chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

precambrian ophiolites cambrian island arc and variscan suture in the south carpathian balkan region a late proterozoic ophiolite in the south carpathian balkan region has a total surface outcrop area of 400 km 2 it is a complete ophiolitic section that includes mid ocean ridge basalts indicating that it was formed in a large ocean the oceanic crust is unconformably overlain by an ensimatic island arc of cambrian age the ophiolite island arc assemblage was obducted over the moesian platform during early ordovician time both sequences are now incorporated in a continental block as a result of intracontinental convergence which took place in variscan time the ophiolite is situated along the thracian suture which divides the moesian platform and the thracian continental fragment this suture is part of a larger one referred to as the south european suture that is situated between the thracian massif and the adriatic plate to the southwest and the moesian platform bohemian and central french massif to the northeast

sediment contributions from floodplains and legacy sediments to piedmont streams of baltimore county maryland abstract disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades with the role of floodplains in sediment storage as a common focus in the piedmont province of the eastern usa upland deforestation and agricultural land use following european settlement led to accumulation of thick packages of overbank sediment in valley bottoms commonly referred to as legacy deposits previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening this paper seeks to quantify 1 rates of sediment remobilization from baltimore county floodplains by channel migration and bank erosion 2 proportions of streambank sediment derived from legacy deposits and 3 potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the mid atlantic piedmont we calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0 18 and 155 km2 in baltimore county maryland we compared stream channel and floodplain morphology from lidar based digital elevation data collected in 2005 with channel positions recorded on 1 2400 scale topographic maps from 1959 1961 in order to quantify 44 46 years of channel change sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources average annual lateral migration rates ranged from 0 04 to 0 19 m y which represented an annual migration of 2 5 0 9 4 4 channel width across all study segments suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates gross bank erosion rates varied from 43 to 310 mg km y median 114 and were positively correlated with drainage area measured deposition within channels accounted for an average of 46 28 75 of gross erosion with deposition increasingly important in larger drainages legacy sediments accounted for 6 90 of bank erosion at individual study segments represented about 60 of bank height at most exposures and accounted for 57 16 of the measured gross erosion extrapolated results indicated that first and second order streams accounted for 62 38 of total streambank erosion from 1005 km2 of northern baltimore county after accounting for estimated redeposition extrapolated net streambank sediment yields 72 mg km2 y constituted 70 of estimated average piedmont watershed yields 104 mg km2 y the results suggest that streambank sediments are a relatively large source of sediment from piedmont tributaries to the chesapeake bay

variscan tectonics of central europe postaccretionary intraplate deformation of weak continental lithosphere the area occupied by the variscan belt of central europe forms part of gondwana derived microplates essentially avalonia and armorica that according to paleomagnetic data juxtaposed baltica and laurentia from the upper ordovician to the lower devonian the actual structure of this area is a puzzle of rather small fault bounded crustal blocks different in p t t histories which was created by later tectonic processes at around 360 to 320 ma according to a common view and by contrast to paleomagnetic data the structural record of fault bounded blocks is interpreted in terms of mid devonian to lower carboniferous amalgamation of narrow continental plates represented by the fault bounded blocks themselves however this is not supported in this article instead it will be shown that fault systems and fault bounded blocks were created by intraplate deformation of a weak domain of gondwana derived continental lithosphere significantly after its accretion deformation was partitioned into newly formed deep seated strike slip and kinematically connected reverse or normal detachment systems large translation magnitudes caused juxtaposition of crustal areas of variable thickness until they were emplaced along the fault systems the various categories of fault bounded complexes record different tectonic events category 1 metamorphic complexes represent deep seated parts of thickened crust some time before unroofing on the detachment systems between about 340 360 and 320 ma however the record of subduction and extreme crustal thickening during earlier stages of the collision history was erased to a high degree and is only preserved by mineral and structural relics strike slip and detachment systems propagated across and dismembered tectonic boundaries formed during these early events category 2 metamorphic complexes and the barrandian basin recording predominant pre late devonian metamorphic or stratigraphic events represent the brittle upper crustal parts during continuing metamorphism in the category 1 complexes weakly or unmetamorphosed lower paleozoic category 3 basins represent areas of thinned continental crust and record subsidence before and to some degree during activity of detachment systems the complex overall kinematic pattern of block bounding strike slip and detachment systems indicates compression and extension acting simultaneously this probably reflects the effects of continuing oblique plate convergence rotation and wsw extrusion of fault bounded blocks in addition to heating and extensional flow of previously thickened crustal areas

measuring bluff erosion part 1 terrestrial laser scanning methods for change detection human activities influence watershed sediment dynamics in profound ways often resulting in excessive loading of suspended sediment to rivers one of the primary factors limiting our ability to effectively manage sediment at the watershed scale has been our inability to adequately measure relatively small erosion rates on the order of millimeters to centimeters per year over annual and sub annual time scales on spatially extensive landforms such as river banks and bluffs terrestrial laser scanning tls can be employed to address this need tls collects high resolution data allowing for more accurate monitoring of erosion rates and processes and provides a new opportunity to make precise measurements of geomorphic change on vertical landforms like banks and bluffs but challenges remain this research highlights challenges and limitations of using tls for change detection on river banks and bluffs including the presence of vegetation natural surface crenulations and difficulties with creating benchmarks and provides solutions developed to overcome these limitations results indicate that data processing algorithms for change detection can have a significant impact on the calculated erosion rates with different methods producing results that can vary by over 100 the most accurate change detection technique compares a point cloud to a triangulated irregular network tin along a set of vectors that accommodate bluff curvature this paper outlines a variety of methods used to measure bluff change via tls and explains the accompanying error analysis that supports these methods copyright 2012 john wiley sons ltd

determining the times and distances of particle transit in a mountain stream using fallout radionuclides abstract targeting of erosion and pollution control programs is much more effective if the time for fine particles to be transported through a watershed the travel distance the proportions of old and new sediment in suspension and the rate of erosion of the landscape can be estimated in this paper we present a novel technique for tracing suspended sediment in a mountain stream using fallout radionuclides sorbed to sediment atmospherically delivered 7 be 210 pb and 137 cs accumulate in the snowpack are released with its melting and sorb to fine particulates a portion of which are carried downslope into stream channels the half life of cosmogenic 7 be is short 53 4 days thus sediment residing on the stream bed should contain little of the radionuclide the different signatures of newly delivered sediment from the landscape with its 7 be tag and older untagged sediment from the channel is the basis for the tracing the total flux of such radionuclides compared to the inventory in the soil permits estimates of the rates of erosion of the landscape fine suspended particulates in the gold fork river id are transported downstream through the drainage in one or more steps having lengths of tens of kilometers length of the step decreases from about 60 km near the peak of the hydrograph to about 12 km near baseflow the percent of sediment in suspension that is new i e recently delivered from the landscape ranges from 96 to 12 the remaining sediment is resuspended older channel sediment residence times for particulates range from 1 6 days early in the hydrograph at the upper site to 103 days late in the hydrograph at the lowest elevation location rates of erosion of fine sediment calculated from the flux of radionuclides average 0 0023 cm year the long distance transport of fine particles suggests that delivery through the gold fork drainage to the basin outlet is fairly rapid once particles reach the channel and perhaps is also rapid in similar and smaller basins

factors controlling sediment yield from small intensively cultivated catchments in a temperate humid climate abstract data on sediment yield from 26 small cultivated catchments 10 10 000 ha in central belgium were collected based on sedimentation rates in small flood retention ponds area specific sediment yield varies from 0 4 to 20 6 t ha 1 year 1 for catchments ranging from 7 to 4873 ha various catchment properties were analysed in order to understand this large variation in sediment yield catchment area alone explains 64 of the observed variance in area specific sediment yield although no other parameter could explain more it is concluded that catchment area is not a valid parameter to link with sediment yield overall catchment geomorphology e g presented by the hypsometric integral is much more important in controlling sediment yield the lack of data however made this not very clear a multiple regression model including three morphological catchment properties is a valuable tool to predict total sediment yield t year 1 from catchments in central belgium this model has an efficiency of 0 81 furthermore it was concluded that the within catchment spatial distribution of parameters for instance slope steepness is very important but difficult to obtain one single representative value the use of spatially distributed erosion and sediment delivery models is therefore necessary accurate sediment yield data like the one presented in this study however are needed to validate these models

terex toolbox for semi automated selection of fluvial terrace and floodplain features from lidar terraces and floodplains are important indicators of near channel sediment dynamics serving as potential sediment sources and sinks increasing availability of high resolution topography data over large areas calls for development of semi automated techniques for identification and measurement of these features in this study we introduce a novel tool that accommodates user defined parameters including a local relief threshold selected by a variable size moving window minimum area threshold and maximum distance from the channel to identify and map discrete terrace and floodplain surfaces each of the parameters can easily be calibrated for a given watershed or reach subsequently the tool automatically measures planform area absolute elevation and height relative to the local river channel for each terrace polygon we validate the tool in two locations where terrace maps were previously developed via manual digitization from lidar and extensive field mapping campaigns the tool is also tested on six different types of rivers to provide examples of starting selection parameters and to test effectiveness of the tool across a wide range of landscapes generally the tool provides a high quality draft map of terrace and floodplain surfaces across the wide range of environmental conditions for which it has been tested we find that the tool functions best in catchments where the terraces are spatially extensive with distinct differences between the terrace and floodplain the most challenging environments for semi automated terrace and floodplain mapping include steep catchments with dense riparian vegetation and very small terraces 10 m2 in areal extent we then apply the tool to map terraces and floodplains in the root river watershed southeastern minnesota and generate exceedance plots for terrace heights these plots provide a first pass analysis to indicate the tributaries and reaches of the river where terraces constitute a significant source of sediment copyright 2013 john wiley sons ltd

landscape scale geomorphic change detection quantifying spatially variable uncertainty and circumventing legacy data issues abstract repeat surveys of high resolution topographic data enable analysis of geomorphic change through digital elevation model dem differencing such analyses are becoming increasingly common however techniques for developing robust estimates of spatially variable uncertainty in dem differencing estimates have been slow to develop and are underutilized further issues often arise when comparing recent to older data sets because of differences in data quality airborne lidar data were collected in 2005 and 2012 in blue earth county minnesota 1980 km2 and the occurrence of an extreme flood in 2010 produced geomorphic change clearly observed in the field providing an opportunity to estimate landscape scale geomorphic change initial assessments of the lidar derived digital elevation models dems indicated both a vertical bias attributed to different geoid models and localized offset strips in the dem of difference from poor coregistration of the flightlines we applied corrections for both issues and describe the methods we used to discern those issues and correct them we then compare different threshold models to quantify uncertainty poor quantification of uncertainty can erroneously over or underestimate real change we show that application of a uniform threshold often called a minimum level of detection overestimates change in areas where change would not be expected such as stable hillslopes and underestimates change in areas where it is expected and has been observed such as channel banks we describe a spatially variable dem error model that combines the influence of slope point density and vegetation in a fuzzy inference system vegetation is represented with a metric referred to as the cloud point density ratio that assesses the complete point cloud to describe the density of above ground features that may hinder bare earth returns we compare the significance of spatially variable versus spatially uniform dem errors on change detection by thresholding the dem of difference at a 95 confidence interval 2 results indicate significant geomorphic change in relatively predictable locations such as erosion on the outside and deposition on the inside of bends final totals indicated net erosion of 2 625 100 2 389 000 m3 in the county between 2005 and 2012 of this 39 was generated from bluffs 1 from ravines and the remainder came from banks and floodplain areas

the partitioning of the total sediment load of a river into suspended load and bedload a review of empirical data the partitioning of the total sediment load of a river into suspended load and bedload is an important problem in fluvial geomorphology sedimentation engineering and sedimentology bedload transport rates are notoriously hard to measure and at many sites only suspended load data are available often the bedload fraction is estimated with rule of thumb methods such as maddock s table which are inadequately field tested here the partitioning of sediment load for the pitzbach is discussed an austrian mountain stream for which high temporal resolution data on both bedload and suspended load are available the available data show large scatter on all scales the fraction of the total load transported in suspension may vary between zero and one at the pitzbach while its average decreases with rising discharge i e bedload transport is more important during floods existing data on short and long term partitioning is reviewed and an empirical equation to estimate bedload transport rates from measured suspended load transport rates is suggested the partitioning averaged over a flood can vary strongly from event to event similar variations may occur in the year to year averages using published simultaneous short term field measurements of bedload and suspended load transport rates maddock s table is reviewed and updated long term average partitioning could be a function of the catchment geology the fraction of the catchment covered by glaciers and the extent of forest but the available data are insufficient to draw final conclusions at a given drainage area scatter is large but the data show a minimal fraction of sediment transported in suspended load which increases with increasing drainage area and with decreasing rock strength for gravel bed rivers whereby in large catchments the bedload fraction is insignificant at 1 for sand bed rivers the bedload fraction may be substantial 30 50 even for large catchments however available data are scarce and of varying quality long term partitioning varies widely among catchments and the available data are currently not sufficient to effectively discriminate control parameters

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

correlation and paleomagnetism of glacial and loess paleosol sequences on the west siberian plain abstract a complex assemblage of geological biostratigraphical paleopedological magnetostratigraphical and radiometric techniques has been used for analysis and correlation of deposits on the west siberian plain a series of magnetostratigraphical columns has been constructed and the glacial alluvial lacustrine and loess paleosol deposits compared the data are paleomagnetic boundaries such as the brunhes matuyama boundary the base of the jaramillo subchron and the blake excursion their position in the sections is discussed a loess paleosol succession is considered in detail the number of climatostratigraphic cycles is comparable with the world s standard sections of similar genesis special attention is given to the description of the early pleistocene stages of soil formation the malinovka pedocomplex has been described here for the first time it is related to the final stage of the matuyama chron and is characterized by fauna similar to the petropavovka karai dubina fauna a scheme is proposed to correlate glacial and loess paleosol deposits on the west siberian plain and to compare them with the oxygen isotope scale

climate changes in east europe and siberia at the late glacial holocene transition abstract the main climatic oscillations of the lateglacial early holocene allerod younger dryas and preboreal can be distinguished all over eastern europe and siberia distribution of the main climatic indices in the lateglacial early holocene from west to east in northern eurasia shows that variations of the mean january temperature t jan o were larger than those of july temperature t july o as at present t jan o decreased to the east while the deviations from the present day values were greater in the west during the younger dryas the seasonality of climate increased considerably especially in the western european part of the studied area the greatest negative temperature deviations from the present day values up to 14 c occurred in the northwestern part of the east european plain near the scandinavian ice sheet it can be explained by a cooling influence from the remaining large ice body accordingly with degradation of the ice sheet at the warmer intervals of the lateglacial and early holocene the regional differences in temperature deviations became smaller up to 8 c on the whole precipitation p decreased in an easterly direction though its deviations from the modern level varied for different time intervals during the younger dryas p amounted to 60 65 of the present day values in the east european plain 80 in central west siberia and only 50 in central yakutia for the entire northern eurasia p did not exceed 300 350 mm yr in yakutia it was only 100 mm yr levels typical for present day dry steppe and semidesert zones nevertheless the reconstructed changes of the main climatic indexes were proportional to the present day climatic characteristics so that the general tendencies of their contemporary distribution in the mid latitudes were preserved during the entire lateglacial early holocene interval this shows that the general circulation of the atmosphere and geographical distribution of the main highs and lows in the studied time interval were in essence similar to the present day ones boundaries of permafrost in lateglacial and early holocene migrated in response to climate changes the southern limit of permafrost during the allerod was at 60 n in east europe and 55 n in west siberia during the younger dryas it moved south to 50 52 n in east europe and parabolic sand dunes were formed

regional to local environmental changes in southern western siberia evidence from biotic records of mid to late holocene sediments of lake beloye abstract the paper presents the first paleontological data pollen plant macrofossil diatom and ostracod on the sediments of lake beloye which is situated in the forest steppe zone of western siberia our study contributes to better understanding of the middle late holocene regional to local environmental changes regionally we recognized a cold stage of 3 4 2 3 calibrated ka bp and a dry stage of 2 8 1 7 ka bp the dry stage coincides with the climate driven lowered level of the lake at 2 6 1 5 ka bp later the climate changed to warmer and wetter which resulted in a highest stand of the lake at 1 3 0 2 ka bp and was followed by the lowering of the lake forest steppe persisted in this area during the whole period under consideration but probably shifted southward such a shift is reflected in the environment around lake beloye similar to that of modern taiga which existed at 3 2 1 3 ka bp however compared to the colder and wetter climate of taiga the conditions were colder and drier the local plant associations and the lake ecosystem were affected by those events of climate and lake level changes the initial eutrophic sedge reed swamp evolved to the oligo mesotrophic sphagnum bog which existed around the lake at 3 2 1 3 ka bp later the bogging process was interrupted by the lake transgression after which the dried bog around the lake was occupied by the birch forest the lake ecosystem was strongly affected by the 3 4 ka bp climate change the low alkaline eutrophic lake with abundant water higher plants and diatoms changed to the alkaline oligotrophic lake with calcium fixing macrophytic algae and angiosperms this resulted in total change of lake s bio geochemical and sedimentation patterns

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

chronology of glacial lake agassiz meltwater routed to the gulf of mexico abstract sediment cores with new radiocarbon dates from the southern outlet of glacial lake agassiz indicate that meltwater delivery to the mississippi valley was disrupted at 10 800 14 c yr b p and the outlet was abandoned by 9400 14 c yr b p these findings confirm the timing of generally accepted terminations of the lockhart and emerson phases of lake agassiz additionally the radiocarbon chronology indicates that the spillway was fully formed by 10 800 14 c yr b p and that the occupancy in late emerson time was likely short lived with minimal spillway erosion

climate and environmental dynamics of the mid to late holocene settlement in the tobol ishim forest steppe region west siberia abstract environmental archaeology multi proxy records provide eloquent evidence of climate changes and the related natural transformations in the forest steppe parkland zone of sw west siberia during the last ca 8500 years from the late boreal to sub atlantic period chronologically encompassing the regional cultural evolution time span from the mesolithic through the neolithic aeneolithic the bronze and iron ages to historical times close links of the palaeoclimate conditions and the early occupation migrations in the tobol ishim region are manifested by specific socio economic adaptive patterns reflecting landscape dynamics and availability of natural resources as well as scale and intensity of broader territorial cultural interactions pollen spectra from the investigated stratified archaeological sites and palynological sections indicate large scale landscape restructurings related to both the natural as well as intensified anthropogenic activities the periodic climate aridization of the central asian climate regime leading to the northern expansion of steppes in the south of west siberia repeatedly activated inflow of pastoralist communities from the south west further north and east into the former forest steppe and taiga parkland zones at several stages during the holocene in contrast during the moderately cold and humid intervals with intensified precipitations due to the strengthening influence of the atlantic atmospheric streams aboriginal groups of hunters and fishermen linked to the antecedent west siberian and trans ural mesolithic cultures expanded into the former open southern steppe regions in the process of re establishment of the southern taiga parkland forest environments these climatically triggered vegetation zone shifts and territorial population movements are well manifested in the material culture

modeling framework for sediment deposition storage and evacuation in the floodplain of a meandering river application to the clark fork river montana 1 a theory for the evolution of a river floodplain and the associated movement of tracer sediment is applied to the case of the upper clark fork river montana whose floodplain is contaminated with tailings derived from historical mining activities deposition of mine tailings raised the elevation of the floodplain which now contributes contaminated sediment to the channel the theory is capable of reproducing the basic aspects of the system s evolution including aggradation of the floodplain during the mining era and subsequent net supply of sediment from floodplain to channel after the cessation of mine input results indicate that the natural removal of tailings from the floodplain could take thousands of years a period longer than is required for the channel to simply rework the tailings the self stabilizing nature of the model results in an evolution toward a new postmine steady state with tailings eventually almost entirely removed from the system

a rational sediment transport scaling relation based on dimensionless stream power the concept of stream channel grade according to which a stream channel reach will adjust its gradient s in order to transport the imposed sediment load having magnitude qb and characteristic grain size db with the available discharge q mackin 1948 geological society of america bulletin59 463 512 lane 1955 american society of civil engineers proceedings81 1 17 is one of the most influential ideas in fluvial geomorphology herein we derive a scaling relation that describes how externally imposed changes in either qb or q can be accommodated by changes in the channel configuration described by the energy gradient mean flow depth characteristic grain size and a parameter describing the effect of bed surface structures on grain entrainment one version of this scaling relation is based on the dimensionless bed material transport parameter w presented by parker and klingeman 1982 water resources research18 1409 1423 an equivalent version is based on a new dimensionless transport parameter e using dimensionless unit stream power this version is nearly identical to the relation based on w except that it is independent of flow resistance both versions of the scaling relation are directly comparable to lane s original relation in order to generate this stream power based scaling relation we derived an empirical transport function relation relating e to dimensionless stream power using data from a wide range of stable bed load dominated channels the form of that transport function is based on the understanding that while grain entrainment is related to the forces acting on the bed described by dimensionless shear stress sediment transport rate is related to the transfer of momentum from the fluid to the bed material described by dimensionless stream power copyright 2010 john wiley sons ltd

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

peri amazonian avalonian type and ganderian type terranes in the south carpathians romania the danubian domain basement abstract the danubian domain basement of the south carpathians romania comprises two neoproterozoic continental crustal fragments the dr gsan and lainici p ius terranes which were sutured by the closure of an intervening oceanic domain the tisovi a terrane magmatic and detrital zircons extracted from an orthogneiss four granitoid plutons two metasedimentary units and a liassic sandstone were dated by zircon u pb la icp ms the f ge el augen gneiss from the dr gsan terrane basement yielded an age of 803 2 4 4 ma the oldest well constrained crystallization age reported from the romanian carpathians basement the tismana usi a novaci and olte granitoid plutons which intrude the lainici p ius terrane basement yielded ages of 600 5 4 4 591 0 3 5 592 7 4 9 and 588 2 9 ma respectively the tismana granitoid age of 600 ma and the youngest detrital zircon ages of 637 622 ma from a metaquartzite within the lainici paius terrane constrain the deposition of the metaquartzite protolith to ca 620 600 ma the 803 ma age represents an old pan african age whereas the younger neoproterozoic ages suggest pan african cadomian thermotectonic events detrital and inherited zircon ages within the dr gsan and lainici paius terranes attest to a peri amazonian avalonian type provenance for the dr gsan terrane and possibly a ganderian type provenance for the lainici p ius terrane the lainici p ius terrane rifted off gondwana before the dr gsan terrane both terranes were attached to moesia during the early paleozoic

measuring bluff erosion part 2 pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget effectively managing and reducing high suspended sediment loads in rivers requires an understanding of the magnitude of major sediment sources as well as erosion and transport processes that deliver excess fine sediments to the channel network the focus of this research is to determine the magnitude of erosion from tall bluffs a primary sediment source in the 2880 km2 le sueur watershed minnesota usa we coupled analyses of seven decades of aerial photographs with four years of repeat terrestrial laser scanning tls to determine erosion rates on bluffs together these datasets provide decadal scale retreat rates throughout the entire watershed and high resolution geomorphic change detection on a subset of bluffs to both constrain erosion rates and document how environmental conditions affect bluff retreat erosion rates from aerial photographs and tls were extrapolated from 243 and 15 measured bluffs respectively to all 480 bluffs in the le sueur watershed using multiple techniques to obtain estimates of sediment loading from these features at the watershed scale despite different spatial and temporal measurement scales the aerial photograph and tls estimates yielded similar results for bluff retreat rate and total mass of sediment derived from bluffs with bluffs in the le sueur watershed yielding 135 000 39 000 mg yr of fine sediment comparing this value to the average annual total suspended solids tss load determined from gauging from 2000 to 2010 we determined that bluffs comprise 57 16 of the total tss load making bluffs the single most abundant fine sediment source in the basin copyright 2012 john wiley sons ltd

holocene paleoenvironmental changes reflected in peat and lake sediment records of western siberia geochemical and plant macrofossil proxies abstract this paper presents the first result of a study of two long term natural archives in the southwestern part of the western siberian plain bchron age models based on 17 ams dates allowed us to determine a chronology of changes in properties of lake and peat deposits significant changes in the holocene were identified according to geochemical indices accumulation rates and compositions of the plant macrofossils of sediment cores in lake kyrtyma and oshukovskoe peat bog sediments with a low content of organic matter and maximum weathering accumulated in the late glacial below the border of the holocene the transition to the holocene manifested as a black organic gyttja with ostracods and marked warming 12 11 2 ka bp at about 11 2 10 1 ka bp it was replaced by the preboreal oscillation subsequent changes in lake sedimentation were associated with general warming and an unstable hydrological regime an increase in humidification 8 2 ka bp was reflected by lake level rise and contributed to swamping of the watersheds the aridest holocene phase at 7 1 5 5 ka bp was reliably recorded by geochemical data but poorly reflected in the stratigraphy of both profiles subsequent cooling and the resulting decrease in evaporation began at 5 5 4 9 ka bp a pronounced cardinal shift in sedimentation conditions due to a gradual increase in precipitation was recorded at 4 9 2 8 ka bp though short term fluctuations towards dryness were also marked at 3 5 3 3 ka bp the most significant increase in humidification and cooling began at 2 8 ka bp geochemical indices in the lacustrine sediments are climate sensitive and allowing us to obtain enough reliable data associated with changes in sedimentation environments the stratigraphy of peat reflected the nuances of climatic changes less clearly and primarily demonstrated the stages of bog self development however sphagnum peat provided a better resolution record

geothermometry from 40ar39ar dating experiments abstract we have selected a variety of minerals from three basic intrusions within the high grade metamorphic terrane near haliburton ontario for k ar dating by application of 40 ar 39 ar incremental heating experiments we conclude that the discordant k ar mineral dates can best be explained by a slow cooling history from the stepwise heating experiments we calculated isotopic closure temperatures using dodson s theory for slow cooling and from these constructed a cooling curve this curve was then compared to independent constraints to test the overall validity of our procedures and assumptions the results are geologically reasonable insofar as 1 a the maximum calculated temperatures from hornblendes of 700 c are consistent with independent approximate metamorphic grid arguments 2 b the ar closure temperatures for biotites 350 400 c are consistent with independent evidence and 3 c minerals with older k ar dates have higher calculated closure temperatures the resultant geological cooling curve implies that a maximum temperature of 700 c was reached before 1000 ma ago and thereafter the temperature decreased via changes in uplift and cooling rates to below 200 c by 700 ma ago we have discovered that plutonic plagioclases are very sensitive indicators comparable to k felds pars of ar loss and therefore can usefully extend the range of application of the 40 ar 39 ar stepwise heating method we also describe experiments in which we have tested the effects on the ar systematics of acid leaching of plagioclases

sediment supply and channel morphology in mountain river systems 1 relative importance of lithology topography and climate 1 quantifying landscape scale variations in sediment supply to streams and rivers is fundamental to our understanding of both denudational processes and stream channel morpho dynamics previous studies have linked a variety of sediment supply proxies to climatic topographic or geologic factors but few have connected these directly to the characteristics of fluvial systems draining these landscapes here we correlate landscape controls on sediment supply to observed sedimentology and channel patterns through direct measurements of water and sediment fluxes in over 80 drainage basins ranging in area from 1 4 to 35 000 km2 in the northern rocky mountains usa these data show that the relative sediment supply defined by the bankfull sediment concentration is dominated by basin lithology while exhibiting little correlation to factors such as relief mean basin slope and drainage density bankfull sediment concentrations bed load and suspended load increase as much as 100 fold as basin lithology becomes dominated by softer sedimentary and volcanic rocks relative to basins with more resistant lithologies as bed load concentrations increase stream beds become less armored and bed load grain size coarsens at very high sediment concentrations bed surface subsurface and bed load grain sizes converge and a transition from single thread to to braided channel patterns is commonly observed

development of the global width database for large rivers river width is a fundamental parameter of river hydrodynamic simulations but no global scale river width database based on observed water bodies has yet been developed here we present a new algorithm that automatically calculates river width from satellite based water masks and flow direction maps the global width database for large rivers gwd lr is developed by applying the algorithm to the srtm water body database and the hydrosheds flow direction map both bank to bank river width and effective river width excluding islands are calculated for river channels between 60s and 60n the effective river width of gwd lr is compared with existing river width databases for the congo and mississippi rivers the effective river width of the gwd lr is slightly narrower compared to the existing databases but the relative difference is within 20 for most river channels as the river width of the gwd lr is calculated along the river channels of the hydrosheds flow direction map it is relatively straightforward to apply the gwd lr to global and continental scale river modeling

an abrupt ecosystem change in lake beloye southern western siberia palaeoclimate versus local environment abstract sediment structure rock magnetic and bio geochemical records obtained from sapropel core samples in lake beloye southern western siberia indicate an abrupt ecosystem change at 3 4 calibrated ka bp the lake changed from eutrophic to oligotrophic its vegetation from carbon fixing macrophytic angiosperms to calcium fixing macrophytic algae and angiosperms and as a result the type of sedimentation shifted from peaty sapropel to carbonate rich sapropel those changes could be induced by climate which was warmer and wetter before 3 4 ka bp and cooler and drier after this nevertheless our data show that those ecosystem changes occurred when the lake became shallower to get about 1 m depth and started to freeze to the bottom in winter time the full freezing of the lake led to the deposition of carbonates which resulted in i death of carbon utilizing macrophytic angiosperms and ii winter precipitation of calcium carbonate in summer additional portions of ca 2 and hco 3 ions come into the lake from the surrounding caco 3 rich loess sediments with ground water the beloye lake thus represents an example of interrelated regional climatic and local ecological factors which combination resulted in the 3 4 cal ka bp dramatic change of its ecosystem

seasonal patterns of suspended sediment transport in an abandoned farmland catchment in the central spanish pyrenees the suspended sediment response of a small catchment subjected to farmland abandonment and subsequent plant recolonization was studied in relation to its hydrological functioning the analysis of data over a seven year period demonstrated that suspended sediment yield was greatly influenced by the occurrence of intense low frequency events greater amounts of suspended sediment were exported during spring when the catchment was hydrologically more active rainfall intensity and baseflow at the start of a flood event had a strong influence on the sediment response suggesting that several hydrological processes were active within the catchment ssc suspended sediment concentration q hysteretic loop analysis at the event scale aided understanding of the sedimentological and hydrological behaviour of the catchment during the study period the ssc q loops showed a high degree of seasonality and two main patterns strongly related to catchment wetness were distinguished when the catchment was dry mainly during summer and the beginning of autumn the predominant process was infiltration excess runoff over sparsely vegetated areas close to the main channel under these conditions floods exhibited a counter clockwise hysteretic loop and were characterized by a small streamflow response short duration and high ssc under wet conditions mainly during winter and spring saturation excess runoff was increasingly dominant over vegetated areas under these conditions floods exhibited a clockwise hysteretic loop and were characterized by a larger streamflow response longer duration and higher suspended sediment yield the lower ssc during the falling stage of the hydrograph is likely to be due to dilution effects related to the contribution of clean water resulting from enlargement of the saturated areas together with an increase in the baseflow discharge copyright 2009 john wiley sons ltd

a network based framework for identifying potential synchronizations and amplifications of sediment delivery in river basins long term prediction of environmental response to natural and anthropogenic disturbances in a basin becomes highly uncertain using physically based distributed models particularly when transport time scales range from tens to thousands of years such as for sediment yet such predictions are needed as changes in one part of a basin now might adversely affect other parts of the basin in years to come in this paper we propose a simplified network based predictive framework of sedimentological response in a basin which incorporates network topology channel characteristics and transport process dynamics to perform a nonlinear process based scaling of the river network width function to a time response function we develop the process scaling formulation for transport of mud sand and gravel using simplifying assumptions including neglecting long term storage and apply the methodology to the minnesota river basin we identify a robust bimodal distribution of the sedimentological response for sand of the basin which we attribute to specific source areas and identify a resonant frequency of sediment supply where the disturbance of one area followed by the disturbance of another area after a certain period of time may result in amplification of the effects of sediment inputs which would be otherwise difficult to predict we perform a sensitivity analysis to test the robustness of the proposed formulation to model parameter uncertainty and use observations of suspended sediment at several stations in the basin to diagnose the model the proposed framework has identified an important vulnerability of the minnesota river basin to spatial and temporal structuring of sediment delivery

factors controlling specific sediment yield in the upper indus river basin northern pakistan estimates of sediment yield are essential in water resources analysis modelling and engineering in investigations of continental denudation rates and in studies of drainage basin response to changes in climate and land use the availability of high resolution global environmental datasets offers an opportunity to examine the relationships between specific sediment yield sysp and drainage basin attributes in a geographical information system gis environment this study examines sysp at 14 long term gauging stations within the upper indus river basin twenty nine environmental variables were derived from global datasets the majority with a 1 1 km resolution the sysp ranges from 194 to 1302 t km 2 yr 1 for sub basins ranging from 567 to 212 447 km2 the high degree of scatter in sysp is greatly reduced when the stations are divided into three groups upper glacierized sub basins lower monsoon sub basins and the main indus river percentage snow ice cover lcs emerges as the single major land cover control for sysp in the high mountainous upper indus river basin a regression model with percentage snow ice cover lcs as the single independent variable explains 73 4 of the variance in sysp for the whole indus basin a combination of percentage snow ice cover lcs relief and climate variables explains 98 5 of the variance for the upper glacierized sub basins for the lower monsoon region a regression model with only mean annual precipitation p explains 99 4 of the variance along the main indus river a regression model including just basin relief r explains 92 4 of the variance in sysp based on the r2adj and p value statistics the variables used are capable of explaining the majority of variance in the upper indus river basin copyright 2007 john wiley sons ltd

the neoproterozoic pan african basement from the alpine lower danubian nappe system south carpathians romania abstract the south carpathians which were thrust to the moesian platform in the alpine orogeny late cretaceous to tertiary include the danubian nappe system the danubian pre alpine basement comprises two variscan nappes each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an ordovician devonian volcano sedimentary cover no lithological correlation can be established between the pre ordovician basements of these two units the metamorphic basement from the first variscan nappe the dr gsan group is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons the banded structure of the amphibolites together with their geochemistry suggests a volcano sedimentary sequence zircon u pb data on an intercalated augen gneiss have given an age of 777 3 ma for the emplacement of the protolith of this gneiss nd model ages t dm for the amphibolites range from 717 ma to 817 ma at 777 ma nd values cluster is at 8 3 to 9 8 and sr initial ratios range between 0 7007 and 0 7023 indicating an oceanic origin without continental crust contamination major and trace elements from the dr gsan amphibolites consistently display an island arc signature with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low k calc alkaline one the dr gsan terrane is similar to the early pan african juvenile terranes of the sahara the basement of the second variscan nappe the lainici p ius group is made up of metasedimentary rocks mainly quartzites marbles and graphitic mica gneisses cut by early leucogranitic dykes medium k calc alkaline and alkali calcic mainly granitic plutons and late medium k porphyry diorite dykes this magmatism can be bracketed between 588 ma and 567 ma u pb zircon ages the best preserved pluton tismana 567 ma old displays a composite alkali calcic very high k calc alkaline magmatic sequence ranging from gabbro diorite to monzogranite including an ultramafic pod ages and geochemical signatures resemble the saharan late pan african granitoids the existence of late precambrian partly juvenile terrains is thus confirmed within the basement of south carpathians which renders then a segment of the european alpine belt that can be successfully compared to the pan african trans saharan belt

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

predicting natural base flow stream water chemistry in the western united states 1 robust predictions of stream solute concentrations expected under natural reference conditions would help establish more realistic water quality standards and improve stream ecological assessments models predicting solute concentrations from environmental factors would also help identify the relative importance of different factors that influence water chemistry although data are available describing the major factors controlling water chemistry i e geology climate atmospheric deposition soils vegetation topography geologic maps do not adequately convey how rocks vary in their chemical and physical properties we addressed this issue by associating rock chemical and physical properties with geological map units to produce continuous maps of percentages of cao mgo s uniaxial compressive strength and hydraulic conductivity for western united states lithologies we used catchment summaries of these geologic properties and other environmental factors to develop multiple linear regression lr and random forest rf models to predict base flow electrical conductivity ec acid neutralization capacity anc ca mg and so4 models were derived from observations at 1414 reference quality streams rf models were superior to lr models explaining 71 of the variance in ec 61 in anc 92 in ca 58 in mg and 74 in so4 when assessed with independent observations the root mean square error for predictions on validation sites were all temperature precipitation soil atmospheric deposition vegetation amount of rock water contact topography

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

the blackspring ridge flute field south central alberta canada evidence for subglacial sheetflow erosion abstract the blackspring ridge bsr located in south central alberta canada is dominated by a prominent flute field flutes elongated streamlined depressions and ridges elongate streamlined hills are up to 15 km long and are composed of two material types in situ bedrock and in situ pre laurentide glaciation fluvial sand and gravel beds the preglacial beds are tertiary or early quaternary in age the beds are undisturbed maintain primary bedding structures and even maintain clast imbrication no till overlies the gravel beds although in places large granite boulder erratics lie on the surface indicating that ice was present in the region in the past because the ridges are composed of preglacial materials they are remnant erosional landforms rather than constructional landforms geomorphic and sedimentary evidence favor subglacial meltwater as the erosional agent rather than ice we suggest that the elevation of the bsr relative to basal ice would have resulted in confined subglacial meltwater flow with associated flow acceleration and increased scouring resulting in flute formation this meltwater stripped away any till cover leaving behind only a few boulders observations at the bsr flute field preclude the possibility that flutes and remnant ridges are the result of deformation of soft clayey beds

floodplain width adjustments in response to rapid base level fall and knickpoint migration abstract geomorphology has long been engaged in characterizing the form and understanding the evolution of floodplains this study primarily examines floodplain width in four tributaries to the minnesota river in southern minnesota namely the maple le sueur and blue earth rivers and seven mile creek the tributary systems are relatively young having formed after retreat of the wisconsinan ice sheet and are rapidly evolving in response to a base level fall of nearly 70 m 13 400 ybp as a result the lower reaches of all four river channels are aggressively incising this study applies a new freely available open code plug in for arcgis to measure floodplain width as a function of elevation above the geomorphic top of bank systematic changes are observed in all four systems above the steep incising knickzone reaches of each of the tributaries relatively wide and mostly unconfined floodplains are observed within the knickzone floodplains progressively narrow to between 25 60 of their width above the knickzone despite the fact that sediment loads increase significantly in the downstream direction a power law relationship is consistently observed between floodplain width and the ratio of local channel slope to contributing drainage area to about the negative one third power in all four rivers this same power law relationship is observed for two other rivers that differ significantly from our study systems in climatic and tectonic environment as well as base level history

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

analysis of factors determining sediment yield variability in the highlands of northern ethiopia in many developing countries sustainable land management and water resources development are threatened by soil erosion and sediment related problems in response to such threats there is an urgent need for improved catchment based erosion control and sediment management strategies the design and implementation of such strategies require data on erosion rates and understanding of the factors that control the delivery of sediment through the catchment system in this study reservoir sedimentation and corresponding catchment attribute data were used to investigate the major factors controlling sediment yield variability in a mountainous dryland region of northern ethiopia sediment yield data were acquired for representative 11 catchments above reservoirs geomorphological and anthropogenic catchment attributes were extracted for each reservoir from different sources including digital elevation models satellite images and field surveys different statistical analyses such as pearson s correlation principal components and multiple regression were implemented to analyze the relationship between sediment yield and catchment characteristics and to determine the major factors controlling the variability of sediment yield the results show that terrain form gully erosion surface lithology and land cover explain most of the variability in sediment yield among the catchments the implications of the results for relevant management intervention targeted at ameliorating the major causative factors of erosion are also outlined

cosmogenic 10be as a tracer for hillslope and channel sediment dynamics in the clearwater river western washington state we use the 10be concentration in alluvial sand and gravel to document hillslope exposure history and trace the reduction in grain size of river alluvium in the clearwater river basin western washington state clearwater tributary basins wilson creek wc 6 km2 and east fork miller creek efmc 12 km2 were each sampled in headwater and downstream sites for 10be in alluvial sand 0 25 0 50 mm and gravel 22 6 90 mm grain size distributions were determined at each sampling site as well as at several locations along the main stem of the clearwater river channel and watershed geomorphology were quantified using long profile modeling and related morphometric analyses we found that the 10be concentrations differ significantly between the two grain size fractions at all four sampling locations at both headwater sites the gravel exhibits 25 lower 10be concentrations compared to the sand similarly the downstream site of lower wc exhibits 55 lower 10be concentration in the gravel compared to the sand in contrast the gravel from the downstream site on lower efmc exhibited 22 higher 10be concentration in the gravel compared to the sand the disparity in 10be concentration at the wc sites is best explained by shielding of the coarser grain size fraction and its delivery to the channel by deep seated landslide processes more intense landsliding in the downstream wc site is consistent with the increased disparity of 10be between the sand and gravel fractions at that site the inverse relationship between the sand and gravel 10be concentrations at the headwater efmc site is best explained by a sediment provenance mechanism where the hillslope weathering rate exceeds the down slope transport rate for this particular basin the inverse grain size dependency gravel sand observed in the downstream efmc site requires a more complex interplay between hillslope and channel processes including cobble weathering and grain size reduction during fluvial transport resulting in a dilution of the 10be signal in the sand fraction downstream these results underscore the importance of geomorphic consideration and the grain size sampled in the correct interpretation of basin average erosion rates

precambrian tholeiitic dacitic rock suites and cambrian ultramafic rocks in the pennine nappe system of the alps evidence from sm nd isotopes and rare earth elements major element trace element and sm nd isotope analyses were made of polymetamorphic hornblendefelses plagioclase amphibolites and banded amphibolites from the berisal complex in the simplon area italy switzerland to determine their age origin and genetic relationships in light of major and rare earth element data the hornblendefelses are inferred to have originally been pyroxene rich cumulates the plagioclase amphibolites and the dark layers of the banded amphibolites to have been tholeiitic basalts and the light layers dacites the sm nd isotope data yield isochron ages of 475 81 ma for the hornblendefelses 1 018 59 ma for the plagioclase amphibolites and 1 071 43 ma for the banded amphibolites the 1 ga magmatic event is the oldest one ever found in the crystalline basement of the pennine nappes the sm nd isotope data support the consanguinity of the tholeiitic dark layers and the dacitic light layers of the banded amphibolites with the tholeiitic plagioclase amphibolites and the ultramafic hornblendefelses

temporal and spatial variations of sediment rating curves in the changjiang yangtze river basin and their implications the natural hydrologic regime of the changjiang yangtze river in china has been disturbed considerably by intensified human activities over the past five decades in this study sediment rating curves were analyzed based on monthly data of water discharge and suspended sediment concentration at stations in the upper yichang station middle hankou station and lower datong station reaches of the changjiang in different periods from 1955 to 2007 temporal and spatial variations of the sediment rating curves were analyzed with respect to the impact of human activities and watershed characteristics results indicate that human disturbances have had a substantial impact on sediment rating parameters with the magnitude of the impact related to the scale of the river sections as indicated by the sediment rating parameters the sediment transport regimes between the upper and the mid lower reaches differ significantly in particular the impoundment of the three gorges dam in 2003 changed the sediment transport regimes in the upper and mid lower reaches of changjiang into similar regimes characterized by a decrease in the sediment transport capacity of high water discharge furthermore the sediment rating curve at the datong station in 1955 1968 was applied to estimate the potential sediment load 1969 2007 in the absence of human influences the mean annual sediment deficit caused by human activities has increased from 80 mt yr 1969 1985 to 250 mt yr 2003 2007 this indicates that intensified human activities in the changjiang basin especially the construction of the three gorges dam have altered the natural sediment transport process and have thus become a dominant force in changjiang sediment delivery to the sea

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

machine learning predicts reach scale channel types from coarse scale geospatial data in a large river basin author s guillon herva byrne colin f lane belize a sandoval solis samuel pasternack gregory b

alpine polyphase tectono metamorphic evolution of the south carpathians a new overview abstract the main terrains involved in the cretaceous tertiary tectonism in the south carpathians segment of the european alpine orogen are the getic supragetic and danubian continental crust fragments separated by the severin oceanic crust floored basin during the early middle cretaceous times the danubian microplate acted initially as a foreland unit strongly involved in the south carpathians nappe stacking multistage folding thrusting events uplift erosion and extensional stages and the development of associated sedimentary basins characterize the south carpathians during cretaceous to tertiary convergence and collision events the main cretaceous tectogenetic events responsible for contraction and crustal thickening processes in the south carpathians are mid cretaceous austrian phase and latest cretaceous laramide or getic phase in age the architecture of the south carpathians suggests polyphase tectonic evolution and mountain building and includes from top to bottom the getic supragetic basement cover nappes the severin and arjana cover nappes and danubian basement cover nappes all tectonically overriding the moesian platform the severin nappe complex including obarsia and severin nappes with late jurassic early cretaceous ophiolites and turbidites is squeezed between the danubian and getic supragetic basement nappes as a result of successive thrusting of dismembered units during the inferred mid to late cretaceous subduction collision followed by tectonic inversion processes early cretaceous thick skinned tectonics was replaced by thin skinned tectonics in late cretaceous thus the former middle cretaceous austrian nappe stack and its albian lower senonian cover got incorporated in the intra senonian laramide getic stacking of the getic supragetic severin arjana nappes onto the danubian nappe duplex the two contraction events are separated by an extensional tectonic phase in the upper plate recorded by the intrusion of the banatitic magmas 84 73 ma the overthrusting of the entire south carpathian cretaceous nappe stack onto the fold thrust foredeep units and to the moesian platform took place in the late miocene intra sarmatian times and was followed by extensional events and sedimentary basin formation

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

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

fluvial processes morphology and sediment budgets in the coon creek basin wi usa 1975 1993 sediment budget processes in coon creek wisconsin from 1975 to 1993 changed only moderately generally continuing the trends that were evident in 1975 perhaps most importantly sediment yield to the mississippi river appears to be unabated with much of this clearly coming from storage loss especially stream bank erosion vertical accretion continued on the lower new floodplains inset within their meander plains in tributaries and the upper main valley the lower main valley also continued to aggrade but at the rate of about 6 of that occurring in the 1920s and 1930s the major revision from earlier studies is that the upper main valley is a less significant net source of sediment than previously thought and the earlier prognostications of it being a significant net source of sediment in the future may be wrong perturbations have been caused by changes of riparian vegetation and much more importantly by the introduction of fish shelter structures and protected cut banks along the stream system reaching downstream to the end of the upper main valley because these structures do not permit natural stream migration bank erosion and downstream sediment transfer the coon creek basin has lost much of its suitability as a natural laboratory of fluvial processes

landscape evolution valley excavation and terrace development following abrupt postglacial base level fall many high latitude fluvial systems are adjusting to base level changes since the last glaciation channels that experienced base level fall may still be incising often through glacial diamictons tills these tills can be quite competent behaving more like weak bedrock than unconsolidated sediment and erode at a fast pace thus providing a unique opportunity to test models of channel incision and knickpoint migration in transient systems here we integrate light detection and ranging lidar topography strath terrace chronology and numerical modeling to determine knickpoint migration and incision history of the le sueur river in central minnesota usa results indicate that the le sueur river is best modeled as a detachment limited channel with downstream coarsening related to lag clasts from tills playing a critical factor in longitudinal profile development the le sueur river meanders as it incises so we coupled the best fit incision model to a meander model to determine valley excavation history the excavation history was used to determine a natural background erosion rate prior to land use changes associated with settlement and agricultural expansion in the mid 1800s we compared background fine sediment silt and clay erosion rates with historic decadal average annual suspended loads results show that modern fine sediment contributions from sources associated with valley excavation are three times higher than modeled presettlement loads recent changes in hydrology associated with land use and climate change have increased flows in rivers leading to higher sediment loads not just from field erosion but from increased bank and bluff erosion in the deeply incised valleys

1 57 ga magmatism in the south carpathians implications for the pre alpine basement and evolution of the mantle under the european continent abstract chemical and isotopic analyses of amphibolites and gneisses from the oldest lithostratigraphic group in the south carpathians produce new insights regarding the chronology and evolution of the mobile proterozoic crust in central eastern europe these results date an episode of magmatism related to oceanic crust consumption reveal a period of continental stabilization and put constraints on the underlying mantle composition amphibolites from the cump na group have their origin in basalts chemically similar to island arc tholeiites a whole rock isochron age of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand

contrasting mountain and piedmont dynamics of sediment discharge associated with groundwater storage variation in the biobio river supply and transport of sediment in catchments involve processes with fundamental consequences for river management land use and the prediction of climate driven sediment fluxes in the present study we addressed spatial variability in the water routes through the surface and subsurface of a catchment and the suspended sediment discharge qs over a mountain piedmont system we analyzed daily suspended sediment concentration cs and water discharge q measurements at stations located in different topographic settings mountain and piedmont in the biobio river basin southern central andes 37 39 s in steep catchments the q versus qs relationship has a marked seasonal hysteresis in the piedmont qs is proportional to q with no seasonal hysteresis the contrast in the hysteresis pattern between catchments with different topographies is explained by differences in the routing of rainfall derived water in the piedmont most of the rainfall is converted into surface runoff because the water table is near the surface in the mountains groundwater storage results in large seasonal variations in the proportion of q that flows at the surface and transports sediment from the hillslopes producing hysteresis by separating the total q into two components direct discharge qd and base flow qb we observed the response of qs to the fraction of water that quickly leaves the catchment after a rainfall event qd similar results between the mountain and piedmont and the absence of hysteresis simplify the behavior of qs into a linear relationship with qd over the entire catchment and lead us to propose that sediment mobilization to the river along the biobio catchment is primarily controlled by overland flow our findings highlight the importance of an adequate hydrological model for understanding the erosion and transport processes of a catchment and which can be applied to other natural and modeled mountain piedmont systems

interplay between spatially explicit sediment sourcing hierarchical river network structure and in channel bed material sediment transport and storage dynamics understanding how sediment moves along source to sink pathways through watersheds from hillslopes to channels and in and out of floodplains is a fundamental problem in geomorphology we contribute to advancing this understanding by modeling the transport and in channel storage dynamics of bed material sediment on a river network over a 600 year time period specifically we present spatiotemporal changes in bed sediment thickness along an entire river network to elucidate how river networks organize and process sediment supply we apply our model to sand transport in the agricultural greater blue earth river basin in minnesota by casting the arrival of sediment to links of the network as a poisson process we derive analytically under supply limited conditions the time averaged probability distribution function of bed sediment thickness for each link of the river network for any spatial distribution of inputs under transport limited conditions the analytical assumptions of the poisson arrival process are violated due to in channel storage dynamics where we find large fluctuations and periodicity in the time series of bed sediment thickness the time series of bed sediment thickness is the result of dynamics on a network in propagating altering and amalgamating sediment inputs in sometimes unexpected ways one key insight gleaned from the model is that there can be a small fraction of reaches with relatively low transport capacity within a nonequilibrium river network acting as bottlenecks that control sediment to downstream reaches whereby fluctuations in bed elevation can dissociate from signals in sediment supply

near channel versus watershed controls on sediment rating curves predicting riverine suspended sediment flux is a fundamental problem in geomorphology with important implications for water quality land and water resource management and aquatic ecosystem health to advance understanding we evaluated environmental and landscape factors that influence sediment rating curves srcs we generated srcs with recent total suspended solids tsss and discharge data from 45 gages on 36 rivers throughout the state of minnesota usa watersheds range from 32 to 14 600 km2 and represent distinct settings regarding topography land cover and geologic history rivers exhibited three distinct src shapes simple power functions threshold power functions and peaked or negative slope functions we computed src exponents and coefficients describing the steepness of the relation and the tss concentration at median flows respectively in addition to quantifying watershed topography climate hydrology geology soil type and land cover we used lidar topography to characterize the near channel environment upstream of gages we used random forest models to analyze relations between src parameters and attributes of the watershed and the near channel environment the models correctly classify 78 of src shapes and explain 37 60 of variance in src parameters we find that src steepness exponent is strongly related to near channel morphological characteristics including near channel relief channel gradient and presence of lakes along the local channel network but not to land use in contrast land use influences tss concentrations at moderate and low flow these findings suggest that the near channel environment controls changes in tss as flows increase whereas land use drives median and low flow tss conditions

40ar 39ar dating of the inner carpathians variscan basement and alpine mylonitic overprinting abstract the 40ar 39ar dating method has been applied to mylonitic rocks from the carpathian mountains these are variscan metamorphic and magmatic rocks that were overprinted during the alpine orogeny the inner western carpathians are conventionally described as a nappe pile formed by northward movement and then subjected to intense strike slip and normal faulting resulting in the formation of mylonitic rocks precise stratigraphie ages provide clear constraints for the geodynamic interpretation related to the succession of alpine events such as the pre gosauian phase during the turonian 90 ma the 40ar 39ar method allows to define the age of the ancient variscan basement and the ages of the alpine overprinting in the high and low tatras mineral ages of around 340 350 ma are yielded by gneisses micaschists and amphibolites providing a younger limit for the variscan metamorphism the emplacement cooling of the variscan granites is defined between 305 and 335 ma these rocks are overprinted by several alpine tectonothermal events the major events are dated at 65 and 86 88 ma during which the mylonites were generated an older event around 140 ma earlier defined by the rb sr method is now confirmed by the 40ar 39ar method dating of phengites extracted from high pressure metamorphic triassic rocks from the kosice area yields new data for the age of this event at 155 ma