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

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

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

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

catchment clearing accelerates the infilling of a shallow subtropical bay in east coast australia abstract understanding processes that govern the transport and distribution of terrestrial sediments to and within bays is critical for interpreting the drivers of long term changes in these ecosystems on the east coast of australia increased soil erosion and sediment delivery following extensive land clearing in the contributing catchments associated with european settlement is highlighted as a key driver of the decline of numerous nearshore habitats including seagrass meadows and in shore coral reefs here we use optical radiocarbon and radionuclide dating to estimate mass accumulation rates and type of terrestrial sedimentation in central moreton bay during the holocene we compare the long term rates of infilling within the central basin with the recent past and show a 3 9 fold increase in sediment accretion over the last 100 years compared to the long term last 1500 to 3000 yrs average infilling during the holocene is not spatially uniform with preferential deposition occurring within the now submerged palaeochannels of the brisbane and pine rivers we suggest that modern turbidity regimes in moreton bay are the result of the compounded effect of both a historical increase in fine sediment supply and a rapid decline in the effective storage capacity of the basin

a 1500 year record of river discharge inferred from fluvial marine sediments in the australian subtropics abstract in australia there is a scarcity of high resolution hyrdoclimate reconstructions for the last several millennia fluvial marine sediments offer a potential avenue for examining trends in freshwater input to coastal settings and by inference past hydroclimates here major elemental geochemistry 13c and c n ratios of organic matter grain size and diatom species abundance measured in a 4 4 m long sediment core collected from moreton bay in east coast australia are used to infer the relative freshwater discharge of the adjacent catchment over the last 1500 years reduced freshwater discharge into the bay occurred from 630 to 1200 ce especially between 1100 and 1200 ce a broad increase in discharge is indicated after 1300 ce extending to the present the initial shift to the prolonged wet period coincides with both a decrease in the frequency of dry el nino events based on regional records from the austral pacific and a broad hemispheric scale cooling trend this record provides further insight into low amplitude climate variability in the australian subtropics over the last 1000 years supporting efforts in both forecasting current and future climates and managing regional water resources importantly instrumental records do not cover the full range of natural climate variability experienced in the region over the last 1000 years

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

the dominant erosion processes supplying fine sediment to three major rivers in tropical australia the daly nt mitchell qld and flinders qld rivers abstract the tropics of northern australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of australia s water resource especially given the high potential for erosion when long dry seasons are followed by intense wet season rain here we use 137cs concentrations to determine the erosion processes supplying sediment to two major northern australian rivers the daly river northern territory and the mitchell river queensland we also present data from five sediment samples collected from a 100 km reach of the cloncurry river a major tributary of the flinders river queensland concentrations of 137cs in the surface soil and subsurface channel banks and gully samples were used to derive best fit probability density functions describing their distributions these modelled distributions are then used to estimate the relative contribution of these two components to the river sediments our results are consistent with channel and gully erosion being the dominant source of sediment with more than 90 of sediment transported along the main stem of these rivers originating from subsoil we summarize the findings of similar studies on tropical australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion previously as a result of catchment scale modelling sheet wash and rill erosion was considered to be the major sediment source in these rivers identifying the relative importance of sediment sources as shown in this paper will provide valuable information for land management planning in the region this study also reinforces the importance of testing model predictions before they are used to target investment in remedial action

suspended sediment dynamics in a southeast asian mountainous catchment combining river monitoring and fallout radionuclide tracers summary soil erosion is intense in mountainous tropical regions where heavy storms result in the supply of large quantities of sediment to rivers the origin and dynamics of suspended sediment were analysed in a catchment located in northern laos during the first erosive flood of the rainy season in may 2012 the catchment was equipped with 4 successive gauging stations draining areas ranging 0 2 11 6 km2 fallout radionuclides beryllium 7 7be unsupported pb 210 210pbxs and cesium 137 137cs were determined on rainfall overland flow stream water suspended sediment soil surface and subsurface samples with n 3 19 75 75 65 and 14 respectively assumptions underpinning the 7be labelling method were validated by implementing experiments in the laboratory i e rainwater 7be sorption to soil particles and in the field i e 7be 210pbxs activity ratio evolution in rainwater and related overland flow during a natural storm event radionuclide analyses provided a way to quantify variations in sediment dynamics and origin throughout the flood 1 a proportion of recently eroded sediment labelled by 7be and referred to as fresh sediment ranging between ca 8 35 in suspended loads 2 higher contributions of fresh sediment at the beginning of the flood rising stage 3 a progressive dilution of fresh sediment by particles remobilised from the riverbed channel 4 the dominance of particles originating from the soil surface ca 70 80 of total sediment load in upper parts and a much larger contribution of subsurface material ca 64 at the downstream station the original contribution of 7be labelled particles derived from collapsed riverbanks to sediment export was also demonstrated this pilot study supports the use of fallout 7be and 210pbxs in tropical catchments to constrain sediment dynamics it also puts forward the need to better characterize the sources of sediment in order to avoid possible misinterpretations

fallout 210pb as a soil and sediment tracer in catchment sediment budget investigations a review increasing anthropogenic pressures coupled with climate change impacts on natural resources have promoted a quest for innovative tracing techniques for understanding soil redistribution processes and assessing the environmental status of soil resources among the different existing tracers the fallout component of the radioisotope lead 210 also termed unsupported or excess lead 210 pb 210 ex when referring to its presence in soil or sediment arguably offers the broadest potential for environmental applications due to its origin and relatively long half life for more than five decades pb 210 ex has been widely used for dating sediments to investigate sedimentation processes and since the 1990s to provide information on the magnitude of soil and sediment redistribution the aim of this review is to provide a comprehensive evaluation and discussion of the various applications of pb 210 ex as a tracer in terrestrial and aquatic environments with particular emphasis on catchment sediment budget investigations this paper summarizes the state of the art related to the use of this tracer the main assumptions the requirements including the need for accurate analytical measurements and for parallel validation and the limitations which must be recognised when using this fallout radionuclide as a soil and sediment tracer lessons learned and current and future research needs in the environmental and radiochronological application of pb 210 ex are also presented and discussed c 2014 elsevier b v all rights reserved

evidence for separation across a gray band on europa abstract thynia linea a gray band on europa is found to be a 25 km wide and 900 km long region of lithospheric separation which has been infilled by relatively dark material roughly a dozen older features and the cuspate segments that form its outline appear to have been displaced across its width displacement azimuths indicate a best fit pole of opening near 79 s 200 w however displacement magnitude decreases toward either end of the gray band indicating that it is more akin to a tear in a nonrigid europan lithosphere opening was in response to nw se directed tensile stress in accord with the stress predictions of nonsynchronous rotation observations of thynia linea are consistent with a laterally mobile brittle lithosphere decoupled from ductile or liquid material below as previously suggested to account for opening of wedge shaped bands in europa s antijovian region lithospheric separation and contemporaneous emplacement of new material offers a possible volcano tectonic scenario for resurfacing europa if this process is ongoing resurfacing can be accomplished on a time scale consistent with the satellite s surface age if one gray band or zone of wedge shaped bands forms every 10 3 10 4 yr and becomes unrecognizable with age this would imply that features on europa brighten with age as through continuous deposition of frost onto the surface

evaluation of models for the formation of chaotic terrain on europa chaotic terrain on europa is interpreted to be the result of the breakup of brittle surface materials over a mobile substrate two end member models have been proposed for the mobile substrate a liquid water ocean or solid warm ductile ice direct contact between the brittle surface ice and an underlying ocean might be accomplished by melting through europa s ice shell but plausible sources of thermal energy are insufficient to locally melt through the ice shell we calculate that a liquid or partially liquid substrate is probably necessary for tilted blocks to be observed challenging a solid state model we propose that a model in which chaos areas on europa formed over bodies of melt or partial melt within the ice shell may be the best match to observational and thermal constraints such bodies of melt within the ice shell may be triggered by warm diapirs of relatively clean ice that partially melted an overlying layer of lower melting temperature such as ice contaminated with salts

determining the origins and history of sedimentation in an underground river system using natural and fallout radionuclides abstract natural and anthropogenic radionuclides were used to characterize the source of sediment reaching the underground river in the karst system at jenolan new south wales australia it was found that the relationship between 226 ra and 232 th concentrations in both spatially averaged soil samples and transported sediments distinguished between two of the most likely source subcatchments sedimentary sequences collected from within the underground system showed that contemporary deposition was made up of an equal mixture of sediment from these two sources however at least three earlier deposition periods were also identifiable each with different relative contributions from the source catchments the first appearance of 137 cs in the sedimentary sequence and correlations with historical information provided a chronology for these changes and it is concluded that the contemporary phase was initiated in the early 1950s most probably by forestry activities this work demonstrates that natural radioactivity can be used as a tracer of the origins of sediment providing an important new approach to problems in sediment supply transport and deposition

geologic mapping of europa galileo data enable the major geological units structures and surface features to be identified on europa these include five primary units plains chaos band ridge and crater materials and their subunits along with various tectonic structures such as faults plains units are the most widespread ridged plains material spans a wide range of geological ages including the oldest recognizable features on europa and appears to represent a style of tectonic resurfacing rather than cryovolcanism smooth plains material typically embays other terrains and units possibly as a type of fluid emplacement and is among the youngest material units observed at global scales plains are typically mapped as undifferentiated plains material although in some areas differences can be discerned in the near infrared which might be related to differences in ice grain size chaos material is composed of plains and other preexisting materials that have been severely disrupted by inferred internal activity chaos is characterized by blocks of icy material set in a hummocky matrix band material is arrayed in linear curvilinear wedge shaped or cuspate zones with contrasting albedo and surface textures with respect to the surrounding terrain bilateral symmetry observed in some bands and the relationships with the surrounding units suggest that band material forms by the lithosphere fracturing spreading apart and infilling with material derived from the subsurface ridge material is mapped as a unit on local and some regional maps but shown with symbols at global scales ridge material includes single ridges doublet ridges and ridge complexes ridge materials are considered to represent tectonic processes possibly accompanied by the extrusion or intrusion of subsurface materials such as diapirs the tectonic processes might be related to tidal flexing of the icy lithosphere on diurnal or longer timescales crater materials include various interior smooth central rough inner and annular massif and exterior continuous ejecta subunits structural features and landforms are shown with conventional symbols type localities for the units are identified along with suggestions for portraying the features on geological maps including colors and letter abbreviations for material units implementing these suggestions by the planetary mapping community would facilitate comparisons of maps for different parts of europa and contribute to an eventual global synthesis of its complex geology on the basis of initial mapping results a stratigraphic sequence is suggested in which ridged plains form the oldest unit on europa followed by development of band material and individual ridges band materials tend to be somewhat older than ridges but in many areas the two units formed simultaneously similarly the formation of most chaos follows the development of ridged plains although chaos is among the youngest materials on europa some chaos units might have formed contemporaneously with ridged plains smooth plains generally embay all other units and are late stage in the evolution of the surface c 1 craters are superposed on ridged plains but are crosscut by other materials including bands and ridges most c2 craters postdate all other units but a few c2 craters are cut by ridge material c3 craters constitute the youngest recognizable material on europa

fingerprinting suspended sediment sources in the catchment of the river ouse yorkshire uk statistically verified composite fingerprints and a multivariate mixing model have been employed to establish the main sources of the suspended sediment transported through the lower non tidal reaches of the river ouse and one of its main tributaries the river wharfe during the period 1994 1997 in the case of the suspended sediment samples collected from the river ouse the load weighted mean contributions from uncultivated topsoil cultivated topsoil and channel bank sources were estimated to be c 25 38 and 37 respectively while for the river wharfe these sources contributed c 70 4 and 23 respectively c 4 was derived from woodland topsoil suspended sediment samples collected during higher flows evidenced a greater contribution from channel banks than samples collected during lower flows source materials were also differentiated according to the three main geological source areas carboniferous permian and triassic and jurassic and their load weighted mean contributions were estimated to be c 24 41 and 35 for the river ouse and c 91 9 and 0 there are no jurassic rocks in this catchment for the river wharfe respectively when suspended sediment samples from tributary streams were used to characterize each geological source area the equivalent results for the river ouse were c 30 46 and 24 considering the three main tributaries that contribute to the river ouse the load weighted mean contributions from the rivers swale ure and nidd were estimated to be 82 15 and 3 respectively these values have been compared with estimates of the relative magnitude of the annual suspended sediment loads of these three rivers for the years 1995 and 1996 derived from continuous monitoring of discharge and turbidity differences between the two sets of results are ascribed to the different periods of record involved and to the timing of suspended sediment sampling relative to the overall storm hydrograph and thus the degree to which the available samples are representative of the overall suspended sediment flux although a number of limitations must be recognized the fingerprinting approach to source ascription is seen as providing valuable information regarding suspended sediment sources in the study catchments copyright 1999 john wiley sons ltd

use of floodplain sediment cores to investigate recent historical changes in overbank sedimentation rates and sediment sources in the catchment of the river ouse yorkshire uk abstract floodplain sediment cores collected from seven sites in the catchment of the river ouse in yorkshire uk have been used to provide information on recent historical changes in both rates of overbank sedimentation and sediment sources the environmental radionuclides 137 cs and unsupported 210 pb have been used to establish chronologies for each core and to estimate average sediment accumulation rates for the last ca 30 and 100 years respectively average sedimentation rates for the individual cores ranged from 0 11 to 1 04 g cm 2 yr 1 in all but one case the estimates of average sedimentation rate during the last ca 30 years for the individual cores are broadly similar to those for the last ca 100 years suggesting that overbank sedimentation rates have been essentially uniform over the longer time period composite fingerprints based on a combination of geochemical and mineral magnetic properties and a numerical mixing model have been used to investigate downcore changes in sediment source in the case of source type most of the cores reflect a primarily topsoil source although there have been periods with increased contributions from subsoil channel bank sources within the ouse basin in general the period commencing in the late 19th and early 20th century and extending through to the 1960s was characterised by increased contributions from topsoil sources however contributions from subsoil channel bank sources have increased over the last few decades the source tracing results relating to sediment contributions from the three main geological topographic zones are in broad agreement with the proportion of the area of the catchment underlain by each rock type temporal variations in the contributions from the three geological topographic zones vary from site to site but for the lower reaches of the river ouse contributions from areas underlain by permian and triassic rocks which mainly outcrop in the vale of york have increased since the turn of the century the changes in sediment source identified are probably a reflection of changes in land use and management and possibly changes in climate these results enable estimates of contemporary suspended sediment fluxes and sources to be placed into a historical context and provide a means of considering the likely impact of potential future changes in land use and climate in the study basin

paleoclimatic fingerprints of ferromanganese nodules in subtropical chinese soils identified by synchrotron radiation based microprobes abstract ferromanganese nodules are important pedogenic indicators in soil they are usually characterized by clearly expressed ring structures although these features are believed to be significant environmental fingerprints the reasons for their formation still await interpretation here we interpreted these fingerprints by the synergistic use of noninvasive synchrotron radiation based techniques and advanced analytical methods the results revealed that the soil nodules were formed due to the filling of the pore networks of the soil matrix that was mediated by both abiotic and biotic factors during alternative soil wetting drying cycles the ring structures are therefore the memories of the soil redox history the variations in elemental compositions of the ring structures indicates the soil moisture conditions at the time of formation their porosity reflects the rate of change in soil redox potential and the soil redox potential is mainly affected by precipitation

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

identifying subsoil sediment sources with carbon and nitrogen stable isotope ratios increased sediment loads from accelerated catchment erosion significantly degrade waterways worldwide in the south east queensland region of australia sediment loads are degrading moreton bay a ramsar listed wetland of international significance in this region like most parts of coastal australia sediment is predominantly derived from gully and channel bank erosion processes a novel approach is presented that uses carbon and nitrogen stable isotope ratios and elemental composition to discriminate between these often indistinguishable subsoil sediment sources the conservativeness of these sediment properties is first tested by examining the effect of particle size separation testing for consistency during transport and the effect of sampling at different times testing for temporal source consistency the discrimination potential of these sediment properties is then assessed with the conservative properties based on the particle size and temporal analyses modelled to determine sediment provenance in three catchments nitrogen sediment properties were found to have significant particle size enrichment and high temporal variance indicative of non conservative behaviour conversely carbon stable isotopes had very limited particle size and temporal variability highlighting their suitability for sediment tracing channel erosion was modelled to be a significant source of sediment 51 9 contrasting desktop modelling research that estimated gully erosion is the predominant sediment source to limit the supply of sediment to moreton bay channel bank and gully erosion must both be targeted by sediment management programs by distinguishing between subsoil sediment sources this approach has the potential to enhance the management of sediment loads degrading waterways worldwide copyright 2014 john wiley sons ltd

europa stratigraphy and geological history of the anti jovian region from galileo e14 solid state imaging data a tidal bulge and associated deformation are predicted to occur in europa s anti jovian region voyager data showed polygonal low albedo bands in this region it was demonstrated that when the low albedo material comprising these bands was removed the margins could be reconstructed suggesting that fracturing and lateral separation has occurred higher resolution galileo images of a 300 000 km2 portion of the anti jovian region permit recognition and mapping of a variety of features and documentation of the geological history we identify background ridged plains several distinctive types of bands and ridges lenticulae and regions of chaotic terrain these images are at relatively low incidence angles thus albedo variations predominate over topography this presents a challenge to morphologically based mapping but does not preclude development of a regional stratigraphy stratigraphic relationships show that dark bands crosscut the bright ridged plains and are themselves disrupted by lenticulae and chaos suggesting a geological history beginning with background ridged plains followed by a period dominated by band formation with the most recent history predominantly characterized by formation of lenticulae and chaos the paucity of impact craters in this region indicates that the entire sequence of units is geologically recent

the application of fallout radionuclides to determine the dominant erosion process in water supply catchments of subtropical south east queensland australia previous studies using fallout radionuclides 137cs and 210pbex to determine the relative contributions of surface soil and channel erosion including gullies and channel banks to stream sediments have used a relatively small number of composite samples 25 to characterize the source end members and concentrations in each of the source end members have through the use of means and standard errors been assumed to be normally distributed here we examine 137cs activity concentrations to determine the erosion processes supplying sediment in seven water supply catchments in south east queensland first we test some of the underlying assumptions in the method using concentrations of 137cs and 210pbex in composite samples collected from 109 surface soil sites and 39 channel bank sites paired composite samples each consisting of 20 subsamples from five sites are used to demonstrate that this sampling approach was sufficient to average out any local variations in surface soil 210pbex and 137cs concentrations across the 300 m2 sampled we derive probability distributions for 137cs and 210pbex concentrations in the group of samples from each of the end members and show that only the distribution of 210pbex in samples from surface soils is normally distributed we use the probability distributions for 137cs which provides the greatest discrimination between sources to show that the 137cs concentrations on the river sediment samples are consistent with channel erosion being the dominant source conservation works aimed at reducing the supply of sediments in these catchments should therefore focus on rehabilitation of the channel network and decreasing the runoff to the channel network these findings are consistent with other similar studies on tropical australian rivers copyright 2012 john wiley sons ltd

brine mobilization during lithospheric heating on europa implications for formation of chaos terrain lenticula texture and color variations the background lineated plains on europa are locally highly modified and destroyed in regions known as chaos and lenticulae produced there are 1 isolated fragments and polygons of background material which rotate and translate 2 matrix which fills in the areas between the fragments and polygons and 3 surface discolorations using observations and constraints from high resolution galileo images we find that a model for the formation of these terrains which involves mobilization and migration of brines and a possible percolation phase transition as the europan lithosphere is warmed can readily explain the vast majority of their characteristics in addition the presence of melt fractions of a few percent in the adjacent ice framework may enhance the creep rate and the accompanying deformation rates the characteristics and distribution of lenticulae suggest that among the strong candidates for heat sources for brine migration and ice mobilization processes is diapirism linked to solid state convection in a layer underlying a brittle lid and possibly overlying a liquid water layer

suspended sediment sources and transport distances in the yellowstone river basin the activity of fallout radionuclides 7 be 1 3 7 cs and 2 1 0 pb was measured on upland and floodplain soils and on suspended sediments to quantify sources of fine sediment and to estimate sediment transport distances in stream channels in the yellowstone river basin samples were collected seven times during snowmelt and runoff at nine locations from the headwaters of soda butte creek to billings montana a 423 km long reach of channel the inventory of radionuclides in soil increases with precipitation and is highest in the headwaters the activity of radionuclides in suspended sediment decreases downstream and more activity is observed earlier than later in the flood hydrograph the radionuclide activity of sediment derived from erosion of upland soils differs from that derived from bank erosion fine suspended sediment has an intermediate radionuclide signature that is quantified in terms of the relative contribution of these two sources of fine sediment at sites high in the drainage soils contribute 50 to the suspended load and this value decreases to 11 26 downstream fine sediment transport distances were calculated from the exponential decrease in radionuclide concentration below a point source transport distances increase from a few kilometers in the headwaters to hundreds of kilometers downstream these estimates are consistent with transport distances estimated from the settling velocity of the particles and from the distribution of mine tailings downstream from a dam failure this study of a large watershed confirms earlier results from smaller basins and suggests that transport distances increase with basin size

geologic mapping of the northern leading hemisphere of europa from galileo solid state imaging data the northern leading hemisphere of europa was imaged at regional mapping resolution 230 m pixel by the galileo spacecraft ssi camera we produced geologic maps from a regional scale mosaic and a high resolution inset of this region twelve geologic units were sufficient to produce correlative geologic maps at both regional and local scales stratigraphic relationships indicate four major episodes in the geologic history of this area the first episode includes background plains formation and modification followed by a second period of extensive lineament formation the third episode included extensive chaotic disruption of the surface at low and middle latitudes the final episode includes the formation of new sets of ridges and bands especially at high latitudes the low crater density indicates that all these episodes in europa s geologic history are geologically recent the latitudinal distribution of chaos areas broadly matches that of areas of crustal thinning from models of tidal heating we show that stress directions rotated clockwise with time which is consistent with predictions from global stress models involving tidal deformation and nonsynchronous rotation of europa s crust on the basis of the change in lineament orientation with time the reconstructed longitudinal positions of the studied area indicate that europa s crust completed a full rotation relative to the tidally deformed interior

determining sources and transit times of suspended sediment in the murrumbidgee river new south wales australia using fallout 137cs and 210pb sediment budgets typically require an estimate of the proportional yield from erosion sources to sediments in transport and storage this becomes increasingly difficult as catchments become larger and erosion storage and deposition processes become more complex we demonstrate how fallout radionuclides can be used to estimate the proportional contributions to sediment load from a tripartite classification of erosion sources in a large catchment the mid murrumbidgee 13 500 km2 the three major potential sources of sediment within this catchment are cultivated lands 22 of the surface area uncultivated pastoral lands 78 and the numerous channels and gullies found in this region concentrations of the fallout radionuclides 210pbex and 137cs in representative samples from each of these three sources are significantly different employing these values in a simple mixing model shows that the largest contribution of material is currently derived from subsoil channel gully sources alterations to the suspended sediment 210pbex signature by in situ labeling and decay are also considered applying the model with different concentrations of 210pbex decayed as a function of residence time in channels suggests that the mean residence time of fine grained material within this system is 10 5 years however differences in 137cs concentrations observed between flood and low flow sediments and the presence of the short lived cosmogenic 7be suggest that residence time of some of this fine grained material may be of the order of only weeks to months

sediment sources and channel dynamics daly river northern australia the daly river occupies a mainly undisturbed large catchment in the australian wet dry tropics concerns about possible increased sediment input to the river from clearing and cropping have motivated this study of fine sediment sources using geochemical tracers for both modern sediments and alluvial bench deposits it is shown that for the last 30 years 89 97 of the fine sediment originates from erosion by gullying and channel change there is no discernible input of top soil from the cleared land adjacent to the daly river in the study area the analysis and osl dating of the alluvial benches have also provided data on the age of and inferences about the causes of bench formation flood frequency change sedimentation rate change and episodes of sand transport the benches are being destroyed as the channel widens contributing sediment to the river and the bed of the daly appears to be shallowing both responses to increased overbank flows the sediment source created by channel widening is almost all the result of hydrologic change with no discernible role for land use

does europa have a subsurface ocean evaluation of the geological evidence it has been proposed that jupiter s satellite europa currently possesses a global subsurface ocean of liquid water galileo gravity data verify that the satellite is differentiated into an outer h2o layer about 100 km thick but cannot determine the current physical state of this layer liquid or solid here we summarize the geological evidence regarding an extant subsurface ocean concentrating on galileo imaging data we describe and assess nine pertinent lines of geological evidence impact morphologies lenticulae cryovolcanic features pull apart bands chaos ridges surface frosts topography and global tectonics an internal ocean would be a simple and comprehensive explanation for a broad range of observations however we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm soft ice with only localized or partial melting two different models of impact flux imply very different surface ages for europa the model favored here indicates an average age of 50 myr searches for evidence of current geological activity on europa such as plumes or surface changes have yielded negative results to date the current existence of a global subsurface ocean while attractive in explaining the observations remains inconclusive future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within europa today

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