two dimensional numerical simulation of bed load transport of a finite depth sediment layer applications to channel flushing abstractnumerical modeling of bed load transport in shallow flows particularly oriented toward environmental flows is an active field of research nevertheless other possible applications exist

propagation pathways and fluid transport of hydrofractures in jointed and layered rocks in geothermal fields abstract palaeofluid transporting systems observed as networks of mineral filled veins in deeply eroded parts of extinct geothermal fields indicate that hydrofractures commonly supply fluids to geothermal fields here we examine well exposed vein networks that occur at crustal depths of around 1 5 km below the initial surface of the tertiary lava pile in north iceland the veins are located in the damage zone of a major fault zone that dissects basaltic lava flows the most common host rocks of geothermal fields in iceland the lava flows contain numerous weaknesses particularly columnar cooling joints and contacts for hydrofractures to supply fluids to geothermal fields the fractures must be able to propagate and transport fluids to the surface we explore hydrofracture pathway formation using boundary element models of hydrofractures with fluid overpressure varying linearly from 10 mpa at the fracture centre to 0 mpa at the fracture tip or the fluid front the hydrofractures propagate through a vertically jointed and horizontally layered pile of lava flows with a general rock matrix young s modulus of 1 10 10 pa and a poisson s ratio of 0 25 the joints and contacts between layers are modelled as internal springs each with a stiffness strength of 6 mpa m the location and sizes of discontinuities as well as the location of the hydrofracture tip vary between the models the results indicate that tensile stresses generated at the tip of an overpressured hydrofracture can open up horizontal and vertical discontinuities out to a considerable distance from the tip and that these discontinuities eventually link up to form the hydrofracture pathway analytical models indicate that for a hot spring of a given yield associated with a fault the dimensions of the fluid transporting part of the fault are likely to be similar for a typical normal fault and a strike slip fault also a hot spring of yield 180 l s the maximum in the low temperature fields of iceland can be supplied through a hydrofracture of aperture 3 mm and trace length 1 2 m these dimensions are very similar to those of typical veins in the studied networks buoyancy rather than excess pressure in the fluid source appears to be the primary driving force of hydrofractures in the geothermal fields of iceland

ore shoots in folded and fractured rocks insights from 3d modelling of the fosterville gold deposit victoria australia abstract at the fosterville gold deposit high concentrations of visible and refractory gold are hosted in arrays of quartz and quartz carbonate veins they are distributed in elongate zones to form south plunging ore shoots within a folded and fractured turbidite sequence here we distinguish the influence of faults versus folds at fosterville by assessing the deposit scale structural framework and hydrothermal fluid flow using a combination of 3d implicit modelling structural analysis and 3d fault slip dilation tendency analyses gold assay and bedding trend data from a large drillhole dataset were spatially interpolated and used to analyse and measure the orientation of ore bodies and folded host rocks field measurements of fold axis orientations were compared to bedding measurements in oriented drillcore bingham axial analysis of bedding trends and orientation data from a 3d implicit model both field and drill core structural data show that ore shoots at fosterville do not parallel the first order gently 10 south plunging folds instead the orientation of the ore shoots is coincident with an intersection lineation between steeply west dipping bedding parallel faults and moderately dipping linkage faults that obliquely cut across the main structural grain resulting in ore shoot plunges larger than 20 slip and dilation tendencies suggest that linkage faults had a higher likelihood of activity in the inferred far field stress regimes at the time of mineralisation relative to other structures at fosterville these linkage faults are therefore interpreted to have been preferential fluid flux conduits in the system despite appearing to be subordinate structures at the scale of the deposit this new structural model for fosterville highlights that fluid flow and ore shoot formation are strongly controlled by obliquely oriented structures that are unlike the main structural grain of first order folds and faults

northern iberian abrupt climate change dynamics during the last glacial cycle a view from lacustrine sediments abstract we present a palaeoclimatic reconstruction of the last glacial cycle in iberia ca 120 000 11 600 cal yrs bp based on multi proxy reconstructions from lake sediments with robust chronologies and with a particular focus on abrupt climate changes the selected lake sequences provide an integrated approach from northern iberia exploring temperature conditions humidity variations and land sea comparisons during the most relevant climate transitions of the last glacial period thus we present evidence that demonstrates i cold but relatively humid conditions during the transition from mis 5 to mis 4 which prevailed until ca 60 000 cal yrs bp in northern iberia ii a general tendency towards greater aridity during mis 4 and mis 3 ca 60 000 to 23 500 cal yrs bp punctuated by abrupt climate changes related to heinrich events he iii a complex highly variable climate during mis 2 23 500 to 14 600 cal yrs bp with the mystery interval mi 18 500 to 14 600 cal yrs bp and not the global last glacial maximum lgm 23 000 to 19 000 cal yrs bp as the coldest and most arid period the last glacial transition starts in synchrony with greenland ice records at 14 600 cal yrs bp but the temperature increase was not so abrupt in the iberian records and the highest humidity was attained during the allerod gi 1a to gi 1c and not during the bolling gi 1e period the younger dryas event gs 1 is discernible in northern iberian lake records as a cold and dry interval although iberian vegetation records present a geographically variable signal for this interval perhaps related to vegetation resilience

coupled and decoupled numerical modeling of flow and morphological evolution in alluvial rivers existing numerical river models are mostly built upon asynchronous solution of simplified governing equations the strong coupling between water flow sediment transport and morphological evolution is thus ignored to a certain extent an earlier study led to the development of a fully coupled model and identified the impacts of simplifications in the water sediment mixture and global bed material continuity equations as well as of the asynchronous solution procedure for aggradation processes this paper presents the results of an extended study along this line highlighting the impacts on both aggradation and degradation processes simplifications in the continuity equations for the water sediment mixture and bed material are found to have negligible effects on degradation this is however in contrast to aggradation processes in which the errors purely due to simplified continuity equations can be significant transiently the asynchronous solution procedure is found to entail appreciable inaccuracy for both aggradation and degradation processes further the asynchronous solution procedure can render the physical problem mathematically ill posed by invoking an extra upstream boundary condition in the supercritical flow regime finally the impacts of simplified continuity equations and an asynchronous solution procedure are shown to be comparable with those of largely tuned friction factors indicating their significance in calibrating numerical river models it is concluded that the coupled system of complete governing equations needs to be synchronously solved for refined modeling of alluvial rivers

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

orbital and sub orbital scale climate impacts on vegetation of the western mediterranean basin over the last 48 000 yr article i nfo high resolution pollen analysis of alboran sea core md95 2043 provides a 48 ka continuous vegetation record that can be directly correlated with sea surface and deep water changes the reliability of this record is supported by comparison with that of padul sierra nevada spain marine isotope stage mis 3 was characterised by fluctuations in quercus forest cover in response to dansgaard oeschger climate variability mis 2 was characterised by the dominance of semi desert vegetation despite overall dry and cold conditions during mis 2 heinrich events hes 2 and 1 were distinguished from the last glacial maximum by more intensely arid conditions taxon specific vegetation responses to a tripartite climatic structure within the hes are observed in mis 1 the bolling allerod was marked by rapid afforestation while a re expansion of semi desert environments occurred during the younger dryas the maximum development of mixed quercus forest occurred between 11 7 and 5 4 cal ka bp with forest decline since 5 4 cal ka bp on orbital timescales a long term expansion of semi desert vegetation from mis 3 into mis 2 reflects global ice volume trends while holocene arboreal decline reflects summer insolation decrease the influence of precession on the amplitude of forest development and vegetation composition is also detected

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

glacial activity and catchment dynamics in northwest greece long term river behaviour and the slackwater sediment record for the last glacial to interglacial transition woodward j c hamlin r h b macklin m g hughes p d lewin j 2008 glacial activity and catchment dynamics in northwest greece long term river behaviour and the slackwater sediment record for the last glacial to interglacial transition geomorphology 101 1 2 44 67 sponsorship uk science and engineering research council woodward the school of geography at the university of leeds hamlin and the university of cambridge hughes the uk natural environment research council gr9 2916 and ip 754 0302 funded the bulk of the analyses reported here specialissue sp iss si

high sediment yields and cool wet winters test of last glacial paleoclimates in the northern mediterranean opposing models have been proposed for last glacial paleoclimates in the mediterranean area to discriminate between the alternative models we calculate variations in sediment yield within a high resolution stratigraphic framework developed for the alkyonides basin central greece latest quaternary highstand deposits are distinguised from lowstand lake corinth deposits on the basis of seismic reflection data and micropaleontological and palynological analyses of drop cores after depth conversion and calculation of solid sediment masses in successive time slices sediment discharge rates during the last glacial lowstand interval ca 70 12 ka are shown to have exceeded discharge rates during the preceeding interglacial highstand interval ca 128 70 ka by 60 implying enhanced seasonality during the glacial period with cool dry summer and wet winter conditions in the region sediment yield calculations can thus provide an empirical test of paleoclimate models and offer input to sequence stratigraphic models

holocene environmental change and river mouth sedimentation in the baie des anges french riviera abstract river mouths on the steep high relief coast of the french riviera exhibit thick sequences of holocene marine estuarine deltaic and river channel floodplain sediments that overlie basal fluvial pleistocene gravel gravel is uncommon in most of the early to middle holocene aggradational progradational marine estuarine deltaic sediments despite an ample supply from rock units in the steep adjoining uplands river mouth gravel is common only in late holocene river channels and in barrier beaches perched on finer grained nearshore sediments neither downslope grain size fining on alluvial fans nor sediment stacking patterns during sea level base level rise readily account for the lack of early to middle holocene gravel in the river mouth sediment wedges holocene sea level rise led to the storage of fine grained sediments in shallow marine estuarine and deltaic environments in the present coastal zone we infer that humid temperate conditions a dense forest cover landscape stabilization and a regular quiescent river flow regime associated with the atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early holocene sea level stabilization in the middle and late holocene coincided with a marked change in bioclimatic conditions toward the present mediterranean type regime which is characterized by a less dense forest cover soil erosion and episodic catastrophic floods the late holocene was thus a time of downstream bedload channel aggradation fine grained floodplain and paludal sedimentation and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments

turbiditic levee deposition in response to climate changes the var sedimentary ridge ligurian sea abstract article history received 31 may 2010received in revised form 25 october 2010accepted 25 october 2010available online 31 october 2010communicated by d j w piperkeywords last deglaciationoverbank depositsturbidity currentsvar sedimentary ridgeligurian sea the var turbiditic system located in the ligurian sea se france is an intermediate mud sand rich system theparticularityofthevardeep seafanisitssinglechannelwithabruptbendsanditsasymmetricandhyper developed levee on the right hand side the var sedimentary ridge long term sediment accumulation on thevar sedimentary ridge makes this an ideal target for studying the link between onshore climate change anddeep sea turbidite stratigraphy this paper focuses on the establishment of the rst detailed stratigraphy ofthe levee which is used to analyze the timing of overbank deposition throughout the last deglaciation mainresults indicate that high variability in turbidite frequencies and deposition rates along the var sedimentaryridgearedeterminedbytwomainparameters 1 theprogressivedecreaseoftheleveeheightcontrollingtheabilityofturbiditycurrentstospilloutfromthechannelontothelevee and2 climaticvariationsaffectingthedrainage basin in particular changes in glacial condition since late last glacial maximum to early holocene compared to other deep water areas this study con rms the ability of turbiditic systems to record pastclimatic events on millennial timescales and underlines the in uence of european deglaciation on theobserved decrease in turbidite activity in the var canyon the presence of a very narrow continental shelf andasingle largechannel leveesystemmakesthevarsedimentaryridgeauniqueexampleofclimate controlledturbiditic accumulations 2010 elsevier b v all rights reserved

pinpointing deep geothermal upflow in zones of complex tectono volcanic degassing new insights from aluto volcano main ethiopian rift the project was financed in the framework of the volkswagen foundation s postdoctoral fellowships for african researchers in the engineering sciences reference 90017

millennial scale response of a western mediterranean river to late quaternary climate changes a view from the deep sea abstractalthough it is widely accepted that erosion and sediment transfer respond to millennial scale climatic variability these changes remain difficult to detect in marine sedimentary archives in the var sediment routing system northwestern mediterranean sea the absence of a continental shelf results in a direct connection between the var river mouth and the deep basin during both highstand and lowstand conditions this makes the var sediment routing system an ideal target to test whether rivers can transmit climate driven high frequency changes in sediment flux to the ocean on the basis of an unprecedented centennial to millennial scale resolution in turbidite sequences we reconstructed the activity of turbidity current overflows along the deep sea var sedimentary ridge over the past 75 kyr the overflow activity is highest one event every 10 30 yr during maximum glacial conditions 30 kyr 16 kyr ago ka and rapidly decreases down to one event every 100 500 yr during the last glacial inte

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

structural lithological and geodynamic controls on geothermal activity in the menderes geothermal province western anatolia turkey western turkey belongs to the regions with the highest geothermal potential in the world resulting in significant electricity production from geothermal resources located predominantly in the menderes massif although geothermal exploitation is increasingly ongoing geological and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood several studies on the menderes massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin this paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs on the basis of field studies we suggest that crustal scale low angle normal faults convey hot fluids to the surface and represent the first order control on geothermal systems at the basin scale connected on low angle normal faults kilometric high angle transfer faults are characterized by dilational jogs where fluids may be strongly focused in addition favourable lithologies in the basement e g karstic marble could play a critical role in the localization of geothermal reservoirs finally a compilation of geochemical data at the scale of the menderes massif suggests an important role of the large mantle thermal anomaly which is related to the hellenic subduction heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low angle faults hence geothermal activity in the menderes massif is not of magmatic origin but rather associated with active extensional tectonics related to the aegean slab dynamics i e slab retreat and tearing

carbon dioxide degassing by advective flow from usu volcano japan magmatic carbon dioxide co2 degassing has been documented before the 31 march 2000 eruption of usu volcano hokkaido japan six months before the eruption an increase in co2 flux was detected on the summit caldera from 120 september 1998 to 340 metric tons per day september 1999 followed by a sudden decrease to 39 metric tons per day in june 2000 3 months after the eruption the change in co2 flux and seismic observations suggests that before the eruption advective processes controlled gas migration toward the surface the decrease in flux after the eruption at the summit caldera could be due to a rapid release of co2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

depth averaged two dimensional numerical modeling of unsteady flow and nonuniform sediment transport in open channels a depth averaged two dimensional 2d numerical model for unsteady flow and nonuniform sediment transport in open channels is established using the finite volume method on a nonstaggered curvilinear grid the 2d shallow water equations are solved by the isimple c n algorithms with the rhie and chow s momentum interpolation technique the proposed sediment transport model adopts a nonequilibrium approach for nonuniform total load sediment transport the bed load and suspended load are calculated separately or jointly according to sediment transport mode the sediment transport capacity is determined by four formulas which are capable of accounting for the hiding and exposure effects among different size classes an empirical formula is proposed to consider the effects of the gravity on the sediment transport capacity and the bed load movement direction in channels with steep slopes flow and sediment transport are simulated in a decoupled manner but the sediment module adopts a coupling procedure for the computations of sediment transport bed change and bed material sorting the model has been tested against several experimental and field cases showing good agreement between the simulated results and measured data

linking gas fluxes at earth s surface with fracture zones in an active geothermal field the percolation of fluids is of utmost relevance for the utilization of underground resources however the location and occurrence of fractures are not always known and important characteristics of faults such as stress state and permeability are commonly uncertain using a case study at the brady s geothermal field in nevada usa we demonstrate how permeable fractures can be identified and assessed by combining fault stress models with measurements of diffuse degassing and emanations at earth s surface areas of maximum gas emissions and emanations correspond to fault segments with increased slip and dilation tendency and represent a fingerprint of the geothermal system at depth thus linking gas fluxes with fault stress models serves as a measure of the connectivity between surface and subsurface

magmatic volatiles to assess permeable volcano tectonic structures in the los humeros geothermal field mexico abstract magmatic volatiles can be considered as the surface fingerprint of active volcanic systems both during periods of quiescent and eruptive volcanic activity the spatial variability of gas emissions at earth s surface is a proxy for structural discontinuities in the subsurface of volcanic systems we conducted extensive and regular spaced soil gas surveys within the los humeros geothermal field to improve the understanding of the structural control on fluid flow surveys at different scales were performed with the aim to i identify areas of increased gas emissions reservoir scale ii their relation to un known volcano tectonic structures fault scale favoring fluid flow and iii determine the origin of gas emissions herein we show results from a co2 efflux scouting survey which was performed across the main geothermal production zone 6 km 4 km together with soil temperature measurements we identified five areas with increased co2 emissions where further sampling was performed with denser sampling grids to understand the fault zone architecture and local variations in gas emissions co2 efflux values range from below detection limit of the device to 1464 g m 2 d 1 with a total output of 87 t d 1 across an area of 13 7 km2 furthermore 13cco2 and 3he 4he analyses complemented the dataset in order to assess the origin of soil gases carbon isotopic data cover a broad spectrum from biogenous to endogenous sources determined 3he 4he ratios indicate a mantle component in the samples of up to 65 being most evident in the northwestern and southwestern part of the study area we show that a systematic sampling approach on reservoir scale is necessary for the identification and assessment of major permeable fault segments the combined processing of co2 efflux and 13cco2 facilitated the detection of permeable structural segments with a connection to the deep high temperature geothermal reservoir also in areas with low to intermediate co2 emissions the results of this study complement existing geophysical datasets and define further promising areas for future exploration activities in the north and southwestern sector of the production field

diffuse surface emanations as indicator of structural permeability in fault controlled geothermal systems abstract diffuse degassing processes provide valuable information on geothermal reservoir characteristics not only in the context of monitoring but also for exploration purposes areas with increased gas emissions can be indicative of major upflow zones from the reservoir through deep reaching permeable fault zones these fault zones may act as preferential target areas for geothermal production drillings in this study it is successfully demonstrated that diffuse degassing measurements can be used for the detection and characterization of permeable structural elements the combination of following techniques has been applied at the brady s geothermal system in the basin and range province nevada usa accumulation chamber method for carbon dioxide and hydrogen sulfide measurements alpha spectroscopic measurements of radon and thoron activity concentrations and gamma spectroscopic measurements of selected nuclides

flow velocities sediment transport and morphological change in the swash zone of two contrasting beaches abstract as part of a large uk research project focussing on the role of swash on shoreline change two field experiments were conducted on contrasting sandy beaches a flatter dissipative beach and a steeper intermediate beach this paper describes almost 300 h of nearshore velocity data collected during this project supplemented by suspended sediment transport sediment tracer and beach profile data during both field experiments the upper part of the beach experienced progressive accretion indicating that onshore sediment transport prevailed in the swash and inner surf zones suspended sediment transport and tracer dispersal were also onshore the associated cross shore flow field was however dominated by offshore directed mean flows especially on the steeper beach velocity skewness defined as u 3 u 2 1 5 where u is the cross shore velocity and kurtosis defined as u 3 u u 2 2 were mainly directed offshore implying that energetics based sediment transport models are unable to predict the direction of sediment transport in the swash zone possible explanations for the observed accretion include enhanced bed shear stress on the uprush due to in exfiltration effects flow acceleration and or bore turbulence and advection of bore entrained sediment into the swash zone

sediment transport by waves and currents a bed load model based on a generalization of bagnold s 1954 constitutive equations together with the assumption of similarity profiles for velocity and concentration was proposed for sediment transport by waves by sleath 1994 this model is now extended to wave current flows and applied to three different situations a oscillatory flows with superimposed currents b net transport produced by progressive waves over a flat horizontal bed and c longshore transport induced by waves approaching a beach in all three cases the model gives reasonable agreement with experiment in the case of longshore transport the model produces almost the same formula as that of the coastal engineering research center 1977 apart from additional terms for density and grain size

sediment transport formula for steep channels a description is given and results presented of experiments to investigate the sediment capacity of stream flows on flume slopes of up to 20 a comparison of the results with values predicted by the meyer peter mueller equation shows that the latter equation seriously underestimates sediment transport capacity on slopes steeper than 3 mainly because of deficiencies in the form resistance factor a new equation is proposed giving the transport capacity for materials with grain sizes larger than 0 4 mm 0 016 in the equation is calibrated by both the original meyer peter data and new steep flume experiments and modified to incorporate the effect of nonuniform sediment grain size distributions with flow depths calculated by the manning strickler equation the new equation still gives excellent estimates of sediment capacity

enhanced aridity and atmospheric high pressure stability over the western mediterranean during the north atlantic cold events of the past 50 k y multiproxy paleoenvironmental records pollen and planktonic isotope from ocean drilling program site 976 alboran sea document rapid ocean and climate variations during the last glacial that follow the dansgaard oeschger climate oscillations seen in the greenland ice core records thus suggesting a close link of the mediterranean climate swings with north atlantic climates continental conditions rapidly oscillated through cold arid and warm wet conditions in the course of stadial interstadial climate jumps at the time of heinrich events i e maximum meltwater flux to the north atlantic western mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high pressure systems over the southwestern mediterranean in conjunction with cooling of the north atlantic

plio pleistocene evolution of the var deep sea fan off the french riviera abstract the var deep sea fan was deposited during the pliocene and quaternary seaward progradation of the var delta within a steep sided flat floored basin formed during the messinian salinity crisis the prominent palaeo var canyon was cut on the slope at the same time following the early pliocene transgression var sediments were initially trapped in the coastal ria formed by sea level incursion of the head of the messinian valley by middle pliocene time gilbert type deltas had prograded to the break of slope modern coastline allowing coarse sediment to reach the basin quaternary coastal uplift and sediment supply from the glaciated alps resulted in a supply of coarse sediment to the fan by the braided var river throughout the quaternary even during sea level highstands such as the present in the earliest pliocene hemipelagic clays accumulated while coarse sediment was trapped in the var ria through the rest of the pliocene a leveed fan valley extended southward from the var canyon which periodically switched locations through avulsion to the east at about the beginning of the quaternary this eastward spillover channel became the main distributary and re occupation of the older south trending channels was blocked by rapid levee progradation and aggradation of mud waves by overbanking of turbidity flows on the var sedimentary ridge during the quaternary channel shifting to the north occurred the quaternary var fan has an unusually steep concave longitudinal profile compared with most passive margin fans the laurentian fan has a similar profile to the var both have a high levee and a gravel and pebble floored fan valley that is essentially a bypass zone compared with the aggradational channel levee systems with lower levees in most passive margin fans this is a consequence of the constant supply of coarse sand gravel and pebbles to the fan even during highstands of sea level the erosive capability of this coarse sediment in ignitive turbidity currents resulted in flushing out of the upper and middle fan valley system thick muddy turbidity currents probably resulting from slumping caused by canyon incision produced the prominent mud waves on the levee the concave longitudinal profile led to rapid sediment deposition at critical points in the valley system as a result of turbidity flow expansion this in turn promoted the development of a left hook in the valley system