spatial variability of soil properties at different scales within three terraces of the henares river spain abstract this paper applies statistical and geostatistical procedures to a soil chronosequence on the terraces of the henares river ne madrid to analyse the spatial distribution of several soil properties and use the contribution of geostatistics to establishing a landscape evolution model of the area particle size distribution ph calcium carbonate and organic carbon were analysed statistical procedures focus on analysing differences between terraces geostatistical procedures identify short and medium range variations within individual terraces at different scales standard transitive variogram models describe the properties of the younger terrace whereas the linear intransitive model fits the majority of variograms of the older terrace the analysis confirms and quantifies the decrease in variability of soil properties from young to old deposits showing thus an increment of soil homogenisation with time ageing of the terraces causes the variables to show nontransitive variogram models with unbounded variances within the observation range

will river erosion below the three gorges dam stop in the middle yangtze abstract the environmental impact of the three gorges dam has been a subject of vigorous academic political and social debate since its inception this includes the key issue of post dam river channel erosion which was predicted by the feasibility study to extend to the river mouth in this paper we examine the geomorphic response of the channel of the middle yangtze for 660 km downstream of the dam using data on channel characteristics bed material and sediment transport we show that in the decade following the dam closure pre dam seasonal erosion has been replaced by year round erosion a pattern most marked at the upstream end of the study area the sediment carrying capacity of the river channel has been largely reduced below the dam the locus of bed scour has moved progressively downstream ceasing as the bed material became too coarse to be transported e g d 50 0 29 mm pre dam coarsened to 20 mm below the dam by 2008 about 400 km below the dam there is a reduction in channel slope that changes the sediment carrying capacity from 0 25 kg m 3 to only about 0 05 kg m 3 which is insufficient to move bed sediment the new long term hydro morphological equilibrium that will be established in this section of the middle yangtze will prevent the further incision downstream initiated by the three gorges dam the results suggest that the full extent of adverse environmental impact predicted by the pre dam studies will not eventuate

combined effects of multiple large scale hydraulic engineering on water stages in the middle yangtze river abstract investigation of water stages influenced by human projects provides better understanding of riverine geomorphological processes and river management based on hydrological data collected over 60 years an extreme stage extreme discharge analysis and a specific gauge analysis were performed to research the individual and combined effects of multiple engineering projects on a long term time series of water stages in the middle yangtze river conclusions are as follows 1 in accordance with the operation years of the jingjiang cutoff cf the gezhouba dam gd and the three gorges dam tgd the time series 1955 2012 was divided into periods of p1 1955 1970 p2 1971 1980 p3 1981 2002 and p4 2003 2012 water stage changes during p1 p2 p2 p3 and p3 p4 are varied because of the differences in the types and scales of these projects the stage decreased at shashi and increased at luoshan owing to the operation of the cf additionally after the gd was constructed the low flow stage decreased in the upstream reach of chenglingji and increased in its downstream reach whereas the flood stage merely decreased at yichang moreover the tgd resulted in an overall decrease in low flow stages and a limited increase in flood stages because of the differential adjustments of river geometry and resistance between the low flow channel and flood channel 2 although differences existed in the scouring mechanisms between streamwise erosion associated with dams and headward erosion associated with cutoffs particular bed textures in the gravel reach led to a similar adjustment that stage reduction at shashi was the greatest of all stations which caused the flow slope and sediment transport capacity to decrease in the sandy reach 3 these engineering projects caused changes in average low flow and flood stages that varied between yichang 1 58 and 0 08 m respectively shashi 3 54 and 0 12 m and luoshan 1 15 and 0 97 m from p1 to p4 however less influence was observed at hankou owing to its remote location and the short impoundment time of the tgd 4 potentially detrimental decreases in low flow stages and increases in flood stages should be monitored and managed in the future our results are of practical significance for river management and the evaluation of the influences of large scale anthropogenic activities on the hydrological regimes of large rivers

estimating transmissivity using empirical and geostatistical methods in the volcanic aquifers of upper awash basin central ethiopia transmissivity t is a basic hydraulic parameter of an aquifer that is utilized in most groundwater flow equations to understand the flow dynamics and is generally estimated from pumping tests however the cost of performing a large number of aquifer tests is expensive and time consuming the fact that specific capacity s c is correlated with hydraulic flow properties of aquifers simplifies parameter estimation mainly because specific capacity values are more abundant in groundwater databases than values of transmissivity and they offer another approach to estimate hydraulic parameters of aquifers in this study an empirical relation is derived using 214 pairs of transmissivity and specific capacity values that are obtained from pumping tests conducted on water wells penetrating the complex volcanic aquifers of upper awash basin central ethiopia linear and logarithmic regression functions have been performed and it is found that the logarithmic relationship predicting transmissivity from specific capacity data has a better correlation r 0 97 than the linear relationship r 0 79 the two parameters are log normally distributed in which the logarithmic relation is also better statistically justified than the linear relation geostatistical estimations of the transmissivity were made using different inputs and methods measured and supplemented transmissivity data obtained from estimates using the derived empirical relation were krigged and cokrigged spherical and exponential models were fitted to the experimental variograms the cross validation results showed that the best estimation is provided using the kriging procedure the transmissivity field represented by the measured transmissivity data and the experimental variogram fitted with the exponential model based on the geostatistical approach the transmissivity map of the aquifer is produced which will be used for groundwater flow modeling of the study area that will follow this analysis

geostatistical estimation of the transmissivity in a highly fractured metamorphic and crystalline aquifer man danane region western ivory coast abstract this work is aimed at estimating the transmissivity of highly fractured hard rock aquifers using a geostatistical approach the studied aquifer is formed by the crystalline and metamorphic rocks of the western ivory coast west africa in the man danane area the study area covers 7290 km 2 90 km 81 km the fracturing network is dense and well connected without a marked fracture direction a data base comprising 118 transmissivity t values and 154 specific capacity q s values was compiled a significant empirical relationship between t and q s was found which enabled the transmissivity data to be supplemented the variographic analysis of the two variables showed that the variograms of t and q s which are lognormal variables are much more structured than those of log t and log q s which are normal variables this result is contrary to what was previously published and raises the question whether normality is necessary in geostatistical analysis several input and geostatistical estimations of the transmissivity were tested using the cross validation procedure measured transmissivity data supplemented transmissivity data kriging cokriging the cross validation results showed that the best estimation is provided using the kriging procedure the transmissivity field represented by the whole data sample measured estimated using specific capacity and the structural model evaluated solely on the measured transmissivity the geostatistical approach provided in fine a reliable estimation of the transmissivity of the man danane aquifer which will be used as an input in forthcoming modelling

implications of flow control by the three gorges dam on sediment and channel dynamics of the middle yangtze changjiang river china the impacts of a dam on the river downstream in terms of hydrology and morphology are determined by a complex mix of variables that includes the patterns of release of water through the dam and the characteristics of the downstream channel scour of the downstream channel is a common response because large dams cause a significant interruption to sediment continuity here we show that in the case of china9s three gorges dam on the yangtze river the outcome is complicated as is commonly the case in large rivers the downstream channel and floodplain system compose an area of long term sediment accumulation and unstable channels with seasonally contrasting erosion and deposition patterns related to the migrating seasonal monsoon rainfall zones in achieving one of the main purposes of this dam that of flood control in the middle and lower basins the pattern of flows released from the dam will closely resemble those seasonal flows that are responsible for channel instability in the middle catchment thus effectively making erosive conditions the most common during a year there is obviously concern about the ultimate impact of sediment storage in the dam on the dynamics of the delta and adjacent coast and we show that this depends on the trajectory and duration of the erosive responses in the middle yangtze basin in this particular case the outcome is of great significance to the well being of the densely populated riparian areas of the river

evaluating late cretaceous oaes and the influence of marine incursions on organic carbon burial in an expansive east asian paleo lake abstract expansive late cretaceous lacustrine deposits of east asia offer unique stratigraphic records to better understand regional responses to global climate events such as oceanic anoxic events oaes and terrestrial organic carbon burial dynamics this study presents bulk organic carbon isotopes 13 c org elemental concentrations xrf and initial osmium ratios 187 os 188 os os i from the turonian coniacian qingshankou formation a 5 ma lacustrine mudstone succession in the songliao basin of northeast china a notable 13 c org excursion 2 5 in organic carbon lean qingshankou members 2 3 correlates to oae3 in the western interior basin wib of north america within temporal uncertainty of high precision age models decreases in carbon isotopic fractionation 13 c through oae3 in the wib and songliao basin suggest that significantly elevated global rates of organic carbon burial drew down pco 2 likely cooling climate despite this os i chemostratigraphy demonstrates no major changes in global volcanism or weathering trends through oae3 identification of oae3 in a lake system is consistent with lacustrine records of other oaes e g toarcian oae and underscores that terrestrial environments were sensitive to climate perturbations associated with oaes additionally the relatively radiogenic os i chemostratigraphy and xrf data confirm that the qingshankou formation was deposited in a non marine setting organic carbon rich intervals preserve no compelling os i evidence for marine incursions an existing hypothesis for generating member 1 s prolific petroleum source rocks based on our results we present a model for water column stratification and source rock deposition independent of marine incursions detailing dominant biogeochemical cycles and lacustrine organic carbon burial mechanisms

tracing the sources fate and recycling of fine sediments across a river delta interface abstract deltaic floodplains are thought to be long term depositional environments however there remains a limited understanding regarding timescales of depositional and erosional events sediment delivery pathways and sediment storage this study uses sediment concentration and sediment fingerprinting to examine the contribution of surface and subsurface sources to suspended sediment transiting the lower roanoke river north carolina united states the lower roanoke is disconnected from its high gradient uplands in the piedmont and appalachian mountains by a series of dams which effectively restricts suspended sediment delivery from the headwaters accordingly sediments from the lower roanoke river basin are the primary source of suspended sediment downstream of the dams the fingerprinting method utilized fallout radionuclide tracers 210pbxs and 137cs to examine the spatial variation of sediment source contributions to suspended sediment samples n 79 three end member sources were sampled 1 surface sources floodplains and topsoils n 60 2 subsurface sources channel bed and banks n 66 and 3 deltaic sources delta front and prodelta n 11 the results demonstrate that with decreasing river slope and increasing influence of estuarine driven flow dynamics the relative contribution of surface sediments to the suspended sediment load increases from 20 2 in the upper reach to 67 1 in the roanoke bayhead delta bhd at the river mouth the surface sediment contribution decreases and the delta front and prodelta sediments contribute 74 1 to the suspended load these results indicate that during the delta transgression erosion of the lower delta provides an additional source of sediment to the upper delta at the same time the lower deltaic plain considered a sediment sink and long term sediment storage site becomes erosional the lower river and distributary network of the delta plain which were thought to only disperse sediments in a seaward direction may also have an important landward directed sediment dispersal component that provides nourishment and fortification to the upper bhd at the cost of the eroding lower delta recognition of these contrasting sediment pathways in the roanoke river highlights that these complex bidirectional processes may exist in other eroding deltas understanding these bidirectional processes will be necessary for the ongoing management of deltaic environments under increasing anthropogenic stress such as land use change and accelerating sea level rise

classification and mapping of anthropogenic landforms on cultivated hillslopes using dems and soil thickness data example from the sw parisian basin france this study focuses on linear anthropogenic landforms of decametric width on cultivated hillslopes and their relations to soil thickness variability the 16 ha study area shows a rolling topography supported by cretaceous chalk of the sw parisian basin france two types of landforms were identified lynchets similar to those described as soil terraces occurring on downslope field parts in other contexts and undulations linear convex landforms that cut across fields accurate dem construction and a detailed soil thickness survey were performed all over the study area soil samples were classified considering their location on specific types of anthropogenic landforms the classification tree ct method was applied to assess whether lynchets and undulations can be discriminated through morphometric attributes slope curvature profile curvature and planform curvature and soil thickness ctsoil or through morphometric attributes only cttopo the ct application establishes predictive classification models to map the spatial distribution of lynchets and undulations over the whole study area the validation results of the ctsoil and cttopo applications show model efficiencies of 83 and 67 respectively both models performed well for lynchets errors arise mainly from difficulties in unequivocally discriminating gently convex undulations and undifferentiated surfaces especially when soil thickness is not accounted for mean values of soil thickness are 1 08 0 62 and 0 45 m in lynchets undulations and undifferentiated areas respectively the general shape of the thickened soil is characteristic to each type of anthropogenic landform multi temporal mapping of field border networks shows that undulations are linked to borders that were removed during the latest land consolidation lynchets are associated with current field borders lynchets and undulations which cover 39 of the study area define topographic indicators of human induced soil accumulations the method involves perspectives for efficiently mapping and quantifying the anthropogenically modified spatial variability of soil thickness on agricultural hillsides

transmissivity and morphological features in a chalk aquifer a geostatistical approach of their relationship abstract whether for the management of an aquifer or to locate new wells hydrogeologists have always tried to establish transmissivity maps of regional aquifers with the highest possible accuracy classically the transmissivity is obtained from well tests and or from calibrating a groundwater flow model on the piezometric data in this paper we investigate the possibility of adding new information to improve the estimates of the transmissivity in a shallow chalk aquifer i e the characteristics of certain morphological features here referred to as lynchets which are short lineaments that can be seen on aerial photographs or on topographic maps and represent a sudden breach in slope of the ground surface we implicitly associate the density of these features with the density of vertical fracturing of the chalk which is linked to the transmissivity we selected the chalk aquifer of northern france to test this approach using numerical and geostatistical techniques to construct maps of the density of the lynchets we compared them with transmissivity maps produced either by calibrating a groundwater flow model with piezometric data or by kriging the transmissivity values obtained with well tests we conclude that the lynchet information is clearly correlated with the transmissivity and that this information can best be used by cokriging as a second variable associated with the well test data incidentally to fit our geostatistical models of spatial variability variogram we use a new technique called the integral semi variogram which is ideally suited to cases such as this where the spatial distribution of the data is such that the data points cannot easily be grouped into pairs of increasing lag distance this new technique is described briefly

hydraulic parameters in the neoproterozoic aquifer of yaounde cameroon in this paper hydrological properties generally needed to improve all over the world the policy and then the sustainability of groundwater resources are also presented in the neoproterozoic terrane of yaounde cameroon for this purpose data collected from 150 boreholes realized in the study area were analysed statistically the transmissivity t and the specific flow q s have been deduced from the pumping tests interpretation using the jacob recovery method the average transmissivity is equal to 2 9 10 5 m2 s and the specific flow is equal to 0 26 m2 s wells depth d in general ranges from 41 to 80 m with an average of 57 m the empirical relationship between t and q s is t 0 0158 q s 1 01 with the determination coefficient r2 0 64 the weathered layer has a thickness h ranged from 2 6 to 63 3 m with an average of 16 8 m compared to other areas of the crystalline basement although in the middle of the equatorial forest the mean specific flow and the mean transmissivity in the neoproterozoic terrane of yaounde represent barely half values those parameters are of paramount importance in the groundwater management policy

seasonal variations of sediment discharge from the yangtze river before and after impoundment of the three gorges dam abstract over the past decades 50 000 dams and reforestation on the yangtze river changjiang have had little impact on water discharge but have drastically altered annual and particularly seasonal sediment discharge before impoundment of the three gorges dam tgd in june 2003 annual sediment discharge had decreased by 60 and the hysteresis of seasonal rating curves in the upper reaches at yichang station had shifted from clockwise to counterclockwise in addition the river channel in middle lower reaches had changed from depositional to erosional in 2002 during the four years 2003 2006 after tgd impoundment 60 of sediment entering the three gorges reservoir was trapped primarily during the high discharge months june september although periodic sediment deposition continues downstream of the tgd during most months substantial erosion has occurred supplying 70 million tons per year mt y of channel derived sediment to the lower reaches of the river if sand extraction 40 mt y is taken into consideration the river channel loses a total of 110 mt y during the extreme drought year 2006 sediment discharge in the upper reaches drastically decreased to 9 mt only 2 of its 1950 1960s level because of decreased water discharge and tgd trapping in addition dongting lake in the middle reaches for the first time changed from trapping net sediment from the mainstem to supplying 14 mt net sediment to the mainstem severe channel erosion and drastic sediment decline have put considerable pressure on the yangtze coastal areas and east china sea

downstream hydrologic and geomorphic effects of large dams on american rivers abstract the hydrology and geomorphology of large rivers in america reflect the pervasive influence of an extensive water control infrastructure including more than 75 000 dams one hundred thirty seven of the very large dams each storing 1 2 km 3 10 6 acre feet of water or more alter the flows of every large river in the country the hydrologic effects of these very large dams emerge from an analysis of the stream gage records of 72 river reaches organized into 36 pairs one member of each pair is an unregulated reach above a dam whereas the other is a regulated reach downstream from the same structure comparison of the regulated and unregulated reaches shows that very large dams on average reduce annual peak discharges 67 in some individual cases up to 90 decrease the ratio of annual maximum mean flow 60 decrease the range of daily discharges 64 increase the number of reversals in discharge by 34 and reduce the daily rates of ramping as much as 60 dams alter the timing of high and low flows and change the timing of the yearly maximum and minimum flows in some cases by as much as half a year regional variation in rivers dams and responses are substantial rivers in the great plains and ozark ouachita regions have annual maximum mean flow ratios that are 7 times greater than ratios for rivers in the pacific northwest at the same time the ratio of storage capacity mean annual water yield for dams is greatest for interior western ozark ouachita and great plains rivers and least for pacific northwest streams thus in many cases those rivers with the highest annual variability have the greatest potential impact from dams because structures can exert substantial control over downstream hydrology the hydrologic changes by dams have fostered dramatic geomorphic differences between regulated and unregulated reaches when compared to similar unregulated reaches regulated reaches have 32 larger low flow channels 50 smaller high flow channels 79 less active flood plain area and 3 6 times more inactive flood plain area dams also affect the area of active areas the functional surfaces that are functionally connected to the present regime of the river regulated reaches have active areas that are 72 smaller than the active areas of similar unregulated reaches the geomorphic complexity number of separate functional surfaces per unit of channel length is 37 less in regulated reaches reductions in the size of hydrologically active functional surfaces are greatest in rivers in the great plains and least in eastern streams the largest differences in geomorphic complexity are in interior western rivers the shrunken simplified geomorphology of regulated large rivers has had direct effects on riparian ecology producing spatially smaller less diverse riparian ecosystems compared to the larger more complex ecosystems along unregulated reaches of rivers

unraveling the onset of cretaceous oceanic anoxic event 2 in an extended sediment archive from the tarfaya laayoune basin morocco we investigated the onset and development of cretaceous oceanic anoxic event 2 oae2 in a newly drilled core sn degrees 4 from the tarfaya basin southern morocco where this interval is unusually expanded high resolution centimeter scale equivalent to centennial analysis of bulk organic and carbonate stable isotopes and of carbonate and organic carbon content in combination with xrf scanner derived elemental distribution reveal that the ocean climate system behaved in a highly dynamic manner prior to and during the onset of oae2 correlation with the latest orbital solution indicates that the main carbon isotope shift occurred during an extended minimum in orbital eccentricity similar to 400 kyr cycle shorter term fluctuations in carbonate and organic carbon accumulation and in sea level related terrigenous discharge were predominantly driven by variations in orbital obliquity negative excursions in organic and carbonate delta c 13 preceded the global positive delta c 13 shift marking the onset of oae2 suggesting injection of isotopically depleted carbon into the atmosphere the main delta c 13 increase during the early phase of oae2 in the late cenomanian was punctuated by a transient plateau maximum organic carbon accumulation occurred during the later part of the main delta c 13 increase and was associated with climate cooling events expressed as three consecutive maxima in bulk carbonate delta o 18 the extinctions of the thermocline dwelling keeled planktonic foraminifers rotalipora greenhornensis and rotalipora cushmani occurred during the first and last of these cooling events and were likely associated with obliquity paced ocean wide expansions and intensifications of the oxygen minimum zone affecting their habitat space on a global scale

using local moran s i to identify contamination hotspots of rare earth elements in urban soils of london abstract rare earth elements rees in urban soils are receiving more attention because of their increased use in modern technology up to now there is little information about the spatial patterns of rees and their influencing factors in urban soils in this study based on the british geological survey london earth geochemical survey data containing a total of 6467 soil samples collected from the urban area of london the spatial distributions of ce la nd sc sm yb and y and their influencing factors were investigated the element sc is included in this study as related element urban samples were collected at a depth of 0 20 cm and total concentrations of 48 chemical elements were determined in the

equilibrium or indeterminate where sediment budgets fail sediment mass balance and adjustment of channel form green river downstream from flaming gorge dam utah and colorado this study examines bed and bank adjustment in the 105 km reach of the green river immediately downstream from flaming gorge dam by the use of historical aerial and oblique photographs analysis of current and abandoned stream gaging records and field observations although this segment has been previously characterized as sediment deficient these data show that sediment is accumulating in all reaches and that the bed has not degraded at any location where historical data are available adjustment is occurring through a combination of deposition of post dam sediment and stabilization of pre dam deposits resulting in a 10 30 reduction in average width of the channel all post dam surfaces are colonized by woody riparian vegetation the style of channel adjustment varies between geomorphically defined reaches in canyons dominated by debris fans and gravel bedded restricted meandering reaches gravel bars have become inactive and accumulated fine sediment in the sand bedded meandering reaches existing islands have increased in size and new mid channel islands have formed in all of these types of reaches post dam deposits line the banks and sediment has accumulated in side channels that previously separated islands from the bank these findings demonstrate that sediment budgets that show a balance between inputs and outputs cannot necessarily be interpreted to indicate channel equilibrium a sediment mass balance for 150 km reach between the dam and the first long term gage indicates approximate balance of inputs and outputs for the pre and post dam periods when uncertainty in budget components is considered the mass balance is indeterminate although the green river may have been in approximate equilibrium in the pre dam period we have shown that channel width is decreasing in the post dam period the post dam deposits constitute a small but a significant component of the sediment budget upstream from the first major tributary sediment is supplied to this reach by small tributaries and to a lesser extent erosion of pre dam alluvium downstream from the study area the volume of the post dam deposits is tiny relative to the volume of sediment input from the first major tributary d 2005 elsevier b v all rights reserved

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

response of the changjiang yangtze river water chemistry to the impoundment of three gorges dam during 2010 2011 abstract the environmental impact of three gorges dam tgd in the changjiang yangtze river is an important topic of concern for scientific communities and the public however the changes in river water chemistry in response to the dam construction remain poorly constrained this study presents the seasonal variability of all major cations and some anions in the lower changjiang during a full hydrological year from 2010 to 2011 the concentrations of all ions except for hco 3 are higher after the tgd operation than before p

astronomical calibration and global correlation of the santonian cretaceous based on the marine carbon isotope record high resolution records of bulk carbonate carbon isotopes have been generated for the upper coniacian to lower campanian interval of the sections at seaford head southern england and bottaccione central italy an unambiguous stratigraphic correlation is presented for the base and top of the santonian between the boreal and tethyan realms orbital forcing of carbon and oxygen isotopes at seaford head points to the boreal santonian spanning five 405 kyr cycles sa1 to sa5 correlation of the seaford head time scale to that of the niobrara formation western interior basin permits anchoring these records to the la2011 astronomical solution at the santonian campanian sa ca boundary which has been recently dated to 84 19 0 38 ma among the five tuning options examined option 2 places the sa ca at the 84 2 ma 405 kyr insolation minimum and appears as the most likely this solution indicates that minima of the 405 kyr filtered output of the resistivity in the niobrara formation correlate to 405 kyr insolation minima in the astronomical solution and to maxima in the filtered 13c of seaford head we suggest that variance in 13c is driven by climate forcing of the proportions of caco3 versus organic carbon burial on land and in oceanic basins the astronomical calibration generates a 200 kyr mismatch of the coniacian santonian boundary age between the boreal realm in europe and the western interior due either to diachronism of the lowest occurrence of the inoceramid cladoceramus undulatoplicatus between the two regions or to remaining uncertainties of radiometric dating and cyclostratigraphic records

the water level fluctuation zone of three gorges reservoir a unique geomorphological unit three gorges reservoir tgr has provoked a series of unprecedented environmental problems many of which are related to the transitional area between the base and capacity water levels of the reservoir commonly referred to as the water level fluctuation zone we proposed here that this zone serves as a unique geomorphological unit playing an important role of influencing the life of the tgr and named it as the tgr disturbance zone because it has been intensively interrupted by various human activities based on its geomorphological characteristics we divided this zone into three types that have hillside profiles with distinct shapes and gradients grain components and sizes and land uses although the three types of the zone have experienced the same set of geomorphological processes under the new annually cyclic hydrological regime their responses and the associated morphologies are distinguishable thus we depicted them separately accompanied with these processes are geochemical and biological processes that bring about exacerbated pollution and destroyed ecosystem in this zone we elaborated these problems and indicated the potential research directions toward fully understanding the complex geomorphological geochemical and biological processes prevalent in the zone c 2015 elsevier b v all rights reserved

decline in suspended sediment concentration delivered by the changjiang yangtze river into the east china sea between 1956 and 2013 abstract the temporal evolution of suspended sediment concentration ssc in a river debouching into the ocean provides vital insights into erosion processes in the watershed and dictates the evolution of the inner continental shelf while the delivery of sediment from rivers to the ocean has received special attention in the recent past few studies focused on the variability and dynamics of river ssc especially in the changjiang yangtze river china the longest river in asia here variations in ssc delivered by the changjiang river to the east china sea and possible causes of its variability were detected based on a long term time series of daily ssc and monthly water discharge measured at the datong gauging station the ssc data are further compared to a hydrological analysis of yearly precipitation covering the entire catchment the results indicate the presence of a decline in ssc in the period 1956 2013 which can be divided into three phases i high ssc 0 69 kg m3 in the wet season and low ssc 0 2 kg m3 in the dry season from 1956 to 1970 ii relative high ssc 0 58 kg m3 in the wet season and low ssc 0 15 kg m3 in the dry season from 1971 to 2002 and iii low ssc 0 19 kg m3 in the wet season and very low ssc 0 09 kg m3 in the dry season after 2002 these three periods have a mean yearly ssc values of 0 62 0 42 and 0 18 kg m3 respectively compared with 1956 1970 the slope of the rating curve between ssc and water discharge decreased respectively by 2 and 30 during the period 1971 2002 and 2002 2013 soil erosion dam construction and banks reinforcement along the changjiang river are the main causes of ssc variations fluctuations in water discharge are also controlling the ssc long term variations specifically from 1956 to 1970 the effect of soil erosion overrules that of dam impoundment which is likely responsible for the high ssc during the period 1970 2002 the influence of dam impoundment increases while that of soil erosion decreases which together produce a small reduction in ssc since 2002 the impact of soil erosion further decreases and large scale sediment trapping behind the three gorges dam is responsible for the occurrence of extremely low ssc the results presented herein for the changjiang river can inform a better management strategy of sediment resources and water quality for both the river and the coast our conclusions can be well applied to other rivers discharging in the ocean subject to similar human activities

the human role in changing fluvial systems retrospect inventory and prospect historical and modern scientific contexts are provided for the 2006 binghamton geomorphology symposium on thehuman role in changing fluvial systems the 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systems including hydrologic and geomorphic changes to watersheds while also commemorating the 50th anniversary of the 1955man s role in changingthe face of the earth symposium thomas jr w l ed 1956a man srole in changing the face of the earth univ chicago press chicago 1193 pp this paper examines the 1955symposium from the perspective of humanimpacts on rivers reviews current inquiry on anthropogenic interactions in fluvial systems and anticipates future directions in this field although the 1955 symposium did not have an explicit geomorphic focus it set the stage for many subsequent anthropogeomorphic studies the 1955 conference provided guidance to geomorphologists by recommending and practicing interdisciplinary scholarship through the use of diverse methodologies applied at extensive temporal and geographical scales and through its insistence on an integrated understanding of human interactions with nature since 1956 research on human impacts to fluvial systems has been influenced by fundamental changes in why the research is done what is studied how river studies are conducted and who does the research rationales for river research are now driven to a greater degree by institutional needs environmental regulations and aquatic restoration new techniques include a host of dating spatial imaging and ground measurement methods that can be coupled with analytical functions and digital models these new methods have led to a greater understanding of channel change variations across multiple temporal and spatial scales and integrated watershed perspectives all changes that are reflected by the papers in this volume these new methods also bring a set of technical demands for the training of geomorphologists the 2006 binghamton geomorphology symposium complements the 1956 symposium by providing a more specific and updated view of river systems coupled with human interactions the symposium focuses on linkages between human land use structures and channel modification with geomorphology hydrology and ecology the emergence of sustainability as a central policy guideline in environmental management should generate greater interest in geomorphic perspectives especially as they pertain to human activities the lack of theories of anthropogeomorphic change however presents a challenge for the next generation of geomorphologists in this rapidly growing subfield

inferring the heterogeneity transmissivity and hydraulic conductivity of crystalline aquifers from a detailed water table map abstract estimating the transmissivity or hydraulic conductivity field to characterize the heterogeneity of a crystalline aquifer is particularly difficult because of the wide variations of the parameters we developed a new approach based on the analysis of a dense network of water table data it is based on the concept that large scale variations in hydraulic head may give information on large scale aquifer parameters the method assumes that flux into the aquifer is mainly sub horizontal and that the water table is mostly controlled by topography rather than recharge it is based on an empirical statistical relationship between field data on transmissivity and the inverse slope values of a topography reduced water table map this relationship is used to compute a transmissivity map that must be validated with field measurements the proposed approach can provide a general pattern of transmissivity or hydraulic conductivity but cannot correctly reproduce strong variations at very local scale less than10 m and will face of some uncertainties where vertical flows cannot be neglected the method was tested on a peridotite ultramafic rock aquifer of 3 5 km 2 in area located in new caledonia the resulting map shows transmissivity variations over about 5 orders of magnitude average logt 5 2 0 7 comparison with a map based on measured water level data n 475 shows that the comparison between logt computed values and logt data deduced from 28 hydraulic tests is estimated with an error less than 20 in 71 of cases logt 0 4 and with an error less than 10 logt 0 2 on average in 39 of cases from this map a hydraulic conductivity map has been computed showing values ranging over 8 orders of magnitude the repeatability of the approach was tested on a second data set of hydraulic head measurements n 543 the mean deviation between both logt maps is about 11 these encouraging results show that the method can give valuable parameter estimates and can characterize aquifer heterogeneity the computed logt and logk maps highlight the spatial distribution of parameters that show a pattern clearly controlled by the fault network of this ultramafic massif however the faults are mainly characterized by low permeability zones this differs from results on other crystalline aquifers and may be due to the fact that weathering products of peridotite are clay like materials the resulting transmissivity map can be used as a starting point for modelling or to direct additional fieldwork

a new framework for modeling sediment fining during transport with fragmentation and abrasion 1 a new framework for modeling sediment fining during transport is proposed the model is based on a physical description of both abrasion and fragmentation processes it attempts to describe and explain the changes in the grain size distribution of sediments during their transport in a water flow abrasion and fragmentation are modeled through the use of breakage frequency functions and daughter size distributions these functions are determined experimentally for the specific case study which is presented comparison between the predictions from the model and experimental data from the case study show that 1 both abrasion and fragmentation are involved in the degradation 2 fragmentation efficiency decreases during the experiment and 3 the shape of the pebbles provides feedback between abrasion and fragmentation this type of model is therefore appropriate for explaining degradation mechanisms which is promising for a future application to rivers

late cretaceous orbitally paced carbon isotope stratigraphy from the bottaccione gorge italy abstract a refined astronomical tuning of the upper albian lower campanian is proposed from the bottaccione reference section gubbio central italy long term eccentricity cycles filtered from a high resolution 13c record were tuned to the highly stable 405 kyr cycles of the new la2010 astronomical solution for the earth s orbital elements the achieved orbital tuning provides a new precise and accurate age model for dating biostratigraphic magnetostratigraphic and carbon isotope events through a 23 myr long record cycles of 8 0 4 7 3 4 and 2 4 myr modulate the entire 13c record thus extending their detection from the cenozoic to 100 ma and represent primary and stable long term oscillation modes of earth s climate ocean system although an ultimate driver of these long term periodicities is lacking we speculate that specifically the periodicity at 4 7 myr represents a homologue of the present eccentricity grand cycles evolved by the chaotic behaviour of solar system planets during the mesozoic the long term periodicities potentially reflect an unexplored expression of the low frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients particularly phosphorus associated with modulation of inputs to the ocean in turn triggered by high order marine transgressions and formation of highly productive shelf seas this very long term eccentricity control modulated by periodic low energy cycles is suggested to play a crucial role in carbon cycling controlling a chain of climate sensitive global biogeochemical processes on the earth finally these grand cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the solar system

relationship between hydrogeological parameters for data scarce regions the case of the araripe sedimentary basin brazil this paper applies and validates a method for generating spatially distributed hydraulic conductivity k based on the specific capacity qs for data scarce regions this method has been applied to the araripe sedimentary basin brazil and consists of four steps 1 selection of 32 wells for which both k and qs data are available 2 estimation of k as a function of qs for the 128 wells for which only specific capacity data are available 3 spatial distribution of k using the kriging geostatistical tool 4 validation of the method using 17 representative wells with k measured data the equation relating k and qs showed a statistically significant linear relationship r 0 93 from which a database has been generated using kriging with the spherical model the results showed a calibration coefficient of nash and sutcliffe ns of 0 54 and moderate spatial dependence ratio of 69 the validation process provided only a moderate efficiency ns 0 22 possibly due to the geological complexity of the focus system despite its limitations the method indicates the possibility of application of ordinary kriging to generate reliable data from auxiliary variables especially for the water management of data scarce areas

radium isotopes and their environmental implications in the changjiang river system abstract radium ra isotopes are widely used to trace water motion and nutrient transport in coastal oceans to enhance our understanding of ra behavior from river to ocean this study examines 226 ra and 228 ra activity concentrations in the water column suspended particulate matter and river bed surface sediments along the middle and lower changjiang river cjr basin based on two cruises in 2006 and 2008 the results show that the ra activity concentrations in the cjr basin are comparable with other rivers in the world higher ra activity concentrations and lower 228 ra 226 ra activity ratios are detected in the tributaries i e in the dongting and poyang lakes than in the mainstream the comparison of pre three gorges dam tgd data taken in 1984 and post tgd data this work illuminates the effect that a major dam has on radium transport within the river and into the estuary we estimate a riverine 226 ra flux of 1 04 0 08 tbq yr 1 extended ra datasets collected in the estuary and the east china sea show that the dissolved and sedimentary ra activity concentrations are higher in the estuary but lower in the sea whereas the particulate ra activity concentrations are larger in the river this finding indicates significant ra desorption from particulate to dissolved phase in the brackish estuary where riverborne materials are filtered and trapped overall these results help to elucidate ra transport from river to ocean and assist further application of ra isotopes in land ocean interaction studies such as submarine groundwater discharge mixing and diffusion processes and determination of water mass and or current structures in the estuarine and coastal zones

geomorphic response of the jingjiang reach to the three gorges project operation upstream damming often causes significant downstream geomorphic adjustments remarkable channel changes have occurred in the jingjiang reach of the middle yangtze river since the onset of the three gorges project tgp therefore it is important to investigate the variations in different fluvial variables for better understanding of the channel evolution characteristics as an example of the jingjiang reach recent geomorphic adjustments in the study reach have been investigated quantitatively including variations in sediment rating curve fluvial erosion intensity channel deformation volume and bankfull channel geometry these fluvial variables adjusted in varying degrees in response to the altered flow and sediment regime caused by the tgp operation a focus of this study has been especially paid on the variation in the bankfull channel geometry calculated bankfull dimensions at section and reach scale indicate that i there were significant bank erosion processes in local regions without bank protection engineering with empirical relations being developed to reproduce the variation in bankfull widths at four typical sections ii the variation in the reach scale channel geometry occurred mainly in the component of bankfull depth owing to the construction of large scale bank revetment works with the depth increasing from 13 7 m in 2002 to 15 0 m in 2014 and with an increase in the corresponding bankfull area of about 11 and iii the reach scale bankfull channel dimensions responded to the previous five year average fluvial erosion intensity during flood seasons at zhicheng with higher correlations for the depth and area being obtained when calibrated by the measurements in 2002 2012 furthermore these developed relations for the section and reach scale bankfull channel geometry were also verified by the observed data in 2013 2014 with encouraging results being obtained this article is protected by copyright all rights reserved

a critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for late cretaceous global correlation abstract climate variability is driven by a complex interplay of global scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter regional correlation which in most cases cannot be obtained with biostratigraphic methods alone chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high resolution correlation over large distances but complications arise from a multitude of possible influences from local differences in biological diagenetic and physico chemical factors on individual 13c records that can mask the global signal to better assess the global versus local contribution in a 13c record it is necessary to compare numerous isotopic records on a global scale as a contribution to this objective this paper reviews bulk sediment 13ccarb records from the late cretaceous in order to identify differences and similarities in secular 13c trends that help establish a global reference 13c record for this period the study presents a global scale comparison of twenty 13c records from sections representing various palaeo latitudes in both hemispheres and different oceanic settings from the boreal tethys western interior indian ocean and pacific ocean and with various diagenetic overprinting the isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute 13c values and variation in amplitude between the sites these differences reflect the varying local influences e g from depositional settings bottom water age and diagenetic history whereas the concordant patterns in 13c shifts might represent 13c fluctuations in the global seawater dissolved inorganic carbon the latter is modulated by variations in organic matter burial relative to re mineralization in the global scale formation of authigenic carbonate and in partitioning of carbon between organic carbon and carbonate sinks these variations are mainly controlled by changes in climate and eustasy additionally some globally synchronous shifts in the bulk 13ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and thus can be globally synchronized by fluctuations in eustasy atmospheric and oceanic oxygen levels or in large scale oceanic circulation because the influence of early diagenetic cements on the bulk 13ccarb signal can but need not be synchronized chemostratigraphy should not be used as a stand alone method for trans continental correlation and especially minor isotopic shifts have to be interpreted with utmost care nevertheless the observed consistency of the 13c correlations confirms global scale applicability of bulk sediment 13c chemostratigraphy for the late cretaceous including sediments that underwent lithification and burial diagenesis such as the sediments from the himalayan and alpine sections limitations arise from increased uncertainties 1 in sediments with very low carbonate content 2 from larger 13c variability in sediments from very shallow marine environments 3 from unrecognized hiatuses or strong changes in sedimentation rates and 4 in sections with short stratigraphic coverage or with few biostratigraphic marker horizons the combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes facies or provincialism of key fossils by using an iterative approach to stepwise increase precision of the correlations isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested which helps to improve biostratigraphic zonations to assess zonal boundary ages and to identify useful criteria for defining late cretaceous stage boundaries many of which are still not formally defined the presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid cretaceous sea level high whereas diachroneity appears to be more pronounced during the late campanian and maastrichtian global sea level fall a similar pattern is observed for trans continental consistency in the 13c shifts graphic correlation of isotopic shifts magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo and magnetostratigraphy finally an attempt of a global average 13c stack is presented for the turonian through maastrichtian

the impact of climate change human interference scale and modeling uncertainties on the estimation of aquifer properties and river flow components summary within the period 1978 2006 climate change and human interferences produced noticeable impacts on the hydrology of a small watershed known as the beca river basin climate change was characterized by a persistent raise in temperature 0 78 c decade 1 and a drop in the annual rainfall 300 mm decade 1 human interferences included the construction of a dam for electric power generation in 1998 and since then the transference of beca river flows from the dam lake to the adjacent t mega river the impacts on catchment hydrology comprised a decline of aquifer hydraulic conductivity and effective porosity by approximately one order of magnitude related to a water table lowering of about 17 m within the bedrock aquifer composed of weathered and fractured hercynian granites and paleozoic metassediments and of saprolite layers derived therefrom aquifer property estimates were compared across spatial scales namely the beca river and the nested sub basins scale sub basin aquifers are more porous and permeable than the basin aquifer because corresponding hydraulic circuits are shallower comparisons were also made between aquifer properties derived from measured and simulated stream flows which revealed effects of modeling uncertainties on the results river flows also suffered a substantial decrease in the course of climate change and human interference especially the overland flows 4 5 decrease and the base flows 2 3 decrease the inter flows were less affected 1 3 decrease because they were partly fed with water from the aquifer storage which in turn underwent depletion the hydrologic changes in the beca river basin anticipate important impacts on the local use of natural water in this context the aforementioned water table lowering may have caused limited access to shallow groundwater for activities such as crop irrigation from dug wells whereas the severe decline in overland flows and base flows had certainly reduced the availability of surface water for the refilling of dam lakes and of groundwater for the supply of public and private boreholes

lynchets in eastern belgium a geomorphic feature resulting from non mechanised crop farming abstract this paper investigates soil stratigraphy of lynchets in sloping lands in eastern belgium and rates of their development by comparison to tillage translocation by non mechanised agriculture in belgium detailed topographical surveys and augerings were carried out at three sites that were under cropland till 1900 1950 rates and diffusion constants of current non mechanised tillage erosion were monitored in ethiopia using tracers and by precise surveys of tillage steps of known ages the lynchets in belgium consist of colluvium that was removed at the upper border of previously farmed plots repeated tillage with animal drawn implements results in soil translocation fluxes to the lower plot borders in the order of 11 to 91 kg m 1 year 1 for slope gradients between 0 03 and 0 35 m m 1 the studied lynchets in eastern belgium would have required cropping agriculture for a total of 217 585 years on steep and 1037 1867 years on gentle slopes the establishment of lynchets hence took place without any deliberate action of digging but due to repeated tillage even with simple implements and water erosion calculated time spans of tillage indicate that some parts of the study area had already been under cultivation during the gallo roman period others since the middle ages

spatial distribution of soil organic carbon concentrations in grassland of ireland abstract soil organic c soc concentrations in topsoil samples taken at 678 sites in the grassland of ireland were investigated using statistics and geostatistics soc concentrations walkley black method follow a lognormal distribution with a median and geometric mean of 5 0 and an arithmetic mean of 5 3 statistically significant p

estimate of cumulative sediment trapping by multiple reservoirs in large river basins an example of the yangtze river basin article most existing models are unable to model large spatial pattern of reservoir sedimentation due to the difficulty in accounting for trapping by upstream reservoirs in a multiple reservoir system in this study we developed and applied a framework on 1358 of large and medium sized reservoirs 10 7 maximum storage capacity for calculating reservoir sedimentation rates in the multi reservoir yangtze river system while accounting for the effect of reduced sediment input due to upstream traps we further used statistical inferences to assess the sedimentation rates of remaining 42 000 smaller reservoirs our results indicate that annual sediment accumu lated in the yangtze reservoirs is approximately 691 93 7 million tons mt 669 89 1 mt of which is trapped by 1358 large and medium sized reservoirs and 22 4 6 mt is trapped by smaller reservoirs despite the large amount of sediment trapped by reservoirs the reduction in sediment load at outlet datong station was merely 305 mt over the last 60 years the difference may reflect uncertainties in estimates but it also indicates the important discrepancy between the estimate of the current rate of sediment sequestration in reservoirs and the estimate of the reduction in the land ocean sediment flux we further estimated a mean annual rate of storage loss of 5 3 10

shoal morphodynamics of the changjiang yangtze estuary influences from river damming estuarine hydraulic engineering and reclamation projects abstract concerns regarding estuarine shoal morphodynamics have increased worldwide because of intensive anthropogenic activities to explore response of estuarine shoals to possible couplings of multiple artificial interferences in river basins and within estuaries the link between the morphodynamic processes of the nanhui shoal nhs which is located along the southern margin of the changjiang estuary the largest estuary in asia and river damming estuarine hydraulic engineering and reclamation projects is discerned in this study the results reveal that the nhs exhibited secular polarization during 1998 2013 with a significant accretion of 1 8 10 8 m 3 landward from the tidal ridge and an erosion of 0 3 10 8 m 3 on the seaward edge respectively forming a steep slope with an elevation between 2 and 3 m meanwhile the nhs morphodynamics could be divided into 3 stages mild accretion with an undisturbed tidal channel during 1998 2002 strong sedimentation with a disrupted tidal channel during 2003 2008 and large scale landward accretion with an infilled tidal channel after 2009 moreover the nhs s volume variations exhibited an 18 month cycle even though an increased area of 35 km 2 above 2 m and a decreased area of 45 km 2 between 2 and 5 m were observed the primary causes of theses periodic changes in the nhs s volume are determined as the fluctuating changjiang water discharge and cyclically altered hydrodynamics of the south passage the deep waterway project dwp and reclamation projects were responsible for the polarization of seaward erosion and landward accretion respectively moreover these reclamation projects dominated the staggered changes in nhs morphodynamics by inducing continuous accretion within the tidal channel compared to estuarine engineering river damming induced dramatic declines in distal sediment may have played a minor role in flat changes of nhs

hydrogeological and hydrochemical characterization of the voltaian basin the afram plains area ghana in the afram plains area groundwater is the main source of water supply for most uses the area is underlain by aquifers of the southern voltaian sedimentary basin which are predominantly sandstones mudstones conglomerates and shale ordinary least squares regression analysis using 41 well test data from aquifers in the afram plains portion of the voltaian system reveals that transmissivity t exists in a non linear relationship with specific capacity sc the analysis reveals that t 0 769sc1 075 with r 2 0 83 for aquifers in the area the mudstone conglomerate aquifer in the area appears to be the most variable in terms of both specific capacity and transmissivity with transmissivity ranging from 0 18 to 197 7 m2 day and 0 5 and 148 5 m3 day m respectively horizontal fractures and joints resulting from secondary fracturing appear to be the main determinants of both transmissivity and specific capacity in the area phreeqc modeling and mineral stability diagrams indicate that groundwater quality in the afram plains area is controlled by the incongruent weathering of silicate minerals in the aquifers these processes concentrate calcium sodium magnesium potassium bicarbonate ion and quartz leading to calcite dolomite and aragonite supersaturation at most locations hierarchical cluster analysis performed on the raw chemical data reveals two main water types or facies the calcium sodium chloride bicarbonate facies and the magnesium potassium sulfate nitrate facies for the southern and northern sections of the afram plains area respectively

the impacts of the three gorges dam upon dynamic adjustment mode alterations in the jingjiang reach of the yangtze river china abstract dam operation profoundly modifies downstream flow sediment regimes resulting in a variety of geomorphologic responses without uniform laws the jingjiang reach of the middle yangtze river has undergone significant adjustment mode alterations with intensive channel erosion and major adjustment area changing from the bankfull channel to the medium flow channel at the time boundary of the three gorges dam tgd impoundment while these changes have received some attention little work has been undertaken to reveal the reason in this study based on 172 cross sections measured in the post flood period from 2003 to 2015 different river patterns longitude and reach averaged channel dimensions were assessed to reflect the channel adjustment characteristics of the jingjiang reach an index has been proposed to measure the cumulative water transport capacity of each discharge interval and to assess the relationship with reach scale medium flow channel dimensions the results indicate that the channel adjustment changes are directly driven by the alterations of flow duration and sediment transport capacity with the deficiency of floods medium flow channels respond quite well to small and medium discharges of under approximately 16 500 m3 s a discharge of 16 500 m3 s which can be regarded as a critical threshold corresponds to the average top levels of braided and meandering channel bars which are of morphological significance in constraining the passing flow in the medium flow channel small and medium discharges under the critical threshold associate with relatively larger reductions in sediment loads and hold increased geomorphic impacts qmjp eventually resulting in adjustment mode alterations the results present herein for the jingjiang reach of the yangtze river can provide a better understanding of dam operation and the corresponding impacts on downstream channel morphology

effects of three gorges dam operation on spatial distribution and evolution of channel thalweg in the yichang chenglingji reach of the middle yangtze river china abstract the evolution of the channel thalweg and pool riffle sequences is a critical feature of morphological adjustments in fluvial systems and might have important effects on aquatic habitat quality channel stability and navigation based on the 220 cross sectional profiles from 2002 to 2016 residual depths and spatial statistical analyses were used to quantitatively analyse the vertical variations and longitudinal distribution of the pool riffle sequences and channel thalweg in the yichang chenglingji reach ycr of the middle yangtze river which consists of the yizhi zhijiang shashi gongan and shishou jianli sub reaches the results showed that the dramatic reduction in the sediment loads following the construction of the three gorges dam tgd has caused significant adjustments in the size morphological diversity and spatial distribution of pool riffle structures in the ycr the average depth of the pools in the yizhi zhijiang reach and the shishou jianli reach overall exhibited a nonlinear growth trend with the average residual depth increasing by 1 4 m and 1 9 m respectively however the average residual depth in the shashi gongan reach showed a decreasing trend with a reduction of approximately 1 2 m the longitudinal lengths of the riffles in all three reaches contracted to different degrees and the specific percentage of longitudinal river length occupied by riffles total riffle length total sub reach length decreased by 8 9 6 and 5 9 in the three sub reaches from upstream to the downstream in addition the morphological diversity of the thalweg elevation in the shashi gongan reach and shishou jianli reach weakened after the construction of the tgd while the bed topography in the yizhi zhijiang reach became more complex and diverse moreover the pool riffle structures in the ycr were rearranged and distributed regularly following the initiation of the tgd operation although the variation characteristics of the average pool spacing in the three sub reaches were quite different quantitative relationship between the average residual depth and the previous four year hydrological condition was proposed for the three sub reaches based on the delayed response model drm and verified using the measurements from 2013 to 2016

impacts of large dams on downstream fluvial sedimentation an example of the three gorges dam tgd on the changjiang yangtze river summary under the influence of climate and human activities fluvial systems have natural ability to make adjustments so that the river hydrology sediment movement and channel morphology are in dynamic equilibrium taking the changjiang yangtze river for example in the early stages after the three gorges dam tgd began operational ten years ago the suspended sediment content ssc and fluxes in the middle and lower reaches of the river decreased noticeably at present they appear to be in a stable state on the decadal scale although the river runoff has not shown any trends the water level in the river decreased appreciably in time in the meantime channel down cutting along the thalweg almost existed throughout the river course the riverbed has turned from depositional before the dam construction to erosional afterwards in other words the riverbed had turned from being sediment sinks to sediment sources in the main channel of the changjiang between yichang and nanjing a distance of 1300 km the riverbed sedimentation mode displays strong intermediate and weak erosion depending on the closeness to the tgd

relative changes in sediment supply and sediment transport capacity in a bedrock controlled river rivers can be affected by multiple natural and human induced changes to sediment supply and to sediment transport capacity assessment of the relative importance of these changes enables appropriate river management here assessments are made of the relative changes in sediment supply and sediment transport capacity of an 83 km section of the bedrock controlled coxs river new south wales australia these relative changes are estimated in turn for land degradation historical climate variations and dam closure measurements of gully erosion extent from aerial photographs indicate that since european settlement the average annual sediment supply to the river has increased by a factor of 20 rainfall records and flow gauging records show a climate shift in the mid 1940s on the basis of hydrologic modeling the increased streamflow in the period since the mid 1940s is estimated to have increased sediment transport capacity by a factor of almost 3 closure of lyell dam in 1982 stopped sediment supply from the upper catchment on the basis of hydrologic modeling the flow regulation and abstraction at the dam is estimated to have reduced the long term average sediment transport capacity downstream by 15 the current sediment transport capacity after the climate shift and dam closure is 2 6 times higher that in the first half of this century in spite of this net increase in sediment transport capacity the huge volume of sediment delivered to the channel from gully erosion has led to widespread sand deposition along much of the river much of the river bed that was previously dominated by bedrock is now alluvial in character only the steepest reaches remain bedrock dominated

applicability of method to estimate transmissivity based on yield drawdown analysis in mountainous fractured rock aquifers a case study in taiwan abstract the observation of yield drawdown response in the course of pumping test as well as its derived application for aquifer characterization is an essential practice in a geotechnical investigation on the basis of that for providing a reasonable estimate of aquifer transmissivity on site a number of empirical models have therefore been proposed yet the majority of previous studies are conducted based on investigations at homogeneous alluvial plain very few particularly in the case of taiwan are carried out focusing on mountainous fractured rock aquifers aiming to address this problem the observation data of 53 pumping tests obtained from a multi years in situ geological investigation program are analyzed and the applicability of empirical log log linear relationship between t and q s is examined our analysis reveals that the yield drawdown responses derived from different geologic formations are quantitatively distinct and those empirical rules derived from the alluvial landform should be used with care when applying in mountainous fractured rock aquifers based on the analysis of statistical results in our study with a systematic investigation and clarification of the q s relationship in advance a satisfactory and cost effective solution is obtained

miocene pleistocene volcanism and tectonics in southern korea and their relationship to the opening of the japan sea abstract miocene pleistocene volcanism and tectonics in southern korea are discussed the miocene volcanism and related tectonics are represented by the eoil orogeny which occurred in the yangnam and pohang basins in the southeastern corner of the korean peninsula the yangnam and pohang basins represent the uplifted central part of the pohang ulsan graben which was rifted between the proto korean peninsula and paleo ulleung land probably in late oligocene early miocene times the eoil orogeny is correlated with the green tuff orogeny in japan evidence of pliocene volcanism is observed on ulleung island located in the western part of the central japan sea volcanic and tectonic events represented on ulleung island are in chronological order 1 volcanic eruption 2 subsidence and marine transgression 3 dome like uplift and 4 volcanic eruption evidence of pleistocene volcanism is present on cheju island located at the southwestern entrance to the korea tsushima strait volcanic and tectonic events represented on cheju island are in chronological order 1 volcanic eruption 2 subsidence and marine transgression 3 uplift and volcanic eruption and 4 doming and volcanic eruption three grabens namely the pohang ulsan graben the ulleung basin and the yamato basin were formed in the southern half of the japan sea which was above sea level in early miocene times paleo ulleung land was present between the pohang ulsan graben and the ulleung basin in miocene pliocene times these three grabens are active rifts and the tectonic events that occurred in this region originated from the action of rising magma the extension and deepening of the southern half of the japan sea resulted from the tectonic movements of these active rifts and their surrounding regions thus it is suggested that the opening of the japan sea progressed by diapiric tectogenesis

upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale in deeply weathered crystalline aquifers two innovative approaches for upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale are proposed they are based on the concept that large scale variations in hydraulic head may characterize large scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering located in south india maheshwaram watershed 53 km2 both methods are based on field data such as water levels discharge rates of irrigation wells geological observations and the results of small scale hydraulic tests the resulting hydraulic conductivity map uses the statistical empirical relationship between log normal distributions of hydraulic conductivity from small scale tests and linear discharge rates from exploited wells i e the ratio between discharge rate and the saturated aquifer thickness the empirical relationship agrees with thiem dupuit s assumption for unconfined aquifers the performance of the method was compared to the values of local hydraulic conductivity estimates deduced from small scale tests not used for drawing the map about 90 of simulated values varies less than 20 from local measurements logk 0 4 on average which is reasonable considering the complexity of the studied fractured aquifer the regionalization of the effective porosity was based on a method that combines both water table fluctuation and groundwater budget techniques in the absence of recharge from rainfall however the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells which here is unknown to avoid this difficulty a coarse graining method was used assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell our results show that cell sizes over 520 520 m achieve a negligible balance in addition porosity maps provide average values of around 1 5 that are almost identical to the ones previously found at watershed scale the proposed methods for regionalizing hydraulic conductivity and porosity fields provide access not only to the average large scale values but also to their spatial distribution which is of prime interest in terms of flux and contaminant transport in a hard rock environment the uncertainty introduced by field data the choice of the computation scale as the impact of cell size on the calculated effective porosity value and the possible meaning of their spatial variations are also discussed

ra tracer based study of submarine groundwater discharge and associated nutrient fluxes into the bohai sea china a highly human affected marginal sea nutrient concentrations in coastal bays and estuaries are strongly influenced by not only riverine input but also submarine groundwater discharge sgd here we estimate the sgd and the fluxes of the associated dissolved inorganic nitrogen din phosphorus dip and silicon dsi into the bohai sea based on a 226ra and 228ra mass balance model this procedure shows that in the bohai sea the average radium activities dpm 100 l 1 are 42 8 6 3 226ra and 212 41 7 228ra for the surface water and 43 0 6 1 226ra and 216 38 4 228ra for the near bottom water according to the 228ra 226ra age model the residence time in the bohai sea is calculated to be 1 7 0 8 yrs the mass balance of 226ra and 228ra suggests that the yearly sgd flux into the whole bohai sea is 2 0 1 3 1011 m3 yr 1 of which the percentage of submarine fresh groundwater discharge sfgd to the total sgd is approximately 5 1 4 1 however the din and dsi fluxes from sfgd constitute 29 and 10 respectively of the total fluxes from the sgd moreover nutrient loads which exhibit high din dip from sgd especially the sfgd may substantially contribute to the nutrient supplies resulting in the occurrence of red tide in the bohai sea

bedform characteristics during falling flood stage and morphodynamic interpretation of the middle lower changjiang yangtze river channel china article a survey was conducted to examine river bedforms using side scan sonar sub bottom profiler and an acous tic doppler profiler in the middle lower mid lower changjiang yangtze river downstream of wuhan china during august 14 20 2003 when the discharge was 27 000 36 000 m 3 s 1 the results show bedforms of a range of sizes occur in the channel and their heights and lengths follow an exponential correlation below flemming s maximum line not all bedforms were formed under the flow conditions experienced during the survey as shown by comparison to three existing models in the literature small scale bedforms with a length b60 m defined as flat bed mega ripple and small dune in the present study are mostly in equilibrium and are probably formed under the existing flowconditions the large dunes witha lengthofn60 m are not in equilibrium and are believed to be the relicts of previous largedischargesnow undergoing adjustment different bedform types occur in the five riverreaches inthis section of the changjiang wuhan tianjiazhen tianjiazhen anqing anqing maanshan maanshan jiangyin and jiangyin estuary downstream in the narrow and single channel reaches above anqing large small dunes are limited to the channel with higher water surface slope where stream power is strong enough for riverbed sediments to be moved frequently in the downstream reaches be tween anqing and jiangyin characterized by anabranching channels small scale bedforms superimposed on large dunes occur widely due to intensive riverbed sediment transport from frequent diverging converging flow during both floods and low flow periods mega ripples and flat beds prevail in the lowermost channel

large scale dam removal on the elwha river washington usa source to sink sediment budget and synthesis abstract understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology but opportunities to study such processes at field scales are rare the phased removal of two large dams on the elwha river washington exposed 21 3 million m3 or 30 million tonnes t of sediment that had been deposited in the two former reservoirs allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply here we provide a source to sink sediment budget of this sediment release during the first two years of the project september 2011 september 2013 and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms owing to the phased removal of each dam the release of sediment to the river was a function of the amount of dam structure removed the progradation of reservoir delta sediments exposure of more cohesive lakebed sediment and the hydrologic conditions of the river the greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine silt and clay and coarse sand and gravel sediments were spilling past the former dam sites after both dams were spilling fine and coarse sediments river suspended sediment concentrations were commonly several thousand mg l with 50 sand during moderate and high river flow at the same time a sand and gravel sediment wave dispersed down the river channel filling channel pools and floodplain channels aggrading much of the river channel by 1 m reducing river channel sediment grain sizes by 16 fold and depositing 2 2 million m3 of sand and gravel on the seafloor offshore of the river mouth the total sediment budget during the first two years revealed that the vast majority 90 of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal waters where slightly less than half of the sediment was deposited in the river mouth delta although most of the measured fluvial and coastal deposition was sand sized and coarser 0 063 mm significant mud deposition was observed in and around the mainstem river channel and on the seafloor woody debris ranging from millimeter size particles to old growth trees and stumps was also introduced to fluvial and coastal landforms during the dam removals at the end of our two year study elwha dam was completely removed glines canyon dam had been 75 removed full removal was completed 2014 and 65 of the combined reservoir sediment masses including 8 mt of fine grained and 12 mt of coarse grained sediment remained within the former reservoirs reservoir sediment will continue to be released to the elwha river following our two year study owing to a 16 m base level drop during the final removal of glines canyon dam and to erosion from floods with larger magnitudes than occurred during our study comparisons with a geomorphic synthesis of small dam removals suggest that the rate of sediment erosion as a percent of storage was greater in the elwha river during the first two years of the project than in the other systems comparisons with other pacific northwest dam removals suggest that these steep high energy rivers have enough stream power to export volumes of sediment deposited over several decades in only months to a few years these results should assist with predicting and characterizing landscape responses to future dam removals and other perturbations to fluvial and coastal sediment budgets

relationship between transmissivity and specific capacity in the volcanic aquifers of jeju island korea abstract transmissivity is often estimated using specific capacity data when standard pumping test data are not available or the drawdown is stabilized early as in this study previous researchers studied the relationship between transmissivity and specific capacity in the leaky aquifer system of volcanic rocks on jeju island korea using the cooper jacob equation the current study utilizes the moench leaky aquifer model the linear relationship between transmissivity and specific capacity on a log log scale for volcanic aquifers on jeju island is remarkably strong with a correlation coefficient of 0 94 the width of the 90 prediction interval is about 0 89 log cycles indicating a 0 44 order of magnitude uncertainty when transmissivity is estimated using specific capacity

a methodology for regionalizing 3 d effective porosity at watershed scale in crystalline aquifers 13 an innovative approach for regionalizing the 3 d effective porosity field is presented and 14 applied to two large overexploited and deeply weathered crystalline aquifers located in 15 southern india the method derives from earlier work on regionalizing a 2 d effective 16 porosity field in that part of an aquifer where the water table fluctuates which is now 17 extended over the entire aquifer using a 3 d approach a method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 saprolite and fractured layers the method for regionalizing 3 d effective porosity 20 combines water table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data for groundwater abstraction the structure of the 22 weathering profile and geostatistical techniques the approach is presented in detail for the 23 kudaliar watershed 983 km 2 and tested on the 730 km 2 anantapur watershed at watershed 24 scale the effective porosity of the aquifer ranges from 0 5 to 2 in kudaliar and between 25 0 3 and 1 in anantapur which agrees with earlier works results show that i depending 26 on the geology and on the structure of the weathering profile the vertical distribution of 27 effective porosity can be very different and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in effective porosity and ii that the lateral 29 variations in effective porosity can be larger than the vertical ones these variations suggest 30 that within a same weathering profile the density of open fractures and or degree of 31 weathering in the fractured zone may significantly varies from a place to another 32 the proposed method provides information on the spatial distribution of effective porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers 34 implications for mapping groundwater storage and scarcity are also discussed which should 35 help in improving groundwater resource management strategies 36 37

estimation of transmissivity from specific capacity data in fractured carbonate rock aquifer central jordan transmissivity of an aquifer is determined from pumping test analysis but due to the difficulty of performing such tests as well as the relatively high cost of these test it is often estimated from specific capacity data in this study an empirical relation is derived using 237 pairs of transmissivity and specific capacity values that are obtained from groundwater wells penetrating a fractured and karstified carbonate aquifer linear and logarithmic regression functions have been performed and it is found that the logarithmic relationship predicting transmissivity from specific capacity data has a better correlation r 0 95 than linear one r 0 84 this is logically true because both transmissivity and specific capacity are lognormally distributed the spatial distribution of transmissivity is also affected by the presence of fracturing and karstification phenomena within the aquifer matrix

historical changes in 239pu and 240pu sources in sedimentary records in the east china sea implications for provenance and transportation abstract concentrations and isotopic compositions of plutonium pu are widely used for its source identification and to determine transport processes of pu associated particulate matter and water we investigated the concentrations of 239pu and 240pu and their ratios in a number of sediment samples from the east china sea ecs collected in the summer of 2013 august 6 28 the 239 240pu activity concentrations in surface sediment samples were found to range between 0 048 and 0 492 bq kg 1 and the 240pu 239pu atom ratios showed a similar trend as that of the 239 240pu activities the pu atom ratios ranged from 0 158 to 0 297 and were mostly higher than the mean global fallout value of 0 18 the 239 240pu inventories in the ecs varied widely from 2 to 807 bq m 2 with the highest values commonly found in the coastal areas in the yangtze estuary the mean 239 240pu activity concentration is close to the estimated value of the suspended material from the yangtze river catchment 0 18 bq kg 1 and the 240pu 239pu atom ratio was found to be 0 18 which indicates that the yangtze river input is the dominant source of pu for this area the total annual yangtze river input of 239 240pu was estimated to be 2 4 10 10 bq which is small compared to the total amount of 239 240pu buried 3 1 10 13 bq in the whole ecs the pacific proving ground input appears to be the dominant source of pu to the ecs accounting for 45 52 of the total inventory the fractional amount of 239 240pu scavenged from the total 239 240pu transported by the kuroshio current kc and taiwan warm current twc into ecs sediments is estimated to be 10 our study shows that the 240pu 239pu atom ratio is useful not only to obtain a better insight of the biogeochemistry influenced by the kc but also to trace the long range transport of other particle reactive species besides the sedimentation rates obtained based on the penetration depths of 239 240pu and vertical profiles of excess 210pb agree within uncertainties which suggests that 239 240pu can potentially be used as a chronostratigraphic time marker in the marine environment

channel sedimentation and erosion of the jiangsu reach of the yangtze river during the last 44 years river channel sedimentation in the lower reaches of the yangtze river can be affected by both changes in sea level and changes in solid discharge from the upper river to evaluate dynamic changes of sedimentation and erosion in the jiangsu reach of the yangtze river about 330 km in length from 1959 to 2003 databases were designed and constructed using a digital elevation model dem of channel topography based on the jiangsu river relief map for 1959 1970 1985 1992 and 2003 the results indicated that the main course of the yangtze river in jiangsu province had experienced an obvious switch from sedimentation to erosion status around 1985 because of the decreasing amount of solid load from the upper parts of the river channel after that year the sedimentation process in the main course of the jiangsu reach of the yangtze river demonstrated the propulsive process of downstream ward aggradations between 1985 and 2003 the erosion rate of the lower segment was greater than those of the middle and upper segments this is probably because both channel flow and tide current had influenced the lower segment when channel flow combines with tide current in the same direction channel erosion can be intensified especially if there is a solid load shortage in the channel copyright 2009 john wiley sons ltd

delta changes in the pearl river estuary and its response to human activities 1954 2008 abstract this paper is concerned with delta evolution in response to human activities in the pearl river estuary utilizing more than 50 years data bathymetric data together with simulation fluvial discharge data the net accretion rate in the lingdingyang subaqueous delta decreased from 16 6 mm y over the period 1955 1964 to 1 6 mm y for the period 1998 2008 because there was a dramatic downward trend in the sediment load in particular the closure of the longtan dam ltd in 2006 resulted in the sediment load entering the pearl river falling from 75 mt y annual average 1954 2006 to 25 2 mt y a decrease of 67 another reason may be sand mining in the lingdingyang estuary based on the linear relationship between sediment load and accumulation rate an annual average sediment load of 21 7 mt y carried into the lingdingyang estuary is the critical threshold value that separates delta progradation from recession however the outer subaqueous delta in the modaomen estuary underwent deposition in the same period because there is no obvious change in sediment load into the area during 1954 2008 in the coming decades ongoing human interferences will reduce the fluvial sediment load entering the sea which probably will result in a phase of general delta recession replacing delta progradation

submarine groundwater borne nutrients in a tropical bay maowei sea china and their impacts on the oyster aquaculture submarine groundwater discharge sgd has been recognized as an important pathway for nutrients into estuaries coasts and the adjacent seas in this study 222rn was used to estimate the sgd associated nutrient fluxes into an aquaculture area in a typical tropical bay maowei sea china the sgd into the maowei sea during june of 2016 was estimated to be 0 36 0 33 m d 1 and was associated with sgd derived dissolved inorganic nitrogen din dissolved inorganic phosphorus dip and dissolved silicon dsi fluxes mol d 1 of 4 5 5 5 106 5 3 9 1 104 and 9 4 9 3 106 respectively the sgd derived nutrients i e din dip and dsi were more than 1 9 0 9 and 3 6 times the amounts in the local river input and served as dominant sources in the nutrient budgets in the maowei sea moreover the n p ratios in the sgd around the maowei sea were high mean 64 and these ratios likely exceeded the environmental self purification capacity thereby enhancing the biomass and changing the phytoplankton community structure therefore sgd processes with derived nutrients may affect the biogeochemical cycles and marine ecological environment in the maowei sea furthermore the n p ratios 67 in oysters are very close to those in the sgd in the maowei sea this coincidence suggests that the high n p ratios in the sgd are likely to be one of the most important sources that support oyster aquaculture which might weaken the burden of water eutrophication in the maowei sea

downstream sedimentary and geomorphic impacts of the three gorges dam on the yangtze river abstract although large dams have been constructed and continue to be constructed on many rivers the lack of long term gauging data often makes it difficult to document either reservoir sedimentation or the dams downstream impacts more than 50 years of water and sediment data from 20 gauging stations within the yangtze river s basin provide us a unique opportunity to delineate the impacts from the three gorges dam tgd the world s largest dam during the first decade after tgd completion in 2003 1 8 gt of sediments were trapped in the three gorges reservoir tgr the tgr s sediment retention rate increased from 65 during the first three years of operation to 85 by 2008 2012 when the tgd was in normal operation in the low discharge drought years of 2006 and 2011 reservoir retention exceeded 90 sedimentation in the tgr has been discontinuous the most prominent depocenters being at the broad section near the up river entrance to the reservoir and just upstream of the dam where sediment thickness locally exceeds 60 m median size of the sediments trapped in the tgr is 11 m whereas sediments discharged from the tgr are finer than 5 m as a result of sediment retention in the tgr the river downstream has been eroded at a rate of 65 mt yr riverbed sediments have coarsened considerably in the first several hundred kilometers downstream of tgd sediment discharge into the yangtze estuary as measured at the datong downstream gauging station decreased by 130 mt yr relative to the normal water years of 2001 2002 nearly 90 of which can be attributed to the tgd with planned construction of large upstream cascade reservoirs the amount of sediment entering the tgr will decline dramatically thus reducing sedimentation in the tgr and thereby extending its lifespan by the end of the 21st century the tgr should have retained more than 80 of its original storage capacity sediment outflow from the tgr will likely be less than 15 mt yr compared to 50 mt yr at present even with downstream channel erosion the long term average sediment discharge into the yangtze estuary in future decades most likely will decrease to ca 110 mt yr only 20 of its level in the 1960s and further delta erosion is expected

米国 西部内陸 上部白亜系niobrara層のサイクロ層序学 コニアシアン サントニアン軌道時間尺度

astronomical dating in the 19th century abstract today astronomical tuning is widely accepted as numerical dating method after having revolutionised the age calibration of the geological archive and time scale over the last decades however its origin is not well known and tracing its roots is important especially from a science historic perspective astronomical tuning developed in consequence of the astronomical theory of the ice ages and was repeatedly used in the second half of the 19th century before the invention of radio isotopic dating building upon earlier ideas of joseph adhemar james croll started to formulate his astronomical theory of the ice ages in 1864 according to which precession controlled ice ages occur alternatingly on both hemispheres at times of maximum eccentricity of the earth s orbit the publication of these ideas compelled charles lyell to revise his principles of geology and add croll s theory thus providing an alternative to his own geographical cause of the ice ages both croll and lyell initially tuned the last glacial epoch to the prominent eccentricity maximum 850 000 yr ago this age was used as starting point by lyell to calculate an age of 240 million years for the beginning of the cambrium but croll soon revised the tuning to a much younger less prominent eccentricity maximum between 240 000 and 80 000 yr ago in addition he tuned older glacial deposits of late miocene and eocene ages to eccentricity maxima around 800 000 and 2 800 000 yr ago archibald and james geikie were the first to recognize interglacials during the last glacial epoch as predicted by croll s theory and attempted to tune them to precession soon after frank taylor linked a series of 15 end moraines left behind by the retreating ice sheet to precession to arrive at a possible age of 300 000 yr for the maximum glaciation in a classic paper axel blytt 1876 explained the scattered distribution of plant groups in norway to precession induced alternating rainy and dry periods as recorded by the layering in holocene peat bogs he specifically linked the exceptionally wet atlantic period to the prolonged precession minimum at 33 300 yr ago and further related basic stratigraphic alternations to precession induced climate change in general such a linkage was also proposed by grove karl gilbert for cyclic alternations in the marine cretaceous of north america extrapolating sedimentation rates he arrived at an astronomical duration for part of the cretaceous that was roughly as long as the final estimate of william thomson for the age of the earth assuming that orbital parameters directly affect sea level karl mayer eymar and blytt correlated the well known succession of tertiary stages to precession and eccentricity respectively remarkably blytt like croll before him used very long period cycles in eccentricity to establish and validate his tuning understandably these studies in the second half of the 19th century were largely deductive in nature and proved partly incorrect later nevertheless this fascinating period marks a crucial phase in the development of the astronomical theory of the ice ages and climate and in astronomical dating it preceded the final inductive phase which started with the recovery of deep sea cores in 1947 and led to a spectacular revival of the astronomical theory by a century the first half of the 20th century can best be regarded as an intermediate phase despite the significant progress made in both theoretical aspects and tuning

marine carbon burial flux and the carbon isotope record of late cretaceous coniacian santonian oceanic anoxic event iii abstract episodes of widespread distribution of organic rich marine facies within relatively narrow stratigraphic intervals have been interpreted as oceanic anoxic events oaes there are a number of such intervals in the upper cretaceous some of which also exhibit significant positive excursions in carbon isotope records as a result a general model of the relationship between enhanced organic carbon burial and positive c isotope shifts has emerged carbon isotope stratigraphy has therefore developed the dual utility of a chronostratigraphic tool and a means to help identify and define intervals of exceptional organic matter burial and preservation however variations in regional carbon isotope records of globally documented events suggest that the relationship between organic carbon burial flux and magnitude of carbon isotope excursion may not be entirely straightforward for example strata of coniacian santonian age have long been recognized for enhanced organic content in many areas but the designation of oceanic anoxic event iii for this interval has been rather equivocal in the literature mostly due to the weak positive 13 c excursion 0 5 yet in some areas organic carbon accumulation rates for coniacian santonian strata are roughly double that of the older oae ii which is marked by a 2 4 shift in 13 c interestingly the burial flux of carbonate which leads to depletion rather than enrichment of the c isotope signal is also significantly elevated during coniacian santonian time in this study the role of variations in organic carbon and carbonate accumulation rates on carbon isotopic expression are explored through application of data on the composition accumulation rate and areal distribution of end member facies types to the development of a global carbon isotopic mass balance model the results are used to explore the hypothesis that net organic carbon burial during oae iii was not accurately represented in the carbon isotopic record these results have important implications for interpretation of c isotope records related to past perturbations of the global carbon cycle

organic geochemical characterization of santonian to early campanian organic matter rich marls sondage no 1 cores as related to oae3 from the tarfaya basin morocco abstract in addition to previously analyzed sediments of cenomanian to santonian age in the tarfaya sondage no 2 well this study presents the results of a stratigraphically younger interval of santonian to early campanian age in the adjacent well tarfaya sondage no 1 this interval is part of the oceanic anoxic event 3 oae3 which occurred mainly in the atlantic realm due to known high quality source rocks related to oaes i e cenomanian turonian the investigated sample section was tested for the quality quantity and kind of organic matter om describing also the depositional environment the study was carried out by means of i elemental analysis c org caco 3 ts ii rock eval pyrolysis iii vitrinite reflectance measurements iv gas chromatography flame ionization detection gc fid and v gc mass spectrometry gc ms total content of organic carbon c org values for the hydrogen index hi mainly in the range 500 700 mg g c org and s 2 values 10 40 mg g rock support the assumption of a high petroleum generation potential in these upper cretaceous sediments ts c org ratios as well as pristane phytane ratios indicate variable oxygen contents during sediment deposition representing a typical depositional setting for the late cretaceous and are in good agreement with previously analyzed data in the tarfaya basin phyto and zoo plankton were identified as marine sourced all of the investigated early campanian and santonian samples are immature with some tendencies to early maturation these results are based on vitrinite reflectance 0 3 0 4 vr r t max values 409 425 c production indices pi s 1 s 1 s 2 n alkane ratios i e carbon preference index as the deposition of these sediments is time related to oae3 the depositional environment was characterized by oxygen deficiency or even anoxic bottom water conditions this situation was favored during the cretaceous greenhouse climate by limited oxygen solubility in the then warmer ocean water furthermore local factors related to nutrient supply and primary bioproductivity led to the exceptionally thick upper cretaceous organic matter rich sedimentary sequence of the tarfaya basin

mobile mud dynamics in the east china sea elucidated using 210pb 137cs 7be and 234th as tracers mobile mud mm which has fine grain size distribution 90 clay silt and 2 5 in south inshore indicates that the sediment focusing resulted in the increased mass flux the residence time of mm is estimated as 3 6 years both by mass balance of mm and 210pbex in mm

the morphometric variation of islands in the middle and lower yangtze river a variational analytical explanation abstract anabranching rivers are formed of islands of various shapes and this study applies a variational analytical approach to explain the morphology of islands of a particular basic shape a theoretically modeled anabranching river is developed based on observations from the middle and lower yangtze river which alternates between a single channel and a two channel anabranching reach with islands approximately triangular in planform such that one anabranch is longer than the other the equilibrium condition of the model river is derived from a variational investigation of basic relationships of flow continuity channel boundary resistance bedload transport and energy conservation in the anabranching river we demonstrate that when such a system reaches stationary equilibrium the triangular planform of the island is determined by the proportions of water and sediment passing through the two channels we also show that the shorter straight channel takes a larger proportion of sediment relative to its proportion of water for the island to take a streamlined morphology the difference between the proportions of water and sediment discharge entering each channel needs to be as small as possible when the paired proportions of water and sediment discharge take different values the streamlined morphologies of the island vary in a wide range in comparison with the measured morphologies of the five islands located in the middle lower yangtze river the theoretically determined lengths of the islands are remarkably consistent varying from the corresponding field measurements by a range of

redox controlled preservation of organic matter during oae 3 within the western interior seaway during the cretaceous widespread black shale deposition occurred during a series of oceanic anoxic events oaes multiple processes are known to control the deposition of marine black shales including changes in primary productivity organic matter preservation and dilution oaes offer an opportunity to evaluate the relative roles of these forcing factors the youngest of these events the coniacian to santonian oae 3 resulted in a prolonged organic carbon burial event in shallow and restricted marine environments including the western interior seaway new high resolution isotope organic and trace metal records from the latest turonian to early santonian niobrara formation are used to characterize the amount and composition of organic matter preserved as well as the geochemical conditions under which it accumulated redox sensitive metals mo mn and re indicate a gradual drawdown of oxygen leading into the abrupt onset of organic carbon rich up to 8 deposition high hydrogen indices hi and organic carbon to total nitrogen ratios c n demonstrate that the elemental composition of preserved marine organic matter is distinct under different redox conditions local changes in 13c indicate that redox controlled early diagenesis can also significantly alter 13corg records these results demonstrate that the development of anoxia is of primary importance in triggering the prolonged carbon burial in the niobrara formation sea level reconstructions 18o results and mo total organic carbon ratios suggest that stratification and enhanced bottom water restriction caused the drawdown of bottom water oxygen increased nutrients from benthic regeneration and or continental runoff may have sustained primary productivity

improving sediment load estimations the case of the yarlung zangbo river the upper brahmaputra tibet plateau abstract suspended sediment load of a river represents integrated results of soil erosion landform change and ecosystem variation occurring within the river basin accurate estimation of suspended sediment load is helpful for distinguishing the impact of natural and anthropogenic factors on earth system processes within river basin under global climate change suspended sediment load with long term in situ observation limited by harsh conditions can be estimated by sediment rating curves and various subdivision methods with suspended sediment concentration and discharge data of low frequency new sediment rating curve subdivision methods based on flood ranks and suspended sediment concentration stages were proposed in this study the flood ranks subdivision method which defined a flood to begin when discharge exceeded the critical discharge value rank1 or the previous peak flow rank2 and the later and end when fluctuating discharge reached the peak flow of current flood again which is the beginning of next flood or lowered to the critical discharge value the last rank was suitable for application in the basin where sediments were mainly transported and exhausted in early events the suspended sediment concentration stages subdivision method i e the rising and falling limbs of suspended sediment concentration separated by peak dates estimated based on accumulated precipitation was suitable for application in the basin where soil erosion was closely related to precipitation compared to the traditional sediment rating curve and seasonal discharge classes and discharge stages subdivision methods these newly proposed methods can improve suspended sediment concentration and subsequently suspended sediment load estimation in the middle reach of the yarlung zangbo river with higher coefficients of determination and nash sutcliffe efficiency coefficients and lower bias and root mean square errors moreover combination of the two separately developed methods presented further improved estimation the newly proposed sediment rating curve subdivision methods could be helpful for suspended sediment load estimation and therefore are useful for water resource management within river basins