middle terrace deposits of the tagus river in alpiarca portugal in relation to early human occupation abstract the stratigraphy and sedimentology of the q3 middle terrace alluvial sequence in the lower tagus river valley portugal were studied near the village of alpiarca approximately 40 km upstream from the estuarine area two main stratigraphic units were recognized separated by an important uncomformity the lower gravels unit lg consists of intercalations of medium to coarse gravel deposits mainly quartzitic with coarse sandy matrix organized in tabular bodies the overlying upper sands unit us consists of tabular sandy channel deposits and overbank fines the latter containing well developed paleosols and backswamp deposits showing a general aggrading trend apparently with varying rates available data indicate that deposition of the us took place under temperate climatic conditions within us deposits are several paleolithic archaeological sites the lower ones in the alluvial stratigraphy being middle acheulian whereas those embedded in overlying deposits are from bottom to top upper acheulian and micoquian some of these sites have been recently excavated the quartzite artifacts were apparently abandoned by early humans on the flood plain surface during deposition of the us unit and were subjected to limited reworking during their incorporation in the alluvium tl osl dating of sandy silty sediments though imprecise support archaeological evidence pointing to an age of 150 000 to 70 000 yr b p for the us unit

lateglacial early holocene fluvial reactions of the jeetzel river elbe valley northern germany to abrupt climatic and environmental changes abstract mechanisms of climatic control on river system development are still only partially known palaeohydrological investigations from river valleys often lack a precise chronological control of climatic processes and fluvial dynamics which is why their specific forces remain unclear in this multidisciplinary case study from the middle elbe river valley northern germany multiple dating of sites palynostratigraphy radiocarbon and osl dating and high resolution analyses of environmental and climatological proxies pollen plant macro remains and ostracods reveal a continuous record of the environmental and fluvial history from the lateglacial to the early holocene biostratigraphical correlation to northwest european key sites shows that river system development was partially out of phase with the main climatic shifts the transition from a braided to an incised channel system predated the main phase of lateglacial warming 14 6 ka bp and the meandering river did not change its drainage pattern during the cooling of the younger dryas period environmental reconstructions suggest that river dynamics were largely affected by vegetation cover as a vegetation cover consisting of herbs dwarf shrubs and a few larger shrubs seems to have developed before the onset of the main lateglacial warming and pine forests appear to have persisted in the river valley during the younger dryas in addition two phases of high fluvial activity and new channel incision during the middle part of the younger dryas and during the boreal were correlated with changes from dry towards wet climatic conditions as indicated by evident lake level rises lateglacial human occupation in the river valley which is shown by numerous palaeolithic sites forming one of the largest settlement areas of that period known in the european plain is assigned to the specific fluvial and environmental conditions of the early allerod

late quaternary paleoclimatic and geomorphological evolution at the interface between the menyuan basin and the qilian mountains northeastern tibetan plateau abstract the tibetan plateau is regarded as an amplifier and driver of environmental change in adjacent regions because of its extent and high altitude however reliable age control for paleoenvironmental information on the plateau is limited osl appears to be a valid method to constrain the age of deposits of glacial and fluvial origin soils and periglacial structures in the menyuan basin on the northeastern tibetan plateau dating results show glaciers advanced extensively to the foot of the qilian mountains at 21 ka in agreement with the timing of the global last glacial maximum lgm recorded in northern hemisphere ice cores comparison with results from the eastern tibetan plateau suggests that the factor controlling glacial advance in both regions was decreased temperature not monsoon related precipitation increase the areas of the menyuan basin occupied by glacio fluvial deposits experienced continuous permafrost during the lgm indicated by large cryoturbation features interpreted to indicate that the mean annual temperature was 7 c lower than at present glacio fluvial systems in the menyuan basin aggraded and terraces formed during cold periods penultimate glaciation lgm and possibly the younger dryas as a response to increased glacial sediment production and meltwater runoff then

the relation between climate and river processes landforms and deposits during the quaternary abstract the extent to which river processes and morphology are dependent on climate is an old question when looking at large time scales climatic cyclicity seems to coincide with alternating events in fluvial development however the shorter the time scales at which fluvial development is considered the more it is difficult to find a close correspondence with climate evolution ultimately it appears that the response time of river processes to climatic change may restrict the sensitivity of the fluvial systems to adapt to short climatic oscillations the impact of climate on fluvial systems is largely transferred to these systems by the climate determined soil cohesion and peak discharges the latter factors are especially related to vegetation cover and permafrost conditions finally a number of basin characteristics are discussed that demonstrate that fluvial systems are not completely controlled by climate

river incision and terrace formation in the late cenozoic of europe abstract late cenozoic environmental changes which affected european rivers are reviewed focusing especially on those of mid pleistocene times c 1 2 0 8 ma or around mis 22 and thereafter these involved dominating but fluctuating cold climate periglacial conditions shorter but major episodes of glaciation and brief interglacials there were also related sea level and tectonic responses the known history of european rivers in this period is individually varied but is predominantly marked by multiple stages of episodic incision the form of which changed in style at around the mid pleistocene transition it is suggested that the nature of climatic oscillations the dating of incision episodes and the processes that achieve this incision are as yet insufficiently understood fluvial process studies suggest that the onset of incision may broadly relate to changes in slope discharge sediment load and calibre and bedrock erodibility and these may all have been transformed as the direct or indirect result of mid pleistocene climatic changes common properties of basal sediments on strath terraces suggest that it was during the extended but variable cold stage episodes that both valley deepening and lateral widening occurred and that climatic change was the principal driver of episodic deep valley incision

strength capacity of a no tension portal arch frame under combined seismic and ash loads abstract in some previous papers the seismic response of a simple structural system has been studied namely a masonry arch portal baratta et al 1996 seismic risk of historic centres modelled by the classical rules of mono dimensional structures and complex structural systems made of combinations of several elementary arch portals in this paper the seismic response of a simple masonry arch portal under the combined action of horizontal seismic forces and vertical overload due to volcanic ash fall subsequent to an eruption is discussed decay of the collapse coefficient of the horizontal load is evaluated for ash fall load increasing

geomorphological evolution of a lowland valley system during the weichselian weichselian geomorphological and fluvial evolution has been recorded in the valley fill of the reusel a small tributary of the lower maas river it has been studied by means of borehole sections a first deep incision into the substratum occurred during the early weichselian lower pleniglacial this was followed by aggradation at first by a braided river at a later date by a meandering river dating respectively from the lower and middle pleniglacial the upper pleniglacial aggradation again points to a braided river system the end of the pleniglacial is characterized by aeolian infilling of the valley and decreasing carrying capacity of the river

sedimentology and geomorphology of overbank flows on meandering river floodplains abstract along floodplains there occurs an ordered sequence of geomorphic events during floods the following sequence occurs for individual flood events 1 the rise of floodwater and of groundwater 2 the inundation of the floodplain 3a adjustments of the overbank flow pattern to the floodplain environment 3b the flood peak 4 the initial fall of floodwaters and changes in the overbank flow pattern 5 a gradual cessation of the overbank flow 6a infiltration evaporation and a wave like motion of stagnant water and 6b postflood transformation under subaerial conditions field observations support this model for meandering rivers in the polish lowland

quaternary river terraces in england forms sediments and processes abstract flights of quaternary river terraces in south and east england have common characteristics involving low gradient planed or irregular bedrock surfaces and single or multi storey gravel deposits rather than depending on warm cold or cold warm transitions it is suggested that bedrock planation working depths of gravel and later stage relatively shallow aggradations are all dominantly of cold climate origin basal sediments show active incorporation of plucked and periglacially shattered materials whilst super incumbent units incorporating up catchment and slope derived materials demonstrate later cold stage sediment influx and consequent cessation of active bedrock erosion channel activity effecting both planation and deposition are reviewed together with the detailed sedimentology of gravelly sediments which show evidence of both autogenic processes bar migration channel switching and infilling and truncation of upper sedimentation units cold climate indicators turbation ice wedge casts and frozen block transport and specifically for the last glacial interglacial cycle varying sediment flux as climates changed both interglacial and transitional activities are believed to be of lesser morphological significance whilst prior uplift is taken as enabling rather than being a generator of terrace within the timescale of a glacial interglacial cycle variations within cold stage climates varying sediment influx and channel belt bedrock erosion are stressed as dominating mid catchment and mid latitude quaternary terracing at the glacial interglacial scale

climate and related controls on interglacial fluvial sedimentation in lowland britain lewin john gibbard p l 2002 climate and related controls on interglacial fluvial sedimentation in lowland britain sedimentary geology 151 3 4 pp 187 210 rae2008

reconstructing the interacting effects of base level climate and tectonic uplift in the lower mino river terrace record a gradient modelling evaluation the origin of the lower mino river terraces in the nw iberian peninsula has been a topic of debate since the 1940s various hypotheses about their main controlling factors have been put forward but general consensus is still lacking field studies of terrace distribution and the weathering of quartzite pebbles in the terrace deposits demonstrated that terrace longitudinal correlation is not parallel to the current river bed in addition the longitudinal profile model fluver2 was used to simulate the profile evolution of the mino river over the past 450 ka a reconstructed longitudinal profile and an offshore climate record were used as inputs several scenarios with variable uplift rates were investigated and evaluated against properties of four selected reaches along the river for a match with the number of terraces their relative altitude timing and sediment thickness an uplift scenario with a net constant vertical uplift rate of 0 08 m ka 1 yielded the best results the best fit scenarios indicate that base level changes from glacioeustatic changes in combination with tectonic uplift are the main driving forces of the observed terrace formation and valley incision contrary to most nw european fluvial systems the timing of upstream controlled sediment supply has a less dominant effect on terrace formation this can be explained by the close proximity to the narrow passive atlantic margin

climate related river activity at the weichselian holocene transition a comparative study of the warta and maas rivers huvial systems from the dutch and polish lowlands are compared for their evolution during the weichselian deglaciation period in both regions the pleniglacial braided river pattern changed to a meandering pattern in the beginning of the lateglacial several transitional stages between braided and high sinuosity meandering systems have been recognized a difference in fluvial activity is found during the younger dryas when the maas transformed to a braided pattern while the warta maintained its meandering pattern phases of erosion and aggradation are more or less synchronous in the different river basins but their intensity may differ greatly the major characteristics of the fluvial systems are obviously a response to the general climatic evolution and related to changes in vegetation the regional differences are of minor importance and can be explained by site specific factors threshold values within the latter factors define the changes in river dynamics

river response to variations of periglacial climate in mid latitude europe abstract the last glaciation was characterised by considerable changes in climate many european river basins reacted to these changes by initial incision and subsequent pattern change earlier research explained this by the time lag of vegetation development after a climatic change which considerably affected the sediment load however since some river basins react differently or do not react at all this model needs to be refined this paper deals with the fluvial evolution of several rivers in northern and central europe during the last glaciation and two of them the weise elster river in the leipzig area and the spree river in the niederlausitz germany are discussed in more detail the vegetation cover on the floodplain in combination with the presence of frozen ground which affects the discharge characteristics largely determines the river type nevertheless when the sequences are compared not only synchronous changes in fluvial development may be observed but also distinct differences in fluvial development by analysing the different rivers in their varying geomorphological settings it appears that grain size basin configuration and catchment size are important parameters also which can determine whether a threshold is exceeded or not

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

pleistocene fluvial terraces from northern france seine yonne somme synthesis and new results from interglacial deposits the seine yonne and somme are the main rivers draining northwestern france and flowing into the channel during pleistocene cold stages they were tributaries of the fleuve manche they are characterised by well developed stepped terrace systems showing up to 10 incision steps for the last 1 ma after 15 years of research and the synthesis of stratigraphical sedimentological bioclimatical data and numerical dating these terrace systems are interpreted as the response of the fluvial environments to climatic cyclicity superimposed on a background of slow tectonic uplift the comparison of these three terrace systems shows that the incision budget is similar within the studied area about 55 65 m 1 ma implying relative homogeneity of uplift in the main part of the area beyond marine influence the analysis of each stepped alluvial formation shows regular sediment balance generally composed of coarse periglacial gravels pleniglacial covered by fine grained sediments locally overlain by calcareous tufa interglacial however in the lower seine valley close to the present coast the low terrace includes two estuarine interglacial units interbedded within periglacial gravel units nevertheless until recently evidence of full interglacial conditions remained elusive in fluvial contexts especially in the somme to address these issues a new research programme has been launched on tufa deposits that are the best candidate to register the climatic optimum initial results from la celle seine saint acheul and caours somme allow palaeoenvironmental reconstructions of mis 11 and 5e and thus confirm the importance of calcareous tufa to define a reference record of pleistocene interglacials for northern france moreover it has been previously demonstrated that the main incision leading to terrace formation can be attributed to the transition between interglacial and glacial during early glacial phases the new results from interglacial records have important implications concerning the precise occurrence of the major incision phases within the climatic cycle as they provide the starting point immediately preceding downcutting

last glacial interglacial cycle in the evolution of river valleys in southern and central poland abstract the last glacial interglacial cycle is represented usually by several cuts and fills which have formed 2 3 terrace steps from the last cold stage and by two or more fills of lateglacial holocene age their number depends on the size of the river valley and the position in the longitudinal profile the sequence of changes reflects shorter stadial interstadial climatic fluctuations generally aggradation dominates during the cooler phases of the vistulian and during the interpleniglacial the most distinct erosional phases occurred during the change from a more oceanic to a more continental climate before the maximum extension of the ice sheet 25 20 ka bp and during the upper pleniglacial lateglacial transition 15 13 ka bp the second phase coincides with the rapid downcutting in the lower course of the main vistula valley which had been blocked earlier by the scandinavian ice sheet in the holocene aggradation prevailed accelerated by anthropogenic soil erosion it was only in the mountain foreland that shorter lived hydrological changes resulted in well expressed several cuts and fills

river terraces as a response to climatic forcing formation processes sedimentary characteristics and sites for human occupation abstract climate impact on the fluvial processes led to morphological and sedimentological differentiation of a terrace this diversity in the fluvial environment determined how people could adapt to the river although the climatic impact on development and initiation of river terraces seems to be well accepted a number of pertinent questions disturb this simplicity for instance the exact terrace development within a climate cycle is still under debate different kinds of terraces and their sedimentary successions may originate either from aggradation incision or lateral migration is there a typical sedimentary succession below terraces what is the genetic origin of each sedimentary layer what are the relative ages of those layers and erosion phases within a climate driven erosion aggradation cycle the variability in staircase preservation in relation to climatic cyclicity is analysed in three scenarios specific scenarios depend essentially on the preservation of the fluvial deposits dating from the warm periods finally a preliminary inventory is presented of the most favourable sites for human occupation in fluvial valleys as derived from a random selection of archaeological findings generally human occupation in that morphological position seems to be linked with at least temporarily dry conditions climatic conditions do not seem to play the major role the termination of a settlement may have been due to increased risks of flooding apart from other than natural fluvio environmental reasons

using vhr multispectral remote sensing and lidar data to determine the geomorphological effects of overbank flow on a floodplain the vistula river poland abstract at the bottoms of river valleys there can be found landforms developed by overbank flow such as crevasse channels and crevasse splays usually cut off from the main river channel by the natural levees humans construct embankments artificial levees which completely divide integrated parts of the river valley and thus gain new areas for agriculture and settlement purposes however during extremely high water stages these areas suffer from flooding very often caused by levee breach the objective of the study is to answer the research question can we use geomorphological analysis of the floodplain to predict extreme flood effects in a large river valley with an artificial levee system the study has been conducted in a reach of the vistula river 60 km downstream from warsaw poland that was affected by catastrophic flood event in may and june 2010 specific emphasis has been put on using very high resolution vhr multispectral remote sensing and lidar light detection and ranging data work is divided into three stages 1 identification of floodplain landforms from palaeofloods on the vhr multispectral satellite imagery 2 outline of the 2010 flood event on the basis of river stage data and acoustic doppler current profiler measurements and a detailed study of its geomorphologic effects on the floodplain on the basis of aerial imagery and lidar data 3 comparison of landforms created in palaeofloods and in the 2010 flood event the results of the study show that geomorphological effects of the recent catastrophic flooding are strikingly similar to palaeoflood landforms developed before the construction of an artificial levee system the main conclusion is that overbank flow in some reaches of the floodplain causes and will cause similar effects as it has done in the past analysis of palaeoflood landforms enables prediction of these effects and can therefore prove useful for flood risk management post flood transformation of palaeoflood landforms by human impact and natural geomorphological processes induces the use of special methods for the identification of the landforms and study of their spatial features vhr multispectral remote sensing enables such analysis in many places of the earth lidar data provide new possibilities for the accurate estimation of overbank deposition and erosion rate on the floodplain

quaternary evolution of a meandering gravel bed river in central spain the river jarama is a medium sinuosity meandering river with gravel bedload throughout the quaternary it developed a large number of terraces in a repetitive sequence of aggradation stability degradation stability stages which are studied in the middle reach of the river applying geomorphological and sedimentological methods as well as kadiocarbon dating techniques the upper terrace system of earliest pleistocene to mid pleistocene age forms isolated fragments vertically disconnected and colluviated and their sequential distribution of facies implies lateral shifting of channels and a welldeveloped flood plain the middle terrace system of mid to late pleistocene age has differentiated levels in the upstream reaches while downstream they condense giving a thick multi episodic series corresponding to the tectonic tilting of the basin classical point bar fining upward sequences of a medium to high sinuosity river with gravels and sands as bedload are clearly differentiated in them a major degradation stage follows this group of terraces with an incision of up to 30 m then during a relatively long period of stability a forest of riparian species developed prior to the last aggradational stage of the lower terrace system the aggradation resulted in a fining upward sequence where lateral accretion is clearly visible in the gravels due to migration of the medium to low sinuosity river sedimentation continued and was active up to the 1950s but since then intense anthropogenic modifications led to renewed incision of the river

multiphase timing of hominin occupations and the paleoenvironment in luonan basin central china thousands of paleolithic artifacts have been recovered from paleolithic sites in the luonan basin in the upper south luohe river of central china their discovery suggests that the basin was an important area for hominin settlement during the pleistocene however the initial timing of this occupation and the environmental conditions for this period are still largely unknown in addition the sediments are not well dated and most of the artifacts lie on the surface in an attempt to resolve these issues a new systemic paleomagnetic analysis was carried out on the loess deposits that contain in situ stone tools our detailed loess paleosol analyses of the stratigraphy of different sites in the basin and chinese loess plateau shows the accumulation of the loess since at least 1 1 million years ma ago moreover recently discovered in situ cores flakes and retouched stone tools in these deposits show that hominins used this region repeatedly from 0 8 0 7 ma to 0 4 0 3 and 0 2 0 1 ma pedostratigraphic analyses magnetic susceptibility and carbon isotope analyses also indicate that these hominins lived in a subtropical to warm temperate climate with broad needle leaf forest vegetation mixed with grasses c 2011 university of washington published by elsevier inc all rights reserved

tt osl dating of longyadong middle paleolithic site and paleoenvironmental implications for hominin occupation in luonan basin central china dating middle pleistocene hominin occupations alongside the reconstruction of paleoenvironments in china between 700 and 100 ka has always been a challenging task in this paper we report thermally transferred optically stimulated luminescence tt osl dating results for a middle paleolithic site in the luonan basin central china which we have named longyadong cave the results suggest that the age of cave infilling and the deposition of sediments outside the cave range between 389 18 and 274 14 ka these deposits are stratigraphically and geochronologically correlated with the l4 loess and s3 paleosol units of the typical loess paleosol sequence of the chinese loess plateau and with marine isotope stages mis 10 to 9 respectively on the basis of these new ages and the available paleoenvironmental data it is suggested that the longyadong hominins might have occupied the site both in glacial and interglacial periods demonstrating that they coped well with environmental change in this mountainous region in warm wet and cold dry climates the study further implies that the hominins abandoned the longyadong cave between 274 14 and 205 19 ka when it was sealed by alluvial and slope deposits c 2012 university of washington published by elsevier inc all rights reserved

differential impact of small scaled tectonic movements on fluvial morphology and sedimentology the huang shui catchment ne tibet plateau abstract the aim of this paper is to investigate the morphological implications of the interplay between tectonic movements at different rates timescales and spatial extent in a catchment of intermediate size the huang shui river a main tributary of the yellow river in the ne tibet plateau river incision started from a peneplain like surface that developed in post miocene pliocene times at the end of the tertiary a general tectonic uplift of the tibetan plateau initiated river incision this general uplift also caused local fragmentation of the huang shui catchment into blocks kilometers or maximally a few tens of kilometers of local extent that have subsided and or uplifted relative to one another fluvial deposition of 30 m in the subsiding blocks contrasts with erosion and formation of gorges in the uplifted blocks incision into the former peneplain was not continuous but a staircase of terraces developed under climatic influences terrace deposits are sometimes capped by interglacial soils or soil derived material apparently terrace incision occurred at the transition to the next cold period the different rates of uplift and subsidence of the individual blocks resulted in the simultaneous development of erosion and accumulation terraces of different sizes within the same catchment even within the same tectonic block this makes it impossible to connect the terraces of the different blocks except for the three youngest terraces representing the last 300 000 years thus illustrating the uniform tectonic history of the catchment since that time

sensitivity of weichselian fluvial systems to climate change nochten mine eastern germany abstract this paper aims to contribute to the understanding of fluvial system response to climate change during the last glacial interglacial cycle fluvial and aeolian successions have been studied in the opencast brown coal mine nochten in eastern germany an absolute chronology was established by luminescence and 14 c dating enabling to demonstrate the relations between depositional units and changes in sedimentary environment over time with regional climatic and vegetational changes it is concluded that the major climatic periods coinciding with the oxygen isotope stages are generally reflected in the fluvial sequence by distinct fluvial environments major climatic changes oxygen isotope stage boundaries have been preserved in the fluvial record as erosional bounding surfaces and by changes in fluvial style rapid climate changes like the middle pleniglacial dansgaard oeschger cycles are in general not reflected in the fluvial succession these cycles were too short or with too low amplitude to cause a strong vegetational response and related changes in water and sediment supply it is emphasized that also the preservation potential of short lived climatic warming events in high energy fluvial systems is low warming events may however have been preserved in lacustrine successions in former thermokarst lakes a strong cooling event at ca 40 ka leading to continuous permafrost conditions and changes in the water and sediment budget was reflected in the fluvial archive by a change from sandy anabranching to braided river conditions

the somme valley terrace system northern france a model of river response to quaternary climatic variations since 800 000 bp recent research on the somme valley terrace deposits that began in 1987 has resulted in an integrated sequence of geological and geomorphological evidence for this area that is of particular significance for prehistoric investigations this has been achieved using previous evidence and new results from archaeological and geological excavations these include longitudinal profiles cartography and detailed synthesis of sections of alluvial deposits stratigraphy of river deposits and overlying loess sequences the work based on a study of the geometry of the terrace system has resulted in the identification of ninestepped alluvial formations that occur along 70 km of the valley detailed study permits the integration of the various alluvial sequences this suggests that each alluvial sequence results from sedimentation through a single glacial interglacial climatic cycle this hypothesis is confirmed by investigation of soil and loess sequences of the deposits overlying the fluvial sediments the synthesis presented provides a basis for understanding the deposition of the terrace system and an initial chronostratigraphic interpretation for the deposits

uplift driven valley incision and river terrace formation in southern england outside the limits of middle pleistocene glaciation the river basins of southern england contain long cenozoic terrestrial sedimentary records of greatest importance are the river terrace sequences which contain biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary however trends in valley development cannot easily be accommodated within the framework of quaternary climatic change it is argued in this paper that episodic incision and terrace development result from uplift a consequence of the interplay between continuing alpine orogenic movements and erosion driven isostasy using a simple linear model height age an uplift rate of ca 7 cm ka 1 is estimated for the terrace sequence in the upper thames valley this preliminary model is evaluated using the records of adjacent basins 1997 john wiley sons ltd

spatial variation of overbank aggradation rate and its influence on avulsion frequency river avulsions are commonly considered to be driven by the aggradation and growth of alluvial ridges and the associated increase in cross valley slope relative to either the down channel slope or the down valley slope the latter is termed the slope ratio in the present paper therefore spatial patterns of overbank aggradation rate over stratigraphically relevant time scales are critical in avulsion dominated models of alluvial architecture detailed evidence on centennial to millennial scale floodplain deposition has to date been largely unavailable new data on such long term overbank aggradation rates from the rhine meuse and mississippi deltas demonstrate that the rate of decrease of overbank deposition away from the channel belt is much larger than has been supposed hitherto and can be similar to observations for single overbank floods this leads to more rapid growth of alluvial ridges and more rapid increase in slope ratios potentially resulting in increased avulsion frequencies a revised input parameter for overbank aggradation rate was used in a three dimensional model of alluvial architecture to study its effect on avulsion frequency realistic patterns of avulsion and interavulsion periods 1000 years were simulated with input data from the holocene rhine river with avulsions occurring when the slope ratio is in the range 3 5 however caution should be practised with respect to uncritical use of these numbers in different settings evidence from the two study areas suggests that the avulsion threshold cannot be represented by one single value irrespective of whether critical slope ratios are used as in the present study or superelevation as has been proposed by other investigators

fluvial response to weichselian climate changes in the niederlausitz germany the last glacial shows large variations in climate which are reflected in the fluvial record in the niederlausitz eastern germany the entire sequence resembles the fluvial development in other river basins in northwestern europe which show contemporaneous changes in depositional style at the onset of a climatic change during the middle and the late pleniglacial permafrost conditions resulted in an episodic river discharge the presence or absence of vegetation in combination with such ephemeral stream conditions determined the type of river during each period a relatively well developed vegetation cover on the flood plains during the middle pleniglacial resulted in a low sediment yield in combination with the intermittent discharge this caused the development of an ephemeral anastomosing river system a river with stable channels and extensive sandy overbank areas the decline in vegetation cover at ca 28 ka bp caused an increase in sediment yield and peak discharges which resulted in the development of a sandy braided river in adjustment to these new conditions following the coldest period at around 20 ka precipitation was so low that fluvial activity was limited and aeolian deposition took place in the valley 1997 by john wiley sons ltd

the use of gpr to image three dimensional 3 d turbidite channel architecture in the carboniferous ross formation county clare western ireland

fluvial response to rapid climate change during the devensian weichselian lateglacial in the river great ouse southern england uk few lateglacial 15 200 11 500 cal bp fluvial deposits are known from southern england uk this paper outlines a sedimentological investigation of a lateglacial site near the village of roxton in the middle reach of the river great ouse below the holocene argillaceous alluvium several large gravelly lithofacies units representing long term fluvial processes are recognised based on their lower bounding surfaces and sedimentary features in line with palaeontological evidence and radiocarbon dating detailed facies analysis indicates that the river changed from a braided to a wandering meandering regime in response to the warming induced reduction in nival peak discharge and increase in vegetation cover consisting of birch woodland and grassland during the lateglacial interstadial 15 200 12 700 cal bp this was followed by a change back to a braided river in response to climatic deterioration during the younger dryas chronozone 12 700 11 500 cal bp the interstadial floodplain consisted of both overbank fines and channel lateral or point bar sands and gravels the two suites of contemporaneous sediments in the geological succession may be easily mis interpreted as independent climato stratigraphical units due to their cross cutting relationship and marked difference in facies assemblage lateral channel movement in such a system also implied that the floodplain underwent constant erosion resulting in underdeveloped overbank sequences insufficient to withstand post depositional removal by erosion this probably accounts for the rare preservation of fine textured overbank deposits of the lateglacial interstadial in southern england

timescales climate and river development abstract in the long term glacial interglacial sequences river development follows general climatic evolution however at the scale of one cold warm cycle it appears that the geomorphological effect of river activity is best expressed at times of climatic change such periods of pronounced fluvial action last only a short time in more detail the internal evolution in a drainage basin after a climatic event results in a delayed response of the morphology and sedimentation pattern finally on the shortest timescale local thresholds may play a decisive role in the reactions of river systems it is concluded that the relation between fluvial development and climate is not a simple one but is fundamentally dependant on the timescale

uplift driven valley incision and climate controlled river terrace development in the thames valley uk abstract the sequence of terraces of the river thames in southeast england has previously been shown to span the period from the earliest pleistocene to the present this terrace sequence contains biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary large scale fluvial incision resulting in basin wide terrace formation appears to have been concentrated at the warming limbs of the major climatic glacial interglacial cycles when sediment supply was greatly reduced this incision and subsequent valley floor widening created the accommodation space for the later aggradation of the terrace sediments during the following warm cold transitions and during the cold stages when high sediment supply conditions prevailed although the timing of terrace aggradation may be controlled by climate change the progressive valley incision recorded by terrace staircases cannot easily be explained in terms of quaternary climatic change alone and recently developed models suggest that long term incision by the thames has been driven by uplift this paper presents an overview of the available terrace data and tabulates incision amounts and rates between key stratigraphic horizons superimposed upon these broad changes revealed by the complex internal sedimentary architecture of many terrace sediments are the geomorphological system responses to both higher frequency climate driven changes and more localized intrinsic fluvial system adjustments

climatic control on quaternary fluvial sedimentology of a fenland basin river england understanding and interpreting climate response from ancient fluvial deposits requires a combined approach of detailed sedimentological description and interpretation local climate proxies and the accurate comparison of these sequences with further independent climate records application of these multiple lines of evidence is particularly effective in the quaternary period where higher resolution and more detailed palaeoenvironmental reconstruction are possible this paper presents results from a devensian weichselian age sequence in northern fenland england that integrates these approaches detailed sedimentological description has identified three fluvial facies associations overlain by a period of ice wedge cast formation fossil plant and coleopteran material within these sediments have been studied to provide palaeoenvironmental reconstructions for the local landscape including quantitative temperature estimates using the mutual climatic range method on fossil coleoptera in addition joint application of radiocarbon and optically stimulated luminescence osl dating allows this sequence to be compared with the stacked marine isotope record although dates do not agree well at the limit of the radiocarbon technique sedimentological interpretations palaeoenvironments and global ice volume variations a proxy for climatic severity are all in agreement and show clearly how the river nene responded to subtle changes in climate and vegetation cover during the devensian weichselian stage the level of detail possible in this reconstruction shows the importance of this approach in understanding fluvial response to past climate changes

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