orogen parallel deformation of the himalayan midcrust insights from structural and magnetic fabric analyses of the greater himalayan sequence annapurna dhaulagiri himalaya central nepal the metamorphic core of the himalaya greater himalayan sequence ghs in the annapurna dhaulagiri region central nepal recorded orogen parallel stretching during mid crustal evolution anisotropy of magnetic susceptibility ams and field based structural analyses suggest that mid crustal deformation of the amphibolite facies core of the ghs occurred under an oblate sub oblate strain regime with associated formation of low angle northward dipping foliation magnetic and mineral stretching lineations lying within this foliation from the top of the ghs record right lateral orogen parallel stretching we propose that oblate strain within a mid crustal flow accommodated oblique convergence between india and the arcuate orogenic front without need for strain partitioning in the upper crust oblate flattening may have also promoted orogen parallel melt migration and development of melt depleted regions between km3 scale leucogranite culminations at 50 100 km intervals along orogen strike following cessation of flow continued oblique convergence led to upper crustal strain partitioning between orogen perpendicular convergence on thrust faults and orogen parallel extension on normal and strike slip faults in the annapurna dhaulagiri himalaya orogen parallel stretching lineations are interpreted as a record of transition from mid crustal orogen perpendicular extrusion to upper crustal orogen parallel stretching our findings suggest that mid crustal flow and upper crustal extension could not be maintained simultaneously and support other studies from across the himalaya which propose an orogen wide transition from mid crustal orogen perpendicular extrusion to upper crustal orogen parallel extension during the mid miocene the 3d nature of oblate strain and orogen parallel stretching cannot be replicated by 2d numerical simulations of the himalayan orogen

equivalent roughness of alluvial bed the eguivalent roughness of a movable bed is considered relationships are given which can be used to determine the equivalent bed roughness from the bed material size and the bed form dimensions in the case of a plane bed the equivalent roughness is related to the d 9 0 of the bed material based on flume and field data the equivalent roughness may vary from 1 10 d 9 0 similar values were reported by other research workers in the case of bed forms the equivalent roughness is related to the average height and length of the bed forms both flume and field data were used to determine a functional relationship the proposed relationship yields values which are considerably smaller than other existing relationships

net sediment transport and morphological change in the swash zone of a high energy sandy beach from swash event to tidal cycle time scales abstract a field experiment was conducted on a high energy sandy beach truc vert france to examine swash zone processes and shoreline erosion accretion in response to changing wave and tide conditions beachface morphological changes were measured at the swash by swash timescale using an array of ultrasonic bed level sensors and at the tidal timescale through total station surveys hydrodynamic and sediment dynamic data were collected using arrays of pressure transducers electromagnetic current meters optical backscatter sensors and total load sediment traps data were collected for 16 consecutive days 33 tides over a spring neap spring tidal cycle with offshore significant wave heights of 1 4 m and periods of 5 12 s the swash motion was predominantly at infragravity wave frequencies over the measurement period the upper beach experienced phases of accretion erosion and stability trapped sediment loads for the uprush and backwash were predicted reasonably well by cross shore velocity skewness but the prediction of net transport over individual swash events by velocity based models was more problematic particularly lower in the swash zone where swash interactions were more prevalent net sediment fluxes over individual swash events often exceeded 100 kg per unit meter beach width and such rates were only one order of magnitude less than the net transport typically experienced across the high tide swash zone over complete tidal cycles upper beach erosion accretion at the tidal timescale was reasonably well predicted by the dean criterion based on offshore wave steepness and dimensionless fall velocity but the beach gradient also played a significant role in controlling the occurrence of erosion and accretion

the influence of beach porosity on wave uprush and backwash abstract packwood a r 1983 the influence of beach porosity on wave uprush and backwash coastal eng 7 29 40 a numerical model is described to calculate the influence of a porous bed on the run up of a bore on a gently sloping sandy beach it is shown that fine medium grade sands have very little effect in the run up phase significant differences between impermeable and porous bed solutions are found in the backwash which might explain certain sand erosion and deposition phenomena

sand transport processes and bed level changes induced by two alternating laboratory swash events abstract sand transport processes and net transport rates are studied in a large scale laboratory swash zone bichromatic waves with a phase modulation were generated producing two continuously alternating swash events that have similar offshore wave statistics but which differ in terms of wave swash interactions measured sand suspension and sheet flow dynamics show strong temporal and spatial variability related to variations in flow velocity and locations of wave capture and wave backwash interactions suspended and sheet flow layer transport rates in the lower swash zone are generally of same magnitude but sheet flow exceeds the suspended load transport by up to a factor four during the early uprush the bed level near the inner surf zone is relatively steady during a swash cycle but changes of o cm s are measured near the mid swash zone where wave swash interactions lead to strongly non uniform flows the two alternating swash events produce a dynamic equilibrium with bed level changes up to a few mm induced by single swash events but with net morphodynamic change over multiple events that is two orders of magnitude lower most of the intra swash and the single event averaged bed level changes in the swash zone are caused by a redistribution of sediment within the swash the transport of sediment across the surf swash boundary is minor at intra swash time scale but becomes increasingly significant at swash averaged time scales or longer i e averaged over multiple swash events

the evolution of pleistocene climate a time series approach abstract in the later part of the pleistocene variations in global ice volume have been dominated by an approximate 100 000 year cycle analysis of 2 myr long oxygen isotope record from an equatorial pacific core indicates that this is true only for the last 900 000 years prior to this time the amplitude of the 100 000 year cycle is much reduced as is the variance of all oscillations with periods greater than 60 000 years based on results of time series analysis of this 2 myr long record the pleistocene glacial cycles can be divided into three sections 1 the late pleistocene 0 900 kyr b p where the variations in the isotope record are dominated by the 100 000 year cycle 2 the middle pleistocene 900 1450 kyr b p in which low frequency components are not as important as in the later period of the pleistocene and 3 the early pleistocene late pliocene 1450 2000 kyr b p where general reductions of importance at all frequencies is seen as compared to the later intervals recent modeling efforts which describe variations in global ice volume show that the dominant low frequency component observed in the late pleistocene can result from different time constants for the rate of glacial growth and decay in response to variations in the earth s orbital parameters it is hypothesized that during the early pleistocene the rate of growth and decay of glaciers were more similar and that continental erosion by successive glacial advances lowered the land surface in areas of ice cap formation to below sea level when the ice caps became marine based more rapid decay of the ice became possible

high resolution x ray computed microtomography a holistic approach to metamorphic fabric analyses an intrinsic limitation of studying microstructures in thin section is that their spatial three dimensional 3 d distribution shape and orientation have to be inferred by combining 2 d data from different sections this procedure always involves some degree of interpretation that in some cases can be ambiguous recent advances in high resolution x ray computed microtomography have made possible the direct imaging in 3 d of volumes of rock to centimeter scale this rapidly evolving technology is nondestructive and provides a holistic approach of microstructural analysis that eliminates interpretative procedures associated with 2 d methods spatial images can be generated through any part of the rock sample and used as virtual petrographic sections our application of this technique to an oriented drill core sample from the classic orijarvi metamorphic region of southern finland reveals a number of in situ 3 d aspects including 1 the spatial distribution and shape of andalusite porphyroblasts 2 the geometry of a matrix foliation anastomosing around the porphyroblasts 3 a millimeter scale compositional layering that controlled the oscillation of porphyroblasts and sulfide mineralization and 4 distinct inclusion trail patterns characterizing porphyroblast core versus rim zones the combined data indicate that the steeply dipping bedding subparallel foliation that characterizes the orijarvi area formed by bulk north south crustal shortening and associated vertical stretching

beach face evolution in the swash zone we investigate swash on an erodible beach using the one dimensional shallow water equations fully coupled to a bed evolution exner equation in particular the dam break bore collapse initial condition of shen meyer j fluid mech vol 16 1963 pp 113 125 and peregrine williams j fluid mech vol 440 2001 pp 391 399 is investigated using a numerical model based on the method of characteristics a sediment transport formula cubic in velocity u au 3 is used here this belongs to a family of sediment transport formulae for which pritchard hogg coastal engng vol 52 2005 pp 1 23 showed that net sediment transport under the shen meyer 1963 bore collapse is offshore throughout the swash zone when a non erodible bed is considered it is found that full coupling with the beach although still resulting in the net offshore transport of sediment throughout the swash zone leads to a large reduction in the net offshore transport of sediment from the beach face this is particularly true for the upper third of the swash zone moreover in contradistinction to swash flows over non erodible beds flows over erodible beaches are unique to the bed mobility and porosity under consideration this has very important implications for run up predictions the conclusion is that it is essential to consider full coupling of water and bed motions i e full morphodynamics in order to understand and predict sediment transport in the swash regardless of other physical effects e g turbulence infiltration pre suspended sediment etc

swash zone sediment fluxes field observations abstract this paper describes newly obtained high frequency observations of beach face morphological change over numerous tidal cycles on a macrotidal sandy beach made using a large array of ultrasonic altimeters these measurements enable the net cross shore sediment fluxes associated with many thousands of individual swash events to be quantified it is revealed that regardless of the direction of net morphological change on a tidal time scale measured net fluxes per event are essentially normally distributed with nearly equal numbers of onshore and offshore directed events the majority of swash events cause net cross shore sediment fluxes smaller than 50 kg m 1 and the mean sediment flux per swash event is only o 1 kg m 1 leading to limited overall morphological change however much larger events which deposit or remove hundreds of kilograms of sand per meter width of beach occur at irregular intervals throughout the course of a tide it was found that swash swash interactions tend to increase the transport potential of a swash event and the majority of the swash events that cause these larger values of sediment flux include one or more interactions the majority of the larger sediment fluxes were therefore measured in the lower swash zone close to the surf swash boundary where swash swash interactions are most common despite the existence of individual swash events that can cause fluxes of sediment that are comparable to those observed on a tidal time scale frequent reversals in transport direction act to limit net transport such that the beach face volume remains in a state of dynamic equilibrium and does not rapidly erode or accrete

foliation development and refraction in metamorphic rocks reactivation of earlier foliations and decrenulation due to shifting patterns of deformation partitioning reactivation of early foliations accounts for much of the progressive strain at more advanced stages of deformation its role has generally been insufficiently emphasized because evidence is best preserved where por phyroblasts which contain inclusion trails are present reactivation occurs when progressive shearing operating in a synthetic anastomosing fashion parallel to the axial planes of folds changes to a combination of coarse and fine scale zones of progressive shearing some of which operate antithetically relative to the bulk shear on a fold limb reactivation of earlier foliations occurs in these latter zones reactivation decrenulates pre existing or just formed crenulations generating shearing along the decrenulated or rotated pre existing foliation planes partitioning of deformation within these foliation planes such that phyl losilicates and or graphite take up progressive shearing strain and other minerals accom modate progressive shortening strain causes dissolution of these other minerals this results in concentration of the phyllosilicates in a simi lar but more penetrative manner to the for mation of a differentiated crenulation cleavage except that the foliation can form or intensify on a fold limb at a considerable angle to the axial plane of synchronous macroscopic folds reactivation can generate bedding parallel schistosity in multideformed and meta morphosed terrains without associated folds heterogeneous reactivation of bedding gen erates rootless intrafolial folds with sigmoidal axial planes from formerly through going struc tures reactivation causes rotation or refrac tion of axial plane foliations forming in the same deformation event causing reactivation in those beds or zones in which an earlier foli ation has been reactivated and results in destruction of the originally axial plane foli ation at high strains reactivation also provides a simple explanation for the apparently wrong sense but normally observed rotation of gar net porphyroblasts whereby the external foli ation has undergone rotation due to antithetic shear on the reactivated foliation alter natively the rotation of the external foliation can be due to its reactivation in a subsequent deformation event porphyroblasts with inclusion trails com monly preserve evidence of reactivation of earl ier foliations and therefore can be used to ident ify the presence of a deformation that has not been recognized by normal geometric methods because of penetrative reactivation reac tivation often reverses the asymmetry between pre existing foliations and bedding on one limb of a later fold leading to problems in the geo metric analysis of an area when the location of early fold hinges is essential the stretching lineation in a reactivated foliation can be rad ically reoriented potentially causing major errors in determining movement directions in mylonitic schistosities in folded thrusts geometric relationships which result from reactivation of foliations around porphyroblasts can be used to aid determination of the timing of the growth of porphyroblasts relative to deformation events other aspects of reac tivation however can lead to complications in timing of porphyroblast growth if the presence of this phenomenon is not recognized for example d grown porphyroblasts may be dis solved against reactivated s and hence appear to have grown syn d

measurement of wave by wave bed levels in the swash zone abstract a technique is described to observe and quantify wave by wave bed level changes in the swash zone the ultrasonic instrument system is non contact with the beach face surface being measured and the sensors remain outside of the fluid flows causing sediment movement sensor resolution combined with the electronic noise inherent within a digital network data logging system results in a conservative measurement accuracy of 1 mm equating to a couple of sand grain diameters in height illustrative field results demonstrate the practical use of the instrumentation and a simple data pre processing method to separate swashes and intervening bed level events is discussed these example data reveal rather complex fluctuations of the bed observed over time periods of minutes to hours rather strikingly gross bed level changes per wave are revealed to be up to many orders of magnitude larger than the observed net rate of beach face evolution it is outlined how observations of successive bed level changes at multiple locations within a dense grid combined with a consideration of sediment continuity will now enable the total net sediment transported per uprush backwash to be quantified

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

advances in numerical modelling of swash zone dynamics we present a comprehensive and critical review of work on the numerical modelling of swash zone processes between 2005 and 2015 a wide range of numerical models has been employed for the study of this region and hence only phase resolving approaches i e depth averaged and depth resolving models are analyzed the current advances in the modelling of swash zone processes are illustrated by comparing different numerical models against laboratory experiments of a dam break driven swash event depth averaged and depth resolving models describe well the swash flow for both coarse sand and gravel impermeable beach cases depth averaged models provides a practical tool for engineering use whereas depth resolving models improve the flow description especially for the backwash phase with a significantly higher computational cost the evolution and magnitude of bed shear stresses predicted by all models is reasonable when compared with laboratory estimates based on the log law however differences between modelling approaches cannot be rigorously evaluated owing to the uncertainty in shear stress estimates while employing such approximation furthermore small scale processes such as turbulence evolution are investigated with depth resolving models finding differences between the two dimensional and three dimensional approaches numerical models allow us to investigate other processes such as beach morphology changes the evolution of the turbulence coherent structures and the infiltration exfiltration effects on the swash flow a discussion on the advantages and limitations of each model is presented the future of swash zone modelling depends on the increase of the computational power and more importantly on the improvement of the current capability to obtain intra wave measurements for model validation calibration and greater resolution of physical processes

numerical modelling of the flow and bed evolution of a single bore driven swash event on a coarse sand beach abstract this paper examines the numerical prediction of the sediment transport and bed evolution for a single swash event on a coarse sediment beach in these conditions bed load is the dominant mode of sediment transport laboratory experiments of a single bore driven swash event are simulated numerically using a fully coupled model that solves the system of non linear shallow water equations and the exner sediment conservation formula the analysis focuses on two aspects the optimal choice of parameters for the meyer peter and muller sediment transport formula and the model used for computing the shear stress the methods tested for the bed shear stress are the momentum integral method and the chezy formulation in which the friction factor is computed using two different formulae infiltration into the beach and its effects on the shear stress and sediment transport are also modelled results show that the basic meyer peter and muller sediment transport formula provides good results in the run up on the other hand the sediment transport in the early stage of the backwash is overestimated a reduction of the sediment mobility constant in the formula in the backwash marginally improves the results however the causes of the overestimation of the sediment transport at the early stage of the backwash is the overestimation of the shear stress while at later stages there are several contributions that are identified i e modelling of the sediment transport and infiltration it is also suggested that the meyer peter and muller sediment transport formula might not capture the complexity of the processes involved during the backwash the comparison of the methods for the estimate of the bed shear stress show that comparable results can be obtained using the momentum integral method and the chezy formulation with time and space varying friction factor the resulting bed evolution is also described in the predicted final profile deposition is found in the upper part of the beach and erosion in the lower part a bed step is formed just below the position of the initial shoreline this feature is determined by the onset of a hydraulic jump during the backwash

a succession of near orthogonal horizontal tectonic shortenings in the paleoproterozoic central lapland greenstone belt of fennoscandia constraints from the world class suurikuusikko gold deposit the relative and absolute timing of orogenic gold deposits in complex structural settings are active and challenging topics of research especially in precambrian greenstone belts the suurikuusikko gold deposit in central lapland greenstone belt is currently the largest primary gold producing deposit in europe located on a slight bend of the strike slip kiistala shear zone kisz gold is refractory and locked inside arsenopyrite and pyrite in this study different structural features were investigated along the kisz from the recently stripped etela pit which is the southern extension of the suurikuusikko ore body our data source ranges from aeromagnetic to high resolution aerial images x ray computed tomography scans of selected rock samples and regional geological and geophysical datasets the kisz has recorded five discrete deformation phases spanning between ca 1 92 and 1 76 ga the refractory gold at the suurikuusikko deposit formed during e w contraction related to the d1 thrusting phase this was followed by a n s shortening event d2 where most of the strain was taken up by the northern and southern thrusts tectonic vectors then switched from n s to ne sw and as a result dextral strike slip regime d3 commenced along the kisz this event exsolved invisible gold from the sulfides and remobilized it along with fractures a near orthogonal switch of the regional stress regime from ne sw to nw se flipped the kinematics of the kisz from dextral to sinistral d4 the last deformation phase d5 produced widespread veining under e w contraction and secured gold mineralization at the iso kuotko gold deposit within the kisz

kinematics of orogenic collapse in the variscan pyrenees deduced from microstructures in porphyroblastic rocks from the lys caillaouas massif in the pyrenees a phase of bulk vertical shortening d3 is indicated by a horizontal crenulation cleavage s3 which is developed in a pre existing schistosity s2 porphyroblasts of the lys caillaouas massif regionally preserve 1 1 the initial pre d3 orientation of s2 in the form of a vertical and e w trending preferred orientation of their inclusion trails 2 2 a vertical l2 stretching lineation defined by the elongation of the inclusions these data are consistent with n s compression and crustal thickening during d2 the angle between the inclusion trails s2 i and the external schistosity s2 e records the subsequent rotation of s2 from vertical to gently dipping orientations at higher crustal levels s2 remained steep suprastructure and little d3 deformation is evidenced with depth d3 deformation progressively intensifies and zones can be distinguished with opposite dip directions of s2 opposite apparent porphyroblast rotation senses and opposite f3 crenulation asymmetries these micro structures on a n s section through the lys caillaouas and the garonne dome massifs record a regional partitioning of bulk coaxial vertical shortening this deformation partitioning was probably controlled by a not exposed gneiss dome which behaved relatively rigid as compared to its metasedimentary cover in zones of non coaxial d3 deformation s2 was extended reactivated and forms the dominant schistosity where d3 was locally more coaxial s2 was shortened isoclinally crenulated and s3 forms the macroscopic cleavage the fact that d3 extension in the lys caillaouas massif immediately followed d2 compression and that similar extension is recorded in large parts of the variscan foldbelt suggests gravitational collapse of a thickened orogen this is consistent with the flattening type of d3 strain recognized in a number of pyrenean variscan massifs peak high t low p metamorphic conditions coincide with the onset of orogenic extension when very little crustal thinning could have been accomplished yet this suggests that heat induced strain softening within the orogen may have triggered its collapse

porphyroblast non rotation during crustal extension in the variscan lys caillaouas massif pyrenees abstract the dominant foliation s 2 in the variscan lys caillaouas massif central pyrenees france spain formed in a subvertical orientation during crustal thickening d 2 subsequent non coaxial crustal extension produced a subhorizontal crenulation cleavage s 3 whereby s 2 was folded and rotated andalusite staurolite cordierite and biotite porphyroblasts grew very early during this extension d 3 and included s 2 as straight curved and weakly crenulated inclusion trails these inclusion trails exhibit a strong subvertical preferred orientation which is independent of the local magnitude of d 3 strain the dip angle of the external main foliation s 2 or the aspect ratio and shape orientation of porphyroblasts this indicates that porphyroblasts did not rotate in the d 3 deformation field and hence preserve the orientation of s 2 at the time it was trapped in the porphyroblast relative to the bulk d 3 flow plane porphyroblasts could maintain a stable orientation in the d 3 flow due to complete accommodation of the bulk flow vorticity by heterogeneous shear strain the lack of vorticity of local volumes of zero shear strain such as porphyroblasts was balanced by concentration of shear strain in planar zones anastomosing around them it is likely that s 2 maintained a subhorizontal orientation throughout the d 3 crustal extension which would imply that porphyroblasts also remained stationary relative to the earth s surface during d 3 whereas s 2 in the deforming matrix experienced shear induced rotation a late brittle ductile folding event d 4 involving differential rigid block rotations dispersed the orientation of inclusion trails to some degree these late rotations could be corrected for by artificial unfolding of the f 4 folds

morphodynamical modelling of field scale swash events in the present work data for three single swash events are selected from those available for an accretive tide that occurred at le truc vert beach france during a measurement field campaign at that location these events are primarily chosen because of the different final bed change they produced namely variable accretion seaward erosion landward deposition and variable erosion along the swash zone these data are compared to results obtained from a state of the art numerical fully coupled 1d morphodynamical shallow water solver driven by measurements made of those events in the lower swash inner surf zone it is found that the hydrodynamics is reasonably well represented although the computed results exhibit reduced maximum inundations in comparison with the observed ones the model reproduces the correct order of magnitude of the morphodynamic change after each event and sometimes the pattern of erosion and deposition but this change is generally underestimated sensitivity analyses are conducted with respect to more uncertain physical parameters and assumed initial conditions they suggest that initial spatial distributions for velocity and pre suspended sediment concentration play a key role in the quantitative and qualitative prediction of the bed change

experimental study of bore driven swash hydrodynamics on impermeable rough slopes abstract a detailed experimental investigation of the hydrodynamics of large scale bore driven swash on impermeable rough beach slopes is described the experiments were carried out on 1 10 impermeable rough slopes with three different surface roughnesses based on 1 3 mm sand 5 4 mm gravel and 8 4 mm gravel the large scale discrete swash event was produced by the collapse of a dambreak generated bore on the beach simultaneous depths and velocities were measured using lif laser induced fluorescence and piv particle image velocimetry respectively yielding better resolution of the hydrodynamics than previous studies depth time series instantaneous velocity profiles depth averaged velocities instantaneous turbulent kinetic energy profiles depth averaged turbulent kinetic energy reynolds stress profiles and bed shear stresses are presented for five cross shore measurement locations in the swash the measurements resolve the backwash shoreline position and the late backwash period when depths are shallow and velocities are high the detailed data can be used to test and develop advanced numerical models for bore driven waves on rough slopes

a paleoclimate model of northern hemisphere ice sheets abstract a model for predicting the growth and decay of ice sheets based on the astronomical theory of climate change is presented the purpose of the study in part is to isolate the role of the ice sheet physics and earth response under varying ice load by simplifying to the extreme the role of the hydrosphere atmosphere ice sheet physics and the response of the lithosphere asthenosphere under the ice load are modeled explicitly insolation anomalies taken at a fixed latitude directly force latitudinal displacement of the snow line accumulation rate a and ablation rate a evaluated at mean sea level are specificed as external constants a a decrease linearly with ice sheet elevation rough tuning of the model to the general shape of the ice volume record of the last two major glacials determines the external constants model predictions of the ages of several events in the last major glaciation compare well with the radiological ages the six glacial terminatios i vi over the last 600 000 yr are identified and the predicted ages compare reasonably well with the 18 o record for two deep sea cores a direct comparison of model power spectra of ice volume as a function of period with spectra of the 18 o record shows apparent underprediction of power near 100 000 yr when a quantitative but heuristic method for taking into account the red noise spectrum evident in the geological records is used a much more favorable comparison is possible the model prediction lends support to the hypothesis that the nonlinearity of the ice sheet physics is responsible for the 100 000 yr periodicity in the geological record of the late pleistocene

on beach cusp formation a system of shallow water equations and a bed evolution equation are used to examine the evolution of perturbations on an erodible initially plane beach subject to normal wave incidence both a permeable under darcy s law and an impermeable beach are considered it is found that alongshore periodic morphological features reminiscent of swash beach cusps form after a number of incident wave periods on both beaches on the permeable impermeable beach these patterns are accretional erosional in both cases flow is horn divergent spacings of the cusps are consistent with observations and are close to those provided by a standing synchronous linear edge wave an analysis of the processes leading to bed change is presented two physical mechanisms are identified concentration gradient and flow divergence which are dominant in the lower and upper swash respectively and their difference over a wave cycle leads to erosion or deposition on an impermeable beach infiltration enters this balance in the upper swash a bed wave of elevation is shown to advance up the beach at the tip of the uprush with a smaller wave of depression on the backwash it is found that cusp horns can grow by a positive feedback mechanism stemming from decreased increased backwash on positive negative bed perturbations

computer experiments to investigate complex fibre patterns in natural antitaxial strain fringes antitaxial non deforming strain fringes from lourdes france show complex quartz calcite and chlorite fibre patterns that grew around pyrite in a slate during non coaxial progressive deformation development of these fringes was modelled using a computer program fringe growth 2 0 which can simulate incremental growth of crystal fibres around core objects of variable shape it uses object centre paths as input which are obtained from fibre patterns in thin section the numerical experiments produced fibre patterns that show complex intergrowth of displacement controlled face controlled and intermediate fibres similar to those in the natural examples the direction of displacement controlled growth is only dependent on the relative movement between core object and fringe so that core object rotation with respect to the fringe influences the fibre patterns and produces characteristic asymmetric fibre curvature object centre paths should be used for kinematic analysis of strain fringes instead of single fibres since these paths represent the fringe as a whole the length along the path can be interpreted in terms of finite strain and path curvature in terms of rigid body rotation of fringes with respect to an external reference frame

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

the morphodynamics of a swash event on an erodible beach a high accuracy numerical solution coupling one dimensional shallow water and bed evolution equations with for the first time a suspended sediment advection equation thereby including bed and or suspended load is used to examine two swash events on an initially plane erodible beach the event of peregrine williams j fluid mech vol 440 2001 pp 391 399 and that of a solitary wave approaching the beach equations are solved by the method of characteristics and the numerical model is verified full coupling of suspended load to beach change for peregrine williams j fluid mech vol 440 2001 pp 391 399 yields only slightly altered swash flows depending on beach mobility and sediment response time a series of similar final beach change patterns results for different beach mobilities suspended and bed load transport have distinct morphodynamical signatures for the solitary wave a backwash bore is created hibberd peregrine j fluid mech vol 95 1979 pp 323 345 this morphodynamical bore propagates offshore initially and leads to the creation of a beach bed step larson sunamura j sedimentary petrology vol 63 1993 pp 495 500 primarily due to bed load transport its height is directly related to bed load mobility and also depends strongly on the bed friction coefficient the shock dynamics of this bed step is explained and illustrated bed and suspended load mobilities are quantified using field data and an attempt is made to relate predictions to measurements of single swash events on a natural beach average predicted bed change magnitudes across the swash are of the order of 2 mm with maximum bed changes of up to approximately 10 cm at the bed step

numerical model of swash motion and air entrapment within coarse grained beaches abstract the paper presents a numerical model for bore driven swash on permeable coarse grained beaches the surface flow module is modelled using the non linear shallow water equations nlswes solved using the godunov based finite volume ader scheme which is suitable for handling steep bores as well as large source terms in the nlswes the subsurface flow comprises i infiltration and exfiltration modelled as vertical piston like flow ii horizontal pore air movement within the unsaturated region of the beach iii the horizontal groundwater flow model predictions of the surface and subsurface flow are in good agreement with measurements from large scale laboratory experiments for swash on permeable immobile beaches in these simulations air velocity was sufficiently small to justify using darcy s resistance law for the air flow whereas the quadratic forchheimer law had to be used for the infiltration and groundwater flow the validated numerical model provides insight into the surface subsurface water exchange for bore driven swash on coarse grained beaches the impact of air entrapped between the wetting front and the groundwater level on the water exchange is examined in particular

development of antitaxial strain fringes during non coaxial deformation an experimental study strain fringes were modelled experimentally around wooden objects in a simple shear box containing polydimethylsiloxane pdms the fringes were made of paraffin wax that was periodically poured into dilated sites next to the core object and left to crystallise in the experiments fringes and core object rotated at similar decreasing rotation rates relative to extensional incremental stretching axes isa of flow and rotated relative to each other by small amounts fringes did not necessarily open parallel to isa due to interactions between fringes and core object therefore neither displacement controlled fibres nor object centre paths can be expected to record the exact orientation of the extensional isa but only give estimates existing methods to calculate finite strain were applied to the experimental fringes these methods generally underestimate the actual finite shear strain this study illustrates that different final fringe shapes can develop in the same shear zone depending on core object shape and its initial orientation with respect to the shear zone boundary a classification of final fringe shapes is presented based on the initial orientation of elongate core objects

stress and displacement fields in the outer wedge induced by megathrust earthquakes we model plate boundary slip at the outer oceanward segment of the megathrust wedge as slip at the base of a two dimensional elastic wedge subject to gravity force with a sloping seafloor at the top and drag at the bottom from a rigid plate in frictional contact the stress and displacement fields in the wedge are given analytically as functions of basal frictional coefficient e unlike either conventional dislocation models constant slip or crack models constant stress drop our wedge model constant e drop does not show a stress singularity at the updip toe of the plate boundary the slip increases but the stress drop decreases updip along the fault toward the trench axis there is a minimum stress difference state in the wedge when e is varied by referring to this state e ec the stress state is separated into a horizontally tensile regime e ec slip associated with a e drop in the range e ec occurs toward increasing horizontal tension and shear energy such earthquakes include tsunami earthquakes occurring in the outer segment and the 2011 great tohoku oki earthquake which involved both the outer and inner segments with much larger slip in the outer segment these earthquakes are characterized by an almost complete drop of basal stress which brings the wedge into the maximum tensile state leading to the rare occurrence of thrust aftershocks at the base of the wedge and frequent occurrence of normal fault aftershocks within the wedge

on the transport of suspended sediment by a swash event on a plane beach we develop solutions for the transport of suspended sediment by a single swash event following the collapse of a bore on a plane beach and we investigate the morphodynamical role that such transport may play although the intrinsic asymmetry between uprush and backwash velocities tends to encourage the export of sediment we find that swash events may be effective in distributing across the swash zone much or all of the sediment mobilised by bore collapse additionally settling lag effects may promote a weak onshore movement of sediment we quantify both effects in terms of the properties of the sediment and of the swash event and comment on the relationship between our findings and recent field studies of swash zone sediment transport

unified view of sediment transport by currents and waves i initiation of motion bed roughness and bed load transport attention is given to the properties of sediment beds over the full range of conditions silts to gravel in particular the effect of fine silt on the bed composition and on initiation of motion critical conditions is discussed high quality bed load transport data sets are identified and analyzed showing that the bed load transport in the sand range is related to velocity to power 2 5 the bed load transport is not much affected by particle size the prediction of bed roughness is addressed and the prediction of bed load transport in steady river flow is extended to coastal flow applying an intrawave approach simplified bed load transport formulas are presented which can be used to obtain a quick estimate of bed load transport in river and coastal flows it is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions the proposed model is fully predictive in the sense that only the basic hydrodynamic parameters dep

laboratory and numerical study of dambreak generated swash on impermeable slopes new laboratory experiments have produced detailed measurements of hydrodynamics within swash generated by bore collapse on a steep beach the experiments are based on a dambreak rig producing a highly repeatable large scale swash event enabling detailed measurements of depths and velocities at a number of locations across the swash zone experiments were conducted on two beaches differentiated by roughness results are presented for uprush shoreline motion flow depths depth averaged velocity velocity profiles and turbulence intensity estimates of the time and spatially varying bed shear stress are obtained via log law fitting to the velocity profiles and are compared with the shear plate measurements of barnes et al 2009 for similar experimental conditions experimental results are compared with model predictions based on a nlswe model with momentum loss parameterised using the simple quadratic stress law in terms of the depth averaged velocity predicted and measured flow depths and depth averaged velocities agree reasonably well for much of the swash period but agreement is not good at the time of bore arrival and towards the end of the backwash the parameterisation of total momentum loss via the quadratic stress law cannot adequately model the swash bed shear stress at these critical times

probing the prodigious strain fringes from lourdes abstract we investigate the kinematics of classic sigmoidal strain fringes from lourdes france and review previous genetic models strain methods and strain rates for these microstructures displacement controlled quartz and calcite fibers within the fringes yield an average strain of 195 with the technique of ramsay and huber 1983 this agrees well with strains measured from boudinaged pyrite layers and calcite veins in the same rocks but conflicts with ca 675 strain in previous analogue models for the studied strain fringes produced by progressive simple shear we show that the detailed geometry and orientation of fiber patterns are insufficiently explained by simple shear but imply two successive differently oriented strain fields although all strain fringes have the same overall asymmetry considerable morphological variation resulted from different amounts of rotation of pyrite grains and fringes minor rotation led to sharply kinked fibers that record a ca 70 rotation of the kinematic frame larger up to 145 rotations accommodated by antithetic sliding on pyrite fringe contacts produced more strongly and smoothly curved fibers combined with published rb sr ages for the studied microstructures our new strain data indicate an average strain rate of 1 41 10 15 s 1 during ca 37 myr continuous growth

the pyrite type strain fringes from lourdes france indicators of alpine thrust kinematics in the pyrenees a new method is developed to reconstruct polyphase deformation histories from pyrite grains with displacement controlled fibrous strain fringes it decomposes the relative displacement between a pyrite grain and a fringe into incremental rotations and pull apart directions application to a classic specimen from lourdes france shows that the rotations determine the fibre curvature sense and strongly depend on local strain parameters as well as the initial orientation and shape of pyrite grains in contrast pull apart directions appear to be relatively constant and straight although curved pull apart trajectories were expected from the heterogeneous non coaxial deformation in the matrix the discrepancy is due to the localization of shear strain components around pyrite fringe complexes the complexes themselves represent ellipsoidal domains of relatively coaxial strain that parallel a regional crenulation cleavage even in zones lacking this cleavage due to stretching and shearing of a pre existing foliation s1 thus strain fringes consistently record bulk shortening orientations regardless of local variations in strain parameters and microstructural development the analysed pyrite fringe complexes from lourdes were previously considered as classic shear sense indicators but yield hook shaped pull apart trajectories in the new method this indicates two deformation events that can be related to a sub horizontal s2 and steep regional crenulation cleavage s3 the recorded polyphase deformation history is tentatively interpreted in terms of a change from gravitational spreading to a compressive emplacement of a thrust sheet in the north pyrenean foreland

isotopic dating of strain fringe increments duration and rates of deformation in shear zones the time scales over which deformation in the earth9s crust remains localized in shear zones are poorly known as are the associated strain rates we have determined the longevity and rates of deformation using rubidium strontium rb sr microsampling dating of increments of fibrous strain fringes from a pyrenean shear zone the fibers grew quasi continuously through a protracted deformation history between 87 and 50 million years ago over a period comparable to that of an orogeny during a short interval between 66 and 62 million years a rise in strain rate from 1 1 10 15 to 7 7 10 15 seconds 1 occurred this acceleration correlates with an abrupt change in fiber growth direction and a stress field inversion from gravitational collapse to renewed horizontal crustal shortening

non linear shallow water modelling of bore driven swash description of the bottom boundary layer abstract the paper presents a simple approach to estimate the bottom shear stress in the swash zone by coupling the non linear shallow water equations with the momentum integral equation for the bottom boundary layer the approach allows not only the computation of the frictional dissipation term in the equations but also to have an insight into the flow structure in the water column during a swash event the numerical results have been compared with a new set of experiments involving a single dam break generated swash event three different grain sizes ranging from coarse sand to gravel have been tested in the laboratory a sensitivity analysis on the only calibration parameter of the model the bed roughness is presented and its optimal value is chosen the numerically predicted free surface depth averaged velocity and velocity profiles have been compared with the measured ones results are very good in the run up stage where also the bottom shear stress is well modelled in the backwash the frictional energy dissipation is better modelled for the gravel beach than for the coarse sand one results show that the simple model accurately predicts the flow parameters during the swash event also the velocity profiles are reasonably well predicted especially during the run up

thermoluminescence dating of coarse grain quartz from the malan loess at zhaitang section china thermoluminescence tl ages were obtained for five loess samples taken from the zhaitang section near beijing china using the coarse grain quartz technique the paleodose values have been determined by the method of total sample bleaching and regeneration of the tl growth curve the method appears to be suitable for the age determination of loess samples up to about 150 000 yr where the annual dose rate values are of the order 3 4 mgy yr this limit is a function of the total accumulated dose the ages are in good agreement with those obtained by a fine grain tl technique and are consistent with geological and geomagnetostratigraphic evidence

shear stress and sediment transport calculations for swash zone modelling it is shown that the observed difference in sediment transporting efficiency by the swash uprush compared with the downrush could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush the bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead phi tau of the bed shear stress compared with the free stream velocity at the peak frequency with this approach the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula without the need for different uprush and downrush coefficients while the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre suspended sediment in the uprush nevertheless the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre suspended sediment to the onshore sediment transport in swash zones c 2002 published by elsevier science b v

the internal inclusion trail geometries preserved within a first phase of porphyroblast growth the inclusion trail geometry within a first phase of porphyroblast growth can differ significantly from that preserved by further enlargement because the porphyroblast forms a rigid mass up against which the rock preferentially strains during ensuing events the geometry of the first overgrown inclusion trails is affected by their primary orientation including any pre existing curvature combined with any heterogeneous rotation of this foliation about the developing stretching lineation this can impact the apparent timing of foliation intersection inflection axes preserved within porphyroblasts fias that nucleated during the development of a sub horizontal foliation but is readily resolved 3 d computer analysis of sigmoidal inclusion trails reveals that the asymmetry method for fia determinations is unaffected by the cut location relative to the porphyroblast core significantly perfect spiral inclusion trail geometries can be produced from a sigmoidal shape in cuts up 30 away from the fia therefore since fias in most porphyroblasts bear no relation to matrix structures there is a 17 chance that thin sections cut relative to the foliation lie within 30 of a fia and could contain such an apparent spiral fias maintain consistent trends for the first phase of porphyroblast growth accompanying horizontal bulk shortening but may vary in plunge fias have sub horizontal plunges for porphyroblasts nucleating during gravitational collapse but may vary in trend for all periods of porphyroblast regrowth the data available indicates that fias remain consistently trending and sub horizontal until the relative direction of plate motion causing orogenesis changes

a numerical study of swash flows generated by bores abstract article history received 10 october 2007received in revised form 15 march 2008accepted 4 april 2008available online 4 june 2008keywords swash zonetsunami runupdam breakborenon linear shallow water equationsreynolds averaged navier stokes equationnon linear k model the dynamic processes of bore propagation over a uniform slope are studied numerically using a 2 dreynolds averaged navier stokes rans solver coupled to a non linear k turbulence closure and avolume of uid vof method the dam break mechanism is used to generate bores in a constant depthregion present numerical results for the ensemble averaged ow eld are compared with existingexperimental data as well as theoretical and numerical results based on non linear shallow water nsw equations reasonable agreement between the present numerical solutions and experimental data isobserved using the numerical results small scale bore behaviors and ow features such as the bore collapseprocess near the still water shoreline the mini collapse during the runup phase and the back wash bore inthe down rush phase are described in the case of a strong bore the evolution of the averaged turbulencekinetic energy tke over the swash zone consists of two phases in the region near the still water shoreline the production and the dissipation of tke are roughly in balance in the region farther landwards of the still water shoreline the tke decay rate is very close to that of homogeneous grid turbulence on the other hand in the case of a weak bore the bore collapse generated turbulence is con ned near the bottom boundarylayer and the tke decays at a much slower rate 2008 elsevier b v all rights reserved

incrementally developed slickenfibers geological record of repeating low stress drop seismic events an accretionary melange of triassic age ocean floor sediments exposed in the chrystalls beach complex south island new zealand comprises competent sandstone and chert phacoids set in a cleaved mudstone matrix deformed in a continuous discontinuous style at subgreenschist conditions deformation structures include a pervasive anastomosing fault fracture mesh of multiple shearing surfaces subparallel to cleavage coated with incrementally developed quartz calcite slickenfibers microstructural observations reveal slickenfiber growth by crack seal shear slip increments of 10 100 m with incremental slip transfer of the same order accommodated by opening of extension fractures that link en echelon slip surfaces individual slip surfaces can be traced for meters to tens of meters so that the ratio of average slip u to potential rupture length l predominantly lies within the range 10 6 u l 10 5 characteristic of microearthquakes obeying constant stress drop scaling with a low stress drop 30 kpa typical of low frequency earthquakes the host rock assemblage metamorphic environment inference of near lithostatic fluid overpressures low stress drop and mixed continuous discontinuous shearing resemble conditions and characteristics of low frequency earthquakes as identified within the seismic signals recorded during episodic tremor and slow slip events at the downdip end of the seismogenic subduction thrust interface and within accretionary prisms

thermoluminescence dating of periods of loess deposition and soil formation in normandy the least incomplete records of pleistocene climate change come from the study of deep sea sediments in which the stratigraphic record of oxygen isotope variations reflecting terrestrial ice volume is the primary correlation medium on continents the available record is far less complete because many of the characteristics of glaciation are erosional rather than depositional the areas of loess deposition may provide the best deposits in which to develop relatively complete regional stratigraphies that may be compared with the deep sea record1 2 in this study we use thermoluminescence tl dating of loess and of soil developed on loess to test this model we have confined ourselves to the last complete glacial cycle within which the reproducibility of the age determinations is similar to the time resolution of most deep sea core records

strain fringes and strain shadows at kamoa drc implications for copper mineralisation abstract the formation of strain shadows and strain fringes is described from diamictite and siltstone of the grand conglomerat unit nguba group at the kamoa copper deposit located within the drc at the western end of the central african copperbelt cacb fringes reveal a straight orientation of fibres during a coaxial deformation this supports the interpretation of a single phase of deformation during fringe growth within the deposit area the non deformed distal part of fringes and the straight orientation of fibres demonstrate the simple geometry of strain fringes quartz grains within strain fringes and strain shadows have generally straight or smoothly curved boundaries and lack undulose extinction in strain fringes muscovite and chlorite are generally observed on quartz grains where they define a foliation these characteristics suggest a static recrystallisation that developed under relatively high temperature and wet conditions a nw crustal shortening during the kolwezian deformation event of the lufilian orogeny is believed to be responsible for the coeval development of foliation strain shadows and strain fringes a syn orogenic origin of the copper sulphides during the lufilian orogeny is proposed