn line flow toward the northeast is concentrated near the continental shelf with the mean surface velocity maximum located 30 km offshore from the shelf break taken as the 170 m isobath there are two regions of southwestward flow a deep countercurrent over the continental slope beneath the kuroshio axis and a recirculation offshore which extends throughout the whole water column there is a bimodal distribution to the depth of maximum velocity with occurrence peaks at the surface and 210 dbar when the maximum velocity is located within the top 80 m of the water column it ranges between 0 36 m s and 2 02 m s when the maximum velocity is deeper than 80 m it ranges between 0 31 m s and 1 11 m s the 13 month mean net absolute transport of the kuroshio in the ecs is 18 5 0 8 sv standard deviation 4 0 sv the mean positive and negative portions of this net flow are 24 0 0 9 sv and 5 4 0 3 sv respectively

transgressive and highstand systems tracts and post glacial transgression the east china sea abstract the late pleistocene holocene depositional sequence on the shelf in the east china sea ecs is interpreted on the basis of the analyses of four sediment cores and high resolution seismic reflection sub bottom profiler records along a ne sw across shelf transect sedimentary strata deposited above a lowermost planar erosional surface that was formed during sea level fall of the last glacial are divided into two units along a ne sw across shelf transect changjiang okinawa the lower unit is characterized by seaward dipping tangential clinoforms with a thickness of 30 40 m at mid shelf depths and less than 30 m beneath the outer shelf prograding clinoforms are more obvious in mid shelf environments the upper unit is characterized by an upper transparent layer that is formed into ridge and swale topography the boundary between the upper and lower units is sharp and erosional surficial sediments taken by cores from the central ecs shelf are also divided into two facies a sandy facies consisting of sand or sandy gravel with moderately abundant molluscan shell fragments and a muddy facies comprising mud intercalated with thin sand layers the sandy facies is widely distributed on the middle to outer shelf seafloor and has a measured thickness of 30 cm up to several metres radiocarbon ages of molluscan shells in this sediment are less than approximately 10 ka bp except for ages from basal shell lag deposits which are 10 40 ka bp the muddy facies underlies the sandy facies and has radiocarbon ages of 2 7 2 9 ka bp previous work and 20 38 ka bp this study and tl ages of 27 50 ka bp previous work the boundary between these lithologic units is an erosional sharp contact the sandy and muddy facies are correlated with the upper and lower seismic units respectively the lower unit is characterized by prograding clinoforms and is interpreted to represent deltaic or nearshore tidal ridge sediments of the paleo changjiang river that were deposited during the last glacial lowstand of sea level as a lowstand systems tract the underlying erosional surface is interpreted to be a sequence boundary formed as a regressive marine erosional surface during the fall of sea level the erosional boundary between the lower and upper units is interpreted as a transgressive surface of erosion formed during the subsequent rise of sea level the upper unit has a modern sand ridge topography and is interpreted to represent offshore shelf sand ridges of the transgressive to highstand systems tract

spatial and temporal variations of the kuroshio east of taiwan 1982 2005 a numerical study 1 a 1 8 east asian marginal seas model nested to a larger domain north pacific ocean model is implemented over a span of 24 years from 1982 to 2005 to investigate the spatial and temporal variations of the kuroshio east of taiwan between 22 and 25 n the mean state and variability of the kuroshio such as the two paths observed in the trajectories of surface drifters southeast of taiwan and the branching of the kuroshio northeast of taiwan are well reproduced by the model southeast of taiwan the kuroshio is mostly in the top 300 m in the inshore path but extends to 600 m in the offshore path northeast of taiwan the kuroshio follows the shelf edge in the east china sea but may branch along a path south of the ryukyu islands the latter path often meanders southward and a significant portion of the kuroshio transport may be diverted to this path the kuroshio extends from the coast to 123 123 5 e between 22 and 25 n with currents reaching a depth of 1000 m at some latitudes the kuroshio transports averaged over five sections east of taiwan are 28 4 5 0 sv and 32 7 4 4 sv with and without the contribution from the countercurrent respectively

concepts of sediment deposition and accumulation applied to the continental shelf near the mouth of the yangtze river a fundamental understanding of how sedimentary strata form requires distinction between deposition and accumulation of particles deposition refers to the temporary emplacement of particles on the seabed accumulation is the net sum of many episodes of sediment deposition and removal the difference between rates of deposition and accumulation affects the ability of an environment to record sedimentary events radionuclide profiles of 234 th and 210 pb within the seabed can be used to determine 100 day deposition rates and 100 yr accumulation rates respectively on the continental shelf near the mouth of the yangtze river short term deposition rates are about 4 4 cm month whereas accumulation rates integrated over a century are an order of magnitude less about 5 4 cm yr

yangtze river of china historical analysis of discharge variability and sediment flux hydrological records covering a 100 year period from the upper middle and lower yangtze river were collected to examine the temporal and spatial distribution of discharge and sediment load in the drainage basin the yangtze discharge as expected increases from the upper drainage basin downstream only an estimated 50 of the discharge is derived from the upper yangtze with the rest being derived from the numerous tributaries of the middle and lower course however the distribution of sediment load along the yangtze is the reverse of that observed for discharge with most of the sediment being derived from the upper basin a dramatic reduction in sediment load by 0 8 108 tons year occurs in the middle yangtze because of a marked decrease in slope and the change to a meandering pattern from the upper yangtze rock sections considerable siltation also occurs in the middle yangtze drainage basin as the river cuts through a large interior dongting lake system sediment load in the lower yangtze while significantly less than that of the upper river is somewhat higher than the middle yangtze because of additional load contributed by adjacent tributaries a strong correlation exists between the discharge and sediment load along the yangtze drainage basin during the dry season as lower flows carry lower sediment concentration during the wet season a strong correlation is also present in the upper yangtze owing to the high flow velocity that suspends sand on the bed however a negative to poor correlation occurs in the middle and lower yangtze because the flow velocity in these reaches is unable to keep sand in suspension transporting only fine grained particles downstream hydrological data are treated for 30 years 1950 1980 when numerous dams were constructed in the upper yangtze drainage basin at yichang and hankou hydrological stations records revealed a decreasing trend in annual sediment load along with slightly reduced annual discharge at the same stations this can be interpreted as the result of water diversion primarily for agriculture sediment load at datong further downstream is quite stable and not influenced by slightly reduced discharge furthermore sediment concentration at the three hydrological stations increased which can be attributed to sediment loss in association with intensifying human activity especially in the upper drainage basin such as deforestation and construction of numerous dams mean monthly sediment load of these 30 years pulses about 2 months behind discharge implying dam released sediment transport along the entire river basin during the high water stage

clay mineralogy of pliocene pleistocene mudstones eastern taiwan combined effects of burial diagenesis and provenance unroofing pliocene pleistocene sedimentary rocks in the coastal range of eastern taiwan were deposited in a synorogenic collisional basin that developed immediately east of the growing taiwan fold and thrust belt during active arc continent collision unmetamorphosed mudstones from this stratigraphic sequence which were buried up to 6 km deep contain abundant detrital illite and chlorite derived from the adjacent metamorphic orogen a surprisingly small down section increase in percent illite layers in mixed layer illite smectite provides evidence for a low paleogeothermal gradient about 14 c km possibly combined with kinetic retardation of the illitization reaction resulting from the short duration of maximum burial illite crystallinity increases from the base to the top of the stratigraphic sequence opposite to the expected trend for burial metamorphism this reverse trend parallels lithic fragment detrital modes of sandstones from the same sequence and records progressive unroofing of the nearby prograde metamorphic terrane during collision related uplift and deformation

monsoon hydrography and productivity changes in the east china sea during the past 100 000 years okinawa trough evidence md012404 1 we analyzed the high resolution foraminifer isotope records total organic carbon toc and opal content from an okinawa trough core md012404 in order to estimate the monsoon hydrography and productivity changes in the east china sea ecs of the tropical western pacific over the past 100 000 years the variability shown in the records on orbital time scales indicates that high toc intervals coincide with the increases of boreal may september insolation driven by precession cycles 21 ka implying a strong connection to the variations in monsoons we also observed possibly nearly synchronous millennial scale changes of the ecs surface hydrography mainly driven by salinity changes but also by temperature effects and productivity coincident with monsoon events in the hulu dongge stalagmite isotope records we found that increased freshening and high productivity correlate with high monsoon intensity in interstadials this study suggests that the millennial scale changes in monsoon hydrography and productivity in the ecs are remarkable and persistent features over the past 100 000 years

holocene variability of the kuroshio current in the okinawa trough northwestern pacific ocean abstract cores 255 and b 3gc from the southern and northern okinawa trough respectively were studied for determining the variability of the kuroshio current on centennial scales during the holocene based on detailed ams 14 c dates stable isotope and planktonic foraminiferal distribution the main flow of the kuroshio current was inferred to re enter the okinawa trough at 7 3 calendar cal kyr bp leading to abrupt changes in sedimentation rate remarkably increased abundance of the kuroshio current indicator pulleniatina obliquiloculata increased sea surface temperature sst and depth of thermocline dot during 4 6 2 7 cal kyr bp the abundance of p obliquiloculata sharply decreased corresponding to a decreases in sst and dot implying that the influence of the kuroshio current weakened at that time possibly as a result of the intensified winter monsoon significantly the kuroshio current proxies e g the difference in sst between the southern and northern okinawa trough display periodicities of 1500 yr and 700 800 yr ascribed to the second harmonic of the 1500 yr cycle in oceanic thermohaline circulation during the holocene the holocene events at 0 6 1 7 3 3 4 6 5 9 8 1 9 4 cal kyr bp in the okinawa trough appear to be the most recent manifestation of the millennial scale climate cycle recorded in the north atlantic arabian sea marine sediment cores and greenland ice cores suggesting global climatic tele connections

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

paleoenvironmental change in the middle okinawa trough since the last deglaciation evidence from the sedimentation rate and planktonic foraminiferal record well dated high resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores a7 and e017 in the middle okinawa trough reveal strong and rapid millennial scale climate changes since similar to 18 to 17 thousand years before present kyr b p sedimentation rate shows a sudden drop at similar to 11 2 cal kyr b p due to a rapid rise of sea level after the younger dryas yd and consequently submergence of the large continental shelf on the east china sea ecs and the retreat of the estuary providing sediment to the basin during the last deglaciation the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly consistent with the timing of sea surface temperature sst variations determined from mg ca measurements of planktonic foraminifera from one of the two cores these fluctuations are coeval with climate variation recorded in the greenland ice cores and north atlantic sediments namely heinrich event 1 h1 bolling allerod b a and yd events at about 9 4 kyr b p a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the kuroshio current in the okinawa trough which was synchronous with a rapid sea level rise at 9 5 9 2 kyr b p in the ecs yellow sea ys and south china sea scs the abundance of planktonic foraminiferal species together with mg ca based sst exhibits millennial scale oscillations during the holocene with 7 cold events at about 1 7 2 3 4 6 6 2 7 3 8 2 9 6 10 6 cal kyr bp superimposed on a holocene warming trend this holocene trend together with centennial scale sst variations superimposed on the last deglacial trend suggests that both high and low latitude influences affected the climatology of the okinawa trough c 2006 elsevier b v all rights reserved

orbital and millennial scale variations in asian dust transport path to the japan sea abstract orbital and millennial scale variations in the asian monsoon and its probable association with the dansgaard oeschger d o cycles have been demonstrated by previous studies however the origin and nature of such variations are poorly understood the japan sea is located down wind of the arid areas of the eurasian continent and thus receives significant amounts of aeolian dust consequently the hemipelagic sediments of the japan sea are expected to record a continuous aeolian dust accumulation which may provide information about the past variations in asian monsoon grain size flux and provenance of aeolian dust in the sediments were examined using two sediment cores obtained from the northern and southern parts of the japan sea in order to understand the spatial variability of asian monsoon since the silt fraction of the detrital materials in hemipelagic sediments of the japan sea is composed predominantly of aeolian dust the grain size flux and provenance of the silt fraction were examined the taklimakan desert loess plateau and siberia northeast china areas were identified as possible source areas of aeolian dust in the sediments of the japan sea based on the electron spin resonance esr signal intensity and crystallinity of quartz moreover the relative contribution of aeolian dust from each source area was estimated based on the esr signal intensity and crystallinity of quartz aeolian dust fluxes from the two source areas at the southern site were then estimated grain size and flux of eolian dust at the northern site and fluxes of aeolian dust from two source areas at the southern site show orbital scale variations in harmony with the insolation change at 30 n in june these results indicate orbital scale changes in the extent of the arid area and or frequency of dust storms in the taklimakan desert loess plateau and siberia northeast china areas and suggest that southward northward shifts of the westerly jet axis occurred together with either intensified weakened winter monsoon decreased increased winter precipitation in the siberia northeast china area or southeastward northwestward shifts of summer monsoon limit during periods of smaller larger insolation at 30 n in june in addition to these orbital scale variations millennial scale variations possibly associated with the d o cycles are observed in the grain size record of aeolian dust at the two sites based on analogy with orbital scale variations these millennial scale variations are considered to reflect millennial scale changes in the position of the westerly jet axis together with the changes either in winter monsoon intensity winter precipitation or position of summer monsoon limit our results suggest n s oscillations in the westerly jet and summer monsoon limit and changes in the intensity of the winter monsoon on orbital and millennial timescales

upward decrease of organic c n ratios in the okinawa trough cores proxy for tracing the post glacial retreat of the continental shore line abstract six piston cores were collected along the nw se line in the okinawa trough close to the chinese continental shelf edge and dated by 23 ams 14 c measurements along with planktonic 18 o stratigraphy and an ash layer dated as 6 3 ka on a time scale to 19 ka the ratio of total organic carbon to total nitrogen concentration c n ratio displays gradual decreases toward the present and suggests the decrease of vascular plant fragment input to the trough from continental rivers this suggestion is confirmed by similar decreases of lignin phenol content and ratio of c 28 fatty acid to c 16 fatty acid content in core rn93 pc3 the gradual decrease of land plant fragment input is interpreted to be a consequence of the retreat of the continental coastline during the deglacial period

high resolution stratigraphic correlation of benthic oxygen isotopic records spanning the last 300 000 years abstract in order to compare the response of different oceanographic regions to global climate change very detailed stratigraphic techniques are required the global signal of ice volume changes recorded in the oxygen isotopic composition of foraminifera can provide the tool for developing the necessary high resolution stratigraphy in order to evaluate the resolution of a stratigraphy based on detailed isotopic records two techniques are used to correlate a set of benthic oxygen isotope records from seven piston cores taken in the north and south atlantic the indian and the equatorial and north pacific oceans the first technique was modified from the graphic correlation procedure of shaw 1964 this procedure requires the identification of isotopic events that are correlated from core to core detailed correlations for intervals of the cores between events are provided by a series of straight line segments connecting all common events the second technique developed by martinson et al 1982 uses inverse procedures to define a continuous non linear mapping function that correlates the isotopic records the mapping function maximizes the correlation coefficient between data sets being compared the techniques are independent in that they rely on different criteria for correlating the data series stratigraphic correlations obtained by these procedures are in excellent agreement the mean difference between the correlations is on the order of the sampling intervals of each core and when corrected for sedimentation rates suggests that benthic isotope records from the suite of seven cores can be correlated to a resolution of 2000 to 4000 yrs

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

paleoenvironmental changes in the northern area of the east china sea during the past 42 000 years a 33 65 m long images md982195 core with very high sedimentation rate ca 80 cm kyr retrieved from the northern part of the east china sea was analyzed at 10 cm intervals about 125 years for oxygen carbon isotope of globigerinoides ruber sensu stricto sea surface temperature sst from alkenones u37 k and principal component analysis of planktonic foraminiferal assemblage the general pattern of the 18o curve resembling the alkenone sst curve is similar to the standard open ocean oxygen isotope curve it reveals many light 18o peaks apparently corresponding to dansgaard oeschger d o cycles as observed in greenland ice cores for the last 42 ka the alkenone sst at the core top is 24 c which is close to the modern annual mean sst around the core site on the other hand sst during the last glacial maximum lgm was about 5 c lower than that in the present day alkenone derived sst does not correlate with the light negative 18o peaks corresponding to the d o cycles the oxygen isotope ratios for the surface waters based on oxygen isotopes of g ruber and alkenone ssts indicate approximately 1 0 increase on average during the lgm and many light peaks at the warm d o events this suggests that fresh water was supplied to the core site during these events the meandering of the westerlies during the cold and warm d o cycles would have caused an atmospheric tele connection between east asia and greenland the core was divided into four periods based on q mode factor analysis of the planktonic foraminiferal assemblage i e 1 a strong upwelling period from 42 to 24 ka indicated by abundant occurrence of globigerina bulloides 2 a cold and low salinity water mass period from 24 to 14 ka suggested by increase of neogloboquadrina pachyderma neogloboquadrina incompta and globigerina quinqueloba 3 a transitional period from cold to warm water masses from 14 to 8 ka as indicated by the increase of warm water species such as pulleniatina obliquiloculata and globigerinoides ruber and 4 the present day warm kuroshio current condition after 8 ka the kuroshio current flowed into the ecs since the last 42 ka and weakened during the last glacial maximum lgm due to the expansion of the coastal water in the northern part of the ecs

influence of intermediate water in the western okinawa trough by the outflow from the south china sea although the kuroshio and the south china sea scs waters flow in and out of the luzon strait near surface the scs water mainly flows out of the scs at mid depth between 350 and 1350 m in all seasons and years that we studied the eastward flowing scs intermediate water is blocked by and joins the northward flowing kuroshio at about 122 e thus the kuroshio intermediate water kiw is composed of the west philippine sea wps proper water on the east centered at 600 m depth because the ridge east of taiwan separating the okinawa trough from the wps is mostly shallower than 600 m the eastern portion of the kiw is largely blocked by the ridge and is forced to turn eastward this water does not enter the okinawa trough freely until it reaches a deep gap in the ryukyu ridge farther north subsequently forming the eastern portion of the intermediate water in the trough the western portion of the kiw is the mixed water of scs and wps the nutrient rich scs intermediate water centered at 500 m is less influenced by the ridge and is able to flow into the okinawa trough the scs intermediate water thus retains its signature in the southern and western okinawa trough upwells onto the east china sea shelf and becomes a major source of nutrients to the shelf water

what about the asthenosphere viscosity comment on sea level change glacial rebound and mantle viscosity for northern europe by k lambeck c smither and p johnston lambeck et al 1998a hereafter lsj present a thorough in my own studies fjeldskaar 1994 1997 i have shown that the best fitting models have a low viscosity asthenosphere study of the sea level change connected to the deglaciation of fennoscandia they establish a comprehensive observational based on fjeldskaar 1994 the thickness and viscosity of the asthenosphere are not precisely determined but are within database on crustal rebound for the whole of northern europe this database is used in a high resolution modelling of the the range shown in fig 1 it is clearly demonstrated that the asthenosphere has a thickness of less than 150 km a thicker rebound based on the observed deglaciation pattern a key result is an estimate of the effective elastic thickness of the asthenosphere shows significant discrepancies from the observed uplift data lithosphere and the viscosity structure of the mantle lsj give a brief overview of previous results on the mantle models similar to the one favoured by lsj were tested in fjeldskaar 1994 model no 14 it was pointed out that models rheology models established by a similar approach lsj s comment to models with a low viscosity asthenosphere and with a lower mantle viscosity of 2 0 1021 pa s or higher without a low viscosity asthenosphere are not viable options the various other previously published viscosity models is that the differences are attributable to a number of factors these reason is that the short wavelength components decay too slowly giving significant deviations in central parts of the uplift dome factors include the fact that the other studies used only a subset of the data and that some of them assumed the ice sheet to be this is clearly demonstrated in the theoretical present uplift pattern calculated with the rheology parameters of lsj given perfectly known a third factor is that none of the studies has examined the entire range of possible earth model parameters in lambeck et al 1998b the predicted present day uplift centre lies further to the west than the observed centre this would this immediately gives the reader the impression that lsj do not have similar shortcomings and that the final resulting not be the case if a low viscosity asthenosphere was used fjeldskaar 1994 fig 6 furthermore the rheology model of earth rheology model is better constrained than the previous studies however this is not the case lsj have ignored models lsj cannot produce the observed shoreline tilts fjeldskaar 1994 this is also demonstrated in lsj figs 28 and 29 with a low viscosity asthenosphere on this basis it is rather peculiar that they 1 criticize others for not having used the in conclusion lsj have not been able to come up with a model for the earth rheology that gives optimum fit to entire range of possible earth models and 2 give the reader the impression that models with a low viscosity asthenosphere the observed rebound because models with a low viscosity asthenosphere have not been considered the lsj rheology is are unrealistic

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

spatial and temporal variability of surface water in the kuroshio source region pacific ocean over the past 21 000 years evidence from planktonic foraminifera abstract the kuroshio current is the major western boundary current of the north pacific ocean and has had a large impact on surface water character and climate change in the northwestern pacific region the kuroshio current becomes a distinctive surface flow in the ryukyu arc region after diverging from the north equatorial current and passing through the okinawa trough therefore the ryukyu arc area can be called the kuroshio source region we reconstructed post 21 ka time space changes in surface water masses in the ryukyu arc region using 15 piston cores which were dated by planktonic 18 o stratigraphy and ams 14 c ages our analysis utilized spatial and temporal changes in planktonic foraminiferal assemblages which were classified into the kuroshio subtropical coastal and cold water groups on the basis of modern faunal distributions in the study region these results indicate that the kuroshio current and adjacent surface water masses experienced major changes during 1 the last glacial maximum lgm and 2 the so called pulleniatina minimum event pme from 4 500 to 3 000 yr bp the kuroshio lgm event corresponds to severe global cooling and is marked by decreases in planktonic 18 o values and estimated sea surface temperature sst with the dominance of the cold water group of planktonic foraminifera cooling within the kuroshio source region was enhanced during the lgm event because the kuroshio current was forced eastward due to the formation of a land bridge between taiwan and the southern ryukyu arc which prohibited its flow into the okinawa trough except for the severe reduction and disappearance of the pulleniatina group no clear cooling signal was identified during the pme based on 18 o values estimated sst values and variations in the composition of planktonic foraminiferal faunas the pme assemblages are marked by high abundances of neogloboquadrina dutertrei a distinctive kuroshio type species along with other species assigned to the coastal and central water groups subtle ecological differences exist between pulleniatina obliquiloculata and n dutertrei i e p obliquiloculata exhibits lower rates of reproduction under conditions of lower primary productivity in the central equatorial pacific ocean el nino like conditions in the equatorial pacific ocean result in lower rates of surface transport in the kuroshio current in turn this response triggers lower rates of primary productivity in central equatorial surface waters as well as in the upstream kuroshio source region ultimately resulting in a lower abundance of p obliquiloculata thus we interpret the pme as a possible proxy signal of el nino like conditions and enhancement of the el nino southern oscillation climate system after the pme in the tropical and sub tropical pacific ocean

latest pleistocene climate variation of the east asian monsoon from pollen records of two east china regions abstract pollen analyses performed on borehole cores from the present delta plains of the paleo changjiang incised valley and the paleo huanghe fluvial china lead to reconstruction of the latest pleistocene variation of the east asian monsoon and permit direct correlation with the vegetation history of eastern china from 13 000 to 11 670 cal yr bp the short term climatic deterioration stcd possibly corresponding to the younger dryas characterized by cold dry conditions caused by a strengthened winter monsoon and a weakened summer monsoon is reflected in the predominance of xerophytic herbaceous pollen e g artemisia input indicative of open grasslands during the subsequent early post glacial pg interval 11 670 11 270 cal yr bp pollen of conifer forest grassland taxa with thermophilous hardwood tree pollen indicate climatic warming cool humid conditions artemisia chenopodiaceae a c ratios reveal that climatic changes led to increased precipitation at the transition between the stcd and the early pg intervals moreover both the phytogeographic differences and the a c ratios indicate that during the stcd episode the humidity levels between the paleo changjiang incised valley and the paleo huanghe fluvial were different because they were located in different monsoonal zones finally the possible correspondence of the stcd episode to the yd cold event is believed to indicate that the yd is not confined to the circum north atlantic region but at minimum is a hemispheric climatic event

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