phosphoran olivine overgrowths implications for multiple impacts to the main group pallasite parent body phosphoran olivine 1 7 wt p2o5 is a metastable phase known from fewer than a dozen meteoritic or terrestrial occurrences we have thoroughly examined phosphoran olivine in the springwater pallasite to characterize its distribution textural relationships and geochemistry phosphoran olivine is abundant in springwater as randomly distributed millimeter scale partial overgrowths on the p free olivine crystals geochemical analyses support the substitution mechanism of p into the tetrahedral si site with octahedral site vacancies for charge balance observed trace element variations on the other hand are not related to p substitution element mapping reveals fine scale oscillatory p zoning in unusual serrate patterns indicating rapid crystal nucleation from a melt as proposed by boesenberg and hewins 2010 and a subsequently variable rate of crystallization the timing of phosphoran olivine formation in springwater is constrained to after the period of macroscopic olivine rounding but before the cooling of the metal matrix because the phosphoran overgrowths overprint specific host grain boundary modifications we suggest that the episode of extremely rapid cooling necessary to crystallize and preserve this rare phase may have been triggered by an additional impact to the parent body

the neogene to recent rallier du baty nested ring complex kerguelen archipelago taaf indian ocean stratigraphy revisited implications for cauldron subsidence mechanisms 1 ups cnrs fre 2566 orsayterre department des sciences de la terre universite de paris sud f 91405 orsay cedex france bbonin geol u psud fr 2 cnrs umr 6524 magmas et volcans department de geologie petrologie geochimie universite jean monnet f 42023 saint etienne cedex 2 france 3 cnrs ep 125 department des sciences de la terre universite de nice sophia antipolis f 06108 nice cedex 2 france 4 department of geology university college dublin belfield dublin 4 eire 5 gemoc macquarie university sydney australia

validation and verification of a numerical model for tsunami propagation and runup a robust numerical model to simulate propagation and runup of tsunami waves in the framework of non linear shallow water theory is developed the numerical code adopts a staggered leapfrog finite difference scheme to solve the shallow water equations formulated for depth averaged water fluxes in spherical coordinates a temporal position of the shoreline is calculated using a free surface moving boundary algorithm for large scale problems the developed algorithm is efficiently parallelized employing a domain decomposition technique the developed numerical model is benchmarked in an exhaustive series of tests suggested by noaa we conducted analytical and laboratory benchmarking for the cases of solitary wave runup on simple beaches runup of a solitary wave on a conically shaped island and the runup in the monai valley okushiri island japan during the 1993 hokkaido nansei oki tsunami in all conducted tests the calculated numerical solution is within an accuracy recommended by noaa standards we summarize results of numerical benchmarking of the model its strengths and limits with regards to reproduction of fundamental features of coastal inundation and also illustrate some possible improvements

on the role of shoreline boundary conditions in wave overtopping modelling with non linear shallow water equations abstract the note extends and completes the analysis carried out by briganti and dodd briganti r dodd n 2009 shoreline motion in nonlinear shallow water coastal models coastal eng 56 5 6 doi 101016 j coastaleng 2008 10 008 495 505 on the performance of a state of the art non linear shallow water equations solver in common coastal engineering applications the case of bore generated overtopping of a truncated plane beach is considered and the performance of the model is assessed by comparing with the peregrine and williams peregrine d williams s m 2001 swash overtopping a truncated beach j fluid mech 440 391 399 analytical solution in particular the influence of shoreline boundary conditions is investigated by considering the two best performing approaches discussed in briganti and dodd briganti r dodd n 2009 shoreline motion in nonlinear shallow water coastal models coastal eng 56 5 6 doi 101016 j coastaleng 2008 10 008 495 505 different distances of the edge of the beach from the bore collapse point are tested for larger distances the accuracy of the overtopping modelling decreases as a consequence of the error in modelling the tip of the swash lens and consequently the run up a sensitivity analysis using the numerical resolution is carried out this reveals that the approach in which cells shallower than a prescribed threshold are drained and wave propagation speeds for wet dry riemann problem are used at the interface between a wet and a dry cell referred as option 2ea in briganti r dodd n 2009 shoreline motion in nonlinear shallow water coastal models coastal eng 56 5 6 doi 101016 j coastaleng 2008 10 008 495 505 performs consistently better than the other

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

aligned olivine in the springwater pallasite the mechanism by which olivine grains became embedded within iron nickel alloy in pallasite meteorites continues to be a matter of scientific debate geochemical and textural observations have failed to fully elucidate the origin and history of the olivine crystals however little research attention has been devoted to their crystallographic orientations within the metal matrix using electron backscatter diffraction we have collected crystallographic orientation data for 296 crystals within 65 cm2 sample surface from springwater though no global crystallographic preferred orientation exists very low misorientations are observed among 100 axes of olivine crystals within specific texturally defined domains combined with a thorough characterization of large scale springwater textures the definitively nonrandom spatial distribution of olivine orientations provides clues regarding the nature of the olivine s initial formation environment as well as the sequence of events subsequent to metal incorporation

overtopping a truncated planar beach run up on a truncated impermeable beach is analysed theoretically and experimentally to find the volume of fluid associated with a single wave event that flows over the end of the beach the theoretical calculations investigate the motion using the shallow water equations and the fluid is allowed to flow freely over the end of the beach two models of wave events are considered dam break initial conditions in which fluid collapses from rest to run up and overtop the beach and a waveform that models swash associated with the collapse of a long solitary bore the calculations are made using quasi analytical techniques following the hodograph transformation of the governing equations they yield predictions for the volume of fluid per unit width that overtops the beach primarily as a function of the dimensionless length of the beach these predictions are often far in excess of previous theoretical calculations new experimental results are also reported in which the overtopping volumes due to flows initiated from dam break conditions are studied for a range of reservoir lengths and heights and for a range of lengths and inclinations of the beach without the need for any empirically fitted parameters good agreement is found between the experimental measurements and the theoretical predictions in regimes for which the effects of drag are negligible

direct bed shear measurements under loose bed swash flows shear plate measurements of bed shear stress under fixed and loose bed swash uprush flows are presented and contrasted a shear plate previously developed for fixed bed flows was modified and tested for coarse and fine grain loose beds transient flows were generated by a dam break flow over initially dry horizontal and sloping beds with flows upslope analogous to swash uprush flows on beaches performance of the shear plate varied with grain size for the coarse grained loose beds only the peak shear stress at the leading edge of the swash flow was consistently obtained for fine grained loose beds the shear stress was reliably obtained over the whole uprush swash cycle data were obtained for varying thickness of loose bed material commencing with a single grain layer which correspond to partially starved bed conditions the direct measurements clearly indicate that the bed shear stress comprises of a fluid shear stress component and a grain shear stress component the grain shear stress increases linearly with sediment load and is significantly larger for the coarse loose grain bed tests due to the much larger normal stress compared to that for fine grain loose bed tests with the same number of grain layers the data show a high degree of consistency with the classical theory of bagnold 1956 and the derived coefficient of dynamic internal friction is similar to that observed by hanes and inman 1985

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

energy grade line analysis of tsunami run up on the sendai plain after the 2011 tohoku earthquake abstract energy grade line analysis egla of tsunami run up has been proposed as a simple tool to predict inundation heights and tsunami loads a large database of more than 500 inundation measurements collected on the sendai plain on the east coast of japan after the tohoku earthquake of 2011 provided the writers the opportunity to evaluate the accuracy of the general egla method and to make adjustments to fit the model to the sendai plain refinements to the egla model included a correction for the influence of large linear topographic obstructions on tsunami flows in order to achieve better agreement with measured inundation heights the study illustrates that inundation height predictions are sensitive to the choice of froude number parameter and land use roughness coefficients an important outcome of this study is a site specific tool for probabilistic prediction of inundation heights over the sendai plain that is of value for tsunami counter measure planning including design of tsunami resistant structures

assessment of runup predictions by empirical models on non truncated beaches on the south east australian coast abstract this paper assesses the accuracy of 11 existing runup models against field data collected under moderate wave conditions from 11 non truncated beaches in new south wales and queensland australia beach types spanned the full range of intermediate beach types from low tide terrace to longshore bar and trough model predictions for both the 2 runup exceedance r2 and maximum runup rmax were highly variable between models with predictions shown to vary by a factor of 1 5 for the same incident wave conditions no single model provided the best predictions on all beaches in the dataset overall model root mean square errors are of the order of 25 of the r2 value models for r2 derived from field data were shown to be more accurate for predicting runup in the field than those developed from laboratory data which overestimate the field data significantly the most accurate existing models for predicting r2 were those developed by holman 12 and vousdoukas et al 40 with mean rmse errors of 0 30 m or 25 a new model of models for r2 was developed from a best fit to the predictions from six existing field and one large scale laboratory r2 data derived models it uses the hunt 17 scaling parameter tan h o l o and incorporates a setup parameterisation this model is shown to be as accurate as the holman and vousdoukas et al models across all tidal stages it also yielded the smallest maximum error across the dataset the most accurate predictions for rmax were given by hunt 17 but this tended to under predict the observed maximum runup obtained for 15 min records mase s 22 model has larger errors but yielded more conservative estimates greater observed values of rmax are expected with increased record length leading to greater differences in predicted values given the large variation in predictions across all models however it is clear that predictions by uncalibrated runup models on a given beach may be prone to significant error and this should be considered when using such models for coastal management purposes it should be noted that in extreme events which are lacking in the dataset runup may be truncated by beach scarps cliffs and dunes or may overtop and as a result the probability density functions will have different tail shapes the uncertainty already present in current models is likely to increase in such conditions

morphodynamic evolution of a coastal lagoon entrance during swash overwash new field observations of beach berm growth resulting in the sub aerial closure of an intermittently closed and open lake or lagoon are presented these perched estuarine systems frequently exhibit ephemeral entrances that respond to process forcing almost instantaneously on a geomorphic timescale with closure by a supra tidal berm of depositional origin the observations were made following a mechanical opening of the entrance and show very rapid vertical growth of an initially low beach berm as a result of swash overtopping and sediment overwash very little simultaneous seaward progradation was observed sediment overwash volumes were obtained from survey data over a period of 12 days either side of spring tide and the observations also provide an accurate measure of swash sediment transport at the berm crest a process based parametric model is developed through robust parameterisations of wave run up wave run up distributions and sediment transport and is applied to predict the total overwash transport into and infilling the estuary entrance the model is tested against the field data and compares well with the observations while the field data are site specific the proposed modelling framework represents a first step in modelling the complex growth and recovery of natural beach berms in broad scale morphodynamic models

compositional trends among iid irons their possible formation from the p rich lower magma in a two layer core group iid is the fifth largest group of iron meteorites and the fourth largest magmatic group i e that formed by fractional crystallization we report neutron activation data for 19 of 21 known iid irons these confirm earlier studies showing that the group has a relatively limited range in ir concentrations a factor of 5 this limited range is not mainly due to incomplete sampling instead it seems to indicate low solid liquid distribution coefficients reflecting very low s contents of the parental magma the same explanation responsible for the limited range in group iva despite this similarity these two groups have very different volatile patterns group iva has very low abundances of the volatile elements ga sb and ge whereas in group iid ga and sb abundances are the highest known in a magmatic group of iron meteorites and ge abundances are the second highest after group iiab group iid appears to be the only large magmatic group having high volatile abundances but low s in the volatile depleted groups iva and ivb it is plausible that s was lost as a volatile from a chondritic precursor material because group iid seems to have experienced minimal loss of volatiles we suggest that s was lost as an early melt having a composition near that of the fe fes eutectic 315 mg g s when temperatures had risen 400 500 k higher p rich melts formed became gravitationally unstable and drained through the first melt to form an inner core that was parental to the iid irons as discussed by kracher a wasson j t 1982 the role of s in the evolution of the parental cores of the iron meteorites geochim cosmochim acta46 2419 2426 it is plausible that a metal rich inner core and a s rich outer core could coexist metastably because stratification near the interface permitted only diffusional mixing the initial liquidus temperature of the inner p rich core is estimated to have been 1740 k after 60 crystallization the increase in p and the decrease in temperature may have permitted immiscibility with the s rich outer core we have not recognized samples of the outer core

the early stages of shallow flows in an inclined flume the motion of an initially quiescent shallow layer of fluid within an impulsively tilted flume is modelled using the nonlinear shallow water equations analytical solutions for the two dimensional flow are constructed using the method of characteristics and in regions where neither of the characteristic variables is constant by adopting hodograph variables and using the riemann construction for the solution these solutions reveal that the motion is strongly influenced by the impermeable endwalls of the flume they show that discontinuous solutions emerge after some period following the initiation of the flow and that for sufficiently long flumes there is a moving interface between wetted and dry regions using the hodograph variables we are able to track the evolution of the flow analytically after the discontinuities develop we also calculate the velocity and height fields by using jump conditions to express conservation of mass and momentum across the shock and thus we show how the hydraulic jump moves within the domain and how its magnitude grows in addition to providing the behaviour of the flow in this physical scenario this unsteady solution also provides an important test case for numerical algorithms designed to integrate the shallow water equations

recent advances in modeling swash zone dynamics influence of surf swash interaction on nearshore hydrodynamics and morphodynamics the role of the swash zone in influencing the whole nearshore dynamics is reviewed with a focus on the interaction between surf and swash zone processes local and global hydromorphodynamic phenomena are discussed in detail and a description of the overall swash zone operation is given the effects of swash zone boundary conditions are highlighted together with the importance of surf zone boundary conditions major emphasis is placed on illustrating the interactions of various hydrodynamic modes which in turn control the swash and surf zone morphology finally methods to account for swash zone processes in coastal models with different temporal and spatial resolutions are proposed

an experimental investigation into the metastable formation of phosphoran olivine and pyroxene abstract the formation of phosphoran olivine by crystallization from a melt was investigated experimentally using a one atmosphere furnace using san carlos olivine mg fe 2 sio 4 mixed with either iron phosphide fep or magnesium pyrophosphate mg 2 p 2 o 7 both dynamic crystallization and isothermal experiments produced phosphoran olivine as zoned single crystals and as overgrowths surrounding normal phosphorus free olivine grains the crystallization pathways that form phosphoran olivine were traced and confirm that it is a metastable phase that can crystallize from a phosphorus rich melt over timescales of hours to days removal of the p and equilibration of the olivine however requires weeks to months in the presence of silicate melt phosphoran olivine with up to 27 wt p 2 o 5 was generated and up to 69 of the si tetrahedral sites were replaced by p the substitution of si by p into olivine was confirmed as 4 vi m 2 2 iv si 4 3 vi m 2 2 iv p 5 vi phosphoran olivine compositions that vary from mg fe 2 sio 4 to mg fe 1 65 0 35 si 0 3 p 0 7 o 4 have been produced in these experiments phosphoran pyroxene was also generated in a few experiments and forms when phosphoran olivine reacts with either tridymite or melt it has compositions compatible with protopyroxene orthopyroxene pigeonite and sub calcic augite and can contain up to 31 5 wt p 2 o 5 like phosphoran olivine it is also a metastable phase phosphorus replaces si in pyroxene by the following substitution methods 8 iv si 4 3 iv si 4 4 iv p 5 iv with al entering the structure by the exchange 2 iv si 4 iv al 3 iv p 5 phosphoran pyroxene compositions vary from mg fe 8 si 8 o 24 to mg fe 8 si 3 p 4 o 24

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

well balanced and flexible morphological modeling of swash hydrodynamics and sediment transport abstract existing numerical models of the swash zone are relatively inflexible in dealing with sediment transport due to a high dependence of the deployed numerical schemes on empirical sediment transport relations moreover these models are usually not well balanced meaning they are unable to correctly simulate quiescent flow here a well balanced and flexible morphological model for the swash zone is presented the nonlinear shallow water equations and the exner equation are discretized by the shock capturing finite volume method in which the numerical flux and the bed slope source term are estimated by a well balanced version of the slic slope limited centered scheme that does not depend on empirical sediment transport relations the satisfaction of the well balanced property is demonstrated through simulating quiescent coastal flow the quantitative accuracy of the model in reproducing key parameters i e the notional shoreline position the swash depth the flow velocity the overtopping flow volume the beach change depth and the sediment transport rate is shown to be satisfactory through comparisons against analytical solutions experimental data as well as previous numerical solutions this work facilitates an improved modeling framework for the swash hydrodynamics and sediment transport

a petrological and chemical reexamination of main group pallasite formation abstract the large number of pallasite parent bodies suggests that their formation was a common event in asteroid evolution new microprobe data has been generated for pallasite olivines and chromites that indicate subsolidus redox processes while literature data has been collated and correlated to form new results and interpretations the new data include information on metal compositions the metal cooling rates the formation of round and fragmental olivine the close packing of olivine the crystallization of the phosphates phosphoran olivine and orthopyroxene and the bulk pallasite p and s contents a model for main group pallasites has been developed using fractional melting of a chondritic precursor to make a multi layered parent body one portion of this contains a gradational metal olivine pallasite texture concentric downward crystallization of the molten metal is indicated based on cooling rates and metal compositions fractional crystallization of the residual silicate and metallic melts produces the minor phases on cooling comparisons to and a brief review of past models particularly those utilizing mixing have been made

suspended sediment transport under seiches in circular and elliptical basins abstract enclosed bodies of water such as lakes or harbours often experience large scale oscillatory motions seiching as a simple model of such flow we investigate exact solutions to the shallow water equations which represent oscillatory flow in an elliptical basin with parabolic cross section specifically we consider two fundamental modes of oscillation in one of which the flow is parallel to the axis of the ellipse while in the other it is radial we obtain periodic analytical solutions for sediment transport including erosion deposition and advection under either mode of oscillation and present a method for obtaining such solutions for a more general class of flow fields and sediment transport models our solutions provide estimates of the morphodynamical importance of seiching motions and also reveal a characteristic pattern of net erosion and deposition associated with each mode in particular we find that a net flux of suspended sediment can be transported from the deeper to the shallower regions of the basin these transport patterns which are driven essentially by settling lag are highly robust to the formulation of the sediment transport relation and appear not to be substantially affected by the omission of frictional terms in the hydrodynamics they should thus provide considerable insight into sediment transport in less idealised systems

swash overtopping on plane beaches reconciling empirical and theoretical scaling laws using the volume flux abstract existing empirical and theoretical models for swash overtopping are considered and reconciled by using the positive volume flux of the incident waves and the deficit in freeboard as scaling parameters this scaling holds for solitary waves monochromatic waves and random waves the empirical model of battjes 1974 the eurotop model eurotop 2016 and the theoretical model of peregrine and williams 2001 can all be written in terms of the positive volume flux with consistent coefficients this scaling can be rationalised physically by equating the positive volume flux to the volume of fluid displaced by a wavemaker the empirical exponential vertical scaling in eurotop is very similar to the empirical vertical scaling identified by battjes 1974 here it is shown that the latter can be rationalised theoretically from a simple ballistic swash model new experiments on swash overtopping a truncated plane beach are presented for monochromatic and random waves and shown to scale well with these two parameters data for equivalent smooth planar beaches from the clash database are compared to the new scaling with good agreement the influence of beach slope on overtopping has some uncertainty between the theoretical and empirical models and in the present data particularly for high deficit in freeboard as the truncation point approaches the still water line this is likely to be a result of different processes occurring in the surf and swash zones or over the subaqueous beach face and sub aerial beach face

an integral treatment of friction during a swash uprush abstract the effects of bed friction are modelled for the flow near the moving shoreline during the uprush phase of a swash event by extending the pohlhausen method used by whitham 1955 to a sloping bed the tip of the swash near the moving shoreline is treated in an integral sense as a region of uniform velocity being acted on by the forces of friction gravity and the pressure force induced by the frictionless flow behind the swash tip the bed shear stress is parameterized by using the quadratic dependence on velocity the theory is compared to data of the shoreline velocity and position in the swash of breaking solitary waves and the friction coefficient is determined from direct measurements of bed shear stress the theoretical predictions are in good agreement with the laboratory results in terms of time history of the shoreline velocity and position as well as the run up

formation of phosphorus rich olivine in dar al gani 978 carbonaceous chondrite through fluid assisted metamorphism phosphorus rich olivine p 2 o 5 1 wt is a mineral that has been reported only in a few terrestrial and extraterrestrial occurrences previous investigations suggest that p rich olivine mainly forms through rapid crystallization from high temperature p rich melts here we report a new occurrence of p rich olivine in an ungrouped carbonaceous chondrite dar al gani dag 978 the p rich olivine in dag 978 occurs as lath shaped grains surrounding low ca pyroxene and olivine grains the lath shaped olivine shows a large variation in p 2 o 5 0 5 5 wt the p rich olivine grains occur in a chondrule fragment and is closely associated with chlorapatite merrillite feni metal and troilite tiny cr rich hercynite is present as inclusions within the p rich olivine the lath shaped texture and the association with cr rich hercynite indicates that the p rich olivine in dag 978 formed by replacing low ca pyroxene precursor by a p rich fluid during a thermal event rather than by crystallization from a high temperature melt the large variation of p 2 o 5 within olivine grains on micrometer scale indicates a disequilibrium formation process of the p rich olivine the occurrence of p rich olivine in dag 978 reveals a new formation mechanism of p rich olivine

the swash of solitary waves on a plane beach flow evolution bed shear stress and run up the swash of solitary waves on a plane beach is studied using large scale experiments ten wave cases are examined which range from non breaking waves to plunging breakers the focus of this study is on the influence of breaker type on flow evolution spatiotemporal variations of bed shear stresses and run up measurements are made of the local water depths flow velocities and bed shear stresses using a shear plate sensor at various locations in the swash zone the bed shear stress is significant near the tip of the swash during uprush and in the shallow flow during the later stages of downrush in between the flow evolution is dominated by gravity and follows an explicit solution to the nonlinear shallow water equations i e the flow due to a dam break on a slope the controlling scale of the flow evolution is the initial velocity of the shoreline immediately following waveform collapse which can be predicted by measurements of wave height prior to breaking but also shows an additional dependence on breaker type the maximum onshore directed bed shear stress increases significantly onshore of the stillwater shoreline for non breaking waves and onshore of the waveform collapse point for breaking waves a new normalization for the bed shear stress which uses the initial shoreline velocity is presented under this normalization the variation of the maximum magnitudes of the bed shear stress with distance along the beach which is normalized using the run up follows the same trend for different breaker types for the uprush the maximum dimensionless bed shear stress is approximately 0 01 whereas for the downrush it is approximately 0 002

an exact solution for ideal dam break floods on steep slopes dam break floods on steep slopes occur in diverse settings they may result from failure of either natural or man made dams and they have been responsible for the loss of thousands of lives costa 1988 recent disasters resulting from dam break floods on steep slopes include those at fonte santa mines portugal in november 2006 and taum sauk missouri usa in december 2005 numerical solutions of the shallow water equations are generally used to predict the behavior of dam break floods but exact analytical solutions suitable for testing these numerical solutions have been available only for floods with infinite volumes horizontal beds or both computational models used to simulate dam break floods commonly produce numerical instabilities and or significant errors close to the moving front when steep slopes and or irregular terrain are present in the flood path in part these problems reflect the complex interaction of phenomena not included in model formulation e g intense sediment transport under timedependent flow conditions but in part they also reflect shortcomings in the numerical solution algorithms themselves therefore it is important to obtain exact analytical solutions of the shallow water equations that can be used to test the robustness of numerical models when they are applied to floods of finite volume on steep slopes this paper presents a new solution for this purpose

run up and backwash bore formation from dam break flow on an inclined plane nonlinear shallow water equations are employed to model the inviscid slumping of fluid along an inclined plane and analytical solutions for the motion are derived using the hodograph transformation to reveal the run up and the inception of a bore on the backwash starting from rest the fluid slumps along the inclined plane attaining a maximum run up before receding and forming a relatively thin and fast moving backwash this interacts with the less rapidly moving fluid within the interior to form a bore the evolution of the bore and the velocity and height fields either side of it are also calculated to reveal that it initially grows in magnitude before diminishing and intersecting with the shoreline this analytical solution reveals features of the solution such as the onset of the bore and its growth and decline previously known only through numerical computation and the method presented here may be applied quite widely to the run up of other initial distributions of fluid

swash flow properties with bottom resistance based on the method of characteristics in the swash zone an assessment of swash flow properties requires an understanding of swash depth and swash velocity which can affect sediment movement as well as the design of coastal structures the method of characteristics provides a useful tool to model unsteady shallow water flows such as dam break flow swash flow and tsunami run up in this paper bottom resistance was incorporated into the nonlinear shallow water equations to extend the application of the method of characteristics to account for frictional effects in the swash zone the new characteristic equations are solved by the specified time interval scheme the bottom resistance has little influence on the seaward swash hydrodynamics initial swash stage e g water depth and flow velocity while its influence becomes significant in the small water depth region near the swash front which reduces the maximum run up height at a specified time and location and comparing with a frictionless swash solution the uprush flow velocity reduces due to the bottom resistance while the flow velocity increases during the initial phase of the backwash owing to the earlier reversal time with the bottom resistance however the differences with the inviscid solution are small within the swash lens conversely the maximum backwash velocity is reduced significantly as a result of the shorter duration of the backwash consistent with previous field observations friction does not significantly alter the gradient of the water surface elevation and a seaward dipping water surface elevation is observed during the majority of the swash process the dominant effect of bottom resistance is to reduce the range of inundation particularly with larger resistance coefficients the incorporation of the bottom resistance extends the application of method of characteristics in the swash zone to more practical problems particularly where run up elevation is critically important e g overtopping flows

swash overtopping and sediment overwash on a truncated beach new experimental laboratory data are presented on swash overtopping and sediment overwash on a truncated beach approximating the conditions at the crest of a beach berm or inter tidal ridge runnel the experiments provide a measure of the uprush sediment transport rate in the swash zone that is unaffected by the difficulties inherent in deploying instrumentation or sediment trapping techniques at laboratory scale overtopping flow volumes are compared with an analytical solution for swash flows as well as a simple numerical model both of which are restricted to individual swash events the analytical solution underestimates the overtopping volume by an order of magnitude while the model provides good overall agreement with the data and the reason for this difference is discussed modelled flow velocities are input to simple sediment transport formulae appropriate to the swash zone in order to predict the overwash sediment transport rates calculations performed with traditional expressions for the wave friction factor tend to underestimate the measured transport additional sediment transport calculations using standard total load equations are used to derive an optimum constant wave friction factor of f w 0 024 this is in good agreement with a broad range of published field and laboratory data however the influence of long waves and irregular wave run up on the overtopping and overwash remains to be assessed the good agreement between modelled and measured sediment transport rates suggests that the model provides accurate predictions of the uprush sediment transport rates in the swash zone which has application in predicting the growth and height of beach berms c 2005 elsevier b v all rights reserved

stony iron meteorites history of the metal phase according to tungsten isotopes abstract the global composition of the early solar system is thought to be roughly chondritic in terms of refractory components and this means that metal and silicate should be present together in early planetesimals to fully understand the metal silicate differentiation process within the eucrite parent body epb it is important to try and identify the metal reservoir that is complementary to the silicate part the isotope 182 of tungsten w a siderophile element is partly formed from the decay of 182 hf and w isotopes are useful for examining metal silicate segregation the w isotopic composition expected for the metal that is complementary to eucrites falls in the range of iron meteorites however mesosiderites seem to be genetically linked to eucrites based on petrologic and oxygen isotopic similarities therefore we undertook the analysis of the metal phase of these stony irons here we present tungsten isotopic data for mesosiderite and pallasite metal to characterize their parent body bodies and to assess possible relationships with eucrites all stony iron metals are depleted in radiogenic tungsten by 1 3 to 4 2 e units relative to the terrestrial standard while chondrites for comparison are depleted by 1 9 e units in addition to w isotopic heterogeneity from one stony iron to another there is also w isotopic heterogeneity within individual meteorites a formation model is tentatively proposed where we show that mesosiderites pallasites and eucrites could possibly come from the same parent body several hypotheses are discussed to explain the isotopic heterogeneity the production of cosmogenic tungsten the in situ decay of hafnium present in inclusions and tungsten diffusion processes after metal silicate mixing during the cooling of the meteorites the two latter hypotheses provide the best explanation of our data

total nitrogen in iron meteorites total nitrogen contents have been measured by rna of 30 iron and 4 stony iron meteorites wide variations in n concentrations are noted 0 5 ppm to about 200 ppm as a group the ia irons have the highest nitrogen this element is positively correlated with c ga and ge samples of meteorites that have been exposed to shock do not show any abnormal n distribution

massive chromite in the brenham pallasite and the fractionation of cr during the crystallization of asteroidal cores abstract large 2 mm chromite grains are present in iiiab iron meteorites and in the main group pallasites pmg closely related to high au iiiab irons pallasites seem to have formed by the intrusion of a highly evolved metallic magma from a iiiab like core into fragmented olivine of the overlying dunite mantle high cr contents are commonly encountered during the analyses of metallic samples of high au iiiab irons and main group pallasites an indication that cr contents were high in the intruding liquid and that cr behaved as an incompatible element during the crystallization of the iiiab magma contrary to expectations based on the negative iiiab cr ni and cr au trends among low au iiiab irons in a region about 10 cm across in the brenham main group pallasite massive chromite fills the interstices between olivine grains the site normally occupied by metal in brenham and other pallasites the massive chromite may have formed as a late cumulus phase because fe ni was also crystallizing its absence in the chromite rich region suggests a separation associated with differences in liquid buoyancy the coexisting chromite and olivine are zoned in the olivine feo is highest in pallasitic olivine metal regions lowest in rims adjacent to chromite and intermediate in the cores of these olivines chromite shows the opposite zoning with the highest feo contents at grain edges adjacent to olivine the observed gradients are those expected to form by fe mg exchange between olivine and chromite during slow cooling at subsolidus temperatures compared to normal brenham contents of phosphoran olivine and phosphates are higher in the chromitic pallasitic region we also report data for large to massive chromites present in pmg molong and in high au iiiab bear creek that like brenham formed from a highly evolved magma the bear creek chromite has a much lower mg content than that in the pallasites implying that in the pmg the mg was extracted from the olivine during high temperature reaction with the precipitating chromite there are other circumstantial arguments indicating that cr was incompatible in the metal during the crystallization of the iiiab magma with the concentration in the residual magma rising from an initial value of about 300 g g to a value around 700 g g when bear creek and brenham were formed we consider possible explanations for these negative cr au and cr ni trends and find the most probable one to be that they reflect sampling artefacts resulting from analysts avoiding visible chromite and the commonly associated phase fes when choosing metal samples

mineralogy petrology and distribution of meteorites at the whitecourt crater alberta canada the whitecourt meteorite impact crater alberta canada is a rare example of a well preserved small impact structure with which thousands of meteorite fragments are associated as such this crater represents a unique opportunity to investigate the effect of a low energy impact event on an impacting iron bolide excellent documentation of meteorite fragment locations and characteristics has generated a detailed distribution map of both shrapnel and regmaglypted meteorite types the meteorites distribution and internal and external characteristics support a low altitude breakup of the impactor which caused atmospherically ablated regmaglypted meteorites to fall close to the crater and avoid impact related deformation in contrast shrapnel fragments sustained deformation at macro and microscales resulting from the catastrophic disruption of the impactor the impactor was significantly fragmented along pre existing planes of weakness including kamacite lamellae and inclusions resulting in a bias toward low mass 100 g fragments meteorite mineralogy was investigated and the accessory minerals were found to be dominated by sulfides and phosphides with rare carlsbergite consistent with other low ni iiiab iron meteorites considerations of the total mass of meteoritic material recovered at the site relative to the probable fraction of the impactor that was preserved based on modeling suggests that the crater was formed by a higher velocity lower mass impactor than previously inferred

an experimental study of the interaction of two successive solitary waves in the swash a strongly interacting case and a weakly interacting case abstract the interaction of successive solitary waves in the swash zone have been studied using large scale experiments with a simple bathymetry of a constant depth region where the water depth was 1 72 m and a plane beach whose slope was 1 12 two wave cases were considered where two successive solitary waves of the same height were generated one after the other so that the wave crests were separated by the effective wavelength associated with a single solitary wave in the weakly interacting case the swash period associated with a single solitary wave is smaller than the time period separating the successive wave crests which leads to similar run ups for the first and second wave whereas in the strongly interacting case the swash period associated with a single solitary wave is larger than the time period separating the successive wave crests which leads to a significant reduction in the run up of the second wave the degree to which there is an interaction between the swash uprush of the second wave and the downrush of the first wave is found to be related to the solitary wave slope parameter which predicts breaker type of the first wave previous data from literature are found to support this claim measurements of bed shear stress bed pressure and the free surface displacement at a location near the stillwater shoreline are used to describe how the dynamics of the boundary layer differ when the downrush of the first wave meets the incoming second wave in both cases

eulerian flow velocities in the swash zone field data and model predictions measurements of eulerian flow velocity obtained within the swash zone on a relatively steep beach face gradient 1 23 are compared with an extended ballistic swash model the model only requires a friction factor beach slope and terminal bore velocity as input the following model predictions matched well with observations 1 the maximum eulerian flow velocity is the shoreline velocity when it arrives at the fixed point of interest on the beach face 2 at any location the time of flow reversal occurs prior to the shoreline reaching its maximum landward excursion 3 the maximum flow velocity in the backwash is the velocity recorded as the shoreline recedes past the fixed point of interest and this is less than the maximum uprush velocity and 4 the duration of the uprush flow is shorter than the duration of the backwash flow previous studies have already confirmed that the ballistic swash model including friction can accurately predict shoreline motion and maximum run up on steep beaches this study shows that it is similarly successful in predicting eulerian flow velocities during individual swash events the model does not presently account for interacting swash however and so may be less appropriate on gently sloping beaches

forces on a vertical wall on a dike crest due to overtopping flow abstract wave overtopping a sea dike may pose a threat to people and property however knowledge of the overtopping features in particular overtopping flow loads are not well understood the aim of this study was to understand the overtopping process on a dike crest and to develop an empirical formula for the resulting overtopping flow impact loads on a wall as a function of the property of the incoming waves and dike geometry characteristics in this paper we propose a new descriptor the overtopping momentum flux in order to predict the impact loads to validate the proposed empirical function a series of physical scale model tests was conducted in these experiments we measured the overtopping flow loads on a vertical wall at different locations on a dike which were induced by broken waves a correction coefficient for the wall effect on the initial flow depth and an empirical initial flow depth coefficient for a broken wave were determined these empirical coefficients allowed for an interpretation of the overtopping process of a broken wave from dike toe up to the front of the wall on the dike

zoning of phosphorus in igneous olivine we describe p zoning in olivines from terrestrial basalts andesites dacites and komatiites and from a martian meteorite p2o5 contents of olivines vary from below the detection limit 0 01 wt to 0 2 0 4 wt over a few microns with no correlated variations in fo content zoning patterns include p rich crystal cores with skeletal hopper or euhedral shapes oscillatory zoning structures suggesting replacement of p rich zones by p poor olivine and sector zoning melt inclusions in olivines are usually located near p rich regions but in direct contact with low p olivine crystallization experiments on basaltic compositions at constant cooling rates 15 30 c h reproduce many of these features we infer that p rich zones in experimental and natural olivines reflect incorporation of p in excess of equilibrium partitioning during rapid growth and zoning patterns primarily record crystal growth rate variations occurrences of high p phenocryst cores may reflect pulses of rapid crystal growth following delayed nucleation due to undercooling most cases of oscillatory zoning in p likely reflect internal factors whereby oscillating growth rates occur without external forcings but some p zoning in natural olivines may reflect external forcings e g magma mixing events eruption that result in variable crystal growth rates and or p contents in the magma in experimental and some natural olivines al cr and p concentrations are roughly linearly and positively correlated suggesting coupled substitutions but in natural phenocrysts cr zoning is usually less intense than p zoning and al zoning weak to absent we propose that olivines grow from basic and ultrabasic magmas with correlated zoning in p cr and al superimposed on normal zoning in fe mg rapidly diffusing divalent cations homogenize during residence in hot magma al and cr only partially homogenize and delicate p zoning is preserved because p diffuses very slowly this interpretation is consistent with the fact that zoning is largely preserved not only in p but also in al cr and divalent cations in olivines with short residence times at high temperature e g experimentally grown olivines komatiitic olivines groundmass olivines and the rims of olivine phenocrysts grown during eruption p zoning is widespread in magmatic olivine revealing details of crystal growth and intra crystal stratigraphy in what otherwise appear to be relatively featureless crystals since it is preserved in early formed olivines with prolonged residence times in magmas at high temperatures p zoning has promise as an archive of information about an otherwise largely inaccessible stage of a magma s history study of such features should be a valuable supplement to routine petrographic investigations of basic and ultrabasic rocks especially because these features can be observed with standard electron microprobe techniques

shoreline motion in nonlinear shallow water coastal models abstract different shoreline boundary conditions for numerical models of the non linear shallow water equations based on godunov type schemes are compared the study focuses on the peregrine and williams peregrine d h williams s m 2001 swash overtopping a truncated plane beach journal of fluid mechanics 440 391 399 problem of a single bore collapsing on a slope this is considered the best test to assess performances of the shoreline boundary treatments in terms of all the parameters of interest in swash zone modelling emphasis is given to the shoreline trajectory and flow velocity modelling a mismatch of the velocity at the early stage of the motion is highlighted most of the tested techniques perform similarly in terms of maximum run up the backwash phase is critical in all cases starting from the brocchini et al brocchini m bernetti r mancinelli a albertini g 2001 an efficient solver for nearshore flows based on the waf method coastal engineering 43 2 105 129 shoreline boundary treatment a simple technique that improves the accuracy of velocity predictions is also developed a sensitivity analysis of the domain resolution and the threshold value of the water depth that defines a wet cell is also presented

the influence of seaward boundary conditions on swash zone hydrodynamics abstract the influence of the seaward boundary condition on the internal swash hydrodynamics is investigated new numerical solutions of the characteristics form of the nonlinear shallow water equations are presented and applied to describe the swash hydrodynamics forced by breaking wave run up on a plane beach the solutions depend on the specification of characteristic variables on the seaward boundary of the swash zone equivalent to prescribing the flow depth or the flow velocity it is shown that the analytical solution of shen and meyer shen m c meyer r e 1963 climb of a bore on a beach part 3 runup j fluid mech 16 113 125 is a special case of the many possible solutions that can describe the swash flow but one that does not appear appropriate for practical application for real waves the physical significance of the boundary conditions is shown by writing the volume and momentum fluxes in terms of the characteristic variables results are presented that illustrate the dependence of internal flow depth and velocity on the boundary condition this implies that the internal swash hydrodynamics depend on the shape and wavelength of the incident bore which differs from the hydrodynamic similarity inherent in the analytical solution a solution appropriate for long bores is compared to laboratory data to illustrate the difference from the analytical solution the results are important in terms of determining overwash flows flow forces and sediment dynamics in the run up zone

experimental investigations of trace element fractionation in iron meteorites ii the influence of sulfur abstract we have investigated the partitioning of ir ge ga w cr au p and ni between solid metal and metallic liquid as a function of temperature and s concentration of the metallic liquid partition coefficients for siderophile elements such as ir w ga and ge increase by factors of 10 100 as the sconcentration of the metallic liquid increases from 0 30 wt partition coefficients for other siderophile elements such as ni au and p increase by only factors of 2 3 in contrast partition coefficients for the more chalcophile element cr decrease these experimentally determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of ni p au and ir during the magmatic evolution of groups iiab iiiab iva and ivb iron meteorites the mean s concentration for each group increases in the order ivb iva iiiab iiab in accord with cosmochemical prediction however we are unable to reproduce the geochemical behavior of ge ga w and cr in an internally consistent way we conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed

large scale laboratory measurements of solitary wave inundation on a 1 20 slope abstract the run up flow and related pressure of solitary waves breaking on a 1 20 plane beach were investigated experimentally in a super tank 300 m 5 m 5 2 m swash flow measurements of flow velocities are compared with an existing analytical solution by incorporating an analytical solution the hydrodynamic pressure for a quasi steady flow state is determined and compared with laboratory data concerning the evident extra pressure exerted by the impact of swash flow an empirical drag coefficient for a circular plate is also suggested in the present study

experimentally determined subsolidus metal olivine element partitioning with applications to pallasites pallasite meteorites which consist primarily of olivine and metal may be remnants of disrupted core mantle boundaries of differentiated asteroids or planetesimals the early thermal histories of pallasites are potentially recorded by minor and trace element zonation in olivine however constraining this history requires knowledge of element behavior under the conditions of pallasite formation which is lacking for many of the main elements of interest e g co cr mn in this study we experimentally determined metal olivine partition coefficients for fe ni co cr and mn in a pallasite analogue at subsolidus temperatures metal olivine partition coefficients km increase in the order kmn kcr 1 kfe kco kni with five orders of magnitude separating kmn from kni transition metals also become more siderophile with increasing experimental temperature 900 to 1550 c the experiments incidentally produced diffusion profiles in olivine for these elements our results suggest they diffuse through olivine at similar rates core compositions of pallasite olivines are consistent with high temperature equilibration with feni metal olivine zonation toward crystal rims varies significantly for the investigated transition metals we suggest rim zonation results from partial re equilibration during late stage crystallization of minor phases e g chromite phosphates this re equilibration occurred over short timescales relative to overall pallasite cooling likely tied to initial cooling rates on the order of 100 300 c myr

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

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

morphological analysis of olivine grains annealed in an iron nickel matrix experimental constraints on the origin of pallasites and on the thermal history of their parent bodies two types of pallasites can be distinguished on the basis of the grain shape of olivine rounded or angular it has been suggested that these two types of textures resulted from different degrees of annealing at high temperature in the parent body in order to characterize the kinetics of rounding of olivine grains in an fe ni matrix we carried out a series of annealing experiments using a mixture of olivine and fe ni powder we were able to reproduce at a miniature scale the range of textures in pallasites the rate of rounding was rapid enough to be observed and measured at the scale of a few micrometers to 20 m even though the experiments were performed below the solidus of the fe ni metal for instance grains 14 m in diameter became nearly spherical within 7 days at 1400 oc for the morphological analysis of olivine grains we used two independent techniques the critical diameter method and the gaussian diffusion resample method a new technique specially developed for our study both techniques indicate that the rounding time scale is proportional to the cube of the grain size and that morphological adjustments in our experiments occurred by volume diffusion in the olivine lattice not by surface diffusion along the olivine metal boundaries we used our experimental data to estimate the time scales required for the development of olivine metal textures in natural pallasites we determined that small scale rounding of olivine grains in a solid metal matrix can be produced within relatively short time intervals 100 years to produce rounded olivine grains 0 1 mm in radius at 1300 1400oc

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

identification of the projectile component in the impact structures rochechouart france and saaksjarvi finland implications for the impactor population for the earth a set of 11 impact melt rock samples from the rochechouart impact structure france and nine impact melt rock samples from saaksjarvi impact structure finland were studied for their major and trace element compositions including the abundances of the platinum group elements the main goal of this study was to identify the projectile type s responsible for the formation of these two impact structures the results confirmed previous studies that suggested extraterrestrial contamination in both the rochechouart and saaksjarvi impact melt rocks the projectile types found for rochechouart and saaksjarvi are quite similar and compatible with the composition of non magmatic iron meteorites ia and iiic this interpretation is based on identical platinum group element patterns as well as peculiar ni cr ni ir and cr ir ratios which can be explained by mixing of the different components of non magmatic iron meteorites this result indicates that besides ordinary chondrites non magmatic iron may be among the most common material impacting the earth as they also represent the majority of the projectiles for craters smaller that 1 5 km the abundance of non magmatic irons as projectiles as well as their composition olivine pyroxene and iron supports the assumption that a fraction of the s type asteroids could by related to this type of material

chemical zoning of olivine in several pallasites chemical zoning profiles of olivines in the esquel imilac and yamato 8451 pallasites were measured by using an electron probe microanalyzer in order to study their cooling histories pallasite olivines are considered to be compositionally uniform but show faint zoning for fe mg cao al2o3 cr2o3 and mno within a few hundred micrometers from the rim the cao al2o3 and cr2o3 contents of olivines in pallasites decrease gradually toward the rim the fe mg zoning and the mno enrichment in olivine rims of pallasite olivines may reflect a redox process on the basis of diffusion calculations to estimate the cooling rate by using chemical zoning of pallasite olivine the formation process of chemical zoning was discussed similar cooling rates obtained for the fe mg cao and mno profiles of an olivine imply that these zoning patterns formed during the same event

an investigation of the behavior of cu and cr during iron meteorite crystallization the measured cu and cr contents in magmatic iron meteorites appear to contradict the behavior predicted by experimental fractional crystallization studies currently available to investigate the origin of cu and cr concentrations observed in these meteorites a thorough set of solid metal liquid metal experiments were conducted in the fe ni s system in addition to cu and cr partitioning values were also determined for as au bi co mo ni pb rh ru sb sn v and zn from the experiments experimental results for cu and cr showed similar chalcophile partitioning behavior whereas these elements have differently sloped trends within magmatic iron meteorite groups thus fractional crystallization alone cannot control both the cu and cr concentrations in these iron meteorite groups a simple fractional crystallization model based on our experimental cu partitioning results was able to match the cu versus au trend observed in the s poor ivb iron meteorite group but not the decreasing cu versus au trends in the iiab and iiiab groups or the unique s shaped cu versus au trend in the iva group however the crystallization model calculations were found to be very sensitive to the specific choice for the mathematical expression of d cu suggesting that any future refinement of the parameterization of d cu should include a reassessment of the cu fractional crystallization trends the cr versus au trends in magmatic iron meteorite groups are steeper than those of cu and not explained by fractional crystallization other influences such as the removal of chromite from the crystallizing system or sampling biases during iron meteorite compositional analyses are likely responsible for the cr trends in magmatic iron meteorite groups

chemical classification of iron meteorites xi multi element studies of 38 new irons and the high abundance of ungrouped irons from antarctica abstract we report concentrations of 14 elements in the metal of 38 iron meteorites and a pallasite the meteorites are classified based on these data and on structural observations three samples are paired with previously classified irons thus these additional 35 irons raise the number of well classified independent iron meteorites to 598 one yamato iron contains 342 mg g ni the second highest ni content in an iab iron after oktibbeha county two small irons from western australia appear to be metal nodules from mesosiderites several of the new irons are from antarctica of 24 independent irons from antarctica 8 are ungrouped the fraction 0 333 is much higher than the fraction 0 161 among all 598 classified irons statistical tests show that it is highly improbable 2 9 probability that the antarctic population is a random sample of the larger population the difference is probably related to the fact that the median mass of antarctic irons is about two orders of magnitude smaller than that of non antarctic irons it is doubtful that the difference results from fragmentation patterns yielding different size distributions favoring smaller masses among ungrouped irons more likely is the possibility that smaller meteoroids tend to sample a larger number of asteroidal source regions perhaps because small meteoroids tend to have higher ejection velocities or because small meteoroids have random walked a greater increment of orbital semimajor axis away from that of the parent body

mineral and chemical composition of the new iron meteorite javorje from slovenia abstract the single piece iron meteorite javorje with a mass of 4920 g is the heaviest and largest meteorite found in the territory of slovenia the meteorite javorje is a medium octahedrite with kamacite bandwidth of 0 85 0 26 mm the bulk composition of ni 7 83 wt co 0 48 wt and trace elements ga 25 g g ge 47 g g ir 7 6 g g as 5 8 g g au 0 47 g g and pt 13 4 g g indicates that the meteorite javorje belongs to the chemical group iiiab mineral and bulk chemical compositions are consistent with other reported group iiiab meteorites the presence of numerous rhabdites carlsbergite sparse troilite and chromite and abundance of daubreelites are in accordance with low ni and low p iiiab iron meteorites the severely weathered surface and secondary weathering products in the interior of the meteorite suggest its high terrestrial age

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

swash zone boundary conditions derived from optical remote sensing of swash zone flow patterns 1 optical remote sensing is used to measure flow patterns in the swash zone timestack images are analyzed to measure the asymmetry and the relative duration of the inflow into the swash zone this varies significantly between individual swashes contrary to the classical analytical swash model for runup induced by bores which predicts a similar flow pattern for all events for swash forced by breaking bores the gradient of the x t locus of flow reversal varies over a wide range and flow reversal can occur simultaneously across the whole swash zone this variation of the gradient of the locus of flow reversal in x t space can be parameterized in terms of a single free variable in recent solutions to the nonlinear shallow water equations which fully defines the swash boundary inflow condition consistent with the theory the horizontal runup the swash period and the swash similarity parameter were observed to be independent of the swash inflow conditions but the flow asymmetry is not only a weak correlation was observed between the swash boundary condition and the iribarren number and beach slope conversely the analysis suggests that the degree of swash swash interaction does influence the swash boundary condition and the resulting internal flow kinematics the variation in inflow conditions is expected to influence the magnitudes of the velocity moments within the swash zone and therefore sediment transport rates

efficient and robust wave overtopping estimation for impermeable coastal structures in shallow foreshores using swash abstract estimation of wave overtopping over the crest of coastal structures is crucial to design effective and cost efficient countermeasures against storms semi empirical formulas are often used for wave overtopping assessment but they are not always applicable for complex structures which exist in reality e g a storm wall on a dike in a shallow or very shallow foreshore detailed numerical models such as eulerian and lagrangian rans models have potential to simulate overtopping of complex coastal structures with good accuracy however such models require significant computational resources the use of such models is often not feasible for the design of coastal structures which often requires multiple iterations and model runs over a reasonably long period of time e g wave trains with 1000 individual waves in this paper we investigated the applicability of the simplified depth integrated wave transformation model swash for wave overtopping estimation of impermeable coastal structures in shallow foreshores the validation results demonstrate the capability of swash to predict mean wave overtopping discharge with good accuracy compared to results from four different overtopping experimental campaigns comprising 124 individual cases the overall performance of swash to estimate mean wave overtopping discharge is as accurate as those obtained by semi empirical equations in literature however in order to obtain accurate mean wave overtopping discharge with the swash model the incident wave properties at the toe of the dike need to be accurately reproduced for cases where this is not possible a correction method is proposed in this paper detailed validation of the instantaneous wave overtopping also shows a good agreement with physical model data in one example a single intensive overtopping event was not well resolved by the swash model and the instantaneous wave overtopping was under predicted however this did not contribute significantly to the mean wave overtopping discharge an additional advantage of the swash model is that specific coastal structure geometries can be modelled in swash if they are not covered by semi empirical equations even in a case with rapidly varied flow e g vertical wall on a dike the model shows sufficient robustness in this paper the details on the swash model configuration and post processing methods are outlined to enable the reader to reproduce reliable wave overtopping estimation over impermeable coastal structures in shallow foreshores

the influence of wave acceleration and volume on the swash flow driven by breaking waves of elevation abstract we study the swash flow driven by breaking waves of elevation using two sets of large scale experiments with a focus on understanding how wave properties control the flow evolution on the beach in the first set of experiments we test solitary waves and waveforms that have the same acceleration phase and wave height as the solitary waves but an elongated deceleration phase the results show that the run up and the flow in the immediate vicinity of the moving shoreline are similar showing that the shape of the wave acceleration phase controls these swash flow parameters in the second set of experiments we test waves generated by custom wavemaker trajectories previously reported in baldock et al 2019 in which the wave integrated volume flux wave height and wave period are varied the results show that waveforms with the same wave integrated volume flux produce nearly identical downrush flow despite having different wave heights and periods finally we present dimensionless plots of swash flow that illustrate the utility of separate scalings for uprush and downrush flow based on the wave acceleration and wave integrated volume flux respectively

unlocking the zinc isotope systematics of iron meteorites zinc isotope compositions 66zn and concentrations were determined for metal samples of 15 iron meteorites across groups iab iiab and iiiab also analyzed were troilite and other inclusions from the iab iron toluca furthermore the first zn isotope data are presented for metal silicate partitioning experiments that were conducted at 1 5 gpa and 1650 k three partitioning experiments with run durations of between 10 and 60 min provide consistent zn metal silicate partition coefficients of 0 7 and indicate that zn isotope fractionation between molten metal and silicate is either small at less than about 0 2 0 2 or absent metals from the different iron meteorite groups display distinct ranges in zn contents with concentrations of 0 08 0 24 g g for iiabs 0 8 2 5 g g for iiiabs and 12 40 g g for iabs in contrast all three groups show a similar range of 66zn values reported relative to jmc lyon zn from 0 5 0 5 to 3 0 3 0 with no clear systematic differences between groups however distinct linear trends are defined by samples from each group in plots of 66zn vs 1 zn and these correlations are supported by literature data based on the high zn concentration and 66zn 0 determined for a chromite rich inclusion of toluca modeling is employed to demonstrate that the zn trends are best explained by segregation of chromite from the metal phase this process can account for the observed zn 66zn cr systematics of iron meteorite metals if zn is highly compatible in chromite and zn partitioning is accompanied by isotope fractionation with 66znchr met 1 5 1 5 based on these findings it is likely that the parent bodies of the iab complex iiab and iiiab iron meteorites featured 66zn values of about 1 0 to 0 5 0 5 similar to the zn isotope composition inferred for the bulk silicate earth and results obtained for chondritic meteorites together this implies that most solar system bodies formed with similar bulk zn isotope compositions despite large differences in zn contents

la icp ms mapping of olivine from the brahin and brenham meteorites complex elemental distributions in the pallasite olivine precursor abstract to investigate the early history of olivine from the main group pallasites brahin and brenham we have spatially mapped their trace element distributions using laser ablation inductively coupled plasma mass spectrometry la icp ms brahin olivine interiors contain 100 200 m patches enriched in cr al ti v sc and ga separated by linear enrichments of p these structures bear no relation to current crystal morphologies rather cross cutting relationships suggest they predate olivine metal mixing brenham olivine also has internal variations for these elements by contrast ni and co concentrations in olivine from both meteorites decrease near crystal margins as expected for freezing in of profiles formed during diffusive re equilibration with metal during cooling brenham olivine also has decreasing al cr and ti near the margin correlations between concentrations of cr and al exist for individual brahin olivine grains but do not hold over multiple grains indicating a heterogeneous precursor al and ti are correlated over multiple grains in brahin interpreted as ti cations decorating pre existing al defects in brenham olivine similar geochemical trends exist but the cr al relationship probably represents both grain margin effects and pre existing internal heterogeneity the preservation of structure for elements which are normally fast diffusers in olivine hinges on coupled substitutions involving al which along with p diffuses much more slowly than most other elements under some conditions al concentrations in olivine are low and variable 3 33 ppm which is inconsistent with crystallisation from a normal silicate melt al in olivine thermometers indicate that pallasite olivine was formed in a low temperature environment following its delivery to the magma ocean core mantle boundary al p systematics were not substantially modified assuming diffusivities for al and p that are similar to si since they reside in the same crystallographic site and temperatures of 1600 1650 k from the melting point of the metal and the absence of orthopyroxene in pallasites an upper limit on the residence time of pallasite olivine of 1 ma can be inferred by the persistence of trace element detail over scales of 100 m following the olivine metal mixing event homogeneous ni and co distributions were modified by diffusion cr and v were partially modified al and p were essentially unchanged

impact of a uniform bore on an erodible beach abstract the impact of a uniform bore on an erodible beach is investigated using a shallow water description and a sediment conservation equation the solution which is obtained using the method of characteristics employs a cubic bed load formula and a crudely calibrated sediment transport coefficient it is found that as with the fixed bed case of hibberd and peregrine 1979 a backwash bore forms which for the mobile bed also comprises a bed step it is found that this bed step achieves a significant height the volume of sand deposited above the final still water level is consistent with that observed under certain events on some sandy beaches

paucity of sulfide in a large slab of esquel new perspectives on pallasite formation the 0 7 ton esquel meteorite found in patagonia before 1951 is a typical main group pallasite in most respects we examined petrographically a slab 1 m long having an area of 3000 cm2 that shows the typical pallasitic texture with fragmental olivine phase abundances in vol are olivine 66 metal 32 schreibersite 0 76 troilite 0 46 and chromite 0 31 esquel can be divided into four lithologies 1 pallasitic matrix consisting of olivine fragments embedded in metal 81 2 large 5 cm olivine nodules having low metal contents 18 3 massive metal 0 3 and 4 zones dominated by fes and fine olivine 0 7 main group pallasites appear to have formed by the intrusion of a highly evolved low ir high ni au and s metallic magma into fragmented olivine this model implies that fes should be abundant in main group pallasites and we had speculated that examination of an exceptionally large slab might reveal a high troilite content we found instead an exceptionally low fes content new compositional data confirm that esquel has a lower au content than other main group pallasites having similar ir contents literature data based however on relatively small sections suggest that high au pallasites have higher s contents than esquel but have lower s contents than expected from a trapped melt model we conclude that a relatively complex model is required to explain the origin of main group pallasites after intrusion the degree of crystallization of the metallic magma varied from location to location but in almost all cases an fes rich liquid either escaped or formed fes rich pallasitic rocks that are underrepresented in the meteorite inventory

measurements and modelling of the advection of suspended sediment in the swash zone by solitary waves novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone an experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse the advection scales and settling of this sediment were measured during the uprush along a rigid sediment free beach face by a sediment trap located at varying cross shore positions measurements were made using a number of repeated solitary broken waves or bores approximately 25 of the pre suspended sediment picked up by the bores reaches the mid swash zone 50 of the horizontal run up distance indicating the importance of the sediment advection in the lower swash zone the pre suspended sediment is sourced from a region seaward of the shoreline still water line which has a width of about 20 of the run up distance an eulerian lagrangian numerical model is used to model the advection scales of the suspended sediment the model resolves the hydrodynamics by solving the non linear shallow water equations in an eulerian framework and then solves the advection diffusion equation for turbulence and suspended sediment in a lagrangian framework the model provides good estimates of the measured mass and distribution of sediment advected up the beach face the results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre suspended sediment to the net sediment transport in the swash zone c 2009 elsevier b v all rights reserved

an analytical model for bore driven run up we use a hodograph transformation and a boundary integral method to derive a new analytical solution to the shallow water equations describing bore generated run up on a plane beach this analytical solution differs from the classical shen meyer runup solution in giving significantly deeper and less asymmetric swash flows and also by predicting the inception of a secondary bore in both the backwash and the uprush in long surf we suggest that this solution provides a significantly improved model for flows including swash events and the run up following breaking tsunamis

kinematics of breaking tsunami wavefronts a data set from large scale laboratory experiments abstract this paper provides an overview of a new large scale laboratory data set on the kinematics of breaking tsunami wavefronts the aim of the experiments was to provide an open access data set for model testing calibration and verification with particular emphasis on fluid kinematics in the wave breaking and run up swash zones the experiments were performed over a composite slope in the tsunami wave basin at the o h hinsdale wave research laboratory at oregon state university data for ten different wave conditions were collected including non breaking and breaking waves and both shore breaks and fully developed long bores surface elevation and fluid kinematics were measured with a closely spaced array of surface piercing wave gauges non contact ultrasonic wave gauges and four 3 d side looking acoustic doppler velocimeters the array was traversed from the nearshore depth 0 2 m to the middle and upper run up zone providing kinematic data at 30 cross shore locations video was also recorded from 4 cameras covering the propagation breaking and run up zones surface elevation flow velocities and the wave maker displacement were also recorded to provide offshore boundary conditions the experiments include conditions with wave heights up to 0 55 m notional wave periods up to 20 s and run up lengths of up to 15 2 m on a 1 30 slope in terms of the slope in the shoaling and breaker zones the data correspond to iribarren numbers in the range of 0 26 5 6 raw calibrated and processed data are stored with open access within the osu tsunami wave basin experiment notebook which provides full access to all the wave maker control signals data instrument coordinates and processing and plotting software this paper serves as an introduction to the data set demonstrates data quality and provides an initial analysis of some key parameters that govern the impact of tsunami events including run up versus offshore wave conditions and nearshore bore height the maximum inundation depths at the original shoreline position and the time to maximum inundation depth and flow reversal examples of temporal and convective accelerations and turbulent flow components are also presented to illustrate further details of the kinematics

swash overtopping a truncated plane beach swash on a plane beach is modelled by using a solution of the shallow water equations due to shen meyer 1963 the equations are used in a form appropriate for a plane at a finite angle to the horizontal the beach is cut off at a level below that of the maximum run up and the water is taken to fall freely over the end of the beach an explicit solution is found which permits evaluation of the overtopping flow and total volume for one swash event

numerical study of the flow structure at a swash tip propagating over a rough bed abstract understanding the boundary layer flow structure at the tip of a swash flow is important for improving predictions of wave run up coastal flooding and sediment transport processes on beaches but this is difficult to investigate experimentally recently there has been debate regarding the mechanics of boundary layer growth during the uprush flow here an extensively validated rans model is used to investigate the swash tip dynamics during a dam break driven swash event the model enables the analysis of the spatial and temporal variation of important parameters in particular the water surface gradients the bed shear stress and the non uniformity of the velocity profile the rate of flow convergence of surface particles toward the tip and the ratio of the depth averaged flow velocity and celerity of the swash tip are also obtained the flow depth varies with distance behind the wave tip approximately as a power law with a power of 1 2 3 4 the surface elevation dips offshore at distances greater than 0 2 m behind the front the shear stress decreases quite slowly in the spatial region immediately behind the wave tip and is in very good agreement with the flat plate boundary layer model of barnes and baldock 2010 the model results indicate that the boundary layer structure is well developed or depth limited at the wave tip and fits a power law velocity profile with an exponent of order 1 3 consistent with a rough bed the normalised vertical variation in the velocity profile is very uniform in the region 1 m behind the wave tip and matches that for a 1 3 power law alternate logarithmic fits to the velocity profile yield consistent values of bed roughness at different locations but corresponding to a grain size that is about twice that used in the experiment the rate of flow convergence of surface particles toward the wave tip is also consistent with a fully developed boundary layer and a 1 3 power law