anthropogenic influences on changes in the sediment load of the yellow river china during the holocene using data on formation of the loess plateau of central china loess palaeosol sequences pollen analysis historical geography and long term experimentation on rates of soil erosion it is demonstrated that current serious erosion on the loess plateau is mainly due to human destruction of the natural vegetation and irrational land use these two modifications greatly reduce soil infiltration capacity and resistance of the soil to erosion the increase of soil erosion began ca 5000 bp at which time a hunting and pastoral life began to change gradually to a sedentary life centred around cultivation using the volume of holocene loessic sediments on the continental shelf of the bohai yellow and east china seas it is estimated that the present sediment load of the lower yellow river is at least three times greater than it was during the holocene although human induced soil erosion in the loess plateau began earlier it was not until the tang dynasty about 1000 bp that it began to increase rapidly ac

recent sediment accumulation and origin of shelf mud deposits in the yellow and east china seas abstract modern last 100 yr accumulation rates of shelf mud deposits in the yellow and east china seas were investigated using the distribution of excess 210pb 210pbex in sediment core samples compilation and merger of new and previously published data helped clarify sediment accumulation in these seas the estimated accumulation rates together with data of suspended sediment concentrations provided findings on the sediment budget origin and transport pathway of the mud deposits the overall accumulation distribution in the yellow and east china sea shelf revealed a general cross shelf decreasing trend along the sediment dispersal system away from the rivers except for the south sea ssm and southeastern yellow sea seysm mud patches found along the korean coast notably 210pbex activity profiles within the ssm and the seysm yielded a relatively high accumulation rate of 2 5 mm yr implying a sedimentation rate of 4 15 107 tons per year in this coastal zone such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge 6 20 106 tons yr from korean rivers suggesting an additional offshore source the distribution pattern of the well defined suspended plume clearly showed the possible transport and exchange of fine grained sediments between the ecs shelf and the coastal area of korea especially during winter such a high accumulation in korean coastal areas is attributable to the sediments supplied from the mud deposit of the ecs i e swcim with origins in chinese rivers therefore the korean coastal area may be an important sink for some of chinese river sediments being transported from the south by the yellow sea warm current

wind driven effects on the yellow sea warm current the yellow sea is a shallow basin writh an average depth of 44 m located between china and the korean peninsula one of the dominant ocean circulation features of the yellow sea is a warm wrater intrusion known as the yellow sea warm current this feature is present throughout the year but reaches its farthest northward extension in winter the circulation of the yellow east china and bohai seas was modeled using the princeton ocean model to better understand the dynamics of the yellow sea warm current the horizontal resolution of the model varies from 8 km in the yellow sea to 25 km in the east china sea twenty four sigma levels are used to define the vertical structure the model uses daily atmospheric forcing from the navy operational global atmospheric prediction system for 1993 open boundary conditions are applied at the taiwan strait the tsushima korea strait an area south of taiwan and the tokara strait with a closed boundary south of the ryukyu islands the model results are examined to determine the effect of the wind on the northward extension of the warm water intrusion using both water mass characteristics and northward velocity components sensitivity tests and spectrum analyses performed to study the influence of the wind on the yellow sea warm current show that winds modify the pathway and extent of the yellow sea warm current the current s origin however appears to be due to external forcing from the current systems developed in the east china sea

magnetic properties of muddy sediments on the northeastern continental shelves of china implication for provenance and transportation mud deposits are widespread in estuaries and on continental shelves and contain important information regarding interactions between terrestrial and coastal processes magnetic properties of muddy sediments from the northeastern continental shelves of china including shelves close to korean coasts were analyzed using bulk and size fractionated samples to elucidate muddy sediment sources and transport types concentration and granulometry of magnetic minerals were determined and all samples were found to be dominated by magnetite muddy sediments from the zhemin coast off the zhejiang and fujian coasts have the highest magnetic susceptibility and saturation isothermal remanent magnetization sirm values while those from the central and southeastern south yellow sea and the western korea strait have lower values reflecting lower magnetic mineral concentrations single domain ferrimagnetic grains dominate the magnetic particles in the central south yellow sea while superparamagnetic sp grains contribute significantly to the magnetic grains in the bohai sea sp and coarse multi domain md grains dominate magnetic grain assemblages in the north yellow sea and along the zhemin coast rock sediment particle size is not a major factor affecting the magnetic properties of the mud deposits in the study area rather terrigenous inputs and hydrodynamic transport processes primarily control the magnetic properties and sediments from the changjiang and huanghe rivers make the most significant contribution this observation applies to the whole study area although terrigeneous magnetic mineral concentrations decrease with increasing distance from the river mouths due to both sorting and mixing with other sediments with weak magnetic signatures bacterial magnetosomes also play a role in the central south yellow sea

late quaternary paleoenvironmental changes in the southeastern yellow sea korea abstract a 34 meter long ams 14 c dated sediment core was examined in order to reconstruct the paleoenvironmental changes that have taken place in the southeastern yellow sea during the last 16 600 years to achieve this we analyzed the geochemical compositions of organic matter the benthic foraminiferal assemblages and the stable isotopes of benthic foraminiferal tests the organic geochemical results show that terrigenous organic matter was dominant in the southeastern yellow sea between 16 600 and 4300 cal yr bp probably due to the influence of river runoff marine organic matters originating from surface primary productivity began increasing drastically after 4300 cal yr bp benthic foraminiferal assemblages reveal that brackish species were dominant before 3500 cal yr bp but the saline species dominated after this time the 18 o values of the benthic foraminifer cibicides lobatulus showed that a change from high amplitude to low amplitude fluctuations took place at 3500 cal yr bp these multi results indicate that the southeastern yellow sea changed from an estuarine to a modern marine shelf environment probably due to the inflow of the yellow sea warm current between 4300 and 3500 cal yr bp the time discrepancy of 800 years indicates that a modern marine shelf environment was not fully developed in the southeastern yellow sea until 3500 cal yr bp even though the sea began to be influenced by the oceanic current at 4300 cal yr bp

stratigraphy of late quaternary deposits using high resolution seismic profile in the southeastern yellow sea abstract high resolution chirp and sparker system seismic profiles were analyzed to investigate the sequence stratigraphy of late quaternary deposits in the southeastern yellow sea approximately 1560 line km data of chirp and sparker profiles were acquired together with 11 piston cores two previous long drill cores ysdp 102 and 103 were used for comparison with seismic data high resolution seismic profiles image the holocene mud deposits and the complex sedimentary structure in this area sequence analysis of high resolution seismic profiles reveals that the shelf deposits form a succession of high frequency five order sequences consisting of one depositional sequence developed during the late quaternary the depositional sequence includes five sedimentary units each with different seismic facies and geometry 1 incised channel fill and lowstand deltaic wedge unit sy1 2 sand ridges unit sy2 3 estuarine deltaic mud unit sy3 4 redeposited mud unit sy4 and 5 recent distal mud unit sy5 based on the interpretation of high resolution seismic records and correlation with the ysdp 102 103 long cores and piston cores late quaternary deposits in the southeastern yellow sea consists of a set of the lowstand unit sy1 early transgressive unit sy2 middle transgressive unit sy3 late transgressive unit sy4 and highstand systems tract unit sy5 formed since the last glacial period the rather unusual stratigraphic architecture including three systems tracts is largely controlled by the postglacial sea level changes and regionally circulation pattern associated with sediment erosion and redeposition the results of this study present firstly clear seismic evidence that the southeastern yellow sea mud belt seysm can be divided into three stratigraphic units units sy3 sy4 and sy5 bounded by distinct bounding surfaces

provenance discrimination of last deglacial and holocene sediments in the southwest of cheju island east china sea abstract the ultimate provenance of muddy sediment in the southwest of cheju island east china sea remains enigmatic thus far in this study rare earth elements rees were used to investigate sediment provenances of cores e03 6 e03 10 and e03 11 taken from the mud patch discrimination plots based on ree fractionation parameters and trace elements suggest that the sediments deposited during the last deglacial period 15 ka were derived predominantly from the paleo huanghe yellow river which might have delivered sediments directly into the northeastern east china sea during the lowstand of sea level the coarse grained sediments deposited at transgressive stage 15 6 ka were primarily sourced from the changjiang yangtze river and partly from the korean peninsula probably transported by tidal currents in comparison the clayey sediments deposited at highstand stage

man s influence on the erosion and transport of sediment by asian rivers the yellow river huanghe example during the holocene sediment input from the yellow river to the yellow sea and adjacent areas has amounted to about 3000 km 3 detailed records from river gauging stations over the past 70 yrs together with estimates based on earlier historic records suggest that the river has contributed 2300 km 3 of sediment during the last 2300 yrs an average discharge of 1 km 3 yr 1 x 10 9 t yr prior to extensive agricultural use of the loess plateau in northern china beginning about 200 bc therefore the river s load must have been about 0 1 km 3 yr an order of magnitude lower than that at present a broad delta 20 m below sea level suggests that early holocene rates were higher than the pre agricultural average and therefore that middle holocene loads were low

geochemical records of taiwan sourced sediments in the south china sea linked to holocene climate changes we present a multi proxy geochemical analysis of core kng5 retrieved from the northern south china sea slope spanning the last 13 0 ka bp to assess the response of weathering and erosion processes in the southwestern taiwan river basin to climate change a provenance analysis indicates that the core sediments were primarily derived from the southwestern taiwan river and can be used to reconstruct the erosion and or weathering history of this river basin the chemical index of alteration the plagioclase index of alteration rb sr al ti principle component 1 and k al combined with terrigenous mass accumulation rates and the proportion of clay exhibit sharp excursions from 12 0 to 5 5 ka peaking at 10 0 ka which suggests strong chemical weathering and physical erosion during the early mid holocene the period of the maximum summer monsoon abrupt falling weathering trends during 5 2 and 3 5 ka bp correlate with a weaker monsoon after 3 5 ka bp a stable lower weathering trend to the present day was evident indicating the deposition of less weathered sediments in the slope when the monsoon rainfall was weakening a good correlation between our proxy records of chemical weathering and variations of the monsoon intensity in south china emphasizes that variation in monsoon intensity is most likely the primary drive of the intensity of weathering and erosion in southwestern taiwan river sediments over the last 13 0 ka bp finally we concluded that geochemical parameters can be used as reliable proxies for climate variation on a millennial centennial time scale in such areas as taiwan where weathering limited regimes exist c 2015 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

holocene changes in detrital sediment supply to the eastern part of the central yellow sea and their forcing mechanisms in this study holocene changes in the riverine eolian and erosional supplies to the eastern part of the central yellow sea ys and their forcing mechanisms were determined on the basis of multiple mineralogical and geochemical indices of three age dated piston cores from the central yellow sea mud cysm deposition the core records of the indices including clay minerals rare earth element fractionation parameters and conservative trace elements revealed abrupt changes in the sediment sources especially similar to 9 0 and 4 8 ka the late last deglaciation and early holocene sediments units 3 and 4 similar to 14 1 to similar to 9 0 ka most likely originated from the paleo huanghe and the sea bed erosion together with some contribution from the paleo changjiang shoal sediments that extended northeastward into the ys after that period the dominant sediment source gradually changed to the changjiang during the middle holocene similar to 9 0 4 8 ka unit 2 while the supplies from huanghe and sea bed erosion to the south ys decreased in the last 4 8 ka unit 1 the cysm largely received changjiang derived sediments besides some clay sized particulates from the huanghe sea bed erosion and korea rivers might be transported to the cysm during unit 1 possible mechanisms behind such changes in the riverine and erosional sediment sources and contributions include position shifts of river mouths tidal stress evolutions shelf sea level fluctuations east asian monsoon climate changes and the development of the yswc and coastal circulation systems c 2015 elsevier ltd all rights reserved

holocene shifts in riverine fine grained sediment supply to the east china sea distal mud in response to climate change holocene changes in fine grained sediment supplies to the east china sea outer shelf were uncovered through the mineralogical and geochemical analysis of core b3 in the east china sea distal mud ecsdm based on the lithology accelerator mass spectrometry ams 14c dating and sea level change core b3 can be divided into two major units transgressive stage unit 1 12 5 6 8 kyr and highstand stage unit 2 6 8 0 kyr significant discrepancy of dolomite calcite ratio in the fine fractions 16 m of changjiang dolomite calcite 3 1 and huanghe dolomite calcite 1 22 sediments was used as a new uniqueness provenance tracer to distinguish these two riverine sources both of the dolomite calcite ratio and rare earth elements fractionation parameters in the fine grained sediment indicated distinct provenance shifts of core b3 during the holocene unit 1 of core 3 12 5 6 8 kyr mainly consists of the reworked and resuspension sediments of the east china sea shelf during the holocene transgression while unit 2 sediments 6 8 0 kyr are most likely sourced from the changjiang and huanghe moreover mixing curves of dolomite calcite ratio reveal that the ecsdm continuously received the changjiang sediment since 6 1 kyr with notable fluctuations whereas the huanghe sediment supply began in 6 8 kyr but abruptly stopped during 4 2 0 8 kyr and then appeared again since 0 8 kyr temporal changes of the changjiang and huanghe fine grained sediment contribution to the ecsdm are closely related to the formation of modern oceanic circulation system since 6 8 kyr shelf sea level change the 4 2 kyr climate event and the followed transition to cold and dry climate condition in the northeastern china global climate change as well as the artificial shift of lower huanghe course in ad 1128 in the war against invasion of the northern nomadic nation human activities

the 2013 marche offshore earthquakes new insights into the active tectonic setting of the outer northern apennines a seismic sequence offshore the marche region sheds new light on the active tectonic setting of the outer northern apennines revealing the existence of a previously unknown transcurrent seismogenic structure in contrast to the po plain area where vigorous seismicity testifies to active frontal thrusting the seismotectonic setting of the adriatic domain is characterized by the occurrence of active crustal strike slip faults dissecting the thrust belt as recent studies suggest that thrust faults represent the unique seismogenic sources characterizing the adriatic sector of the outer northern apennines our results pose new challenges to the identification of seismogenic structures in the region

detrital sediment fluxes from continents to oceans abstract detrital sediment is carried from land to the sea by three agents rivers glaciers and winds the shoreline is an arbitrary boundary within the detrital sediment transport system which extends from a site of origin across areas of temporary storage to a site of long term deposition the most important of the agents moving sediment across the land is river transport estimated to be in the order of 20 10 12 kg of sediment annually at present analysis of drainage basins indicates that relief and runoff are the most important factors in determining the sediment load of rivers the competence of rivers to transport sediment is governed by the volume flow gradient and the sediment load itself today most large rivers are fed by snowmelt in highland areas runoff from rainfall in the drainage basin and groundwater inflow along the river course water is lost to evaporation and groundwater infiltration river courses can often be divided into two segments a degradational section in which the gradient is relatively steep and little temporary storage of sediment takes place and an aggradational section where the gradient is sharply reduced through meandering and where large scale temporary sediment storage forms a flood plain lakes trap sediment inland and prevent its transport to the sea today many high and mid latitude rivers are interrupted by lakes of glacial origin there are also some large areas of internal drainage that deliver no sediment to the sea the load carried by rivers has been markedly altered by human activity and may have doubled over the past few thousand years only to be reduced in the past century by the widespread construction of dams the ancient use of fire in hunting and its subsequent use in clearing land has increased erosion extensive deforestation and cultivation processes have also increased the sediment supply dam construction is a relatively new factor and affects the sediment transport system by trapping sediment before it can reach the sea the resulting lower sediment supply from rivers is at least in part compensated by increased coastal erosion glacial erosion is difficult to estimate there is an ongoing controversy whether ice sheets are effective erosive agents or not estimates of the present global flux of glacial detritus range from 0 8 50 10 12 kg annually with the lower value most probable the dust flux is in the order of 0 5 to 0 9 10 12 kg annually but may vary greatly with time

fine aeolian quartz records in cheju island korea during the last 6500 years and pathway change of the westerlies over east asia 1 we investigated the fine component of aeolian dust deposited on a maar of cheju island korea during the last 6500 years to specify the variability of fine aeolian dust transported by the westerlies and its main controlling factor from the viewpoint of global atmospheric circulation as a proxy for the fine aeolian dust we used the fine component of chemically isolated aeolian quartz from bulk sediments the fine quartz flux fqf varies from 0 1 to 1 4 mg cm2 a with periodicities of 1620 810 400 325 and 210 years mainly providing information on the aridity change in the dust source region the taklimakan desert the median grain size of the fine quartz mfq representing the pathway of the dust transporting westerlies fluctuates between 2 and 6 m with significant cycles of 1030 390 280 220 and 195 years and shows similar variation pattern to the fqf on the basis of visual and spectral analyses the high low fqf and the large small mfq correspond to the warm cold atmospheric temperature record from greenland ice cores with significant coherent cycles indicating that the aridity in the dust source areas and the pathway of the westerlies in east asia were linked to climatic and atmospheric conditions in greenland through the pathway change of the westerlies during the middle to late holocene the pathway change of the westerlies mainly responsible for the variability of the fine aeolian dust in east asia was probably controlled by a climatic response to initial solar activity and resulting atmospheric reorganization in polar and high latitude regions

geochemical composition and provenance of muddy shelf deposits in the east china sea abstract textural and geochemical compositions of shelf sediments in the east china sea were measured and compared with those of riverine sediments the sediments were primarily composed of mud and sandy mud with an average mean grain size of 6 1 contents of caco3 varied from 3 9 to 11 5 averaging 7 6 elemental ratios of sc al zr ti cr th and nb co can be treated as powerful geochemical indices for sediment sources because these elements behave conservatively under marine environments and the ratios show large variations between different end members of potential sediment sources comparative analysis between elemental sc al zr ti cr th nb co ratios and sr isotopic 87sr 86sr ratios strongly suggest that sediments in the northern part of the east china sea primarily originate from the huanghe river whereas the muddy deposits in the western part of the east china sea originate from the changjiang river the difference in 87sr 86sr ratios between the two regions appears to indicate varied sources

geochemical constraints on the provenance of surface sediments of radial sand ridges off the jiangsu coastal zone east china abstract the jiang harbor centered radial sand ranges rsrs off the jiangsu coast are the largest in the yellow sea however the provenance of the rsrs remains controversial in this study we compare major and trace element geochemistry together with grain size and main mineral composition in carbonate free sediments from rsrs and potential sources onshore and offshore rsr sediments have different grain size characteristics onshore rsr sediments have mean grain sizes of 2 tio 2 li and partly in cs zn and some high field strength elements y zr nb pb and th while depleted in other elements offshore rsr sediments are complicated in geochemical compositions some of them have very high contents of high field strength elements and others are similar to onshore rsr sediments onshore and offshore rsr sediments have different controlling factors of geochemical compositions onshore rsr sediments are influenced by clay size minerals whereas offshore sediments are controlled by heavy minerals the identification of zr nb and ti zr vs k rb shows that onshore and offshore rsrs seem to have similar sources their differences in grain size are a result of hydrodynamic sorting the identification of elemental ratios reveals that sources of rsr sediments are variable in space and time and the inputs of the chinese rivers especially the old yellow river and the yangtze river are still dominant but the effect of the korean field cannot be neglected our findings also demonstrate the potential of elemental ratios such as zr nb and k rb as tracer pairs for provenance of sediments in the yellow sea

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

quantitative reconstruction of holocene sediment source variations in the yellow and northern east china seas and their forcings abstract sediment provenance in the yellow sea and northern east china seas yecss has long been a subject of interest but its quantification is still inconclusive here we present an improved al mg regression analysis by refining its methodological approach to strengthen quantification of sediment source to sink transports in the yecss with focus on its forcing mechanisms during the holocene our quantitative source estimates clearly depict a considerable supply of the chinese river cr sediments 50 to the southwestern korean coastal region and the korean river kr sediments 30 40 to the central yellow sea mud deposit which accounts for a good balance between the sediment supply and budget of the shelf deposit of particular note is an abrupt decline in the cr contributions around 124 e which indicates that the cr sediments do not directly reach the eastern part of the yellow sea blocked by a strong physical boundary further the observed variations in proportions between huanghe changjiang and korean river derived sediments over the last 15 kyr notably an abrupt increase of cr contribution since 7 ka followed by a sudden drop at 3 4 ka exhibit a good correspondence with other mineralogical proxy records these temporal provenance changes witnessed robust palaeoenvironmental signals which fit to major climatic and oceanographic events linked with sea level intensity of the kuroshio current inflow and the east asian monsoon this study improves understanding of what pathways and sinks exist within the yecs basin and how rates of sediment supply from adjacent rivers have changed over time

late quaternary transgressive and highstand systems tracts in the northern east china sea mid shelf abstract analysis of very high resolution 3 5 khz seismic profiles and sediment data from the northern east china sea mid shelf region reveals that the sedimentary sequence above the acoustic basement consists of five late quaternary sedimentary units comprising transgressive and highstand systems tracts formed after the last glacial maximum the transgressive systems tract includes four units 1 incised valley fill unit i 2 transgressive estuarine deltaic complex unit ii 3 transgressive sand sheet unit iii and 4 tidal sand ridge unit iv the lower two units units i and ii representing a paralic environment consist of sediment preserved from shoreface erosion the upper units units iii and iv corresponding to a marine environment consist of sediments produced through shoreface erosion during the holocene transgression a ravinement surface separates the lower and the upper units the highstand systems tract is composed of a distal mud patch unit v derived from the huanghe and changjiang rivers in china dispersal and deposition of this modern mud are largely controlled by the regional circulation pattern and sediment supply

liquefaction flow of submarine slopes under partially undrained conditions an effective stress approach the stability of submarine slopes is commonly assessed based on undrained soil response liquefaction flow may occur when pore pressure rise in soil elements under constant shear stress causes a reduction in effective stresses recent experimental studies have shown that a small net flow of water into an element results in additional pore pressure generation and further reduces its strength as a result soil elements can liquefy due to expansive volumetric strains that cannot be predicted by undrained analysis submarine deposits of the fraser river delta are known to contain high concentrations of methane gas tidal variations can cause unequal pore pressure generation with depth and time in these soils such changes reduce the effective stresses during low tides and may induce liquefaction flow of slopes due to partial drainage conditions an effective stress approach based on an elastic plastic stress strain relationship is presented to model liquefaction flow of sand a fully coupled analysis is carr

high resolution acoustic characteristics of epicontinental sea deposits central eastern yellow sea abstract large amounts 45390 line km of closely spaced 2 2 4 4 km high resolution subbottom profiles chirp 2 7 khz made it possible to identify detailed echo types and their distribution in an epicontinental shelf environment on the basis of seafloor morphology surface bedforms and subbottom acoustic characters 10 echo types were identified in the uppermost sedimentary sequence of the central eastern yellow sea flat seafloor with sharp bottom echoes echo types 1 1 1 2 and 1 3a transgressive sediment sheets or relict sands is widespread in the offshore area and underlain to the west by an acoustically transparent wedge echo type 1 3b highstand muds mounded seafloor with either smooth surface or superposed bedforms echo types 2 1 2 2 and 2 3 tidal ridges and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are dominant in the eastern nearshore area large scale mounds with continuous inclined internal reflectors echo type 2 4 giant mud bank occur in the southeastern nearshore area various scale eroded seafloor echo types 3 1 and 3 2 channels and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are present in the northern part of the sea the distribution pattern of echo types in the central eastern yellow sea reflects depositional processes and sediment dispersal systems during the holocene transgression and highstand period 1 development of tidal ridges and large scale dunes in response to strong tidal currents and waves in the eastern nearshore area 2 construction of transgressive to highstand mud bank huksan mud belt by deposition of muds derived from the keum river in the southeastern nearshore area 3 active erosion due to intensified currents in the northern part and 4 highstand mud deposition derived from the huanghe river on the transgressive sediment sheets in the offshore area

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

structure and eastward extension of the changjiang river plume in the east china sea 1 the hydrographic structure and offshore extension of freshwater plume discharged from the changjiang also known as the yangtze river in the northern east china sea were investigated by analyzing conductivity temperature depth ctd data and drifter trajectories collected during the summers of 1997 and 1998 from june to early september when southerly winds prevail the plume tends to move northeast in the chinese coastal area and then separates from the coastal zone to travel eastward over 400 km offshore across the western shelf of the northern east china sea during other seasons when northerly winds prevail the plume is confined to the chinese coast in the summer the plume in the midshelf confined to a thin surface layer 10 to 15 m thick extends eastward in the form of patches of low salinity water rather than spreading as a tongue shaped pattern from the changjiang mouth the eastward movement of patches in the western shelf is primarily due to upwelling favorable southerly winds upon reaching the vicinity of cheju do an island in the middle of northern east china sea the patches are advected to the korea tsushima strait by either the cheju warm current or a northward flowing mean current of the kuroshio branch current and then finally flow into the east japan sea

an exploratory model study of sediment transport sources and deposits in the bohai sea yellow sea and east china sea a regional ocean circulation model roms is used to simulate the chinese land derived sediment transport in the bohai sea yellow sea and east china sea byecs the model includes the effect of currents tides and waves on the sediment transport and is used to study the pathway and dynamic mechanisms of the fine grain sediment transport from the huanghe river yellow river the old huanghe delta and the changjiang river yangtze river in the byecs the seasonal variability of the sediment transport in the byecs and the sources of the yellow sea trough mud patch the mud patch southwest of cheju island the mud patch offshore from the zhejiang and fujian provinces and the okinawa trough mud patch are discussed the results show that the huanghe river sediment can be transported to the yellow sea trough but little makes it to the outer shelf while the old huanghe delta sediment is mainly transported to the yellow sea trough most of the sediment from the changjiang river mouth is carried to the mud patch off the coast of the zhejiang and fujian provinces but with part of this sediment also transported to the yellow sea trough the model shows that it is difficult to transport land derived sediment to the okinawa trough mud patch under normal conditions the model also has difficulty accounting for the deposition of sediment in the region to the southwest of cheju island and offshore from the zhejiang and fujian provinces an issue requiring further study

phosphorus distribution c n p ratios and δ13coc in arctic temperate and tropical coastal sediments tools for characterizing bulk sedimentary organic matter abstract onshore offshore trends in phosphorus p organic carbon oc and total nitrogen tn concentration p distribution elemental organic c n p ratios and stable carbon isotopic composition of oc 13 c oc of surficial sediments are presented from three river dominated coastal regimes the mackenzie river beaufort shelf in the canadian arctic the mississippi delta and louisiana shelf in the temperate gulf of mexico and the tropical amazon shelf these parameters measured in surficial sediments from the three sites are used to assess changes in the importance of terrestrial and marine organic matter sources to sediments as a function of distance from the locus of riverine discharge trends in elemental ratio data from the arctic transect and a portion of the gulf of mexico transects can be explained in terms of a two end member mixture of terrestrial and marine phytodetritus in the arctic transect covariation of organic c p ratios with 13 c oc is consistent with a two end member mixture of terrestrial and marine organic matter a similar relationship between c p ratios and 13 c oc is not evident in gulf of mexico or amazon shelf sediments at these sites the two end member model fails to explain the data adequately the most striking feature of the onshore offshore trends in elemental oc op and oc tn ratios is the occurrence of low ratios in sediments from deep water stations in the gulf of mexico and all stations on the amazon shelf resulting from p and n enrichments exceeding the redfield ratio for marine plankton three explanations are discussed to account for these low ratios 1 the dominance of refractory op and on compounds in the residuum of degraded organic matter 2 differential sorption of op and n compounds regardless of lability on the surfaces of the fine grained sediments characteristic of these sites and 3 a dominance of bacterial biomass or components derived from bacterial biomass elemental ratios and 13 c oc signatures indicate that differential sorption may be most important in the deep water gulf of mexico sites in contrast elemental ratios and 13 c oc on the amazon shelf are most consistent with a sedimentary organic matter pool dominated by bacterial biomass or derivative substances

evolution of late quaternary mud deposits and recent sediment budget in the southeastern yellow sea abstract analysis of high resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern yellow sea mud belt seysm along the southwestern korean peninsula the seysm up to 50 m thick over 250 km long and 20 55 km wide can be divided into three stratigraphic units a1 a2 and b from oldest to youngest unit a1 overlying the acoustic basement comprises the northern part of the seysm unit a2 comprises the southern part of the seysm much of unit a2 is exposed at the seafloor unit b completely covers unit a1 and pinches out southward 14c data suggest that evolution of each unit is closely related to the postglacial sea level changes unit a1 consists of estuarine deltaic or shallow water muds deposited during the early to middle stage of postglacial sea level rise ca 14 000 7000 yr b p unit a2 corresponds to relict muds deposited during the last deceleration stage of sea level rise ca 7000 3 500 yr b p unit b consists of shelf muds deposited during the recent sea level highstand ca very low background activities of 210pb of the surface sediment of unit a2 suggest that the present day sediment accumulation is negligible in the southern seysm on the other hand 210pb excess activity profiles in unit b yield an average sediment accumulation rate of 3 9 mm yr indicating active sediment accumulation in the northern seysm the annual sink 3 0 10 7 tons yr of fine grained sediment in unit b is about an order of magnitude greater than can be explained by the sediment input from the korean rivers alone we propose that reworking of unit a2 has provided large volumes of muds to unit b resulting in excessive sediment accumulation in the northern seysm much of unit a2 in turn is likely to have originated from erosion of unit a1 in the north this rather unique erosional depositional regime of the seysm is probably owing to the tidal and regional currents characteristic in the southeastern yellow sea

signatures of the late holocene neoglacial cold event and their marine terrestrial linkage in the northwestern pacific margin marine microfossil assemblages in core sediments from the northern east china sea ecs were investigated to understand late holocene paleoclimatic changes in the northwestern pacific margin we find a pronounced alternation of ocean condition during the late holocene characterized by an abrupt decrease in dinoflagellate cysts and kuroshio water species of planktonic foraminifera centered at ca 4000 2500 14c yr bp compilation and merger of new and previously published data show that this oceanic event corresponds with terrestrial cooling and dry episodes in the northern china the synchronicity between marine and terrestrial records is considered to be linked to a weakened kuroshio influence that is in coupled with intensified winter monsoon highlighting a significance of oceanic atmospheric dynamics in determining moisture and heat distribution over both oceanic and terrestrial domains superimposed on the late holocene the synchronicity between this particular climatic shift in the northwestern pacific and the neoglacial cold events in the northern high latitude regions is tentatively indicative of a global climate signal possibly associated with dynamics of the north pacific gyre system and the high latitude north atlantic thermohaline circulation and therefore positions of the mean latitude of the kuroshio extension

geochemistry of alkaline earth elements mg ca sr ba in the surface sediments of the yellow sea abstract the concentrations of alkaline earth elements were measured in the surface sediments of the yellow sea in an attempt to establish their sources from horizontal distributions the maximum concentrations of mg are found in the central yellow sea and its horizontal distribution is mainly controlled by quartz dilution the concentrations of ca and sr increase toward the southeastern yellow sea region the relatively higher enrichment of ca and sr in the southeastern yellow sea with sr ca ratios of 0 0053 suggests the presence of carbonates which are comprised of foraminifera and or coccoliths like deep sea carbonates on the other hand the concentrations of ba increase toward the northeastern yellow sea the higher ba enrichment in the sandy region of the northeastern yellow sea is associated with the presence of feldspar as evidenced by excellent correlations among ba mg al mg and sr ca ratios our results suggest that the transgressive and relict sand occurring in the eastern parts of the yellow sea contains al sr and ba enriched feldspars which originated from arprock river korea and thus can be distinguished from sand occurring in the western parts of the yellow sea which originated from yellow and yangtze rivers

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

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

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

ree partitioning in riverine sediments around the yellow sea and its importance in shelf sediment provenance abstract we sought to identify the characteristics and their controlling factors of rare earth element ree fractionation patterns in two chemically partitioned labile and residual fractions of korean kr and chinese riverine cr sediments we also investigated their sediment origins in the yellow sea based on ree signatures the results showed that the upper continental crust ucc normalized ree fractionation patterns were remarkably different for labile and residual fractions even between kr and cr sediments notably kr sediments in both residual and labile fractions exhibited a striking enrichment of light rees lrees unlike cr sediments with no obvious fractionation such lree enrichment is relatively much stronger in the coarse grained sandy sediments the peculiar lree enrichment in both fractions of kr sediments was preferentially linked to grater felsic granitic compositions compared with cr sediments that were close to those of the ucc granodiorite with relatively more mafic minerals consisting of a mixture of various rock types application of these ree signatures to the provenance of yellow sea sediments provides an important clue to the cause underlying the lack of correlation between the mud budget and the river discharge in korean coastal regions as well as the ultimate fate of cr sediments the ree fractionation signals especially in residual fractions may shed light on the major existing phases affecting ree fractionation as well as the origin of sediments in the yellow sea

late quaternary evolution of the yellow east china sea tidal regime and its impacts on sediments dispersal and seafloor morphology the evolution of a tidal current field in the yellow sea and east china sea yecs in response to the sea level rise since the last glacial maximum lgm was investigated using a two dimensional tidal model with special attention to changes in the sedimentary environment of the continental shelf region it was found that tidal currents on the yecs shelf have generally been semi diurnal throughout the post glacial stages with f ratio index of diurnal inequality and s2 m2 ratio index of spring neap cycle remaining similar to present on the other hand the spatial distribution of the tidal bottom stress associated with m2 and m4 tidal currents changed greatly during the transgression as the sea level rose two core regions showing high bottom stress values migrated shoreward from cheju island toward the west coast of korea and along the retreat path of the paleo changjiang estuary distribution of extremely intense tidal bottom stress suggested that intense tidal reworking may have occurred at sea levels from 90 to 45 m in the southeast yellow sea and at 75 to 60 m off the paleo changjiang estuary the latter of which agreed with the timing of a large terrigenous organic c flux observed on the shelf slope distribution of slightly weaker bottom stress indicated that the sand ridges off the changjiang estuary and in the southeast yellow sea also might have formed at during those periods on the other hand when the sea level was between 45 and 15 m the tidal bottom stress was generally not strong enough to invoke significant reworking even though the stress intensity may be stronger than present correlation with modern and relict sedimentary features suggested that the tidal process have played a significant role on the reworking and deposition of sediments on the yecs shelf

eolian quartz flux variations in cheju island korea during the last 6500 yr and a possible sun monsoon linkage we have obtained a high resolution sedimentary record covering the last 6500 yr from a maar in cheju island korea in order to reconstruct the history of variations in the eolian quartz flux eqf and hence asian dust the long term variation of eqf reveals three intervals a period of high eqf 4000 2000 cal yr b p and two periods of low eqf 6500 4000 cal yr b p and 2000 cal yr b p to present which have been affected by the east asian monsoon due to insolation change and the cold air activity in high latitudes correlated with polar high pressure systems this long term variation is superimposed by millennial and centennial scale fluctuations with periodicities of 1137 739 214 162 137 127 and 111 yr implying drier conditions in the source areas in china the detrended eqf record correlates visually and statistically cross spectral analysis with the atmospheric d 14 c record solar proxy the centennial scale variability in eqf may be affected

climatology and seasonal variability of ocean fronts in the east china yellow and bohai seas from satellite sst data front detection and declouding algorithms developed at the uri have been applied to the 12 year 1985 1996 pathfinder sst data set to produce the first comprehensive objectively derived year round climatology of ocean thermal fronts in the eastern china seas from 24 n to 41 n ten fronts have been distinguished namely kuroshio zhejiang fujian jiangsu shandong peninsula bohai sea seohan bay kyunggi bay western and eastern chejudo south korean coastal front and yangtze bank ring front the fronts are seasonally persistent they emerge and disappear in the same seasons of different years the frontal pattern remains fairly stable from one year to another whereas individual fronts display different modes of seasonal variability

origin and dispersal of recent clay minerals in the yellow sea abstract the clay minerals in the by considering the clay minerals supplied by rivers in china the old and present day huanghe river and korea the keum and yeongsan to the yellow sea continental shelf and the spatial variation in the distribution of clay minerals in the yellow sea this study indicates that the provenance of the cysm may be closely related to the old and present day huanghe river system whereas the clay minerals in the seysm seem to be largely associated with the keum and yeongsan rivers in addition smectite may be suggested as an important clay mineral in differentiating between cysm and seysm and understanding the sources of these two mud categories

sedimentary system response to the global sea level change in the east china seas since the last glacial maximum abstract the east china seas ecs is one of the world s largest continental shelf seas based on the combination of global sea level change and sequence stratigraphy we systematically investigated the evolution of sedimentary system in the ecs since the last glacial maximum lgm we have defined the transgressive boundary layer and constructed several sedimentary models of the ecs on the sequence stratigraphy and evolution of tidal sand ridges since the lgm and sediment source to sink during the high sea level the result shows that the ecs represent a typical case for large scale continental shelf response to the global sea level change three sedimentary system tracts had been formed in the ecs since the lgm first is the lowstand system tract corresponding to the late of last glaciation and lgm 23 15 4 cal kyr b p the progressive wedge occurred along the okinawa trough slope and the paleo coastal zone pcz along the continental shelf edge second is the transgressive system tract corresponding to the last deglaciation 15 4 7 cal kyr b p a large scale transgressive boundary layer and tidal sand ridges were formed in this stage third is the highstand system tract corresponding to the high sea level since 7 cal kyr b p the eddy mud coastal current mud present tidal sand ridge delta tidal flat and beach have been accumulating since then the global sea level change after lgm can be divided into seven phases of which four rapidly rising phases rrp i ii iii iv and three slowly rising phases srp i ii iii are distinguished the tidal sand ridges were formed in the srp and transgressive boundary layer in the rrp the tidal sand ridges can be divided into three types including radicalized channel and emanative the modern circulation current system of the ecs had been built in the end of the last deglaciation the effect of sediment source to sink in the ecs is closely correlative to the current system driven by the interaction of the east asian monsoon and kuroshio the major sediment source is from the river discharge of the huanghe and changjiang river and coastal resuspension the muddy sediment in the eddy and coastal current which cover the tidal sand ridges and transgressive boundary layer is a major sediment sink in the modern ecs

sedimentary environment and formation mechanism of the mud deposit in the central south yellow sea during the past 40kyr abstract sedimentary environment and formation mechanism of the mud deposit in the central south yellow sea of china during the last 40 kyr are studied based on the analysis of particle size sediment density chemical features magnetic properties and ams 14 c ages of a new core ys01a together with other available core data the results show that there exist four sedimentary sections during this 40 kyr period including two marine sections a and c and two terrestrial intertidal sections b and d sedimentary indexes of section d which were formed before 40 kyr show that strong weathering and erosion occurred in this section in contrast sedimentary environment of section b was wetter and warmer and weathering and erosion were not as strong as in section d marine deposits in both sections a and c indicated the effects of sea level rise and section c was deposited when the climate was much wetter than in section a variations of climate and local hydrodynamics created different sediment features of two marine sections from the estimated river discharges of the huanghe changjiang and relevant korean rivers and calculation of mud deposit volumes of section a during the past 9 7 kyr it is found that the sediment inputs from these river sources can only account for about 48 of sediments in the two mud deposits of the central and southeastern south yellow sea the other main source of sediments is identified to be the seabed erosion resuspension and redeposition from the yellow sea and to a lesser extent from the biogenesis and diagenesis it provides a unique opportunity of understanding the formation and source of mud deposits by comparing the sedimentary properties of sections a and c in core ys01a it is found that formation of mud deposits is not related directly to the yellow sea warm current which only changed the sediment properties of mud deposits in section a since it formed from holocene by bringing a large amount of organic mass and finer particles however cold water mass developed in this area is important as it helped to trap more and finer particles in the two marine sections upwelling usually occurs around 50 m bathymetry which is at the juncture of two opposite water currents and has induced the thickest sediment layer this study also confirmed that formation of the mud deposit in the central south yellow sea is caused mainly by the tidal currents on the continental shelves

multielement geochemistry of offshore sediments in the southeastern yellow sea and implications for sediment origin and dispersal abstract in total 116 surface sediments were collected from an offshore area of the southeastern yellow sea including a large mud belt southeastern yellow sea mud seysm and analyzed for grain size and geochemical composition organic carbon and 42 elements principal component analysis revealed that elemental compositions of the offshore sediments were mostly controlled by common aluminosilicate clay minerals and quartz most elements heavy minerals hf zr u th rare earth elements rees biogenic calcium carbonates ca sr feldspar and mica k ba pb and mn oxides mn oxide coatings on sand grains notably total ree concentrations may be associated with heavy minerals possibly zircon and monazite especially in silty grains even though heavy ree hrees concentrations are more strongly controlled by clay minerals in muddy sediments the diagnostic discrimination plots of geochemical compositions e g fe vs al mg vs al light ree vs hree and la lu ucc vs la y ucc suggested that the offshore sediments especially in seysm deposits were composed of a mixture of korean river derived silts and chinese river derived clays this demonstrated that chinese river sediments especially clay particles largely contributed to the formation of the giant mud belt in the korean coastal area furthermore the observed geochemical end members provide new markers of sediment provenance which can be used to track dispersal patterns and sediment limits from chinese and or korean rivers