analysis of gully dimensions and sediment texture from southeast australia for catchment sediment budgeting abstract catchment scale sediment budgeting models are increasingly being used to target remediation works aimed at controlling erosion and improving water quality gully erosion is often a major sediment source and needs to be accounted for in such models in a manner consistent with the scale of analysis and available data using 130 measurements of gully cross sectional area and 45 measurements of gully wall sediment texture the variability in gully dimensions and particle size distribution for the lake burragorang catchment in australia is examined the distribution of gully cross sectional area measurements is log normally distributed and modelling indicates a representative value of 23 m 2 be used in catchment sediment budgeting applications the proportion of gully eroded sediment contributing to the bedload budget defined as particles 63 m diameter of a river link is approximately half though may be higher in igneous landscapes a continental scale spatially distributed subsoil texture dataset provided limited capacity to predict the finer scale spatial variation in the proportion of sediment contributing to bedload from gully erosion within the lake burragorang catchment

degradation of the mitchell river fluvial megafan by alluvial gully erosion increased by post european land use change queensland australia along low gradient rivers in northern australia there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains on the mitchell river fluvial megafan in northern queensland river incision and fan head trenching into pleistocene and holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion in this study rates of alluvial gully erosion into incipiently unstable channel banks and or pre existing floodplain features were quantified to assess the influence of land use change following european settlement alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent gps surveys and historic air photos demonstrating rapid increases in gully area of 1 2 to 10 times their 1949 values extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950 which is post european settlement this is supported by young optically stimulated luminescence osl dates of gully inset floodplain deposits lidar terrain analysis historic explorer accounts of earlier gully types and archival records of cattle numbers and land management it is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks adjacent floodplain hollows and precursor gullies this is a result of reduced native grass cover increased physical disturbance of soils and the concentration of water runoff along cattle tracks in addition to fire regime modifications episodic drought and the establishment of exotic weed and grass species geomorphic processes operating over geologic time across the fluvial megafan predisposed the landscape to being pushed by land used change across an intrinsically close geomorphic threshold towards instability the evolution of these alluvial gullies is discussed in terms of their initiation development future growth and stabilisation and the numerous natural and anthropogenic factors influencing their erosion

in stream wetlands and their significance for channel filling and the catchment sediment budget jugiong creek new south wales abstract evidence is presented here of recent and extensive infilling of the incised channel network of the jugiong creek catchment se australia the present channel network resulted from widespread stream and gully incision in the period between 1880 and 1920 our survey shows that gully floors have been colonised extensively by emergent macrophyte vegetation since before 1944 forming continuous dense in stream wetlands which now cover 25 of the channel network in the 2175 km 2 catchment and have so far trapped almost 2 000 000 t of nutrient enriched fine sediments this mass of sediments represents the equivalent of 4 7 years of annual sediment production across the catchment and in some tributaries more than 20 years of annual yield is stored within in stream wetlands previous work on the late quaternary stratigraphy of the region has shown that there were repeated phases of channel incision in the past following which the channels quickly stabilised by natural means and then filled with fine grained sediment to the point of channel extinction creating unchannelled swampy valley floors the current formation and spread of in stream wetlands is interpreted to be the onset of the next infill phase but it is not known whether present conditions will allow complete channel filling and reformation of the pre existing swampy valley floors nevertheless further spread of in stream wetlands is likely to increase the sediment trapping capacity and further reduce the discharge of sediments and nutrients into the murrumbidgee river the in stream wetlands may provide a significant capacity to buffer erosion from gullied catchments of considerable size up to 300 km 2 as an adjunct to current riparian management options they may also assist the recovery of sediment impacted channels downstream

elastic wave velocities of forsterite and its β spinel form and chemical boundary hypothesis for the 410 km discontinuity a method for measuring elastic wave velocities at pressures up to 15 gpa has been developed velocities of forsterite and spinel were measured using a piston cylinder apparatus with a pulse echo overlap method for pressures up to 4 gpa and using a split sphere apparatus with a pulse transmission technique for higher pressures to validate the results volume compression incompressibility and rigidity were estimated from measured travel times and comparison was made between the present estimates and data from x ray brillouin and acoustic measurements the v p and k values for spinet are 3 and 8 higher than previous measurements at 10 gpa respectively velocity jumps in v p and v s due to olivine to spinel transition were about 1 34 and 0 80 km s 1 respectively very different from seismological observations of velocity jumps at the 410 km discontinuity which were concentrated around 0 45 km s 1 for the p wave and 0 22 km s 1 for the s wave velocity jumps in mantle peridotite were calculated using the experimental results and comparison was made between these estimates and seismological observations at the 410 km discontinuity the evidence does not support the phase change hypothesis and a chemical boundary was proposed as the origin of the 410 km discontinuity an eclogitic mineral assemblage might be an alternative for the composition of the transition layer

trends and controls of holocene floodplain sedimentation in the rhine catchment article i nfo holocene floodplain sedimentation in the rhine catchment is controlled by human and climate impacts intricate river behaviour modifies the fluvial response to the external impacts making cause effect analysis difficult especially on large spatial scales to better understand the relative importance and interdependencies of external and internal controls temporally resolved floodplain sedimentation rates are established using three different methods i floodplain storage studies on the trunk stream ii depth age analysis of overbank deposits from different parts of the catchment and iii cumulative frequency distributions of 14 c ages from floodplain deposits from various parts of the catchment the applied methodology strongly differs with the available temporal resolution and the size of the corresponding catchment all three methods show a strong increase in sedimentation rate for more recent periods that can be linked to increasing human impact evidences for climate impacts and intricate river behaviour are less clear and hindered by insufficient temporal resolution of the currently available data

river stabilisation due to changing climate and vegetation during the late quaternary in western tasmania australia abstract the stanley river in western tasmania australia contains sub fossil rainforest logs within the channel and floodplain of the more than 85 radiocarbon dates obtained all but 3 date from 17 ka to the present and permit an interpretation of fluvial and related environmental changes over this period particular attention is focused on the interactive relationship between the river and its riparian rainforest following the last glacial maximum the stanley river was a laterally active gravel load system reworking most of its valley floor in the upstream reaches with ameliorating conditions at the end of the pleistocene climate became less seasonal and flow regimes less energetic huon pines already present in the catchment re asserted themselves in the form of dense tree cover along the river banks and floodplains with basal floodplain deposition shifting from gravels to coarse sands and granules by about 3 5 ka a further change in climate reduced stream discharges substantially as a result the channel reduced in size transported finer sediment became laterally stable and the floodplain accreted with overbank deposits of sand and silt huon pines falling into the channel formed obstructions of woody debris some surviving for 2 ka these have reduced stream power and boundary shear stress further contributing to channel stability generational sequences of huon pines on the river banks some extending back 1 2 ka are additional evidence of this stability since the pleistocene changing climate and the re establishment of dense riparian rainforest appear to have stabilised the river channels and floodplains of western tasmania

sediment deposition in the flood plain of stemple creek watershed northern california abstract over the past 150 years major land use changes have occurred in the stemple creek watershed in northern california that have caused erosion to move soils from the upland to the flood plain stream channels and the bay the purpose of this study is to document the recent 1954 to present sediment deposition patterns in the flood plain area adjacent to stemple creek using the 137 cesium technique sediment deposition ranged from 0 26 to 1 84 cm year 1 for the period from 1964 to 2002 with an average of 0 85 0 41 cm year 1 sediment deposition rates were higher for the 1954 to 1964 period with a range of 0 31 3 50 cm year 1 and an average of 1 29 1 04 cm year 1 these data indicate that sediment deposition in the flood plain has decreased since the middle 1950s probably related to reduction in row crop agriculture and an increase in pasturelands this study shows that the flood plains in the stemple creek watershed are a significant sink for the soils being eroded from the upland area given the significance of the flood plain for trapping eroded materials before they reach the stream channels or the bay efforts need to be made to manage these flood plain areas to insure that they do not change and become a source rather than a sink for eroded materials as improved management practices on the upland areas reduce sediment input to the flood plain

combining a spatial model with geochemical tracers and river station data to construct a catchment sediment budget 1 information about diffuse pollutant sources in river catchments and the processes responsible for their generation is often obtained using geochemical tracing in stream monitoring or process based modeling yet these methods are rarely combined in this study we combine these three methods to produce a catchment sediment budget for the lake burragorang catchment in australia the physically based process model sednet was modified using local catchment data to constrain predicted hillslope erosion rates in forested areas the rate and texture of sediment supply from gully erosion and the predicted floodplain deposition rates the model s capacity to match the geochemical tracer both spatial source and erosion process data and gauging station load data improved markedly hillslope erosion primarily in the steeper mainly forested areas near the reservoir is identified by the model as the main source of sediment delivered to lake burragorang the contribution from gully and river bank erosion is comparatively small though gully erosion can be locally dominant this result is consistent with the tracer data utilizing multiple independent data sets allows for a more rigorous evaluation of model performance and it is argued increases the likelihood that the model is correctly representing the main components of the catchment s sediment budget the identification of diffuse sediment sources in other catchments can clearly benefit from combining a range of observational data with a structured model evaluation process

towards an understanding of the ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record abstract in this contribution we explore the idea that the ca isotope proxy has utility as an indicator of carbonate authigenesis i e post depositional precipitation of caco3 within the sedimentary package given the strong contrast in isotopic fractionation factor between the formational and diagenetic environments ca isotopes have the potential to fingerprint carbonate authigenesis when it occurs close to the seawater sediment interface we demonstrate that ca isotopes are particularly applicable to exploring ocean acidification events and potentially ocean anoxic events and focus our attention on ocean acidification related to the paleocene eocene thermal maximum petm we present three scenarios that vary in the magnitude and duration of the carbon fluxes that are simulated using an earth system model of intermediate complexity cgenie and we use the cgenie output to constrain the upper boundary conditions of 1 d reactive transport models of authigenesis and recrystallization in the sedimentary section along with simple mixing calculations the models inform our exploration of the hypothesis that authigenic carbonate induced by a saturation state overshoot during the petm explains recently published ca isotope records and perhaps bulk carbonate records over ocean anoxic event oae 2 our simulations suggest that fractionation factor variability does not explain the petm 44ca records and we propose a 44ca caco3 space framework to assist with the elucidation of authigenic additions over time scales that are short relative to the residence time of ca in the ocean 1 ma ultimately we find that the authigenic zone generated in the sedimentary column may be influenced by alkalinity overshoots or redox state the caco3 produced in this zone can overprint temporal signals with depth dependent signals that reflect lithology and sedimentation rate and need not be spatially uniform even when driven by a global event ultimately we demonstrate the utility of ca isotopes for exploring short time scale climatic events and a quantitative framework to guide interpretations

the yamal peninsula lake baikal deep seismic sounding profile seismograms from three nuclear explosions recorded along a 2400 km long deep seismic sounding profile extending from the yamal peninsula to lake baikal are presented we have constructed a preliminary 1 d compressional velocity model to fit the major travel time features of the data clear differences between the seismograms from each shot imply that the velocity structure of the crust and upper mantle is variable along the profile estimated crustal thicknesses range from 47 km beneath the west siberian rift to 42 km beneath the siberian craton the structure of the upper mantle above the transition zone consists of material with p wave velocities ranging from 8 25 km s at the moho to 8 53 km s at 225 km velocities increase abruptly at 225 km depth to 8 63 km s there is little evidence for a pronounced low velocity zone although small velocity reversals are required to terminate several branches of the travel time curve the uppermantle transition zone discontinuity at 425 km depth consists of a 5 6 first order velocity increase the lower discontinuity has a 4 9 velocity increase over the depth range 656 5 to 659 km

the recent history of erosion and sedimentation on the southern tablelands of southeastern australia sediment flux dominated by channel incision abstract as in other regions colonised from europe within the last few centuries australia s vegetation and soils have been dramatically changed by clearing cropping and grazing in southeastern australia particularly on the southern tablelands the impacts of european settlement are clearly manifested by channel incision by using stratigraphic and documentary evidence in conjunction with aerial photographs sediment budgets for the post settlement period have been constructed to define the fluxes and stores of sediment for each of the major geomorphic components of the 136 km2 catchment of jerrabomberra creek near canberra using these budgets and some plausible assumptions it has been possible to approximate the history of both the sediment delivery ratio and sediment yield for this catchment while the quantities estimated in this analysis are approximations the trends through time are credible sediment yield increased rapidly to a peak after european settlement and has returned to a level between the peak and the pre european value the delivery ratio has followed a similar trend the most general conclusion to emerge is that in this landscape both the total sediment flux and the sediment yield of the catchment have been dominated by channel erosion this result is contrary to the findings in many parts of the world where sheet and rill erosion dominates the fluxes the soil conservation implication of these results is clear to control off site effects of erosion the focus must be on the channels

holocene valley aggradation and gully erosion in headwater catchments south eastern highlands of australia late quaternary stratigraphy of a 50 km2 catchment on the south eastern highlands of australia reveals processes and history of denudation and helps resolve a long standing debate about factors controlling episodic valley aggradation and degradation during holocene times valley sedimentation occurred when swampy vegetation fully colonized valley floors and obliterated all channels promoting aggradation for periods of several thousand years with most incoming sediment being trapped in swampy meadows much of the sediment was reworked from late pleistocene alluvial fan and valley fill deposits and primary hillslope erosion was minor during the holocene differing sedimentation patterns between the late pleistocene holocene and post european settlement periods reflect regional changes in sediment supply and transport capacity as a result of major environmental change within the holocene however valley fill stratigraphy is controlled by massive episodic gully erosion terminating aggradation gully initiation appears to be controlled more by thresholds of incision into vegetated valley floors than by changes to sediment supply whether the thresholds are exceeded because of climatic change autonomous change or extreme events cannot yet be determined overall the holocene history represents continuing complex response to events of the late pleistocene and does not support the k cycle concept which has strongly influenced late quaternary geomorphology in australia

alternative chronologies for late quaternary last interglacial holocene deep sea sediments via optical dating of silt sized quartz abstract we summarize the results of a test on the potential of optical dating for the age assessment of late quaternary deep sea sediments our approach combines a single aliquot regeneration sar protocol for equivalent dose d e estimation on fine silt sized quartz with a time dependent evaluation of supported and unsupported long lived radioisotopes within the deposited sediment matrix for this purpose nine samples from two independently dated deep sea cores from the indian ocean were obtained the sar analysis resulted in mean d e estimates with precisions ranging from 0 9 to 3 7 combination of these data with measured radioisotope concentrations resulted in stratigraphically sensible ages ranging from ca 7 to 120 ka these ages exhibit good agreement with existing chronologies for the cores based on radiocarbon age determinations and correlation of key volcanic palaeoecological and isotopic events optical dating may provide an important additional dating method for late quaternary deep sea sediments

introduction to calcium isotope geochemistry past lessons and future directions abstract calcium ca isotopes have been utilized as geochemical tools since the 1970s increasing in popularity and scope since the mid to late 1990s research conducted over the past thirty years has revealed a range of applications for ca isotopes that are highlighted in this introduction and special issue as well as a series of interesting and fundamental problems that have yet to be resolved for such a chemically simple system in comparison to redox active elements for instance the level of complexity is both surprising and intellectually attractive while the advent of multiple collector inductively coupled plasma mass spectrometers made metals such as fe mg and zn considerably more accessible analytically the precision and ease of ca isotopic analysis did not radically improve in a comparable manner for a variety of reasons one of which may be perceived analytical difficulty the application of ca isotopes to geological questions remains in the shadows to some extent in the geosciences in this introduction we identify i areas that we think are most fertile for the application of ca isotopes as tools and ii outstanding questions and future directions that can move the field towards increased utility and broader acceptance by the geosciences community

modeling impacts of erosion and deposition on soil organic carbon in the big creek basin of southern illinois abstract land use land cover lulc plays an important role in influencing the spatial intensity of water erosion which is the primary governor of horizontal translocation of soil organic carbon soc the fate of redistributed soc through erosion remains debatable and the mineralization rate of exposed soc protected in soil aggregates is the major focus of this argument cohesive spatially explicit modeling of soc and erosion can potentially reduce some of the controversy to this end we simulated erosion deposition and photosynthetic in situ flux of soc in a small watershed of 28 42 ha located in the big creek basin of southern illinois the main objectives of this research were a to study erosion and deposition dynamics under different lulc b to examine the extent of carbon dislocation and deposition possible in the study area and c to determine the net soc accretion and reduction possible by accounting for gains through annual photosynthesis and deposition and losses from erosion under different lulc scenarios to fulfill our objectives we combined geowepp an erosion deposition process model with century 4 0 an ecosystem model used for simulating soc our results show that between 11 and 31 of the eroded soil gets deposited in the same basin depending on the lulc type leaving the remainder to be transported downstream additionally as expected soc flux due to erosion and deposition varies with the type of management practices in the case of conservation management practices the flux associated with erosion and deposition remains below 10 in comparison to in situ soc transformations due to annual photosynthesis however in the case of non conservation management practices this proportion rises above 50

super deep reflection profiling exploring the continental mantle lid abstract reflections from the continental mantle lithosphere have now been reported from common mid point cmp profiles at numerous sites around the world these reflections include 1 distinct dipping events that appear to originate in the lower crust and continue some distance into the upper mantle 2 kilometer scale discontinuous diffusely distributed or isolated reflections at varying depths 3 continuous sub horizontal reflections tens of kilometers in extent often interpreted as the base of the lithosphere in spite of a wide variation in depth and 4 very deep reflections in the mantle lithosphere 125 km the first category of mantle reflections is most commonly observed in proximity to crustal sutures lending credence to their interpretation as fossil subduction zones isolated discontinuous mantle reflections are by far the most common and though observed in both ancient and modern collisional environments are difficult to interpret due to both their limited extent and a corresponding lack of three dimensional control sub horizontal mantle reflections appear in disparate tectonic environments in at least nine locations worldwide of special note are the various reports of specific reflections at 80 100 km 22 24 s twt in the north sea eastern europe and the urals which suggest a more ubiquitous mantle horizon the deepest events imaged thus far in a controlled source cmp survey are the super deep mantle reflections of the urseis project that have been identified at 135 165 km 35 43 s and 225 km 56 s of the many reported mantle reflections these are the most likely to be associated with the base of the lithosphere although such an interpretation averts the question of why an essentially thermo mechanical transition should be reflective at high frequencies 10 20 hz

resolving the holocene alluvial record in southeastern australia using luminescence and radiocarbon techniques a previous assessment of radiocarbon 14 c dates from alluvial units in southeastern australia revealed a gap in the geochronological record that coincides with the holocene climatic optimum thisgapin the alluvial recordcanbe further refined usingoptically stimulatedluminescence osl the chronology of holocene river terraces on widden brook a sandy alluvial stream in southeastern australia was established using 14 c and osl techniques combined use of these independent techniques allows for a more rigorous assessment of the alluvial record the robust chronology consisting of 38 14 c and 11 osl samples permitted identification of significant deposi tionalvariationwithin thecatchment resulting fromlocalisedgeomorphicprocesses thethree terrace sequences identified yielded distinct chronologies suggesting alluvial deposition at different times the sequences exhibited a continuous chronology which indicated continuous deposition throughout the holocene the chronology of terrace sequences within this catchment suggests that terrace formation can be attributed to localised geomorphic processes rather than climatic forcing copyright 2010 john wiley sons ltd supporting information can be found in the online version of this article

correlation of lg amplitude ratios from peaceful nuclear explosions to crustal structure in northern eurasia because the lg phase is strongly affected by the variations of crustal structure in some areas understanding these factors is important for nuclear test monitoring this study examines the effects of regional tectonic structure on lg propagation by using the peaceful nuclear explosion pne profiles in russia the logarithms of lg sn and lg pcoda pne amplitude ratios within the 0 5 to 3 hz frequency band are measured and correlated with the regional crustal structures both ratios are found to decrease within the areas with thick low velocity sedimentary cover and across tectonic boundaries with abrupt variations of crustal thickness for the offset derivatives of both the logarithmic ratios a linear relationship to the slopes of the moho and the vertical travel times within the sedimentary cover is determined a strong negative slope is observed along both crustal thinning and crustal thickening segments and a positive slope follows the negative slope across a crustal thickening segment therefore crustal thinning appears to affect the lg propagation stronger than crustal thickening which could be due to focusing lg energy within the crustal wave guide the log amplitude regression provided in this article could be useful for predicting lg behavior in areas where amplitude measurements are not available

stream response to quaternary climate change evidence from the shoalhaven river catchment southeastern highlands temperate australia abstract luminescence ages from a flight of four paired alluvial terraces in the upper catchment of the shoalhaven river southeast highlands australia provide a record of stream behaviour throughout the late quaternary ages ranging from 7 ka in the modern floodplain to nearly 500 ka for the uppermost dated terrace allow comparisons to be made of the response of streams throughout southeastern australian to late quaternary climatic perturbations the alluvial record of the shoalhaven river highlights the broad regional synchronicity of episodes of heightened fluvial activity during oxygen isotope stage ois 5 terminating 75 ka 60 40 30 25 and 20 15 ka the shoalhaven record also shows an absence of fluvial activity during the last glacial maximum suggesting that southeastern australia was most likely dry at this time as compared to northern australia which was probably wet fluvial activity while still significant decreased substantially after approximately 60 ka suggesting a general drying of climate towards the present

butzer down under debates on anthropogenic erosion in early colonial australia abstract the arrival of europeans in the new world and the rapid deforestation for agriculture and settlement that shortly followed resulted in large and rapid increases in soil erosion and sediment aggradation in australia as in parts of north america and other new world sites this event dates to the last several centuries of the common era a period for which we have surprisingly little historical or scientific data capable of informing debates on the impact of european colonisation on soils and erosion these research themes and debates were central to the work of karl butzer who undertook field and archival research in australia to test existing ideas of the timing and magnitude of landscape response to colonisation in this paper the work and impact of butzer in australia is reviewed as part of ongoing scholarship on the impact of colonisation on landscapes to which butzer contributed butzer and helgren 2005 geomorphic records of soil erosion and historical accounts of land use and impact from eastern australia show that european settlement land clearing and agriculture resulted in rapid and often severe increases in erosion in the late eighteenth and early nineteenth centuries mirroring the experience of anthropogenic soil loss experienced in other parts of the world it is postulated that the geomorphic response to european settlement in australia is more complex than researchers have previously noted that in some contexts continues to influence catchment processes decades and centuries after colonisation

rapid assessment of gully sidewall erosion rates in data poor catchments a case study in australia knowledge of erosion rates and sediment yields from gullies is critical for the effective prioritisation of management efforts aimed at reducing the impact of gully derived sediments on water quality this paper describes a rapid assessment method for estimating sidewall gully erosion rates for already established gully networks it combines a conceptual empirical model of the cycle of gully initiation and stabilisation with an easy to apply technique for assessing gully extent and dimensions the method is illustrated using a case study of the avon richardson catchment of north central victoria australia it is estimated that a total of 4 6 106tonnes of sediment have been generated in that catchment from gully erosion since the latest major phase of gullying in the mid 1800s this is equivalent to 8 9tha 1y 1 if sediment generation was evenly distributed spatially and temporally across the 3300km2 catchment over 160years prior to 2010 current rates of gully erosion are estimated to be 4700ty 1 equivalent to 1 4tha 1y 1 the results are comparable with observed rates of sidewall erosion in the avon richardson catchment further testing is required to build confidence in its applicability to assess sediment yields and for assisting regional authorities to plan remediation efforts

cenozoic landscape development in the blue mountains se australia lithological and tectonic controls on rifted margin morphology abstract cenozoic landscape development on the southeastern australian rifted margin as recorded by mid tertiary basalt flows that preserve ancient landforms is generally considered to be very slow eocene miocene basalts of the southeastern australian highlands flowed down paleovalleys indicating that landscape dissection was already well under way at the time of their eruption within the deeply incised blue mountains however miocene basalts cap relatively flat hilltops suggesting that most incision postdates their emplacement we have studied the controls on these apparent lateral variations in cenozoic landscape development using both field observations and numerical models we have mapped the blue mountains basalts in detail to reconstruct the miocene landscape and to quantify both the amount of subbasalt relief and postbasalt incision rates new geochemical and k ar geochronological data indicate that most of the blue mountains basalts were derived from a common magma source and were erupted i

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

the holocene evolution and geomorphology of a chain of ponds southeast australia establishing a physical template for river management abstract chains of ponds are a discontinuous river type found in australia their unusual morphology important ecological functions and increasing rarity make them a priority for conservation and yet very little research has investigated their physical structure behaviour and evolution this paper reconstructs the holocene evolution and environmental history of crisp s creek a headwater chain of ponds in the southern tablelands of nsw australia this history establishes baseline information on the physical template that can be used to assess a range of other biophysical processes and design appropriate river rehabilitation and management strategies for these rivers sedimentary aggradation began in the late holocene at least 3 7 1 3 ka broadly synchronous with aggradation phases at other sites in southeast australia since european arrival in the nineteenth century parts of the river incised destroying intact ponds and smothering formerly swampy floodplains with post incision alluvium however sections unaffected by incision provide a rare opportunity to examine the evolutionary trajectory of an intact variant of these rivers this research deepens our understanding of the evolutionary context for contemporary river behaviour as relevant for designing appropriate and effective conservation and rehabilitation strategies for chains of ponds

changes in the rates of floodplain and in channel bench accretion in response to catchment disturbance central queensland australia analysis of the changes in rates of catchment sediment storage can provide material evidence of the impact of landscape disturbance on catchment sediment flux a number of studies have suggested increased sediment yields from the rivers draining to the great barrier reef since european settlement in the mid nineteenth century many of these predictions which indicate increases between four to ten times the pre disturbance estimates are based on large scale catchment modelling that make some critical assumptions about pre disturbance erosion rates and or sediment delivery ratios in addition the majority have not been validated by empirical data this study uses single grain osl dating and 137cs depth profiles to determine pre and post floodplain accretion rates in theresa creek a subcatchment of the dry tropical fitzroy river basin we demonstrate that floodplain accretion rates have increased by three to four times since european settlement ca a d 1850 decreased rates of floodplain accretion since the mid twentieth century at sites contributed to by gullied terrain suggest a decrease in the supply of sediment derived from gully networks in contrast floodplain accretion rates from areas dominated by cultivation remain high widespread in channel benches deposited since european settlement are stable and appear to be important stores of large volumes of sediment low magnitude increases in post disturbance floodplain sedimentation rates 3 to 4 times in comparison to those reported from mainly temperate climates 10 to 100 times are attributed to the naturally high sediment loads typical of dry tropical catchments consequently previous predictions of large post disturbance increases in sediment yields from large dry tropical catchments draining to the great barrier reef are likely to be overestimates

timing of post european settlement alluvium deposition in se australia a legacy of european land use in the goulburn plains the timing of landscape change post settlement alluvium psa deposition and gully erosion in the southeastern australian tablelands remains at the centre of a long standing discussion over the geomorphological effects of european land use compared with aboriginal land use and climate change few quantitative studies date the onset of gully erosion and subsequent psa deposition in the tablelands and those that do determine the timing of landscape change for individual catchments rather than across the region in this study we present optically stimulated luminescence osl burial ages of swampy meadow sm sediment and psa from six sites spread throughout the goulburn plains to place better regional constraints on the timing of landscape change psa burial ages at each of our sample sites range between 213 and 81 years before ad 2013 the year during which all samples were collected and measured corresponding to ad 1800 1932 all measured psa burial ages post date european arrival to australia and are

upper mantle velocity structure beneath the siberian platform summary we present a new velocity model for the continental upper mantle beneath central siberia based on observations of the 1982 rift deep seismic sounding dss profile three peaceful nuclear explosions pne were detonated to provide energy for the 2600 km long profile that extends from the yamal peninsula to the mongolian border se of lake baikal in this paper we model seismic recordings from the northernmost explosion since data from that shot shows unambiguous arrivals from the mantle transition zone discontinuities the analysis combines forward traveltime modelling and waveform matching using reflectivity synthetic seismograms our model for the lithosphere has velocities of 8 25 8 20 km s from the moho to 117km depth between 117 and 123km depth a strong velocity gradient 8 30 8 53 km s is required while a moderate gradient 8 53 8 55 km s l exists between 123 and 136km depth a low velocity zone from 136 to 210km depth terminates this phase arrival branch the gradient again rises between 210 and 233 km and depth culminating in a high gradient zone 8 63 8 80 km s between 233 and 235 km depth below the high gradient zone more moderate gradient 8 80 8 85 km s is required from 235 to 253 km depth terminating in a zone of lower velocity 8 62 8 64 km s from 253 to 400 km depth the upper mantle transition zone consists of two high gradient zones separated by a more moderate gradient the upper zone is best modelled as a 35 km thick velocity gradient 8 64 9 45 km s from 400 to 435 km depth the existence of the velocity gradient is based on the observation that arrivals from this feature can be identified starting at 1580 km range and rapidly become prominent with increasing distance a model with a first order discontinuity predicts significant arrivals at ranges closer than 1580 km our observations contain no compelling evidence for a 520 km discontinuity although a small discontinuity cannot be ruled out the lower transitionzone discontinuity is modelled as a 4 km thick gradient zone 10 25 10 62 km s i from 655 to 659 km depth

predicting the topographic limits to a gully network using a digital terrain model and process thresholds a digital terrain model is used with process thresholds to predict the extent of a stable gully network in a 5 km2 catchment of the southeastern highlands of australia the model developed by dietnch et al 1992 1993 predicts the topographic controls on channel networks and interprets these in terms of a critical shear stress for channel incision c applied by saturation overland flow we adapt the model slightly to compare the shear stress applied by hortonian overland flow to that applied by saturation overland flow the limits to gully erosion in the catchment are controlled strongly by a topographic threshold that has an inverse relationship between upslope catchment area and local gradient the topographic threshold for channel incision is reproduced using a simple model of hortonian overland flow and a c appropriate for incision into a degraded grass surface c 245 dyn cm2 this is consistent with historical evidence for the timing of gully erosion the study confirms a strong topographic control on the extent of the channel network in a catchment significantly different from the western north america catchments where the topographic threshold was first demonstrated despite its simplicity the model for incision by overland flow appears capable of distinguishing the hydrological processes responsible for channel incision when these are reflected in the relationship between channel network and landscape morphology the model requires relatively simple inputs suggesting it may be useful for mapping gully erosion hazard in actively eroding catchments

using osl to assess hypotheses related to the impacts of land use change with the early nineteenth century arrival of europeans in south eastern australia an exploratory case study from grabben gullen creek new south wales a common explanation for intense soil erosion and gullying in se australia is the introduction by europeans of new land use practices following their arrival in australia in the late 18th century eucalyptus woodlands were cleared to introduce farming and valley bottoms characterized by chains of ponds with organic rich swampy meadow sm soils were subsequently buried by thick deposits of post settlement alluvium psa generated by erosion in the catchment in this study optically stimulated luminescence osl is used to evaluate the source s of the psa in grabben gullen creek ggc australia we use a portable osl reader to measure total photon counts on bulk polymineral and polygrain size samples from nine profiles along the creek we use these luminescence signals as geotracers of sediment source s and transport pathways we obtained higher luminescence signals in the psa than in the sm sediments suggesting different sources and fluvial transport conditions for these two widespread sedimentary units portable osl reader data from soils in the ggc catchment that are potential sources for the sm sediments and psa show that the high luminescence signals recorded in the psa are similar to those from subsoil samples in granite soils suggesting that the psa was derived by gullying of granite subsoils in the sm sediments luminescence signals decrease upwards from the base of the profile as expected in well reset fluvial deposits but with one or more changes in gradient in the profile of photon counts with depth most likely indicating changes in sediment deposition rates to calculate deposition rates in the sm sediments several samples were dated using osl the osl ages produced low scatter in the equivalent doses confirming the well reset nature of the grains composing the sm and indicating a process of sediment transport in dilute flows as is interpreted from the portable osl signals this article is protected by copyright all rights reserved

impact of historic land use change on sediment delivery to a chesapeake bay subestuarine delta historic land use in the chesapeake bay drainage basin induced large fluxes of fluvial sediment to subestuarine tributaries stratigraphic and palaeoecologic analyses of deltaic deposits may be used to infer changes on the landscape but are not sufficient to quantify past sediment supply when viewed as an inverse boundary value problem reconstruction of the sediment supply function may be achieved by combining deltaic sedimentation chronologies with an equation governing delta progradation we propose that the diffusion equation is appropriate for simulating delta progradation and obtaining the sediment supply function provided a suitable diffusion constant d can be determined three new methods for estimating d are presented for the case of estuarine deltas when the inverse boundary value technique was applied to otter point creek a tidal freshwater delta at the head of bush river in upper chesapeake bay d values ranged from 3763 to 6199 m2 a 1 delta growth simulations showed a 1740 1760 initial pulse a 1760 1780 erosive redistributive interval a 1780 1920 growth period and a 1920 present erosive redistributive era coupling of simulated delta elevations with an empirical plant habitat predictive equation allowed for comparison of predicted versus actual relative habitat areas also the model yielded reconstructed watershed erosion rates and stream suspended sediment concentrations that could be useful for development of water quality regulations copyright 2001 john wiley sons ltd

holocene valley aggradation driven by river mouth progradation examples from australia since the end of the post glacial sea level rise 6800 years ago progradation of river mouths into estuaries has been a global phenomenon the responses of upstream alluvial river reaches to this progradation have received little attention here the links between river mouth progradation and holocene valley aggradation are examined for the macdonald and tuross rivers in south eastern australia optical and radiocarbon dating of floodplain sediments indicates that since the mid holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary this link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits both rivers have abandoned their main holocene floodplains over the last 2000 years and their channels have contracted a regional shift to smaller floods is inferred to be responsible for this change though a greater relative sea level fall experienced by the macdonald river since the mid holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley copyright 2006 john wiley sons ltd

the history of human induced soil erosion geomorphic legacies early descriptions and research and the development of soil conservation a global synopsis abstract this paper presents a global synopsis about the geomorphic evidence of soil erosion in humid and semihumid areas since the beginning of agriculture historical documents starting from ancient records to data from the mid twentieth century and numerous literature reviews form an extensive assortment of examples that show how soil erosion has been perceived previously by scholars land surveyors farmers land owners researchers and policy makers examples have been selected from ancient greek and roman times and from central europe southern africa north america the chinese loess plateau australia new zealand and easter island furthermore a comprehensive collection on the development of soil erosion research and soil conservation has been provided with a particular focus on germany and the usa geomorphic evidence shows that most of the agriculturally used slopes in the old and new worlds had already been affected by soil erosion in earlier prehistoric times early descriptions of soil erosion are often very vague with regard to the roman times geomorphic evidence shows seemingly opposing results ranging from massive devastation to landscapes remaining stable for centuries unfortunately historical documentation is lacking in the following centuries historical records become more frequent and more precise and observations on extreme soil erosion events are prominent sometimes they can be clearly linked to geomorphic evidence in the field the advent of professional soil conservation took place in the late eighteenth century the first extensive essay on soil conservation known to the western world was published in germany in 1815 the rise of professional soil conservation occurred in the late nineteenth and early twentieth centuries soil remediation and flood prevention programs were initiated but the long term success of these actions remains controversial in recent years increasing interest is to recover any traditional knowledge of soil management in order to incorporate it into modern soil conservation strategies the study shows that local and regional variations in natural settings cultural traditions and socioeconomic conditions played a major role for the dynamics and the rates of soil erosion on a long term perspective geomorphic evidence and historical sources can often complement each other but there should be also an awareness of new pitfalls when using them together

fluvial responses to land use changes and climatic variations within the drury creek watershed southern illinois abstract fluvial responses to climatic variation and anglo american settlement were documented for the drury creek watershed southern illinois by examining stratigraphic geomorphic climatic and historical data regional analyses of long term precipitation records document a period of decreasing mean annual precipitation from 1904 to about 1945 and an increasing trend in annual precipitation from 1952 to the present the period between 1945 and 1951 experienced a large number of intense storms that resulted in high annual precipitation totals statistical relationships illustrate that changes in precipitation totals are transferred to the hydrologic system as fluctuations in stream discharge historical records of southern illinois show that a maximum period of settlement and deforestation occurred between the 1860s and 1920s this era ended in the 1940s when large tracts of land were revegetated in an attempt to curtail erosion which had caused extensive upland degradation in response to hillslope erosion at least two meters of fine grained sediments were deposited on valley floors average sedimentation rates determined using decdrochronologic techniques are estimated to be 2 11 cm yr for the period between 1890 and 1988 rates that are 1 to 2 orders of magnitude greater than pre settlement values calculated for other areas of the midwest however botanical data suggest that aggradation was episodic possibly occurring during three periods characterized by greater annual precipitation since the 1940s sedimentation rates have declined reduced rates of sedimentation are related to an episode of channel entrenchment that reduced overbank flooding entrenchment coincided with a period of 1 reduced sediment yields associated with watershed revegetation and the introduction of soil conservation practices and 2 intense storm activity that resulted in long periods of high discharge as a result of channel incision and hillslope erosion newly exposed bedrock in upstream areas currently provides a source of gravel load to the channels the distribution of coarse bedload material along tributary streams combined with downstream decreases in width depth ratios and tractive force estimates suggest that channels in the drury creek watershed are slowly adjusting their configuration to transport coarse bedload material the fluvial response to the increased influx of coarse sediment began more than 45 years ago and continues today

velocity structure of upper mantle transition zones beneath central eurasia from seismic inversion using genetic algorithms summary we present velocity constraints for the upper mantle transition zones beneath central siberia based on observations of the 1982 rift deep seismic sounding dss profile the data consist of seismic recordings of a nuclear explosion in north western siberia along a 2600 km long seismic profile extending from the yamal peninsula to lake baikal we invert seismic data from the mantle transition zones using a non linear inversion scheme using a genetic algorithm for optimization and the wkbj method to compute the synthetic seismograms a statistical error analysis using a graphbinning technique was performed to provide uncertainty values in the velocity models our best model for the upper mantle velocity discontinuity near 410 km depth has a two stage velocity gradient structure with velocities increasing from 8 70 9 25 km s over a depth range of 400 415 km a gradient of 0 0433 s and from 9 25 9 60 km s over a depth range of 415 435 km a gradient of 0 0175 ski this derived model is consistent with other seismological observations and mineral physics models the model for the velocity discontinuity near 660 km depth is simple sharp and includes velocities increasing from 10 15 km s l at 655 km depth to 10 70 km s at 660 km depth a gradient of 0 055 s

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

high velocities in the uppermost mantle of the siberian craton abstract anomalous high seismic velocities up to 8 8 km s have been reported suvorov et al 1985 in the mantle beneath the kimberlite areas of siberia high mantle velocities were also observed on some geon center profiles carried out using nuclear explosions egorkin et al 1987 to obtain clear general signatures of the mantle structure in siberia and the role of the high velocity blocks the geon data were analyzed and compared with other geophysical information this analysis showed that the largest blocks of 300 400 km width with velocities up to 8 6 km s are observed beneath the tunguss depression and in the southern part of the craton near its boundary with the baikal rift zone the blocks penetrate to depths of 100 110 km where they are underlain by low velocity zones or a horizontally homogeneous layer there is no evidence of these blocks in the gravity field velocity anisotropy is proposed as a main cause of the anomalous high velocities although the crossing profiles show that such velocities are observed in different directions the yakutia kimberlite fields are located in the region with average sub moho velocity of 8 3 8 4 km s but with higher velocity at depths of 70 80 km

upper mantle heterogeneity in the northern part of eurasia abstract a two dimensional velocity model of the upper mantle has been compiled from a long range seismic profile crossing the west siberian young plate and the old siberian platform it revealed considerable horizontal and vertical heterogeneity of the mantle a sharp seismic boundary at a depth of 400 km outlines the high velocity gradient transition zone its base lying at a depth of 650 km several layers with different velocities velocity gradients and wave attenuation are distinguished in the upper mantle they likewise differ in their inner structure for instance the uppermost 50 70 km of the mantle are divided into blocks with velocities from 7 9 8 1 to 8 4 8 6 km s 1 comparison of the travel time curves for the siberian long range profile with those compiled from seismological data for europe distinguished large scale upper mantle inhomogeneities of the eurasian continent and allowed for the correlation of tectonic features and geophysical fields the velocity heterogeneity of the uppermost 50 100 km of the mantle correlates with the platform age and heat flow i e the young plates of western europe and western siberia have slightly lower velocities and higher heat flows than the ancient east european and siberian platforms at greater depths 150 250 km the upper mantle velocities increase from the ocean to the inner parts of the continent the structure of the transition zone differs significantly beneath western europe and the other parts of eurasia the sharp boundary at a depth of 400 km traced throughout the whole continent as the boundary reflecting intensive waves transforms beneath western europe into a gradient zone this transition zone feature correlates with positions of the north atlantic west europe geoid and heat flow anomalies

studies of mantle structure of u s s r territory on long range seismic profiles long range seismic sounding carried out during the last few years on the territory of the u s s r has shown a basic inhomogeneity of the uppermost mantle as well as evidence of regularities in the distribution of its seismic parameters the following data were used times and apparent velocities of p and s waves for investigation of mantle velocities converted waves for seismic discontinuity model studies and wave attenuation for q factor estimation strong regularities were distinguished in the distribution of average seismic velocities for the uppermost mantle in their dependence on the age and type of geostructure and on their position relative to the central part of the continent old platforms and the inner part of the continent are marked by velocities under the mohorovicic discontinuity of more than 8 2 8 3 km s 1 young platforms and outer parts of the continent by 8 0 8 2 km s 1 and orogenic and rift zones by 7 8 8 0 km s 1 the difference becomes more pronounced at a depth of about 100 200 km for the old platform mantle velocities of 8 5 8 6 km s 1 are typical beneath the orogenic and rift areas inversion zones with velocities less than 7 8 km s 1 are observed the converted waves show fine inhomogeneities of the crust and uppermost mantle the presence of many discontinuities with positive and negative changes of velocity and anisotropy of seismic waves in some of the layers wave attenuation allowed the determination of the q factor in the mantle it varied from one region to another but a close relation between q and p wave velocity is the main cause of its variation

exchanges of sediment between the flood plain and channel of the amazon river in brazil sediment transport through the brazilian sector of the amazon river valley a distance of 2010 km involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at obidos 1200 mt yr 1 the exchanges occur through bank erosion bar deposition settling from diffuse overbank flow and sedimentation in flood plain channels we estimated the magnitude of these exchanges for each of 10 reaches of the valley and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel the annual supply of sediment entering the channel from bank erosion was estimated to average 1570 mt yr 1 1 3 the obidos flux and the amount transferred from channel transport to the bars 380 mt yr 1 and the flood plain 460 mt yr 1 in channelized flow 1230 mt yr 1 in diffuse overbank flow totaled 2070 mt yr 1 1 7 the obidos flux thus deposition on the bars and flood plain exceeded bank erosion by 500 mt yr 1 over a 10 16 yr period sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 mt yr 1 over 16 yr crudely validating the process based calculations of the sediment budget which in turn illuminate the physical controls on each exchange process another 300 400 mt yr 1 are deposited in a delta plain downstream of obidos the components of the sediment budget reflect hydrologic characteristics of the valley floor and geomorphic characteristics of the channel and flood plain which in turn are influenced by tectonic features of the amazon structural trough

landscape preservation under post european settlement alluvium in the south eastern australian tablelands inferred from portable osl reader data human land use changes leading to widespread erosion and gully incision have been well studied but the effects that erosion and sediment mixing which accompany the deposition of post european settlement alluvium psa have in valley bottoms and wetlands receive considerably less attention psa overlying pre disturbance swampy meadow sm wetland sediments is commonly exposed along incised stream channel gully walls throughout the south eastern australian tablelands providing an ideal setting in which to assess and understand better how psa deposition affects valley bottoms and the wetland environments that often occupy them portable optically stimulated luminescence posl reader data were measured on bulk sediment samples from sm psa stratigraphies at 16 locations throughout the south eastern australian tablelands to assess the effects of erosion and sediment mixing at the sm psa boundary trends of posl data with depth at each profile were used in conjunction with visual profile descriptions to identify the stratigraphic boundary between sm and psa sediment and to infer the degree of valley bottom erosion and sediment mixing during psa deposition at most sites sm sediments experienced minimal if any disturbance during psa deposition and we refer to these as non eroded sites many sites however experienced a significant degree of erosion and sediment mixing eroded sites often corresponding to visually diffuse sedimentary boundaries between the two stratigraphic units our findings demonstrate that sm landscapes in the tablelands can be preserved with minimal disturbance under psa at non eroded sites and are preserved beneath a mixing zone at all eroded sites copyright 2016 john wiley sons ltd

accelerated overbank accumulation after nineteenth century river regulation works a case study on the maros river hungary abstract in the nineteenth century the meandering rivers of the carpathian basin were extensively regulated and their large up to 100 km wide floodplains were confined by artificial levees on the narrow 0 5 4 km artificial floodplains confined by these levees overbank sedimentation has become the dominant geomorphological process resulting in rising floodplain levels during the last century the maros river is an extreme example of this process as it carries a significant amount of suspended sediment 4 6 10 6 m 3 y and because its lowland reach was drastically shortened by cutoffs resulting in bed scour and an increased sediment load simultaneously a flood embankment system was constructed reducing the floodplain width by 70 80 the resulting accelerated overbank sediment accumulation increases the flood hazard along the river the aim of this study is to determine the spatial and temporal pattern of overbank sediment accumulation on the artificial floodplain of the lower maros river over the last 150 years and to identify its influencing factors the lateral slope of the protected natural floodplain was projected towards the present day channel allowing the volume m 3 and rate cm y of overbank sedimentation to be calculated using digital terrain modelling dtm changes in the rate of sedimentation were determined by pollen analysis the studied reach was divided into five sections based on the rate of aggradation i the distal surface of the alluvial fan where no sedimentation was measured only incision ii the original front of the alluvial fan 1 0 0 4 cm y iii the recently formed secondary alluvial fan 1 4 0 3 cm y iv the low lying floodplain 0 4 0 2 cm y and v the outlet unit 2 0 0 5 cm y the aggradation rate was slower on elevated forms such as the pre regulation natural levee 0 2 cm y and greater on the low lying floodplain 0 6 cm y the greatest accumulation rate 1 3 2 4 cm y was measured in cutoffs the sedimentation rate was high during the regulation period 1 9 2 4 cm y but later decreased to 0 5 0 9 cm y the rate of aggradation was determined by the width height and slope conditions of the floodplain the impoundment of the main river and the land use in the area

wetting and drying of australia over the past 300 ka alternately dry and wet climatic episodes across central and eastern australia during the past 300 ka have greatly affected australia9s rivers lakes and dune fields evidence of widespread climate and flow regime changes has been provided by 75 thermoluminescence tl dates and 18 u th dates from alluvial and eolian sediments fluvial conditions dominated part of the last two interglacials stage 5 and 7 resulting in large sand loads in rivers in the present simpson desert and southeastern australia during the last interglacial fluvial activity in central australia peaked at 110 ka stage 5 pluvial probably 5 10 ka behind world temperature and sea level maxima following the last late interglacial wet phase aridity associated with dune building spread from central australia toward its margins achieving greatest intensity during the last glacial maximum a less widespread wet phase identified at about 55 35 ka stage 3 subpluvial is associated with high lake levels and paleochannel activity in southeastern australia this tl record of variable continental aridity in australia correlates well with global changes including the variable eolian dust flux into central china the northern pacific ocean and antarctica

sediment yield from disturbed earth systems changes of sediment yield rates through time reflect evolutionary changes within a landscape when a drainage basin is perturbed significantly by base level climatic or tectonic change sediment yields increase dramatically but with no further disturbance they decline rapidly these sediment yield changes have been documented at all scales from small experimental studies to incised channels to the colorado river basin and to the himalaya mountains thus the shape of the sediment yield curve can be used to estimate future sediment yields and to interpret past tectonic events

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

combining bulk sediment osl and meteoric 10be fingerprinting techniques to identify gully initiation sites and erosion depths deep erosional gullies dissect landscapes around the world existing erosion models focus on predicting where gullies might begin to erode but identifying where existing gullies were initiated and under what conditions is difficult especially when historical records are unavailable here we outline a new approach for fingerprinting alluvium and tracing it back to its source by combining bulk sediment optically stimulated luminescence bulk osl and meteoric 10be 10bem measurements made on gully derived alluvium samples in doing so we identify where gully erosion was initiated and infer the conditions under which such erosion occurred as both 10bem and bulk osl data have distinctive depth profiles in different uneroded and depositional settings we are able to identify the likely incision depths in potential alluvium source areas we demonstrate our technique at birchams creek in the southeastern australian tablelands a well studied and recent example of gully incision that exemplifies a regional landscape transition from unchanneled swampy meadow wetlands to gully incision and subsequent wetland burial by post european settlement alluvium we find that such historic alluvium was derived from a shallow erosion of valley fill upstream of former swampy meadows and was deposited down the center of the valley incision likely followed catchment deforestation and the introduction of livestock which overgrazed and congregated in valley bottoms in the early 20th century during a period of drought as a result severe gully erosion was likely initiated in localized compacted and oversteepened reaches of the valley bottom

exploring the importance of authigenic clay formation in the global li cycle abstract lithium isotopic 7li and elemental concentrations of pore fluids and carbonates from iodp site u1338 hole a eastern equatorial pacific ocean suggest that clay authigenesis i e in situ precipitation is a significant sink for li in carbonate rich sedimentary sections systematic variations in pore fluid 7li with depth in the section suggest that clay authigenesis can i strongly decrease pore fluid li concentrations with depth and ii fractionate li isotopically to a considerable degree 5 21 relative to seawater we hypothesize that clay authigenesis in carbonate rich sections occurs due to the presence of reactive biogenic silica and reactive transport modeling supports the contention that the pore fluid 7li depth profile at site u1338 is best explained by faster authigenesis at depth the significance of clay authigenesis in carbonate rich sediments is two fold if global in scale i it can generate sizeable output fluxes in the global li cycle and ii the evolution of the sedimentary system over time can markedly impact the isotopic composition of the global li output flux we compile odp and iodp pore fluid li data from 267 sites of these 207 have li pore fluid concentration gradients in the upper 50 100 meters that indicate the sites as diffusive sinks of li we then estimate that clay authigenesis in carbonate rich sediments could reasonably generate a li output flux on the order of 1 2 1010 moles year which is comparable to the gross input fluxes in the modern li cycle a series of reactive transport simulations illustrate how clay authigenesis might impact the isotopic composition of the output flux of li from the global ocean the suggestion is that applying a constant fractionation factor from the global ocean over time is likely incorrect and that secular changes in the 7li of the output flux will be driven by rates of authigenesis burial rates and the depth extent of authigenesis in the sedimentary section utilizing a time dependent depositional diagenetic model the 7li values of bulk carbonate are shown to be a consequence not of recrystallization alone but recrystallization in the presence of clay authigenesis further our model results are used to illustrate how carbonate 7li may be used to constrain the temporal evolution of clay authigenesis in the sedimentary section ultimately this work suggests that the li isotopic composition of bulk carbonates can be altered diagenetically however such alteration is not a detriment but provides useful information on those diagenetic processes in the sedimentary column that impact the global li cycle thus li isotopes in bulk carbonates have the potential to elucidate diagenetic controls on the global li cycle over long time scales

spatial patterns of historical overbank sedimentation and floodplain evolution blue river wisconsin abstract increased soil erosion and overbank flooding associated with land use changes following european settlement have buried pre settlement floodplain surfaces in many driftless area watersheds with as much as several meters of alluvium this paper examines the processes influencing spatial variations in the storage of post settlement vertical accretion alluvium and the impact on floodplain evolution in the blue river watershed wisconsin the cross sectional area of historical vertical accretion sediments stored on floodplains was measured at 41 cross valley transects in the 208 km2 watershed the storage of historical overbank sediments is influenced by valley width stream power and the development of meander belts post settlement alluvial storage increases with valley width and decreases with cross sectional stream power in a multivariate regression model valley width and cross sectional stream power explain 67 of the variance in the amount of post settlement alluvium the development of meander belts enlarged channels confined between alluvial terraces by accelerated lateral channel migration influences historical floodplain storage by decreasing the influence of valley width and modifying stream power characteristics for flows greater than bankfull meander belts are located in headwater and mid basin valley reaches where high stream power produces rapid lateral channel migration whereas low gradient channels in downstream valleys lack the power necessary to migrate laterally and develop meander belts meander belts influence the spatial pattern of historical sedimentation by 1 containing large magnitude floods and preventing overbank flow 2 increasing sediment transport capacities 3 initiating the erosion of previously deposited historical sediments 4 reducing the attenuation of flood peaks and 5 increasing the amount of sediment routed downstream to wide low gradient valley bottoms lacking meander belts continued high rates of lateral channel migration will eventually be damped as widening of the meander belt decreases flow depths and stream power

optical dating of holocene dune sands in the ferris dune field wyoming abstract optical dating of late quaternary quartz dune sands from the clear creek portion of ferris dune field wyoming demonstrates the considerable potential of the technique as a chronostratigraphic tool a sequence of radiocarbon dated holocene interdune strata permit optical dating of the intercalated dune sand to be tested the concordance is good the optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at clear creek peaked during two relatively short phases at ca 8500 and 4000 yr b p the dates indicate that aeolian accumulation maxima at least in the clear creek area may not be synchronous with previously defined phases of marked aridity

flood channel morphology of a quiet river the lachlan downstream from cowra southeastern australia abstract detailed geomorphic mapping and sediment analyses of floodplain features were undertaken on a 30 km reach of the lachlan river in southeastern australia the reach is located in the transitional zone between the southern great dividing range and extensive alluvial plains to the west the channel resembles other fine grained low energy alluvial channels it is muddy narrow and deep and meanders irregularly it contains fine grained accreting bench deposits and in places is influenced by inherited fluvial forms both of which indicate long term channel stability by contrast the floodplain exhibits features that have been attributed elsewhere to catastrophic flood flows including elliptical scour scars swirl pits cobble and gravel deposits large chutes and chute bars zones of floodplain stripping flood levees and multiple flood channels sorting and texture of floodplain sediments generally increases with height above the bed although deposits are variable and poorly sorted indications of recent fluvial activity at several levels above the bed are confirmed by aerial photographs dating from 1954 although changes to the channel position have been small the alluvial facies model displays a compound floodplain in which a stable low energy channel is inset within a high energy flood dominated floodplain this interpretation is consistent with streamflow and documentary evidence of recurrent large floods since 1839 which have a return period of

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

alluvial sedimentation rates from southeastern australia indicate post european settlement landscape recovery increased catchment sediment yields are common following the introduction of european style agriculture to relatively undisturbed landscapes catchment erosion rates generally increase immediately after disturbance and then decline over time consequently where a catchment currently sits along this disturbance recovery sequence will strongly influence future catchment sediment yields and river morphology in this study field stratigraphy optical dating and hydraulic modelling are used to investigate changes in catchment sediment yield and storage in the lake burragorang catchment in australia with emphasis placed upon changes occurring since european settlement in a d 1820 on the southern tablelands and the upper cox s river subcatchment a large volume of sediment was liberated by gully erosion early in the post settlement period much of which was deposited at break of slope positions below the catchment s headwaters or stored in alluvial benches adjacent to the channel but within the confines of older holocene alluvium a lack of substantial sediment deposition over the last 20 to 40 years is evidence that catchment sediment yields have strongly declined this is consistent with both reduced erosion rates and re aggradation of the incised gullies that in their erosive phase dominated the catchment s post settlement sediment flux collectively these characteristics indicate the catchment is undergoing a phase of landscape recovery

the role of diagenesis in shaping the geochemistry of the marine carbonate record carbonate sediments and rocks are valuable archives of earth s past whose geochemical compositions inform our understanding of earth s surface evolution yet carbonates are also reactive minerals a

multi scalar controls on channel geometry of headwater streams in new zealand hill country abstract catchment reach and local scale controls upon channel geometry are examined for small headwater streams in adjacent sub catchments with variable land use histories in a typical hill country area of the north island of new zealand although systematic downstream increase in channel cross sectional area is evident in one sub catchment a result of catchment scale controls on geometry including discharge and slope marked local variability in channel geometry in the two other sub catchments reflects non systematic patterns of reach scale controls including the distribution of floodplain pockets and associated bank materials and local scale controls such as bedrock outcrops and wood land use change exerts a primary control upon these relationships for a given catchment area streams in native forest are wider and shallower than streams that flow within pasture or pinus plantations increased hillslope erosion following land clearance has instigated the accumulation of post settlement alluvium psa which has altered the boundary conditions and bank materials within which streams flow significant psa accumulation following native forest clearance in one of the sub catchments has allowed the stream to flow entirely within its own alluvial deposits in this instance catchment scale controls on channel geometry are dominant in contrast local scale controls on channel geometry are more important in the other sub catchments where lesser accumulation of psa reflects differences in land clearance these findings indicate that place based understandings which consider the spatial and historical contexts of landscape settings are required to interpret patterns of channel geometry and to inform river rehabilitation initiatives

timing and causes of gully erosion in the riparian zone of the semi arid tropical victoria river australia management implications abstract gully erosion in the seasonally wet tropics of australia is a major source of sediment in rivers stabilization of gullies to reduce impacts on aquatic ecosystems and water storages is a focus for management however the cause of the gully erosion is poorly understood and so a critical context for soil conservation is missing it is uncertain if they are the result of post european cattle grazing or are they much older and related to non human factors the causes of riparian gully erosion along a reach of the victoria river in the semi arid tropics of australia were investigated using several methods gully complexes were described and characterised by two major components a flood drainage channel fdc and upslope of this an outer erosion feature oef characterised by badlands set within an amphitheatre the oef is likely to be a major source of sediment that appears to be of recent origin a review of historical records combined with optically stimulated luminescence osl dating showed that the fdcs were well established prior to the introduction of domestic stock it also showed that the badlands began to develop about 90 years ago that is about 40 years after the arrival of domestic stock in addition an analysis of aerial photos coupled with an on ground survey and analysis of fallout radionuclides revealed that erosion processes are still active within the gully complexes while the fdcs are natural drainage channels cattle grazing probably triggered the badland formation with the expansion aided by increased rainfall in the past 40 years therefore the oefs are of human origin and protection from grazing of the riparian zone should slow badland erosion and reduce sediment input to the river

the anthropocene is there a geomorphological case the anthropocene as used to describe the interval of recent earth history during which humans have had an overwhelming effect on the earth system is now being formally considered as a possible new geological epoch such a new geological time interval possibly equivalent to the pleistocene epoch requires both theoretical justification as well as empirical evidence preserved within the geological record since the geological record is driven by geomorphological processes that produce terrestrial and near shore stratigraphy geomorphology has to be an integral part of this consideration for this reason the british society for geomorphology bsg has inaugurated a fixed term working group to consider this issue and advise the society on how geomorphologists can engage with debates over the anthropocene this esex commentary sets out the initial case for the formalisation of the anthropocene and a priori considerations in the hope that it will stimulate debate amongst and involvement by the geomorphological community in what is a crucial issue for the discipline the working group is now considering the practical aspects of such a formalization including the relative magnitude problem the boundary problem and the spatial diachrony of anthropogenic geomorphology copyright 2013 john wiley sons ltd

age distribution and significance within a sediment budget of in channel depositional surfaces in the normanby river queensland australia we present the results of investigations into alluvial deposition in the catchment of the normanby river which flows into princess charlotte bay pcb in the northern part of the great barrier reef lagoon our focus is on the fine fraction 63 m of alluvial deposits that sit above the sand and gravel bars of the channel floor but below the expansive flat surface generally referred to as the floodplain variously described as benches bank attached bars or inset or inner floodplains these more or less flat lying surfaces within the macro channel have hitherto received little attention in sediment budgeting models we use high resolution lidar based mapping combined with optical dating of exposures cut into these in channel deposits to compare their aggradation rates with those found in other depositional zones in the catchment namely the floodplain and coastal plain in total 59 single grain osl dates were produced across 21 stratigraphic profiles at 14 sites distributed though the 24 226 km2 catchment in channel storage in these inset features is a significant component of the contemporary fine sediment budget i e recent decades last century annually equivalent to more than 50 of the volume entering the channel network from hillslopes and subsoil sources therefore at the very least in channel storage of fine material needs to be incorporated into sediment budgeting exercises furthermore deposition within the channel has occurred in multiple locations coincident in time with accelerated sediment production following european settlement generally this has occurred on a subset of the features we have examined here namely linear bench features low in the channel this suggests that accelerated aggradation on in channel depositional surfaces has been in part a response to accelerated erosion within the catchment the entire contribution of 370 kilotonnes per annum of fine sediment estimated to have been produced by alluvial gully erosion over the last 100 years can be accounted for by that stored as in channel alluvium these features therefore can play an important role in mitigating the impact on the receiving water of accelerated erosion

confirming geomorphological interpretations based on portable osl reader data portable optically stimulated luminescence osl readers are increasingly being used in geomorphological and archaeological investigations but information regarding data reproducibility and the reliability of interpretations based on portable osl reader data has not yet been presented to the wider geomorphological community this letter addresses these two issues by returning to grabben gullen creek in the southeastern australian tablelands where we remeasure a sediment profile that was first measured by other researchers 3 years earlier we also compare portable osl reader data measured on sediment interpreted to have been deposited in swampy meadow wetlands and flood alluvium settings with data measured on known swampy meadow and flood deposits our data show that portable osl reader data are reproducible moreover we confirm the earlier interpretation that stratigraphies commonly exposed in southeastern australian tablelands valley bottoms reflect pre european swampy meadow wetlands and flood alluvium copyright 2015 john wiley sons ltd

wetland and terrestrial vegetation change since european settlement on the fleurieu peninsula south australia microfossil sediment and documentary records provide a history of european land use and its impact on the vegetation of the fleurieu peninsula south australia two sedimentary cores were analysed for their fossil pollen and charcoal composition chronologies were established using a combination of 210pb 14c and microfossil markers primary and secondary evidence for the spatial expansion of land uses in the region were compiled providing local bioregional and regional scaled european settlement histories the settlement and land use histories of the major vegetation types in the region were different and were closely determined by the nature of the vegetation itself the sedimentary and microfossil records indicate that wetland and terrestrial vegetation have undergone sequential changes of composition there is evidence of a decline in fire sensitive understorey species and the decline is likely due to intensive firing and grazing of scleropyllous woodlands and forests early in european settlement

chronology of murrumbidgee river palaeochannels on the riverine plain southeastern australia four major periods of palaeochannel activity have been identified on the murrumbidgee sector of the riverine plain of southeastern australia on the basis of stratigraphic information the channels reveal a picture of changing flow conditions during the last full glacial cycle the ages of the periods were determined from nearly 40 thermoluminescence dates on surficial fluvial and aeolian sediments these are named the coleambally phase which occurred from 105 to 80 ka the mid to latter part of oxygen isotope stage 5 the kerarbury phase from 55 to 35 ka stage 3 the gum creek phase from 35 to 25 ka late stage 3 to early stage 2 and the yanco phase from 20 to 13 ka late stage 2 the present flow regime was established by about 12 ka stage 1 the first two phases correlate with episodes of enhanced fluvial activity in northern and central australia and with reduced dust activity globally the phases in stage 2 appear to be associated with seasonal snow melt and increased peak flows in periods flanking the last glacial maximum source bordering aeolian dunes associated with the coleambally kerarbury and yanco phases were found however the tl dates show that some have undergone aeolian reworking thermoluminescence dating and fluvial stratigraphy have revealed a detailed picture of late quaternary climate and flow regime changes that has the potential to extend to identified deposits stratigraphically older than those described here