the chronology of holocene alluvial sediments from the wetterau germany provided by optical and 14c dating holocene floodplain chronologies are often hard to establish the principal limitation being the scarc ity of organic remains in the present study optical dating of flood loam was carried out in

changes in antarctic bottom water properties in the western south atlantic in the late 1980s data collected in 1988 1989 as part of the south atlantic ventilation experiment have been combined with the historical database to study the circulation and water mass variability of the abyssal water in the argentine basin a map of potential temperature at 4000 m used as an indication of geostrophic shear defines a south and western intensified crescent shaped abyssal recirculation within this recirculation and its northward extension to the brazil basin antarctic bottom water aabw properties have undergone two modifications during the 1980s 1 the water mass cooled 0 05 c and freshened 0 008 in salinity ratio on surfaces of constant density 2 the densest layer of aabw was altered to less dense water through mixing or advection out of the study area this water mass change does not appear to have affected the flow pattern data collected in 1983 and 1988 to the north in the brazil basin show penetration of the freshwater mass in the deep western boundary current to between 18 s and 10 s indicating very rapid propagation of the anomaly from the argentine basin into the brazil basin as a deep western boundary current it is suggested that open ocean convective events within the weddell sea contributed to the change in aabw documented here

phases of soil erosion derived colluviation in the loess hills of south germany in south germany soil erosion is as old as farming and dates back to early neolithic times its sedimentary products form thick colluvial and alluvial sediment bodies in all drainage basins numerous local studies exist but the extrapolation of findings from local case studies to a regional scale has been problematic here a graphical approach is used for frequency analysis of existing data a frequency distribution for optical dates on colluvial sediments from the beginning of agriculture until 1200 ad was constructed by 1 representing the optical ages by gaussian distributions and 2 summing all the single curves the resulting graph clearly shows phases of increased colluviation during periods of stronger human impact a first significant increase occurred during the bronze age during the iron age roman period and at around 800 ad distinct maxima appear in the distribution and highest frequencies are present towards the end of the analysed period at around 1100 ad conclusions that can be drawn from such an approach are limited by sampling bias and other factors but for the analysed period and on a regional and long term scale colluviation seems to have been mainly triggered by intensity of land use climatic fluctuations are of only secondary importance rainfall events that were sufficiently erosive to produce colluvial sediments occurred throughout the agricultural periods the limiting factor for colluvium production was sensitivity of the landscape to erosion and this is a result of land use d 2002 elsevier science b v all rights reserved

holocene alluvial sediment storage in a small river catchment in the loess area of central belgium abstract soil erosion and sediment deposition widely affect landscape development particularly in erosion prone areas with loess derived soils nevertheless until now few attempts were made to quantify soil losses and sediment storage over long centennial or millennial timescales in this study the holocene alluvial sediment storage in a small river catchment 52 km2 of the belgian loess belt is estimated and a preliminary sediment budget for the catchment is presented in the valley of the nethen river c 13 km long a detailed survey of the alluvial sediment archive was conducted hand augerings and percussion drillings were made along cross valley transects at 12 locations in the catchment ams 14c dating of peat samples provided a temporal framework for the interpretation of the cores results show that the thickness of holocene sediment deposits in the nethen valley is 4 to 6 m which corresponds to a total clastic sediment mass of 14 106 t stored in the valley bottom three alluvial units could be distinguished and associated with deposition phases from 9600 to 2900 b c 2900 b c to a d 1000 and a d 1000 to present in contrast to the older sediments units 1 and 2 deposits from the last 1000 year unit 3 contain little organic matter they are seldom intercalated with peat layers and devoid of tufa unit 3 reaches a thickness of c 2 m thereby representing 50 of the holocene sediment mass stored in the alluvial plain the mean sedimentation rate in the alluvial plain for this last phase is 26 t ha 1 a 1 which is about tenfold larger than the sedimentation rates calculated for the older holocene sediment units sediment supply towards the alluvial plain has therefore increased tremendously since medieval times these results are in contrast to dating results obtained for colluvial sediments in a nearby dry valley within the catchment of the nethen where soil erosion and sediment deposition started in the early iron age and was already substantial during the roman age this means that there is a time lag of about one millennium between the onset of high sedimentation rates in the upstream area and high deposition rates in the alluvial plain this is probably caused by a change in coupling sediment connectivity between the plateau slopes and rivers as soil erosion proceeds first the dry zero order valleys in the catchment act as sediment traps and only after these are filled sediment reaches the floodplains the preliminary sediment budget for the nethen catchment illustrates that 50 of the sediment that was eroded during the holocene was stored in colluvial deposits which are mainly located on footslopes and in dry valley bottoms another 29 of the sediment mass is stored in the alluvial plain

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

spatio temporally variable response of fluvial systems to late pleistocene climate change a case study from central germany abstract the change of the earth s climate and anthropogenic forcing challenge catchment management as the deliberate use of the fluvial system s natural resources depends to some extent on the predictability of the system s variable sensitivity to external impacts the alluvial history of the wetter valley in central germany provides an example of the occurrence of a spatio temporally variable catchment sensitivity to the late pleistocene climate change empirical models that are based on sediment flux controls such as sediment supply transport capacity and gradient serve to explain differential floodplain construction during the early younger dryas the large scale basin upland morphology caused localised divergent cooling impacts and vegetation changes which generated reach scale variable sediment transport system states in the wetter valley the spatial arrangement of reach scale variable response is ascribed to the tectonically driven morphological configuration of the wetter catchment the crucial amplification of differential floodplain construction can be assigned to the spatially variable availability of a surplus of laacher see tephra particles in manner of a pulsed sediment input the ubiquitous tephra cover was previously deposited by the laacher see volcano event in the upper allerod thus the reach scale variable response during the early younger dryas can be deemed to have been climatically triggered but superimposed by an internally driven specific upstream catchment response the documented processes of late quaternary alluviation in the wetter valley imply the need for whole catchment approaches the latter are a prerequisite to reveal the occurrence and causalities of variable fluvial response in relation to external impacts that interact with internal morphological controls this is seen to be crucial to achieve an improved predictability of future environmental change in fluvial landscapes

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

lateglacial to holocene pedogenesis and formation of colluvial deposits in a loess landscape of central europe wetterau germany abstract loess areas in central europe have been settled since ancient times and are therefore predestined to archive information about both the paleoenvironment with and without human activities in gentle rolling loess landscapes distinct short and shallow valleys so called dells are prominent landscape elements that act as sediment traps the loess paleosol colluvium lpc sequence of gambach wetterau germany can be regarded as an exceptional sequence for lateglacial holocene pedogenesis and human impact in dry loess landscapes with the lpc sequence of gambach reflects climate controlled pedogenesis from ca 15 ka to 4 7 ka with the formation of a cambisol having some properties related to chernozem soil forming processes during the lateglacial a chernozem is developed in the deposits of the laacher see tephra which still show the influence of periglacial climate in their lowermost part the upper part of these deposits was relocated by colluvial processes at around 6 7 ka chernozem soil forming processes were still ongoing until 4 7 ka when these shifted to luvisol formation which is still active today since 4 7 ka extended land use with indications of agricultural fire use since at least 2 3 ka led to the formation of colluvial deposits combined with a topographic leveling of upland positions on a landscape scale the results of the formative element of humans on loess landscapes from the wetterau can also be taken as representative for around 9400 km2 of dry loess landscapes in central europe

anomalous temperatures in central scotia sea sediments bottom water variation or pore water circulation in old ocean crust we report low temperature gradients from 60 to 12 of geothermal and extrapolated temperatures offset from modern bottom water temperatures in sediments from the central scotia sea we examine possible causes bearing in mind similar anomalous measurements 18 years previously attributed at the time to instrumental error small temperature offsets 0 1 c may reflect short term bottom temperature variation within eddies of the antarctic circumpolar current low sediment temperature gradients may be caused by horizontal advection of cold water within the upper oceanic basaltic layer documented in younger ocean floor elsewhere or by northward encroachment of colder bottom waters from the antarctic peninsula shelf or weddell sea for several years prior to measurement

long period changes in the bottom water flowing through vema channel further details of the warming of bottom water flowing through the vema channel first reported by zenk and hogg 1996 are given because cross channel gradients of temperature are large and the channel is narrow careful analysis is required to determine whether or not the bottom water temperature minimum was adequately sampled by a particular station or cruise during a period from 1972 to 1996 at least 14 visits with quality hydrographic measurements have been made to the region of these 11 were judged successful and their data indicate an abrupt rise in potential temperature by 0 03 c from 0 18 c to 0 15 c in the early 1990s that has remained until the latest observation in the spring of 1996 although this observation is consistent with the report of warming of antarctic bottom water in the argentine basin by coles et al 1996 their associated conclusion that this water mass has also freshened by 0 008 psu on potential density surfaces is in contradiction with our finding of no measurable change

characterization and quantification of holocene colluvial and alluvial sediments in the valdaine region southern france this study presents a holocene sediment budget for the valdaine region located at the edge of the southern french pre alps holocene colluvial and alluvial deposition are quantified based on existing and new field data average sediment thickness values were calculated for different landscape units and available chronological data were used to make a time differentiated sediment budget total holocene colluvial deposition in the valdaine 334 km2 amounts 167 106 m3 while alluvial deposition in the roubion and jabron catchments in total 610 km2 including their catchment upstream the valdaine amounts 177 106 m3 especially colluvial deposition is high 0 75 106 g m2 compared with other catchments three major deposition periods 8500 2000 bc 700 bc ad 800 and ad 1200 2000 and two periods of relative hillslope stability with local fluvial incision 2000 700 bc and ad 800 1200 set the framework for a time differentiated sediment budget results show that depositional phases relate to intense

soil erosion in small catchments of the quercy region southwester france during the holocene erosion rates in two small catchments of the quercy region southwestern france calculated from colluvial deposits trapped in karstic depressions show a progressive increase during the holocene rates lower than 0 2 t ha 1 yr 1 have been found for the period that covers the beginning of the holocene to the early iron age the soils buried in the depressions testify to the permanence of a forest cover until the late neolithic and to its replacement by a herbaceous vegetation during protohistorical times probably as a consequence of forest clearance and increased grazing by cattle after the early iron age erosion increased significantly and the mean rate reached 0 8 t ha 1 yr 1 before mediaeval times the associated coarse grained crudely stratified colluvium is thought to reflect ploughing of the surrounding fields erosion rate increased up to c 1 3t ha 1 yr 1 during mediaeval and modem times

asynchronous holocene colluvial and alluvial aggradation a matter of hydrosedimentary connectivity based on optically stimulated luminescence osl and radiocarbon dating we establish chronologies of colluviation and alluviation in different floodplain sections of the northwestern wetterau loess basin germany similar to some other european valley floors holocene floodplain aggradation is marked by two important breaks 1 a millennial scale delay between the neolithic agricultural colluviation and floodplain aggradation in loess catchments agricultural colluviation started at about 7000 cal bp and anthropogenic floodplain aggradation only at about 2200 200 cal bp 2 a centennial scale variability in a temporary rise in rates of anthropogenic floodplain aggradation up to 3 6 1 7 mm yr during the high middle ages in directly neighbouring reaches independent archaeologic historic and vegetation records document distinct agricultural histories of hillsides and floodplains and highlight the importance of hydrosedimentary connectivity as compared with land use intensity the late iron age

a temporarily changing holocene sediment budget for a loess covered catchment central belgium abstract this study presents a holocene sediment budget for the nethen catchment a typical river catchment 55 km 2 in the belgian loess belt soil erosion and hillslope sediment storage are quantified by extrapolating detailed data obtained from soil profile truncation studies in three representative zero order sub catchments floodplain sediment storage is estimated by augerings along several transects across the main river and some of its tributaries the sediment budget shows that ca 38 of the soil eroded during the holocene is redeposited as colluvium on hillslopes and in dry valley bottoms another 23 of the eroded sediment is now stored as alluvium in the floodplain the remaining 39 or 21 10 6 mg is exported from the catchment dating of both colluvial and alluvial sediment deposits reveals that sediment dynamics between the hillslopes the dry valley bottoms and the floodplain behave highly non linearly before 500 bc sediment delivery from the hillslopes to the river channels was near maximum however since the onset of significant agriculture in the late bronze age early iron age increased rates of soil erosion are only reflected in the colluvium but not in the floodplain resulting in very low hillslope sediment delivery ratios from the medieval period onwards soil erosion increased even further mainly as a result of a further increase in agricultural land use but now also accelerated floodplain sedimentation took place due to an improved slope channel coupling and the management of floodplains

changes in sediment flux and storage within a fluvial system some examples from the rhine catchment the rhine river system can look back on a long history of human impact whereas significant anthropogenic changes to the river channel started only 200 years ago the impacts of land use have been felt for more than 7500 years here we review results from several case studies and show how land use change and climate impacts have transformed the fluvial system we focus on changes in sediment delivery pathways and slope channel coupling and show that these vary in time and depend on the magnitude of a rainfall event these changes must be accounted for when trying to use sediments as archives of land use change and climatic impacts on fluvial systems for example human impact is recorded in slope deposits only as long as rainfall intensity and runoff generation do not exceed the threshold for gullying similarly climatic impacts are only recorded in alluvium when both the landscape is rendered sensitive by human activities e g deforestation and rainfall thresholds for gullying are exceeded copyright 2003 john wiley sons ltd

holocene river and slope activity in the visoko basin bosnia herzegovina climate and land use effects alluvial and colluvial deposits were investigated at prehistoric tells close to the bosna river the chronology is based on ten radiocarbon ages five optically stimulated luminescence ages and on the archaeological record fluvial activity of the bosna river is indicated by overbank fines ca 5000 1000 bc 500 bc until today and a phase of lateral displacement of the river bed with subsequent channel fills ca 2000 500 bc early holocene fluvial activity was probably triggered by climatic variability but might have promoted the expansion of neolithic societies into the visoko basin mid to late holocene river activity occurred under increased climatic aridity but coincided with the expansion of prehistoric settlements to a wider area of the river basin on hard rocks in the adjacent mountainous areas the destruction of the thin soil cover in the mountains is discussed as a probable trigger for enduring subsequent river activity this is also indicated by a change in the geochemical signature of the alluvial sediments the proposed mechanism might explain the mid to late holocene river history in other regions the potential of geochemical analyses and diachronous high resolution archaeological records to make inferences regarding sediment sources and geomorphological processes is demonstrated copyright 2013 john wiley sons ltd

holocene landscape dynamics at the tell arslantepe malatya turkey soil erosion buried soils and settlement layers slope and river activity in a middle euphrates catchment alluvial and colluvial sequences were studied around the prehistoric tell arslantepe in 11 exposures and additional auger cores the chronology is based on 11 optically stimulated luminescence osl ages four radiocarbon ages and the embedded artifacts sediments contained wood charcoals providing information on former vegetation fluvial activity is documented during late glacial times 15 4 2 5 12 8 3 1 kyr and frequently after roman times slope and soil erosion occurred in the early 10 6 1 4 8 2 0 7 kyr and mid late holocene 6 7 0 9 5 4 0 7 4 7 0 7 2 6 0 2 2 5 0 2 1 9 0 2 1 8 0 2 kyr and during the last 1000 years the early holocene erosion phases pre date the so far established onset of settlement at the tell this either indicates an earlier onset of agricultural land use than assumed or climatic influence on erosion such as the 10 3 and 8 2 kyr climate events known from western europe the erosion phases at around 5 0 and 2 6 kyr could reflect geomorphic respon

holocene alluviation and hydrology in the upper thames basin a sequence of changing conditions for flooding and alluviation in the upper thames valley during the holocene has been identified and provisionally dated by the investigation of archaeological sites interstratified with alluvium archaeological survey suggests that the changes can be related to clearance and agricultural activity in the catchment area

river response to rapid holocene environmental change evidence and explanation in british catchments macklin m g jones a f lewin j 2010 river response to rapid holocene environmental change evidence and explanation in british catchments quaternary science reviews 29 13 14 1555 1576 sponsorship welsh assembly government and the higher education funding council for wales for funding this study through its support of the centre for catchment and coastal research at aberystwyth university

infrared stimulated luminescence dating of holocene colluvial sediments using the 410 nm emission abstract infrared stimulated luminescence irsl ages are reported for loessic colluvial sediments from wiesenbach south germany the samples were collected by boring and the polymineral fine grain fraction t4 1 i m was used for irsl investigations irsl spectra were measured prior to dating they show two major emissions at approx 560 and 410 nm the advantages of the subtraction dating technique aitken and xie 1992 using the 410 run emission are demonstrated the ages obtained are used for the reconstruction of the landscape development at the studied site subsequent to an erosion phase the deposition of a colluvium started prior to the roman period and increased to a maximum accumulation rate during the middle ages

establishing a holocene sediment budget for the river dijle abstract a holocene sediment budget was constructed for the 758 km 2 dijle catchment in the belgian loess belt in order to understand long term sediment dynamics hillslope sediment redistribution was calculated using soil profile information from 809 soil augerings which was extrapolated to the entire catchment using morphometric classes as large parts of the forests within the catchment prove to have undergone little or no erosion since medieval times a correction was applied for the presence of forests total holocene erosion amounts 817 66 mt for the catchment of which 327 34 mt was deposited as colluvium this corresponds with a net holocene soil erosion rate of 10 8 0 8 10 3 mg ha 1 for the entire dijle catchment alluvial deposits were studied through 187 augerings spread over 17 cross valley transects the total alluvial sediment deposition equals 352 11 mt or 42 of total eroded sediment mass results indicate that at the scale of a medium sized catchment the colluvial sediment sink is as important as the alluvial sediment sink and should not be neglected as a result the estimation of erosion through alluvial storage and sediment export would yield large errors dating of sediment units show an important increase in alluvial deposition from medieval times onwards indicating the important influence of agricultural activities that developed from that period mean sediment export rates from the catchment for the last 1000 1200 years range between 0 8 and 1 3 mg ha 1 a 1 and are consistent with present suspended sediment measurements in the dijle erosion for agricultural land for this period is 9 2 2 2 mg ha 1 a 1 sediment budgets for the various tributary catchments provide an insight in the sources and sinks of sediment at different scales within the catchment

geoarchaeology the four dimensional 4d fluvial matrix and climatic causality abstract geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales geoarchaeology in the uk over the last twenty years has flourished largely because it has gone beyond technological and scientific applications over the same period our ability to reconstruct the 3 dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances these have included the use of lidar laser imaging and radar to produce high resolution digital surface models the use of geophysics particularly ground penetrating radar and electrical resistivity to produce sediment depth models and the use of gis and data visualisation techniques to manipulate and display the data these techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3 dimensional volumetric models of the matrix of artefacts within fluvial deposits additionally a revolution in dating techniques particularly direct sediment dating by luminescence methods has enabled the creation of 4 dimensional models of the creation and preservation of these sites these 4 dimensional models have the ability to provide far more information about the processes of site creation preservation and even destruction and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change all improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales this allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level this data can then form a component of biocomplexity or agent based modelling which is becoming increasingly used in the natural sciences particularly ecology and geomorphology and which can be used to test scenarios including the impact on and response of hominins to abrupt or catastrophic environmental change whilst catastrophic events clearly represent the atypical they can be illuminating in revealing cognitive processes resulting in abandonment coping mitigation and innovation these points are exemplified using two in depth case studies one from the holocene geoarchaeological record of the river trent in central england and the other from the palaeolithic record from rivers in south west britain in the former the interaction between climate change and human activity is illustrated at the year to century timescale whilst in the other the timescale is millennial these case studies have deliberately been chosen to be as different as possible in temporal and spatial scale with the aim of examining the applicability of methodological and theoretical aspects of geoarchaeology lastly the paper considers the problem of scale in geoarchaeology and concludes it is process dependency which ultimately affects the questions we can ask and that questions of human response to climate change are fundamentally a product of materiality and cognitive processes this demands an in depth contextual approach to such questions rather than database driven assertions of causality

sediment budget for five millennia of tillage in the rockenberg catchment wetterau loess basin germany abstract the long cultivated loess landscapes of central europe provide the opportunity to explore the long term perspective on the evolution human natural sediment systems that are driven by human caused soil erosion processes a balance of spatially non uniform sediment production sedimentation and delivery was developed to highlight the quantitative dimensions and functioning of anthropogenic sediment redistribution in an undulating loess catchment of temperate europe the presented long term perspective relies on analysing pedostratigraphic and lithostratigraphic field data from 728 corings across 10 km 2 gis based data processing and the analysis of data uncertainty for a period of 5000 years of tillage anthropogenic sediment production equals 9425 t ha 1 of which 62 still reside as colluvial sediment on the catchment s hillsides the valley floors fulfil a sediment conveyor function through transporting 77 of the sediment received from the hillsides whole catchment yield to the contiguous higher order valley is 29 of the amount of anthropogenic sediment production the average catchment scale depth of soil truncation is 0 64 m while the remaining anthropogenic sediment cover has an average thickness of 0 46 m effective surface denudation 0 18 m the long term integral net erosion rate is 0 5 t ha 1 a 1 because of extensive sediment retention on hillsides the inherited human imprint on the soilscape eventually can be judged as beneficial rather than detrimental the ubiquitous cover of humic colluvia generally is more suitable for intense cultivation than pristine pedostratigraphies the sediment budget although build from a historic perspective also provides a plausible reference for realistic objectives of managing the soil erosion problem in human natural sediment systems

sensitivity of west and central european river systems to environmental changes during the holocene a review abstract sediment deposition in floodplains is an essential part of the sediment dynamics of a catchment these sediment dynamics can vary largely on a holocene time scale under the influence of driving forces such as land use and climatic variations in this paper we review the holocene floodplain sediment deposition history of rivers in west and central europe with special attention to the influence of climate and land use variability during the early holocene preboreal to atlantic period most floodplains were rather stable with limited floodplain aggradation after this initial phase of relative stability sedimentation rates increase during the middle and late holocene with often the most important deposition phase during the last 1000 to 2000 a the start of the increase in sedimentation varies spatially with an earlier start in the west france germany then in the east poland belarus ukraine while there are also local differences between regions which are settled early e g loess regions compared to later settled regions the sedimentation history of most floodplains can be linked to the local land use history while influence of climatic variations on floodplain aggradation is often reported to be of minor importance processes related to bedload are often reported to be more influenced by climatic events relationships between the driving forces and the sediment history are mainly based on synchronicity and there is seldom proof for a direct causal relationship future research should focus on a system based approach integrating the floodplain deposition in the entire sediment dynamics which includes also erosion colluvial deposition and export main research questions that need further attention include integration of system based concepts like landscape connectivity and buffering effects and also the assessment of the individual contribution of land use changes and climatologic variations on the sediment dynamics detailed sediment budget studies combined with modeling studies can make an important contribution to the understanding of floodplain sediment dynamics

impact of mediaeval agriculture on the alluvium in the san river headwaters polish eastern carpathians abstract an abrupt change in sedimentary processes occurs in the alluvium of the san river headwaters in the bieszczady mountains polish eastern carpathians older gravels are overlain with a sharp boundary by an extensive cover of sand and silt which is enriched in wood debris partly burned at the base the spatial distribution of the fine grained alluvium the wood debris composition and radiocarbon ages are best explained by a relatively sudden onset of deforestation and cultivation of the valley bottom and slopes in the middle of the second millennium this corresponds well with palynological archaeological and historical data on the agricultural colonisation of the valley

geomorphological facies reconstruction of late quaternary alluvia by the application of fluvial architecture concepts abstract this paper investigates the methodical implications the benefits and the constraints of applying the fluvial architecture concept to late quaternary shallow subsurface alluvial deposits the focus is upon a typical small to mesoscale valley floor of the temperate zone the studied reach is part of the river wetter catchment 517 km 2 in central germany a large number of studies on late quaternary terrestrial paleoenvironmental change of the temperate zone refer to such small to mesoscale catchments which are mostly occupied by mixed to suspended load rivers as in many cases mostly coring based evidence is available the observation and measurement is limited to lithology and lithofacies boundaries facies geometry must be inferred moreover in those environments differences in lithofacies are obscured by a significantly reduced range of grain size distributions an example of an ancient channel belt of late glacial to holocene age serves to delineate the methodical practice and utility of the fluvial architecture approach field evidence is obtained from detailed cross sectional surveys and comprises descriptions of lithofacies structural pedogenetical biotic features munsell color and total organic carbon magnetic volume susceptibility cross sectional lithofacies information is represented by spatially attributed scaled borehole logs the example also accentuates the need for applying additional stratigraphical methods such as physical age determination macrofossil analysis and tephrological stratigraphy these methods form the basis to discern stacked channel facies and derive a diachrony of channel forms thus the adapted architecture approach provides a significant surplus of information on channel dimensions ages and channel floodplain interconnectedness distinct fluvial landforms such as channels levees abandoned channels swamps and floodplain flats can be highlighted a number of methodical constraints are discussed in detail e g the sharpness of channel element geometry and the underlying ordering of bounding surfaces moreover it is shown that the analytical process resembles an iterative looping process that is led by deduction many geomorphologists and multi disciplinary floodplain researchers collect sedimentary data but still neglect utilizing the potential of architectural analysis the study makes clear that sedimentological approaches used in big river floodplains also apply to small valleys in fact the procedures for facies reconstruction need to be adjusted to each individual case study alluvial architecture analysis provides the tools to reveal interconnectedness or disconnectedness of channel near channel and overbank fluvial landforms which is essential for a geomorphological understanding of floodplain evolution

scale linkage and contingency effects of field scale and hillslope scale controls of long term soil erosion anthropogeomorphic sediment flux in agricultural loess watersheds of southern germany abstract agricultural landscapes with a millennial scale history of cultivation are common in many loess areas of central europe over time patterns of erosion and sedimentation have been continually modified via the variable imposition of anthropogenic discontinuities and linkages on fragmented hillslope sediment cascades which eventually caused the complicated soilscape pattern these field records challenge topographically oriented models of hillslope erosion and simple predictions of longer term change of spatial soilscape by cultivation activities a thorough understanding how soilscape patterns form in the long term however is essential to develop spatial concepts of the sediment budget particularly for the spatial modeling of anthropogenic hillslope sediment flux using gis in this study i used extensive datasets of anthropogenic soil truncation and burial in a typical undulating loess watershed in southern germany 10 km2 wetterau basin n of frankfurt a m spatial soilscape properties and historic sediment flux as caused by cultivation over seven millennia were evaluated by these data the soilscape pattern on the low gradient hillslopes of the study area was found to be marked by a statistical near random pattern of varying depth thickness of truncation and overthickened burial moreover it was shown that truncation and burial had developed independently from each other and did not correlate with either hillslope gradient or downslope curvature hence in the field any combination of few nearly preserved severely truncated or completely removed soil profiles with either no some or a thick sediment cover is present thereby lacking an obvious spatial pattern here i suggest putting long term change of the soilscape into a contextual anthropogeomorphic systems perspective that accommodates components of human induced soil erosion operating at different spatial scales to interpret the longer term spatial consequences at the hillslope system level in the study area system scale linkages are marked by the spatial intersection of a finer scaled managed field system with a broader hillslope scale framework of natural erosion controls in the low gradient study area field borders exert control over the spatial reference of soil erosion and sedimentation sites over time this brought about a growing historical and spatial contingency change to the soilscape because of arbitrary spatial changes of the field system which are inherent in its socio agricultural maintenance thus the very low gradient and low erosivity setting of the study area have singled out the agency of human induced spatial and connectivity controls and contingency for long term spatial hillslope sediment flux although these findings may be less true for different settings they allow for deriving a generic conceptual model of the linkages between natural and anthropogenic subsystems to interpret the effects of long term human induced sediment flux accordingly the resulting balance between on hillslope net storage and net delivery to streams is scaling with basic physiographic properties of erosivity and sedimentation as well as the degree of anthropogenic hillslope fragmentation for loess areas in europe variable fields are fundamental anthropogeomorphic units that determine appropriate system scaling for historic sediment flux analysis and constrain retrodiction and prediction of changing fluxes at a point and a time at watershed scales methodical implications address adequate sampling strategies to record soilscape change as a result of which a critical review of the applicability of the catena concept to long cultivated hillslopes in central europe was included finally the suggested refined generic model of long term human controlled sediment flux involves a number of research opportunities particularly for linking modeling approaches to long term field records of cultivation related change in the soilscape

fluvial system evolution and environmental changes during the holocene in the mue valley western france geomorphological and palaeoenvironmental research on holocene sedimentation in the mue valley provides evidence for fluvial system changes related to climate and human activities in normandy a poorly studied area of the paris basin the 24 km long valley bottom has been investigated through a systematic survey it shows an original longitudinal sedimentary pattern in relation with valley morphology and local geological controls minerogenic tufaceous and peaty deposits provide opportunities for multi proxy analyses and radiocarbon dating control sedimentation began around 9500 14c bp with silt deposition in a meandering system the boreal and the lower atlantic periods 8500 6000 14c bp were mainly characterized by unlithified calcareous tufa locally these deposits are very thick 7 to 13 m the tufa formed barrages across the valley bottom providing an autogenic control on upstream sedimentation during the upper atlantic period 6000 4700 14c bp the valley experienced a decrease in calcareous sedimentation and the development of organic deposits at the beginning of the subboreal 4700 3500 14c bp peat deposits expanded especially behind the tufa barrages the valley bottom was characterized by large marshy areas whereas the regional vegetation was progressively modified by human activities at the end of the subboreal 3300 3000 14c bp the infilling of the valley by calcareous silt was caused by an increase of river activity related to climatic and land use changes from the iron age and gallo roman periods 2800 1700 14c bp the valley bottom was filled by silty overbank deposits related to an increase of soil erosion the slopes and river system were once again coupled and the fluvial system functioned as a continuum from upstream to downstream the alluvial record of the mue valley reflects a broad regional pattern of environmental changes but presents particular features which highlight the need of longitudinal studies to take into account spatial and temporal discontinuities of holocene hydro sedimentary systems even in small order valleys

deep ocean temperature variations and implications for errors in seafloor heat flow determinations 1 the accuracy with which seafloor heat flow is determined depends on the temporal stability of bottom water temperature indirect tests for stability are provided most commonly by observing the uniformity of heat flow with depth this criterion is met to a high degree of certainty at two sites in the eastern north pacific ocean where colocated high quality probe and borehole heat flow data can be compared a more direct test for stability is provided by long term observations of bottom water temperature previously published records and new data show temperature variations of only a few hundredths of a degree at sites in the central and eastern north atlantic and the eastern north pacific resultant gradient perturbations are geothermally insignificant 5 mk m 1 at depths greater than 1 2 m below the seafloor consistent with the uniformity of heat flow with depth observed in these areas geothermally problematic bottom water temperature variations are observed or inferred in the western north and south atlantic and western south pacific variations range up to 0 15 k and are capable of producing gradient perturbations of up to 5 mk m 1 at depths as great as 5 m below the seafloor while these data are instructive their distribution is not adequate to provide general guidelines for estimating geothermal gradient perturbations data from shallower sites are needed in all oceans to define depth limits of acceptable bottom water temperature variability and from other deep ocean locations where near source bottom water transients or vigorous deep water circulation dynamics are likely to be present

a very large scale flow burst observed by the superdarn radars we examined the dynamics of the ionospheric plasma in the dayside sector by using the hf radar data at iceland west and at finland from 1100 to 1230 ut on september 5 1995 during that period the solar wind density was high and the imf was strongly southward the dayside magnetopause was highly compressed nearly to the geosynchronous orbit the two radars simultaneously detected a poleward flow burst in the noon sector which assuming uniformity of flow in the region of the data gap 1 5 mlt between the two radars showed a magnetic local time extent of 5 hours this local time extent is 2 to 3 hours wider than previous results the maximum poleward plasma velocity of the flow burst is 750 m s and the latitudinal size of the flow burst region is 100 to 200 km this flow burst region initially expanded in longitude up to 5 hours and then shifted poleward with a phase speed of 400 to 670 m s the flow burst has a duration of 20 min this large scale poleward flow burst is likely to be due to large scale reconnection occurring at the dayside magnetopause and subsequent convection as the magnetic field lines are transported across the polar cap

variations in sediment yield from the upper doubs river carbonate watershed jura france since the late glacial period abstract the upper doubs river valley is a 910 km2watershed feeding into lake chaillexon the lake was formed by a natural rockfall at the end of the bolling chronozone around 14 250 cal yr b p and since then has trapped material eroded from the watershed the filling process and variations in sediment yield have been investigated by mechanical coring seismic surveys and electric soundings the detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the late glacial period and holocene epoch and estimating the lake s entrapment capacity this enables us to determine the intensity of the erosion processes in relation to climate and environmental factors the bolling allerod interstade produced the greatest yields with mean values of 19 500 metric tons per calendar year t yr the younger dryas chronozone saw a sharp fall 8900 t yr that continued into the preboreal 2100 t yr clastic supply increased during the boreal 4500 t yr before declining again in the early atlantic 2400 t yr since then yields have risen from 4500 t yr in the late atlantic to 6800 t yr in the subboreal and 11 100 t yr in the subatlantic comparison of quantitative data with the qualitative analysis of the deposits and with the paleohydrologic curve of the watershed based on level fluctuations in lakes around chaillexon shows that climate was the controlling factor of sediment yield until the late atlantic from the late atlantic subboreal around 5400 cal yr b p 470014c yr b p and especially from the end of the subboreal chronozone and during the subatlantic chronozone 2770 cal yr b p 270014c yr b p present climatic constraints have been compounded by human activity related to forest clearing and land use

convection surrounding mesoscale ionospheric flow channels 1 we evaluate data from the european incoherent scatter eiscat svalbard radar esr and defense meteorological satellite program dmsp spacecraft coupled with data from the super dual auroral radar network superdarn polar cap convection patterns in order to study how the ionospheric convection evolves around a sequence of transient mesoscale flow channel events in the duskside of the cusp inflow region on a northwestward convection background for the interplanetary magnetic field imf by positive and bz negative a sequence of three eastward flow channels formed over the course of 1 hour in response to three sharp imf rotations to imf by negative and imf bz positive the first and third channels due to imf by negative periods of 13 min and 30 min respectively develop in a similar manner they span the entire esr field of view and widen poleward with increasing time elapsed since their first appearance until the imf rotates back the convection patterns are consistent with the line of sight data from the esr and dmsp within a 10 min adaption time the flow lines form a twin vortex flow with the observed channel being the twin vortices center flow the fitting algorithm was pushed to its limits in terms of spatial resolution in this study during portions of the channel events the suggested twin cell flow is not in agreement with our physical interpretation of the flow channels being reconnection events because cell closure is suggested across an anticipated nonreconnecting open closed boundary for these segments we present simulated patterns which have been arrived at by a combination of looking at the raw data and examining the fitted convection patterns

interannual variability of bottom temperatures in drake passage a continuous 4 year record of in situ bottom temperature measurements at 3690 m within drake passage 59 43 7s 55 29 5w from november 1992 to november 1996 is presented the record shows fluctuations of order 0 02 c over monthly periods throughout the 4 years but the annual mean temperature is the subject under discussion in this work between june 1994 and may 1995 the water sampled was of the order of 0 1 c cooler than the water sampled on either side of this time period this temporal temperature anomaly has only become apparent because of the availability of a continuous data set hydrographic data sampled from the same location as part of the world ocean circulation experiment sr1 repeat section provide potential temperature and salinity values that enable the bottom temperature record to be linked to variability in weddell sea deep water wsdw oxygen isotope measurements demonstrate that the year long period of cooler wsdw measured in drake passage is a signature of ice shelf water in the formation process of deep and bottom waters within the weddell sea

sensitivity of floodplain geoecology to human impact a holocene perspective for the headwaters of the dijle catchment central belgium floodplain deposition rates have increased markedly under influence of human impact throughout the late holocene in many western and central european catchments consequently the geomorphology and ecology of many floodplains changed in this study we discuss this human impact and its influence on the floodplain geoecology during the middle and late holocene for the headwaters of the dijle catchment located in the belgian loess belt the floodplain geoecology and the regional vegetation was reconstructed from sedimentological and palynological analyses an age depth model for the studied sequences was obtained using 17 radiocarbon dates statistical analyses of the pollen data cluster analysis and canonical correspondence analysis were used to detect changes in the pollen record our data show that until c 2500 cal bp human impact was nearly absent or localized with no discernible influence on the floodplain geoecology the floodplain was in a stable phase and consisted of a marshy environment where organic material could accumulate which is interpreted as the natural state of the floodplain from c 2500 cal bp onwards human impact gradually increased however only when human impact in the catchment crossed a threshold around 500 cal bp the floodplain geoecology changed with clearing of the alder carr forest the establishment of a single channel river and the dominance of minerogenic overbank sedimentation spatial variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differences in hillslope floodplain connectivity and local differences in human impact

non uniform and diachronous holocene floodplain evolution a case study from the dijle catchment belgium fluvial architecture changed under the influence of increasing human impact throughout the holocene in many north west european catchments typically peat formation in a marshy environment during the early and middle holocene is replaced by clastic overbank deposition in this study we show the importance of a detailed chronology of floodplain changes with an example from the belgian dijle catchment in total 45 radiocarbon ages from 15 alluvial sites were used cumulative probability functions were made of the radiocarbon ages from the base 16 samples and top 29 samples of the peat layer two alluvial sites were studied in detail the results indicate that the end of peat growth and the transition towards clastic overbank deposition is diachronous at the catchment scale ranging between 6500 and 500 cal a bp this diachronous pattern can be attributed to differences in timing and intensity of agricultural activities at the catchment scale or to differences in hillslope floodplain connectivity moreover in the broad floodplain of the main valley the top of the peat layer is even diachronous at cross section scale these results indicate that inferences on changes in sedimentation rate and floodplain changes should be based on a multi transect and multi core dating approach copyright 2014 john wiley sons ltd

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

colluvial and alluvial response to land use change in midland england an integrated geoarchaeological approach this paper presents geomorphic soils and palaeoecological data from a small sub catchment in the english midlands in an attempt to provide an integrated picture of holocene landscape change the area used has also been the focus of a multi disciplinary and long term archaeological survey raunds area project and so has a wealth of archaeological and historical data which can be related to the environmental record the paper combines these data much of which are only published in the archaeological literature with new interpretations based upon unpublished data and new data particularly from the hillslopes and new radiocarbon dating from the valley floor it is inferred that despite a long history of pastoral and arable agriculture since the neolithic bronze age colluviation on lower slopes significant soil redistribution and overbank alluviation only began to a measurable extent in the late saxon medieval period 9th century ad onwards it is suggested that this is due to a combination of land use factors principally the laying out of an intensive open field system and the establishment of villages combined with a period of extremes in climate well known throughout europe indeed the critical element appears to have been the social changes in this period that created this regionally distinctive landscape which happened to have a high spatial connectivity and facilitated intensive arable production with high tillage rates intense rainfall events during this period could therefore detach and mobilize high volumes of soil and the open field system facilitated transport to slope bases and valley floors the need for detailed and spatially precise land use data in order to interpret accelerated landscape change is stressed

recharge of a subglacial lake by surface meltwater in northeast greenland observations of rapid persistent elevation gains that occur on the ice surface above a subglacial lake as the lake is refilled with surface meltwater during the summer melt period in greenland show that surface meltwater may be trapped and stored at the bed of an ice sheet affecting ice dynamics downstream the discovery of a 70 metre deep collapse basin near the summit of the largest and most northerly peripheral ice cap of greenland and the use of high resolution stereo satellite imagery to monitor its evolution suggests that surface meltwater can be trapped and stored beneath the greenland ice sheet previously meltwater from the surface of the ice sheet had been assumed to drain efficiently through the basal hydrologic system during the summer melt period rapid persistent elevation gains occur on the ice surface above a subglacial lake as the lake is refilled with surface meltwater and stored at least on annual time scales these findings have potential implications for our understanding of ice sheet temperature and velocity in a warming climate surface meltwater production on large ice sheets is expected to increase if this water is delivered to the ice sheet base it may have important consequences for ice dynamics for example basal water distributed in a diffuse network can decrease basal friction1 2 and accelerate ice flow3 4 5 6 7 8 whereas channelized basal water can move quickly to the ice margin where it can alter fjord circulation and submarine melt rates9 10 less certain is whether surface meltwater can be trapped and stored in subglacial lakes beneath large ice sheets here we show that a subglacial lake in greenland drained quickly as seen in the collapse of the ice surface and then refilled from surface meltwater input we use digital elevation models from stereo satellite imagery and airborne measurements to resolve elevation changes during the evolution of the surface and basal hydrologic systems at the flade isblink ice cap in northeast greenland during the autumn of 2011 a collapse basin about 70 metres deep and about 0 4 cubic kilometres in volume formed near the southern summit of the ice cap as a subglacial lake drained into a nearby fjord over the next two years rapid uplift of the floor of the basin which is approximately 8 4 square kilometres in area occurred as surface meltwater flowed into crevasses around the basin margin and refilled the subglacial lake our observations show that surface meltwater can be trapped and stored at the bed of an ice sheet sensible and latent heat released by this trapped meltwater could soften nearby colder basal ice11 and alter downstream ice dynamics12 13 heat transport associated with meltwater trapped in subglacial lakes should be considered when predicting how ice sheet behaviour will change in a warming climate

holocene floodplain evolution of small rivers in the uplands of lower saxony germany abstract the holocene floodplain evolution of the river ilme and its distal tributaries in the uplands of lower saxony germany has been reconstructed by shallow corings arranged in cross and longitudinal profiles in those river reaches that drain agricultural land we differentiate three holocene fluvial units overlying the weichselian lower terrace a fine grained humus basal layer early middle holocene an older meadow loam 8th early 14th century and a younger meadow loam since 15th century intertongued with these sediments are alluvial fans and colluvia of two periods 1 neolithic to early medieval time 2 14th century in contrast forested floodplains are underlain by sand and gravel whereas on floodplains used as meadows a fine grained wiesensediment meadow sediment has accumulated since the 17th century the humus basal layer and the sandy gravel were both accumulated by braided rivers in the middle and lower reaches of the ilme floodplain the change to a meandering river happened when the older meadow loam accumulated as a result of woodland clearing and soil erosion in the early middle ages in the course of time the vertical accretion of the floodplain decreased as a result of the decreasing frequency of inundations itself caused by the increasing capacity of the river channel vertical accretion was nearly terminated in the late middle ages when a short climatic change caused fan and colluvial deposition since the 15th century the younger meadow loam accumulated most of it filling old channels in the wooded solling hills the change over from a braided river to a meandering river began in the 17th century but in those reaches with wooded floodplains the rivers are still braided

late holocene paleoecology and sedimentary history of a small lowland catchment in central england a variety of paleoecological and sedimentary techniques were used to investigate the storage of sediment within a small lowland catchment during the holocene radiocarbon dating of vertically accreted floodplain deposits allowed the calculation of inorganic accumulation rates these rates show a dramatic increase in sediment deposition during the late bronze age and early iron age 2900 2300 yr b p due to deforestation and cultivation of the catchment slopes and resultant soil erosion the soils within the catchment were susceptible to structural damage surface waterlogging and slope wash erosion from the calculated increases in sediment storage estimates of catchment erosion were made which vary from around 20 to 140 tons km 2 yr 1 the study of alluvial chronology at this scale can provide unique information on the source areas of holocene floodplain sediments and provide long term erosion rates

early human impact on soils and hydro sedimentary systems multi proxy geoarchaeological analyses from la narse de la sauvetat france we analysed the late holocene pedo sedimentary archives of la narse de la sauvetat a hydromorphic depression in the southern limagne plain central france where chronologically accurate studies

on the effects of thermal properties structure and water bottom temperature variation on temperature gradients in lake sediments in heat flow determinations it is customary to treat the surface temperature variation as a finite sum of fourier components the medium is assumed to be homogeneous or horizontally stratified wit

stratification of east west plasma flow channels observed in the ionospheric cusp in response to imf by polarity changes 1 during a period of predominantly north westward flow for imf bz negative and imf by positive a sequence of three distinct negative excursions of imf by resulted in a train of three eastward directed flow channels interleaved by westward flow enhancements propagating into the polar cap the high resolution of the eiscat svalbard radar data enables us to track formation and movement of the flow channels which are interpreted as a sequence of intermittent reconnection alternating between different reconnection sites our observations are consistent with the view that a new region of reconnected flux manifests as development of a distinct flow channel near the polar cap boundary and that successive events stay separated while pushing each other into the polar cap each flow channel will remain separated from neighboring channels mapping to different reconnection sites as long as the magnetic tension force with its associated field aligned current systems is maintained

impacts of sediment connectivity on holocene alluvial records across a mediterranean basin guadalentin river se spain two contiguous alluvial valleys maria and guadalupe sectors of the upper guadalentin river se spain show distinct holocene alluvial architecture cut and fill nested and stepped fill terraces revealing a strong control of valley morphology and bedrock barriers on sediment delivery storage and preservation the headwater valley maria sector preserves four morphosedimentary alluvial units corresponding to two palaeogeographic stages morphosedimentary unit msu1 the most extensive is a major depositional valley infill dominated by sand and silt texture showing three stratigraphic sets dated 9000 8500 5300 4800 4000 3000 cal bp this vertically stacked alluvial accumulation occurs upstream of a narrow bedrock channel that limited sediment connectivity with the downstream guadalupe sector between 3000 and 2350 cal bp a 15 m deep incision on msu1 occurred and subsequent cut and fill cycles generated three alluvial terraces dated at 2350 1900 cal bp msu2 1800 700 cal bp msu3 and post 400 years msu4 in the downstream valley guadalupe sector six flights of alluvial terraces msug1 to msug6 were formed by episodic aggradation and quasi continuous incision in response to baselevel changes of the lower guadalentin river during the holocene alluvial chronologies in these two contiguous valleys show out of phase sedimentation periods under low connectivity conditions 9 3 ka and in phase cut and fill cycles after valley re connection post 3 0 ka the late holocene alluvial activity periods also coincide with morpho stratigraphic data from the lower guadalentin indicating that fluvial connectivity throughout the catchment was only completed in the late holocene

microslag as a stratigraphic tracer to quantify floodplain processes lienne catchment belgium abstract this paper focuses on two objectives i the presentation of the methodology for using small sized iron slag called microslag as a stratigraphic marker to reconstruct the centennial scale floodplain evolution and ii the study of the geomorphic evolution of the ardennian rivers situated in the lienne catchment southern belgium by means of microslag evaluation 14c dating topographic surveys and sedimentological analysis using these data the floodplain history since the late pleistocene is reconstructed fine floodplain sedimentation and lateral mobility rates are estimated and channel incision phases are identified the first holocene erosion episode occurred during the bronze age archaeological data and historical sources indicate roman and high middle age occupations in the area but no evidence of erosion or increased floodplain sedimentation have been observed several peat layers have been dated in the chavanne floodplain to approximately 1000 bp and probably indicate very low anthropogenic activity and a high level of groundwater before 1000 ce the fluvial style of the ardennian rivers was probably different characterized by a low level forested floodplain which explains the presence of frequent peat layers within the alluvial sequences and abandoned channels from the eleventh century onwards a generalized increase in sedimentation rates occurred coinciding with a higher concentration of charcoal in the alluvium and also the formation of colluvial deposits analyses of slag concentrations allowed us to reconstruct the evolution of the floodplain topography in the lienne catchment the mean floodplain aggradation over the last several centuries is between 2 7 and 16 cm century depending on the study site such differences in floodplain sedimentation rates can be explained by several factors such as the distance to past cultivation areas the degree of woodland clearance flow velocities during floods and the incision of the riverbed during recent centuries which reduces the frequency of inundation and therefore sedimentation on floodplains

statistical patterns of high latitude convection obtained from goose bay hf radar observations we have derived patterns that describe the statistical interplanetary magnetic field imf dependencies of ionospheric convection in the high latitude region of the northern hemisphere the observations of plasma motion were made with the hf coherent backscatter radar located at goose bay labrador over the period september 1987 to june 1993 the area covered by the measurements extended poleward of 65 to a working limit of about 85 distributions of electrostatic potential have been derived and expressed as series expansions in spherical harmonics the patterns are the first derived from direct ground based observations of ionospheric convection that approach in completeness and level of detail the patterns derived in recent satellite studies rich and hairston 1994 weimer 1995 we show the dependence of the convection on imf angle in the gsm y z plane for three intervals of imf magnitude in this plane except for predominantly northward imf the convection is primarily two cell the dusk cell is larger in terms of both spatial extent and potential variation the effect of imf by is apparent in the global shaping of the cells and the orientation of the overall pattern in mlt for by by the dusk dawn cell is more round crescent shaped and the pattern more rotated toward earlier mlts the by effect on the nightside convection is pronounced and is hemispherically antisymmetric like the well known day side by effect for imf increasingly northward the convection trajectories on the dayside become increasingly distorted evolving through a three cell to a four cell circulation the additional cells appear on either side of the noon meridian and result in sunward flow the overall agreement with the results of the satellite studies is good and extends to quite fine detail in the case of the comparison with weimer 1995 there are significant differences with the statistical patterns derived from magnetometer measurements which tend to show domination by the dawn rather than the dusk cell

high resolution heat flow density in the lower congo basin 1 heat flow density hfd has been derived in the lower congo basin from 293 conventional probe measurements 424 oil exploration data and about 1 000 000 bottom simulating reflector bsr values each set of data provides independent estimates of temperature gradients associated with specific uncertainties and geographic distributions but a statistical comparison in overlapping domains shows a relatively good consistency in situ conductivity has been measured in conventional surveys and estimated from rock composition and porosity in oil exploration boreholes in the deep offshore measurements and estimates are consistently low and increase significantly toward the shelf domain thermal conductivity does not change significantly in the interval between the water bottom and the bsr and can be estimated from the surface measurements to provide an inference of hfd the combined sets of hfd in the lower congo basin cover the overall domain of the continental margin and a part of the oceanic domain high resolution imaging of the bsr by three dimensional 3 d seismic studies provides in addition good quality nominal resolution of 500 m in the deep offshore at short length scales on the order of kilometers large variations of hfd from 30 to 140 mwm 2 exist above salt diapirs and canyons related to heat refraction on the other hand no small scale effect related to fluid flow has been detected although active venting is known at larger length scale hfd in the deep offshore is different on both sides of the congo submarine channel 54 8 mwm 2 to the north and 48 12 mwm 2 to the south which are also characterized by different basin tectonic styles at the margin scale hfd is significantly different in the oceanic domain 42 3 mwm 2 the deep continental offshore 52 10 mwm 2 and the continental shelf 65 15 mwm 2 a progressive reduction of the radiogenic heat contribution in the extended continental crust is the more likely the cause of these differences mantle heat flow below the continental margin is consequently high compared to that expected 15 mwm 2 for old shields such as congo

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

towards determining the thermal state of old ocean lithosphere heat flow measurements from the blake bahama outer ridge north westem atlantic summary detailed suites of heat flow measurements have been completed at four sites on and to the east of the southern end of the blake bahama outer ridge in the north west atlantic on ocean crust which ranges in age from roughly 115 to 155 ma the principal purpose of these measurements was to compare instrumental techniques and to examine the decay of heat flow with age on old ocean floor multi penetration gradient measurements were made at the youngest site with a 2 5 m outrigger probe and multipenetration heat flow measurements at the other three sites with a new 3 5 m violin bow type instrument in addition at all four sites the gradient was measured using outriggers on a 9 m piston or gravity corer and conductivities were measured on the sediment recovered the average of thermal conductivities measured on cored sediments agreed to better than 2 per cent with the average of conductivities measured in situ at the oldest three sites such good agreement is surprising given the problems associated with making measurements on sediments recovered in cores the greatest measurement errors in determining heat flow were found to be caused by temperature disturbances generated by the piston coring process gravity coring reduced these disturbances but provided a less representative section for measuring thermal conductivity the violin bow probe which measures average interval conductivities in situ provided the most reliable heat flow determinations the accuracy of these determinations was limited primarily by the presence of thermal disturbances due to bottom water temperature variations the heat flow averages at all four sites are virtually identical they range from 47mw m 2 1 12 cal cm 2s 1 to 49mw m 2 1 17 cal cm 2s 1 with standard errors of less than 2 mw m 2 0 05 cal cm 2s 1 the constancy and the value of heat flow over lithosphere of this age and the local shallowing of depth with increasing age in the region containing the heat flow sites cannot be explained by either a simple plate or a boundary layer lithosphere cooling model the unexpectedly high heat flow and shallow depths may result from lithospheric thinning and perhaps dynamic forces associated with a thermal perturbation beneath the plate

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

holocene relief and soil changes in loess covered areas of south western germany the pedosedimentary archives of bretten bauerbach kraichgau based on infrared stimulated luminescence irsl dating of loess borne sediments a chronometry of holocene landscape evolution is established for a representative study site in the early settled kraichgau area in south western germany the results show that the gently rolling relief is due essentially to soil erosion and colluvial deposition triggered by humans cultivating the loess soils since the onset of agriculture in the neolithic period levelling of relief is accompanied by alterations in soil type patterns from haplic luvisols before the impact of humans over variably truncated luvisols with bt horizons prevailing at the slope surfaces in the middle ages to calcaric regosols characterizing both sites of erosion and accumulation since then the tremendous changes show that the effects of human activities have been recorded over thousands of years indicating an early anthropocene in a geomorphological and pedological sense most landscapes are probably more modified by humans than thought at first sight as the results show this recognition requires considering that current geomorphological and soil forming processes might work at different frequencies or magnitudes e g by changes of internal system thresholds such as increased erodibility following the complete erosion of a more resistant bt horizon and or in a different direction e g accumulation instead of erosion or sediment transport due to slope angles decreased by former deposition of colluvium than they would in the absence of a human controlled pre history

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

large scale imaging of high latitude convection with super dual auroral radar network hf radar observations the hf radars of the super dual auroral radar network superdarn provide measurements of the e b drift of ionospheric plasma over extended regions of the high latitude ionosphere with the recent augmentation of the northern hemisphere component to six radars a sizable fraction of the entire convection zone approximately one third can be imaged nearly instantaneously 2 min to date the two dimensional convection velocity has been mapped by combining line of sight velocity measurements obtained from pairs of radars within common volume areas we describe a new method of deriving large scale convection maps based on all the available velocity data the measurements are used to determine a solution for the distribution of electrostatic potential expressed as a series expansion in spherical harmonics the addition of data from a statistical model constrains the solution in regions of no data coverage for low order expansions the results provide a gross characterization of the global convection we discuss the processing of the radar velocity data the factors that condition the fitting and the reliability of the results we present examples of imaging that demonstrate the response of the global convection to variations in the interplanetary magnetic field imf in the case of a sudden polarity change from northward to southward imf the convection is seen to reconfigure globally on very short 6 min timescales

the black floodplain soil in the amoneburger becken germany a lower holocene marker horizon and indicator of an upper atlantic to subboreal dry period in central europe abstract in many sediment profiles of central european floodplains a black horizon is found between late glacial and middle to upper holocene sediments this horizon is rich in clay and humic material and is referred to as black floodplain soil bfs its widespread occurrence in the amoneburger becken near marburg hessen provides some new insights into the period and circumstances of its development as a polygenetic formation the bfs is of special importance for paleoecological and archeological research it was probably supplied with clay and humic substances from the surrounding terrestrial chernozemic soils and therefore it also has to be regarded as a sediment it developed mainly in the boreal and atlantic periods but did not gain its final characteristics until a following dry period which led to a lowering of the ground water table and widespread illuviation in the floodplains even in former lacustrine deposits

variability in fluvial geomorphic response to anthropogenic disturbance abstract humans have greatly impacted the processes and intensities of erosion sediment transport and storage since the introduction of agriculture in many regions around the world accelerated floodplain sedimentation can be related to increases in human pressure on the environment however the relation between the intensity of anthropogenic disturbance and the magnitude of change in fluvial sediment dynamics is not straightforward and often non linear here we review a number of case studies from contrasting environmental settings in the european loess belt the eastern mediterranean mountain ranges and the eastern usa detailed field based sediment archive studies and sediment budgets covering time periods ranging from 200 to over 5000 year as well as the use of pollen and sediment provenance techniques show that no overarching concept of changes in floodplain sedimentation following anthropogenic disturbance can be established slope channel dis connectivity controls the existence of thresholds or tipping points that need to be crossed before significant changes in downstream sediment dynamics are recorded following human impact this coupling can be related to characteristics of human pressure such as its duration intensity and spatial patterns but also to the geomorphic and tectonic setting furthermore internal feedback mechanisms such as those between erosion and soil thickness further complicate the story all these factors controlling the propagation of sediment from eroding hillslopes to river channels vary between regions hence only unique patterns of fluvial geomorphic response can be identified as a result unravelling the human impact from current day sediment archives and predicting the impact of future human disturbances on fluvial sediment dynamics remain a major challenge this has important implications for interpreting contemporary sediment yields as well as downstream sediment records in large floodplains deltas and the marine environment in terms of changes in the drivers of environmental change

human and climate impact on catchment development during the holocene geul river the netherlands interest in the holocene development of small to medium sized river catchments in western and central europe in relation to changes in land use and climate has increased over the past years in this study we reconstruct the holocene landscape development and fluvial dynamics of the geul river the netherlands and the main forcing mechanisms of environmental change field studies were carried out and we used osl and 14c dating methods to reconstruct the holocene valley development our study shows that 2 periods of deforestation during the roman period and the high middle ages led to severe soil erosion and increased floodplain sedimentation in the catchment of the geul river possibly combined with periods of increased wetness during the high middle ages alluvial fans have been active since the roman deforestation phase our results show that the geul catchment is highly sensitive to changes in land use

a constraint on the shear stress at the pacific australian plate boundary from heat flow and seismicity at the kermadec forearc new heat flow measurements and relocated hypocenters that constrain the subduction geometry of the pacific plate at the kermadec trench yield an estimate of shear stress on the thrust fault with the exception of a few relatively high values 60 mw m 2 on the upper forearc region near the active volcanic ridge most of the 64 heat flow values along two profiles across the forearc range from 20 to 40 mw m 2 corrections for bottom water temperature variations that caused nonuniform temperature gradients were required for most measurements the means of the most reliable values for the northern and southern profiles are 28 9 5 8 mw m 2 n 33 and 28 9 7 2 mw m 2 n 19 respectively and the measurements show no apparent systematic variation along the profiles over the range 50 to 150 km distance from the trench the means of the 10 values at each of two sites on the pacific plate seaward of the profiles are 57 2 6 3 and 60 2 6 6 mw m 2 redeterminations of focal depths and fault plane solutions of earthquakes in the vicinity of the heat flow profiles indicate thrust faulting on a plane dipping 17 2 calculated values of heat flow for a two dimensional analytical approximation to conduction through the upper plate diffusion into the downgoing slab and advection by that slab are consistent with either a uniform stress of 40 17 mpa along the thrust fault or stress increasing linearly at 0 5 0 2 mpa km 1 with distance from the trench axis the comparable scatter in the heat flow measurements about those calculated from these simple stress distributions does not show one to be a better approximation than the other