a global review of sediment source fingerprinting research incorporating fallout radiocesium 137cs abstract information on the main sources supplying deleterious sediment loads to river systems is needed to improve our understanding of soil erosion processes to better target erosion control measures in particular it is important to quantify the respective contributions of surface and subsurface sources to material degrading waterbodies radiocesium 137cs emitted during thermonuclear bomb testing 1950 1980 and nuclear accidents provides significant discrimination between surface material exposed to atmospheric fallout and subsurface material sheltered from it a systematic worldwide review of research articles n 123 that used 137cs to trace sediment sources showed that the united kingdom n 24 australia n 23 and the united states n 20 had the highest number of publications utilizing 137cs in a sediment tracing framework in contrast few studies were published for catchments in africa n 9 or south america n 2 in the northern hemisphere positive relationships were evident between 137cs activities in surface and subsurface sources and the proportion of thermonuclear bomb fallout however given the low proportions of fallout received in regions between 0 and 20 n and 0 20 s the potential application of 137cs tracing techniques may be limited in this area of the world as well as in agricultural regions with severe soil erosion i e chinese loess plateau and south africa in total 94 of the studies researching surface and subsurface sources that analysed 137cs as a potential tracing property included this parameter in end member mixing models the main challenges for the future of this technique are related to the access to ultra low background gamma spectrometry facilities and the development of surrogate tracers future research should ensure that basic catchment information and details on the sampling design are properly documented to ensure studies are reproducible moreover researchers should provide raw measurement data to help improve our global understanding of 137cs dynamics in soil erosion research

palaeoenvironmental reconstruction of a middle miocene alluvial fan to cyclic shallow lacustrine depositional system in the calatayud basin ne spain the middle miocene sedimentary fill of the calatayud basin in north eastern spain consists of proximal to distal alluvial fan floodplain and shallow lacustrine deposits four main facies groups characteristic of differentsedimentary environments are recognized 1 proximal and medial alluvial fan facies that comprise clast supported gravel and subordinate sandstone and mudstone the latter exhibiting incipient pedogenic features 2 distal alluvial fan facies formed mainly of massive mudstone carbonate rich palaeosols and local carbonate pond deposits 3 lake margin facies which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system i e front lithofacies a comprising massive siliciclastic mudstone and tabular carbonates or lateral lithofacies b showing laminated and or massive siliciclastic mudstone alternating with tabular and or laminated carbonate beds and 4 mudflat shallow lake facies showing a remarkable cyclical alternation of green grey and or red siliciclastic mudstone units and white dolomitic carbonate beds the cyclic mudflat shallow lake succession as exposed in the orera composite section ocs is dominantly composed of small scale mudstone carbonate dolomite cycles the mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods the deposits evolving either under subaerial exposure or water saturated conditions depending on their location on the lacustrine mudflat and on climate the dolomite intervals accumulated during lake level highstands with mg rich waters becoming increasingly concentrated lowstand to highstand lake level changes indicated by the mudstone dolomite units of the small scale cycles reflect a climate control from dry to wet conditions on the sedimentation in the area the spatial distribution of the different lithofacies implies that deposition of the small scale cycles took place in a low gradient shallow lake basin located in an interfan zone the development of the basin was constrained by gradual alluvial fan aggradation additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of 1 8 o and 1 3 c values varying from 7 9 to 3 0 pdb and from 9 2 to 1 7 pdb respectively more negative 1 8 d and 1 3 c values are from carbonate rich palaeosols and lake margin carbonates which extended in front of the alluvial fan systems whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment the results show a clear trend of 1 8 o enrichment in the carbonates from lake margin to the centre of the shallow lake basin thereby also demonstrating that the lake evolved under hydrologically closed conditions

climate stability across the eocene oligocene transition southern argentina fossil mammal teeth from mid latitude southern argentina 46 s that closely bracket the eocene oligocene transition show no resolvable change in oxygen isotope compositions in combination with paleofloral observations and geographic considerations this finding implies not only that climate was essentially constant despite interpretations elsewhere for major mid and high latitude cooling but also that evolution of hypsodonty did not coincide with climate change during the eocene oligocene transition one possible explanation for eocene oligocene transition climatic stability is that southern high latitude cooling increased latitudinal temperature gradients and strengthened ocean circulation gyres including the southward flowing brazil current in the western south atlantic regionally increased heat transport in the western atlantic offset global cooling producing a nearly constant temperature in southern south america a more radical interpretation supported by some marine data is that the paradigm of major global cooling at the eocene oligocene transition is largely false in that mean sea surface temperatures changed very little

rapid stepwise onset of antarctic glaciation and deeper calcite compensation in the pacific ocean the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth at present this depth is 4 500 m with some variation between and within ocean basins the calcite compensation depth is linked to ocean acidity which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate1 geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the eocene oligocene boundary 34 million years ago 2 when significant permanent ice sheets first appeared on antarctica3 4 5 6 but the relationship between these two events is poorly understood here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical pacific ocean that cover the eocene oligocene boundary we find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40 000 years each synchronous with the stepwise onset of antarctic ice sheet growth the glaciation was initiated after climatic preconditioning7 by an interval when the earth s orbit of the sun favoured cool summers the changes in oxygen isotope composition across the eocene oligocene boundary are too large to be explained by antarctic ice sheet growth alone and must therefore also indicate contemporaneous global cooling and or northern hemisphere glaciation

identifying sediment sources in a gullied catchment using natural and anthropogenic radioactivity the ratio of the lithogenic nuclides 226ra and 232th indicates that the major source of sediment in transport in a gullied catchment located in the head waters of whiteheads creek new south wales australia is the gully itself this observation is supported by 7be and 137cs concentrations which indicate that the sediment is derived from erosion of either gully floor or gully wall material while subcatchment 7be and 137cs data show sheet rill and gully erosion are occurring in the upstream catchments sediment from these sources is either being trapped before entering the gully or the volume of sediment is small compared to that derived from the gully itself the differences in the 226ra to 232th ratio between the suspended solids collected on the rising stage and samples of sediment deposited during the falling stage at the outlet of the catchment indicate a change in the source of sediment during storm events the results presented here demonstrate the applicability of radionuclide tracers in providing quantitative estimates of the relative contributions of individual catchments to the sediment moving within a drainage network and in determining whether or not the sediments are mainly derived from subsoil or topsoil sources

palaeoenvironment of the eocene eckfeld maar lake germany implications from geochemical analysis of the oil shale sequence abstract drill core samples from the depth interval between 19 4 and 32 0 m of the laminated central lake facies of the eocene eckfeld maar were investigated for biomarker and stable isotope composition bulk organic geochemical parameters c n hi and the molecular composition of the soluble organic matter indicate a dominance of particulate organic matter from land plants and microbially derived lipids in the lower part of the sedimentary succession an angiosperm dominated vegetation is indicated from the terpenoid biomarker composition abundant 4 methylsteroids in the 25 6 30 8 m section of the oil shale sequence reflect a contribution of algal derived biomass samples with high concentrations of methylsteroids are characterized by low amounts of triterpenoids related to the arborane skeleton and vice versa this pattern is interpreted as reflecting differences in autochthonous organic matter production vs microbial activity in the lowermost section 32 0 30 6 m a trend towards heavier 18 o and 13 c values indicates the evolution of permanently meromictic conditions in the lake and an increase in methanogenesis high 13 c values of siderites 10 throughout most of the sequence are consistent with permanently anoxic conditions at the sediment water interface the lighter 18 o values of siderites from turbidites relative to siderites from biogenic laminites are postulated to have been caused by temporary phases of increased precipitation followed by landslides and improved circulation within the lake depletion of the organic matter in 13 c average 13 c 29 4 in comparison with the fossil wood ranging from 23 1 to 26 6 is explained by the dominance of waxy lipid rich land plant material e g leaf waxes resins bark over wood supplied to the lake carbon cycling during anoxic decomposition of organic matter is assumed to further affect the 13 c values through the activity of anaerobic e g methanogenic bacteria resulting in a depletion of the biomass in 13 c the overall trend in the isotopic composition of organic carbon towards heavier values in the depth interval between 26 0 and 3 2 m is accompanied by decreasing c n ratios indicating an increase in aquatic organic matter production the geochemistry of the oil shale succession points towards a highly productive eutrophic ecosystem with intense microbial activity under meromictic conditions in the maar lake beside the high input of land plants to the biomass major contributions from bacteria and phytoplankton are indicated by the biomarker composition

differences between the source contribution of bed material and suspended sediments in a mountainous agricultural catchment of western iran abstract soil erosion is intense in semi arid regions of iran and causes a decline in dam reservoir capacities and losing fertile soils from agricultural areas effective control of sediment delivery to the water storage requires an understanding of the sediment sources to investigate the spatial provenance of suspended and bed material sediments in the taleghani catchment western iran eleven geochemical tracers were used to distinguish sediment sources in total 44 source samples were collected from the surface soil of three land use sources and the sub soil of channel banks together with eight suspended samples in different flood events and eleven bed material samples from different river stream sites were collected two mixing models i e the collins and hughes mixing models were applied to compute the contribution of different sources to both river bed and suspended sediments the results of more accurate mixing model the hughes model based on goodness of fit test indicated that channel derived sediments dominate average 71 5 the sediment sources contributing to bed materials in addition temporal variability of sources when suspended load was applied as the sediment input in mixing models showed that crop fields were the dominant source of sediment in flood events with high sediment concentrations however in flood events with less sediment concentrations channel banks reach to higher apportionment

geochemistry of daihai lake sediments inner mongolia north china implications for provenance sedimentary sorting and catchment weathering abstract to advance the understanding of sediment distribution catchment weathering hydraulic sorting and sediment provenance in a tectonically stable basin the geochemistry of surface sediment samples from daihai lake in north china is presented mud bulk sediments were analyzed for 10 major and 30 trace elements organic carbon and nitrogen and for 87sr 86sr ratios in silicate fraction acid insoluble ai and carbonates acid soluble as enrichment in fe2o3 cao mno mgo k2o and p2o5 and their positive correlation with al2o3 rb sr ratios and bivariate discrimination diagrams of k vs rb and th u vs th suggest low chemical weathering intensity under semiarid conditions in the daihai catchment accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth although similar chondrite normalized ree rare earth element patterns of lake sediment samples with lree light rare earth element enrichment negative eu anomalies and an almost flat hree heavy rare earth element pattern may suggest similar sedimentary source rocks original sediment provenance can be recognized on the basis of their distinctive 87sr 86sr ai ratios and immobile th zr ti and nb trace element signature separating from weathering and sedimentary processes as well as from grain size effect

sediment output and effective discharge in two small high mountain catchments in the bavarian alps germany abstract sediment output solid and dissolved load from two small alpine rivers partnach and lahnenwiesgraben in the bavarian alps was measured during three summer field seasons from 2001 2003 there is high spatial variability of sediment output between the catchments and a high temporal variability between observation periods sediment transport in the partnach river reintal is dominated by solute load whereas the lahnenwiesgraben river transports a much greater proportion of solid load this difference can mainly be explained by the different lithologies of the systems the reintal catchment is dominated by massive triassic limestone in the lahnenwiesgraben catchment in addition to limestones unconsolidated rocks marls and mudstone layers are significant furthermore large rockslide dams in the partnach valley isolate large parts of the reintal catchment from solid load output the components of fluvial sediment transport were where possible calculated by using flow duration curves and rating curve techniques in the lahnenwiesgraben event specific rating curves were used to determine suspended load on the broad database of 55 measured flood events in the lahnenwiesgraben a good correlation r pearson 0 9 between event peak discharge and suspended load of the event was established effective discharge was calculated for the different types of sediment load solid and dissolved and total load in the reintal effective discharge for total load is found in low flow classes close to mean discharge because sediment output is dominated by dissolved load which has its maximum efficiency at low and moderate discharges in the lahnenwiesgraben most work is done by discharges much higher than mean discharge during extreme individual flood events

spatial patterns of sediment dynamics within a medium sized watershed over an extreme storm event abstract in this study we quantified spatial patterns of sediment dynamics in a watershed of 311 km 2 over an extreme storm event using watershed modeling and statistical analyses first we calibrated a watershed model dynamic watershed simulation model dwsm by comparing the predicted with calculated hydrograph and sedigraph at the outlet for this event then we predicted values of event runoff volume v peak flow q peak and two types of event sediment yields for lumped morphological units that contain 42 overland elements and 21 channel segments within the study watershed two overland elements and the connected channel segment form a first order subwatershed several of which constitute a larger nested subwatershed next we examined i the relationships between these variables and area a precipitation p mean slope s soil erodibility factor and percent of crop and pasture lands for all overland elements i e the small spatial scale sss and ii those between sediment yield q peak a p and event runoff depth h for the first order and nested subwatersheds along two main creeks of the study watershed i e the larger spatial scales lss we found that at the sss sediment yield was nonlinearly well related to a and p but not q peak and h whereas at the lss linear relationships between sediment yield and q peak existed so did the q peak a and q peak p relationships this linearity suggests the increased connectivity from the sss to lss which was caused by ignorance of channel processes within overland elements it also implies that sediment was transported at capacity during the extreme event so controlling sediment supply from the most erodible overland elements may not efficiently reduce the downstream sediment load

soil hydraulic properties in a marly gully catchment draix france abstract runoff is one of the main factors controlling gully development concentrated flow erosion occurs where flow discharge and velocity exceed critical values in southern french alps in black marl gully catchments runoff from hillslopes occurs in the form of hortonian overland flow because rainfall intensities exceed the infiltration capacity of the soil in such a situation spatial variability of infiltration capacities is critical for describing the runoff production this study reports detailed field measurements of near saturation and saturated infiltration properties capillary sorptivity s and hydraulic conductivity k a total of 140 infiltration tests were conducted using tension disc and ponded ring infiltrometers on 6 different regoliths weathering profile encountered in a marly gully catchment the main objectives were to improve our knowledge of the spatial variability of infiltration in black marl areas and to compare different field and data analysis methods hydraulic conductivity values k h at supply pressure heads h ranging from h 100 up to h 0 mm were calculated using steady state flow and wooding s equation wooding r a 1968 steady infiltration from shallow circular pond water resour res 4 6 1259 1273 k h 0 mm was also estimated from the ponded ring infiltrometer data set the estimation of sorptivity was based on transient flow and the solution of haverkamp et al haverkamp r roos p j smettem k r j parlange j y 1994 three dimensional analysis of infiltration from the disc infiltrometer 2 physical based infiltration equation water resour res 30 11 2931 2935 three methods were used to analyse tension disc infiltrometer data multiple radii multiple potential and single test only the multiple radii method was found not suitable in our context due to a large spatial variability in the infiltration properties over small distances the other methods gave similar estimates of the hydraulic conductivity the hydraulic conductivity k h ranged up to two orders of magnitude this result confirms the role played by structural voids when the regolith is at near saturation the dispersion of the estimates of field saturated hydraulic conductivity is larger than unsaturated values the spatial differences found are explained by the topographical position and by the regolith structure observed for the 6 sites an analysis based on the ponding time show that the regolith type plays an important role in the dynamic of the runoff production

tracing sediment sources during floods using diffuse reflectance infrared fourier transform spectrometry drifts a case study in a highly erosive mountainous catchment southern french alps summary in mountainous catchments large quantities of sediment are exported within very short periods leading to numerous environmental problems e g reservoir siltation the origin of suspended sediment during two distinct floods was determined by conducting an original fingerprinting method coupling diffuse reflectance infrared fourier transform spectroscopy drifts and a chemometric technique i e partial least squares pls analysis samples of the potential sediment sources were collected in badland areas developed on various substrates i e molasse marly limestones black marls and gypsum in the galabre 20 km 2 catchment located in the french southern alps drifts spectra provided a way to discriminate between the different potential sediment sources furthermore the use of mid infrared spectra allowed the direct quantification of the gypsum proportion in sediment this contribution was systematically null at the catchment outlet because of the rapid dissolution of gypsum in the river a pls model was then constructed to estimate the contribution of the three other potential sources to the sediment flux during the floods this model was developed and validated using a set of 45 experimental samples that were prepared in the laboratory in order to contain various proportions of the three remaining sources by introducing drifts spectra into the pls model we could predict the proportions of those sources in the mixed experimental samples with a confidence interval of ca 10 the model was then applied to the sediment collected during the two selected floods in order to outline their origin black marls provided the highest contribution of sediment during both events but the analysis also revealed a significant contribution of molasse results also showed the remobilisation of sediment originated from molassic substrates that deposited on the riverbed during a preceding event opportunities for improvement and further use of this method as an alternative or rapid complementary sediment fingerprinting technique are finally discussed

sediment source changes over the last 250 years in a dry tropical catchment central queensland australia abstract rivers draining to the great barrier reef are receiving increased attention with the realisation that european land use changes over the last 150 years may have increased river sediment yields and that these may have adversely affected the reef environment mitigation of the effects associated with such changes is only possible if information on the spatial provenance and dominant types of erosion is known to date very few field based studies have attempted to provide this information this study uses fallout radionuclide 137cs and 210pbex and geochemical tracing of river bed and floodplain sediments to examine sources over the last 250 years for theresa creek a subcatchment of the fitzroy river basin central queensland australia a monte carlo style mixing model is used to predict the relative contribution of both the spatial geological sources and erosion types the results indicate that sheetwash and rill erosion from cultivated basaltic land and channel erosion from non basaltic parts of the catchment are currently contributing most sediment to the river system evidence indicates that the dominant form of channel erosion is gully headcut and sidewall erosion sheetwash and rill erosion from uncultivated land i e grazed pasture woodland is a comparatively minor contributor of sediment to the river network analysis of the spatial provenance of floodplain core sediments in conjunction with optical dating and 137cs depth profile data suggests that a phase of channel erosion was initiated in the late nineteenth century with the development of land underlain by basalt in the mid twentieth century the dominant source of erosion shifted to cultivated land although improvements in land management practices have probably resulted in a decrease in sediment yield from cultivated areas in the later half of the twentieth century on a basin wide scale because of the limited spatial extent of cultivation channel sources are likely to be the largest contributor of sediment to the fitzroy river accordingly catchment management measures focused on reducing sediment delivery to the great barrier reef should focus primarily on decreasing erosion from channel sources

suspended sediment transport in a highly erodible catchment the river isabena southern pyrenees abstract understanding and quantifying sediment load is important in catchments draining highly erodible materials that eventually contribute to siltation of downstream reservoirs within this context the suspended sediment transport and its temporal dynamics have been studied in the river isabena 445 km 2 south central pyrenees ebro basin by means of direct sampling and turbidity recording during a 3 year dry period the average flood suspended sediment concentration was 8 g l 1 with maximum instantaneous values above 350 g l 1 the high scatter between discharge and suspended sediment concentrations up to five orders of magnitude has not permitted the use of rating curve methods to estimate the total load interpolation techniques yielded a mean annual sediment load of 184 253 t y 1 for the study period with a specific yield of 414 t km 2 y 1 this value resembles those reported for small torrents in nearby mountainous environments and is the result of the high connectivity between the badland source areas and stream courses a fact that maximises sediment conveyance through the catchment floods dominated the sediment transport and yield however sediment transport was more constant through time than that observed in mediterranean counterparts this can be attributed to the role of base flows that entrain fine sediment temporarily stored in the channel and force the river to carry high sediment concentrations i e generally in the order of 0 5 g l 1 even under minimum flow conditions

eocene circulation of the southern ocean was antarctica kept warm by subtropical waters 1 near the eocene s close 34 million years ago the climate system underwent one of the largest shifts in earth s history antarctic terrestrial ice sheets suddenly grew and ocean productivity patterns changed previous studies conjectured that poleward penetration of warm subtropical currents the east australian current eac in particular caused eocene antarctic warmth late eocene opening of an ocean gateway between australia and antarctica was conjectured to have disrupted the eac cooled antarctica and allowed ice sheets to develop here we reconstruct eocene paleoceanographic circulation in the tasmanian region using 1 biogeographical distributions of phytoplankton including data from recently drilled ocean drilling program leg 189 sites and 2 fully coupled climate model simulations we find that the eac did not penetrate to high latitudes and ocean heat transport in the region was not greater than modern our results do not support changes in thermal isolation as the primary driver of the eocene oligocene climatic transition

cooler winters as a possible cause of mass extinctions at the eocene oligocene boundary the eocene oligocene boundary at about 33 7 myr ago marks one of the largest extinctions of marine invertebrates in the cenozoic period1 for example turnover of mollusc species in the us gulf coastal plain was over 90 at this time2 3 a temperature change across this boundary from warm eocene climates to cooler conditions in the oligocene has been suggested as a cause of this extinction event4 but climate reconstructions have not provided support for this hypothesis here we report stable oxygen isotope measurements of aragonite in fish otoliths ear stones collected across the eocene oligocene boundary palaeotemperatures reconstructed from mean otolith oxygen isotope values show little change through this interval in agreement with previous studies5 6 from incremental microsampling of otoliths however we can resolve the seasonal variation in temperature recorded as the otoliths continue to accrete new material over the life of the fish these seasonal data suggest that winters became about 4 c colder across the eocene oligocene boundary we suggest that temperature variability rather than change in mean annual temperature helped to cause faunal turnover during this transition

faunal turnovers of palaeogene mammals from the mongolian plateau most orders and many families of modern mammals were established during the palaeogene mammalian evolution during this period of time has been correlated with global climatic events1 2 3 4 although the timing mode and scale of such a climate evolution link remain debatable1 5 6 the palaeogene global climate was step punctuated by a warming across the palaeocene eocene boundary about 55 myr ago and a cool off throughout the late eocene and early oligocene epochs1 2 7 8 9 10 the most severe cooling was at 33 5 myr slightly after the eocene oligocene boundary and was characterized by a drop in the mean annual temperature and by changes in vegetation from eocene dense forests to oligocene more open country5 here we analyse 33 palaeogene mammal faunas from the mongolian plateau of china and mongolia there is a distinct pattern of faunal turnovers perissodactyl dominant faunas of the eocene were abruptly replaced by rodent lagomorph dominant faunas of the oligocene we interpret the turnovers as having been effected by global climatic shifts and name the prominent biotic reorganization across the eocene oligocene boundary the mongolian remodelling which correlates to the european grande coupure

assessment of different colour parameters for discriminating potential suspended sediment sources and provenance a multi scale study in luxembourg abstract sediment colour has recently been used successfully to estimate suspended sediment sources in small catchments using the fingerprinting approach the methodology offers opportunity for further research since it provides a rapid and cheap means for investigating sediment sources however the colour based fingerprinting approach has not yet been tested in medium and large catchments this paper aims to test whether colour parameters are capable of discriminating sediment sources in a nested system of seven sub catchments ranging from 0 7 to 247 km 2 of the attert river catchment nw luxembourg time integrated suspended sediment samples and samples of potential sediment sources land use types and channel banks were collected in all catchments sediment colour was then computed from diffuse reflectance spectrometry measurements asd fieldspec ii spectrometer 0 4 2 5 m taken over the visible wavelength range twenty four colour parameters were derived from several colour space models cie xyy cie xyz rgb munsell hvc helmholtz chromaticity cieluv and cielab and their ability to discriminate potential suspended sediment sources and provenance was evaluated and compared results demonstrated that time integrated suspended sediment samples collected in the study catchments had statistically different colour values moreover these values always represented a mixture of the colour values measured on potential suspended sediment sources in the catchment inter source colour contrasts land use types and channel banks were observed in all catchments kruskal wallis h test however although colour is able to distinguish potential sediment sources in small catchments the level of source discrimination decreases as the catchment size increases probably due to heterogeneous geology and pedology intra source variability and to source overlap nevertheless in the studied medium sized catchments ranging from 19 4 to 247 km 2 colour could differentiate between topsoil and sub surface i e channel bank material and or up to three sources types no single colour model had discrimination power across catchments instead in each catchment a different combination of colour parameters gathered from different colour space models produced optimal discrimination of potential sediment sources furthermore a colour based fingerprinting approach did not possess potential for integrating spatial provenance and source type information because colour parameters could not discriminate between contrasting geological sub areas in summary although colour parameters were not capable of discriminating the range of land use type and channel banks as potential suspended sediment sources in medium sized catchments they afford substantial information and could be integrated into the classical fingerprinting approach together with other constituents e g geochemistry radionuclides and or organic compounds

reduced sediment supply in a fast eroding landscape a multi proxy sediment budget of the upper rhone basin central alps alpine water and sediment supply influence the sediment budget of many important european fluvial systems such as the rhine rhone and po rivers in the light of human induced climate change and landscape modification it becomes increasingly important to understand the mechanisms of sediment production and supply in alpine sediment systems this study aims to investigate the modern sediment budget of the upper rhone basin one of the largest alpine intramontane watersheds located in the central alps of southwestern switzerland major areas of sediment generation are fingerprinted by framework petrography heavy mineral concentrations and bulk geochemistry the relative contributions of the three major sources to the sediment of the trunk rhone river are identified by compositional mixing modelling concentrations of the terrestrial cosmogenic nuclide 10be measured in quartz separated from fluvial sediments provide spatially averaged denudation rates for selected tributary basins results from sediment fingerprinting and mixing modelling suggest that tributaries located in the north and the east of the catchment are generating most of the sediment transported by the rhone river to its primary sedimentary sink in lake geneva despite having some of the highest denudation rates within the basin tributaries located in the southern area of the rhone basin are relatively underrepresented in the sediment budget of the rhone river these tributaries are severely affected by human activities for example through sediment mining as well as water and sediment abstraction in large hydropower reservoirs together these processes reduce the basin wide sediment discharge by about 50 thereby explaining most of the observed compositional pattern in addition there is evidence suggesting that large amounts of glaciogenic sediments are currently supplied by retreating glaciers glaciogenic material with its low 10be concentrations can lead to a significant overestimation of denudation rates and thus limit the applicability of cosmogenic nuclide analysis in such glaciated settings

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

relationships between suspended sediment concentrations and discharge in two small research basins in a mountainous mediterranean area vallcebre eastern pyrenees abstract the relationships between suspended sediment concentrations and discharge were studied at the can vila 0 56 km2 and ca l isard 1 32 km2 sub basins of the vallcebre research area eastern pyrenees during a period of 5 years that included 67 events of diverse magnitude abandoned agricultural fields and forests are the main land use in the can vila basin whereas the ca l isard basin is mainly forested though there are also some heavily eroded landscapes badlands the most frequent events were of a single discharge peak although double and multiple peaked events were also recorded clockwise positive hysteretic loops occurred in both catchments mainly during the wet seasons when precipitation was of moderate intensity average of 18 mm h 1 and baseflow before the event was rather high average for ca l isard 8 1 l s 1 km 2 and for can vila 11 76 l s 1 km 2 the bulk of stream discharge came from saturated areas whereas sediments came mainly from the stream channels counter clockwise negative hysteretic loops were much more frequent in the ca l isard basin mainly in summer when rainfall intensity was high average of 32 5 mm h 1 and baseflow was low average for ca l isard 0 94 l s 1 km 2 and for can vila 0 73 l s 1 km 2 most of the water and sediment came from the badlands eight shaped loops occurred in transition periods mainly in the ca l isard basin

magnetostratigraphy of cenozoic sediments from the xining basin tectonic implications for the northeastern tibetan plateau 1 the xining subbasin of the longzhong basin holds the longest continuous cenozoic stratigraphic record at the margin of the northeastern tibetan plateau despite a rich biostratigraphic content including the xiejia mammal fauna the tectonic evolution of the basin is largely unconstrained in this study we present stratigraphic biostratigraphic and magnetostratigraphic results that provide a basis for reconstructing the cenozoic tectonic evolution of the xining basin with respect to adjacent regions of the northeastern tibetan plateau magnetostratigraphic analysis from three red bed sections in the xining basin indicates continuous deposition at low and nearly constant accumulation rates average 2 2 cm kyr from 52 0 to 17 0 ma we interpret this result to indicate that no major regional tectonic event implying large sediment accumulation variations has affected the xining basin deposition during this considerable time window in detail accumulation rate variations outline a three stage evolution with 1 8 cm kyr from 52 0 ma to 34 5 ma 4 1 cm kyr from 34 5 to 31 0 ma and 2 3 cm kyr from 31 0 to 17 0 ma the second order increase between 34 5 and 31 0 ma can be interpreted to result from either a distal tectonic event or to be of climatic origin although the region was tectonically quiescent for much of the cenozoic tectonic activity occurred during basin initiation or reactivation at circa 55 0 52 5 ma and during intense basin deformation after 17 0 ma

determining the sources of suspended sediment in a forested catchment in southeastern australia 1 knowledge is scarce regarding the relative contributions from harvested areas and unsealed roads to sediments in forested catchments we investigate the source composition of suspended sediment using sediment tracers and an improved multivariate mixing model sediment samples were collected during six rainfall events geochemical and radiometric tracer properties were corrected for particle size and organic content as well as conservativeness during erosion and sediment delivery the mixing model incorporates variability of the tracer properties using a monte carlo simulation technique mean sediment contribution from the undisturbed forest was 50 70 harvested areas gravel surfaced roads and ungravelled roads contributed 5 15 6 14 and 12 25 respectively the unsealed roads contribute 20 to 60 times more sediment than the undisturbed forest and about 10 times more sediment than the harvested areas on a per unit area basis harvested areas contribute 1 to 5 times greater sediment than the undisturbed forest these results support other studies that identify unsealed roads as important sediment sources in forested catchments

indian ocean high productivity event 10 8 ma linked to global cooling or to the initiation of the indian monsoons uplift of the himalayas and tibetan plateau ca 10 8 ma has been said to be the main cause of the origin or intensification of the indian monsoon system because mountains modulate the land sea thermal contrast the intensification of the monsoons in turn is seen as the cause of major changes in fauna and flora on land as a result of changing precipitation patterns as well as in the indian ocean where the monsoons drive increased upwelling and thus increased productivity we argue that the interactions between the elevation of the himalayas and tibetan plateau the onset of the monsoons and their effects on the indian ocean biota remain uncertain the timing of these events uplift monsoons and biotic change is not well constrained neogene deep sea benthic foraminiferal faunal and isotope records of the ninetyeast ridge combined with published data show that a major increase in bio genic productivity occurred at 10 8 ma throughout the indian ocean the equatorial pacific and southern atlantic we suggest that this indian ocean high productivity event was not simply the result of monsoon induced upwelling or nutrient delivery from the weathering of newly uplifted mountains but may have been caused by strengthened wind regimes resulting from global cooling and the increase in volume of the antarctic ice sheets

temporal variability of suspended sediment sources in an alpine catchment combining river rainfall monitoring and sediment fingerprinting influence of the rainfall regime on erosion and transfer of suspended sediment in a 905 km 2 mountainous catchment of the southern french alps was investigated by combining sediment monitoring rainfall data and sediment fingerprinting based on geochemistry and radionuclide concentrations suspended sediment yields were monitored between october 2007 and december 2009 in four subcatchments 22 713 km 2 automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment sediment exports at the river catchment outlet 330 pm 100 t km 2 yr 1 were mainly driven 80 by widespread rainfall events long duration low intensities in contrast heavy local and short duration storms generated high peak discharges and suspended sediment concentrations in small upstream torrents however these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river this study also confirmed the important contribution of black marls up to 70 to sediment transported in rivers although this substrate only occupies c 10 of the total catchment surface sediment exports generated by local convective storms varied significantly at both intra and inter flood scales because of spatial heterogeneity of rainfall however black marls marly limestones contribution remained systematically high in contrast widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones marls quaternary deposits and conglomerates which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment

a quick and low cost technique to identify layers associated with heavy rainfall in sediment archives during the anthropocene long term records are needed to investigate the impact of extreme events inthe current framework of global change sedimentary reconstruction with ahigh resolution remains difficult without conducting expensive destructiveand or time consuming analyses in this study high resolution ct scan profiles 0 6 mm resolution were used to investigate their potential for detecting flood deposits induced by heavy rainfall events this method was applied to a sediment core dated with fallout radionuclides covering 120 year period collected in a pond draining a small forested catchment french massif central central france between 1960 and 2017 28 layers were deposited seventy six percent of these deposits were correlated to the occurrence of heavy rainfall 50 mm recorded during one or two consecutive days the remainder of the deposits detected with the computer tomo graphy ct scanner n 5 were not correlated to weather events they mainly occurred in response to landscape management operations for example afforestation works as a result of the major 1999 storm this period was indeed characterized by an increase in the delivery of137cs enriched sediment demonstrating a greater topsoil contribution to sediment during majorforest management operations the intensity of detrital layers has significantly decreased throughout time after a major land use change that tookplace in 1948 and land abandonment the frequency of heavy rainfall anassociated detrital deposits has nevertheless increased by 60 and 75 respectively between the years 1960 and 2017 these results outline the potential of ct scan for reconstructing long term flood deposits associated with heavy precipitation

examining suspended sediment sources and dynamics during flood events in a drained catchment using radiogenic strontium isotope ratios 87sr 86sr soil erosion is recognized as one of the main processes of land degradation in agricultural areas high suspended sediment loads often generated from eroding agricultural landscapes are known to degrade downstream environments accordingly there is a need to identify suspended sediment sources and to investigate their dynamics here soil and sediment strontium isotopic ratios were used to examine suspended sediment sources and dynamics in a lowland drained catchment in france suspended sediment n 14 was collected in stream and at tile drain n 4 outlets during three flood events between december 2013 and february 2014 potential source soils n 28 representative of the carbonate and silicate substrates found in the catchment were sampled and analyzed strontium isotopic ratios 87sr 86sr were measured in different particle size fractions 2 m 63 m and 2 mm soil 87sr 86sr ratios significantly discriminated between source samples classified as carbonate 0 712625 to 0 717815 and silicate 0 719287 to 0 724631 soils 87sr 86sr ratios measured in suspended sediment 0 713660 to 0 720571 reflect variations in source contributions during different hydrological conditions the 87sr 86sr ratios varied in the different fractions of soil samples i e 2 m 63 m and 2 mm and in suspended sediment samples suspended sediment was interpreted as a mixture of two end members with the dominant contribution of the 2 m fraction of soil samples occurring during small scale flood events and the 2 mm fraction during more intense flood events modelling results indicate that carbonate source soil contributions are variable with their highest contributions occurring during the two first flood events compared to the last flood event the results also show that the tile drainage system enhances the connectivity between cultivated hillslopes and the river network providing a preferential pathway for fine 2 m particles this study demonstrates the potential of using strontium isotopic ratios to examine the variations of suspended sediment sources in drained catchments with contrasting carbonate and silicate sources more importantly the results highlight the need to improve the management of sediment exported from tile drains in similar agricultural environments as they were demonstrated to transfer very fine material to the riverine environment

erosion quantification in the small marly experimental catchments of draix alpes de haute provence france calibration of the etc rainfall runoff erosion model abstract erosion rates measured for 15 years in the small ranging from 0 13 ha to nearly 1 km2 and steep 30 75 mountainous marly basins of draix south alps france are over 100 tons ha year in a badland area devoid of vegetation in a similar basin reforested at the end of the 19th century the sediment yield is considerably reduced less than 3 tons ha year the analysis of the sediment yield of these torrents reveals the importance of the erosion processes on slopes at the scale of the elementary gully and the influence of deposition transport and scouring processes as soon as the channel network of the basin is developed these processes were modelled by a hydrosedimentologic model developed by cemagref for flood torrent erosion and called etc etc is an integrated spatialized and global model working at the event scale the rainfall runoff component and the solid transport component which involves scouring deposition and armouring are well developed on the other hand the erosion component is not yet a physically based model as the knowledge on the elementary processes is not enough quantitative the etc model was used on a badland basin of 86 ha in area the laval and has shown its ability to simulate both water and sediment flows in mountainous and steep basins the erosion modelling highlighted the need for a better representation of the slope processes and for more information on the storing of sediments in the channel network observations carried out on the influence of the vegetation cover patterns and the links between slopes and channels should be taken into account to improve the model

the geochemical evolution of syncollisional magmatism and the implications for significant magmatic hydrothermal lead zinc mineralization gangdese tibet abstract in addition to well known subduction processes the collision of two continents also generates abundant ore deposits as in the case of the tibetan plateau which is the youngest and most spectacular collisional belt on earth during the building history of the gangdese magmatic belt several magmatic flare up events developed however significant magmatic hydrothermal lead zinc mineralization dominantly accompanied the magmatism during the syncollisional period 65 41 ma based on integrated geochemical and isotopic data we provide insights into the genesis and evolution of syncollisional magmas and their implications for significant magmatic hydrothermal lead zinc mineralization the sr nd isotopic compositions of most syncollisional igneous rocks 87sr 86sr 0 7034 0 7123 end t 9 0 to 1 8 indicate a mixing origin between mantle derived basaltic magmas and ancient crustal melts and fractional crystallization is a fundamental mechanism by which syncollisional magmas evolve towards intermediate to silicic compositions most lead zinc mineralization related plutons are high silica 76 14 wt sio2 on average high oxygen fugacity average fmq 2 5 granites with highly evolved chemical signatures average eun eun 0 33 high rb sr average 3 9 and they represent the final products from primary magmas due to the contribution of ancient crustal melts to the genesis of mineralization related parent magmas the spatial distribution of pb zn deposits within the northern gangdese magmatic belt is controlled by the lithospheric architecture in compressional environments magmas have low evacuation efficiency and long magma chamber lifespan which is favorable for basaltic parents evolved to high silica granites through sufficient fractional crystallization this scenario contributes to our understanding of the significant magmatic hydrothermal lead zinc mineralization that occurred in the syncollisional period

tracing sediment sources in a tropical highland catchment of central mexico by using conventional and alternative fingerprinting methods land degradation is intense in tropical regions where it causes for instance a decline in soil fertility and reservoir siltation two fingerprinting approaches i e the conventional approach based on radionuclide and geochemical concentrations and the alternative diffuse reflectance infrared fourier transform spectroscopy method were conducted independently to outline the sources delivering sediment to the river network draining into the cointzio reservoir in mexican tropical highlands this study was conducted between may and october in 2009 in subcatchments representative of the different environments supplying sediment to the river network overall cointzio catchment is characterized by very altered soils and the dominance of andisols and acrisols both fingerprinting methods provided very similar results regarding the origin of sediment in huertitas subcatchment dominated by acrisols where the bulk of sediment was supplied by gullies in contrast in la cortina subcatchment dominated by andisols the bulk of sediment was supplied by cropland sediment originating from potrerillos subcatchment characterized by a mix of acrisols and andisols was supplied in variable proportions by both gullies and rangeland cropland in this latter subcatchment results provided by both fingerprinting methods were very variable our results outline the need to take the organic carbon content of soils into account and the difficulty to use geochemical properties to fingerprint sediment in very altered volcanic catchments however combining our fingerprinting results with sediment export data provided a way of prioritizing the implementation of erosion control measures to mitigate sediment supply to the cointzio reservoir supplying drinking water to morelia city copyright 2012 john wiley sons ltd

assessment of intermediate fine sediment storage in a braided river reach southern french prealps this paper presents a field investigation on river channel storage of fine sediments in an unglaciated braided river the bes river located in a mountainous region in the southern french prealps braided rivers transport a very large quantity of bedload and suspended sediment load because they are generally located in the vicinity of highly erosive hillslopes consequently these rivers play an important role because they supply and control the sediment load of the entire downstream fluvial network field measurements and aerial photograph analyses were considered together to evaluate the variability of fine sediment quantity stored in a 2 5 km long river reach this study found very large quantities of fine sediment stored in this reach 1100 t per unit depth 1 dm given that this reach accounts for 17 of the braided channel surface area of the river basin the quantities of fine sediment stored in the river network were found to be approximately 80 of the mean annual suspended sediment yields ssys 66 200 t year 1 comparable to the ssys at the flood event scale from 1000 t to 12 000 t depending on the flood event magnitude these results could explain the clockwise hysteretic relationships between suspended sediment concentrations and discharges for 80 of floods this pattern is associated with the rapid availability of the fine sediments stored in the river channel this study shows the need to focus on not only the mechanisms of fine sediment production from hillslope erosion but also the spatiotemporal dynamics of fine sediment transfer in braided rivers copyright 2010 john wiley sons ltd

suspended sediment and 137cs fluxes during the exceptional december 2003 flood in the rhone river southeast france abstract at the beginning of december 2003 one of the biggest floods for at least 150 yr was recorded on the rhone river in the lower part of the river the peak flood reached 11 000 m 3 s 1 the geomorphological and radioecological consequences of such an event were investigated downstream all the nuclear installations by using measured and calculated fluxes and the total export of suspended sediment and associated 137 cs results pointed out the major role played by large floods in the annual suspended sediment load as 3 70 10 6 tons of silts 0 85 10 6 tons of sands and 0 84 10 6 tons of clays were transferred towards the coastal environment nevertheless these solid loads were found to be lower than those expected as regards the liquid discharge reached during this event and suggested that previous floods that occurred on the river and on its main tributaries during the last decade have probably led to the removal of available sediment from the channels and their banks besides the 137 cs activity measured within the suspended load was estimated at 14 9 0 4 bq kg 1 which is a level characteristic of the suspended sediments from the rhone catchment area and demonstrated that nuclear installations located along the rhone valley did not significantly contribute to any increase in 137 cs activity in the water during the flood the total 137 cs particulate export amounted to 77 17 gbq and was mainly associated with the silt fraction that contributes to around 70 of the total 137 cs export

late cenozoic increase in accumulation rates of terrestrial sediment how might climate change have affected erosion rates abstract accumulation rates of terrestrial sediment have increased in the past few million years both on and adjacent to continents although not everywhere apparently erosion has increased in elevated terrain regardless of when last tectonically active or what the present day climate in many regions sediment coarsened abruptly in late pliocene time sparser data suggest increased sedimentation rates at 15 ma approximately when oxygen isotopes in benthic foraminifera imply high latitude cooling if climate change effected accelerated erosion understanding how it did so remains the challenge some obvious candidates such as lowered sea level leading to erosion of continental shelves or increased glaciation account for increased sedimentation in some but not all areas perhaps stable climates that varied slowly allowed geomorphic processes to maintain a state of equilibrium with little erosion until 3 4 ma when large oscillations in climate with periods of 20 000 40 000 years developed and de

floodplains as a source of fine sediment in grazed landscapes tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape abstract the flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers despite this importance the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood this study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in illinois sediment source samples were collected from five sources croplands forested floodplains grasslands upper grazed floodplains and lower grazed floodplains event based and aggregated suspended sediment samples were collected from the stream at the watershed outlet quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from the five sources to the suspended sediment loads to account for possible effects of small sample sizes the analysis was repeated with only two sources grazed floodplains and croplands grasslands forested floodplains results based on mean values of tracers indicate that the vast majority of suspended sediment within the stream 95 is derived from erosion of channel banks and the soil surface within areas of grazed floodplains uncertainty analysis based on monte carlo simulations indicates that mean values of tracer properties which do not account for sampling variability in these properties probably overestimate contributions from the two major sources nevertheless this analysis still supports the conclusion that floodplain erosion accounts for the largest percentage of instream sediment 55 75 although grazing occurs over only a small portion of the total watershed area grazed floodplains which lie in close proximity to the stream channel are an important source of sediment in this headwater steam system efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on eroding floodplain surfaces and channel banks within heavily grazed reaches of the stream

discriminating fine sediment sources and the application of sediment tracers in burned catchments a review wildfire can cause substantial changes to runoff erosion and downstream sediment delivery processes in response to these disturbance effects the main sources of sediment transported within burned catchments may also change sediment tracing offers an approach to determine the proportional contributions of fine sediment typically 63 m from burned catchment sources in this paper we review the application of various sediment tracers to discriminate fine sediment sources following wildfire fallout radionuclides provide the most effective tracers for discriminating hillslope surface and sub surface usually channel bank sources previous tracer studies quantifying contributions from these sources after wildfire are based exclusively on radionuclides the potential for fallout radionuclides to discriminate spatial sources defined according to burned and unburned areas depends on burn related changes in surface soil concentrations tracing of burned and unburned source areas will be problematic where most radionuclides in surface material are bound to ash rather than soil geochemical properties of surface soils are probably too susceptible to natural and burn related variability to consistently discriminate burn defined spatial sources mineral magnetic properties have shown potential for discriminating soil burned at different severities as well as unburned areas more research is needed to assess the use of soil organic compounds as tracers of burned source areas linking fallout radionuclide based hillslope and channel source discrimination with process measurements and monitoring after fire can provide enhanced insight into fine sediment transfer and related water quality impacts adopting such integrated and multi scale approaches would contribute to improved understanding of hydrological and geomorphological responses to wildfire copyright 2012 john wiley sons ltd

interactions of phosphorus with sediments in the river swale yorkshire uk the ultimate fate of inorganic phosphorus in natural waters is to a large degree determined by interactions with sediments the interactions in river bed sediments have been investigated by a combination of methods using surface sediments 2 mm in diameter collected from a 55 km stretch of the river swale in yorkshire uk the sediments were analysed by digestion fe ca and p clay mineralogy and their equilibrium phosphate concentration all the equilibrium phosphate concentrations were below 2 mol dm 3 which is much less than the concentration in the overlying water and indicates a net uptake of phosphorus by the sediments experiments in a fluvarium channel with a coarse sediment also showed that the release and uptake of soluble phosphorus was towards a steady state concentration in the overlying solution consistent with measurements of the equilibrium phosphate concentration a kinetic model describing the net uptake of soluble reactive phosphorus by river sediments was applied to chemical data collected during an intensive monitoring exercise in the catchment copyright 1999 john wiley sons ltd

sediment fingerprinting in agricultural catchments a critical re examination of source discrimination and data corrections fine sediment source fingerprinting techniques have been widely applied in agricultural river catchments successful source discrimination in agricultural environments depends on the key assumption that land use source signatures imprinted on catchment soils are decipherable from those due to other landscape factors affecting soil and sediment properties in this study we re examine this critical assumption by investigating i the physical and chemical basis for source discrimination and ii potential factors that may confound source un mixing in agricultural catchments including particle size and organic matter effects on tracer properties the study is situated in the river tamar a predominantly agricultural catchment 920 km2 in south west england that has also been affected by mining source discrimination focused on pasture and cultivated land uses and channel banks monthly time integrated suspended sediment samples were collected across seven catchments for a 12 month period physical and chemical properties measured in source soils and sediment included fallout radionuclides 137cs excess 210pb major and minor element geochemical constituents total organic carbon and particle size source discrimination was entirely dependent on differences in tracer property concentrations between surface and sub surface soils this is based on fallout radionuclide concentrations that are surface elevated while many geochemical properties are surface depleted due to weathering and pedogenetic effects although surface soil contamination can reverse this trend however source discrimination in the study catchments was limited by i rotation of cultivated and pasture fields resulting in reduced differences between these two sources and ii the cultivated source signature resembling a mix of the pasture and channel bank sources for many tracer properties furthermore a combination of metal pollution from abandoned historic mines and organic enrichment of sediment from upland areas of peaty soils resulted in the non conservative behaviour of some tracer properties in several catchments differences in the particle size and organic carbon content of source soils could explain much of the variation in these properties in downstream sediment rather than selective transport effects inconsistent relationships between particle size organic carbon and tracer property concentrations further undermined the basis for the use of widely applied corrections to tracer datasets sensitivity analysis showed that correcting source tracer data for differences in organic matter can produce large changes to source contribution estimates that cannot be justified and such corrections should not be used confounding factors related to poor source discrimination and non conservative behaviour are highly likely to affect sediment fingerprinting studies in many agricultural catchments as a result estimates of source contributions in many fingerprinting studies may contain significant unquantified errors

hydrogeologic processes in saline systems playas sabkhas and saline lakes abstract pans playas sabkhas salinas saline lakes and salt flats are hydrologically similar varying only in their boundary conditions thus in evaluating geochemical processes in these systems a generic water and solute mass balance approach can be utilized a conceptual model of a coastal sabkha near the arabian gulf is used as an example to illustrate the various water and solute fluxes analysis of this model suggests that upward flux of ground water from underlying formations could be a major source of solutes in the sabkha but contribute only a small volume of the water local rainfall is the main source of water in the modeled sabkha system with a surprisingly large recharge to rainfall ratio of more than 50 the contribution of seawater to the solute budget depends on the ratio of the width of the supratidal zone to the total width and is generally confined to a narrow zone near the shoreline of a typical coastal sabkha because of a short residence time of water steady state flow is expected within a short time 50 000 years the solute composition of the brine in a closed saline system depends largely on the original composition of the input water the high total ion content in the brine limits the efficiency of water rock interaction and absorption because most natural systems are hydrologically open the chemistry of the brines and the associated evaporite deposits may be significantly different than that predicted for hydrologically closed systems seasonal changes in temperature of the unsaturated zone cause precipitation of minerals in saline systems undergoing evaporation thus during the hot dry season months minerals exhibit retrograde solubility so that gypsum anhydrite and calcite precipitate evaporation near the surface is also a major process that causes mineral precipitation in the upper portion of the unsaturated zone e g halite and carnallite provided that the relative humidity of the atmosphere is less than the activity of water the slope of the fresh brine water interface in saline lake systems is shallower than in fresh seawater interface because of the greater density difference between the fresh brine water bodies the interface between sabkha brines and seawater slopes seaward unlike normal marine fresh water systems that slope landward moreover the brine seawater interface does not achieve steady state because it is pushed toward the sea by the sabkha s brine

shallow lacustrine carbonate microfacies document orbitally paced lake level history in the miocene teruel basin north east spain results are presented of a detailed carbonate petrographic study of an upper miocene lacustrine mixed carbonate siliciclastic succession in the teruel basin spain with the aim of constraining lake level variability at different stratigraphic scales regular alternations of red to green mudstone and lacustrine limestone termed the basic cycle reflect lake level variations at the metre scale in an earlier study the basic cycle was shown to be controlled by the climatic precession cycle petrographic analysis made it possible to distinguish two main carbonate microfacies groups characteristic of very shallow transient and shallow permanent lake environments respectively in addition to the basic cyclicity the microfacies analysis reveals lake level variations on a larger scale as a consequence the astronomical forcing hypothesis of the cyclicity in the cascante section is explored further a climate modelling study of orbital extremes indicates that high lake levels could relate to enhanced net winter precipitation and runoff during precession minima consistent with mediterranean geological data using this phase relationship an astronomical tuning of the cycles is established starting from astronomical ages of magnetic reversal boundaries subsequently successive basic cycles are correlated to precession minima the tuning reveals an identical number of basic cycles in the cascante section as precession related sapropel cycles in the deep marine succession at monte dei corvi italy corroborating the precessional control of the basic cycles at cascante lake level highstands in the large scale cycle identified by the microfacies analysis relate to maxima in both the ca 100 and 405kyr eccentricity cycles again consistent with mediterranean geological data subtraction of the identified astronomically related lake level variations from the palaeoenvironmental record at cascante indicates a shift to deeper and more permanent lacustrine environments in the upper half of the section the cause of this shift remains unclear but it may be linked to tectonics non astronomical climate long period astronomical cycles or autogenic processes 2008 the authors journal compilation 2008 international association of sedimentologists

combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment an excess of fine sediment grain size 2 mm supply to rivers leads to reservoir siltation water contamination and operational problems for hydroelectric power plants in many catchments of the world such as in the french alps these problems are exacerbated in mountainous environments characterized by large sediment exports during very short periods this study combined river flow records sediment geochemistry and associated radionuclide concentrations as input properties to a monte carlo mixing model to quantify the contribution of different geologic sources to river sediment overall between 2007 and 2009 erosion rates reached 249 75 t km 2 yr 1 at the outlet of the bleone catchment but this mean value masked important spatial variations of erosion intensity within the catchment 85 5000 t km 2 yr 1 quantifying the contribution of different potential sources to river sediment required the application of sediment fingerprinting using a monte carlo mixing model this model allowed the specific contributions of different geological sub types i e black marls marly limestones conglomerates and quaternary deposits to be determined even though they generate locally very high erosion rates black marls supplied only a minor fraction 5 20 of the fine sediment collected on the riverbed in the vicinity of the 907 km2 catchment outlet the bulk of sediment was provided by quaternary deposits 21 66 conglomerates 3 44 and limestones 9 27 even though bioengineering works conducted currently to stabilize gullies in black marl terrains are undoubtedly useful to limit sediment supply to the bleone river erosion generated by other substrate sources dominated between 2007 and 2009 in this catchment

the elevation history of the tibetan plateau and its implications for the asian monsoon abstract the determination of the evolving palaeoaltitude of the tibetan plateau since the india eurasia collision underpins our understanding of how orography in central asia affects the intensity of the monsoon and hence global climate change palaeoaltitudes however cannot be measured directly and need to be inferred from proxy observations that are usually model dependent differing tectonic models for the behaviour of the lithosphere during continental collision have contrasting implications for the elevation of the plateau however two techniques recently employed for determining palaeo elevation are independent of tectonic models the first involving the variation with altitude of oxygen isotopes in precipitation and the second involving the change of leaf morphology with moist static energy of the atmosphere elevation studies have focused on southern tibet largely due to the relative ease of access to the region there is a remarkable unanimity amongst the diverse techniques applied that the altitude of the southern plateau has not significantly changed since at least the mid miocene ca 15 ma arguing for an onset of the monsoon system during or before the early miocene a range of tectonic studies suggest that the northern and eastern parts of the plateau are younger geomorphological features but there are few quantitative constraints of the timing of elevation from these regions of tibet since both the elevation and the surface area of the plateau impact on atmospheric circulation palaeoaltitude studies need to be extended to chart the increasing areas of elevated land surface through time

palaeo altimetry of the late eocene to miocene lunpola basin central tibet the elevation history of the tibetan plateau provides direct insight into the tectonic processes associated with continent continent collisions here we present oxygen isotope based estimates of the palaeo altimetry of late eocene and younger deposits of the lunpola basin in the centre of the plateau which indicate that the surface of tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years we conclude that crustal but not mantle thickening models combined with plate kinematic solutions of india asia convergence are compatible with palaeo elevation estimates across the tibetan plateau

variable source contributions to river bed sediments across three size fractions sediment tracing using geochemical properties is an efficient way to identify the spatial sources of transported sediments delivered to waterways here the contribution of soil sources to river bed sediments has been quantified in emu creek a headwater catchment in south eastern queensland australia soil samples were collected from the eight major rock types present in the catchment and were related to river bed sediments collected from eight sites along the main channel geochemistry as characterized by 39 elemental concentrations was measured using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry three particle size fractions were examined 10 10 63 and 63 212 m with the three resultant mixing models showing divergent results we conclude that the results of sediment mixing models based on the analysis of one grain size should not be assumed to apply across the entire particle size range of transported sediment emphasizing the need to match the size fraction used in tracing studies to that size fraction of interest in downstream sinks furthermore we present results highlighting the control transport distance plays in source dominance with this particularly evident in the coarser fraction where local sources dominate over more distant sources copyright 2015 john wiley sons ltd

quantifying the dominant sources of sediment in a drained lowland agricultural catchment the application of a thorium based particle size correction in sediment fingerprinting soil erosion is one of the main factors influencing land degradation and water quality at the global scale identifying the main sediment sources is therefore essential for the implementation of appropriate soil erosion mitigation measures accordingly caesium 137 137cs concentrations were used to determine the relative contribution of surface and subsurface erosion sources in a lowland drained catchment in france as 137cs concentrations are often dependent on particle size specific surface area ssa and novel thorium th based particle size corrections were applied surface and subsurface samples were collected to characterize the radionuclide properties of potential sources sediment samples were collected during one hydrological year and a sediment core was sampled to represent sediment accumulated over a longer temporal period additionally sediment from tile drains was sampled to determine the radionuclide properties of sediment exported from the drainage network a distribution modelling approach was used to quantify the relative sediment contributions from surface and subsurface sources the results highlight a substantial enrichment in fine particles and associated 137cs concentrations between the sources and the sediment the application of both correction factors reduced this difference with the th correction providing a more accurate comparison of source and sediment samples than the ssa correction modelling results clearly indicate the dominance of surface sources during the flood events and in the sediment core sediment exported from the drainage network was modelled to originate predominantly from surface sources this study demonstrates the potential of th to correct for 137cs particle size enrichment more importantly this research indicates that drainage networks may significantly increase the connectivity of surface sources to stream networks managing sediment transferred through drainage networks may reduce the deleterious effects of suspended sediment loads on riverine systems in similar lowland drained agricultural catchments

tibetan plateau aridification linked to global cooling at the eocene oligocene transition the eocene oligocene transition about 33 5 million years ago was a major global climate event the end of the eocene was unusually warm with no significant ice on antarctica but the oligocene saw the arrival of a permanent antarctic ice sheet two papers this week relate to the continental effects of this global change dupont nivet et al examined sedimentary records from the tibetan plateau and find a drop in atmospheric water which caused cooling and aridification coincident with antarctic cooling previous studies attributed this phenomenon to the rapid uplift of the tibetan plateau but this new work suggests that regional tibetan climate was influenced by global events in an unrelated paper on the same climate transition zanazzi et al explore the cooling in north america at the time using stable isotope measurements from fossil teeth and bones to create a proxy temperature record they find a large drop in mean annual temperature of 8 2 c a greater fall than seen in the oceans this continental transition may explain why many cold blooded reptiles and amphibians became extinct whereas mammals able to regulate their body temperature escaped relatively unscathed precisely dated evidence details that aridification on the tibetan plateau occurred at the time of the eocene oligocene transition in the marine records this suggests a direct link between the palaeontological and palaeoenvironmental changes recorded in continental asia at the time and global climate cooling continental aridification and the intensification of the monsoons in asia are generally attributed to uplift of the tibetan plateau and to the land sea redistributions associated with the continental collision of india and asia1 2 3 whereas some studies suggest that past changes in asian environments are mainly governed by global climate4 5 6 the most dramatic climate event since the onset of the collision of india and asia is the eocene oligocene transition an abrupt cooling step associated with the onset of glaciation in antarctica 34 million years ago7 8 9 however the influence of this global event on asian environments is poorly understood here we use magnetostratigraphy and cyclostratigraphy to show that aridification which is indicated by the disappearance of playa lake deposits in the northeastern tibetan plateau occurred precisely at the time of the eocene oligocene transition our findings suggest that this global transition is linked to significant aridification and cooling in continental asia recorded by palaeontological and palaeoenvironmental changes10 11 12 and thus support the idea that global cooling is associated with the eocene oligocene transition13 14 15 we show that with sufficient age control on the sedimentary records global climate can be distinguished from tectonism and recognized as a major contributor to continental asian environments

summer temperatures of late eocene to early oligocene freshwaters the marine foraminiferal isotope record displays a positive 18o shift early in the oligocene which has been identified as the onset of the antarctic oi 1 glaciation reported here are the first oxygen isotope derived summer paleotemperatures for continental freshwater in the northern hemisphere hampshire basin isle of wight uk leading up to and across this event these paleotemperatures are derived from multiple paleoproxies rodent tooth enamel gastropod shells charophyte gyrogonites and fish otoliths and are independent of freshwater evaporation effects and changes in ice volume we conclude that a fluctuating mesothermal climate existed but that there was no significant decrease in summer temperatures across the oi 1 glaciation this result is concordant with several other studies in suggesting that the majority of the isotopic shift in the marine realm across the oi 1 glaciation is linked to changes in antarctic ice volume and not to global temperature change our new approach has allowed us to derive numerical values for summer temperatures as well as to reconstruct relative temperature change across this key interval of the eocene oligocene transition

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

stable isotope records of cenozoic climate and topography tibetan plateau and tarim basin we seek to better understand growth of the tibetan plateau and associated climate change by presenting the first regionally extensive set of oxygen isotope data obtained from ca 40 m y of cenozoic strata from a 700 000 km2 area ranging from the northern edge of the tibetan plateau northward across the entire tarim basin our results reveal a previously unrecognized large positive isotope shift from eocene to oligocene which we suggest results from initial topographic growth of the himalayan tibetan system and attendant reorganization of climate by this growing mountain belt a negative isotopic shift recorded in miocene strata may reflect retreat of the neotethyan sea from the tarim basin as well as enhanced elevation of the himalaya tibetan plateau region and the rise of the tian shan which diverted moisture bearing westerlies and deepened aridity in the tarim basin and the northern tibetan plateau

effect of orogeny plate motion and land sea distribution on eurasian climate change over the past 30 million years the eurasian climates of today 10 million and 3o million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions the resulting climates compare well with various palaeoclimate records the retreat of the paratethys an epicontinental sea shifts the central asian climate from temperate to continental conditions and plays as important a role as uplift of the himalayan tibetan plateau in driving the asian monsoon changes

deposition and early alteration of evaporites summary the depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories marginal mixed shallow subaqueous and subaerial shallow and deep subaqueous these three environmental groupings hold for both marine and nonmarine settings although the details of continental evaporites may be far more complex than in most marine fed water bodies the primary evaporite morphologies from many continental playa hypersaline marine and marine marginal depositional settings are reasonably well understood because of the numerous detailed studies of recent holocene and cenozoic deposits that serve as models for sedimentary interpretation the sedimentological features that develop in deeper water settings are inferred based on examination of unaltered cenozoic deposits each environmental setting develops characteristic depositional features and patterns and one facies grades into the next because there may be significant physiochemical changes in water composition during deposition as well as sudden change s in both water depth and basinal circulation description and interpretation of evaporative rocks should not be based on mineralogy alone but on the distinct sedimentary characteristics of each part of a deposit in cases where sediments still reflect their primary mineralogy and morphology most of the environments can now be recognized however geochemical studies are commonly required to determine the source s of the original water the determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions bromine content of chloride salts and the stable isotopes of strontium sulphur carbon and oxygen only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled