sources and dispersal of land based runoff from small hawaiian drainages to a coral reef insights from geochemical signatures abstract land based sediment and contaminant runoff is a major threat to coral reefs and runoff reduction efforts would benefit from knowledge of specific runoff sources geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment then used in the nearshore region of a coral reef fringed urban embayment on southeast oahu hawaii to describe sources and dispersal of land based runoff the sedimentary rare earth element ratio la yb n showed a clear distinction between the two main rock types in the overall contributing area tholeiitic and alkalic olivine basalt based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages sediment from one of five tholeiitic drainages had a distinct geochemical signature and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin sediment and the anthropogenic metals cd pb and zn were entrained in runoff from the most heavily urbanized region of the watershed although anthropogenic cd and zn had localized distributions close to shore anthropogenic pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore illustrating how trade wind driven sediment transport can increase the scale of runoff impacts to nearshore communities our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land based runoff in shallow coastal environments the application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff impacted coastal ecosystems worldwide

flux and fate of small mountainous rivers derived sediments into the taiwan strait article i nfo high resolution chirp sonar profiles across the taiwan strait reveal a large silt sand dominated deltaic clinoform up to 50 m thick overlying the postglacial transgressive sea floor across the southeastern central and northern strait delta like configuration and internal depositional sequences indicate a northwestward progradation from western taiwan primarily from the choshui zhuoshui river grain size and mineral data confirm the sediment s taiwanese derivation the chirp profiles together with existing radiocarbon and geomagnetic dates suggest that the clinoform has formed over the past 10 kyr the estimated volume of 375 km 3 of sediment mainly sand and silt suggests a mean annual accumulation of 60 10 6 t yr presumably much of fine mud delivered by taiwanese rivers has been washed away by the local currents and escaped either northeastward into the southern okinawa trough or southward into the south china sea numerous shallow borings onshore over the central western taiwan coastal plain reveal an additional 350 km 3

stable isotopic and biomarker evidence of terrigenous organic matter export to the deep sea during tropical storms abstract the global export of organic carbon oc is intimately linked to the total flux of terrestrial sediment to the ocean with the continental margins receiving 90 of the sediment generated by erosion on land recent studies suggest that a substantial amount of particulate oc poc might escape from the shelf and be exported to the continental slope deep sea sector although the mechanisms and magnitude of such deep sea poc transfer remain unknown here we investigate hyperpycnal flow associated total suspended matter tsm collected from water depths of 3000 m near the bottom of sea floor in the gaoping submarine canyon gsc off southwestern taiwan elemental c n isotopic 13 c 15 n and biomarker compositions of tsm were investigated to understand its biogeochemical characteristics a two end member 13 c mixing model indicates that deep sea tsm contains 90 terrigenous oc while a similar mixing model using 15 n reveals a lower proportion 58 organic biomarkers of tsm suggest contributions from a mixture of resuspended continental margin derived marine organic matter om mar and terrigenous sources revealing that terrestrial oc likely mixes with nitrogen rich marine material during rapid transport this study documents that rapid transfer of terrigenous organic matter om terr into the deeper regions of gsc occurred within a week of typhoon morakot likely through hyperpycnal injection of sediment laden warm freshwater from southern taiwan evidence from this typhoon morakot induced hyperpycnal plume event in taiwan demonstrates that extreme storm events provide an efficient way to export terrigenous oc without oxidation to hitherto unknown water depths of deep sea in the oceania region

isotopic evidence for the influence of typhoons and submarine canyons on the sourcing and transport behavior of biospheric organic carbon to the deep sea abstract export of biospheric organic carbon from land masses to the ocean plays an important role in regulating the global carbon cycle high relief islands in the western pacific are hotspots for such land to ocean carbon transport due to frequent floods and active tectonics submarine canyon systems serve as a major conduit to convey terrestrial organics into the deep sea particularly during episodic floods though the nature of ephemeral sediment transportation through such canyons remains unclear in this study we deployed a sediment trap in southwestern taiwan s gaoping submarine canyon during summer 2008 during which typhoon kalmaegi impacted the study area we investigated sources of particulate organic carbon and quantified the content of fossil organic carbon oc f and biospheric non fossil carbon ocnf during typhoon and non typhoon periods based on relations between total organic carbon toc isotopic composition 13 c 14c and nitrogen to carbon ratios n c of newly and previously reported source materials during typhoons flooding connected terrestrial rivers to the submarine canyon fresh plant debris was not found in the trap except in the hyperpycnal layer suggesting that only hyperpycnal flow is capable of entraining plant debris while segregation had occurred during non hyperpycnal periods the ocnf components in typhoon flood and trapped samples were likely sourced from aged organics buried in ancient landslides during non typhoon periods the canyon is more connected to the shelf where waves and tides cause reworking thus allowing abiotic and biotic processes to generate isotopically uniform and similarly aged ocnf for transport into the canyon therefore extreme events coupled with the submarine canyon system created an efficient method for deep sea burial of freshly produced organic rich material our results shed light on the ephemeral transport of organics within a submarine canyon system on an active tectonic margin

geology and geomorphology control suspended sediment yield and modulate increases following timber harvest in temperate headwater streams abstract suspended sediment transport is an important contributor to ecologic and geomorphic functions of streams however it is challenging to generalize predictions of sediment yield because it is influenced by many factors in this study we quantified the relevance of natural controls e g geology catchment physiography on suspended sediment yield ssy in headwater streams managed for timber harvest we collected and analyzed six years of data from 10 sites five headwater sub catchments and five watershed outlets in the trask river watershed western oregon united states we used generalized least squares regression models to investigate how the parameters of the ssy rating curve varied as a function of catchment setting and whether the setting modulated the ssy response to forest harvesting results indicated that the highest intercepts of the power relation between unit discharge and ssy were associated with sites underlain primarily by friable rocks e g sedimentary formations the greatest increases in ssy after forest harvesting up to an order of magnitude also occurred at sites underlain by the more friable lithologies in contrast basins underlain by resistant lithologies intrusive rocks had lower ssy and were more resilient to management related increases in ssy as such the impact of forest management activities e g use of forested buffers building of new roads on the variability in ssy was primarily contingent on catchment lithology sites with higher ssy or harvest related increases in ssy also generally had a lower mean elevation and slope b greater landscape roughness and c lower sediment connectivity we used principal component analysis pca to further explore the relationship between ssy and several basin physiographic variables the pca clearly separated sites underlain by friable geologic units from those underlain by resistant lithologies results are consistent with greater rates of weathering and supply of sediment to headwater streams in catchments with more friable lithologies and limited sediment supply in catchments underlain by resistant lithologies we hypothesize that a similar framework may aid in predicting the overall ssy of a catchment as well as its susceptibility to increases in ssy following forest harvesting

erosion rates for taiwan mountain basins new determinations from suspended sediment records and a stochastic model of their temporal variation abstract we estimate erosion rates from suspended sediment records for 11 basins in the eastern central range ecr of taiwan using methods based on mean measured sediment discharge a rating curve of sediment and water discharge and a rating curve corrected for periods of limited sediment due to the lack of landslide supplied sediment the preferred method for any basin depends on record length and sampling frequency with higher quality records being analyzed by the latter method erosion rate estimates range from 2 2 to 8 3 mm yr for records with varying sampling frequencies and durations between 8 and 27 yr this variation in erosion rates does not seem to reflect lithology tectonic environment or climate we interpret the variation in terms of natural stochastic variation in water discharge and sediment supply to assess the quality of the erosion rate estimates and to better understand the dependence of uncertainty on the duration and frequency of sampling we construct a stochastic model of sedi

supply and removal of sediment in a landslide dominated mountain belt central range taiwan abstract a strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding we reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern central range of taiwan here the magnitude frequency distribution of landslides can be modeled by a robust power law but this scale invariance is not mirrored in the sediment discharge at the mountain front instead downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions the rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment removal of landslide debris is a function of the transport capacity of the stream at the site of entry thus there is a dual supply and transport control on sediment loads in bedrock floored streams over a monitoring period of 25 yr the bulk of the sediment leaving the mountain bel

review of erosion dynamics along the major n s climatic gradient in chile and perspectives abstract chile is an elongated country running in a north south direction for more than 30 along a subduction zone its climate is progressively wetter and colder from north to south this particular geography has been used positively by a growing number of studies to better understand the relationships between erosion processes and climate land use slope tectonics volcanism etc here we review the erosion rates factors and dynamics over millennial to daily periods reported in the literature in addition 21 new catchment mean erosion rates suspended sediment and 10be are provided and previous suspended sediment derived erosion rates are updated a total of 485 local and catchment mean erosion rates are reported erosion rates vary between some of the smallest values on earth 10 5 mm a to moderate values 0 5 mm a compared to other active ranges this review highlights strong limitations concerning the quantification of local erosion factors because of uncertainties in sampling point location slope and rainfall data for the mean erosion rates e for the millennial and decennial catchments a model of the form e s 1 s 0 6 2 r with 0 3 0 8 accounts for 40 to 70 of the erosion variance confirming a primary role of slope s compared to precipitation rate r over this time scale over the long term this review points to the long 5 to 10 ma response time of rivers to surface uplift in north central arid chile over millennia data provide evidence for the progressive contribution of extreme erosion events to millennial averages for drier climates as well as the link between glacier erosion and glacier sliding velocity in this period of time a discrepancy exists between the long term offshore sedimentological record and continental decennial or millennial erosion data for which no single explanation appears still little information is available concerning the magnitude of variation of millennial erosion rates over centuries data show the variable role of groundwater in the dynamics of suspended load and document a decrease in erosion over hundreds of years probably associated with historical harvesting

constraining the transport time of lithogenic sediments to the okinawa trough east china sea the transport time of siliciclastic sediments from their continental sites of formation to their final location of deposition on the seafloor is an important parameter bearing on land sea interactions climate variability and understanding of marine sediment record 234u 238u activity ratios of the lithogenic fraction from late quaternary sediment deposited in the okinawa trough east china sea were reported in this study on basis of 234u 238u activity ratios the comminution ages and transport times were calculated using recoil loss factors f derived from different equations based on grain size distribution the transport times were longer approximately 200 100 kyr for the okinawa trough sediments deposited between 27 and 14 ka decreased gradually between 14 and 7 ka and stayed relatively short 100 kyr thereafter mineralogical geochemical and isotopic evidences indicate that changes in sediment transport time correspond well with the shift of sediment provenance predominantly from asia s interior prior to 14 ka to taiwan island after 7 ka this study offers the first and robust constraint on time scale of sediment transport process in east asia marginal sea which is constrained by unique sediment source to sink transport pattern the result illustrates the potential of this approach to decipher climate related changes in the mode of supply of lithogenic sediment to marginal seas it also highlights current difficulties in obtaining quantitative estimates of comminution age mostly because of uncertainties in estimating the recoil loss factor

a detrital heavy mineral viewpoint on sediment provenance and tropical weathering in se asia abstract understanding heavy mineral preservation is important for interpreting generation pathways provenance and geochemistry of sediments despite this many assumptions about heavy mineral stability are based on ancient strata and few studies consider modern sediments particularly those in tectonically active tropical areas such as se asia we report new heavy mineral data on 69 river sand samples from the malay peninsula and sumatra in which one aim was to find provenance indicators specific to these areas identifications were performed using optical microscopy and confirmed with sem eds in the malay peninsula heavy minerals record granitic and contact metamorphic provenance variable amounts of zircon tourmaline hornblende andalusite epidote monazite rutile and titanite and minor amounts of pyroxene apatite anatase garnet diaspore colourless spinel cassiterite and allanite are typical of this source area the composition of assemblages from sumatra indicates contributions from two major sources the modern volcanic arc i and the basement ii abundant pyroxene particularly hypersthene up to 70 is diagnostic of the volcanic arc source vesuvianite garnet andalusite tourmaline chrome spinel rutile anatase and corundum are present only in small amounts

geochemistry of river borne clays entering the east china sea indicates two contrasting types of weathering and sediment transport processes the east china sea is characterized by wide continental shelf receiving a huge input of terrigenous matter from both large rivers and mountainous rivers which makes it an ideal natural laboratory for studying sediment source to sink transport processes this paper presents mineralogical and geochemical data of the clays and bulk sediments from the rivers entering the east china sea aiming to investigate the general driving mechanism of silicate weathering and sediment transport processes in east asian continental margin two types of river systems tectonically stable continental rivers and tectonically active mountainous rivers coexist in east asia as the direct weathering products clays can better reflect the silicate weathering regimes within the two river systems provenance rock types are not the dominant factor causing silicate weathering intensity difference existed in the east asian rivers the silicate weathering intensity of tectonically stable river basins is primarily driven by monsoon climate and the sediment transfer is relatively slow because of natural trapping process and increasing damming effect the geochemistry of these river borne sediments can thus indicate paleo weathering intensities in east asian continent in contrast silicate weathering intensity in tectonically active mountainous rivers is greatly limited by strong physical erosion despite the high temperature and highest monsoon rainfall the factors controlling silicate weathering in tectonically active catchments are complex and thus it should be prudent to use river sediment records to decipher paleoclimate change these two different silicate weathering regimes and sediment transport processes are manifestations of the landscape evolution and overall dominate the sedimentation in asian continental margin

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

frequent sediment density flows during 2006 to 2015 triggered by competing seismic and weather events observations from subsea cable breaks off southern taiwan at least 17 subsea telecommunications cables cross the gaoping canyon and manila trench system in the strait of luzon between taiwan and the philippines there cable breaks record rapid 5 16 ms 1 long run out 300 km sediment density flows triggered by earthquakes and typhoons four major cable breaking events have occurred in the last decade in 2006 the pingtung ml 7 0 earthquakes formed up to 3 individual flows some of which ran out for up to 460 km in 2009 typhoon morakot generated two sediment flows the first was triggered by hyperpycnal river discharge whereas a second flow formed 3 days later possibly due to failure of recently deposited flood sediment in upper gaoping canyon a flow in 2010 formed during a swarm of ml 3 5 earthquakes that followed the ml 6 4 jiashian earthquake finally typhoon soudelor of 2015 caused the gaoping river to form a hyperpycnal plume that failed to break cables at 2600 m depth but broke at least 6 cables in deeper water the 2006 pingtung earthquakes produced the largest sediment flow s that produced 22 cable breaks the other events were less destructive with each causing 6 9 breaks sources of the sediment flows varied with the triggering mechanism those associated with hyperpycnal discharges probably began near the mouth of the gaoping river in contrast earthquake triggered landslides and subsequent sediment density flows formed anywhere on the adjacent continental margin flow speeds generally declined with increased run out lower seabed slope and increased channel width most variability 7 20 ms 1 was observed over the 0 4 1 0 slopes of gaoping canyon but speeds were mainly restricted to 5 8 ms 1 in the 0 3 sloping manila trench the 2006 2015 period of frequent cable damaging flows is the first for the past two decades or longer in the absence of evidence for increased seismic or anthropogenic activity this disruptive period may reflect increased typhoon intensity and fluvial sediment discharge such typhoon related flows may complicate interpretation of palaeo seismic records derived from turbidites in such settings

short term changes in seafloor character due to flood derived hyperpycnal discharge typhoon mindulle taiwan july 2004 during typhoon mindulle in early july 2004 the choshui river central western taiwan discharged similar to 72 mt of sediment to the eastern taiwan strait peak concentrations were g 200 g l similar to 35 40 of which was sand box core samples and chirp compressed high intensity radar pulse sonar records taken just before and after the typhoon indicate that the hyper pycnal sediment was first deposited adjacent to the mouth of the choshui subsequently resuspended and transported northward via the taiwan warm current and redeposited as a patchy coastal band of mud dominated sediment that reached thicknesses of 1 2 m within megaripples within a month most of the mud was gone probably continuing its northward transit but more mud appeared in late august in response to typhoon aere following autumn and winter storms the entire nearshore area was again sand dominated by early spring

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

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

typhoon and earthquake enhanced concentration and inventory of dissolved and particulate trace metals along two submarine canyons off southwestern taiwan abstract the influence of typhoon and earthquake events on the distributions of dissolved and particulate trace metals al fe mn cd cu pb zn is evaluated along the gaoping canyon and fangliao canyon in a tectonically active margin off southwestern taiwan the fangliao canyon was mightily struck by a large pingtung earthquake ml 7 0 in winter when terrestrial inputs were insignificant this large earthquake clearly enhanced the concentration and inventory of total suspended matter tsm dissolved and particulate metals by 2 5 fold in fangliao canyon and nearby gaoping canyon as compared to those in normal winter conditions the gaoping canyon is typically inundated with massive amounts of terrestrial materials during summer typhoons from the mountainous gaoping river strong contrast of particle and metal distributions can be found between summer and winter and between typhoon and regular summer periods in the gaoping canyon which was apparently caused by various strengths of river inputs followed by sediment resuspension and lateral advection at intermediate and near bottom depths along the canyon the water column and canyon wide inventories of tsm dissolved and particulate metals increased up to 2 fold higher during the post typhoon period than during the rainy period in summer in the gaoping canyon after extreme events most metals tend to increase their release into the dissolved phase through the increase of tsm concentration in addition to huge river inputs during typhoon both typhoon and earthquake induce energetic sea conditions that cause sediment resuspension and enhance the concentration and inventory of particles and metals in submarine canyons

modeling the sediment yield from landslides in the shihmen reservoir watershed taiwan landslides generate enormous volumes of sediment in mountainous watersheds however quantifying the downstream transport of landslide derived sediment remains a challenge landslide erosion and sediment delivery to the shihmen reservoir watershed in taiwanwas estimated using empirical landslide frequency area and volume area relationships empirical landslide runout models and the hydrological simulation programfortran hspf landslide erosion rates ranged from 0 4mmyr to 2 2mmyr during the period 1986 2003 but increased to 7 9mmyr following typhoon aere in 2004 the percentage of landslide sediment delivered to streams decreased from 78 during the period 1986 1997 to 55 in 2004 although the delivery ratio was lower the volume of landslide sediment delivered to streams was 2 81 10mgyr in 1986 1997 and 8 60 10mgyr in 2004 model simulations indicate that only a small proportion of the landslidematerial was delivered downstream an average of 13 of the landslide material delivered to rivers was moved downstream during the period 1986 1997 in 2004 the period including typhoon aere the annual fluvial sediment yield accounted for approximately 23 of the landslide material delivered to streams in general the transfer of sediment in the fluvial system in the shihmen reservoir watershed is dominantly transport limited the imbalance between sediment supply and transport capacity has resulted in a considerable quantity of landslide material remaining in the upper stream regions of the watershed copyright 2012 john wiley sons ltd

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

deep sea sedimentation offshore eastern taiwan facies and processes characterization recent sedimentary facies and processes along the offshore slope of east taiwan are investigated using a large set of geophysical and sedimentological data the taiwan orogen is often considered as one of the most tectonically active regions in the world and also suffers important climatic activity with an average of four typhoons per year we have mapped in details the morphosedimentary features and characterized the sedimentary facies along offshore eastern taiwan there we show that the slope is driven by a variety of erosional processes from mass wasting to turbidity current mass movements such as slides or mass transport deposits mtds are ubiquitous and affect the whole east coast off taiwan detailed core investigations such as grain size analysis chemical and mineralogical composition revealed that turbidite facies range from thin fine grained turbidites to thick massive turbidite facies the detailed analysis of turbidite beds allow us to discuss the controlling factors of turbidity current generation turbidity currents represent an important sedimentary process that governs the slope morphology off east taiwan triggering mechanisms likely range from slope instabilities related to earthquakes shaking to failure relative to climatic controlled pulses of sediment supply we propose that at least two end members are characteristics in our turbidite records in term of controlling factor 1 turbidity currents likely generated by tectonic activity and earthquakes shaking in particular and 2 turbidity currents likely generated by climatic activity such as typhoon induced floods

particle dynamics of the surface intermediate and benthic nepheloid layers under contrasting conditions of summer monsoon and typhoon winds on the boundary between the taiwan strait and east china sea abstract two shipboard surveys of hydrographics and sediment dynamics were conducted off the mouth of minjiang the min river in july 2012 under contrasting summer monsoon and typhoon wind conditions observations included profiles of conductivity temperature depth fluorescence and suspended particle volume concentration and current velocity in addition water samples were taken for the analyses of mass concentration poc and chlorophyll of suspended sediment seafloor sediment samples were also taken for grain size analysis nepheloid layers nls were observed at surface intermediate and benthic depths snl inl bnl respectively the nl dynamics under the two wind conditions were mainly controlled by 1 the presence of the minjiang river plume and terrigenous material it carries 2 water column stability affected by wind current and waves 3 current induced resuspension of seafloor sediment and 4 physically coupled biological activities the wind field was the major forcing controlling the observed flow field and the upper water column stability in the typical summer condition southerly winds induced offshore directed currents enhancing the seaward dispersal of the minjiang river plume facilitating water column stratification thereby forming 3 nls in the water column phytoplankton growth was enhanced by terrigenous material and sunlight the suspension of the seafloor sediment was the one of the major sources for suspended particles in these nls furthermore the c n ratio of poc in the three nls is 5 72 almost identical to the redfield ratio indicating their predominant marine origin conversely under typhoon related northerly winds the offshore spread of the river plume was restricted the reduced riverine input and enhanced mixing resulted in the disappearance of the snl elevated turbidity in the inl was largely due to the presence of phytoplankton while the bnl was comprised of sediment resuspended off the seafloor and from horizontal advection our results suggest that the presence of the river plume from the minjiang at the study site sets the condition for the snl dynamics the dynamics of inl and bnl were dominated by the wind field and to a lesser degree the wave field and tidal current

accumulation of terrestrial organic carbon on an active continental margin offshore southwestern taiwan source to sink pathways of river borne organic particles abstract sediment samples 213 sites collected from the tectonic active continental margin offshore southwestern taiwan were analyzed for grain sizes organic carbon nitrogen and carbon isotopic composition to obtain mass accumulation rate of terrestrial organic carbon and carbon budget to evaluate fate of terrestrial organic carbon from small mountainous rivers on the continental margin offshore southwestern taiwan terrestrial organic carbon accumulation rates range from 0 29 to 45 6 g c m 2 yr 1 with a total accumulation budget of 0 063 mt yr 1 which accounts for less than 13 of total river particulate organic carbon loads exported from the adjacent rivers the gaoping a k a kaoping erhjen and tsengwen rivers this low burial efficiency of terrestrial organic carbon demonstrated that a majority of river borne particles together with organic materials was moved away from the study area for the river borne particles from the gaoping river a pair of depocenters in the upper slope flanking the gaoping submarine canyon are the locations where the maximum tc org accumulation rate were observed which hold up to 45 0 016 mt yr 1 of the calculated accumulation found in the study region on the other hand the occurrence of higher fraction terrestrial organic carbon in the upper and middle gaoping submarine canyon suggests that a majority of particulate organic carbon of the gaoping river was transported directly into the deep sea basin through the gaoping submarine canyon our results demonstrated that active margin with narrow shelf and slope is not an efficient sink for the large amount of terrigenous organic carbon supplied by the small rivers but a transient environment for these river derived particles

sea level responses to rapid sediment erosion and deposition in taiwan abstract numerous studies have shown that sediment deposition can perturb sea level by several meters over millennial timescales by modifying the gravity field crustal elevation and sediment thickness relatively few studies have focused on the complementary role of erosion on sea level change despite its effects on the same quantities partly because many rapidly eroding mountains are too far from shorelines to strongly perturb sea level at the coast taiwan a mountainous island eroding rapidly within tens of km of the coast offers an opportunity to investigate the joint influences of rapid onshore erosion and rapid offshore deposition on sea level change here we develop a sediment loading history for taiwan since the previous interglacial 120 ka by compiling published erosion and deposition rate measurements and by applying a geometric marine sediment deposition and compaction model for sites without deposition rate measurements we use the resulting sediment redistribution history to drive sea level responses in a gravitationally self consistent sea level model our simulations show that the effects of rapid onshore erosion outweigh the effects of rapid offshore deposition along taiwan s east coast along the east coast of taiwan sediment redistribution induces rapid sea level fall a response that differs in sign from the coastal sea level rise induced by rapid sediment redistribution in many other river systems around the world the spatial extent of the modeled sea level fall is sensitive to the earth model particularly the effective elastic thickness of the lithosphere a sensitivity that we describe in further detail in the discussion these results suggest that sediment redistribution could have generated sea level changes of 10 m on the east coast of taiwan since 10 ka and 100 m since 120 ka this can account for some of the discrepancy between observed and modeled paleo sea level marker elevations which reduces estimates of tectonically driven rock uplift rates inferred from the elevation differences between paleo sea level markers and modeled sea level this highlights the importance of accounting for erosional unloading in interpretations of paleo sea level reconstructions and associated estimates of tectonically driven uplift rates

morphological evolution of the south passage in the changjiang yangtze river estuary china abstract estuarine morphology of the world s major large rivers have experienced great changes due to intensive anthropogenic activities and natural forcings especially in the changjiang estuary located at the end of the longest river in asia this study focuses on morphological changes of the south passage sp which is one of the 4 channels in the branching estuary at the mouth of the changjiang yangtze river china a multivariate analysis technique of empirical orthogonal eigen function eof method was used to examine the major modes of change in the long term over 26 years water depth data the results show that the morphological changes at the sp could be divided into two stages between 1987 and 1997 the sp had a single stable channel with closure of a cross channel between 1997 and 2012 sp displayed southeastward elongation of a spit into the main channel and westward shoal incision by a cross channel the opening of the sp developed a two channel morphology which stabilized and showed infilling during 2003 2012 the average deposition rate was 10 cm yr in the past 30 years the most dominant morphological changes of sp included the deposition around the upstream opening of the channel the second most important pattern of morphological change was related to the downstream elongation retreat and lateral migration of the spit of the jiangyanan shoal which resulted in the two channel configuration of the sp additionally these morphological changes were not triggered by the decline of the distal sediment source from the upstream but due to the input of proximal sources of the shoal at the upstream opening of the sp and spill over sediment from the north passage via a short cut channel

bajada de rahue province of neuquen argentina an interstadial deposit in northern patagonia abstract pollen and diatom analyses of a radiocarbon dated lacustrine section in the temperate andean region of argentina rahue province neuquen suggest interglacial type climatic conditions between 27 000 and 33 000 yr b p with environments that resemble the modern conditions at the locality this finding correlates with a woodland record from central chile interpreted as reflecting conditions substantially warmer and drier prior to 27 000 yr b p than during the following full glacial period it also appears to relate to the global paleoclimatic scheme derived from deep sea records suggesting interhemispheric synchroneity of such broad scale palaeoclimatic phases

climate driven bedrock incision in an active mountain belt measurements of fluvial bedrock incision were made with submillimeter precision in the east central range of taiwan where long term exhumation rates and precipitation driven river discharge are independently known they indicate that valley lowering is driven by relatively frequent flows of moderate intensity abrasion by suspended sediment is an important fluvial wear process and channel bed geometry and the presence of widely spaced planes of weakness in the rock mass influence erosion rate and style

organic carbon fluxes to the ocean from high standing islands the transfer of terrestrially derived yet poorly quantified organic carbon to the oceans is an important yet unagreed upon proportion of the world s carbon budget the few data that exist suggest that high standing oceanic islands in the southwest pacific may make important contributions to the overall terrestrial flux of particulate organic carbon poc to the oceans we have determined the poc flux from several streams in new zealand with those data and previous measurements from taiwan and papua new guinea we estimate the poc flux from high standing islands in the southwest pacific to be 48 1012 g c yr 1 a value slightly lower than previous estimates these islands which make up only 3 of earth s landmass contribute 17 35 of the estimated poc entering the world s oceans annually and thus may be important sources of terrestrial carbon to the ocean anthropogenic activities especially deforestation and forest harvesting have probably exacerbated the natural flux few to no data exist for many of these islands and thus a more detailed assessment awaits further measurements

stratigraphic modeling of the western taiwan foreland basin sediment flux from a growing mountain range and tectonic implications abstract sediment flux signals from source to sink in foreland basins preserve a record of tectonics sea level and climate through erosion and sedimentation however longitudinal sediment transport often occurs in foreland basins thus removing part of the orogenic material flux from foreland basin records here we use mass balance calculation and stratigraphic simulations of sediment fluxes for the taiwan orogen to provide an order of magnitude estimate of how much orogenic material may bypass a foreland basin our results indicate a significant potentially more than 50 mismatch between sediment volume currently preserved in the basin and the amount of material presumably eroded from the orogen since the onset of collision in taiwan this suggests either a significant overestimation of average erosion rates over the period concerned with orogenic development of taiwan or it supports previous paleogeographic work suggesting that longitudinal sediment transport in the paleo taiwan strait served as a major bypass conduit of importance for the establishment of a steady state orogen we identify candidate submarine topography in the south china sea that may preserve taiwan s missing erosional mass

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

major sinks of the changjiang yangtze river derived sediments in the east china sea during the late quaternary the east china sea ecs is a typical marginal sea located between the eurasian con tinentandwestpacificocean inthisstudy wereviewstate of the artresearchprogressonthepos sible sinks of the changjiang derived sediments in the ecs during the late quaternary the major sinks of these sediments in the ecs are on the outer shelf and the okinawa trough during the last glacial maximum corresponding to a lowstand of sea level during the deglacial marine transgres sion the gently dipping shelf was rapidly inundated and strong tides prevented fine sediment from deposition on the open shelf resulting in the development of a unique tidal sand ridge sys tem with sea level reaching the present situation and the modern marine environment being com pleted in the early holocene the changjiang sediments mostly accumulated in the river s estuary to build a large delta with only a fraction reaching the inner shelf and coastal embayments the late quaternary changes in monsoon climate induced river flux sea level and oceanic circulation primarily controlled the source to sink transport of the changjiang sediments in the ecs and fur ther determined the stratigraphic framework and sedimentary facies on the shelf

clay mineral compositions of sediments in the gaoping river sea system implications for weathering sedimentary routing and carbon cycling abstract small mountainous rivers smrs play a crucial role in the global sediment and carbon cycle by rapid transfer of huge particulate and dissolved loads into the sea gaoping river sea system is a good representative of smrs in oceania having an extreme high denudation rate 15 000 t km 2 yr 1 and a high burial efficiency of terrestrial particulate organic carbon poc in the gaoping submarine canyon gpsc however it is contentious whether silicate weathering or poc burial plays more important role in long term carbon cycling in such a high active orogen clay minerals of fluvial sediments not only act as an important carrier of poc but also encode valuable information of weathering regimes on land and dispersal routes in the seas to uncover these informations surface and core sediments are systematically collected from the gaoping river sea system for clay mineral analysis comparative studies are carried out on the basis of new results and vast published data to better understand weathering processes and products in oceanian islands and southeast asian continent we find that clay mineral compositions in the gaoping river gpr and other taiwan rivers are a legacy from provenance rocks in the alpine reach characterized by predominant illite and chlorite and limited compositional change throughout the river courses these sharply contradict the downstream increase in compositional complexity rich in kaolinite and smectite and chemical weathering intensity in southeast asian large rivers because of strong hydrolysis and active sediment recycling at the lowland reach with extensive floodplains high consistency of clay mineral compositions is also observed in the interior and exterior of gpsc careful examination shows that a slight offshore decrease in cumulative illite and chlorite content is accompanied by a slight increase in exotic clay mineral inputs by ocean circulations the combination of this finding with previously reported data on the offshore change in 13corg and 14corg values suggests that petrogenic poc predominates in the river dominated gaoping continental margin with high preservation efficiency due to its tight bandage with clay minerals moreover a tardy response of chemical weathering fluxes to high elevated physical erosion rates is remarkably examined in the oceanian and global river gauging data we therefore postulate that rapid transfer and high burial efficiency of terrestrial poc in the tectonically active high standing islands and their adjacent continental margins play much more important role in the long term carbon cycle than silicate weathering

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

trace metal fluxes to the ocean the importance of high standing oceanic islands 1 trace metal analyses of river channel sediments from taiwan and new zealand provide new estimates for global budgets of trace metal inputs to the world s ocean mean trace metal values from high standing island river sediments are less chemically weathered than observed in sediments collected from large continental rivers and more similar to upper continental crust ucc values our mean values for cu mn co and pb are similar to the ucc zn ni and cr are more highly enriched compared to ucc values our new estimates of global trace metal budgets combining previous estimates with these new data show that geochemical fluxes of metals into the oceans are lower than previous estimates ranging from 9 lower for co to 24 lower for cu

early interglacial carbonate dilution events in the south china sea implications for strengthened typhoon activities over subtropical east asia abstract a compilation of many late quaternary marine sediment records from the northern south china sea scs continental slope confirms 15 50 reductions in sedimentary calcium carbonate concentrations between 11 0 and 8 5 ka bp in the early holocene this low carbonate event occurred at a time when the regional sea level rose from 50 m to 10 m which drowned large areas of continental shelves especially those near and within the taiwan strait this event is associated with a significant increase in bulk sedimentation rates on the upper continental slope and the relative abundance of fine grained detritus sediment provenance analyses suggest a dominant terrigenous input from taiwan and a minor contribution from luzon during the low carbonate event similar to the background terrigenous deposition in other periods of the holocene two comparable low carbonate events respectively from the beginning of marine isotope stages 5 5 and 7 3 have also been recognized pointing to similar causal factors while carbonate dissolution and carbonate accumulation rate should not have been responsible increased terrigenous input and dilution is considered as the main cause for the recurrent low carbonate events in early interglacials we further hypothesize that during early interglacials fluvial sediment discharge from taiwan and luzon intensified due to stronger typhoon activities and massive fine grained sediments from these two end members may have been transported to the northern scs continental slope via surface and deep ocean currents the conjecture of strengthened typhoon activities over east asia during the early holocene is supported by high ocean heat contents in the west pacific warm pool area with the prevailing la nina like conditions

deciphering the geology of some darriwilian sandbian ordovician ghost formations in the uk and north america using olistoliths in marine debris flows olistostromes with calcareous olistoliths are rare components in the ordovician successions in nw europe and north america having been described from only a small number of localities one of the best exposed but least known is in the garn formation in coastal outcrops in anglesey in northwestern wales here in the graptolite bearing shales of the garn formation there are numerous limestone olistoliths that are derived from an otherwise unknown ghost formation whose original depositional site remains an enigma these olistoliths contain a baltoscandian type of conodont fauna that is otherwise unknown in wales and england it represents the baltoniodus variabilis subzone of the amorphognathus tvaerensis zone similar but slightly older conodont faunas are recorded from olistoliths in the tweeddale member of the shinnel formation in southern scotland and in probable olistoliths of the cobbs arm limestone in northeasternmost newfoundland approximately coeval conodont faunas are present in calcareous olistoliths in the woods hollow shale of west texas and the womble shale in the ouachita mountains of arkansas usa lithological and conodont evidence indicates that the calcareous olistoliths were derived from carbonate sediments deposited in relatively shallow water it is concluded that the study of ghost formation olistoliths may provide otherwise unavailable but important data bearing on the marine depositional history of a particular region

denudation rate changes along a fast eroding mountainous river with slate headwaters in taiwan from 10 be meteoric 9 be ratios

geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers 1 to assess the role that erosion processes play in governing the character of particulate organic carbon poc discharged from small mountainous and upland rivers a suite of watersheds from oregon california and new zealand was investigated the rivers share similar geology tectonic setting and climate but have sediment yields that range over 3 orders of magnitude the 14c age of the poc loads is highly correlated with sediment yield carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern plant and ancient rock derived oc at lower yields modern plant oc dominates the material delivered to the river by sheetwash and shallow landsliding with increasing yield a progressively larger part of the poc is contributed directly from bedrock erosion via deep gully incision our results support the inference that active margin watersheds are important sources of aged poc to the ocean

the isotopic composition of particulate organic carbon in mountain rivers of taiwan small rivers draining mountain islands are important in the transfer of terrestrial particulate organic carbon poc to the oceans this input has implications for the geochemical stratigraphic record we have investigated the stable isotopic composition of poc 13corg in rivers draining the mountains of taiwan in 15 rivers the suspended load has a mean 13corg that ranges from 28 1 0 8 to 22 0 0 2 on average 37 samples per river over the interval of our study to investigate this variability we have supplemented suspended load data with measurements of poc in bedrock and river bed materials and constraints on the composition of the terrestrial biomass fossil poc in bedrock has a range in 13corg from 25 4 1 5 to 19 7 2 3 between the major geological formations using coupled 13corg and n c we have found evidence in the suspended load for mixing of fossil poc with non fossil poc from the biosphere in two rivers outside the taiwan central range anthropogenic land use appears to influence 13corg resulting in more variable and lower values than elsewhere in all other catchments we have found that 5 variability in 13corg is not controlled by the variable composition of the biomass but instead by heterogeneous fossil poc in order to quantify the fraction of suspended load poc derived from non fossil sources fnf as well as the isotopic composition of fossil poc 13cfossil carried by rivers we adapt an end member mixing model river suspended sediments and bed sediments indicate that mixing of fossil poc results in a negative trend between n c and 13corg that is distinct from the addition of non fossil poc collapsing multiple fossil poc end members onto a single mixing trend as an independent test of the model fnf reproduces the fraction modern fmod in our samples determined from 14c measurements to within 0 09 at the 95 confidence level over the sampling period the mean fnf of suspended load poc was low 0 29 0 02 n 459 in agreement with observations from other mountain rivers where physical erosion rates are high and fossil poc enters river channels the mean 13cfossil in suspended poc varied between 25 2 0 5 and 20 2 0 6 from catchment to catchment this variability is primarily controlled by the distribution of the major geological formations it also covers entirely the range of 13corg found in marine sediments which is commonly thought to derive from mixing between marine and terrigenous poc if land sourced poc is preserved in marine sediments then changes in the bulk 13corg observed offshore taiwan could instead be explained by changes in the onshore provenance of sediment the range in 13corg of fossil organic matter in sedimentary rocks exposed at the surface is large and given the importance of these rocks as a source of clastic sediment to the oceans care should be taken in accounting for fossil poc in marine deposits supplied by active mountain belts

water and sediment discharge from small mountainous rivers taiwan the roles of lithology episodic events and human activities national science council of taiwan nsc96 2628 m 001 028 u s national science foundation and naval oceanographic office

distribution of organic carbon and lignin in soils in a subtropical small mountainous river basin abstract as a unique biomarker of terrigenous organic matter om lignin has provided valuable information for tracing the sources of om in land to ocean transfer oceanian small mountainous rivers smrs are characterized by extremely high erosional rate and quick change in microclimate within watershed which may potentially affect the distribution of soil oc and lignin concentrations and compositions bulk oc and lignin were determined on surface soils and soil profiles from a taiwanese smr jhuoshuei river and nearby region along a large altitudinal gradient 3 3176 m to investigate the influence of microclimate on soil oc and lignin both surface soils oc and lignin increased in higher altitude suggesting higher preservation of om in the cold region variations in lignin vegetation indices s v and c v in surface soils generally reflect the vegetation change in this river basin and were more affected by precipitation seasonality than mean annual precipitation lignin concentration decreased with depth along with a decrease in s v and c v and an increase in degradation indices ad al v and dhba v reflecting a decreased input and or biodegradation of lignin in subsoils our survey on soil lignin in taiwan smr provided the basis for utilizing lignin to trace the source of oc in land to ocean transfer as well as paleo climate and paleo vegetation reconstruction study in taiwan smrs

the danube river inception evidence for a 4 ma continental scale river born from segmented paratethys basins before reaching the black sea the danube river passes through a string of para tethyan vienna pannonian and western and eastern dacian basins the key question is when and how did the danube river became a continental scale river with a drainage similar to present new data presented here show that the late miocene deep water strata in the black sea have a significant sediment source and depositional style change at about 4 ma however the presence of active miocene basins within the danube catchment raises questions about the timing of danube river inception and whether the upstream palaeogeography would have allowed or disallowed delivery of large sediment volumes to the deep water black sea stratigraphic analyses in the pannonian and dacian basins reveal a phase of coeval sedimentary fill of the basins along the danube at about 4 ma this multi basin observation points to a concurrent basin fill model rather than the basin fill and spill or messinian type lowstand models previously proposed for danube inception this article is protected by copyright all rights reserved

average landslide erosion rate at the watershed scale in southern taiwan estimated from magnitude and frequency of rainfall abstract this study calculated the long term average landslide erosion rate in the kaoping river watershed in southern taiwan and investigated the relative importance of extreme rainfall events on landslide erosion the method followed three steps first calculating landslide volumes for 10 rainfall events from a multi temporal event based landslide inventory second estimating the frequency of landslide generating rainfall by using hydrologic frequency analyses and third combining the two sets of data to estimate the average landslide erosion rate results of the study showed that the average landslide erosion rate is 2 65 5 17 mm yr 1 corresponding well to rates reported in other studies using other methods the study also found that extreme intensive rainfall events play a more important role on landslide erosion than frequent moderate rainfall events extreme rainfall maximum 24 h rainfall 600 mm contributes 64 79 of the average landslide erosion rate moreover the natural variation of landslide erosion magnitudes is extremely large and can cause significant uncertainty in estimating the landslide erosion rate from total landslide volume this study found 1 2 mm yr 1 of uncertainty based on simulation results involving a hypothetical 100 year landslide inventory in summary this study demonstrates the importance of extreme rainfall events on landslide erosion and the method proposed in this study is capable of calculating a reliable estimate of average landslide erosion rate in areas with insufficient landslide records

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

provenance weathering and erosion records in southern okinawa trough sediments since 28ka geochemical and sr nd pb isotopic evidences abstract geochemical and sr nd pb isotopic compositions of the detrital sediments from odp hole 1202b and taiwan rivers were measured in this study aiming to reveal changes in sediment provenance in the southern okinawa trough sot since 28 ka and to examine the weathering and sediment transport processes in response to monsoon climate variability large variations in sr nd pb isotopic ratios at 11 9 ka suggest changes in detrital sediment provenance in the sot from a dominance of the paleo changjiang yangtze river and or continental shelf sediment during the late deglaciation and to west taiwan rivers since 9 5 ka volcanic rocks and eastern taiwan sediments have not significantly contributed to the sot the large shift in sediment provenance during the early holocene marks a major change in oceanic circulation mainly caused by the intrusion of the kuroshio current into the trough clay mineral and geochemical proxies suggest that the taiwan derived sediments accumulated during the early mid holocene climate optimum ca 9 5 4 ka might be tightly related to the reworking of older altered sediments from terraces and floodplains rather than having experienced more intense silicate weathering than in the late holocene 4 0 ka overall silicate weathering in taiwan was greatly inhibited by accelerating sediment production and transfer from land to ocean caused by monsoon intensification in holocene our study illustrates that the radiogenic isotopic and geochemical compositions of fine grained detrital sediments are sensitive tools for fingerprinting sediment sources and for reconstructing changes in oceanic currents and monsoon climate in river dominated east asian continental margin

sediment accumulation and retention of the changjiang yangtze river subaqueous delta and its distal muds over the last century abstract mega deltas are major sinks of river borne sediments and important sources of terrigenous sediments for open shelves their evolution has far reaching impacts on adjacent coastal waters from the point of view of along shelf morphodynamics and biogeochemistry however the complex budgeting patterns of input storage bypass and final accumulation of sediment are still poorly understood the changjiang yangtze river in china is among the world s largest river systems not only in terms of water and sediment discharges but also the massive amount of sediment deposited in its subaqueous delta and distal muds here we discuss about the along shelf sediment redistribution in the changjiang subaqueous delta and distal muds csddm over the last century for the purpose of understanding its spatial diversity in detail we divided the study area into three spatially connected parts namely the changjiang subaqueous deltaic mud cjm the zhejiang inner shelf mud zjm and the fujian inner shelf mud fjm the concept of sediment retention index helps understand the overall evolution of this mega delta hydrological survey data from the peripheral rivers and short marine sediment cores are used to evaluate the amount of sediment supplied to and deposited in the study area the results show that over the last century the rate of sediment supply to the csddm reached 645 mt year 1 on average ranging between 535 and 725 mt year 1 while the total sediment deposition in the csddm reached 683 mt year 1 on average 390 976 mt year 1 with the ratio for the deposits in the cjm zjm and fjm being close to 3 5 2 as such the input and output of sediment were generally in balance the sediment retention indices are estimated to be 0 35 0 86 and 1 00 for cjm zjm and fjm respectively this study contributes to our knowledge of marine sediment fluxes facilitates a better understanding of the growth and development of mega deltas under system regime shifts and helps identify a sustainable development model for areas of high population density heavy economic activity and rapid urbanization

hyperpycnal sediment discharge from semiarid southern california rivers implications for coastal sediment budgets southern california rivers discharge hyperpycnal river density greater than ocean density concentrations of suspended sediment 40 g l according to buoyancy theory during flood events mostly during el nino southern oscillation enso conditions because hyperpycnal river discharge commonly occurs during brief periods hours to occasionally days mean daily flow statistics often do not reveal the magnitude of these events hyperpycnal events are particularly important in rivers draining the transverse range and account for 75 of the cumulative sediment load discharged by the santa clara river over the past 50 yr these events are highly pulsed totaling only 30 days 0 15 of the total 50 yr period observations of the fate of sediment discharge although rare are consistent with hyperpycnal river dynamics and the high likelihood of turbidity currents during these events we suggest that much of the sediment load initially bypasses the littoral circulation cells and is directly deposited on the adjacent continental shelf thus potentially representing a loss of immediate beach sand supply during particularly exceptional events 100 yr recurrence intervals flood underflows may extend past the shelf and escape to offshore basins

near synchronous and delayed initiation of long run out submarine sediment flows from a record breaking river flood offshore taiwan subsea fiber optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides similar flows are inferred to form from major river floods whose sediment laden waters plunge and travel along the seabed however the complex initiation of flood related flows and their hazard potential have not been observed until now here we use cable fault data from the gaoping canyon manila trench off taiwan to show that a major river flood formed during typhoon morakot 2009 generated two long run out destructive sediment flows one during peak flood and the other 3 days later the latter flow was more damaging with speeds and run out similar to that of landslide triggered turbidity currents formed in the same catchment if the second flow was due to remobilized canyon sediment it occurred during low earthquake mw 2 0 activity suggesting other triggering mechanisms

rare earth elements in fine grained sediments of major rivers from the high standing island of taiwan thirty eight sediment samples from 15 primary rivers on taiwan were retrieved to characterize the rare earth element ree signature of fluvial fine sediment sources compared to the three large rivers on the chinese mainland distinct differences were observed in the ree contents upper continental crust normalized patterns and fractionation factors of the sediment samples the average ree concentrations of the taiwanese river sediments are higher than those of the changjiang and huanghe but lower than the zhujiang light rare earth elements lrees are enriched relative to heavy rare earth elements hrees with ratios from 7 48 to 13 03 we found that the variations in la lu ucc gd lu ucc and la yb ucc gd yb ucc are good proxies for tracing the source sediments of taiwanese and chinese rivers due to their distinguishable values our analyses indicate that the ree compositions of taiwanese river sediments were primarily determined by the properties of the bedrock and the intensity of chemical weathering in the drainage areas the relatively high relief and heavy rainfall also have caused the rees in the fluvial sediments from taiwan to be transported to the estuaries down rivers from the mountains and in turn delivered nearly coincidently to the adjacent seas by currents and waves our studies suggest that the ree patterns of the river sediments from taiwan are distinguishable from those from the other sources of sediments transported into the adjacent seas and therefore are useful proxies for tracing the provenances and dispersal patterns of sediments as well as paleoenvironmental changes in the marginal seas

effects of topography lithology rainfall and earthquake on landslide and sediment discharge in mountain catchments of southeastern taiwan abstract from 1996 through 2007 several heavy typhoons and earthquakes precipitated landslide hazards in southeast taiwan in the present study we analyze the impact of topography lithology rainfall and earthquakes on landsliding and sediment transport by quantifying the landslide ratio ratio of landslide area to catchment area and the sediment discharge for the sinwulu and luye upstream catchments of the peinan river the steep topography in these two catchments causes a large proportion of landslide ratios on slopes to exceeding 50 a condition which accelerates the delivery of landslide debris to the downslope channel the landslide ratios of 0 84 2 30 are obviously related to the rock strength and discontinuity density of the terrain but we find the magnitude of landsliding and sediment discharge to vary with the occurrence of earthquakes typhoon induced rainstorms generate the bulk of sediment discharge in the study catchments though the landslide debris is transported by the huge amounts of runoff produced by rainstorms a contributing factor is the recent occurrence of severe earthquakes which weakened the geomaterial leading in turn to further increases of fluvial sediment during subsequent typhoons additionally the finding that eventual reduction of unit sediment concentration after high magnitude earthquake events reveals that the downslope transport of landslide debris associated with earthquake activity and subsequent typhoon events precipitates a relatively short term 1 3 year increase of erosion rates in these two study areas in southeastern taiwan

the time scale of river sediment source to sink processes in east asia abstract knowledge of river sediment recycling provides important constraints on continent weathering and earth surface processes in this study we estimate the comminution age of sediments from the changjiang yangtze river and two small mountainous rivers in taiwan based on their lithogenic 234u 238u ratio the 234u 238u distributions in the changjiang catchment are overall related to sediment grain size and chemical weathering regime while 234u 238u ratios in taiwan rivers mainly depend on erosion denudation processes the comminution age constrains the time scale of sediment source to sink processes in catchments from sediment weathering denudation to transportation and finally deposition our results indicate that the comminution ages vary from 250 to 600 kyr for the changjiang sediments and 110 kyr for the taiwan sediments different comminution ages are associated with contrasting erosion and weathering regimes and diverse topography between the large changjiang catchment and small mountainous taiwan basins the longer comminution age of the changjiang sediment is an interacting effect of a longer erosion weathering history and sediment trapping effect and thus slow transfer rate created by broad floodplains and lakes in the middle and lower reaches the shorter comminution age of the taiwan sediment results from fast sediment denudation and transport associated with strong tectonic uplift typhoon climate and steep topography as these two major river systems dominate the sedimentology in east asia continent margin the distinct geological and topographical settings between the changjiang and taiwan river systems result in different sediment source to sink transport processes this work presents a systematic and quantitative constraint on the time scale of river sediment transfer process in east asia and also provides new insight into weathering regimes and sediment transport in monsoon climate dominated continent and island

the efficacy of stream power and flow duration on geomorphic responses to catastrophic flooding abstract geomorphologists have long studied the impacts of extreme floods yet the association between the magnitude of flow parameters discharge velocity shear stress or stream power and resulting geomorphic effectiveness remains vague and non deterministic attempts have been made to include flow duration and total expenditure of stream power in combination with peak unit stream power as important variables but there has been minimal exploration of this hydraulic combination taking advantage of tropical storm irene s rapid track through eastern vermont usa in late summer 2011 this paper presents the array of geomorphic responses to a short duration time to peak of

partitioning sediment flux by provenance and tracing erosion patterns in taiwan we critically evaluate the potential and limitations of an alternative way to calculate erosion rates based on petrographic and mineralogical fingerprints of fluvial sediments coupled with gauged sediment fluxes our approach allows us to apportion sediment loads to different lithological units and consequently to discriminate erosion rates in different tectonic domains within each catchment our provenance data on modern taiwanese sands indicate focused erosion in the backbone range and tananao complex of the retrowedge lower rates are inferred for the northern part of the island characterized by tectonic extension and for the western foothills in the prowedge the principal factor of uncertainty affecting our estimates is the inevitably inaccurate evaluation of total sediment load because only the suspended flux was measured another is the assumption that suspended load and bed load are derived from the same sources in fixed proportions additional errors are caused by the insufficiently precise definition of lithologically similar compositional end members and by the temporal variability of sediment composition at the outlet of each catchment related to the spatial variability of erosional processes and triggering agents such as earthquakes typhoons and landslides to evaluate the robustness of our findings we applied a morphometric technique based on the stream power model the results obtained are broadly consistent with local discrepancies ascribed to poorly constrained assumptions and choices of scaling parameters our local erosion estimates are consistent with gps uplift rates measured on a decadal timescale and generally higher than basin wide results inferred from cosmogenic nuclide and thermochronology data

estimating river sediment discharge to the ocean application to the eel margin northern california abstract hydrotrend a synthetic river discharge numerical model can simulate the natural variability daily annually and longer in the flux of water and sediment delivered to the coastal ocean the numerical model is designed to make discharge predictions based on climate even though field measurements of river flow are not available provided that appropriate assumptions are made regarding past climate the model can predict how a river may have behaved in the geological past sediment load is determined from a river s rating coefficients when applied to the flood dominated eel river northern california hydrotrend captures the intermonthly and interannual variability of discharge and loads over a century or more hydrotrend is applied to the ice age paleo eel river when sea level was lower and climate much cooler and wetter the paleo eel river at 18 000 year bp would see its hinterland runoff increase but not the magnitude of the peak discharges the post dicted sediment load of the paleo eel river was 25 greater than today s although basin precipitation was 45 greater and the hinterland area 4 greater through sea level lowering a method is provided to obtain sediment discharge rating coefficients for unmonitored modern rivers and paleo rivers the relationship q s g 1 2 h 3 2 a 1 2 provides for an estimate of a river s sediment load q s to within a factor of 3 over 7 orders of magnitude from knowledge of basin relief h and basin area a rating coefficients are determined from this estimate of q s and the power law rating curve q s aq b 1 where q is discharge

chemical indices cia and wip as proxies for integrated chemical weathering in china inferences from analysis of fluvial sediments abstract rivers play a key role in earth surface processes by weathering and eroding the upper continental crust under variable climate regimes how to quantitatively determine the chemical weathering intensity in the drainage basins using geochemistry of fluvial sediments remains unclear the chemical index of alteration cia and the weathering index of parker wip have been used worldwide as proxies to evaluate the chemical weathering intensity in large watersheds and in specific weathering profiles in this study concentrations of major oxides in the suspended particulate matter spm and fine grained floodplain sediments from 13 major rivers in china from north to south were analysed and compiled for the estimation of chemical weathering in china the gradual increase in cia and decrease in wip values with decreasing latitude of the catchments suggest enhanced weathering intensity in these river basins a combined monsoon climate effect of temperature runoff and precipitation primarily controls the chemical weathering in china the provenance rock types and relief play minor roles in weathering whereas an active tectonic setting and typhoon events play key roles in the weathering process in taiwan the cia values of the finer spm samples within a given river are overall greater than those in the corresponding coarser floodplain sediments underscoring the effect of sediment grain size on cia values the irregular seasonal variation of the cia within a specific river further confirms the notion that the cia does not reflect the instantaneous chemical weathering on continents although it is impossible to build a general model for regulating the chemical weathering of continents this study reveals that the integrated chemical weathering intensity in large latitudinal watersheds can with careful application be quantitatively estimated using the proper geochemical proxies of river sediments

sediment trapping in deltas of small mountainous rivers of southwestern taiwan and its influence on east china sea sedimentation abstract taiwan s setting of high mountains steep gradients frequent earthquakes erodible lithology and heavy rainfall represents an ideal site to focus on sedimentary processes of the deltas of small mountainous rivers smrs several smrs in southwestern taiwan have deposited a thick sedimentary succession in the composite southwest taiwan delta swtd since the middle holocene evidence from the swtd can help to determine its trapping efficiency and assess the role of smrs in sediment transport to the sea we used historical nautical charts bathymetric data satellite radar data and 14c dates to calculate the sediment volume of the swtd on millennial and decadal scales the 14c dates of core samples indicate deposition of thick deltaic sediment in subsiding areas since the time of the maximum flooding surface about 7 cal ka bp the paleo shoreline changes of the swtd suggest a steady westward progradation since 7 cal ka bp in contrast the nautical charts suggest minor volume reduction of the offshore part of the swtd with a deepening trend and retreating shorelines during the last seven decades the results show that at least 201 72 13 90 km3 3 23 105 mt of sediment has been trapped in the swtd since 7 cal ka bp and that the delta has shifted to a destructive phase during the past seven decades as human influences such as construction of reservoirs dams and weirs in the hills have reduced the sediment supply the birth of the taiwan warm current and following continuous sediment supply from the western rivers of taiwan to the east china sea since 7 3 cal ka bp have played a crucial role in the sedimentation of the east china sea particularly in the okinawa trough and the japan sea through the tsushima warm current