tributary trunk stream relations in a cut and fill landscape a case study from wolumla catchment new south wales australia at the time of european settlement of the south coast of new south wales australia in the mid nineteenth century river courses were discontinuous throughout wolumla catchment within a few decades of settlement intact valley fills had been transformed into incised channels along trunk streams this induced associated patterns of secondary incision into tributary valley fills three of the primary subcatchments in wolumla catchment became fully incised while an upland swamp and a floodout i e sand sheet deposits atop an intact valley floor remain in mid catchment of the fourth subcatchment of the 70 lower order tributaries which join the trunk streams in the four subcatchments 27 have incised 12 of which are discontinuously incised incision of tributary streams in wolumla catchment cannot be explained by subcatchment area and slope relations the position of the trunk stream channel within the valley floor trough is the key determinant of whether or not tributary streams have incised changes to river morphology since european settlement have altered the linkage of tributary streams to the trunk stream impacting directly on the within catchment transfer of water and sediment

unraveling paraglacial activity on sierra de gredos central spain a study based on geomorphic markers stratigraphy and osl abstract we study the paraglacial activity in gredos gorge a glaciated valley of sierra de gredos central spain using geomorphic markers stratigraphy and an approach based on osl we use luminescence signals from debris flow and fluvial deposits as well as osl dating of three deposits to detect the main paraglacial processes in gredos gorge we identify two major phases of paraglacial activity during and after the retreat of last glacial maximum lgm glaciers the first phase consisted of high discharge debris flows sourced up valley triggered during the deglaciation the second phase started 11 ka and is characterized by two processes 1 the triggering of low discharge debris flows sourced on the flanks of moraines and 2 the reworking of paraglacial deposits by rivers our results of osl signals stratigraphy markers and sediment volume indicate that during and after the deglaciation of gredos gorge paraglacial sediment was depleted as theory predicts however glacigenic sediments have not been transferred to sediment sinks as long as 70 of glacial deposits are still stored in the valley the transition of the environmental conditions prevailing during the lgm to current mediterranean climate seems to play an important role in delaying the exhaustion model of glacially conditioned sediment release we propose that the poor coverage of vegetation driven by the mediterranean climate prevents the stabilization of glacigenic sediment that is only mobilized during high discharge events responding to extreme rainfalls

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

interpreting luminescence data from a portable osl reader three case studies in fluvial settings optically stimulated luminescence osl is a technique that has been applied from the mid 1980s mainly for sediment dating the osl technique is based on sample stimulation by light to determine the luminescence signal that is stored in the crystal lattices of sediment grains after deposition burial by later sediment and subsequent exposure to ionizing radiation from radioactive elements in the surrounding sediment in such sediment dating two parameters are required the equivalent dose i e the luminescence signal stored in the grains and the dose rate i e the ionizing energy from and radiation emitted by naturally occurring radioisotopes in the deposit plus the effects of cosmic radiation in this research the osl technique is not used for dating the study goal is to analyse only the luminescence signals the total photon counts in polymineral samples obtained after light stimulation in the blue blsl and infrared irsl wavelengths using a portable osl reader designed and built at the scottish universities environmental research centre suerc three fluvial case studies from cambodia australia and mexico are used to illustrate the geomorphological interpretations possible with the portable osl reader data from sediments resulting from a range of different depositional processes the case studies show that aspects of sediment s transport and depositional processes can be inferred from the portable osl reader data providing valuable insights into geomorphological history copyright 2010 john wiley sons ltd

recent landscape history in arid western new south wales australia a model for regional change accelerated erosion by wind and water has taken place in arid western new south wales australia since the introduction of domestic and feral herbivores by europeans in the nineteenth century this action led to widespread soil loss by sheetwash rilling gullying and aeolian deflation upland creek systems formerly comprising shallow sinuous channels are now entrenched into alluvial fills on the valley floor radiocarbon dating of charcoal from aboriginal cooking pits exposed by this erosion indicates that the current phase of incision of the valley floor has occurred since grazing of domestic animals began about 140 years ago stratigraphic evidence is presented which suggests that this type of incision gullying or arroyo cutting in the valley floor may not have occurred before within the 20 000 year sedimentary history of the valley fills studied channel enlargement and knickpoint retreat initiated by these changes is ongoing and the implications of this for land and heritage management in the region are discussed a conceptual model is presented which summarises the hydrogeomorphic changes which have occurred in upland catchments in the region as a result of changes in landcover

seventeenth canadian geotechnical colloquium the effect of cohesion loss and stress path on brittle rock strength stress strain curves for brittle rocks show three characteristic stress levels crack initiation long term strength and peak strength damage controlled testing at low confining stresses has shown that the long term and peak strengths are sensitive to the amount of induced damage i e the greater the amount of damage the lower the long term and peak strengths these tests also showed that the brittle failure process is characterized by a loss of cohesion as friction is mobilized excavation of a circular test tunnel in massive brittle rock resulted in failure around the tunnel the back calculated strength for the failed rock around the tunnel is approximately one half of that measured in laboratory tests crack induced damage of lac du bonnet granite both in the laboratory and in situ begins when the load exceeds approximately one third of the unconfined compressive strength however the stress level associated with failure is a function of loading path in the laboratory where the loading path monotonically increases the ultimate strength of an unconfined sample is 225 mpa numerical studies suggest that in situ the loading path around the tunnel is more complex involving stress increase and decrease and stress rotation for this loading path failure initiates at a stress between 100 and 120 mpa conventional frictional failure criteria did not adequately predict the extent of brittle failure measured around the circular tunnel the results from the damage controlled laboratory tests and the microseismic monitoring carried out during tunnel construction indicate a constant deviatoric stress criterion is a reliable indicator for predicting the onset of damage this criterion was also found to give a reasonable prediction for the maximum depth of failure around the test tunnel the fundamental assumption in the constant deviatoric stress criterion is that at low confining stresses such as those which occur around underground openings the brittle failure process is dominated by cohesion loss

optically stimulated luminescence dating of sediments over the past 200 000 years optical dating of sediment using optically stimulated luminescence has become important for studying earth surface processes and this technique continues to develop rapidly a group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure the technique is well suited to the dating of deposits as young as one year to several hundred thousand years recent technical developments have established a dating protocol with improved precision a high degree of reliability and an in built means to detect incomplete signal removal during deposition this approach has been extended to age estimation for single grains opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement ongoing research offers the possibility of significant age range extension and novel applications including low t

identifying rock slope failure precursors using lidar for transportation corridor hazard management abstract in the thompson and fraser river valleys rockfall and rockslides are a hazard for railway traffic in the region in june 2013 a 2600 m 3 rockslide occurred in the white canyon causing damage to infrastructure and interruption to service in the year preceding this failure the slope was monitored using terrestrial light detection and ranging lidar as part of the railway ground hazards research program initiative the purpose of this study is to evaluate a hazard management strategy for transportation corridors exposed to steep slopes involving the identification of rockfall precursors prior to significant slope failures for this failure deformation was observed in the seven months preceding collapse with an accelerating period occurring in the final 28 days a distinct pattern of smaller rockfalls was observed around the perimeter of the deforming rock block as well as loss of surficial material over the slides tension crack this study shows that with lidar monitoring precursors to rock slope failures can be identified allowing for better rock slope hazard management by focusing attention on areas with the highest probability of failure

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

analysis of acoustic emission patterns for monitoring of rock slope deformation mechanisms acoustic emission ae is generated in soil and rock materials by rearrangement of particles during displacement or increasing damage in the microstructure preceding a collapse therefore ae is appropriate for estimation of slope degradation to overcome the high attenuation that characterise geological materials and thus to be able to monitor ae activity a system that makes use of a waveguide to transmit ae waves from a deforming zone to a piezoelectric transducer was developed the system quantifies acoustic activity as ring down count rdc rates in soil applications rdc rates have been correlated with the rate of deformation whereas the recent application to rock slopes requires new interpretation strategies in order to develop new strategies the system was installed at two rock slope trial sites in italy and austria rdc rates from these sites which have been measured over 5 and 1 5 years respectively are analysed and clear and recurring trends are identified the comparison of ae trends with response from a series of traditional instruments available at the sites allows correlation with changes in external slope loading and internal stress changes ae signatures from the large rock slope in italy have been identified as generated in response to variations in the groundwater level and snow loading at the slope in austria ae signatures include the detachment of small boulders from the slope surface caused by the succession of freeze thaw cycles during winter time the work reported in this paper is contributing to the development of ae monitoring and interpretation strategies for rock slopes the longer term aim is to identify approaching failures and derive rules for setting thresholds that can be used to give warning of rock slope failures in time to enable action to be taken

gully formation and the role of valley floor vegetation southeastern australia attempts to understand the causes of gully erosion have been hampered by a poor understanding of quantitative changes to the force of flows and the resistance to scour we used flume experiments on an unincised valley floor to determine flow resistance and the critical shear stress for scour under natural and degraded vegetation covers applying the results to sites of gully formation in southeastern australia demonstrates the crucial role that reduced vegetation cover plays in increasing the susceptibility of valleys to channel incision widespread and rapid gully formation in the 19th century required degradation of valley floor vegetation and was not solely the result of land use or climatically induced increases in discharge

using meteoric 10be to track fluvial sand through the waipaoa river basin new zealand we use meteoric 10 be measured in 24 fluvial sand samples collected along the mainstem and from prominent tributaries within the tectonically active waipaoa river basin new zealand to identify sediment sources and monitor the mixing of sediment as it travels from headwater basins to the sea deforestation for agriculture beginning in the early 1900s resulted in severe but nonuniformly distributed erosion tributaries in the northern headwaters where large amphitheater gullies that continually feed prodigious amounts of deeply sourced sediment to the mainstem are prevalent yield exceptionally low concentrations of meteoric 10 be 1 5 10 6 atoms g 1 in the more stable eastern and western tributaries concentrations of meteoric 10 be are nearly an order of magnitude greater 14 10 6 atoms g 1 meteoric 10 be concentrations in samples collected along the mainstem above and below tributary confluences steadily and regularly increase downstream r 2 0 92 as large amounts of low concentration gully derived sediments are augmented with higher concentration sediment from more stable tributaries providing strong evidence that meteoric 10 be concentrations reflect sediment sourcing in this fluvial network a two component mixing model indicates that the gullied northern region of the waipaoa basin produces sediment at a rate 20 times that of the eastern and western regions these results suggest that meteoric 10 be in contrast to the widely applied in situ technique that is limited by the availability and distribution of quartz is an effective tool for the rapid assessment of sediment dynamics and movement within a wide range of fluvial networks

aggradation and incision since the very late pleistocene in the naas river south eastern australia past phases of aggradation and incision have been studied along a 10 km reach in the naas valley in south eastern australia detailed mapping of the stratigraphy and an ambitious dating exercise involving 23 optical dates have been used to distinguish the different periods of aggradation and incision the dated alluvial sequence shows that a period of aggradation occurred in the very late pleistocene ca 14 000 12 000 years ago alluvial deposits are absent for the period 12 000 3300 years ago whether this truly reflects no deposition or a series of aggradation and erosion cycles remains unresolved aggradation dominated between 3300 and 900 years ago punctuated by a short incision event around 1300 years ago gully erosion contemporaneous with this incision phase is also recorded incision has dominated during the last 900 years cutting down to bedrock this incision which is still ongoing has not been a continuous process but involved short periods of aggradation the exposed bedrock and large boulders display numerous scour holes indicating that bedrock has been exposed and abraided for lengthy periods in the past the aggradation and incision cycles in the late holocene gave rise to three groups of terraces today visible along the study reach possible causes for the different periods of erosion and deposition are discussed in the context of late pleistocene and holocene climate change land use impacts and intrinsic factors

paleoenvironmental changes during the last 4000 yr in the tigray northern ethiopia in the tigray region at the northern ethiopian highlands paleoenvironmental reconstruction based on several infilled valley deposit sequences suggests that the past 4000 yr comprised three major wetter periods ca 4000 3500 yr b p 2500 1500 yr b p and 1000 960 yr b p during which soils were formed and two degradation episodes ca 3500 2500 yr b p and 1500 1000 yr b p during which there was an increase of sediment yield from the slopes into the valleys for the past 1000 yr and in particular since the early 17th century stratigraphic records together with historic chronicles suggest increasing aridity although difficulties arise in distinguishing between natural and human impacts particularly in a region with a long established agricultural background stratigraphical and proxy paleoclimatic data have indicated climate as the main controlling factor responsible for the environmental changes in the tigray

a review of human and natural changes in maya lowland wetlands over the holocene abstract in the maya lowlands of mexico belize and guatemala two main types of wetlands have played important roles in human history bajos or intermittently wet environments of the upland interior yucatan and perennial wetlands of the coastal plains many of the most important maya sites encircle the bajos though our growing evidence for human wetland interactions is still sparse the deposits of these wetlands record two main eras of slope instability and wetland aggradation the pleistocene holocene transition as rainfall increased and forests eclipsed savannas and the maya preclassic to classic as deforestation land use intensity and drying increased the ancient maya adapted with terraces around these bajo margins but retracted in the late preclassic in some areas the perennial wetlands of the coastal plains have different histories and the first conceptual model of human wetland interaction described intensive wetland agriculture in the preclassic through classic based on raised fields and canals but a second model arose that interpreted the wetland stratigraphy and canals as more indicative of natural aggradation by accelerated erosion and gypsum precipitation that buried archaic and preclassic fields and there was little classic era use we present new data on a third and fourth model in this study the third is a hybrid of the models one and two including the archaic to preclassic aggradation of the second model and the first model s classic period fields and canals as piecemeal attempts by the maya to adapt to these and other environmental changes the fourth conceptual model describes a very late terminal classic preplanned project on a floodplain these wetland fields were short lived aggraded rapidly but with some reoccupation in the postclassic all of these new models display the burgeoning evidence for intricate maya interactions with wetlands and the diversity of evidence from the relatively few studies underscores the infancy of our understanding of maya interaction with tropical wetlands

multi technique approach to rockfall monitoring in the montserrat massif catalonia ne spain abstract montserrat mountain is located near barcelona in catalonia in the northeast of spain and its massif is formed by conglomerate interleaved by siltstone sandstone with steep slopes very prone to rockfalls the increasing number of visitors in the monastery area reaching 2 4 million per year has highlighted the risk derived from rockfalls for this building area and also for the terrestrial accesses both roads and the rack railway a risk mitigation plan has been launched and its first phase during 2014 2016 has been focused largely on testing several monitoring techniques for their later implementation the results of the pilot tests performed as a development from previous sparse experiences and data are presented together with the first insights obtained these tests combine four monitoring techniques under different conditions of continuity in space and time domains which are displacement monitoring with ground based synthetic aperture radar and characterization at slope scale with an extremely non uniform atmospheric phase screen due to the stepped topography and atmosphere stratification terrestrial laser scanner surveys quantifying the frequency of small or even previously unnoticed rockfalls and monitoring rock block centimetre scale displacements the monitoring of rock joints implemented through a wireless sensor network with an ad hoc design of zigbee loggers developed by icgc and finally monitoring singular rock needles with total station

rapid post settlement floodplain accumulation in northland new zealand many river systems within new zealand and globally have experienced rapid acceleration in floodplain sedimentation in response to anthropogenic catchment disturbance creating significant issues i e flooding and water quality reconstruction of past river responses to environmental and anthropogenic driven changes in sedimentation and erosion can provide valuable insights into these river dynamics this research uses lidar data sedimentology radiocarbon chronology xrf analysis and gpr to examine pre and post settlement alluviation of the kaeo river and floodplain sedimentation in northland new zealand in kaeo rapid rates of post settlement floodplain aggradation equating to over 4 m of interbedded sand and silt alluvium in a partly confined valley setting have created considerable contemporary flooding issues radiocarbon dates indicate that terrestrially sourced sedimentation commenced at 7680 7570 cal yr bp and continued at an average rate of 1 mm yr 1 under conditions of limited accommodation space the holocene floodplain has accumulated at a faster average rate 8 13 5 mm yr 1 in the last several hundred years in response to anthropogenic catchment disturbance following m ori and european settlement this response mirrors the general trend for northland floodplains where there has been rapid accumulation of floodplains 3 10 mm yr 1 in the last 1000 yr

age and source of colluvial sediments at vaihingen enz germany abstract colluvial sediments accumulated on the lower slopes of a ridge as a result of past and present soil erosion were dated by optical 14 c and archaeological methods this allowed us to reconstruct the depositional history of the colluvium and also to identify temporary sedimentary sinks in its transportational pathway a cascade model of colluvium formation is developed colluvial sediments resulting from early soil erosion in the neolithic to iron age periods were mainly deposited on the upper slopes significant deposition on the lower slope occurred for the first time during the iron age and roman period since then deposition rates have increased because of more intensive land use

human impact on the environment in the ethiopian and eritrean highlands a state of the art abstract this review analyses the environmental evolution of the ethiopian highlands in the late quaternary the late pleistocene 20 000 12 000 14c years bp was cold and dry with 1 low lake levels in the rift valley 2 large debris fans on the flanks of lake abhe basin and 3 the blue nile transporting coarse bedload then a period with abundant and less seasonal rains existed between 11 500 and 4800 14c years bp as suggested by increased arboreal pollen high river and lake levels low river turbidities and soil formation around 5000 4800 14c years bp there was a shift to more arid conditions and more soil erosion many phenomena that were previously interpreted as climate driven might however well be of anthropic origin thick sediment deposits on pediments as well as an increase of secondary forest scrub and ruderal species in pollen diagrams are witnesses of this human impact one important aspect of the late quaternary palaeoenvironment is unclear changes in nile flow discharges and rift valley lake levels have been linked to changes in precipitation depth most authors do not take into account changes in land use in the highlands nor changes in the seasonality of rain both of which can lead to a change in runoff coefficients tufa and speleothem deposition around 14 000 years ago tend to indicate that at the end of the last glacial maximum lgm conditions might have been wetter than generally accepted the most important present day geomorphic processes are sheet and rill erosion throughout the country gullying in the highlands and wind erosion in the rift valley and the peripheral lowlands based on existing sediment yield data for catchments draining the central and northern ethiopian highlands an equation was developed allowing to assess area specific sediment yields sy 2595a 0 29 n 20 r 2 0 59 where sy area specific sediment yield t km 2 year 1 and a drainage area km2 with respect to recent environmental changes temporal rain patterns apart from the catastrophic impact of dry years on the degraded environment cannot explain the current desertification in the driest parts of the country and the accompanying land degradation elsewhere causes are changing land use and land cover which are expressions of human impact on the environment deforestation over the last 2000 3000 years was probably not a linear process in ethiopia studies on land use and land cover change show however a tendency over the last decades of increasing removal of remnant vegetation which is slowed down or reversed in northern ethiopia by a set aside policy ongoing land degradation requires urgent action at different levels of society soil and water conservation swc structures are now widely implemented local knowledge and farmer s initiatives are integrated with introduced swc techniques at various degrees impact assessments show clear benefits of the soil conservation measures in controlling runoff and soil erosion in high rain areas runoff management requires greater emphasis during the design of soil conservation structures in such areas investment in swc might not be profitable at farm level although benefits for society are positive this pleads in favour of public support the present land degradation in the ethiopian highlands has a particular origin which includes poverty and lack of agricultural intensification causes of these are to be found in the nature of past and present regional social relations as well as in international unequal development this review strengthens our belief that under improved socio economic conditions land husbandry can be made sustainable leading to a reversal of the present desertification and land degradation of the ethiopian highlands

beryllium 10 in chesapeake bay sediments an indicator of sediment provenance in a plot of 10 be vs fe central chesapeake bay sediments can be segregated into distinct units this plot reveals an unexpected statistically significant difference between sediments on the eastern and western flanks of the main channel implying different origins although the 10 be concentrations in sediments from these two regions span as much as an order of magnitude range the 10 be fe ratios vary by an amount approximating analytical error alone the large concentration ranges are ascribed to hydraulic sorting which can produce variance in composition while not affecting ratios between grain surface components such as fe and be on the basis of 10 be fe signatures sediments on the western flank of the main channel appear to have been derived from the susquehanna or another piedmont appalachian river sediments on the eastern flank may have been transported from the south by landward flowing bottom currents or may be relicts of a pleistocene estuarine system conditions under which 10 be may prove a useful tool in sediment provenance studies elsewhere are discussed

historical evolution of permanent gullies in the myjava hill land slovakia abstract the myjava hill land is part of the area with the highest density of permanent gullies in slovakia up to 11 km km 2 gullies are often 10 15 m deep and occasionally extend 20 m the pattern and density of gullies have been controlled primarily by the original land use from the pre collectivization era old maps and historical sources indicate two to three periods of gully formation the central part of the area settled between the second half of the 16th and the beginning of the 19th centuries was affected by gully formation in two periods the first between the end of the 16th century and the 1730s and the second roughly between the 1780s and 1840s marginal parts of the study area to the west and south west which were settled earlier may have been affected by disastrous gullying as early as the 14th century gullies were formed during periods of extensive forest clearance and expansion of farmland but the triggering mechanism of gullying was extreme rainfalls during the little ice age however periods of gully formation in the myjava hill land were not fully synchronous with the well known phases of gullying in other central european countries

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

delineating stratigraphic breaks at the bases of postglacial eolian dunes in central alberta canada using a portable osl reader temporal constraints for the late pleistocene deposition of eolian dunes that occur in central and northern alberta canada can be provided by dating sediments from the dune bases using luminescence techniques in places however the postglacial dunes overlie glaciofluvial sands that resemble the eolian deposits in texture such that demarcating the bases of the dunes is often problematic in this study we address the problem by employing a portable optically stimulated luminescence osl reader to construct luminescence profiles that depict luminescence signal variation with depth with the portable osl reader measurement can be performed on bulk sediments negating the need for laborious separation procedures to isolate pure mineral fractions as is required in regular luminescence dating measurements can also be carried out in the field permitting quicker decision making during sample collection results from this study presented as depth variations of feldspar derived infrared stimulated luminescence irsl signals and predominantly quartz generated post ir blue osl signals show that luminescence profiling enables one to distinguish between eolian deposits that make up the dunes from the underlying non eolian sands the identification of such cryptostratigraphic interfaces is made possible by differences in the dosimetric histories of the sediments the delineation of the dune bases allows targeted sampling that yields best luminescence age approximations for the initiation of postglacial eolian deposition in the region luminescence profiling of eolian sequences would also in theory permit the identification of depositional breaks of extended duration copyright 2012 john wiley sons ltd

late quaternary river evolution of floodplain pockets along mulloon creek new south wales australia valley confinement along upper middle reaches of mulloon creek in the upper shoalhaven catchment of southern new south wales australia restricts floodplain development to a series of distinct pockets these pockets comprise a downstream thinning wedge of vertically accreted fine grained deposits atop basal gravels some time before 12500 years ago a bedload dominated river was transformed into a suspended load system in the mid late holocene swamps developed in the middle lower part of each floodplain pocket within a few decades of european settlement of this region circa ad 1820 discontinuous watercourses in some floodplain pockets had incised to form a low sinuosity gravel bed channel wedge shaped units of post incisional alluvium that thicken downstream overlie the swamp and floodplain deposits in the downstream part of these pockets in the downstream most pocket incision commenced prior to colonization while upstream swamps retain a continuous swamp across the valley floor the late quaternary evolution of this variant of discontinuous watercourse is summarized in a schematic model

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

sedimentological processes in lahars insights from optically stimulated luminescence analysis abstract a lahar is a sediment laden flow capable of major destructive impacts on infrastructure and human life how lahars transport sediment is thus a key issue for understanding lahar sedimentology and behavior especially in terms of the lahar s hydraulic and rheological properties which can be substantially altered as the lahar gains or loses material during its travel in this research we analyze lahar entrainment processes by evaluating luminescence signals total photon counts from lahar sediments using blue luminescence signals blsl a portable osl reader that analyzes several grams of polymineral and polygrain size samples was applied we use data from three lahars in the tenenepanco and huiloac gorges on popocatepetl volcano mexico to elucidate the ways in which lahars may gain lose and transport sediment during flow sediment samples for luminescence analysis were taken through the full thickness of the lahar deposits at eight different sites for two lahars 1997 and 2001 and at one site for a lahar that occurred 500 yrs ago mean luminescence values obtained for the 1997 lahar help to evaluate the relationship between the lahar entrainment processes and the drainage at the different sites for the 2001 lahar this relationship was also established taking into account the channel slope the main conclusion is that luminescence signals total photon counts can be used to detect entrained material in the flow because the bulked materials modify the final osl signals the application of this type of luminescence analysis thus has the potential to provide a better understanding of sediment entrainment in these sediment laden flows

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

sedimentary development and correlation of late quaternary terraces in the kyrenia range northern cyprus using a combination of sedimentology and optical luminescence data this study focuses on the younger of a series of quaternary terraces along the flanks of the kyrenia range in northern cyprus specifically the kyrenia girne and the koupia terraces the kyrenia girne terrace is tentatively correlated with oxygen isotope stage 5 125 ka and the koupia terrace with oxygen isotope stage 3 50 ka along the northern flank of the range the kyrenia girne terrace deposits 5 20 m above modern sea level typically begin with a basal lag conglomerate and then pass upwards into shallow marine calcarenites and then into variable aeolianites paleosols and fluvial deposits up to 20 m thick in contrast the koupia terrace 2 m above modern sea level consists of aeolianites and shallow marine calcarenites up to 8 m thick the equivalent deposits along the southern flank of the range are entirely non marine fluvial mud sands and conglomerates the marine to continental terrace systems can be tentatively correlated based on mapping height above modern sea level and sedimentary facies however variable preservation and patchy exposure require such correlations to be independently tested to achieve this a portable optically stimulated luminescence osl reader was used to determine the luminescence characteristics of the two terrace systems luminescence profiles show major differences in luminescence characteristics between the two terrace depositional systems which can be related to sedimentary processes provenance and age these features allow sections in different areas to be effectively correlated individual sections show luminescence properties that are generally consistent with an expected up sequence decrease in age however the younger koupia terrace deposits show higher luminescence intensities compared with the older kyrenia girne terrace deposits this can be explained by multiple phases of reworking of the kyrenia girne terrace deposits which changed the luminescence characteristics of the sediment the use of the portable osl reader is therefore an effective means of correlating late quaternary terrace deposits in northern cyprus and probably also elsewhere

holocene floodplain formation in the southern cape region south africa abstract the sediments of holocene floodplain banks in several river catchments in the southern cape region south africa were sedimentologically investigated and radiometrically dated the study resulted in a differentiation into two sedimentation phases the sedimentation of the older phase starts directly above the bedrock or above coarse gravels these sediments are composed of 2 5 3 m of interbedded sand silt and clay in part they are stratified by organic horizons and inclusions the radiocarbon dating of numerous organic horizons as well as fossil wood shows that the sedimentation during the older phase occurred between 1215 and 875 years bp at the base and 670 and 15 years bp at the top of this sequence the sediments of the younger phase mainly consist of homogeneous fine sand and are at least 3 m thick stratigraphically above the sediments of the older deposition phase however the sediments of the younger layer can also comprise the entire holocene deposits situated above the current riverbed these sediments are mainly of modern age and are partly deposits of centennial flood events the context between the onset of sedimentation and the start of pastoral farming by settlers after ad 400 which has been archaeologically verified supports the hypothesis that the first sedimentation phase was set off or favoured by the degradation of the natural vegetation cover as a result of livestock farming later increased sedimentation as well as an increase in peak flows resulting from increased landscape degradation due to intensified pasture farming by the european settlers has to be assumed

the impact of humans on continental erosion and sedimentation rock uplift and erosional denudation of orogenic belts have long been the most impor tant geologic processes that serve to shape continental surfaces but the rate of geomor phic change resulting from these natural phe nomena has now been outstripped by human activities associated with agriculture con struction and mining although humans are now the most important geomorphic agent on the planet s surface natural and anthro pogenic processes serve to modify quite dif ferent parts of earth s landscape in order to better understand the impact of humans on continental erosion we have examined both long term and short term data on rates of sediment transfer in response to glacio fl u vial and anthropogenic processes phanerozoic rates of subaerial denuda tion inferred from preserved volumes of sedimentary rock require a mean conti nental erosion rate on the order of 16 m per million years m m y resulting in the accumulation of 5 gigatons of sediment per year gt yr erosion irregularly increased over the 542 m y span of phanerozoic time to a pliocene value of 53 m m y 16 gt yr current estimates of large river sediment loads are similar to this late neogene value and require net denudation of ice free land surfaces at a rate of 62 m m y 21 gt yr consideration of the variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confi ned to drainage headwaters 83 of the global river sediment fl ux is derived from the high est 10 of earth s surface subaerial erosion as a result of human activity primarily through agricultural practices has resulted in a sharp increase in net rates of continental denudation although less well constrained than estimates based on surviving rock volumes or current river loads available data suggest that present farmland denudation is proceeding at a rate of 600 m m y 75 gt yr and is largely confi ned to the lower elevations of earth s land surface primarily along passive continental margins 83 of cropland erosion occurs over the lower 65 of earth s surface the conspicuous disparity between natu ral sediment fl uxes suggested by data on rock volumes and river loads 21 gt yr and anthropogenic fl uxes inferred from measured and modeled cropland soil losses 75 gt yr is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately downslope from erod ing croplands over the history of human agriculture accumulation of postsettlement alluvium on higher order tributary channels and fl oodplains mean rate 12 600 m m y is the most important geomorphic process in terms of the erosion and deposition of sedi ment that is currently shaping the landscape of earth it far exceeds even the impact of pleistocene continental glaciers or the cur rent impact of alpine erosion by glacial and or fl uvial processes conversely available data suggest that since 1961 global cropland area has increased by 11 while the global population has approximately doubled the net effect of both changes is that per capita cropland area has decreased by 44 over this same time interval 1 per year this is 25 times the rate of soil area loss antici pated from human denudation of cropland surfaces in a context of per capita food pro duction soil loss through cropland erosion is largely insignifi cant when compared to the impact of population growth

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

impacts of the ancient maya on soils and soil erosion in the central maya lowlands abstract many studies across the central and southern maya lowlands of belize guatemala honduras and mexico have produced records of land degradation mostly sedimentation and soil erosion during the ancient maya period from before 1000 bc to the maya collapse of c ad 900 this paper provides new data from two sites blue creek and cancuen synthesizes more than a decade of the authors research in guatemala belize and mexico and synthesizes other findings from this region these research projects analyzed more than 100 excavations in upland and depression sites cored lakes and wetland sediments and studied sediments in the field and laboratory using radiocarbon dating a battery of soil chemistry tests stratigraphic analysis magnetic susceptibility elemental analyses and artifact identification our objective was to date when sedimentation and soil erosion occurred identify stable surfaces and correlate them with the state of knowledge about past land use these findings indicate three general epochs of accelerated soil erosion and identified two major paleosols the three waves of soil erosion occurred in the preclassic period c 1000 bc to ad 250 the late classic ad 550 to 900 and in the last several decades the major paleosol eklu um in these sites is a well developed mollisol or vertisol that started forming in the early holocene and was buried in either the preclassic or classic periods ad 250 to 900 at some sites the eklu um paleosol lies beneath sediments with a fainter paleosol which in turn lies buried below classic period and later sediments this picture shows higher than expected soil erosion linked to the region s first pioneer farmers in the preclassic and less than expected soil erosion in the late classic when population peaked and land use was the most intensive in other regions like cancuen guatemala however most soil erosion occurred during the maya late classic ad 550 830 erosion here was intense but short lived depressions record 1 3 m of aggradation in two centuries a third epoch of accelerated soil loss and aggradation arose with the rapid land use changes brought by new pioneers during the last several decades

real time stability assessment of unstable rocks based on fundamental natural frequency abstract the decrease in strength of potential slip surface after an earthquake and heavy rainfall is one of the main causes of rock failures however fundamental natural frequency can demonstrate the changes in physical and mechanical parameters and support a real time quantitative assessment of the safety of rocks this study applied laser doppler vibrometry in an experiment called frozen thawing test ftt in which the entire collapse process caused by strength degradation is simulated the results show that the safety factor calculated by fundamental natural frequency can give us a new method for stability assessment of unstable rocks therefore the method can satisfy real time safety evaluation of unstable rocks and will offer a foundation for better responses to rock collapse

mind the gap an absence of valley fill deposits identifying the holocene hypsithermal period of enhanced flow regime in southeastern australia the holocene sedimentary record in southeastern australia is present in a range of landscape settings such as upland swamps dells internally drained lake basins alluvial fans and mid catchmen

geomorphic responses to long term land use changes in eastern macedonia greece distinct phases of stream aggradation soil erosion and landscape stability in the basin of drama eastern macedonia greece over the past 7000 years can be tied directly to long term land use changes during the middle and late holocene 1 4 m of alluvial fill accumulated in the centre of the basin and along the angithis valley low levels of alluvial aggradation were recorded during the late neolithic and the early bronze age 7400 4000 cal bp in the centre of the basin along the lower course of the river xeropotamos the rate of aggradation has doubled since the late bronze age 0 5 0 6 mm year 1 compared to the holocene as a whole 0 25 mm year 1 moderate rates of alluvial fill were experienced during the late bronze age 3600 3000 cal bp but the most significant destabilisation of the soils occurred later than in many regions of greece two historical phases of alluvial aggradation and soil erosion are identified in the antique and the early byzantine era 3rd century bc 7th century ad and more significantly in the ottoman period beginning of the 15th to the 20th century ad in the latter period the rate of accumulation was three to five times greater than in the late holocene almost three millennia intervened between the arrival of the first farmers and the onset of erosion this is mainly explained by the settlement pattern during the neolithic and the early bronze age it seems that the early farmers preferred to cultivate the more stable soils on the gentle slopes at the centre of the basin during the late bronze age the land use pattern changed the soils then under cultivation on the foothills were less stable and the steeper slopes were more susceptible to erosion this limited the potential for forest restoration after the first noticeable land clearance and probably explains the extent of alluvial aggradation since the antique era the intensity of land use has increased the two phases of accelerated alluviation in historical times are clearly linked to land use changes particularly with the upstream progression of cropping and grazing onto more sensitive lands in foothills and mountainous areas though this was also influenced by climatic fluctuations the major period of aggradation in the ottoman period is clearly associated with both climatic and anthropogenic factors it seems that the early historic deforestation and agricultural activities rendered river systems more sensitive to relatively modest changes in climate

natural streams and the legacy of water powered mills gravel bedded streams are thought to have a characteristic meandering form bordered by a self formed fine grained floodplain this ideal guides a multibillion dollar stream restoration industry we have mapped and dated many of the deposits along mid atlantic streams that formed the basis for this widely accepted model these data as well as historical maps and records show instead that before european settlement the streams were small anabranching channels within extensive vegetated wetlands that accumulated little sediment but stored substantial organic carbon subsequently 1 to 5 meters of slackwater sedimentation behind tens of thousands of 17th to 19th century milldams buried the presettlement wetlands with fine sediment these findings show that most floodplains along mid atlantic streams are actually fill terraces and historically incised channels are not natural archetypes for meandering streams

response of a landscape to tectonics using channel steepness indices ksn and osl a case of study from the jalisco block western mexico abstract rapid tectonic uplift is known to increase river incision rates and to trigger the propagation of knickpoints along a river profile augmenting local relief thus the topography of mountainous landscapes records long term interactions between tectonics and climate we evaluate the geomorphic response to differential rock uplift with topographic analysis of 16 river basins including the normalized channel steepness index k sn our study focuses on rivers incising the northern and western sectors of the jalisco block western mexico a crustal unit bounded by plio quaternary extensional faulting we use osl signals from 17 riverbed samples to assess erosion rates the results indicate that basins in the northern sector have higher rates of rock uplift and erosion mean k sn 111 18 m 0 9 than those in the southwest mean k sn 77 23 m 0 9 in spite of the plio quaternary lavas that cap large areas of the northern sector the development of plio quaternary grabens and half grabens along the northern boundary of the jalisco block has increased the erosion rates augmenting the local relief by contrast the topography of the basins in the southwestern sector has resulted from a long erosional history controlled by the migration of old tectonic signals farther upstream in this region the landscape seems to have reached the steady state and is currently experiencing the propagation of knickpoints due to the increase in the rate of rock uplift in the coast of jalisco during the holocene

european impacts on downstream sediment transfer and bank erosion in cobargo catchment new south wales australia abstract upland valley fills in cobargo catchment on the south coast of new south wales represent substantial sediment source zones contemporary channels within these fills are up to 8 m deep and 50 m wide for catchment areas 2 virtually all banks are eroding downstream of this sediment source zone sediment transfer zones are characterised by sinuous channels that are partially choked by sands released from upland valley fills coarse sands stored in point bars deflect flow to outer banks where colluvial footslopes are eroded approximately 50 of banks are eroding in this section of the catchment other than the 10 km river reach upstream of the river mouth the remainder of the catchment is a bedrock confined sediment throughput zone characterised by fluctuations in channel bed elevation the downstream 10 km of the catchment is a sediment accumulation zone in which erosion is restricted to occasional concave banks prior to european settlement of cobargo catchment upland valley fills were largely unincised and middle transfer reaches of the catchment comprised swamps vegetation clearance along with disturbance and drainage of swamps transformed discontinuous water courses into continuous channels working from a base point of intact upland valley fills almost 50 of available material has been removed from the upper catchment sediment source zone contributing 2 9 10 6 m 3 of material to the lower catchment of this roughly 65 has been stored along the channel bed and floodplain this gives a total sediment contribution to the delta of 1 0 10 6 m 3 sufficient materials are stored in transient storage units along transfer zones to maintain current rates of sediment throughput to the delta for several decades cobargo catchment experienced dramatic acceleration of channel incision and bank erosion processes within a few decades following european settlement of the catchment i e around 1830 transition in landscape form and associated sediment delivery were rapid with a negligible lag interval i e within a few decades of disturbance however given the extensive volume of sediment released from upland valley fills landscape recovery i e refilling of upland valleys will likely take thousands of years

subterranean transport and deposition of quartz by ants in sandy sites relevant to age overestimation in optical luminescence dating an artificial layered sandy site was created using a combination of native sand and colored sand 3 parts native uncolored quartz 1 part colored quartz in apalachicola national forest near tallahassee florida twelve layers of sand each 1 by 1 m in horizontal extent by 10 cm in thickness were emplaced to a depth of 2 m followed by implantation at the surface of a florida harvester ant pogonomymrex badius colony the lower two layers were 50 cm thick the colony excavated a nest and after 7 months the sand layers were excavated to the base to test the hypothesis that sand grains were moved upward within the ant nest without reaching the surface the ants penetrated 11 of the 12 colored layers reaching a depth of 130 cm thirty nine sticky acetate peels of ant chamber floors were collected and colored sand grains were counted under a microscope more than 16 000 grains were identified in layers that did not originally host them of these more than 80 were unambiguously moved upward this means that possibly as many as 54 000 upwardly mobile grains were present ratio of 3 1 uncolored to colored in relation to optical luminescence osl dating this means that grains that would not have been optically zeroed by transport to the surface defined here as subterranean transported were present in abundance and that if the site was ancient there would have been found many grains that were older than the layers they presently reside in even if only one colony of harvester ants had disturbed the layers this is in addition to the fact that backfilling of chambers and tunnels may contribute even more significantly to the presence of a subterranean transported component of an osl sample we conclude that ants can significantly affect the age distributions in sandy archaeological sites multiple examples of such disturbances have been documented in the literature most relevant to our results are recent studies of the osl chronology of pre clovis age and palaeoindian age archaeological sites in sandy environments in north america that may have been compromised by ant bioturbation of quartz sand grains here we have examined in detail the potential effects of one episode of ant nest building on the age overestimation of affected sediments from this we found that as few as 12 episodes of bioturbation involving backfilling of chambers in the same volume of sand could lead to the presence of 1 contaminant grain per 50 grains of sample

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

mid infrared spectroscopy of impactites from the nordlinger ries impact crater abstract this study is part of an effort to build a mid infrared database 7 14 m of spectra for mertis mercury radiometer and thermal infrared spectrometer an instrument onboard of the esa jaxa bepicolombo space probe to be launched to mercury in 2017 mercury was exposed to abundant impacts throughout its history this study of terrestrial impactites can provide estimates of the effects of shock metamorphism on the mid infrared spectral properties of planetary materials in this study we focus on the nordlinger ries crater in southern germany a well preserved and easily accessible impact crater with abundant suevite impactites suevite and melt glass bulk samples from otting and aumuhle as well as red suevite from polsingen were characterized and their reflectance spectra in mid infrared range obtained in addition in situ mid infrared spectra were made from glasses and matrix areas in thin sections the results show similar but distinguishable spectra for both bulk suevite and melt glass samples as well as in situ measurements impact melt glass from aumuhle and otting have spectra dominated by a reststrahlen band at 9 3 9 6 m bulk melt rock from polsingen and bulk suevite and fine grained matrix have their strongest band between 9 4 and 9 6 m there are also features between 8 5 and 9 m and 12 5 12 8 m associated with crystalline phases there is evidence of weathering products in the fine grained matrix such as smectites mercury endured many impacts with impactors of all sizes over its history so spectral characteristics observed for impactites formed only in a single impact like in the ries impact event can be expected to be very common on planetary bodies exposed to many more impacts in their past we conclude that in mid infrared remote sensing data the surface of mercury can be expected to be dominated by features of amorphous materials

a 2500 year record of natural and anthropogenic soil erosion in south greenland the environmental impact of the norse landnam in greenland has been studied extensively but to date no study has quantified the soil erosion that norse agricultural practices are believed to have caused to resolve this problem a high resolution sedimentary record from lake igaliku in south greenland is used to quantitatively reconstruct 2500 years of soil erosion driven by climate and historical land use an accurate chronology allows for the estimation of detritic fluxes and their uncertainties land clearance and the introduction of grazing livestock by the norse around 1010 ad caused an acceleration of soil erosion up to 8 mm century in 1180 ad which is two fold higher than the natural pre landnam background from 1335 ad to the end of the norse eastern settlement in the mid fifteenth century the vegetation began to recover from initial disturbance and soil erosion decreased after an initial phase of modern sheep breeding similar to the medieval one the mechanization of agriculture in the 1980s caused an unprecedented soil erosion rate of up to 21 mm century five times the pre anthropogenic levels independently a suite of biological and geochemical proxies including ti and diatom concentrations c n ratio 13c and 15n of organic matter confirm that the medieval and modern anthropogenic erosion far exceeds any natural erosion over the last 2500 years our findings question the veracity of the catastrophic scenario of overgrazing and land degradation considered to have been the major factor responsible for norse settlement demise they also shed light on the sustainability of modern practices and their consequences for the future of agriculture in greenland

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

the history of holocene soil erosion in the phlious basin ne peloponnese greece based on optical dating anthropogenic induced soil erosion has occurred in the mediterranean during historic and pre historic times but precise timeframes for periods of past soil erosion are largely missing due to the lack of datable material and suitable dating methods in this study optical dating of colluvial sediments from the phlious basin ne peloponnese greece was applied the results show that soil erosion derived colluvium formed under a mediterranean type climate can be successfully dated by optical stimulated luminescence osl and a high resolution chronology of holocene soil erosion could be established colluvial formation occurred in the early holocene but increased distinctly in the seventh millennium parallel with the onset of the neolithic the start of farming activities other periods of strong colluviation are the middle and late bronze age second millennium the roman period first century to sixth century and the period since the sixteenth century rates of reduced colluviation occurred during

detection of erosion events using10be profiles example of the impact of agriculture on soil erosion in the chesapeake bay area u s a 10be concentration total carbon and grain size were measured in cores collected in undisturbed estuarine sediments of three tributaries of the chesapeake bay these cores were previously studied by davis 1 and brush 2 3 for pollen content age and sedimentation rate in this work we compare the results obtained for these various analyses in the cores we observed two increases in10be concentration concomitant with two major changes in the pollen composition of the sediments these two pollen changes each correspond to well dated agricultural horizons reflecting different stages in the introduction of european farming techniques 2 in the chesapeake bay area the agricultural development associated with forest clearing appears to have triggered the erosion transport and sedimentation into the river mouths of large quantities of10be rich soils this phenomenon explains the observed rise in the sedimentation rate associated with increases in agricultural land use