velocity porosity relationships predictive velocity model for cemented sands composed of multiple mineral phases computer simulations are used to calculate the elastic properties of model cemented sandstones composed of two or more mineral phases two idealized models are considered a grain overlap clay quartz mix and a pore lining clay quartz mix unlike experimental data the numerical data exhibit little noise yet cover a wide range of quartz cement ratios and porosities the results of the computations are in good agreement with experimental data for clay bearing consolidated sandstones the effective modulus of solid mineral mixtures is found to be relatively insensitive to microstructural detail it is shown that the hashin shtrikman average is a good estimate for the modulus of the solid mineral mixtures the distribution of the cement phase is found to have little effect on the computed modulus porosity relationships numerical data for dry and saturated states confirm that gassmann s equations remain valid for porous materials composed of multiple solid constituents as noted previously the krief relationship successfully describes the porosity dependence of the dry shear modulus and a recent empirical relationship provides a good estimate for the dry rock poisson s ratio from the numerical computations a new empirical model which requires only a knowledge of system mineralogy is proposed for the modulus porosity relationship of isotropic dry or fluid saturated porous materials composed of multiple solid constituents comparisons with experimental data for clean and shaly sandstones and computations for more complex three mineral quartz dolomite clay systems show good agreement with the proposed model over a very wide range of porosities

provenance and climate change inferred from sr nd pb isotopes of late quaternary sediments in the huanghe yellow river delta china we present a provenance study of core zk2 from the huanghe yellow river delta in order to assess the impacts of climate change on the sediment supplies during the last glacial interglacial cycle facies analysis and sequence stratigraphy methods are used to construct the age model sr isotopic compositions of zk2 range from 0 716389 to 0 723884 with 87sr 86sr increased with decreasing grain size nd and pb isotopic compositions display two large major excursions during marine oxygen isotope stages mis 2 and 4 with less radiogenic end and lower 208pb 204pb 207pb 204pb and 206pb 204pb values during these periods these excursions have been explained in terms of changes in the mixing proportion of sediments from the loess plateau and ordos plateau resulting from east asian monsoon intensity variations the weak summer monsoon precipitation resulted in decreased erosion of loess plateau during mis 2 4 and the middle of mis 3 meanwhile both the intensified east asian winter monsoon and the southward expansions of mu us desert significantly enhanced the eolian sand entering the huanghe therefore our results highlight the impact of monsoon variability on erosion patterns in the huanghe basin

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

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

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

differential recovery from the effects of a 100 year storm significance of long term hillslope channel coupling howgill fells northwest england a 100 year storm that occurred in 1982 caused major geomorphic changes in the main valleys of the northern howgill fells northwest england those changes which were documented at that time involved extensive hillslope gully erosion alluvial fan sedimentation and substantial sediment input to the stream systems the streams channels which had hitherto been dominantly single thread relatively stable channels responded in many reaches by switching to wide shallow unstable locally braided channels over the 20 years since the event there has been a partial recovery to channel geometries similar to the pre flood conditions however the degree of recovery contrasts between two neighbouring valleys bowderdale and langdale the channel of bowderdale beck has largely recovered flood sedimentation zones have largely stabilised and new single thread channels have cut through most of the former braided reaches in some places channel widths remain higher than the pre flood values and locally recovery has been modified by a lagged complex response in langdale recovery is only partial with many reaches demonstrating sustained instability over the 20 year post flood period furthermore the overall spatial patterns suggest some reach to reach transfer of coarse sediment shifting zones of instability downstream the contrasts between the two valleys appear to relate to different hillslope to channel coupling characteristics themselves inherited from late pleistocene conditions these contrasts are also evident in the longer term post 1949 history of channel change and stability in these two streams indicative of the higher intrinsic instability of the langdale system

rare earth element geochemistry and nd isotope composition of stream sediments south han river drainage basin korea abstract chemical analyses of parent rock soil and stream sediments were done to determine to what extent the river sediments retain the geochemical signature of the parent rocks the study area consists mainly of mesozoic biotite granite and precambrian biotite gneiss located in the central korean peninsula the drainage system consists of tributaries of the south han river such as bokhacheon shinduncheon and yanghwacheon stream sediments were collected every march during 2004 2006 the sediments collected were divided into coarse gravel to sand size and fine silt to clay size more than 90 is coarse sediment the major element composition of the coarse and fine sediments are not identical to the weathering trend of granite however molar proportions of al2o3 cao na2o and k2o in the sediments show that they were derived from granitoids rather than from biotite gneiss the total fe2o3 cao mgo na2o and mno contents and ree concentrations of the fine sediments are higher than those of the coarse sediments in a weathering profile from the granite and gneiss area there was no change of ree distribution pattern from the fresh rock to soil compared to biotite granite normalized ree pattern for the sediment both coarse and fine sediments have relatively flattened ree patterns and all the coarse sediment have positive eu anomalies whereas in the fine sediments negative eu anomalies prevail nd isotopic composition of the sediments is similar to that of the biotite granite rather than the biotite gneiss stream sediments in the icheon area were derived from the granite nd isotope geochemistry as well as ree geochemistry is useful tool for tracing the provenance of the river sediments

quantifying postglacial sediment storage at the mountain belt scale sediment storage is an often neglected term in sediment budgets despite being the crucial link between rates of erosion and sediment yield mountain belts in particular host large valley fills that modulate fluxes of water and sediment buffer the geomorphic coupling between hillslopes and river channels reduce local valley relief and protect bedrock from fluvial incision here we propose a region growing algorithm based on a slope gradient criterion to automatically extract areas of postglacial fluvial and lacustrine valley fills from digital topography at the mountain belt scale applying this method to the european alps we find that the size frequency relationship of 17 766 individual sediment storage units expressed by either area or volume follows a power law over four and five orders of magnitude with scaling exponents 1 77 and 1 71 respectively we show that 90 of the area covered by sediment storage is in the lower quartile of the mountain belt9s elevation and below the median local relief on average low gradient valley fill occupies 6 of the studied drainage basins this fraction increases with basin size likely reflecting the larger accommodation space of trunk valleys generated by multiple glacial interglacial cycles comparison with sediment storage mapped in the southern alps new zealand indicates that rates of uplift and precipitation control the extent and spatial distribution of sediment storage at the mountain belt scale

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

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

delta progradation and chenier formation in the huanghe yellow river delta china abstract to clarify holocene development of the huanghe yellow river delta and the relationship between delta progradation and chenier formation detailed sediment analyses and high resolution radiocarbon dating were done on borehole samples taken from two sites on the present huanghe h9601 latitude 37 40 5 n and longitude 118 28 7 e with an altitude of 5 5 m and h9602 lat 37 47 8 n and long 118 54 3 e 4 8 m downcore changes of sediment facies and accumulation rate show that delta progradation occurred at least twice during ca 2 6 1 2 c 14 yrbp and 1855 present at the two borehole sites these phases of progradation correlate with superlobes 6 and 7 and superlobe 10 respectively of ten superlobes composing the holocene huanghe delta shown by c xue historical changes in the yellow river delta china marine geology 113 321 329 1993 the boundary of these sediments at h9602 is sharp and erosional and correlates with cheniers located between borehole sites on the delta plain the diastem period between these phases of progradation almost coincides with the periods when the river mouth of the huanghe was located in the northwestern part of the bohai sea during 1048 1128 ad superlobe 8 and the jiangsu region facing the yellow sea during 1128 1855 superlobe 9 this suggests that chenier formation and delta progradation are linked and controlled by sediment supply and river course shifts of the lower reaches of the huanghe

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

controls on the erosion of cenozoic asia and the flux of clastic sediment to the ocean rates of continental erosion may be reconstructed from variations in the rate of accumulation of clastic sediment most of which lies offshore global rates of marine sedimentation are usually considered to have reached a maximum after 3 4 ma driven by enhanced erosion in a variable glacial interglacial climate however a new compilation of seismic data from the marginal seas of asia now shows that only the red river reached its historic peak after 4 ma sediment flux from asia first peaked in the early middle miocene 24 11 ma well before the initiation of a glacial climate indicating that rock uplift and especially precipitation are the key controls on erosion at least over long periods of geologic time reconstructions of weathering in east asia show that faster erosion correlates with more humid warm climates in the early middle miocene changing to less erosive drier climates after 14 ma when antarctic glaciation begins average rates of sedimentation on most east asian continental margins since 1 8 ma are 5 6 times less than the modern fluvial flux implying that the flux to the oceans varies sharply on short timescales and is not always buffered over timescales of 10 4 yr by storage in flood plains

variations of east asian summer monsoon since the last deglaciation based on mg ca and oxygen isotope of planktic foraminifera in the northern east china sea 1 variations in mg ca based sea surface temperature and oxygen isotope ratio 18o of the surface water in the northern east china sea ecs were reconstructed with high resolution during the last 18 kyr using planktic foraminifera millennial scale variations between warmer more saline surface water and cooler less saline surface water were recognized during the early deglacial period and the holocene suggesting changes in the mixing ratio between the kuroshio water and the changjiang diluted water stronger east asian summer monsoon easm precipitation events in south china are identified at 10 5 8 8 7 0 5 3 4 7 2 9 1 7 and 0 5 ka based on sea surface salinity sss records of the northern ecs weaker easm precipitation events are also detected at 9 3 8 3 7 3 6 0 3 3 2 3 0 7 and 0 4 ka during the holocene these events agree with the maxima in 18o records of stalagmites from various parts of the changjiang yangtze river drainage this agreement supports that our sss record properly captures the millennial scale dry less easm precipitation events over the drainage basin of the changjiang river during the holocene these dry events are also in good agreement with north atlantic ice rafted events suggesting a teleconnection between north atlantic climate and the easm during the holocene

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

pore geometric modeling for petrophysical interpretation of downhole formation evaluation data 1 an accurate description of water or oil bearing reservoirs strongly depends on a robust determination of their petrophysical parameters e g porosity permeability and fluid distribution downhole logging measurements are the primary means to formation evaluation however they do not directly provide the petrophysical properties of interest to interpret well logging data a range of empirical models are usually employed these empirical relationships however lack scientific basis and usually represent generalizations of the observed trends since macroscopic rock properties vary depending on their microstructure we suggest using a pore scale approach to establish links between various petrophysical properties of sedimentary rocks we outline a method for computing formation permeability using the proposed rock models the method utilizes nmr nuclear magnetic resonance logging data for the information about porosity and grain size we also present an approach for prediction of acoustic velocities of model rocks the proposed methodology is applied to the field data and the corresponding interpretation results are included in this paper

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

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

channel processes following land use changes in a degrading steep headwater stream in north island new zealand abstract in headwater streams in steep land settings narrow and steep valley floors provide closely coupled relationships between geomorphic components including hillslopes tributary fans and channel reaches these relationships together with small catchment sizes result in episodic changes to the amount of stored sediment in channels major sediment inputs follow high magnitude events subsequent exponential losses via removal of material can be represented by a relaxation curve the influence of hillslope and tributary processes on relaxation curves and that of altered coupling relations between components were investigated along a 1 3 km reach of a degrading channel in the 4 8 km2 weraamaia catchment new zealand extensive deforestation in the late 19th and early 20th centuries followed by invasion of scrubs and reforestation induced changes to major erosion types from gully complexes to shallow landslides changes in the size and pattern of sediment slugs from 1938 to 2002 were analysed from air photographs tied to detailed field measurement the rate and calibre of sediment flux changed progressively following substantive hillslope input in a storm in 1938 subsequently the channel narrowed and incised decoupling tributary fans from the main stem thereby scaling down the size of sediment slugs as a consequence the dominant influence on the behaviour of sediment slugs and associated relaxation processes changed from tributary fans to the type and distribution of bedrock outcrops along the reach

morphological responses and sediment processes following a typhoon induced dam failure dahan river taiwan the rates and styles of channel adjustments following an abrupt and voluminous sediment pulse are investigated in the context of site and valley characteristics and time varying sediment transport regimes approximately 10 5 x 106 m3 of stored gravel and sand was exposed when barlin dam failed during typhoon weipa in 2007 the dam was located on the dahan river taiwan a system characterized by steep river gradients typhoon and monsoon driven hydrology high episodic sediment supply and highly variable hydraulic conditions topography bulk sediment samples aerial photos and simulated hydraulic conditions are analyzed to investigate temporal and spatial patterns in morphology and likely sediment transport regimes results document the rapid response of the reservoir and downstream channel which occurred primarily through incision and adjustment of channel gradient hydraulic simulations illustrate how the dominant sediment transport regime likely varies between study periods with sediment yield and caliber and with the frequency and duration of high flows collectively results indicate that information on variability in sediment transport regime valley configuration and distance from the dam is needed to explain the rate and pattern of morphological changes across study periods copyright 2013 john wiley sons ltd

patterns of sediment slug translation and dispersion following typhoon induced disturbance oyabu creek kyushu japan a six year monitoring programme characterized the migration dispersion patterns of sediment slugs generated following typhoon induced disturbances in 1993 and 1997 along a single thread gravel bed stream oyabu creek on kyushu island japan this laterally con ned creek comprises rif e pool sequences with intervening bedrock outcrops the passage of sediment pulses associated with sediment slug processes re ected and was controlled by the rif e pool structures which provided channel bed roughness the volume of sediment stored along valley oors and the distribution of bedrock outcrops changes to bed material size following major sediment inputs during the disturbance events also exerted an in uence on subsequent sediment slug processes the sequence of rainfall events together with changes to channel bed structure induced different phases in the sediment slug processes the capacity of a reach to store or trap sediment as recorded by the longitudinal structure of the channel varied during these differing phases copyright 2004 john wiley sons ltd

channel bed adjustments following major aggradation in a steep headwater setting findings from oyabu creek kyushu japan abstract a typhoon in 1993 induced major aggradation along oyabu creek a steep gravel bed mountain stream in kyushu japan processes of sediment reworking are inferred from a 7 year monitoring program that measured adjustments to channel cross sections the longitudinal profile and the extent distribution of bedrock outcrops along a 3 km study reach over time the reach adopted a riffle and pool structure with notable increase in the area of exposed bedrock on the bed this adjustment process was characterised by progressive reduction in sediment storage change per unit flow the relaxation pathway following disturbance induced by the typhoon was shaped by the magnitude and frequency of subsequent rainfall events the capacity of these events to transport available sediments and physical linkages between reaches adjacent subreaches demonstrated differing relaxation pathways in response to these influences induced by spatial and temporal variability in threshold conditions along the channel longer term evidence indicates that responses to major disturbance such as the 1993 typhoon occur as cycles of around 20 year duration a relaxation period of 7 years is required to attain a quasi equilibrium bed configuration and rate of sediment flux the timeframe of cycles is considered to reflect changes to hillslope channel bed coupling marking the period required to generate sufficient sediment stores to reactivate phases of aggradation and subsequent degradation

provenance sea level and monsoon climate controls on silicate weathering of yellow river sediment in the northern okinawa trough during late last glaciation abstract high resolution multi proxy records including geochemical and grain size data from detrital sediments of iodp site u1429 in the northern okinawa trough provide reliable evidence for constraining sediment source and transport processes they also allow silicate weathering and erosion controlled by sea level change and east asian summer monsoon evolution since 34 ka to be reconstructed provenance proxies indicated that sediments in the northern okinawa trough were mainly supplied by the yellow river middle reach at 34 8 ka the low sea level and proximity of paleo yellow river mouth to the northern okinawa trough were the causes of the dominant yellow river input after 8 ka a retreated yellow river mouth coupled with the blocking effect of the kuroshio current and its branches together with strong east asian summer monsoon precipitation resulted in relatively strong sediment input from kyushu to the northern okinawa trough meanwhile yellow river upper reach supplied more sediments to the study site than that during the 34 8 ka on glacial interglacial scale silicate weathering proxies indicate that the core sediment was more weathered during the last glacial and deglacial than that in the modern yellow river we attribute this to the increased upper reach sediment input which supplied more weak weathered sediment to the study site during the holocene besides composite effect of weathering during glacial and deglacial sediment production and additional weathering upon subaerial exposure of shelf deposits during low sea level stage as well as older weathered sediments reworking during sea level rise could also account for this weathering regime on multi millennial scale from 34 to 18 5 ka silicate weathering was mainly controlled by the east asian summer monsoon with a cooling and drying climate associated with weakened summer monsoon activity this is consistent with the reduced alteration of sediments eroded from the yellow river basin from 18 5 to 8 ka strong reworking of older weathered sediments overwhelmed the east asian summer monsoon in controlling silicate weathering which induced a continuous increase in chemical alteration of the sediments during this period

translation and dispersion of sediment pulses in flume experiments simulating gravel augmentation below dams 1 the effectiveness of gravel augmentation as a river restoration strategy depends on the extent and duration of the topographic and bed texture changes created by the pulse of added sediment previous work has emphasized the strong tendency for natural sediment waves to propagate primarily by dispersion however pulse translation may occur for gravel additions to armored channels downstream of dams where added sediments are finer than the preexisting bed material here we report results of a laboratory investigation in which we created an immobile armored bed and documented the spatial and temporal evolution of the bed topography and bed texture in response to gravel pulses of various volumes and grain sizes the introduced sediment waves evolved by a combination of translation and dispersion with a significant translational component pulse translation and dispersion can be readily discerned on a graph of the time evolution of the downstream cumulative distribution of elevation differences from the preexisting bed topography translation was most evident for smaller volumes of added sediment pulses of finer grained gravel moved through the flume more rapidly resulting in a larger magnitude but shorter duration of bed fining more work is needed to understand the influence of bar pool topography and flow magnitude and duration before the grain size and volume of gravel additions can be selected to achieve optimal patterns of pulse propagation

geochemistry of large river suspended sediments silicate weathering or recycling tracer this study focuses on the major and trace element composition of suspended sediments transported by the world s largest rivers its main purpose is to answer the following question is the degree of weathering of modern river borne particles consistent with the estimated river dissolved loads derived from silicate weathering in agreement with the well known mobility of elements during weathering of continental rocks we confirm that river sediments are systematically depleted in na k ba with respect to the upper continental crust for each of these mobile elements a systematics of weathering indexes of river borne solids is attempted a global consistency is found between all these indexes important variations in weathering intensities exist a clear dependence of weathering intensities with climate is observed for the rivers draining mostly lowlands however no global correlation exists between weathering intensities and climatic or relief parameters because the trend observed for lowlands is obscured by rivers draining orogenic zones an inverse correlation between weathering intensities and suspended sediment concentrations is observed showing that the regions having the highest rates of physical denudation produce the least weathered sediments finally chemical and physical weathering are compared through the use of a simple steady state model we show that the weathering intensities of large river suspended sediments can only be reconciled with the silicate derived dissolved load of rivers by admitting that most of the continental rocks submitted to weathering in large river basins have already suffered previous weathering cycles a simple graphical method is proposed for calculating the proportion of sedimentary recycling in large river basins finally even if orogenic zones produce weakly weathered sediments we emphasize the fact that silicate chemical weathering rates and hence co2 consumption rates by silicate weathering are greatly enhanced in mountains simply because the sediment yields in orogenic drainage basins are higher hence the parameters that control chemical weathering rates would be those that control physical denudation rates

submarine hydrothermal mineralization in the okinawa trough sw of japan an overview abstract the okinawa trough is a heavily sedimented rifted back arc basin formed in an intracontinental rift zone submarine hydrothermal activity is located within the six back arc rifts located in the middle and southern okinawa trough and its distribution is controlled principally by tectonic factors subduction of the daito and gagua ridges beneath the ryukyu arc has resulted in fracturing of the brittle lithosphere beneath the okinawa trough hydrothermal activity is strongest in the volcanic arc rift migration phenomenon vamp area plus the jade site and southernmost part of the okinawa trough spot area which form the prolongation of these two ridges these areas are characterized by extremely high heat flow locally submarine hydrothermal fluids from the okinawa trough tend to be strongly influenced by interaction of the hydrothermal fluids with organic matter in the sediment resulting in high alkalinity and nh 4 concentrations of the fluids the fluids also contain high concentrations of co 2 of magmatic origin submarine hydrothermal mineralization in the trough is diverse the clam site consists principally of carbonate chimneys interaction of the hydrothermal fluid with organic matter in the sediment is particularly strong at this site this is most probably a sediment hosted deposit in which sulphide minerals have deposited within the sediment column leaving spent ore fluids to emerge at the seafloor the jade site consists of active and inactive sulphide sulphate chimneys and mounds the zn pb rich sulphides at this site contain the highest concentrations of pb ag and au so far recorded in submarine hydrothermal sulphide deposits at minami ensei knoll and hatoma knoll active and inactive chimneys consist principally of anhydrite and barite as a result of phase separation of the hydrothermal fluids beneath the seafloor an intense black smoker has recently been discovered at yonaguni knoll in the spot area if it is confirmed that sulphide mineralization is dominant at this site this could be a highly prospective area the most prospective areas for economic grade minerals in the okinawa trough appear to be the jade site and the spot area

a lateglacial and holocene lake record from the nianbaoyeze mountains and inferences of lake glacier and climate evolution on the eastern tibetan plateau abstract our 12 81 m long record from lake ximencuo provides insight into the lateglacial and holocene evolution of the lake and the nianbaoyeze glacier in its catchment and the regional climate history since 19 kyr lake ximencuo was a permanent deep lake throughout its history in contrast to numerous lakes on the tibetan plateau which experienced shallow lake levels or even desiccation during the lateglacial lake ximencuo was fed by large quantities of meltwater in the lateglacial the existence of glaciated upper catchment areas is apparently a prerequisite for lakes on the tibetan plateau which maintained relatively high water levels during the generally cold and dry periods following the global lgm 21 kyr a minor re advance of the nianbaoyeze glacier was recorded coeval with the greenland stadial 2a 16 4 and 14 5 kyr followed by rapid warming apparently synchronous with the greenland interstadial 1 warmest conditions were recorded at lake ximencuo during the early holocene which was punctured by a remarkable pulse of climate deterioration around 8 3 kyr this spell represents probably the 8 2 kyr event of the north atlantic region suggesting that it had a significant impact on the tibetan plateau colder conditions of longer duration occurred from 4 7 to 3 7 kyr apparently in phase with numerous records signalling colder and drier conditions on the tibetan plateau two minor spells of colder conditions and probably catchment erosion were recorded in the late holocene between 2 0 and 1 4 kyr and between 0 5 and 0 1 kyr with the latter representing the little ice age it is unclear whether human activities may have accelerated or even solely triggered the late holocene erosion events

submarine weathering of silicate minerals and the extent of pore water freshening at active continental margins in order to investigate how submarine weathering processes may affect the water balance of sediments at convergent plate margins six sediment cores were retrieved off central chile at water depth between 800 and 4000 m the sediment solid phase was analyzed for its major element composition and the pore fluids were analyzed for dissolved sulfate sulfide total alkalinity major cations chloride bromide iodide hydrocarbons as well as the carbon isotopic composition of methane because of negligible weathering on land surface sediments off central chile are rich in reactive silicate minerals and have a bulk composition similar to volcanic rocks in the adjacent andes deep sourced fluxes of alkalinity cations and chloride indicate that silicate minerals are subject to weathering in the forearc during burial comparison of deep sourced signals with data from nearby ocean drilling program sites reveals two different types of weathering processes in shallow tens of meters methanic sediments of slope basins with high organic carbon burial rates reactive silicate minerals undergo incongruent dissolution through reaction with co2 from methanogenesis at greater burial depth hundreds of meters silicate weathering is dominated by authigenic smectite formation this process is accompanied by uptake of water into the clay interlayers thus leading to elevated salinities in the surrounding pore water deep seated smectite formation is more widespread than shallow silicate dissolution as it is independent from the availability of co2 from methanogenesis although solute transport is not focused enough to form cold seeps in the proper sense tectonically induced diffuse fluid flow transfers the deep seated signal of smectite formation into the shallow sediments the temperature controlled conversion of smectite to illite is considered the most important dehydration process in marine forearc environments depth of kilometers however in agreement with other studies at active margins e g aleutians cascadia nankai trough and despite ubiquitous evidence for smectite formation little evidence for seafloor seepage of dehydration fluids could be found off central chile we argue that the circular process of pore water uptake during smectite formation and release upon illitization implies a balanced freshwater budget and therefore a rather limited potential for net pore water freshening on a margin wide scale according to this rationale pore water freshening at seafloor seeps preferentially occurs at lower latitudes central america barbados mediterranean ridge where terrestrial weathering is more intense thus leading to external i e detrital smectite and thus freshwater inputs to the subduction system

enhanced chemical weathering of rocks during the last glacial maximum a sink for atmospheric co2 abstract it has been proposed that increased rates of chemical weathering and the related drawdown of atmospheric co2 on the continents may have at least partly contributed to the low co2 concentrations during the last glacial maximum lgm variations in continental erosion could thus be one of the driving forces for the glacial interglacial climate cycles during quaternary times to test such an hypothesis a global carbon erosion model has been applied to a lgm scenario in order to determine the amount of co2 consumed by chemical rock weathering during that time in this model both the part of atmospheric co2 coming from silicate weathering and the part coming from carbonate weathering are distinguished the climatic conditions during lgm were reconstructed on the basis of the output files from a computer simulation with a general circulation model only the predicted changes in precipitation and temperature have been used whereas the changes in continental runoff were determined with an empirical method it is found that during the lgm the overall atmospheric co2 consumption may have been greater than today by about 20 mainly because of greater carbonate outcrop area related to the lower sea level on the shelves this does not however affect the atmospheric co2 consumption by silicate weathering which alone has the potential to alter atmospheric co2 on the long term silicate weathering and the concomitant atmospheric co2 consumption decreased together with a global decrease of continental runoff compared to present day both by about 10 nevertheless some uncertainty remains because the individual lithologies of the continental shelves as well as their behavior with respect to chemical weathering are probably not well enough known the values we present refer to the ice free continental area only but we tested also whether chemical weathering under the huge ice sheets could have been important for the global budget although glacial runoff was considerably increased during lgm weathering under the ice sheets seems to be of minor importance

geochemical record of holocene to recent sedimentation on the western indus continental shelf arabian sea 1 we present a multiproxy geochemical analysis of two cores recovered from the indus shelf spanning the early holocene to recent 14 ka indus 23 is located close to the modern indus river while indus 10 is positioned 100 km further west the holocene transgression at indus 10 was over a surface that was strongly weathered during the last glacial sea level lowstand lower holocene sediments at indus 10 have higherendvalues compared to those at the river mouth indicating some sediment supply from the makran coast either during the deposition or via reworking of older sediments outcropping on the shelf sediment transport from makran occurred during transgressive intervals when sea level crossed the mid shelf the sediment flux from non indus sources to indus 10 peaked between 11 ka and 8 ka a hiatus at indus 23 from 8 ka until 1 3 ka indicates non deposition or erosion of existing indus shelf sequences higherendvalues seen on the shelf compared to the delta imply reworking of older delta sediments in building holocene clinoforms chemical index of alteration cia mg al and sr isotopes are all affected by erosion of detrital carbonate which reduced through the holocene k al data suggest that silicate weathering peaked ca 4 6 ka and was higher at indus 10 compared to indus 23 fine grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain the indus shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings

prediction of elastic wave velocities in sandstones using structural models elastic wave propagation in fluid saturated sandstones depends upon two sets of rock features 1 the volume fractions and elastic constants of the rock constituents quartz clay water etc and 2 microstructural geometry grain contacts pore aspect ratios while the former data are usually obtainable the latter are relatively inaccessible we present a new method for determining microstructural data using idealized but physically representative models of sandstone the key to the method is the simulation of certain depositional and diagenetic processes in a manner that completely specifies the geometry of the resulting models hence the geometric features of the grain space and void space required for various theories of elastic propagation can be calculated directly from the models we find good agreement between predictions and measurements of compressional and shear wave velocities in both clean and clay bearing saturated sandstones in contrast with previous efforts at predicting velocitie

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

simulation of the last glacial maximum climate over east asia with a regional climate model nested in a general circulation model abstract the east asian climate at the last glacial maximum lgm 21 000 years b p has been simulated using a regional climate model regcm2 nested in an atmospheric general circulation model of the institute of atmospheric physics iap agcm boundary conditions for the lgm simulations are consistent with the paleoclimate modelling intercomparison project pmip the results show that the nested regional model reproduces well the colder lgm climates over east asia the simulated annual mean surface temperature is 2 c 4 c colder than the present over the east asian continent with the coldest anomaly of about 8 c in the vicinity of current coastal areas where land is exposed due to lowering sea level at the lgm the precipitation changes are complex with general features of drier conditions over eastern china and its neighborhood and wetter conditions over western china than the present compared with the driving iap agcm the regcm2 results display better agreement with geological reconstructions over east asia especially in the mideastern and southern china the simulated warming changes by the iap agcm disagree with cooling in paleodata whereas the regcm2 reproduces realistic cooler lgm climate thus the current work proves that the high resolution regcm2 can capture additional regional details in the lgm simulation produced by improved representation of topography and physics

moderate chemical weathering of subtropical taiwan constraints from solid phase geochemistry of sediments and sedimentary rocks abstract the well known earthquake and storm triggered extremely high physical weathering rate in taiwan is consistent with present geochemical studies of sediments from different subenvironments offshore coastal river and lake and sedimentary rocks of different geological ages indicating a moderate chemical weathering condition major and trace element concentrations normalized to the average upper crust of yangtze craton show that the sediments and the average composition of sedimentary rocks of taiwan are depleted in ca mg na and sr enriched in rb and zr and unchanged with respect to k indicating their moderately altered nature the mean chemical index of alteration cia 71 75 and plagioclase index of alteration pia 81 86 values of coastal and offshore sediments reveal the sediments derivation from sedimentary rocks by moderate silicate chemical weathering processes the mean cia value 62 of sedimentary rocks of taiwan is similar to that for chinese sediment 61 further confirming

management responses to pulses of bedload sediment in rivers abstract rivers can experience sudden pulses of sediment from human and natural erosion processes that can accumulate in the bed abundant studies have examined the sources and dynamics of sediment pulses and problems caused by these pulses particularly flooding avulsions and habitat simplification much less has been written about what managers can do about sediment pulses and that is the purpose of this review the first option for managers is to do nothing and this decision can be informed by many case studies and by theory on the propagation and character of sediment pulses their diffusion translation and celerity doing nothing should be informed by the secondary effects of sediment pulses on channels including widening avulsions and tributary interactions if managers decide that something needs to be done about the sediment they have four options 1 reducing the sediment supply at source 2 trapping sediment in the channel 3 accelerating sediment transport through a reach and 4 directly extracting sediment the most common of these actions is undoubtedly to reduce the supply at source but there are few examples of the consequences of this for sediment pulses there are even fewer examples of trapping accelerating and extracting sediment all of these options have great potential for managing sediment pulses however they also have the potential to trigger incision of tributaries and of the channel behind the passing sediment wave overall the literature equips managers to understand the dynamics of sediment pulses but it does not yet equip them to confidently manage these geomorphic events

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

circum mediterranean fire activity and climate changes during the mid holocene environmental transition 8500 2500 cal bp a mid to late holocene synthesis of fire activity from the mediterranean basin explores the linkages among fire climate variability and seasonality through several climatic and ecological transitions regional fire histories were created from 36 radiocarbon dated sedimentary charcoal records available from the global charcoal database during the mid holocene thermal maximum around 7500 4500 cal bp charcoal records from the northern mediterranean suggest an increase in fire while records from the southern mediterranean indicate a decrease associated with wetter than present summers a north south partition between 40 and 43 n latitude is apparent in the central and western mediterranean relatively abrupt changes in fire activity are observed c 5500 5000 cal bp records of holocene fire activity appear sensitive to both orbitally forced climate changes and shorter lived excursions which may be related to north atlantic cold events possibly modulated by an nao like climate mechanism in cases wh

clay mineral and grain size studies of sediment provenances and paleoenvironment evolution in the middle okinawa trough since 17 ka okinawa trough receives a large amount of fluvial sediment transported by complex oceanographic circulations and is an ideal location for the study of paleoceanography and paleoenvironment changes however our knowledge of the sediment provenance and paleoenvironment evolution in the trough during the past 17 ka is still limited based on high resolution grain size clay minerals and ams c 14 data of the core oki04 we present new evidences of the provenances and paleoenvironment evolution in the middle okinawa trough during the last 17 ka our results indicate that clay sized terrigenous sediment deposited in the middle okinawa trough is mainly from those rivers flowing into east china sea and yellow sea e g yangtze and yellow rivers and taiwanese rivers their contributions varied greatly in space and time during the past 17 ka from 16 5 to 13 8 ka sediment was mainly derived from the yangtze and yellow rivers with little contribution from taiwan from 13 8 to 5 4 ka the contributions from the yangtze and yellow rivers oscillated multiple times low in 13 8 11 6 ka high in 11 6 7 6 ka and back to low in 7 6 5 4 ka whereas the pattern of taiwanese contribution was opposite after 5 4 ka when the sea level was high and shoreline was far away from the okinawa trough the yangtze river and eastern taiwanese rivers became the main provenances the contribution from the yellow river decreased which is probably because yellow river mouth was far away from the middle trough sediment grain size data show that two environmentally sensitive populations are 71 7 mu m and 7 0 5 mu m the variation of the populations mean grain size and content shows that the strength of kuroshio current was weak during 16 5 11 6 ka and became strong in 11 6 5 4 ka in which tsushima warm current and yellow sea warm current formed around 8 5 and 6 5 ka respectively the strength of kuroshio current decreased in 5 4 ka and increased since 3 2 ka based on clay mineralogical analysis we find that the kaolinite chlorite could be used as a new effective indicator for the east asian winter monsoon s evolution in the trough since 17 ka c 2015 elsevier b v all rights reserved

hydraulic and acoustic properties as a function of porosity in fontainebleau sandstone laboratory measurements have been made of the permeability k free porosity l compressional velocities vp or ve and compressional attenuations qp or qe in fontainebleau sandstone over a continuous range of porosities from 3 to 28 this large variation was achieved without any composition change fontainebleau sandstone is made of fine quartz grains with regular grain size 250 m permeability was measured with a falling head permeameter velocities and attenuations were obtained either through an ultrasonic experiment for frequencies around 500 khz or through a resonant bar technique experiment for frequencies around 5 khz and in both cases with varying water saturation the results show an excellent correlation between permeability k and total porosity for all our samples for low porosities 3 to 9 permeability in millidarcies is 2 75 10 5 7 33 while for high porosities 9 to 28 permeability k in millidarcies is given by 0 303 3 05 the correlation is also excellent between free porosity and total porosity on the other hand the correlation between acoustic properties and total porosity is not as clear as for hydraulic properties whatever the frequency 500 khz or 5 khz or the water saturation on the average velocity decreases and attenuation roughly increases with increasing total porosity velocity and attenuation values are related to the variation of grain contact structure and two samples with the same porosity and permeability may exhibit different velocities and attenuations the clear correlation between hydraulic properties and porosity is related to constant grain size while the lack of correlation for acoustic properties emphasizes the importance of the microstructure

ree geochemistry of fine grained sediments from major rivers around the yellow sea abstract to investigate the distribution pattern and controlling factors of rare earth elements rees in riverine sediments river mouth sediments were collected at five geographically different rivers around the yellow sea two 1 m hcl leached and residual fractions and five step sequential extraction schemes the sedex method were applied to size separated sediments

sr nd isotopic constraints on detrital sediment provenance and paleoenvironmental change in the northern okinawa trough during the late quaternary for this study elemental and sr nd isotopic compositions of ams c 14 age dated core sediments from the northern okinawa trough were investigated to reconstruct sediment provenance and transport processes over the last 22 3 ka and further to trace the forcing mechanisms behind the provenance changes the results clearly showed that large compositional variations of these elements and isotopes occur in deposition suggesting three phases of changes in sediment source paleo huanghe unit 3 223 14 8 ka east china sea shelf derived unit 2 14 8 7 3 ka and taiwan derived detritus stages unit 1 7 3 ka such provenance changes since the last glacial maximum may be closely correlated to sea level fluctuation the evolution of tsushima warm current as well as east asian monsoonal climatic variation at 22 3 14 8 ka the paleo huanghe mouth was situated close to the study area thus dominating sedimentation therein especially during stronger winter monsoon periods at the beginning of unit 2 14 8 12 8 ka rapid sea level rise and significant retreat of the river mouth overwhelmed enhanced continental weathering leading to less detrital sediment supply from the paleo huanghe to the study area subsequently the east china sea shelf derived matter dominated detrital deposition therein from 12 8 to 73 ka since 73 ka the fully evolved tsushima warm current has transported some detrital particles from taiwan to the study area especially during the strengthening period at 7 3 5 1 ka a prominent decline in taiwan sourced matter supply at 5 1 2 8 ka may have been caused by suppression of the tsushima warm current possibly associated with the pulleniatina minimum event c 2015 elsevier b v all rights reserved

reconstructing chemical weathering physical erosion and monsoon intensity since 25 ma in the northern south china sea a review of competing proxies reconstructing the changing strength of the east asian summer monsoon has been controversial because different proxies many being indirect measures of rainfall tell contrasting stories about how this has varied over long periods of geologic time here we present new sr isotope grain size and clastic flux data and synthesize existing proxies to reconstruct changing chemical erosion in the northern south china sea since the oligocene using the links between weathering rates and monsoon strength established in younger sediments as a way to infer intensity chemical proxies such as k rb l al and the chemical index of alteration cia together with clay proxies like kaolinite illite chlorite show a steady decline in alteration after a sharp fall following a maximum at the mid miocene climatic optimum mmco 15 5 17 2 ma probably as a result of cooling global temperatures in contrast physical erosion proxies including bulk ti ca and clastic mass accumulation rates mar show peaks at 21 23 ma similar to 19 ma and 15 5 17 2 ma implying faster run off in the absence of drainage capture rates increase again likely driven by slightly increased run off after 13 ma but decrease after 8 ma which is identified as a period of summer monsoon weakening sr isotope composition correlates with hematite goethite and the spectral proxy crat to show stronger weathering linked to more monsoonal seasonality these proxies argue for a strengthening of the east asian monsoon after 22 23 ma followed by an extended period of monsoon maximum between 18 and 10 ma then weakening there is some suggestion that the summer monsoon may have strengthened since 3 4 ma after reaching a minimum in the pliocene c 2014 elsevier b v all rights reserved

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

effects of porosity and clay content on wave velocities in sandstones the ultrasonic compressional vp and shear vs velocities and first arrival peak amplitude ap were measured as functions of differential pressure to 50 mpa and to a state of saturation on 75 different sandstone samples with porosities ranging from 2 to 30 percent and volume clay content c ranging from 0 to 50 percent respectively both vp and vs were found to correlate linearly with porosity and clay content in shaly sandstones at confining pressure of 40 mpa and pore pressure of 1 0 mpa the best least squares fits to the velocity data are vp km s 5 59 6 93 2 18c and vs km s 3 52 4 91 1 89c deviations from these equations are less than 3 percent and 5 percent for vp and vs respectively the velocities of clean sandstones are significantly higher than those predicted by the above linear fits about 7 percent for vp and 11 percent for vs which indicates that a very small amount of clay 1 or a few percent of volume fraction significantly reduces the elastic moduli of sandstones for shaly

morphodynamic response of a variable width channel to changes in sediment supply river channels commonly exhibit downstream variations in channel width which can lead to the development of alternating shallow and deep areas known as riffle pool sequences the response of these channels to variations in sediment supply remains largely unexplored here we investigate the morphodynamic response of a variable width channel to changes in sediment supply through laboratory experiments conducted in a straight flume in which we imposed sinusoidal variations in width we first developed equilibrium conditions under a constant sediment supply and then eliminated the sediment feed to create a degraded armored bed this sediment starved bed was subjected to two types of sediment supply increases a return to the initial constant supply and the introduction of a well sorted sediment pulse analogous to gravel augmentation riffles and pools formed in wide and narrow areas respectively and the location of and relief between riffles and pools remained the same throughout all experimental runs regardless of the sediment supply the primary channel response to changes in supply was adjustment of the overall slope the sediment pulse evolved primarily through dispersion rather than translation which contrasts with prior gravel augmentation experiments conducted in constant width channels and suggests that width variation and resulting riffle pool topography enhances pulse dispersion our results indicate that width variation is a primary control on the location and relief of riffles and pools in straight channels and sediment supply changes are unlikely to affect riffle pool morphology when bank geometry is fixed and water discharge is steady

provenance of dust in the pacific ocean eolian dust preserved in deep sea sediment cores provides a valuable indicator of past atmospheric circulation and continental paleoclimate in order to identify the provenance of eolian dust nd and sr isotopic compositions and rb sr and rare earth element ree concentrations have been determined for the silicate fractions of deep sea sediments from the north and central pacific ocean different regions of the pacific ocean are characterized by distinct air borne inputs producing a large range in end 10 to 1 stsr 86sr 0 705 0 721 la yb 5 15 eun eu 0 6 1 0 and sr nd 4 33 the average nd isotopic composition of pacific deep sea sediments eno 6 is more radiogenic than the average from the atlantic ena 8 in contrast the average 1475m 14and ratio for pacific sediments 0 114 is identical to that of atlantic sediments and to that of global average riverine suspended material the values of ena and 147sm 144nd are positively correlated for the pacific samples but negatively correlated for atlantic samples reflecting a fundamental difference between the dominant components in the end members with radiogenic nd island arc components in the pacific and lree enriched intraplate ocean island components in the atlantic samples from the north central pacific have distinctive unradiogenic end values of 10 87sr 86sr 0 715 high la yb 12 and low eun eu 0 6 and sr nd 3 6 these data are virtually identical to the values for loess from asia and endorse the use of these sediments as indicators of asian paleoclimate and paleowind directions island arc contributions appear to dominate in the northwest pacific resulting in higher end 1 to 1 and lower 87sr 86sr 0 705 and la yb 5 sediments from the eastern pacific tend to have intermediate sr and nd isotopic compositions but regionally variable sr nd and ree patterns they appear to be derived from the west margin of the north and south american continents rather than from asia our results confirm that dust provenance can be constrained by isotopic and geochemical analyses which will facilitate reconstructions of past atmospheric circulation and continental paleoclimate

channel braiding and stability of the brahmaputra river bangladesh since 1967 gis and remote sensing analyses spatial and temporal changes in channel distribution in the large sandy braided system of the brahmaputra river bangladesh were analyzed using satellite images and gis supervised classification of the images within the braided belt i e channels and bars between the bank lines provided raster land cover data for 14 different years between 1967 and 2002 the width of the braided belt the number and width of channels the distribution of land cover attributes and land stability change were examined from the data the results indicate that the recent history of the dynamics of the brahmaputra can be divided into four phases 1 the late 1960s to early 1970s 2 the mid 1970s to early 1980s 3 the mid 1980s to early 1990s and 4 the mid 1990s to early 2000s spatial distributions of the land cover and channels in phase 4 were the least complex suggesting a state of dynamic equilibrium land cover and channel distributions during phase 2 were partly less complex indicating quasi dynamic equilibrium phases 1 and 3 can be regarded as transitional phases with more complex conditions frequent large floods may have triggered significant changes in the river system during phases 1 and 3

geochemical variation within the northern ryukyu arc magma source compositions and geodynamic implications the major and trace element and pb sr nd isotopic compositions of quaternary mafic lavas from the northern ryukyu arc provide insights into the nature of the mantle wedge and its tectonic evolution beneath the volcanic front in the northern part of the arc the subducted slab of the philippine sea plate bends sharply and steepens at a depth of 80 km lavas from the volcanic front have high abundances of large ion lithophile elements and light rare earth elements relative to the high field strength elements consistent with the result of fluid enrichment processes related to dehydration of the subducting slab new pb isotopic data identify two distinct asthenospheric domains in the mantle wedge beneath the south kyushu and northern ryukyu arc which in a parallel with data from the lau basin appear to reflect mantle with affinities to indian and pacific type mid ocean ridge basalt morb indian ocean morb type mantle contaminated with subducted ryukyu sediments can account for the variation of lavas erupted on south kyushu and probably in the middle okinawa trough in contrast magmas of the northern ryukyu volcanic front appear to be derived from sources of pacific morb type mantle contaminated with a sedimentary component along arc variation in the northern ryukyus reflects increasing involvement of a sedimentary component to the south compositions of alkalic basalts from the south kyushu back arc resemble intraplate type basalts erupted in nw kyushu since 12 ma we propose that the bending of the subducted slab was either caused by or resulted in lateral migration of asthenospheric mantle yielding indian ocean type characteristics from a mantle upwelling zone beneath nw kyushu and the east china sea this model also accounts for 1 extensional counter clockwise crustal rotation 4 2 ma 2 voluminous andesite volcanism 2 ma and 3 the recent distinctive felsic magmatism in the south kyushu region

chemical weathering in the upper huang he yellow river draining the eastern qinghai tibet plateau we examined the fluvial geochemistry of the huang he yellow river in its headwaters to determine natural chemical weathering rates on the northeastern qinghai tibet plateau where anthropogenic impact is considered small qualitative treatment of the major element composition demonstrates the dominance of carbonate and evaporite dissolution most samples are supersaturated with respect to calcite dolomite and atmospheric co2 with moderate 0 710 0 715 87 sr 86 sr ratios while six out of 21 total samples have especially high concentrations of na ca mg cl and so4 from weathering of evaporites we used inversion model calculations to apportion the total dissolved cations to rain evaporite carbonate and silicate origin the samples are either carbonate or evaporite dominated but the relative contributions of the four sources vary widely among samples net co2 consumption rates by silicate weathering 6 120 10 3 mol km 2 yr are low and have a relative uncertainty of 40 we extended the inversion model calculation to literature data for rivers draining orogenic zones worldwide the ganges brahmaputra draining the himalayan front has higher co2 consumption rates 110 570 10 3 mol km 2 yr and more radiogenic 87 sr 86 sr 0 715 1 24 than the upper huang he but the rivers at higher latitudes are similar to or lower than the upper huang he in co2 uptake by silicate weathering in these orogenic zones silicate weathering rates are only weakly coupled with temperature and become independent of runoff above 800 mm yr copyright 2005 elsevier ltd

abrupt climate variability since the last deglaciation based on a high resolution multi proxy peat record from nw iran the hand that rocked the cradle of civilization abstract we present a high resolution sub decadal to centennial multi proxy reconstruction of aeolian input and changes in palaeohydrological conditions based on a 13000 yr record from neor lake s peripheral peat in nw iran variations in relative abundances of refractory al zr ti and si redox sensitive fe and mobile k and rb elements total organic carbon toc 13 c toc compound specific leaf wax hydrogen isotopes d carbon accumulation rates and dust fluxes presented here fill a large gap in the existing terrestrial paleoclimate records from the interior of west asia our results suggest that a transition occurred from dry and dusty conditions during the younger dryas yd to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early holocene 9000 6000 yr bp this period was followed by relatively drier and dustier conditions during middle to late holocene which is consistent with orbital changes in insolation that affected much of the northern hemisphere numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the middle to late holocene wavelet analysis of variations in ti abundances as a proxy for aeolian input revealed notable periodicities at 230 320 and 470 years with significant periodicities centered around 820 1550 and 3110 years over the last 13000 years comparison with palaeoclimate archives from west asia the north atlantic and african lakes point to a teleconnection between north atlantic climate and the interior of west asia during the last glacial termination and the holocene epoch we further assess the potential role of abrupt climate change on early human societies by comparing our record of palaeoclimate variability with historical geological and archaeological archives from this region the terrestrial record from this study confirms previous evidence from marine sediments of the arabian sea that suggested climate change influenced the termination of the akkadian empire in addition nearly all observed episodes of enhanced dust deposition during the middle to late holocene coincided with times of drought famine and power transitions across the iranian plateau mesopotamia and the eastern mediterranean region these findings indicate that while socio economic factors are traditionally considered to shape ancient human societies in this region the influence of abrupt climate change should not be underestimated

geochemical discrimination of clastic sedimentary rock sources abstract factors controlling the geochemistry of a clastic sedimentary rock can include 1 composition of source terrain 2 chemical weathering 3 hydraulic sorting 4 diagenesis 5 metamorphism and 6 hydrothermal alteration a linear solution inferring source terrain composition from geochemistry of the sediment is impossible in this multivariate system as several unknowns will commonly be present the use of graphical analysis of element pairs circumvents the problem chemically immobile elements will maintain invariant ratios during rock mass change caused by either addition or depletion of mobile elements this results in chemically immobile element scattergrams exhibiting linear trends along radians extending from the origin if the major mineral phases of the immobile elements have behaved in a hydrodynamically similar manner as chemically mobile element plots will produce a scatter of points this relationship can be used to test chemical immobility and similarity in hydrodynamic sorting history the constraint on analysis is that the source area must be compositionally uniform or the sediment well mixed prior to delivery to the basin a second technique using sio2 plots has also been developed to investigate element mobility and hydrodynamic behaviour of the mineral phases containing the elements sio2 immobile element plots result in a linear arrangement of points extending towards either 0 or 100 sio2 the 0 intercept position occurs for elements with major mineral phases concentrated in sand the 100 intercept for those concentrated in clays plotting chemically mobile elements produces different patterns and this can be used to gain information on alteration and sorting history elemental ratios for chemically immobile elements with similar hydrodynamic behaviour will be the same as those for the weighted average composition of the source material this provides a powerful tool for deducing source terrain from sediment geochemistry techniques outlined above were tested on archaean metasandstones from superior province canada immobile element ratio diagrams for nb al ti and zr al ti indicate that a calc alkaline extrusive intrusive suite lying to the north of the study area was the source and not five other volcanic suites in the region this conclusion agrees with previous clast lithology studies and accentuates the applicability of the geochemical techniques

holocene sedimentology of hypersaline lake urmia northwestern iran abstract a limnogeological expedition examined the sedimentary record of lake urmia one of the world s largest saline lakes located in a tectonically active arid intermontane plateau in northwestern iran near the cradle of western civilization lake urmia resembles the great salt lake u s a in many respects of morphology water chemistry and sediments the present lake area is about 5000 km 2 shallow 8 12 m and a perennial sodium chloride sulfate system 22 salts high resolution 3 5 khz seismic profiles show morphological relicts from a desiccation playa phase buried below only a few meters of sediments from lacustral phases in places around the deeper areas the lake floor is not smooth but covered with mounds aligned in prevailing current directions these are erosional relicts rather than bioherms sediments comprise aragonite chemical precipitates fecal pellet sands detrital clayey muds thin aragonite crusts oolites various gypsum types and occurrences of dolomite in peripheral areas organic matter characteristic of the present shorelines is not preserved at depth in basinal areas piston cores up to 6 m long penetrated a holocene sequence of hypersaline facies with laminated aragonite fecal pellet muds and bottomed in a playa mudflat facies with central gypsiferous muds and marginal terrigenous to dolomitic muds preliminary radiocarbon and pollen analyses suggest a playa stage prior to 9000 yr b p with saline lake deposition in a cool arid climate from 9000 to 7500 yr b p higher energy facies prevailed in a shallow saline lake and since then present day saline environments have persisted with evidence of numerous second order water level fluctuations the preliminary results suggest a lake system out of phase with north african and some other middle eastern lakes

evolution of weathering patterns in the indo burman ranges over the last 280 kyr effects of sediment provenance on 87sr 86sr ratios tracer a high resolution study of mineralogy and major element geochemistry combined with sr and nd isotopes has been conducted on high sedimentation rate cores collected off the irrawaddy river mouth in the andaman sea and the bay of bengal to reconstruct the erosional and weathering history of the irrawaddy river basin in both cores nd 0 values imply that both glacial and interglacial sediments share a common crustal source the irrawaddy river strong glacial interglacial cycles are recorded by 87sr 86sr interglacial periods yield values between 0 713 and 0 717 whereas glacial periods show higher values between 0 717 and 0 719 variations of the pedogenic clays smectite and kaolinite to primary mineral feldspar quartz illite and chlorite ratios show strong precessional cycles suggesting a control by past changes in the summer monsoon intensity each increase in pedogenic clays content is also associated with a net loss of labile elements na k and ca from the detrital minerals under chemical weathering wet periods of summer monsoon reinforcement correspond to an increase in weathering of the irrawaddy plain soils and a decrease of 87sr 86sr ratio plotting 87sr 86sr versus 87rb 86sr gives a pseudo isochrons interpreted as a mixing line representing the strength of chemical weathering during glacial stages enhanced physical erosion induced by glacier scour and frost action in the highland of the irrawaddy river basins produced high volumes of unaltered rb rich minerals the low sea level of glacial times constricted the river to the main channel in the lower reaches and permitted an efficient transport of unaltered rb rich minerals with high radiogenic sr composition from the high relief of the indo burman ranges and the tibetan plateau to the indian ocean

evidence for the submarine weathering of silicate minerals in black sea sediments possible implications for the marine li and b cycles 1 the role of sediment diagenesis in the marine cycles of li and b is poorly understood because li and b are easily mobilized during burial and are consumed in authigenic clay mineral formation their abundance in marine pore waters varies considerably exchange with the overlying ocean through diffusive fluxes should thus be common nevertheless only a minor li sink associated with the low temperature alteration of volcanic ash has been observed we describe a low temperature diagenetic environment in the black sea dominated by the alteration of detrital plagioclase feldspars fluids expelled from the odessa mud volcano in the sorokin trough originate from shallow 100 400 m deep sediments which are poor in volcanic materials but rich in anorthite these fluids are depleted in na k li b and 18o and enriched in ca2 and sr2 indicating that anorthite is dissolving and authigenic clays are forming using a simple chemical model we calculate the ph and the partial pressure of co2 pco2 in fluids associated with this alteration process our results show that the ph of these fluids is up to 1 5 ph units lower than in most deep marine sediments and that pco2 levels are up to several hundred times higher than in the atmosphere these conditions are similar to those which favor the weathering of silicate minerals in subaerial soil environments we propose that in black sea sediments enhanced organic matter preservation favors co2 production through methanogenesis and results in a low pore water ph compared to most deep sea sediments as a result silicate mineral weathering which is a sluggish process in most marine diagenetic environments proceeds rapidly in black sea sediments there is a potential for organic matter rich continental shelf environments to host this type of diagenesis should such environments be widespread this new li and b sink could help balance the marine li and li isotope budgets but would imply an apparent imbalance in the b cycle

the role of large woody debris in modulating the dispersal of a post fire sediment pulse abstract in 2001 a series of post fire debris flows brought 30 000 m3 of sediment deposited as fans to the narrow valley floor of sleeping child creek in western montana usa in 2005 pebble counts and surveys of the channel in proximity to six of the debris flow fans documented a regular sequence of fine grained aggradation upstream of the fans incision through the fans and coarse grained aggradation downstream of the fans these measurements were repeated in 2012 we found that the delivery of large woody debris lwd over the intervening 7 years has been a dominant factor in the disposition of the debris flow material the amount of lwd in the study reach has increased by as much as 50 in the areas with a high burn severity leading to the formation of large logjams that interrupt the flow of sediment along the streambed nearly all of the surveyed reaches have aggraded since 2005 including those that had initially begun incising through the debris flow deposits and the streambed has become generally finer we hypothesize that over the next few decades debris flow sediment not colonized and anchored by riparian vegetation will trickle out of the affected reaches as the logjams slowly degrade

tectonic and climatic controls on long term silicate weathering in asia since 5 ma determining the interplay between tectonic deformation climate atmospheric co2 concentrations and continental weathering and erosion is key to understanding the mechanisms that forced cenozoic global cooling in contrast with studies of paleo climate and pco 2 the history of long term silicate weathering in the himalaya and tibetan plateau htp during the late cenozoic remains unclear we reconstruct 5 m y of silicate sedimentary records at ocean drilling program odp site 1143 in the south china sea to explore the weathering history of the mekong river basin that supplied the sediment coherent variation of weathering proxies from the south china sea bay of bengal loess plateau as well as the yangtze and yellow rivers indicates weakening chemical weathering intensity since the late pliocene as the climate cooled this cooling coupled with tectonic activity shifted the dominant weathering regime from more transport limited to more weathering limited causing less chemical depletion of silicate minerals while silicate weathering rates became strongly correlated to erosion rates they were decoupled from chemical weathering intensity physical denudation and associated silicate weathering rates in the htp area increased in the pliocene driven by both rock uplift and stronger monsoon precipitation decreasing atmospheric co2 concentrations and so contributing to northern hemisphere glaciation nhg citation wan s p d clift a li z yu t li and d hu 2012 tectonic and climatic controls on long term silicate weathering in asia since 5 ma geophys res lett 39 l15611 doi 10 1029 2012gl052377

sedimentary evolution and environmental history of lake van turkey over the past 600 000 years the lithostratigraphic framework of lake van eastern turkey has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years the lithostratigraphy and chemostratigraphy of a 219 m long drill core from lake van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity an age model was established based on the climatostratigraphic alignment of chemical and lithological signatures validated by 40ar 39ar ages the drilled sequence consists of ca 76 lacustrine carbonaceous clayey silt ca 2 fluvial deposits ca 17 volcaniclastic deposits and 5 gaps six lacustrine lithotypes were separated from the fluvial and event deposits such as volcaniclastics ca 300 layers and graded beds ca 375 layers and their depositional environments are documented these lithotypes are i graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations ii varved clayey silts reflecting strong seasonality and an intralake oxic anoxic boundary for example lake level highstands during interglacials interstadials iii caco3 rich banded sediments which are representative of a lowering of the oxic anoxic boundary for example lake level decreases during glacial inceptions iv caco3 poor banded and mottled clayey silts reflecting an oxic anoxic boundary close to the sediment water interface for example lake level lowstands during glacials stadials v diatomaceous muds were deposited during the early beginning of the lake as a fresh water system and vi fluvial sands and gravels indicating the initial flooding of the lake basin the recurrence of lithologies i to iv follows the past five glacial interglacial cycles a 20 m thick disturbed unit reflects an interval of major tectonic activity in lake van at ca 414 ka bp although local environmental processes such as tectonic and volcanic activity influenced sedimentation the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes making lake van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years

re evaluation of the wave model as a tool for quantifying the geomorphic recovery potential of streams disturbed by sediment slugs abstract a central principle of stream rehabilitation is that managers should accelerate the natural recovery of degraded streams in this paper we explore the recovery of channel morphology behind translating sediment waves using an observed expected space for time substitution sfts model channel recovery is defined by the variability of the thalweg cross sections and bed sediments of the three streams investigated in se australia one followed the general response described by gilbert s classic wave model with the stream bed returning to its pre disturbance geomorphic variability as the sediment wave passed in this case the recovery did not necessarily decline gradually with the distance away from the peak of the slug instead the geomorphic variability remained low within the slug and then increased dramatically once the slug evacuated by contrast the other two streams continued on their pre slug trajectory of channel incision which has not allowed geomorphic variability to establish once the sediment slug has passed the three study streams showed different recovery responses to a relatively simple pulse of sediment

aeolian control on the deposition of high altitude lacustrine basins in the middle east the case of lake neor nw iran abstract lake neor is the largest lacustrine basin in the high mountains of the middle east at 2500 m altitude in the alborz belt this lake of holocene age is a shallow fresh water body of glacial origin with ca 4 km 2 surface area and a 40 km 2 drainage area its sedimentary sequence comprised of peat and gyttja consists of 10 m infill which is fairly thick for such a lake autochthonous organic matter is limited in and around the lake except for small areas at the northern and southern ends inorganic constituents of the infill sediment include a significant amount of fine grained calcite dolomite and mica particles that are exotic to the catchment they do not occur in the source rocks as the drainage area of the lake is composed of only andesites and trachyandesites of eocene age in addition the uppermost part of the infill includes abundant fine grained charcoal particles derived from large forest fires perhaps derived as far as the mediterranean region as shown by the present meteorological records the sediment of lake neor is under aeolian control during dust storms this is leading to a considerable amount of deposition air borne particles the infill of some lakes particularly those in highlands may have contain an important aeolian component and thus they cannot be used directly for the interpretation of the evolution of the palaeogeography without taking into consideration the role of dust storms on deposition

sediment pulse evolution and the role of network structure abstract sediment pulses are triggered through a variety of mechanisms from landslides to land use change how do these pulses move through the fluvial system and how do they evolve in a system with perfect sediment connectivity the erosional response to a perturbation and the resulting signal at the river mouth would match however this rarely occurs many studies have addressed reach scale dynamics of sediment pulses and how they translate or disperse downstream at the watershed scale network structure and storage become more important in modulating the sediment signal here we review the current literature on sediment pulse behavior and then address the role of network structure on maintaining dispersing or transforming sediment pulses in a fluvial system we use a reduced complexity network routing model that simulates the movement of bed material through a river basin this model is run in the greater blue earth river gber basin in minnesota usa first with spatially uniform inputs and then with inputs constrained by a detailed sediment budget once the system reaches equilibrium a sediment pulse is introduced first at a single location and then throughout the system and tracked as it evolves downstream results indicate that pulses able to translate downstream disperse in place upon arriving at over capacity reaches as sediment goes into storage in the gber basin these zones occur just upstream of a knickpoint that is propagating upstream through all mainstem channels as the pulses get caught in these sediment bottlenecks there is a decoupling of the original pulse of sediment and the resulting bed material wave these results show that the network structure both in terms of network geometry and the spatial pattern of transport capacity can play a dominant role in sediment connectivity and should be considered when predicting sediment pulse behavior at the watershed scale

conceptual model of sediment processes in the upper yuba river watershed sierra nevada ca this study examines the development of a conceptual model of sediment processes in the upper yuba river watershed and we hypothesize how components of the conceptual model may be spatially distributed using a geographical information system gis the conceptual model illustrates key processes controlling sediment dynamics in the upper yuba river watershed and was tested and revised using field measurements aerial photography and low elevation videography field reconnaissance included mass wasting and channel storage inventories assessment of annual channel change in upland tributaries and evaluation of the relative importance of sediment sources and transport processes hillslope erosion rates throughout the study area are relatively low when compared to more rapidly eroding landscapes such as the pacific northwest and notable hillslope sediment sources include highly erodible andesitic mudflows serpentinized ultramafics and unvegetated hydraulic mine pits mass wasting dominates surface erosion on the hillslopes however erosion of stored channel sediment is the primary contributor to annual sediment yield we used gis to spatially distribute the components of the conceptual model and created hillslope erosion potential and channel storage models the gis models exemplify the conceptual model in that landscapes with low potential evapotranspiration sparse vegetation steep slopes erodible geology and soils and high road densities display the greatest hillslope erosion potential and channel storage increases with increasing stream order in channel storage in upland tributaries impacted by hydraulic mining is an exception reworking of stored hydraulic mining sediment in low order tributaries continues to elevate upper yuba river sediment yields finally we propose that spatially distributing the components of a conceptual model in a gis framework provides a guide for developing more detailed sediment budgets or numerical models making it an inexpensive way to develop a roadmap for understanding sediment dynamics at a watershed scale published by elsevier b v

eolian inputs of lead to the north pacific we evaluate the importance of natural eolian pb to the dissolved oceanic pb budget by measuring the isotopic composition of pb in 35 holocene and late quaternary sediment samples from the north pacific and in 10 samples of chinese loess when the pacific is divided into sediments provinces based on published end and sedimentological data pb from the central north pacific tends to be the most radiogenic and homogeneous due to the dominance of eolian chinese loess lead from the marginal north pacific and the sparsely sampled regions south of 5 n are less radiogenic and more variable owing to hemipelagic inputs from various volcanic arcs and older continental crust located around the pacific rim 208pb 204pb ratios provide the most distinctive provenance information due to the relatively high ratios in chinese loess the chinese loess samples come from 3 localities and span up to 2 myr of time acetic acid leachate bulk loess and loess silicate fractions were analyzed separately leachate pb is considerably less radiogenic than silicate pb the isotopic composition of the silicate component closely matches the sediment data from the central north pacific confirming the dominance of eolian loess in this region we divided up a suite of published hydrogenous pb isotope data from the pacific ocean according to their locations within the three independently defined sediment provinces these data define three distinct fields differentiated primarily by their 206pb 204pb ratios which increase going from the central to southern to marginal provinces this relationship with sediment province strongly suggests that natural eolian and probably hemipelagic inputs significantly impact the seawater pb budget direct support for the dominance of eolian chinese loess in the central north pacific dissolved pb budget comes from the close match between loess leachate pb and the central province hydrogenous pb data eolian inputs are likely to dominate local seawater pb budgets only where eolian pb fluxes are high relative to hemipelagic pb fluxes and where the flux of pb carried by deep water advection is low

reorganization of the western himalayan river system after five million years ago uplift of mountains driven by tectonic forces can influence regional climate1 2 as well as regional drainage patterns which in turn control the discharge of eroded sediment to the ocean3 4 but the nature of the interactions between tectonic forces climate and drainage evolution remains contested5 6 7 here we reconstruct the erosional discharge from the indus river over the past 30 million years using seismic reflection data obtained from drill core samples from the arabian sea and neodymium isotope data we find that the source of the indus sediments was dominated by erosion within and north of the indus suture zone until five million years ago after that the river began to receive more erosional products from himalayan sources we propose that this change in the erosional pattern is caused by a rerouting of the major rivers of the punjab into the indus which flowed east into the ganges river before that time seismic reflection profiles from the indus fan suggest high mass accumulation rates during the pleistocene epoch partly driven by increased drainage to the indus river after five million years ago and partly by faster erosion linked to a stronger monsoon over the past four million years1 our isotope stratigraphy for the indus fan provides strong evidence for a significant change in the geometry of western himalayan river systems in the recent geologic past

characteristics of dust deposited along a transect between central iran and the zagros mountains abstract few studies have been reported on the characteristics of dust particles deposited in arid regions of the middle east the objective of this study was to identify the variations in physical chemical and mineralogical composition of dust particles deposited along an elevational transect lying between central iran and the zagros mountains in the west dust samples were collected at 12 localities during september 2008 and july 2009 with and without transboundary dust storms respectively samples were examined for their grain size distribution and their mineralogical and chemical composition surface soils were also sampled from the vicinity of the dust sampling sites and their total elemental compositions were determined the results indicated that dust deposition rate mean particle diameter and concentration of soluble ions in samples from both sampling periods decreased with altitude with a significantly lower gradient for samples of july 2009 than for those of september 2008 the similarity observed in dust samples taken during september 2008 and those reported by previous studies or measured in local soils and sediments suggests that local soils greatly contribute to the atmospheric dust along the transect in periods with no dust storms during such periods dust deposits in the high altitude zagros mountains where annual precipitation is higher and temperature lower only receive a minor contribution from arid soils of central iran however in july 2009 when a heavy dust storm took place significant differences were observed between local soils and dust samples along the transect particularly at high altitudes in terms of their physicochemical and mineralogical characteristics these findings together with satellite images and patterns of wind frequency and direction clearly indicate the major contribution of a transboundary dust storm probably originating from iraqi arid land to atmospheric deposition in the zagros area and central iran when dust storms blow from across the borders the contribution of local soils and sediments to aerosols drastically decreases with elevation if dust storms originating from outside the country continue to occur not only will they influence the surface soil properties in the zagros region but will also induce environmental problems in the region

major and trace element variations of the sediments at odp site 1144 south china sea during the last 230 ka and their paleoclimate implications abstract we present here the major and trace element data of the sediments at odp site 1144 of the last 230 ka with time resolution about 1 5 kyr to investigate their relations to the climate changes estimated from tio2 and cao contents over 70 in weight of the sediments are terrestrial materials and caco3 abundance ranges between 7 and 19 the variation patterns of some of the major elements such as al fe k mg and mn and some of the trace elements such as the alkali elements such as rb and cs the alkali earth elements such as ba and most transition metals such as sc v co cr zn well match that of the oxygen isotopes of the planktonic foraminifer after normalized with ti with higher values during interglacial periods and lower values during glacial periods whilst the na abundance exhibits inverse variation patterns with lower values during interglacial periods and higher values during glacial periods however most refractory elements such as y zr nb hf ta rees th and u do not show such patterns these agree well with the behaviors of these elements during chemical weathering therefore the changes of chemical weathering intensity in south china the source area of these sediments may account for such variation patterns during interglacials wet and warm climate might occur at south china which resulted in stronger chemical weathering and dry climate might occur during glacials which resulted in weaker chemical weathering such paleoclimate interpretation agrees with those from other paleoclimate proxies such as pollen records indicating that change of the east asian monsoon especially change of the winter monsoon is the key for such paleoclimate variation patterns

trapping of aeolian sediments and build up of the ice cover of a dry based antarctic lake among the perennially frozen lakes of the dry valleys of south victoria land antarctica some are dry based i e frozen to the bottom one of these is studied here by a multiparametric investigation isotopic composition in da nd 18 o ions gas and ice texture analyses a sediment layer about 10 cm thick appearing at a depth of 3 5m is also studied by grain size x ray diffraction and scanning electron microscope analyses the information retrieved indicates that this ice block lake results from a build up in two steps and explains how aeolian sediments were included as a layer into the ice copyright 2002 john wiley sons ltd

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

magnitude and timing of downstream channel aggradation and degradation in response to a dome building eruption at mount hood oregon a dome building eruption at mount hood oregon starting in a d 1780 and lasting until ca 1793 produced dome collapse lithic pyroclastic flows that triggered lahars and intermittently fed 10 8 m 3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the sandy river mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river depositional reach 61 87 km from the source stratigraphic and sedimentologic relations in the alluvial fill together with dendrochronologic dating of degradation terraces demonstrate that 1 channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less 2 the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome building eruption 3 fluvial sediment transport and deposition augmented by one lahar achieved a minimum average aggradation rate of 2 m yr 4 the degradation phase of the cycle was more prolonged than the aggradation phase requiring more than half a century for the river to reach its present bed elevation and 5 the present longitudinal profile of the sandy river in this reach is at least 3 m above the pre eruption profile the pattern and rate of channel response and recovery in the sandy river following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs the magnitude of channel aggradation in the lower sandy river greater than that achieved at other volcanoes following much larger eruptions was likely enhanced by lateral confinement of the channel within a narrow incised valley a combination of at least one lahar and winter floods from frequent moderate magnitude rainstorms and infrequent very large storms was responsible for flushing large volumes of sediment to the depositional reach these conditions permitted a sedimentation response in the sandy river that approached the magnitude of channel aggradation resulting elsewhere from large explosive eruptions and high intensity rainfall regimes despite the fact that the sandy river aggradation was in response to an unremarkable dome building eruption in a climate dominated by low to moderate rainfall intensities

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

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

effects of sediment pulses on channel morphology in a gravel bed river sediment delivery to stream channels in mountainous basins is strongly episodic with large pulses of sediment typically delivered by infrequent landslides and debris flows identifying the role of large but rare sediment delivery events in the evolution of channel morphology and fluvial sediment transport is crucial to an understanding of the development of mountain basins in july 2001 intense rainfall triggered numerous debris flows in a severely burnt watershed in the sapphire mountains of montana ten large debris flow fans were deposited on the valley floor and investigations focused on the channel response to these sediment pulses the channel has aggraded immediately upstream of each fan and braided in reaches immediately downstream channel incision through the fans has created sets of coarse grained terraces the deposition upstream of the pulses consists almost exclusively of fine material resulting in a median bed material size d 50 1 2 orders of magnitude lower than the ambient channel material the volume of sand being transported is so great that these aggrading reaches can extend hundreds of meters upstream of the fans with 1 2 m of sand deposited across the entire valley floor along a 10 km study reach cross section surveys longitudinal profiles and pebble counts chronicle channel response to a punctuated increase in sediment supply and provide insight on the processes of sediment wave dispersal

experimental evidence for the effect of hydrographs on sediment pulse dynamics in gravel bedded rivers 1 gravel augmentation is a river restoration technique applied to channels downstream of dams where size selective transport and lack of gravel resupply have created armored relatively immobile channel beds augmentation sediment pulses rely on flow releases to move the material downstream and create conditions conducive to salmon spawning and rearing yet how sediment pulses respond to flow releases is often unknown here we explore how three types of dam releases constant flow small hydrograph and large hydrograph impact sediment transport and pulse behavior translation and dispersion in a channel with forced bar pool morphology we use the term sediment pulse generically to refer to the sediment introduced to the channel the zone of pronounced bed material transport that it causes and the sediment wave that may form in the channel from the additional sediment supply which can include input sediment and bed material in our experiments we held the volume of water released constant which is equivalent to holding the cost of purchasing a water volume constant in a stream restoration project the sediment pulses had the same grain size as the bed material in the channel we found that a constant flow 60 greater than the discharge required to initiate sediment motion caused a mixture of translation and dispersion of the sediment pulse a broad crested hydrograph with a peak flow 2 5 times the discharge required for entrainment caused pulse dispersion while a more peaked hydrograph 3 times the entrainment threshold discharge caused pulse dispersion with some translation the hydrographs produced a well defined clockwise hysteresis effecting sediment transport as is often observed for fine sediment transport and transportlimited gravel bed rivers the results imply a rational basis for design of water releases associated with gravel augmentation that is directly linked to the desired sediment behavior