architecture of miocene overbank deposits in northern pakistan abstract understanding the geometry of sediment bodies and patterns of sediment disruption in ancient fluvial overbank successions is fundamental to interpretations of overbank deposition overbank deposits of the fluvial chinji formation siwalik group can be divided into sequences 1 20 m thick defined by the alternation of stratified sediments and paleosols preservation of stratified sequences does not support a gradual vertical aggradation of overbank sediments over the extent of the floodplain but instead indicates periods of rapid sediment deposition followed by long hiatuses and soil development rapid deposition of overbank sequences is predicted by models that hypothesize 1 episodic vertical aggradation of the entire floodplain 2 deposition controlled by the growth of alluvial ridges 3 incision and filling of local valleys 4 rapid filling of localized low areas or 5 rapid deposition associated with river channel avulsion these models also have important implications for understanding fossil preservation and floodplain paleoecology paleosol bounded sequences in the chinji formation can pinch out laterally over kilometers indicating that episodes of rapid deposition were restricted to local areas on the floodplain there is no evidence that bases of sequences are erosional and they do not appear to record valley incision and filling sequences generally do not thin and fine systematically away from the terminating margins of major channel deposits suggesting they are not related to the growth of alluvial ridges along active channels lithologic variations and patterns of sediment disruption within sequences appear to reflect the rapid tilling of low areas on the floodplain both adjacent to and distal from the major river channel this infilling of floodplain topography may reflect a continuous process whereby local areas were always being filled somewhere on the floodplain by sediments from minor tributary or crevasse channels alternatively the filling of local flood plain topography may have been caused by widespread but short lived events associated with river channel avulsion

glacial rebound and plate spreading results from the first countrywide gps observations in iceland iceland is one of the few places on earth where a divergent plate boundary can be observed on land direct observations of crustal deformation for the whole country are available for the first t

correlation of fluvial sequences in the mediterranean basin over the last 200 ka and their relationship to climate change macklin mark fuller i c lewin j maas g a 2002 correlation of fluvial sequences in the mediterranean basin over the last 200 ka and their relationship to climate change quaternary science reviews 21 14 15 pp 1633 1641 rae2008

preliminary taphonomical studies of some pleistocene fauna from the central narmada valley madhya pradesh india abstract preliminary taphonomical studies carried out on a pleistocene faunal assemblages from the central narmada valley madhya pradesh india reveals that the assemblage has undergone hydrodynamic sorting resulting in the transportation of the fossils also there has been a delayed burial of the bones field sedimentological evidence supports the occurrence of the assemblage in channel deposits under the influence of moderate currents

geomorphic and hydrologic aspects of monsoon floods on the narmada and tapi rivers in central india abstract high magnitude floods during the monsoon season are considered to be india s recurring and leading natural disaster such large flood are extremely important events not only in terms of human impact but also from the standpoint of geomorphic effectiveness and geomorphic work the narmada and tapi rivers in central india are characterized by one of the most intense flood regimes in the seasonal tropics modern historical and palaeoflood records indicate that large floods are relatively common hydrologic and geomorphic events on the narmada and tapi rivers a catastrophic flood on tapi in july 1991 that occurred from heavy rains and a dam break represents one of the highest unit discharges yet recorded in any part of central india flood competence studies indicate that the flood power of the two rivers is comparable with some of the largest historic and prehistoric floods reported from other parts of the world the rivers have preserved geomorphic and sedimentologic records of palaeofloods for the last two millennium and in choral river a 5000 year old record has been located examination of the synoptic conditions associated with the flood generating low pressure systems reveals that all but a few of them are the result of bay of bengal depressions the flooding in such large rivers profoundly challenges flood hazard management because of limited instrumental records and large spatio temporal variation it is therefore imperative that the design engineering community in india incorporates the geomorphic sedimentologic and botanic information in the planning and design of water resource development projects

late pleistocene alluvial plain sedimentation in lower narmada valley western india palaeoenvironmental implications abstract late pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30 50 m high incised vertical cliffs all along the lower narmada valley in western india the exposed fluvial deposits have been classified into two sediment packages alluvial fan sediments overlain by alluvial plain sediments the alluvial plain sequence has not been studied previously it consists mainly of sands and silts and is dominated by overbank deposits occurrence of large scale bedforms in the alluvial plain sequence points to the existence of a large sand bed river in an alluvial plain setting the major sedimentary facies in stratigraphic order include large channel fills giant epsilon cross bedded strata overbank fines occurring in horizontal massive and undulatory stratified forms associated with crevasse splay and backswamp deposits and a reddish brown palaeosol overlain by thinly stratified sands and silts at the top of the exposed sediment succession large sized channel fills occur at two stratigraphic levels which are morphologically similar and are indicative of high rates of deposition and avulsion the large channel fill structures and the giant epsilon cross bedded strata indicate a large single channel river that was consistently 10 15 m deep and about 70 80 m wide even during the dry seasons these dimensions are larger than those of the present day narmada river at low discharge levels the overbank sediments indicate rapid deposition through frequent overbank floods and floodplain aggradation by a laterally shifting river available chronologic data suggests that the reddish brown palaeosol correlates with a regional phase of pedogenesis in the alluvial plain of gujarat prior to the last glacial maximum lgm the thinly stratified sands and silts overlying the palaeosol were deposited by a considerably depleted but perennial river during the arid phase of the last glacial maximum overall the alluvial plain sediments of the lower narmada valley particularly those below the palaeosol have been attributed to a hyper avulsive large river with low sinuosity whose high discharge levels were determined primarily by a large catchment area further to the east and not by the semiarid climate prevailing in the gujarat alluvial plain during the upper part of the late pleistocene the study concludes that the narmada river has maintained a large catchment at least since the last 100 ka however the river was characterised by a much bigger channel during much of the late pleistocene with discharge levels higher than the present day

northern europe climate variations during late holocene evidence from marine skagerrak abstract granulometric and stable oxygen isotope analyses of four sediment cores from two high accumulation areas in the skagerrak ne north sea were carried out in order to reconstruct climate fluctuations and to evaluate climate impact during the upper holocene extremely high sedimentation rates especially in the eastern skagerrak are explained by increased current activity which is responsible for the transport and deposition of high quantities of suspension load during periods of stormy zonal atmospheric circulation patterns these were most frequent during colder periods while warmer phases are characterized by calmer meridional to zonal atmospheric circulation patterns while the subatlantic climate deterioration and the subboreal climate optimum left only indistinct traces in the sediments the roman climate optimum and a colder period between ca 400 and 700 ad are well documented the following medieval warm period is characterized by a clear temperature increase of the waterbody in connection with less frequent advances of atlantic water masses into the skagerak deep and a decrease in bottom current strength a mode of sedimentation prevails similar to that of recent summer conditions suggesting short and mild winters during that period the onset of the little ice age around 1350 ad however shows an intensified bottom current circulation most probably due to amplifying westerly winds and a decrease in water temperatures in connection with more frequent advances of higher saline atlantic waters the little ice age can be divided into 3 phases a stormy zonal onset a calm meridional maximum and a stormy zonal end the stormy phases are characterized by a sedimentation mode similar to that of recent winter conditions while the little ice age maximum shows conditions comparable to exceptional cold modern winters from 1900 ad at the onset of the modern climate optimum the winter type sedimentation decreases and conditions change again to a level comparable to the medieval warm period

channel form and processes of the flood dominated narmada river india the 1300 km long narmada river flows along a structural lineament alternating between constricting rocky gorges and rapids and meandering wide alluvial reaches channel forms and processes were studied in a 120 km long section of an alluvial reach channel size shape and bedforms in the narmada river are related to very large floods which have occurred three times in this century during such floods the entire 400 m wide channel is utilized and 10 15 m high cliffs on both sides operate as riverbanks normally even the high flows of the south westem monsoon are insufficient to fill the whole channel and hence their effects are limited to building of discontinuous floodplains between the cliffs and modifying bedforms and bars a channel in channel topography is thus created the very large floods are also responsible for erosion of the rocky stretches and building of point bars the river meanders but its movement is restricted because of 1 rocky gorges and scablands operating as anchor points at intervals and 2 the presence of high alluvial cliffs which are topped on extremely rare occasions in spite of being located in a tectonically active zone in a monsoon setting it is the exceptional high magnitude floods at irregular intervals which control the form and behaviour of the narmada river

morphotectonic segmentation and spatial variability of neotectonic activity along the narmada son fault western india remote sensing and gis analysis abstract morphotectonic analysis of landscape using remote sensing and gis is an effective way of deducing the pattern and spatial variation of neotectonic activity along poorly investigated active faults in this paper we evaluate the neotectonic activity along a part of the seismically active but poorly understood narmada son fault nsf a more than 1000 km long ene wsw trending fault transecting through the central part of the indian plate the nsf in the study area is geomorphologically expressed as an ene wsw trending line of north facing scarps that delimit the rugged mountainous topography of the uplands to the south and the alluvial basin to the north which prominently slope away from the scarps the scarps are developed in the south dipping basaltic flows belonging to the deccan trap formation of the late cretaceous eocene and continue westward into tertiary rocks and further as a paleobank of the narmada river field studies have revealed that the nsf in the study area is divisible into four morphotectonic segments i to iv which is attributed to the tilakwada karjan madhumati and rajpardi faults cutting across the nsf we characterize the neotectonic activity of the segments through dem analysis using geomorphic indices which include the mountain front sinuosity hypsometric curves hypsometric integral asymmetry factor stream length gradient index and channel sinuosity interpretations of morphometric data are well supported by field data both the entire length of the nsf and the cross faults are found to be neotectonically active we demonstrate that segment ii has undergone the highest intensity of neotectonic activity followed by segments iii i and iv this is corroborated by the highest elevation of scarps and the alluvial deposits the deepest incision 40 m depth and steep northward slope of the alluvial plain in segment ii we infer that the nsf is characterized by differential uplift in recent past which agrees with the high angle reverse faulting with oblique slip movements along the cross faults

paleorainfall reconstructions from pedogenic magnetic susceptibility variations in the chinese loess and paleosols the rock magnetic properties of the chinese loess and paleosols constitute a unique and sensitive record of east asian paleoclimate through the quaternary period systematic variations in the concentration and grain size of the magnetic minerals in these sediments have produced systematic variations in the magnetic susceptibility signal which can be easily and rapidly measured at many sites across the loess plateau variations in many other rock magnetic properties can be used to identify the key shifts in ferrimagnetic grain size but magnetic susceptibility alone is sufficiently sensitive to record stadial and interstadial climate stages as well as glaciations and interglaciations past changes in rainfall and monsoon activity for this region are reconstructed from the susceptibility variations the susceptibility record is calibrated using the modern relationship between rainfall and pedogenic susceptibility on the loess plateau our rainfall reconstructions identify enhanced summer monsoonal activity in the chinese loess plateau region in the early holocene and the last interglaciation in the presently semiarid western area of the plateau annual precipitation in interglacial times was up to 80 higher than at present in the more humid southern and eastern areas values were up to 20 higher than today s levels during the last glaciation precipitation decreased across the entire plateau typically by 25 the relationship between pedogenic susceptibility climate and weathering age was examined over the northern hemisphere temperate zone and the observed positive correlation between rainfall and susceptibility indicates that climate rather than soil age is the predominant factor that controls pedogenic susceptibility enhancement in loess soils

chronology of late pleistocene environmental changes in the lower mahi basin western india sediments exposed in the lower mahi basin at the southern fringe of the thar desert rajasthan india provide evidence of three distinct depositional environments namely marine aeolian and fluvial these have been used to reconstruct late pleistocene environmental and tectonic history of the region infrared stimulated luminescence irsl chronology of the fluvial and aeolian litho units provides evidence of two major fluvial aggradation phases in the region corresponding to oxygen isotopic stages 5 and 3 the basal marine clay is inferred to represent the last interglacial stage and its present elevation at 20 m a s l is attributed to post depositional tectonism comparison of fluvial records from other regions indicates interhemispherically documented wetter phases during oxygen isotope stages 5 and 3 copyright 2000 john wiley sons ltd

a reconstruction of the north atlantic oscillation using tree ring chronologies from north america and europe tree ring records six from eastern north america and four from northwestern europe are used to develop the first reconstruction of the winter north atlantic oscillation nao the reconstructed series spans the interval ad 1701 1980 and explains 41 of the variance in the nao over the ad 1874 1980 calibration period the reconstruction also captures the spectral properties of this index suggesting that the oscillatory character of the nao is a long term feature of the north atlantic climate system

do stable isotope data from calcrete record late pleistocene monsoonal climate variation in the thar desert of india late pleistocene terrestrial climate records in india may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete petrography shows that calcrete nodules in quaternary sediments of the thar desert in rajasthan are pedogenic with little evidence for postpedogenic alteration the calcrete occurs in four laterally persistent and one nonpersistent eolian units separated by colluvial gravel thermoluminescence and infrared and green light stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units i iv of ca 70 000 60 000 ca 60 000 55 000 ca 55 000 43 000 and ca 43 000 25 000 yr respectively the youngest eolian unit v is 10 000 yr old and contains no calcrete stable oxygen isotope compositions of calcretes in most of eolian unit i in the upper part of eolian unit iv and in the nonpersistent eolian unit range between 4 6 and 2 1 pdb these values up to 4 4 greater than values from eolian units ii and iii are interpreted as representing nonmonsoonal18o enriched normal continental waters during climatic phases when the monsoon weakened or failed conversely 25 000 60 000 yr old calcretes eolian units ii and iii probably formed under monsoonal conditions the two periods of weakened monsoon are consistent with other paleoclimatic data from india and may represent widespread aridity on the indian subcontinent during isotope stages 2 and 4 the total variation in 13c is 1 7 0 0 1 7 and 13c covaries positively and linearly with 18o 13c values are highest when 18o values indicate the most arid climatic conditions this is best explained by expansion of c4grasses at the expense of c3plants at low latitudes during glacial periods when atmosphericpco2was lowered c4dominance was overridingly influenced by global change in atmosphericpco2despite the lowered summer rainfall

large scale facies sequences in alluvial overbank environments abstract gradational coarsening upwards or fining upwards sequences order of meters thick in overbank environments can be produced by progressive crevasse splay levee progradation or abandonment while the channel belt remains unchanged in position in contrast meter scale facies sequences related to periodic channel bell avulsion may show relatively abrupt changes in facies and paleocurrent direction simulation models suggest that the number of such avulsion related facies changes in any overbank sequence bounded above and below by channel belt deposits is on the order of 1 to 10 this is confirmed using an ancient example in this example the average thickness of each avulsion bounded overbank facies sequence was 3 m assuming an average recurrence interval for avulsions of about 1 000 ye rs the mean overbank deposition rate was about 3 mm per year

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

changes in the magnitude and frequency of late holocene monsoon floods on the narmada river central india during the past three decades the narmada river of monsoon dominated central india has undergone extraordinarily large floods that rank among the highest recorded rainfall runoff discharges per drainage area in the world the floods on this river are a direct result of intense tropical cyclones embedded within the summer monsoon circulation the cluster of extreme floods in the past few decades represents an anomalous increase in both the magnitude and frequency of large floods when compared with the 1700 yr record of paleoflood deposits on this river sand deposits from recent floods consistently blanket older flood deposits at numerous slack water paleoflood sites along a 15 km reach of the narmada river at the site of the highest flood deposits 4 5 sandy flood deposits yielding post a d 1950 14c dates cap an underlying sequence of 7 10 silty flood deposits with a minimum 14c age of 650 70 b p and a maximum age older than 1720 185 b p the post a d 1950 floods are thus the largest in at least the past several hundred years an undisturbed surface archaeological site of microlithic artifacts 0 5 m above the post 1950 flood sands provides further evidence that no significantly larger floods have occurred in at least the past 3000 yr incipient soil development on the buried surfaces of some of the higher paleoflood deposits indicates long intervals in the past when no floods reached the highest slack water site the largest flood in the 1951 1991 gaged record of the narmada river at mortakka 55 323 m3s 1 in 1961 is equivalent to a 1000 yr flood in a probability distribution based on the 1700 yr paleoflood record but is less than a 50 yr flood based on the 1951 1991 gaged record alone demonstrating the enormous recent increase in the frequency of severe floods this cluster of severe floods could reflect changes in either climate or land use a number of paleoflood studies in tropical storm regions show a similar increase in high magnitude floods within the past four decades suggesting a widespread climatic cause for this pattern

holocene environmental variability in southern greenland inferred from lake sediments abstract sediments from qipisarqo lake provide a continuous holocene paleoenvironmental record from southern greenland following deglaciation and glacio isostatic emergence of the basin from the sea 9100 cal yr b p proxies of lake paleoproductivity including biogenic silica and organic matter increased markedly until 6000 cal yr b p and thereafter remained stable over the ensuing warm three millennia subsequent decreases in these proxies most dramatically between 3000 and 2000 cal yr b p show the lake s responses to initial neoglacial cooling intervals of ameliorated limnological conditions occurred between 1300 and 900 and between 500 and 280 cal yr b p briefly interrupting the decreasing trend in productivity that culminated in the little ice age increased lake productivity during the latter half of the 20th century which reflects the limnological response to circum arctic warming still has not reached peak holocene values the neoglacial climate of the last 2000 yr includes the most rapid high amplitude environmental changes of the past nine millennia the norse thus migrated around the north atlantic ocean region in the most environmentally unstable period since deglaciation lacustrine sediment records provide a context with which to consider future environmental changes in the labrador sea region in particular any future warming will be superposed on a regional climate system that is currently exhibiting highly unstable behavior at submillennial timescales

late pleistocene evolution of the lower mississippi river valley southern missouri to arkansas the mississippi river served as the principal conduit for meltwaters discharging from the southern margins of north american ice sheets the northern half of the mississippi river alluvial valley in missouri and arkansas can be subdivided into two distinct channel courses the western and eastern lowlands which are separated by crowleys ridge the eastern lowlands contain two entry points the bell city oran and thebes gaps the latter is a narrow bedrock gorge that contains the modern river this paper summarizes a model for evolution of channel courses in the western and eastern lowlands during the illinoian and wisconsin glacial stages for the western lowlands stratigraphic relations between loess units and subjacent fluvial deposits show that major continuous terrace surfaces or valley trains are illinoian or late wisconsin in age investigations of tributary valley fills further show the western lowlands were deeply incised during the early to middle wisconsin stage then aggraded during the late wisconsin stage to such an extent that tributary valleys were backfilled with slackwater deposits moreover analysis of loess thinning and fining trends shows that early to middle wisconsin roxana silt and the late wisconsin peoria loess covers on western lowlands valley trains were derived from deflation of valley trains in the eastern lowlands we conclude that the western lowlands were the primary mississippi river course during illinoian deglaciation but were abandoned shortly thereafter then episodically reoccupied during the late wisconsin stage for the eastern lowlands course valley trains of early to middle wisconsin age are not preserved with the exception of a small remnant where the mississippi river broke through a gap in the southern margins of crowleys ridge and reentered the western lowlands all valley trains in the eastern lowlands are late wisconsin age a series of discontinuous terrace surfaces in the bell city oran gap represent dissected remnants of the primary late wisconsin full glacial and early late glacial course of the mississippi river or combined mississippi and ohio rivers whereas younger continuous braided stream surfaces in the bell city oran and thebes gap courses represent valley trains of latest wisconsin and earliest holocene age hence the bell city oran gap was the primary course during the entire wisconsin stage and the thebes gap was permanently occupied in earliest holocene time as much as 5 m difference in elevation between successive late wisconsin terrace surfaces of the eastern lowlands indicates that valley trains were rapidly constructed incised and abandoned in response to fluctuations in the delivery of meltwater and outwash from the former ice margin moreover a variety of data indicates that deglacial meltwater floods were commonly of sufficient magnitude to overflow from the primary course in the bell city oran gap throughout the late wisconsin substage floodwaters overflowed into the western lowlands constructed a series of secondary valley trains and filled tributary valleys with slackwater deposits during the latest wisconsin stage perhaps in association with the drainage of glacial lake agassiz floodwaters overflowed into the western lowlands and broke through the thebes gap the charleston fan represents the initial deposits of the thebes gap course following deposition of a large crevasse splay at the western lowlands entrance that course was no longer active but flow was routed through the thebes gap during periods of high magnitude flooding until the bell city oran gap was abandoned and the thebes gap course was permanently occupied during earliest holocene time

airborne lidar in support of geomorphological and hydraulic modelling this paper considers the application of airborne laser altimetry lidar to the provision of elevation data at accuracies and spatial densities commensurate with the current generation of high resolution hydraulic models three sets of issues are addressed with reference to a telemac 2d model of a morphologically complex estuary in eastern england first the quality of airborne lidar data is assessed via multiscale calibration against surveyed sections and supplementary control points second image processing techniques are used for i identification of multiple regions of interest within large lidar mosaics ii subregional infilling of voids left by data drop outs iii filtering and subsampling to match topographic information content with model resolution and the density of the computational mesh third the implications of improved terrain data are considered with reference to the estimation of elevations and potential tidal volumes for a number of discrete flood compartments and the modelling of hypothetical inundation scenarios after minor offset correction to ensure registration with local benchmarks the quality of lidar elevation data within a 12 km x 4 kin coverage is found to be consistent with the published specification 0 10 to 0 15 m image processing tools provide an efficient means of managing information content and interfacing this with the gis based functionality of the preprocessing software used in conjunction with the hydraulic model the accuracy and spatial resolution of the lidar data allow the identification of subtle but important topographic variations between adjacent flood compartments in many cases differences in model results obtained using these data relative to previously estimated average flood compartment elevations are small importantly however lidar provides topographic information at an accuracy and resolution close to the present limits of model representation reliable representation of form allows the modeller to concentrate on the physical aspects of model parameterization whilst minimizing the conflation of parameter effects with those of poorly constrained geometric representation copyright c 2003 john wiley sons ltd

north atlantic oscillation dynamics recorded in greenland ice cores carefully selected ice core data from greenland can be used to reconstruct an annual proxy north atlantic oscillation nao index this index for the past 350 years indicates that the nao is an intermittent climate oscillation with temporally active coherent and passive incoherent phases no indication for a single persistent multiannual nao frequency is found in active phases most of the energy is located in the frequency band with periods less than about 15 years in addition variability on time scales of 80 to 90 years has been observed since the mid 19th century

late quaternary alluvial history of the northwestern deccan upland region continental and oceanic sediments from tropical africa australia and south america have recorded analogous changes in climate and stream behaviour during the late quaternary1 4 recently data from north central india have provided evidence for late quaternary changes in river regime in response to global changes in climate in the intertropical zone4 5 here we report evidence for late quaternary river metamorphosis6 from the northwestern deccan upland region of india radiocarbon dates combined with stratigraphic data have allowed the identification of major episodes of erosion and deposition7 8 supporting evidence from the arabian sea2 3 demonstrates that the successive phases of aggradation and incision are linked to late quaternary climatic changes7 8

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

effect of sediment transport boundary conditions on the numerical modeling of bed morphodynamics abstractexperimental sediment transport and river morphologic studies in laboratory flumes can use two sediment supply methods an imposed feed at the upstream end or a recirculation of sediment f

a revised chronology of key vatnajokull iceland outlet glaciers during the little ice age glacier fluctuations from key vatnajokull outlets have been redated using tephrochronology coupled with two lichenometric techniques to ascertain the timing of the little ice age lia maximum in southeast iceland an updated tephrochronology for southeast iceland both the number of tephra layers present and their geochemical signatures indicates a lia maximum for both glaciers between ad 1755 and 1873 based on a population gradient approach lichenometrically dated moraines along the margins of skalafellsjokull and heinabergsjokull narrow this window to the early to mid 19th century respectively these revised chronologies in addition to emerging evidence from elsewhere in iceland support a late 18th to early 19th century lia glacier maximum in contrast the norwegian lia glacial maximum is strongly centred around ad 1750 this implies differing glaciological responses to secular shifts in the north atlantic oscillation such revisions to the vatnajokull record are crucial as accurately identifying the timing and delimiting the spatial extent of the icelandic lia glacier maximum will allow further light to be shed on glacier climate interactions in the north atlantic

two dimensional hydraulic flood modelling using a finite element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry airborne scanning laser altimetry lidar is an important new data source that can provide two dimensional river flood models with spatially distributed floodplain topography for model bathymetry together with vegetation heights for parameterization of model friction methods are described for improving such models by decomposing the model s finite element mesh to reflect floodplain vegetation features such as hedges and trees having different frictional properties to their surroundings and significant floodplain topographic features having high height curvatures the decomposition is achieved using an image segmentation system that converts the lidar height image into separate images of surface topography and vegetation height at each point the vegetation height map is used to estimate a friction factor at each mesh node the spatially distributed friction model has the advantage that it is physically based and removes the need for a model calibration exercise in which free parameters specifying friction in the channel and floodplain are adjusted to achieve best fit between modelled and observed flood extents the scheme was tested in a modelling study of a flood that occurred on the river severn uk in 1998 a satellite synthetic aperture radar image of flood extent was used to validate the model predictions the simulated hydraulics using the decomposed mesh gave a better representation of the observed flood extent than the more simplistic but computationally efficient approach of sampling topography and vegetation friction factors on to larger floodplain elements in an undecomposed mesh as well as the traditional approach using no lidar derived data but simply using a constant floodplain friction factor use of the decomposed mesh also allowed velocity variations to be predicted in the neighbourhood of vegetation features such as hedges these variations could be of use in predicting localized erosion and deposition patterns that might result in the event of a flood copyright 2003 john wiley sons ltd

contrasting development patterns of crevasse channel deposits in cretaceous alluvial successions korea abstract the eumsung and pyonghae basins both of cretaceous age in korea comprise a thick alluvial sequence of conglomerate sandstone and purplish siltstone laterally impersistent gravelly sandstone beds can be classified into two types based on bed geometry internal structure and occurrence a vertically stacked sheetlike bodies facies 1 and b migratory ribbon shaped bodies facies 2 facies 1 is characterized by symmetrical channel geometry with a large ratio of width to thickness of sandstone beds which are mostly stratified and bounded by relatively distinct lower and upper boundaries they are frequently found in aggradational style facies 2 shows asymmetric geometry with a relatively small ratio of width to thickness of sandstone beds it comprises massive cross stratified units bounded by sharp basal contacts and gradational upper boundaries which resulted from laterally shifting mode both types represent crevasse distributary channels developed in floodplain environments facies 1 is suggestive of gradual migration of crevasse distributary channels under the conditions of overall aggradation whereas facies 2 represents discrete abrupt diversion of crevasse channels these features are due to differences in floodplain gradients paleohydrology and trunk channel behaviour

impact of a lisbon type tsunami on the u k coastline and the implications for tsunami propagation over broad continental shelves 1 we investigate the propagation of tsunamis toward the european shelf break using six different initial conditions based on the 1755 lisbon earthquake in order to assess the hazard to this region only one of our source models an assumed earthquake magnitude of 8 7 mw with a zonal fault orientation resulted in significant wave heights at the u k coastline because of wave spreading only a fraction of the tsunami energy from such an event reaches the northwest european shelf which itself provides a further buffer through reflection and frictional dissipation however we found significant local reamplification due to wave interactions and resonance on the continental shelf the maximum elevations obtained were comparable to severe winter storm conditions but with extreme local variability in the tsunami amplitude our results suggest that the impact of any repeat of this event would be very sensitive to the precise location and orientation of the source deformation as well as by complex topographic interactions on the shelf the uncertainties arising from the combination of source orientation and bathymetric interaction suggest that any assessment of risk for places where tsunamis are likely should consider a large ensemble of initial conditions

river response to high frequency climate oscillations in southern europe over the past 200 k y a 200 k y chronology of river response to climate related environmental change has been established for northeast spain using newly developed luminescence dating techniques this constitutes the best documented record of late quaternary river behavior currently available for the north atlantic region and enables fluvial stratigraphies to be compared with high resolution ice core and marine oxygen isotope climate series pleistocene and holocene river aggradational episodes coincide with stadial or neoglacial events while phases of river incision occur during interstadial or interglacial periods alluviation and erosion cycles would appear to track variations in sediment supply controlled by vegetation cover and winter storm frequency

aggradation history and luminescence chronology of late quaternary semi arid sequences of the sabarmati basin gujarat western india the gujarat alluvial plain in the semi arid desert margin of the thar desert contains a record of continental quaternary sequences these sequences were built by drainages originating in the aravalli hills and flowing westward into the indian ocean stratigraphic studies of a part of the late quaternary succession in the sabarmati basin have resulted in a fourfold lithostratigraphic scheme the waghpur formation conglomeratic member sand member the mahesana formation lower heterolithic member upper sand member the akhaj formation and the sabarmati formation facies analysis distribution of conglomerates and cross bed azimuths of the clastic facies of the waghpur formation were used to infer ne sw trending semi arid alluvial fans the deposition of the overlying heterolithic member took place in ephemeral streams influenced by episodic flows and aeolian reworking the upper member of the mahesana formation represents aeolian and older levee deposits feasibility studies of thermoluminescence tl and infra red stimulated luminescence irsl dating on the sabarmati succession yielded stratigraphically consistent ages ranging from 5 ka to 300 ka for two samples tl ages on quartz and irsl ages on feldspar separates were consistent these results together with the stratigraphic and petrographic data reveal the following events in the accumulation history of the sabarmati sequence 1 1 significant aggradation at 300 ka gravel sand and at 58 ka sand and 2 2 pedogenesis bracketed to 58 39 ka the sabarmati river in its middle stretches follows a regional slope deviatory course interpreted previously to be a neotectonic adjustment within the cambay graben our chronological data suggest that this adjustment occurred possibly within the past 39 ka

alluvial paleosols and pedofacies sequences in the permian lower beaufort of the southwestern karoo basin south africa abstract three types of paleosol profiles are described as representative of the range of soil types that developed on the ancient alluvial plains of the southwestern karoo basin during the late permian continuous 3 dimensional exposures of the lower beaufort adelaide subgroup strata allow detailed sedimentological taphonomic and paleopedological observation of thick floodplain sequences that contain numerous stacked paleosol profiles various floodplain strata contain characteristic paleosol profiles that are regulated by the periodicity and competence of overbank flooding both of which decrease with increasing distance from the contributing channel paleosols developed in levee or channel bank deposits are immature calcic entisols displaying evidence of early carbonate translocation but without well developed horizonation proximal floodbasin paleosols at the foot of the meanderbelt slope are mature calcic vertisols with more fully developed profiles containing zones of both carbonate and clay illuviation as well as some groundwater calcretes slickensided stress argillans in the b horizons are indicative of multiple cycles of wetting and drying distal floodbasin paleosols are dominated by hydromorphic and evaporitic processes as a result of their axial position in the floodbasin sheet like networks of mudcrack casts composed of calcretized aeolian sand and silt suggest that dust was a major source of calcium carbonate to the e soils the paleosols are interpreted as having formed under warm to hot semi arid climatic conditions with a strongly seasonal rainfall of 500 to 800 mm per annum and a mean annual moisture deficiency the geomorphic setting was similar to the holocene indo gangetic alluvial plain vertebrate burrow casts in the proximal floodbasin facies indicate a minimum depth to watertable of 150 cm the distribution of rooted horizons reflects dense vegetation flanking major drainage channels and sparse cover in the distal floodbasin a simple stratigraphic sequence of once laterally continuous paleosols is termed a pedofacies stacked sequences of pedofacies within approximately 20 50 m thick and 100 250 m thick stratigraphic successions reflect second and first order sedimentary cycles respectively both scales of cyclicity are attributed to autocyclically controlled avulsions of differentially aggrading channels in the first instance and of complete drainage networks in the second

late quaternary geomorphic evolution of the lower narmada valley western india implications for neotectonic activity along the narmada son fault geomorphic data combined with stratigraphic studies provide significant information to constrain timing and amount of fault movement the lower narmada valley lies astride the narmada son fault nsf an important ene wsw trending tectonic element responsible for the current intraplate seismicity being experienced in the central part of the indian plate varying nature and degree of tectonic movements along the nsf during late pleistocene and holocene have produced four geomorphic surfaces in the lower narmada valley the alluvial plain s1 ravine surface s2 a gravelly fan surface s3 and the valley fill terrace surface s4 two major phases of tectonic movements in a compressive stress regime are recorded along the nsf slow synsedimentary subsidence of the basin during late pleistocene due to differential movement followed by inversion of the basin during the holocene marked by differential uplift along the nsf the study suggests that the inversion of the basin is in response to the significant increase in the intensity of compressive stresses in the indian plate mainly during the early holocene the present incisive drainage and recent seismic activity indicate that the compressive stresses continue to accumulate along the nsf due to continued northward movement of the indian plate

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

integration of channel and floodplain suites i developmental sequence and lateral relations of alluvial paleosols abstract the lower eocene willwood formation of the bighorn basin northwest wyoming consists of about 770 m of alluvial rocks that exhibit extensive mechanical and geochemical modifications resulting from eocene pedogenesis willwood paleosols vary considerably in their relative degrees of maturity maturity is defined as stage of development as a function of the amount of time required to form five arbitrary stages are proposed to distinguish these soils of different maturities in the willwood formation stage 1 soils the least mature are entisols stage 2 and stage 3 soils are intermediate in maturity and are probably alfisols and stage 4 and stage 5 soils the most mature are spodosols these stages are not only time progressive elements of an in situ maturation sequence for w llwood soil formation but in the lateral dimension they are also usually distributed sequentially study of willwood paleosols indicates that an inverse relationship exists between soil maturity and short term sediment accumulation rate the least mature willwood paleosols formed in areas of relatively high net rates of sediment accumulation on 1 channel levee and crevasse splay sediments of the proximal alluvial ridge and 2 deposits filling large and small paleovalleys formed by major episodes of gullying lowered baselevels in contrast the fine grained sediments of the distal floodplain where net sediment accumulation rates were relatively low experienced development of much more mature soils soils of intermediate maturities occur in the order of their stage on intervening proximal floodplain and distal alluvial ridge sediments adjacent bodies of sedimentary rock that differ in their ancient soil properties because of distance from areas of relatively high sediment accumulation are denoted by the new term pedofacies the remarkable sequence of paleosols in the willwood formation clearly illustrates several important principles of soil sediment interrelationships in aggrading alluvial systems that have broad application to other deposits this is especially true in view of the widespread distribution of paleosols in nearly all ancient fluvial rocks further study of willwood paleosols will not only enable precise lateral correlation of coeval alluvial sediments and thereby fluvial sedimentary events from the distal to the proximal realms of the floodplain but will also contribute to increasingly informative evaluations of the nature tempo and mode of alluvial succession

sedimentology geochemistry and osl dating of the alluvial succession in the northern gujarat alluvial plain western india a record to evaluate the sensitivity of a semiarid fluvial system to the climatic and tectonic forcing since the late marine isotopic stage 3 abstract the alluvial successions in the northern gujarat alluvial plain western india have been investigated for reconstructing the climatic fluctuations during the last 40 ka alluvial architecture and geochemical proxies indicate prevalence of a strengthened indian summer monsoon ism with fluctuations between the late marine isotopic stage 3 mis 3 37 ka to the early mis 2 27 ka a gradual onset of aridity declining ism after 27 ka with peak aridity at 22 ka is observed a gradual strengthening of ism at around 18 and 12 ka followed by a short reversal in ism intensity between 12 and 11 ka is attributed to the younger dryas yd cooling event the aeolian sand sheet dated to 6 and 3 5 ka represents the onset of regional aridity following this a short lived humid phase was observed after 2 ka which includes the medieval warm period mwp the study suggests that the variability in the ism to the latitudinal migration of the inter tropical convergence zone was caused by insolation driven cooling and warming events in the north atlantic the incision of the valley fill alluvium occurred in two distinct phases the older incision phase occurred after 11 ka and before 6 ka whereas the younger incision phase that led to the development of present day topography is bracketed between 3 5 ka and before 1 ka the older incision phase is ascribed to the early to mid holocene enhanced ism climatically driven whereas the younger incision seems to be modulated by the activation of basement faults tectonically driven

examination of generation mechanisms for an english channel meteotsunami combining observations and modeling abstracton the morning of 23 june 2016 a 0 70 m meteotsunami was observed in the english channel between the united kingdom and france this wave was measured by several tide gauges and coincided

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

late quaternary environments in north central india microfossil sediment and oxygen isotope studies of deep sea cores from the bay of bengal and northern arabian sea1 5 have revealed strong contrasts between high late pleistocene and low early holocene salinity values3 indicative of major changes in runoff from the large rivers of southern asia2 3 here we present the first radiocarbon dated continental evidence for late quaternary changes in river regime and loess accumulation in this region our data support earlier palaeoclimatic inferences based solely on oceanic evidence2 3 have important implications for fluvial palaeohydrology6 and provide clear environmental constraints against which to test existing regional models of prehistoric land use and early agriculture 7 9

holocene climatic changes in iceland evidence from modelling glacier length fluctuations at solheimajokull abstract we use a coupled energy balance glacier flow model to reconstruct holocene climate from a 5000 yr record of glacier length fluctuations at solheimajokull an outlet glacier in southern iceland the climatic reconstruction is presented in terms of equilibrium line altitude and is translated to envelopes of possible temperature and precipitation changes the reconstruction is highly resolved between ad 1700 and 1990 the 20th century retreat of the glacier resulted from a warming between ad 1920 and 1940 while the advance since ad 1970 was in response to both a cooling and a precipitation increase after ad 1940 the early 18th century climate of iceland was warm comparable to that of the early 20th century while the coldest period in recent history occurred during the 1780s earlier holocene glacier advances at about 5000 3100 and 1400 yr bp and in the 10th and 14th centuries ad resulted from cooling of 1 2 c and correlate with worldwide glacier expansion atmospheric changes in greenland and changes in ocean circulation north of iceland glacier expansions follow periods when sea ice is extensive in the greenland and barents sea resulting temperature changes mean that natural climatic variability has a large signature in iceland making it difficult to isolate any longer term trends such as an enhanced anthropogenic signal

rock varnish microlamination dating of late quaternary geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts in this study we establish a generalized late quaternary i e 0 300 ka varnish layering sequence for the drylands of western usa and tentatively correlate it with the specmap oxygen isotope record we then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late quaternary geomorphic features in the study region vml dating of alluvial fan deposits in death valley of eastern california indicates that during the mid to late pleistocene 5 15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation during the holocene interglacial time however 0 5 1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate vml dating of alluvial desert pavements in death valley and the mojave desert reveals that pavements can be developed rapidly

carbon isotopic composition of lignin biomarkers evidence of grassland over the gangetic plain during lgm abstract carbon isotope 13 c compositions of total organic carbon toc as well as several extracted higher plant derived lignin biomarkers along with the recovery of grass phytoliths provide the first direct evidence of existence of extensive grass land c4 vegetation over the ganges deltaic plain during the last glacial maximum lgm the earliest holocene 9 ka is marked by pronounced 13 c depletion in the lignin phenols coinciding with rapid sea level rise intensified monsoon and replacement of grassland vegetation by mangroves another c4 invasion phase is identified during the late holocene 6 2 ka both the lgm and late holocene c4 phases coincide with the well known monsoon minima the study suggests that change in pco 2 might not be the singular driver of vegetation change as proposed recently and the climate models must take the monsoon like mega climate processes into account for reconstructing the glacial biomes

fluvial responses to climate and sea level change a review and look forward summary fluvial landforms and deposits provide one of the most readily studied quaternary continental records and alluvial strata represent an important component in most ancient continental interior and continental margin successions moreover studies of the long term dynamics of fluvial systems and their responses to external or allogenic controls can play important roles in research concerning both global change and sequence stratigraphy as well as in studies of the dynamic interactions between tectonic activity and surface processes these themes were energized in the final decades of the twentieth century and may become increasingly important in the first decades of this millennium this review paper provides a historical perspective on the development of ideas in the fields of geomorphology quaternary geology vs sedimentary geology and then summarizes key processes that operate to produce alluvial stratigraphic records over time scales of 103 106 years of particular interest are changes in discharge regimes sediment supply and sediment storage en route from source terrains to sedimentary basins as well as changes in sea level and the concept of accommodation late quaternary stratigraphic records from the loire france mississippi usa colorado texas usa and rhine meuse the netherlands rivers are used to illustrate the influences of climate change on continental interior rivers as well as the influence of interacting climate and sea level change on continental margin systems the paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea level change at present empirical field based research on fluvial response to climate and sea level change lags behind a the global change community s understanding of the magnitude and frequency of climate and sea level change b the sequence stratigraphic community s desire to interpret climate and especially sea level change as forcing mechanisms and c the modelling community s ability to generate numerical and physical models of surface processes and their stratigraphic results a major challenge for the future is to catch up which will require the development of more detailed and sophisticated quaternary stratigraphic sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings there is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter 102 103 years and longer 104 106 years time scales than has commonly been the case to date as well as in larger river systems from source to sink studies of quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre quaternary rock record

holocene fluctuations of a polythermal glacier in high alpine eastern jotunheimen central southern norway abstract bukkehammarbreen is a polythermal cirque glacier lying in the permafrost zone of eastern jotunheimen central southern norway in the proglacial lake bukkehammartjorna sediment analyses of loss on ignition loi magnetic susceptibility and analyses of grain size distribution have been used to reconstruct holocene variations in glacier activity and other catchment processes the glacier has low sediment production hence a low signal to noise ratio of minerogenic sediment flux is found grain size analyses are used to enhance the glacigenic signal and to detect glacier variations and other changes in sediment input the sedimentological record from bukkehammartjorn is compared with three other lake records from the same region in order to separate the glacial signal from variations in organic production and episodes of enhanced non glacial minerogenic sedimentation subsequent to the deglaciation after the younger dryas a preboreal glacial advance culminated before 10 100 cal bp this was followed by a prolonged period with no glaciers in the catchment until 7500 cal bp after which there is evidence of limited glacier activity lasting until 6800 cal bp between 6700 and 6000 cal bp the catchment was deglaciated after 6000 cal bp bukkehammarbreen reformed increasing in size towards 3800 cal bp with evidence for reduced glacier activity around 5200 cal bp a glacier with approximately similar size as at present has existed after 3800 cal bp the investigation has demonstrated the usefulness of multi site and multi parameter lacustrine investigations in reconstructing glacier fluctuations and for testing and validating the results the investigations have shown that grain size variations in sediment cores located at increasing distance from the meltwater inlet of a lake may provide an indicator of paraglacial activity in the catchment during the holocene the results also suggest that the lower altitudinal limit of permafrost in eastern jotunheimen remained below about 1800 m during the holocene

a comparison of the lichenometric and schmidt hammer dating techniques based on data from the proglacial areas of some icelandic glaciers abstract measurements of rhizocarpon section and schmidt hammer r values are reported from the proglacial geomorphic features on the forelands of the icelandic glaciers of kviarjokull holarjokull and heinabergsjokull oraefi and south vatnajokull sandfellsjokull and oldufellsjokull east m rdalsjokull and bruarjokull eyjabakkajokull and west snaefell north vatnajokull these data are used in reconstructions of patterns of glacier recession since the little ice age maximum and the geomorphic signals of climatic versus non climatic events are discussed age control was obtained from various dated substrates by utilizing historical accounts aerial photographs and grave stones three lichen growth rates are calculated a 0 51 mm a 1 corrected to 0 50 mm a 1 with a colonization lag time of

the last 140 ka in the afro asian arid semi arid transitional zone abstract during the last ten years a great number of geological or other proxy records provided radiocarbon u th or tl dated information on the past climatic oscillations in the arid semi arid zones extending between the atlantic and the pacific comparisons and a synthetic view of these results can now be attempted for the last 140 ka and compared with global changes as registered in oceanic or ice cores and with palaeomonsson models for this purpose wide spatial and time scales have to be used on the whole arid humid alternations roughly fit global changes cold phases corresponding to an extension of the arid areas to the south warm phases corresponding to the shrinking of the same to the north the last interglacial is associated with an increase of precipitation throughout the area considered isotopic stage 4 brings no evidence whatsoever of humid conditions two wetter episodes are registrated during stage 3 a major rainfall decrease is everywhere associated with the last glacial maximum 21 15 ka in most regions the arid or semi arid zones extending several hundred kilometers southwards relative to the present day pattern the two abrupt deglaciation steps and the younger dryas are recorded in all of the most sensitive regions at the margins of the present day monsoonal range during the holocene the precipitation increases everywhere by 100 400 mn relative to the present day values the optimum being at 8 5 6 5 ka a climatic deterioration follows with an irregular pattern of dry wet episodes according to the different geographic conditions the humid phase terminates at 3 5 3 ka in the whole transitional zone the major southward shift of the monsoonal precipitation range since its optimum some 8000 years ago fits the astronomical neoglacial trend and may possibly be correlated with past stage 5d although its rapidity and spatial importance may just reflect one of the sharp successive cold warm variations registered by grip during the whole stage 5

little ice age variations of outlet glaciers from the jostedalsbreen ice cap southern norway a regional lichenometric dating study of ice marginal moraine sequences and their climatic significance complex moraine ridge sequences in front of seven outlet glaciers of the jostedalsbreen ice cap austerdalsbreen bergsetbreen fabergstolsbreen lodalsbreen stegaholbreen tuftebreen bodalsbreen are dated using families of lichenometric dating curves established previously at an eighth outlet nigardsbreen applicability of the nigardsbreen curves at the regional level is tested using independent historical evidence moraines deposited during the present century are dated to an accuracy of 9 4 yr 16 0 and most of them are dated to an accuracy of 5 5 yr 9 4 results from the moraine sequences are combined to form a composite jostedalsbreen record median predicted dates for moraine ridges cluster around ad 1939 2 yr 1929 3 1908 3 1886 5 1875 2 1867 4 1855 3 1842 5 1822 5 1807 4 and 1785 5 at least four glaciers reached their little ice age maxima prior to ad 1780 two nigardsbreen and bodalsbreen at ca 1750 one fabergstolsbreen at ca 1705 stegaholbreen attained its maximum ca 1863 since the little ice age maximum and despite large differences in glacier size frontal variations of the various outlets have exhibited a high degree of synchroneity which suggests that the moraine sequences contain a sensitive record of high frequency climatic variations over the last ca 250 yr during the early twentieth century measured readvances of the order of 5 150 m over 1 10 yr led to moraine formation dendroclimatic evidence indicates that since the late eighteenth century moraine ridges formed about 5 yr after summer temperature minima and correlate with runs of cool summers temperature depression of 0 5 1 0 c below the ad 1700 1950 average almost simultaneous glacier advances appear to have been caused by reduced ablation this near immediate response to climatic variation by glacier tongues that descend to relative low altitudes is superimposed upon the longer term dynamic response of the ice cap to climate

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

sedimentology of the narmada alluvial fan western india abstract the narmada alluvial fan is one of the world s largest with an axial length of 23 km the architecture is dominated by debris flow deposits gms facies matrix support a clay content of 3 and clast contact indicate that the clast support mechanism resulted from a combination of buoyancy and dispersive pressure the other faci facies gsh planar cross stratified gravel facies gp1 and gp2 sand sheet facies sm and trough cross stratified sand facies st gms gsh and sm facies are debris flow and sheet flow deposits that aggraded the fan whereas gp1 and st are channel bars and channel fills that dominated the fan between major flood events the fan is characterised by subrounded to rounded clasts the rounding is due to the elongated catchment area upstream of the fan apex as clasts are rounded during prolonged bed load transport and are temporarily arrested upstream of the fan apex as channel bars these clasts are remobilized and entrained in debris flows on the fan during events of anomalous discharge storm events the basalt clasts show a progressive fall in maximum clast size from 150 cm to 10 cm away from the fan apex the narmada river exhibits discharges of up to 60 000 m3 s but due to reconfinement of the feeder channel resulting from tectonic reactivation of pre existing lineaments during the late pleistocene this does not aggrade the fan tectonism has influenced the location of the depositional site has provided the necessary physiographic contrast and has played an important role in the erosion of the fan whereas climate controlled primary and secondary processes have determined the nature of alluvial architecture

pleistocene stratigraphy in the southern lower mississippi valley abstract scientific inquiry into pleistocene stratigraphy of the lower mississippi valley lmv dates to early writings of european naturalists in the late 19th century by the early 20th century landscape evolution concepts stratigraphic models and regional syntheses had developed for most areas the 1944 monograph of h n fisk marks the advent of a predictive stratigraphic and landscape evolution model that links form and process to a predominantly glacioeustatic mechanism the fiskian model gained widespread acceptance and decades passed before significant alternate models began to emerge revised stratigraphic and geomorphic concepts are presently developing from newly acquired environmental and engineering data present scenarios classify pleistocene outcrop areas into erosional and constructional landscapes and veneers of eolian colluvial fluvial coastal and marine origin can drape both types of surfaces the southern lmv and adjacent gulf coastal plain gcp experienced significant landscape change during the pleistocene late tertiary pliocene to early pleistocene deposition of the upland complex was by streams with a high sand and gravel load relative to its mud load the regional drainage network and fluvial system behavior was probably significantly different from the modern braided stream alluvial fan complexes received sediment from highland source areas adjacent to the lmv and the glaciated mid continent it is plausible that part of upland complex deposition predates initial glacial advances from early to middle pleistocene an erosional landscape formed during a dissection period that chiefly postdates soil formation on stable landscape positions of the upland complex slope evolution truncated a regionally extensive geosol in multiple phases and parts of the erosion surface complex are graded to the oldest preserved constructional alluvial plains in present valleys toe and foot slope positions of the erosion surface complex and its correlative alluvial plains are presently delineated as the intermediate complex constructional landscapes formed at this time are sparsely preserved fisk s montgomery terrace in the lower red river valley lrrv is the best preserved example influences on the development of erosion surfaces in the lmv are not well understood however interactions of relative sea level fall climate change and epirogenic crustal movement are plausible factors from the latter part of middle pleistocene to the holocene there was widespread evolution of modern constructional landscapes constructional alluviation preserved lithofacies of mixed load laterally accreting meandering streams that developed over large areas of the southern lmv to form parts of the prairie complex lateral planation in valleys and stable rates of upland sediment generation were dominant processes during prairie complex deposition pleistocene stratigraphic examples considered important by fisk are still considered relevant to modern stratigraphic investigators presently pleistocene units of the southern lmv the adjacent lrrv and central gcp can be correlated only by relative stratigraphic relationships refined chronostratigraphic and paleoenvironmental models for these areas would help improve the understanding of the geomorphic influences on quaternary landscape evolution in the region