sediment provenance and paleoenvironmental change in the ulleung basin of the east japan sea during the last 21 kyr despite the well reconstructed paleoceanography of the late quaternary deposits in the east japan sea es provenances of terrigenous sediments and a comprehensive interpretation of their variations since the last glacial maximum remain unclear especially in regard to the mainland china and taiwan derived matter grain size conservative trace elements rare earth elements rees nd isotope and clay mineralogy of core sediments from the ulleung basin of the es were investigated for better understanding of detrital sediment provenance and transport process and then their forcing mechanisms over the last 21 kyr geochemical mineralogical multi indices in this study showed notable three phase changes in sediment provenance which can be closely related to sea level fluctuation development of the tsushima warm current as well as intermittent influence from the east asian summer monsoon climate evolution during unit 1 21 1 8 4 kyr bp when the tsushima warm current was absent in the es the paleo changjiang and the paleo huanghe mouth might be situated close to the study area and thus mainland china could have played major role in the southwestern ulleung basin sedimentation in particular the formation of rhythmic dark colored alternation in unit 1 is possibly attributable to the pulse of paleo huanghe discharge associated with centurial to millennial scale variability in the east asian summer monsoon in unit 2 8 4 7 2 kyr bp these river mouths gradually retreated to their present positions with global sea level rise leading to decreasing terrigenous sediment supply from mainland china to the study area since 7 2 kyr bp unit 3 sedimentation in the ulleung basin should still be mainly derived from mainland china meanwhile increasing chlorite kaolinite ratio but decreasing epsilon nd value revealed that terrigenous matter from taiwan might have been limitedly transported northward to the study area by the fully evolved tsushima warm current a prominent decline in chlorite kaolinite ratio together with contrast change on epsilon nd value centered at around 2 9 kyr bp 3 3 2 4 kyr bp may have been caused by the tsushima warm current suppression possibly related to the pulleniatina minimum event popularly found in the study area and nearby seas c 2014 elsevier ltd all rights reserved

how paleosols influence groundwater flow and arsenic pollution a model from the bengal basin and its worldwide implication in the bengal basin the land surface exposed during the last lowstand of sea level around 20 ka and now buried by holocene sediment is capped by an effectively impermeable clay paleosol that we term the last glacial maximum paleosol lgmp the paleosol strongly affects groundwater flow and controls the location of arsenic pollution in the shallow aquifers of our study site in southern west bengal and by implication in shallow aquifers across the bengal basin and as polluted deltaic aquifers worldwide the presence of the lgmp defines paleointerfluvial areas it is absent from paleochannel areas a paleosol model of pollution proposed here predicts that groundwater in paleochannels is polluted by arsenic while that beneath paleointerfluvial areas is not paleointerfluvial aquifers are unpolluted because they are protected by the lgmp from downward migration of arsenic and from downward migration of organic matter that drives as pollution via reductive dissolution of as bearing iron oxyhydroxides horizontal groundwater flow carries arsenic from paleochannels toward paleointerfluvial aquifers in which sorption of arsenic minimizes the risk of pollution

late quaternary environmental changes in the pearl river mouth region china abstract this study presents findings concerning late quaternary environmental changes in the pearl river mouth region china based on the study of over 300 boreholes out of these 35 boreholes are selected for the reconstruction of transects across the deltaic plain and estuary 39 radiocarbon dates obtained from these boreholes are used to help define the chronology of stratigraphic units present including two terrestrial units t1 and t2 and two marine units m1 and m2 diatom assemblages are studied in 6 boreholes revealing similarities and differences between the two marine units before the area was inundated by the last interglacial sea mis 5 an older terrestrial unit of sand and gravel t2 was laid down in a number of palaeo valleys during the last interglacial period an older marine unit of silt and clay m2 was laid down which was subsequently subaerially exposed when sea level regressed during the last glacial period mis 4 2 causing the uppermost section to be weathered during the same period a younger terrestrial unit of sand and gravel t1 was deposited along palaeo river channels around the early holocene before 8 2 cal ka bp the postglacial rise in sea level initiated a new phase of sedimentation in the outer part of the estuary characterised by the high percentages of marine diatoms in the sediments in the early holocene strong monsoon freshwater discharge resulted in sedimentation of a fine sand layer in the inner part of the estuary after 8 2 cal ka bp rapid rises in sea level caused widespread marine inundation and sedimentation the diatom data suggest that the relative sea level associated with the m2 and m1 units were both at similar levels because the m2 unit is typically recorded at altitudes of 15 m and 20 m below the present sea level this is likely to be a result of long term subsidence although numerical dating of the pre m1 units has not been made in the present study the chronology of these units can be inferred from uranium series ages and optically stimulated luminescence dating obtained from the adjacent coastal waters of hong kong the t1 unit has yielded ages of about 30 0 cal ka bp while the m2 unit has yielded ages about 130 0 cal ka bp confirming their mis 4 2 and mis 5 ages respectively

sedimentary facies and evolution in the qiantang river incised valley eastern china abstract this paper deals with the sedimentary facies and evolution of the qiantang river qr estuary and the characteristics and formation of the incised valley sequences and the related shallow biogenic gas reservoir on the basis of analysis of over 500 cores the result shows that since the last glaciation the late quaternary formation of the qr estuary area underwent three stages 1 deep cutting stage 2 rapid filling stage and 3 burial stage the fall of global sea level during the last glacial maximum enhanced the fluvial gradient and river cutting resulting in the formation of the large scale qr and taihu incised valleys with the interfluve being exposed to air on both flanks of the incised valley fluvial terraces at the elevations are present near the present qr estuarine mouth corresponding to 60 70 90 100 and 115 125 m burial depths the valleys were filled rapidly with fluvial sediments during the post glacial period with the rise of sea level the river mouth migrated to landward and backwater and retrogressive aggradation was enhanced the qr and taihu incised valleys are associated with an early filling and transgressive channel infilling sequence formation and a late filling and transgressive floodplain estuary formation subsequently the qr valley was buried under estuarine marine and estuarine sand bar sediments from bottom to top the incised valley successions can be grouped into four sedimentary facies river channel floodplain estuary estuary shallow marine and estuary sand bar the thickness of the river channel infilling deposits is controlled mainly by base level rising backwater retrogressive aggradation and neotectonism further localized thickening took place where deeper scour pools were present in the incised valley or fluvial terraces were formed during the fall of elative sea level during the deposition of the floodplain estuary facies the conditions of sea level rise tidal regime sediment supply and accommodation space were suitable for the development of a tidal ridge system the sand lenses associated with this facies may represent a tidal ridge system in the incised valley at the later stage when the estuarine sand bars were formed the sedimentary conditions were no longer favourable resulting in absence of sand ridge deposits biogenic gas is stored in the floodplain estuary sand lenses of the incised valleys the changjiang river provides the major sediment supply for the qr estuary sand bar and the qr carried sediments constitute only a small portion of the deposits

evidence for sea level and monsoonally driven variations in terrigenous input to the northern east china sea during the last 24 3 ka geochemical and sedimentological analyses of core pc 1 recovered from the northern east china sea ecs provide insights into variations in terrigenous input associated with sea level and climate changes over the past 24 3 ka based on high resolution multiproxy records our results suggest that the competing processes of sea level and monsoonally driven precipitation determined terrigenous input to the northern ecs dominance of terrigenous material along with relatively light globigerinoides ruber 18o indicates that the last glacial maximum lgm lowstand of sea level has occurred during the period 21 5 19 6 ka not suggesting an early slow rise but supporting the conventional lgm age of 21 ka this lgm lowstand was terminated by the rapid sea level rise of 19 ka meltwater pulse mwp which is well expressed by the nearly synchronous decreases in both terrigenous detritus and mean grain size from 19 6 to 18 9 ka mwp 1a is clearly marked in our records by a sharp reduction in terrigenous input and pronounced maxima of g ruber 18o at 15 3 14 8 ka given the considerable age uncertainties of deglacial marine radiocarbon samples a slightly increasing input of terrigenous matter is noted after 13 4 ka potentially pointing to a sea level fall following the inter allerod cooling period which was seldom reported previously although mwp 1b did not leave robust signatures in terrigenous input it is explicitly captured by the heavy 18o of g ruber and decline in mean grain size at 11 5 10 9 ka mwp 1c probably occurred in a broad millennial interval with multiple peaks which are robustly marked by the abrupt variations in terrigenous input and marine organic matter at 9 7 9 3 and 9 1 ka respectively during the late holocene the effect of continuously weakening monsoon precipitation overwhelmed that of stable sea level resulting in a uniform increase in the proportion of marine derived organic matter after 5 5 ka

pollen and non pollen palynomorph analyses of upper holocene sediments from dianshan yangtze coastal lowlands china hydrology vegetation history and human activity abstract the coastal deltaic plain of the yangtze river between taihu lake tai and shanghai in eastern china has been the scene of human settlement and agriculture since the early neolithic becoming increasingly intensive in the upper holocene when delta accretion and the establishment of a stable hydrological regime of freshwater lakes and wetlands allowed the development of extensive agriculture and complex society in late prehistoric and dynastic times during this period the area was significantly affected by changes in sea level climate and vegetation resulting in a dynamic and complex environmental history however little research has concentrated on environmental change and human impacts during the last few millennia this study focuses on this late period presenting the results of integrated sedimentary microfossil and radiocarbon analyses from a core near the eastern margin of lake dianshan to the east of taihu after the withdrawal of intertidal conditions and the conversion to freshwater lake at the core site about 2600 cal yr bp pollen and algal spore data show that increased sedimentation gradually reduced freshwater depth until a surface peat formed ca 1500 cal yr bp this also dates the start of a switch in woodlands from sub tropical and warm temperate trees to a mainly cool temperate and coniferous tree flora under climatic cooling and human impact after this time water depths at the site increased greatly partly due to climate change and flooding but also because of the establishment of deepwater paddy agriculture microcharcoal and pollen data show that a major episode of human impact using fire with deforestation and rice cultivation occurred between ca 1500 and 1200 cal yr bp these dates suggest it is one of the latest examples of flooded field paddy cultivation before more intensive agricultural techniques were adopted in the area after ca 800 cal yr bp

paleosols below the ames marine unit upper pennsylvanian conemaugh group in the appalachian basin u s a variability on an ancient depositional landscape abstract a vertisol like paleosol complex ranging from 3 to 10 m thick is developed below the ames marine interval conemaugh group upper pennsylvanian in the appalachian basin eastern ohio western pennsylvania west virginia and adjacent parts of maryland and kentucky sub ames mudstones contain the following pedogenic features very large slickensides microsparitic calcite nodules nodules or coatings of radial calcite spar preserved soil microstructure soil compatible birefringence fabrics and prominent mottling commonly restricted to the lower part of the paleosolum soil formation comprised 1 long term pedogenesis in alluvial and probably lacustrine sediments and 2 rapid development of histosols harlem coal as much as 8 m thick encouraged by the approaching am s transgression pedogenic carbonates in the sub ames interval at three localities yielded 18o values ranging from 6 18 to 1 21 pdb average 4 02 pdb s d 1 42 and 13c values ranging 9 17 to 6 72 pdb average 8 12 pdb s d 0 59 a inary plot of these values suggests mixing probably seasonal of evaporative and meteoric effects on isotope partitioning the stratigraphy of the ames harlem coal interval the regional distribution and thickness of the harlem coal and features of the sub ames paleosol show that the pre ames landscape had significant local relief in the form of shallow paleovalleys with broad interfluves along the western to northern margin of the appalachian basin ohio southwestern pennsylvania the stratigraphic relationships of sub ames paleosols the harlem coal ames marine unit interval and the ames marine unit itself are compatible with a significant effect of eustatic sea level rise in this area greater regional tectonic subsidence was probably the strongest control on sub ames sedimenta ion and pedogenesis along the eastern to southern margin south central pennsylvania west virginia northeasternmost kentucky where there appears to have been very little relief the morphology and stable isotope geochemistry of sub ames paleosols are compatible with seasonally wet dry climates probably with moderate 500 1000 mm annual rainfall

shallow gas in the holocene mud wedge along the inner east china sea shelf abstract high resolution seismic surveys were carried out in the inner shelf of the east china sea to investigate the distribution of shallow gas in holocene sediments shallow gas is distributed extensively in the holocene strata of the shelf which is dominated by the yangtze river organic rich fine grain sediments deposited throughout the holocene are essential for gas generation and accumulation the thickness of the holocene sediment is the main controlling factor determining the distribution of shallow gas gas seepages were found mostly at a water depth up to 20 m where sediment erosion mainly occurs coincidence between shallow gas seepage and high methane concentration in the water column suggests that gas emission from these sediments is a potentially significant source of greenhouse gas the interaction between shallow gas migration and coastal erosion would therefore potentially lead to increased greenhouse gas emission and accelerated sediment erosion such results can be applied to other costal locations around the world

stratigraphy and paleoenvironmental changes in the yangtze delta during the late quaternary the yangtze delta area may be subdivided into paleo valley and paleointerfluves of the last glaciation the postglacial transgressive sedimentary cycle ptsc on the front zones of the paleointerfluves is composed of marsh nearshore and barrier lagoon shallow marine and nearshore tidal flat units with a basement in stiff clay the ptsc in back zones of the paleointerfluves consists of lacustrine marsh deposits the ptsc in the incised valley contains river channel floodplain estuary estuarine shallow marine and deltaic units with an erosional surface at its bottom the stiff clay and the erosional surface constitute the ptsc lower boundary the stiff clay consisting of a paleosol experienced deposition alternating with pedogenesis during the falling of sea level during 18o stage 3 ongoing pedogenesis in the sea level lowstand of 18o stage 2 and early diagenesis after paleointerfluve inundation by the sea level rise of 18o stage 1 the climate during the paleosol formation was temperate with more than 500 mm a 1 rainfall and frequently fluctuating groundwater the yangtze river incised its course during falling sea level of stage 3 and a huge incised valley was formed during the sea level lowstand stage 2 the filling of the incised valley took place during the postglacial sea level rise and delta formation occurred at a late stage of ptsc development

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

mid to late holocene geomorphological and hydrological changes in the south taihu area of the yangtze delta plain china abstract the taihu plain of the lower yangtze valley china was a centre of rice agriculture during the neolithic period reasons for the rapid development of rice cultivation during this period however have not been fully understood for this coastal lowland which is highly sensitive to sea level change to improve understanding of the geomorphological and hydrological context for evolution of prehistoric rice agriculture two sediment cores dtx4 and dtx10 in the east tiaoxi river plain south taihu plain were collected and analysed for radiocarbon dating diatoms organic carbon and nitrogen stable isotopes 13c and 15n grain size and lithology these multiproxy analyses revealed that prior to ca 7500 cal yr bp the east tiaoxi river plain was a rapidly aggrading high salinity estuary the palaeo taihu estuary after ca 7500 cal yr bp low salinity conditions prevailed as a result of strong yangtze freshwater discharge subsequently seawater penetration occurred and saltmarsh developed between ca 7000 and 6500 cal yr bp due to accelerated relative sea level rise this transgression event influenced a large area of the taihu plain during the holocene as shown by multiple sediment records from previous studies persistent freshwater marsh or subaerial land formed due to dramatic shrinkage closure of the palaeo taihu estuary after ca 5600 cal yr bp when sea level was relatively stable we speculate that geomorphological and hydrological changes of the east tiaoxi river plain played an important role in agricultural development across the taihu plain during the neolithic period the closure of the palaeo taihu estuary and the formation of stable freshwater marsh or subaerial land after ca 5600 cal yr bp were critical preconditions encouraging the rapid rise of rice productivity in the liangzhu period 5500 4500 cal yr bp this development changed the landscape and river systems and thus provided adequate freshwater supply to the taihu plain

the role of sea level rise monsoonal discharge and the palaeo landscape in the early holocene evolution of the pearl river delta southern china abstract the early holocene history of the pearl river delta is reconstructed based on a series of sediment cores obtained from one of the main palaeo valleys in the basin sedimentary and microfossil diatom analyses combined with radiocarbon dating provide new evidence for the interactions between sea level rise antecedent topography and sedimentary discharge changes within the deltaic basin since the last glacial these new records show that river channels of last glacial age incised down to c 40 m into an older possibly mis5 age marine sequence which forms the floor of the deltaic basin and exists primarily at c 10 m 15 m below present mean sea level rapid postglacial sea level rise flooded the incised valleys by the beginning of the holocene and prior to c 9000 cal years bp marine inundation was largely confined within these incised valleys the confined available accommodation space of the incised valleys combined with strong monsoon driven freshwater high sediment discharge and a period of rapid rising sea level meant that sedimentation rates were exceptionally high towards c 8000 cal years bp as sea level rose to about 5 m marine inundation spilled out of the incised valleys and the sea flooded the whole deltaic basin as a result the mouth of the pearl river was forced to retreat to the apex of the deltaic basin water salinity within the basin increased markedly as the previously confined system dispersed across the basin and the sedimentation changed from fluvial dominated to tidal dominated sea level continued to rise albeit at a much reduced rate between 8000 and 7000 cal years bp and deltaic sedimentation was concentrated around the apex area of the basin during the last 7000 cal years bp the delta shoreline moved seawards and the sedimentary processes changed gradually from tidal dominated to fluvial dominated

features and sealing mechanism of shallow biogenic gas in incised valley fills the qiantang river eastern china a case study abstract late quaternary shallow biogenic gas reservoirs have been discovered and exploited in the qiantang river qr estuary area eastern china the fall of global sea level during the last glacial maximum resulted in the formation of the qr incised valley from bottom to top the incised valley successions can be grouped into four sedimentary facies river channel facies floodplain estuarine facies estuarine shallow marine facies and estuarine sand bar facies all commercial biogenic gas pools occur in floodplain estuarine sand bodies of the qr incised valley and its branches the deeply incised valleys provided favorable conditions for the generation and accumulation of shallow biogenic gas the clay beds that serve as the direct cap beds of the gas pools are mostly restricted within the qr incised valley with burial depths ranging from 30 to 80 m remnant thicknesses of 10 30 m and porosities of 42 2 62 6 in contrast the mud beds cover the whole incised valley and occur as indirect cap beds with burial depths varying from 5 to 35 m thicknesses of 10 20 m and porosities of 50 6 53 9 the pore water pressures of clay and mud beds are higher than that of sand bodies and the difference can be as much as 0 48 mpa the pore water pressures of clay or mud beds can exceed the total pore water pressure and gas pressure of underlying sand reservoirs shallow biogenic gas can be completely sealed by the clay and mud beds which have higher pore water pressure the direct cap beds have better sealing ability than the indirect cap beds generally the pore water pressure dissipation time of clay and mud beds is conspicuously longer than that of sand beds this indicates that the clay and mud beds have worse permeability and better sealing ability than the sand beds however once the gas enters the sand lenses the pore water pressure cannot release efficiently

holocene delta evolution and sediment flux of the pearl river southern china delta progradation and sediment flux of the pearl river delta prd southern china during the holocene are presented based on analyses of borehole data on the delta plain results indicate that the delta prograded into the drowned valley because of early holocene inundation from 9 to 6 cal ka bp as sea level rise decelerated the sea level reached its present level at about 6 cal ka bp and as a consequence a large portion of the drowned valley was covered by the estuary with more than 160 rock islands and platforms the scattered landmasses promoted active deposition and acted as deposition nuclei during deltaic evolution consequently apart from exhibiting a general tendency towards progression prd development occurred less regularly over time and space because of deposition around island boundaries during the last 2 ka mainly because of significantly increased human activities which have trapped sediments in the encircled tidal flats along the front of delta plains the shoreline has advanced rapidly estimated sediment fluxes for the three periods 9 6 6 2 and 2 0 cal ka bp based on the sediment volume analysis were 17 25 22 30 and 44 58 million t a 1 respectively copyright c 2016 john wiley sons ltd

optical dating of holocene tidal deposits from the southwestern coast of the south yellow sea using different grain size quartz fractions abstract the tidal flat deposit provides ideal sedimentary records for paleoenvironmental studies reliable chronology is crucial to utilize this archive for deciphering the history of environmental changes in this study we applied optically stimulated luminescence osl dating method to a holocene tidal flat sequence using both coarse grained cg 90 200 m and fine grained fg 4 11 m quartz extracts from a sedimentary core yz07 in western coast of the south yellow sea the luminescence characteristics of the two grain size fractions were investigated and then their resulting osl ages were systematically compared the results suggested that most tidal flat deposits are well bleached and their fg quartz ages are generally consistent with cg quartz ages while some samples have cg ages underestimated compared with fg likely resulted from the k feldspar contamination for cg quartz hence we applied post ir osl dating and pulsed osl dating techniques they could overcome the problems caused by feldspar contamination and yielded identical dates as fg osl ages all osl ages are generally in stratigraphic order in contrast the 14c ages are much more disorder and characterized with severe inversions finally the age framework of the tidal flat sequence under this study was constructed based on the 30 osl ages and one acceptable radiocarbon age according to the age depth model three main periods of sedimentation rate sr variation were identified these sr changes are probably associated with sea level rise fall history and the depocenter landward seaward movement as well as the transition of depositional process within the holocene delta initiation the depositional environment changes were also reflected in sedimentological features of the tidal flat deposits in our study area

formation processes and evolution of holocene sediments in the yangtze offshore area a review and new interpretation on the response to sea level rise and deltaic progradation abstract seismic profiles integrated with borehole cores from offshore of the yangtze river delta characterize three distinctive holocene deposition units in correspondence to estuarine shallow marine and prodelta facies respectively units to sedimentary processes and evolution of three units in response to sea level rise and yangtze delta development was studied estuarine facies occurred as a cluster of mud ridges unit was considered to be formed during the later stage of the period 10 8 cal ka bp with the prevalence of tidal erosion processes at the same time however the area south of the ridge field experienced rapid deposition possibly due to shelter effects of the zhoushan archipelago unit characterized by homogeneous mud composition rapid accumulation rates and a seaward dipping structure indicated a gravity flow deposition most likely related to the wave and or tidal current induced fluid mudflows during the period of 8 5 cal ka bp intrusion of a mud diapir during 5 3 cal ka bp related to gravity subsidence localized near the river mouth lead to deformation of unit during the 3 ka to present the delta advanced to the study area depositing subaqueous clinoform unit meanwhile erosional processes dominated by tidal currents were promoted by the southeastward progradation of the delta sediments deposited in the north of the area were transformed into tidal sand ridges we predict that the delta will likely reduce in area with a further progradation in the recent future

optical dating of holocene sediments from the yangtze river changjiang delta china abstract establishing a reliable chronology is essential for understanding delta evolution which is normally performed using radiocarbon 14c dating and the recently emerging technique of optically stimulated luminescence osl the application of the latter one to the holocene yangtze river changjiang delta deposit is still quite limited in this study two 60 9 m long cores were collected from taizhou tz and nantong nt within the paleo incised valley of the yangtze river and a total of seven and nine osl samples were collected from the tz and nt cores respectively in addition ten accelerator mass spectrometry ams 14c ages of the tz core were presented with eight ams 14c ages that were previously obtained from the nt core the single aliquot regenerative dose sar protocol was applied to coarse silt sized 45 63 m and fine sand sized 90 125 m quartz the results showed that the grains in the 45 63 m size fractions appeared to be better bleached than those in the 90 125 m size fractions and the detection of insufficiently bleached sediments is required in order to obtain accurate age estimates the ages adopted for the samples range from 3 ka to 9 ka for the tz core and from 1 ka to 14 ka for the nt core which were in general internally coherent within the limits of experimental errors and with respect to their stratigraphic order the ams 14c age of the tz core were significantly older than their osl ages while those from the nt core generally showed good agreement with their osl ages one should be cautious when using ams 14c to date deltatic deposits based on the osl ages two periods of rapid accumulation rates can be found in both cores which are linked to the rapid sea level rise in early holocene and migration of delta front facies in late holocene these investigations indicate that osl technique is an effective method with which to date holocene deltaic deposits especially in coarse sedimentary layers where organic carbon material is sparse

radiocarbon anomalies suggest late onset of agricultural intensification in the catchment of the southern part of the yangtze delta china abstract previously underused information from radiocarbon dates in well characterised sedimentary sequences in the southern yangtze delta china is here utilised in reconstruction of patterns of ancient erosion the southern yangtze delta was an important focus of food production in the early neolithic anomalous radiocarbon dates in holocene sediments from the southern part of the delta are unevenly distributed through time two clusters of dates in sediments ca 9000 7000 cal bp and ca 3000 1000 cal bp most likely indicate two periods of intensive erosion and redeposition of organic materials the older of the two clusters may have been associated with a marked episode of marine transgression whereas the younger cluster could reflect increasing levels of human disruption of soils and sediments in the catchment a relatively late increase in anthropogenic soil erosion supports recent archaeological evidence that following its early neolithic origins agricultural expansion and intensification occurred later on the southern yangtze delta than previously thought

holocene regression and the tidal radial sand ridge system formation in the jiangsu coastal zone east china abstract a radial tidal sand ridge system rtsrs spans more than 20 000 km 2 in the southwest yellow sea is fan shaped and stretches from qianggang toward the sea the marine rtsrs is located in a convergent divergent tidal current field cdtcf numerous drilling holes reveal an area of 3000 km 2 containing tidal sand strata in the jiangsu coastal plain on land adjacent to the marine rtsrs which stretches eastward from chengdong and is also a fan shaped with a central angle of 130 the tidal sand unit lies on a transgressive coastal barrier lagoon unit with an erosional surface between them and the latter unit is in turn lying on late pleistocene stiff mud the tidal sand unit is overlain by the littoral tidal flat unit and together they constitute the holocene regressive succession paleo current study reveals that a paleo current pattern similar to the modern marine cdtcf was present in the holocene sub aerial tidal sand strata therefore the sub aerial tidal sand bodies are deduced to be an ancient rtsrs that was formed during the holocene regression and gradually exposed and changed into land as the changjiang and huanghe deltas prograded both sub aerial and marine rtsrs should be formed in the same tidal depositional environment but in different development stages thus the radial tidal sand ridges in southwestern yellow sea should have formed not during the holocene transgression as most previous studies have inferred but in the process of holocene regression mineralogical analyses demonstrate that the sediment source of the sub aerial rtsrs initially came from the changjiang and later predominantly from the huanghe sea floor erosion by tidal currents may also provide sandy material to form the rtsrs drilling cores and ground penetrating profiles show that the paleo valleys in the study area are much smaller than the present distributaries of the changjiang river thus the presumption of direct sand supply by a large river to form the rtsrs through its apical area is cannot be supported after the sea level reached the present high stand the jiangsu coastline has been prograding seaward as the changjiang delta expanded and this progradation was accelerated when the huanghe debouched in the study area the nearshore part of rtsrs has been gradually changing into land while the entire rtsrs extends seawards in the process of the development the rtsrs apex changed from chengdong to qianggang at present the coastline is still moving seaward while the outer part of the rtsrs suffers from some erosion owing to reduction of sediment supply from both the changjiang delta and the abandoned huanghe delta

provenance structure and formation of the mud wedge along inner continental shelf of the east china sea a synthesis of the yangtze dispersal system surficial grain size and down core clay mineralogical data show that sediment along the inner most part of the continental shelf in east china sea is mainly derived from the yangtze river changjiang spanning from the yangtze mouth 33 degrees n similar to 1000 km southward to the southwestern corner of the taiwan strait 24 degrees n high resolution chirp seismic profiles reveal an elongated mud wedge extending along the inner shelf with a northern depocenter on the modern yangtze delta and a southern depocenter at 27 5 degrees n four distinct acoustic units are delineated within the mud wedge from bottom up unit i late pleistocene mainly valley fills unit ii formed by transgressions thin strata unit iii 11 2 kyr bp downlapping strata and unit iv 2 0 kyr bp flat and opaque strata incised valleys up to 15 m deep are filled by flat lying or inclined strata in unit i the thin 3 m and acoustically transparent unit ii is only seen between 30 and 26 degrees n in water depths between 40 and 90 m separated by acoustically opaque strata or unconformities units iii and iv are widely distributed during the past 11 kyr yangtze sediment accumulation has been unsteady showing two high and one low accumulation rate periods the high accumulation period at 5 8 kyr bp may be related to maximum east asian summer monsoon precipitation in the yangtze basin the other high accumulation period 0 2 kyr bp probably reflects intensive human activities in the river s watershed the low accumulation rate period at 2 5 kyr bp which is seen in both northern and southern yangtze depocenters is probably related to low river discharge and or intensified taiwan warm current and china coastal current c 2011 elsevier b v all rights reserved

changes in environment and provenance within the changjiang yangtze river delta during pliocene to pleistocene transition abstract this study investigates heavy mineral assemblages in sediments of the modern changjiang delta yangtze river and the quaternary pliocene q n boundary strata within the delta area with the aim of deciphering changes in sediment provenance and the depositional environment during the pliocene to pleistocene transition major heavy mineral assemblages in the modern changjiang sediments originate from their provenance rocks while the distribution of unstable amphibole ultrastable zircon tourmaline and rutile and altered minerals limonite leucoxene are closely related to the climate and the hydrodynamic environment within the catchment the ratio of a certain unstable mineral amphibole to an altered mineral limonite is considered to be a sensitive indicator of the chemical weathering intensity that is largely affected by climate conditions heavy mineral data of core sediments reveal distinctly different environments and provenances between the upper quaternary and lower pliocene sedimentary strata in the changjiang delta the pliocene sediments are characterized by abnormally high contents of limonite 42 leucoxene 8 and zircon 15 but an extremely low amphibole content 5 enrichment of zircon is indicated from the mid lower changjiang catchment where granitoid rocks are widely distributed the strong enrichment of altered minerals and the considerable great loss of unstable minerals suggest that pliocene weathering was much stronger than it is nowadays in contrast high contents of amphibole garnet and pyroxene and the low stable mineral content in the quaternary strata indicate that sediment provenances may have extended to the upper changjiang catchment which underwent weak chemical weathering these results imply that changjiang as a large river system might have drained the east china s continental margin prior to the q n transition the distinct heavy mineral assemblages found at the q n boundary in the changjiang delta are indicative of a drastic environment with provenance changes in response to intensive neotectonics it is thus inferred that sensitive heavy mineral indices can be used to indicate the q n boundary in the changjiang delta where reliable geochronological proxies have rarely reached an agreement

link between east asian summer monsoon and sedimentation in river mouth sandbars since the early holocene preserved in the yangtze river subaqueous delta front this paper presents geochemical and grain size records since the early holocene in core ecs0702 with a fine chronology frame obtained from the yangtze river subaqueous delta front since 9500 cal yr bp the proxy records of chemical weathering from the yangtze river basin generally exhibit a holocene optimum in the early holocene a weak east asian summer monsoon easm period during the middle holocene and a relatively strong easm period in the late holocene the 8 2 and 4 4 cal ka bp cooling events are recorded in core ecs0702 the flooding events reconstructed by the grain size parameters since the early holocene suggest that the floods mainly occurred during strong easm periods and the yangtze river mouth sandbar caused by the floods mainly formed in the early and late holocene the yangtze river mouth sandbars since the early holocene shifted from north to south affected by tidal currents and the coriolis force and more importantly controlled by the easm our results are of great significance for enriching both the record of holocene climate change in the yangtze river basin and knowledge about the formation and evolution progress of the deltas located in monsoon regions

simple kinetic models of petroleum formation part ii oil gas cracking kinetic schemes describing oil gas cracking are a required component of models which predict the masses compositions and phases of petroleum expelled from source rocks an additional application is in predicting the temperature zone over which reservoired oil deposits will be degraded to gas this simple first order kinetic model calibrated on closed system laboratory pyrolysis of 16 different source rock samples describes the bulk conversion of oil c6 molecular range to gas c1 5 molecular range cracking rates vary markedly between samples depending on the saturate to aromatic ratio of the generated oil the initial hydrogen index hl0 of the sample taken as an indirect measure of the saturate to aromatic ratio of the oil it generates correlates strongly with optimized rate constants for oil cracking in individual samples thus cracking rates are predictable using a simple routinely performed geochemical screening measurement source rocks with high hl0 tend to generate saturate rich oils with a high mean activation energy and a tight distribution of bond energies which crack relatively slowly over a high but relatively narrow temperature range source rocks with low hl0 generate aromatic rich oils with a low mean activation energy and a broad distribution of bond energies which crack relatively rapidly over a lower but relatively wide temperature range this is an important contributing factor in the observed gas proneness of type iii source rocks with low hl0 the projected cracking window defined limits at 10 90 of initial oil degraded reference heating rate 2 c ma 1 varies from 155 to 205 c in very high quality source rocks hl0 600 mg g c 1 to 115 205 c in very poor quality source rocks hl0 50 mg g c 1 an order of magnitude increase decrease in heating rate elevates depresses these temperature windows by ca 15 c the extrapolations to the geological subsurface are subject to a confidence limit no better than 7 c extrapolation to the reservoir environment requires caution because kerogen an important potential catalyst and hydrogen donor allowing 100 cracking efficiency in the source rock is absent furthermore fractionation during expulsion causes saturate enrichment of expelled ultimately reservoired oils thus in reservoir cracking should be at least as slow as cracking in good quality source rocks and coke or pyrobitumen formation is needed to conserve the hydrogen balance a case history based on deep petroleum pools of the uk central north sea confirms these projections demonstrating no positive evidence of significant in reservoir cracking at temperatures as least as high as 174 c and perhaps even 195 c previous studies have overestimated the importance of in reservoir cracking future studies aiming to predict petroleum composition in traps should concentrate on understanding the charge composition expelled from the kitchen

migration patterns of neolithic settlements on the abandoned yellow and yangtze river deltas of china archaeological records of the neolithic settlements on the eastern china coast between 35 n and 30 n an area covering the abandoned yellow river and the yangtze river delta plains reveal that neolithic people moved from the yellow river basin onto the northern coast for fishing hunting and dry land agriculture 7000 yr ago marine transgression interrupted their activities on the low lying 2 5 m in elevation coastal wetlands between 6000 and 5000 yr ago after which they reclaimed their land near the river mouths their migration routes on the southern yangtze delta plain indicate another scenario early neolithic communities moved onto the plain for wet rice cultivation despite relative sea level rise from 7000 to 4000 yr ago a large number of settlements were established on the lowlands between the eastern chenier ridges and the western taihu lake depression the chenier ridges with 1 0 m higher topography than the adjacent coastal area played a role in sheltering the neolithic people subsequently settlements waned considerably possibly due to further marine inundation combined with cold climate the present study shows that migration patterns of the neolithic settlements are closely associated with a gradually rising sea level between 7000 and 4000 yr ago

the use of foraminifera as indicators of tidal effects in estuarine deposits estuaries are classified according to the degree of mixing of freshwater and seawater into three categories stratified partially mixed and well mixed these generally relate to microtidal mesotidal and macrotidal conditions respectively with increase in tidal influence there is an increase in transport of foraminiferal tests both as bed load and especially in suspension the latter group are generally very small 200 m and include many open marine species when they are sedimented they lead to high diversity assemblages in environments where the diversity of the living assemblages is low the abundance of these exotic tests shows a progressive increase with increased tidal strength thus the presence of size sorting with small mean size diversity range and proportion of exotic individuals can be used as criteria for the recognition of tidal effects in ancient estuarine deposits

mineralogical and isotopic evidence for the sediment provenance of the western south yellow sea since mis 3 and implications for paleoenvironmental evolution abstract changing sediment provenance and related paleoenvironmental evolution since marine isotope stages mis 3 have been investigated based on accelerator mass spectrometry ams 14c and optically stimulated luminescence osl dating of core csdp 01 recovered from the western south yellow sea sys based on our results sea level fluctuations and monsoonal climate variations are identified as the principal factors driving these changes sea level fluctuations determined the accommodation space in the shelf area while the monsoonal climate controlled the sediment supply capacity from river to sea mineral and sr nd isotopic records reveal the major contribution of the paleo changjiang river yangtze river to the study core area during the early mid mis 3 which likely defined the northern limit of the paleo changjiang delta at that time high sediment supply and limited accommodation space led to the development of sediment fed systems on the sys shelf resulting in a high preservation potential for thick stacking and overlapping deltaic sediments along with deltaic progradation core sediment provenance gradually transformed from the paleo changjiang river to the paleo huanghe river yellow river near the late mis 3 implying that the paleo huanghe river likely emptied into the sys and built a large delta during the mis 3 interval a strong summer monsoon during the early mis 1 interval was favorable for the changjiang to deliver abundant sediments to the study core area a weak summer monsoon during the mid late mis 1 when the coastline had retreated to nearly its present day position decreased the changjiang and huanghe supply to the study area low sediment supply and sufficient accommodation space gave rise to the development of sediment starved systems during this period nd values fluctuated between the changjiang and huanghe sources at that time suggesting that sea bed erosion materials are the main sediment contribution to the study area in general sedimentary evolution in the western sys since mis 3 is a good example of river sea interaction in the marginal seas of southeast asia in which sea level and monsoonal climate changes should play an important role

seismic framework and the holocene morphological evolution of the changjiang river mouth china abstract acoustic profiling in combination with coring has been used to examine the recent evolution of river mouth of the changjiang two acoustic facies are present petrologic radiometric and seismic analyses show that the upper facies i of 10 20 m thick fine sand and silt represents the sandy shoals of late holocene age in the distributary and the 5 20 m thick lower facies ii of fine grained silty clay with abundant marine microfossils represents the mid holocene prodelta facies deposited as fillings in the former large estuarine valley of late pleistocene to early holocene origin rapid accumulation during the holocene has led to some instability of unconsolidated sedimentary strata in the distributary such as strata collapse and mud diaper formation the existence of large cross beddings such as tabular and trough stratification in facies i identifies the sediment transport as predominantly bed load driven by runoff and tidal currents two sets of discrete flood ebb flow troughs oriented nw and se reflect controls by tidal waves generated from the sea and the superimposition of runoff and ebb flows symmetrical sand waves that appear at the northern trough of one of the distributaries also indicate the balancing sediment dynamics between runoff ebb and flood currents whereas the asymmetrical ones in the southern trough indicate superimposed sedimentation by runoff and ebb flows a large quantity of sediment has been deposited in the slack water region between the discrete flood and ebb flows to form sandy shoals the principal mechanism of the evolution of estuarine islands in the holocene changjiang mouth the morphology of the extended river mouth to the southeast possibly indicates an external driving force such as the coriolis effect nw prevailing wind and longshore currents

multiple paleosols of the late albian boulder creek formation british columbia canada fifteen lithified paleosols closely spaced in vertical sequence occur in the top 90 m of the late albian boulder creek formation in the foothills of northeastern british columbia canada the paleosols have well developed profiles 0 5 to 1 5 m thick including a b and c horizons the paleosols are characterized by their grey colour cutans vertical roots peds spherulitic siderite and absence of sedimentary structures the paleosols formed during a period when one or more basin wide unconformities occurred as a result of either eustatic sea level fluctuations or local tectonic events these unconformities represent the terrestrial record of a lowered base level which caused valley incision and decreased rates of sedimentation on the incised flood plain the climate was humid to subhumid overall the environment in which these soils developed was of low relief and subject to little erosion the water table was high for part of the year but there is also evidence of periodic drying and oxidation of organic debris cumulatively the paleosols in this interval may represent 150000 yr of non deposition

yangtze offshore china highly laminated sediments from the transition zone between subaqueous delta and the continental shelf abstract this study examines the deposition of highly laminated muddy sediment in vibrocores recovered from a depth of 40 55 m of water and located 120 km east of the yangtze river mouth x radiographs show numerous sharp based sedimentary rhythmics with nearly parallel and undulated laminations interbedded with silty lenses and interbeds the laminated sediment varies from clayey silt to silty clay ams radiocarbon dates on well preserved bivalves are primarily younger than 5500 y bp indicating the formation of the laminated sediment under the present sea level conditions macro and microfossils in the sediments are consistent with the modern offshore sedimentary setting the laminated sediment originated from the yangtze estuary but the sedimentation processes were not deltaic the highly laminated sediment that lies below the normal wave base of 10 m was deposited on the seaward margin of the yangtze subaqueous delta closely associated with submarine tidal and storm generated currents

mangrove bank sedimentation in a mesotidal environment with large sediment supply gulf of papua the most extensive mangrove forests on earth are associated with major river systems the indo pacific region has numerous large rivers that discharge onto broad continental shelves and mangroves occur widely along these coastlines in the gulf of papua gop alone there are 3350 km2 of mangrove forests the majority of which 2900 km2 are associated with the fly kikori and purari river deltas this study examines data from 28 vibracores to describe preserved sedimentary strata and to determine rates of sediment accumulation in this dynamic coastal environment the observations suggest a common stratigraphy is contained in prograding mangrove banks of the mesotidal western gop and that it is similar to mud dominated and physically stratified stratigraphy recorded by other intertidal areas with and without mangroves experiencing large tidal range 2 m and sediment supply e g ganges brahmaputra and yangtze river deltas grain size sedimentary structure radionuclide and remotely sensed data are analyzed and four stratigraphic facies are identified 1 supratidal to high tidal muds 2 mid tidal sandy muds 3 low tidal sand and mud and 4 subtidal channel sands supratidal and high tidal sediments of gop mangrove forests are typically muddy but can have high sand contents 30 in areas exposed regularly to ocean waves these muds can be homogenous but commonly have physical structures laminations and bedding probably reflecting high rates of sediment accumulation relative to bioturbation mangrove muds may have low water contents due to infrequent inundation and because of their cohesive nature and abundant roots can form steep intertidal banks and erosional scarps mid tidal and low tidal sediments are thinly laminated 2 mm laminations likely deposited from fluid mud transport channel sediments have thin and thick mud and sand laminations but are identified by thick 5 cm sand beds a conceptual model of mangrove bank progradation is created using sedimentological and radionuclide data maximum sediment accumulation rates were determined using steady state 210pb profiles and greatest mean rates are found in mid tidal areas 4 4 cm year 3 9 g cm2 year slower accumulation occurs in high tidal and low tidal areas 1 8 and 1 5 cm year respectively 1 2 and 1 0 g cm2 year respectively remotely sensed data indicate that areas of erosion and accretion co exist in the kikori purari region very large 210pb accumulation rates were measured in areas of significant accretion supporting the validity of the calculated rates in areas of rapid accretion cores can have non steady state or event related 210pb profiles reflecting episodic sedimentation or complex radionuclide scavenging dynamics most cores from the fly river delta are of this type sediment trapping in western gop mangroves is estimated to account for 2 14 of the total gop sediment load

coastal gia processes revealed by the early to middle holocene sea level history of east china abstract in order to examine relative sea level responses to the postglacial ice volume change and the glacio hydro isostatic adjustments gia this study investigated the inner part of the hangzhou bay east china a tectonically relatively stable far field location and reconstructed the early to middle holocene sea level history this investigation has established the elevational relationship between modern saltmarsh mudflat and tidal levels based on diatom analysis for sea level indicative meaning estimates produced 17 high quality sea level index points and simulated gia processes for the study site these results reveal that the relative sea level rose from 38 3 1 6 m in c 10 000 cal a bp to the present height by c 7000 cal a bp and the average rate of sea level rise decreased gradually from 19 6 2 6 mm a to 2 3 1 5 mm a during the 3000 years this period of sea level history was punctuated by two episodes of accelerated rise around 8200 and 7500 cal a bp the relative sea level rose to 0 8 1 4 m above msl by c 6500 cal a bp followed by a gradual fall back to the present height at 4500 cal a bp implying a different response to the potential additional ice melting between 7000 and 4000 cal a bp a comparison of the sea level histories between the inner and outer hangzhou bay indicates the coastal levering effect due to the marine inundation of the continental shelves a further comparison between sea level data from china and malay peninsula reveals different gia effects between the cathaysia yangtze blocks and the sundaland block

delta development and channel incision during marine isotope stages 3 and 2 in the western south yellow sea abstract approximately 4100 km of high resolution seismic profiles recently obtained from the western south yellow sea were subdivided into seven seismic units by six major seismic surfaces three sediment cores between 60 and 71 m in length obtained from localities on the seismic profile lines were analyzed for sedimentary characteristics clay mineral components and benthic foraminiferal and ostracod assemblages and were also dated by ams 14 c and optically stimulated luminescence to document the environmental history of the region stratigraphic units in the cores were confidently correlated with seismic units in the profiles stratigraphic correlation among these three cores and the previous well studied core qc 2 was facilitated by the cold water deposits in marine isotope stage mis 5 the three cores document the sedimentary sequence during the period from mis 6 up to mis 1 strata formation and sedimentary environment changes since mis 5 are strongly controlled by sea level fluctuations most of the successions were formed in mis 5 mis 3 and mis 1 with major erosions in mis 4 and mis 2 particularly our data revealed the presence of a large delta active during mis 3 likely from the early stage of mis 3 to about 40 cal kyr bp that was subsequently affected by channel incision the delta succession and incised channel fills have a high concentration of smectite in their clay mineral components suggesting that the paleo yellow river was the main contributor to the delta development and channel incision the delta sequence has a coarsening upward trend and consists of two seismic facies the upper facies shows lateral alternations of chaotic and oblique or very low angle reflectors which correspond to sandy proximal delta front and delta plain facies and the lower facies is characterized by seaward dipping clinoforms which correspond to muddy distal delta front and prodelta facies the top surface of the delta inclines very gently seaward consistent with a deltaic development associated with the sea level fall in mis 3 the incised channel system consists of two main channels with multiple tributaries in a dendritic pattern the incised channel fills begin with fluvial and then estuarine sediments which are truncated by a transgressive ravinement surface and capped by transgressive deposits the main incision channels have a terraced cross sectional morphology which is interpreted to reflect multiple episodes of sea level fall during incision presumably from the late mis 3 to the last glacial maximum

late quaternary stratigraphy of the yeongsan estuary southwestern korea abstract the 18 820 m long sediment core mw 1 from the yeongsan estuary consists of five primary unconsolidated to semi consolidated units ranging in age from late pleistocene to holocene overlying a cretaceous aged basement from oldest to youngest these units include units 1 2 3 fluvial units unit 4 paleosol unit and unit 5 holocene estuarine deposits units 1 2 and 3 are interpreted as in channel or overbank deposits plant materials included within the units and the toc tn total organic carbon total nitrogen ratios 11 14 are also indicative of terrestrial origin unit 2 yields radiocarbon date of 37 700 14 c yrbp unit 4 the paleosol unit is estimated to be originally deposited in fluvial setting such as the area of floodplain or backswamp away from the main channel based on the sporadic distribution of the stagnant freshwater acritarch pseudoschizaea and algae spirogyra the timing of deposition of the original sediments of the paleosol unit is constrained by radiocarbon age of underlying fluvial sediments unit 2 the timing of pedogenesis is around the last glacial maximum when sea level of the yellow sea was lowered temperature was lowered rainfall was reduced and the inland was sparsely vegetated estuarine deposits unit 5 are interpreted to be deposited during the holocene marine transgression

the chronology of a sediment core from incised valley of the yangtze river delta comparative osl and ams 14 c dating abstract optically stimulated luminescence osl dating has gained increased use in dating deltatic deposits however its application can be hindered by the problem of incomplete bleaching to address this limitation we test the single grain osl method for the first time in the yangtze river delta a total of eight osl and 14 ams 14c samples were obtained from a 50 8 m long sediment core from the incised valley of the delta quartz extracted from eight osl samples from the core was first measured with small multi grain aliquots using medium 45 63 m and coarse grained 90 125 m or 150 180 m fractions to test the internal consistency of their respective ages the results showed that four of five medium grained quartz samples appeared to be well bleached in contrast the coarse grained quartz samples revealed poor bleaching except for two samples from the delta front facies five coarse grained quartz osl samples were further analyzed using a single grain osl technique only 0 5 0 7 of the grains passed the rejection criteria single grain osl dating is appropriate for age determination of coarse grained sediments which have been affected by incomplete bleaching however it consumes a lot of instrument time central and minimum age models cam and mam were used to calculate the burial age of the samples mam ages fit best in the stratigraphic sequence small aliquots are recommended as effective in identifying incomplete bleaching for medium or coarse grained quartz a comparison of ams 14c dates and osl ages shows that 14c values are 1 3 ka older than osl ages according to the osl ages core sd experienced rapid accumulation 10 8 ka and in the last 2 ka the former is linked to rapid sea level rise in early holocene while the latter is primarily due to the migration of depo center towards the core site rather than entirely increased sediment delivery caused by human activities

sediment provenance and paleoenvironmental change in the middle okinawa trough during the last 18 5 ky clay mineral and geochemical evidence abstract we investigated grain size clay mineralogy elemental geochemistry organic composition and ams 14 c dating ages in core kx12 3 from the middle okinawa trough in order to better understand the sediment provenances and transport processes and also the forcing mechanisms behind their variations over the last 18 5 ky the geochemical mineralogical indices reveal three notable phases of change in the sediment provenance of the core which are related to the development of the kuroshio current coupled with sea level fluctuations the position shift of the mouths of large rivers the magnitude of tidal bottom stress and the east asian monsoon intensity the sea level lowstand deposits of interval 1 18 5 9 3 ka formed from mixed sediments originating mostly from chinese rivers the paleo huanghe and the paleo changjiang as well as from materials eroded from seafloor by the strong tidal stress thereafter during interval 2 9 3 8 7 ka a significant sea level rise the moderate tidal bottom stress and a gradual landward retreat of river mouths led to obviously decreased sediment supplies from both seafloor erosion and mainland china rivers especially the paleo huanghe into to the study area after this transitional period the dominant sediment provenance during the mid to late holocene interval 3 changed to the changjiang and seafloor erosion resulting in lower detrital linear sedimentation rate and finer grain size at the same time some fine grained materials from taiwan may have been transported northward to the study area by the kuroshio current as evidenced by higher values of chlorite kaolinite ratio and chemical index of illite and lower toc tn values in addition a prominent decline in chlorite kaolinite values that occurred at 5 0 3 5 ka may have been linked to a suppression of the kuroshio current probably related to the pulleniatina minimum event and or the late holocene neoglacial cold event commonly found in the northwestern pacific

a record of late holocene environmental change from southern new england usa article i nfo article history received 28 march 2011 available online 31 august 2011 analyses of a sediment core from little pond located in the town of bolton massachusetts provide new insights into the history of environmental and ecological changes in southern new england during the late holocene declines in organic content and peaks in the abundance of isoetes spores indicate reduced water depth at 2900 2600 2200 1800 and 1200 800 calibrated years before present cal yr bp generally consistent with the timing of dry conditions in records from elsewhere in the northeastern united states the little pond pollen record features little change over the last 3000 yr indicating that the surrounding vegetation was relatively insensitive to these periods of drought the 1200 800 cal yr bp dry interval however coincides with increased abundance of castanea pollen suggesting that the expansion of castanea in southern new england may have been influenced by late holocene climatic variability

late quaternary palaeosols in the yangtze delta china and their palaeoenvironmental implications abstract the stiff clays beneath holocene strata in the yangtze delta are interpreted as palaeosols based on pedogenic features including illuvial argillans voids cracks iron manganese concretions and nodules and carbonate materials variations in clay content with depth the occurrence of foraminifera and the environmental magnetism characteristics of the palaeosols suggest that their parent materials are floodplain deposits anisotropy of magnetic susceptibility ams parameters of the sediments correlate well both with sedimentary dynamics and depositional processes in different sedimentary environments and ams analysis may be a useful tool for inferring sedimentary environments based on their considerable thickness 3 0 m vertical changes of palaeosol maturity and occurrence of ageing argillans throughout the palaeosols the palaeosols are inferred to be compound ones pedocomplexes resulting from alternating deposition and pedogenesis on the palaeointerfluve of the yangtze river phytoliths in the palaeosols indicate that climates turned generally from warm and wet to cold and dry with marked fluctuations during development of the palaeosols this suggests that the palaeosols developed mainly during the marine regression prior to the last glacial maximum the vertical distribution of manganese materials e g concretions nodules speckles and mottles in the palaeosols suggests that the groundwater tables were about 2 0 3 0 m beneath the upper boundary of the palaeosols during their development yellow brown streaks and speckles are abundant from the middle to lower parts of the palaeosols and layers with high caco 3 content occur in the strata just beneath the palaeosols but which lack caliche suggesting that the groundwater table fluctuated markedly during their development voids and cracks filled with clays and carbonate nodules less than 0 1 mm in diameter with thin iron manganese rims are abundant in the palaeosols indicating that wet and dry seasons were marked during the palaeosol development it is suggested that the monsoonal influence was marked in the yangtze delta with both winter and summer monsoons strongly developed during the development of the late quaternary palaeosols

contrasting flooding histories of mississippian carbonate platforms revealed by marine alteration effects in palaeosols palaeosols associated with exposure surfaces in mississippian platform carbonate sequences in britain invariably show evidence for later alteration by sea water these alteration effects can be attributed to flooding of the emergent platforms during transgressions that terminated exposure surface development a study of 230 palaeosol profiles representing 60 stratigraphic levels has revealed a two fold division of these marine hydromorphic effects palaeosols in ramp sequences chadian arundian stages are capped by ferroan dolomite horizons with carbonized rootlets pyrite and thin coals the ferroan dolomites exhibit 13c and 18o values indicative of formation in brackish waters these are interpreted as coastal marshes that developed landward of a transgressive shoreline younger asbian brigantian palaeosols lack these dolomites but have been extensively pyritised the pyrite also developed through marine hydromorphic alteration but flooding was relatively instantaneous over the flat topped platforms these differences in flooding history reflect both different platform configuration and more rapid transgressions during the asbian brigantian likely a result of glacio eustatic effects flooding characteristics of the asbian brigantian platforms differ from those associated with late cainozoic examples apparently because complete platform rims were not developed similar mineralogical alteration effects are likely to be common in other platform sequences in the geological record but have not been documented

rising waters new geoarchaeological evidence of inundation and early agriculture from former settlement sites on the southern yangtze delta china new pollen phytolith charcoal and diatom data from 14c ams dated sediments from three clusters of former occupation sites on the southern yangtze delta liangzhu majiabang and chuodun reveal

millennial scale east asian summer monsoon variability recorded in grain size and provenance of mud belt sediments on the inner shelf of the east china sea during mid to late holocene abstract the response of the monsoon climate on the inner shelf of the east china sea ecs to abrupt climate changes events within the monsoonal yangtze river drainage is contentious repositioning of the monsoon front is thought to have been responsible for the changes in hydroclimate over the yangtze river drainage which has exerted great impact on the sedimentation of the inner shelf of the ecs during the holocene here we present high resolution analyses of grain size and provenance of the sediments from core md06 3040 recovered from the inner shelf of the ecs during md155 marco polo ii images xiv cruise significant variability occurred in the core md06 3040 with notable decrease in east asian summer monsoon precipitation presumably drought events at 6000 bp 5300 bp 4500 bp 3700 3300 bp 2200 bp 1400 1300 bp and 800 600 bp which coincide with the 18ow record in the northern ecs and stalagmite 18osp records from southern china similar patterns of these temporal variations suggest that the yangtze river discharge associated with easm precipitation has been a dominant control on the sedimentation on the inner shelf of ecs

the influences of suspended load on the sedimentation in the coastal zones and continental shelves of china abstract the coastline of china intersects belts of subsidence and uplift river sediments mainly discharge to the coastal zones of subsidence belts where they contribute more than 90 of the total suspended load of river sediment transported into the coastal zones rivers discharging into the coastal zones of the uplift belts contribute no more than 10 of the total in coastal zone subsidence belts tidal flat deposits develop and quaternary strata are quite thick in coastal zone uplift belts in contrast beach sand and gravel and aeolian sand develop only where great amounts of fine sediments are provided to coastal uplift zones by the adjacent major rivers can tidal flat deposits develop quaternary strata are thin in uplift belts and patchy relict sediments are present on the continental shelves on the continental shelves of the southern part of the east china sea and the south china sea where discharge of river sediments is fairly small relict sediments form a broad continuous deposit marine processes can transport the sediments of large rivers into the mouths of small adjacent rivers where various sand and mud bodies form so far in the coastal zones of china no coastal depositional body is known to have formed from sediments derived directly from the continental shelves

holocene paleosols of the upo wetland korea their implications for wetland formation abstract a 4 490 m long core up 1 was recovered from the marginal part of the upo wetland the wetland is a typical riverine wetland in korea and has been designated as a protected wetland in accordance with the international ramsar treaty we studied the holocene environmental changes of the upo wetland and the depositional conditions under which the upo wetland formed the core is divided into four units on the basis of grain size distribution abundance of mottles and vertical color variation unit 1 has undergone pedogenic processes resulting in variably weak to moderate soil profile development unit 1 paleosols are regarded as synsedimentary soils of floodplain origin and the radiocarbon data suggest that the whole paleosol profile spans the last 5790 years the boundaries between the soil horizons are not clear cut probably due to a repeated cycle of accumulation denudation and soil forming processes the recurrence of these processes initiated the development of the upo wetland the lower boundary of unit 2 lies at about 2300 14c yr bp the beginning of the subatlantic age in korea the lack of intense soil formation and abundant clay content in unit 2 indicate that the geomorphologically stable wetland was developed around the coring site at that time this means that the depositional environment changed from a floodplain to a stable continuously submerging wetland setting an abrupt change in sediment textures was detected in unit 3 which commenced formation around 1000 900 14c yr bp indicative of geological events such as inundations or inflows of slope wash sediments anthropogenic deforestation and plowing around the upo wetland area might have started at that time

paleocurrent analysis for the late pleistocene holocene incised valley fill of the yangtze delta china by using anisotropy of magnetic susceptibility data abstract anisotropy of magnetic susceptibility ams analysis has been conducted on samples from borehole core cm 97 from the yangtze river changjiang incised valley fill china to determine the paleocurrent directions to help in reconstructing sedimentary paleoenvironments borehole cm 97 consists of fluvial unit 1 estuarine units 2 6 and deltaic units 7 9 sediments after the last glacial maximum in ascending order the ams results show that the paleocurrent directions for the tide dominated estuarine and deltaic sediments were westerly or northwesterly directed flood tide dominated but give no definite trend for the fluvial sediments comparison between the paleocurrent directions inferred from primary sedimentary structures and in situ ams data shows that they are in good agreement confirming the applicability of ams as a good paleocurrent indicator for sediments deposited in coastal tide dominated environments considering that these sediments were strongly tide influenced and the tidal pattern since 12 kyr bp has not changed significantly we think that the westerly or northwesterly current direction most probably resulted from flood tidal currents and the sedimentary paleoenvironment was a flood tide dominated estuary or delta additionally it has been found that downhole changes of some ams parameters including the mean magnetic susceptibility k the corrected anisotropy degree p j and the magnetic foliation f clearly mark the defined stratigraphic boundaries in the borehole this further extends the validity of ams as a good stratigraphic marker in addition to its long known credibility as a sensible paleocurrent recorder

holocene paleoenvironmental changes in mud area southwest off cheju island east china sea evidence from benthic foraminiferal assemblages and stable isotope records abstract a sediment core retrieved from the mud area southwest off cheju island masci was analysed for benthic foraminifera grain size and stable isotopes and constrained by ams14c dating holocene paleoenvironmental changes in this broad shallow shelf were investigated with special focus on the evolution of the masci and its related ocean eddy system the results indicate that the east china sea shelf has undergone four major environmental evolution stages during the holocene prior to 9 8 cal kyr bp the benthic foraminiferal assemblages were dominated by low salinity shallow water species ammonia beccarii linnaeus elphidium advenum cushman and cribrononion subincertum asano reflecting a near coast deposit environment a noticeable transition of the benthic foraminifera from an a beccarii dominated to ammonia compressiuscula brady dominated assemblage taking place at approximately 9 8 cal kyr bp together with a contemporaneous increase in 18o and 13c provides evidence that a rapid rise in sea level occurred at this time in the east china shelf a gradual increase in 18o between 9 8 and 6 cal kyr bp indicates a steady strengthening influence of open ocean water on the area under study a sudden increase in the abundance of benthic foraminifera along with a decrease in the coarse fraction imply that an early eddy circulation system was established since almost 6 cal kyr bp in the masci this eddy circulation system was quite weak but gradually strengthened between 6 and 3 cal kyr bp possibly due to the intrusion of the yellow sea warm current yswc a more stable mud deposition period characterised by a high sedimentation rate of fine grained sediment and lighter value of 13c starting at approximately 3 cal kyr bp indicates that the masci was formed mainly during the late holocene we believe that the strengthened yswc since 3 cal kyr bp might increase the trap efficiency of the eddy system thereby accounting for the high sedimentation rate of mud deposits during this period

a unique middle pleistocene beech fagus rich deciduous broad leaved forest in the yangtze delta plain east china its climatic and stratigraphic implication abstract pollen analysis of middle pleistocene sediments from the yangtze delta plain provides a paleoecological reconstruction and has implications for stratigraphic correlation in east china the pollen assemblage is characterized by high values of fagus 16 8 on average which is unusual because fagus is generally present only sporadically in other lowland quaternary pollen records from the region in addition to fagus the assemblage has a rich diversity of broad leaved deciduous trees including quercus ulmus carpinus ostrya juglans betula and liquidambar as well as conifers including pinus picea abies larix and tsuga thus the pollen flora suggests a broad leaved deciduous forest mixed with abundant conifers which developed under cooler and more humid conditions than present the stable pollen sequence throughout the studied section suggests a stable environment beech forests also characterize the middle pleistocene of taiwan and japan and thus may be a stratigraphic indicator of the middle pleistocene in east asia the yangtze delta plain may have been an important refugium for the last survival of fagus in the lowlands