a phase resolving cross shore sediment transport model for beach profile evolution abstract a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the mean undertow and the intra wave sediment concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone even for eroding beaches suggesting that other contributions should not be neglected the present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded

modelling gravel barrier profile response to combined waves and tides using xbeach laboratory and field results abstract xbeach a process based numerical model capable of computing nearshore circulation and morphodynamics including overwash and breaching has been used in 1d mode to simulate erosion occurring on a gravel barrier beach d50 11 mm subjected to wave and tidal forcing during selected tests undertaken during the bardex experiments the model demonstrated good quantitative skill brier skill score bss typically 0 65 with respect to beach face erosion offshore accretion and morphological impacts of washover xbeach was also used to model storm impacts on a steep average tan 0 12 4 5 km long and 100 m 140 m wide macrotidal gravel barrier d50 2 mm to 10 mm located in sw england although the development of a storm berm was not reproduced well erosion was predicted with sufficient skill bss 0 60 to meet practical engineering requirements concerned with predicting storm impacts and threshold wave and water level conditions for gravel barrier overwashing

on the profile evolution of three artificial pebble beaches at marina di pisa italy abstract in this paper the profiles of three artificial coarse grained beaches located at marina di pisa tuscany italy were monitored from april 2008 to may 2009 in order to define the response of the beaches to major storms that occurred during the study two beaches are similar the third differs in length and in the level of protection being less than half the length of the others and devoid of an offshore submerged breakwater the work was achieved by means of accurate topographic surveys intended to reconstruct the beach profile from the backshore up to the foreshore upper shoreface transition step the surveys were performed with an rtk gps instrument which provided extremely precise recording of the beach the most significant features of the beaches were tracked during each survey in particular the landward foot of the storm berm the crest of the storm berm the coastline and the step crest were monitored five cross shore transects were traced on each beach along these transects any meaningful slope change was recorded to obtain accurate sections of the beach the field datasets were processed with autocad software to compare the beach profile evolution during the year long research the results showed a comparable evolution of the twin beaches the resulting storm berm retreat of about 15 to 19 m is a remarkable feature considering the coarse grain size and the offshore protection due to the absence of the breakwater the third beach was characterized by even higher values of recession over 20 m and showed hints of wave reflection related processes after the huge steep storm berm had been formed and grown after the high energy events these processes were not as evident on the twin beaches these results underline the different response of three similar protection schemes and the importance that frequent monitoring of the beach morphology holds when it comes to coastal management issues

direct measurements of bed stress under swash in the field 1 utilizing flush mounted hot film anemometry the bed stress under swash was measured directly in a field experiment conducted on barret beach fire island new york the theory development and calibration of the instrument package are discussed and results from the field experiment are presented examples of bed stress time series throughout a swash cycle are presented and an ensemble averaged swash bed stress cycle is calculated strong asymmetry is observed between the uprush and backwash phases of the swash flow the maximum bed shear stress exerted by the uprush is approximately double that of the backwash while the duration of the backwash is 135 greater than that of the uprush friction coefficients in the swash zone are observed to be similar in magnitude to those from steady flow with the mean observed friction coefficient equal to 0 0037 swash friction coefficients derived from the current measurements exhibit a reynolds number dependence similar to that observed for other flows a systematic difference between coefficients for uprush and backwash is suggested

an analysis of the cross shore beach morphodynamics of a sandy and a composite gravel beach in this paper beach profile surveys acquired over more than a decade at a sandy beach narrabeen beach new south wales australia and a composite sand gravel beach milford on sea christchurch bay uk are analysed to compare and contrast cross shore morphodynamics of the two beach types the different behavioural characteristics of the two beach types at decadal inter annual and intra annual time scales are investigated comparisons of beach profiles with dean s equilibrium profile and vellinga s erosion profile show that the dean s profile satisfactorily represents the time mean profiles of both beach types statistical and empirical orthogonal function eof analyses confirm the generally accepted model that the inter tidal zone is the most morphodynamically active region on a sandy beach whereas the swash zone is the most dynamic region on a mixed sand gravel beach the results also imply that during storms composite sand gravel beaches may become unstable due to cutback of the upper beach while sandy beaches are more likely to be unstable as a result of beach lowering due to sediment transport from the inter tidal zone to the sub tidal zone during storms eof results also show that milford on sea beach is in a state of steady recession while the narrabeen beach shows a cyclic erosion accretion variability a multivariate technique canonical correlation analysis cca shows that on the composite beach a strong correlation exists between incident wave steepness and profile response which could be attributed to the unsaturated surf zone whereas on the sandy beach any correlation is much less evident

dating of the ameralik dyke swarms of the nuuk district southern west greenland mafic intrusion events starting from c 3510 ma this paper presents shrimp u pb zircon dating on four meso to palaeoarchaean amphibolite facies ameralik dykes of differing compositions scattered throughout the palaeoarchaean 3850 3600 ma amphibolite granulite facies itsaq gneiss complex in the nuuk district southern west greenland in the north of the complex near the isua supracrustal belt an east west oriented 50 m thick metanoritic dyke with abundant relicts of original opx plag ol igneous mineralogy gave an age of 3512 7 ma interpreted as the intrusion age in general agreement with previous isotope dilution thermal ionization mass spectrometry data in the same area the best estimate for the intrusion age of a metadolerite dyke with the same orientation and similar degree of preservation is 3265 15 ma at the mouth of ameralik fjord 150 km to the sw a large noritic ameralik dyke the ugpik metadolerite was largely recrystallized to amphibolite in the later archaean relict magmatic zircon in this body implies an intrusion age of 3453 16 ma in itilleq fjord 60 km to the east of the ugpik metadolerite a dioritic component of a composite dioritic gabbroic intrusion cutting older more deformed ameralik dykes has yielded an age of 3257 14 ma for the time of intrusion these new sensitive high resolution ion microprobe dates on magmatic crystallization support previous field observations that the ameralik dykes consist of several unrelated sets of dykes different in age by up to 250 ma the magmatic zircons in three of the dykes have 2700 2500 ma overgrowths interpreted to have grown during late archaean amphibolite facies tectonothermal events in the region the original name ameralik dykes might propagate confusion that all such bodies can be regarded as the same age thus we recommend retaining the original definition of the ameralik dykes but using the term ameralik dyke swarms to emphasize that unrelated intrusions of more than one age are present

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

deformation features and critical field relationships of early archaean rocks akilia southwest greenland abstract lithologically varied early archaean rocks on the island of akilia godthabsfjord southwest greenland include a quartz pyroxene unit that has been proposed as a bif carbon isotope data from graphite particles in apatites within this unit have further been proposed to represent evidence for earth s earliest life we present field observations which demonstrate that all lithologies on sw akilia have been intensely deformed during both early and late archaean high grade metamorphism in our view this deformation precludes unambiguous demonstration of purported sedimentary features in the quartz pyroxene rock a unit which we interpret as the result of metasomatic metamorphic and tectonic reworking of a mafic ultramafic protolith such an origin is completely incompatible with the quartz pyroxene rock hosting any signs of early biogenic activity we also reappraise contact relationships between amitsoq gneisses and mafic ultramafic rocks and can find no convincing evidence for the existence of intrusive relationships that have been central to geochronological interpretations on akilia

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

determination of wave shoreline dynamics on a macrotidal gravel beach using canonical correlation analysis abstract this paper describes the application of canonical correlation analysis cca to derive forcing response relations between the wave climate and shoreline position on a macrotidal gravel barrier located in the southwest of the u k and to develop a tool to determine shoreline positions from wave records the data sequences comprise wave climate recorded by a nearshore directional wave buoy and video derived shorelines over a time span of one year and a half the hydrodynamic conditions are used to determine the probability density function of wave heights and alongshore energy fluxes these are then related to shoreline change through a cca analysis the cca analysis identifies patterns of behaviour of the wave conditions and the shoreline position and the relation between both patterns is found to provide useful information about the beach response to wave action the analysis shows that the movement of sediment is greater at the southern end of the study area and that there is an immediate shoreline response to the wave action in the case of coastal management it is more often the case that wave forecasts are available on a routine basis the ability of the cca to provide useful estimates of shorelines from wave conditions was tested by using measured waves to calculate the corresponding shoreline position from additional data at the end of the sequences shoreline positions determined with the cca agreed well with the measured ones thus the cca is found to be a useful tool to determine unknown shoreline positions and support effective coastal management if good quality hydrodynamic and morphological data are available to input into the initial set up of the technique

longshore transport of cobbles on a mixed sand and gravel beach southern hawke bay new zealand abstract few large scale field measurements of longshore sediment transport have been undertaken on beaches composed of coarse sediments in part owing to difficulties associated with measurement in energetic swash zones in which large clasts are moving here we present results from a field experiment in which passive integrated transponder tags were used to investigate patterns of cobble transport over 8 months on a mixed sand and gravel beach on the east coast of new zealand the study objectives were to document rates of alongshore transport and measure rates of cobble abrasion under field conditions cobble recovery rates were highly variable over the study period with 30 60 recovery at site 1 compared to much lower 0 20 recovery rates at sites 2 and 3 consistent uni directional patterns of net alongshore sediment transport were observed the median cobble transport rate was approximately 500 m over 207 days indicating long term net northward transport rates on the order of 2 2 5 m day results highlight a number of factors in addition to longshore energy flux that are important for understanding the observed patterns in particular across shore sediment transport during storms may have been smaller at site 1 than the other sites owing to lesser wave exposure this is partly responsible for higher cobble recovery rates at this site and also an increased amount of time during which cobbles were able to be transported alongshore on the lower beachface unique to this study results demonstrate the use of pit tags to provide direct measurement of cobble abrasion under natural processes repeat weight measurement on individually tracked cobbles show that after 207 days the median loss was 11 3 g or 1 8 of total weight there was a general trend of abrasion increasing with net transport distance but longshore cobble movement was highly variable ranging from 130 to 2500 m

estimating swash zone friction coefficients on a sandy beach abstract video based swash motions from three studies on two separate beaches were analyzed with respect to theoretical swash trajectories assuming plane beach ballistic motions under quadratic friction friction coefficient values for both the uprush and backwash were estimated by comparing measured swash space time trajectories to these theoretical expectations given an initial velocity and beach slope observations were made spanning high tides and in one case during a light rain analysis of over 4500 individual swash events showed that the uprush friction coefficient was nearly constant during all three studies with a mean value of roughly 0 007 and showed no trends over a tidal cycle in contrast backwash friction coefficient values varied over the tidal cycles ranging between 0 01 and 0 07 with minimum values corresponding to the highest tides although these values are close to the theoretical estimates based on a law of the wall formulation and values commonly referenced in the literature these observations show a consistent tendency for backwash friction estimates to greatly exceed uprush friction estimates the disparity between uprush and backwash friction coefficients can be partially attributed to the exclusion of a pressure gradient term in the ballistic model however results indicate that backwash friction coefficients adjusted to account for this effect may be three times larger than the uprush friction values during lower tides this tidal dependence for backwash friction coefficients is attributed to a complex interaction between swash infiltration and entrained sediment loads these findings imply that friction estimates necessary for sediment transport calculations and hydrodynamic predictions based solely on grain roughness may not be correct for backwash flows

observations of morphological change and sediment transport on a steep gravel beach abstract observations of morphological change and swash sediment loads concurrent with measurements of water level waves and currents were obtained during a spring to spring tidal cycle on a steep macrotidal gravel beach in southwest england the wave conditions experienced during the field experiment were relatively calm and the significant inshore wave height and period averaged 0 4 m and 6 s respectively incident frequency water motions dominated the hydrodynamics and the phasing between water surface elevation and cross shore and alongshore currents was inconsistent with standing edge wave motion morphological change was directly related to maxima in shoreline elevation and four modes of berm adjustment identified regression and rollover in response to falling and rising water levels respectively and removal and reformation during and after storms respectively swash processes transported substantial amounts of sediment at rates comparable to sand beaches and the net transport under modal wave conditions was estimated to be 1 kg per swash onshore per unit metre beach width steep hydrodynamic gradients induced by the abrupt slope breaks of the step and berm are one of the main causes of the large morphological variability characteristic of gravel beaches

experimental studies of ree fractionation during water mineral interactions ree release rates during apatite dissolution from ph 2 8 to 9 2 rare earth elements ree release rates were measured during the open system dissolution of natural apatite at 25 c 2 8 ph 9 2 and at ionic strengths ranging from 0 001 to 0 02 mol kg all inlet solutions were ca ree and p free in agreement with previous studies apatite dissolution rates determined from outlet solution ca concentrations decrease monotonically with increasing ph outlet solution molar ree ca ratios differ from that of the dissolving apatite during the experiments this behaviour is interpreted to stem from dissolution or precipitation of minor quantities of rhabdophane ree po4 nh2o this interpretation is supported by solute speciation calculations which indicate that ree are retained in the solid phase when the outlet fluids are supersaturated with respect to nd rhabdophane ksp 10 24 5 0 5 but preferentially released when the outlet fluids are undersaturated with respect to nd rhabdophane the relative concentrations of the ree in the outlet solutions suggest that the secondary rhabdophane is slightly enriched in light ree ce to eu the results of this study suggest that rhabdophane dissolution and precipitation during apatite fluid interaction plays a major role in controlling surface and ground water ree signatures

observations and predictions of fluid velocities in the surf and swash zones 1 surfzone and swashzone water level fluctuations and cross shore fluid velocities observed at seven cross shore locations for 139 51 min periods on a low sloped fine grained sandy beach are shown to be modeled well by the depth averaged nonlinear shallow water equations the model initialized with observations about 150 m from the shoreline in 300 cm water depth accurately predicts the observed decrease in sea swell wave heights and orbital velocities with decreasing water depth across the surf zone and the observed maxima in infragravity orbital velocities and offshore directed mean flows near the outer edge of the swash zone in the surf zone both the observed and predicted velocity fluctuations are dominated by sawtoothed shaped pitched forward asymmetrical sea swell waves in the swash zone infragravity waves contribute substantially to the total velocity variance and asymmetry shoreward of the outer swash zone observed and predicted total and infragravity velocity asymmetry decrease onshore changing sign from positive to negative in the upper swash

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

fine grained agglutinated elongate columnar stromatolites tieling formation ca 1420 ma north china the mesoproterozoic tieling formation near jixian northern china contains thick beds of vertically branched laterally elongate columnar stromatolites carbonate mud is the primary component of both the stromatolites and their intervening matrix its abundance is attributed to water column whiting precipitation stimulated by cyanobacterial photosynthesis neomorphic microspar gives the stromatolites a streaky microfabric and small mud flakes are common in the matrix the columns consist of low relief mainly non enveloping laminae that show erosive truncation and well defined repetitive lamination in plan view the columns form disjunct elongate ridges 10 cm wide separated by narrow matrix filled runnels the stromatolite surfaces were initially cohesive rather than rigid and prone to scour and are interpreted as current aligned microbial mats that trapped carbonate mud the pervasive ridge runnel system suggests scale dependent biophysical feedback between i carbonate mud supply ii current duration strength and direction and iii growth and trapping by prolific mat growth together these factors determined the size morphology and arrangement of the stromatolite columns and their laminae as well as their branching patterns alignment and ridge runnel spacing ridge runnel surfaces resemble ripple mark patterns but whether currents were parallel and or normal to stromatolite alignment remains unclear the formation and preservation of tieling columns required plentiful supply of carbonate mud mat building microbes well adapted to cope with this abundant sediment and absence of both significant early lithification and bioturbation these factors were time limited and tieling stromatolites closely resemble coeval examples in the belt purcell supergroup of laurentia the dynamic interactions between mat growth currents and sediment supply that determined the shape of tieling columns contributed to the morphotypical diversity that characterizes mid late proterozoic branched stromatolites this article is protected by copyright all rights reserved

observation of undertow and turbulence in a laboratory surf zone abstract undertow and turbulence in the surf zone have been studied in a wave flume for a spilling breaker and a plunging breaker fluid velocities across a 1 on 35 sloped false bottom were measured using a fiber optic laser doppler anemometer and wave decay and set up were measured using a capacitance wave gage the characteristics of mean flow and turbulence in spilling versus plunging breakers were studied the mean flow is the organized wave induced flow defined as the phase average of the instantaneous velocity while the turbulence is taken as the deviations from the phase average it was found that under the plunging breaker turbulence levels are much higher and vertical variations of undertow and turbulence intensity are much smaller in comparison with the spilling breaker it was also found that turbulent kinetic energy is transported seaward under the spilling breaker and landward under the plunging breaker by the mean flow the study indicates that there are fundamental differences in the dynamics of turbulence between spilling and plunging breakers which can be related to the processes of wave breaking and turbulence production it is suggested that the types of beach profile produced by storm and swell waves may be the results of different relationships between mean flow and turbulence in these waves

the akilia controversy field structural and geochronological evidence questions interpretations of 3 8 ga life in sw greenland abstract field relations structure and geochronology demonstrate that controversial rocks on akilia sw greenland cannot host evidence of earth9s oldest life mafic ultramafic gneiss that contains a layer of quartz amphibole pyroxene gneiss a few metres thick with purported biogenic graphite is not cross cut by the protoliths of 3 82 3 65 ga tonalitic gneiss the contact between these gneisses is tectonic so their relative ages are unknown multiple episodes of intrusion and deformation in the tonalitic gneiss preceded the earliest deformation fabrics and structures seen in the mafic ultramafic gneiss although previously interpreted as a volcano sedimentary stratigraphy the mafic ultramafic gneiss displays no evidence of such an origin and could be partly or wholly derived from igneous intrusions existing geochronology indicates that the mafic ultramafic and qtz am px gneisses have ages c 2 68 ga during late archaean high grade events that complicate any protolith interpretation u pb dating of apatite from a variety of rocks on akilia shows that this mineral crystallized or possibly recrystallized at c 1 75 ga and it thus provides no indication of an early archaean age for any associated graphite regardless of whether or not the latter is biogenic supplementary material ion microprobe u pb analytical methods and isotope data tables are available at http www geolsoc org uk sup18333

diagnostic investigation of impulsive pressures induced by plunging breakers impinging on gravel beaches abstract this paper presents an integrated investigation of physical processes generating impulsive pressures under the action of plunging breakers impinging on gravel beaches this work is an extension of a recent investigation which suggested that wave impacts from plunging breakers acting on gravel beaches may be a key mechanism to enhance sediment mobilisation in particular comparisons of full scale laboratory measurements against model results from a well validated phase depth resolving numerical model based on the reynolds averaged navier stokes rans equations are presented this represents the first attempt at comparison with such a tool against observed hydrodynamics on steep slope 1 8 gravel beaches at prototype scale in order to understand how impulsive pressures are generated under plunging waves the numerical model is used to carry out a detailed investigation to examine the role of each of the acceleration terms in the momentum balance consistent with prior studies numerical results show that under plunging breakers the local acceleration u t alone cannot be used as a proxy for pressure gradients however the contribution of the third term w u z of total acceleration is recognized for the first time and indicates that this term has an important role in both the induced pressure gradient and sediment mobilisation as induced by this particular type of breaking furthermore results suggest that a parameterisation of the pressure gradient in terms of u t u u x may not suffice when dealing with plunging breakers and hence there is a lack of a suitable parameterisation of this process in the present literature thus for different types of breaking it may be necessary to consider a different characterisation of the pressure gradient toward the parameterisation of sediment transport inside the surf zone

origin of life from apatite dating mojzsis et al 1 2 reported the carbon isotope composition of carbonaceous inclusions in grains of apatite from sediment sequences of akilia island southwest greenland that are more than 3 850 million years myr old the 13c values measured by mojzsis et al 1 led them to conclude that these carbonaceous materials are evidence of early life 3 850 myr ago but if other isotopes u pb and pb pb are used the apatites are estimated at just 1 504 336 2 and 1 459 160 2 myr old this value is consistent with measurements of 1 600 1 700 myr for rb sr mineral isochrons on biotites3 and 1 670 myr for k ar muscovite4 from amitsog gneiss in the region we conclude that about 1 500 myr ago these apatites in akilia island experienced a metamorphic event of about 600 c estimated by the closure temperature of the u pb system5 6

numerical experiments on interactions between wave motion and variable density coastal aquifers a comprehensive two dimensional cross shore process based numerical model of nearshore hydrodynamics based on the navier stokes equations k e turbulence closure and the volume of fluid method beach morphology and variable density groundwater flow seawat 2000 was developed this model which was applied at the field scale relaxes simplifications in existing models that do not include such detailed mechanistic descriptions numerical experiments were conducted to investigate the effects of varying aquifer beach and wave characteristics e g inland groundwater head sand grain size different wave heights and periods on the coupled system spilling and plunging breakers on dissipative and intermediate beaches were simulated for a given set of boundary conditions the model was run for 1 y without the hydrodynamic sub model to achieve a realistic salt freshwater interface then the hydrodynamic component was run for 15 min and the model results analyzed the main features considered were groundwater circulation saltwater wedge position in exfiltration across the beach face and beach morphology the predictions of the numerical model agree well with existing understanding and experimental measurements for an inland watertable that is lower than the still water level swl such that the groundwater flow is mainly landward on both coarse and fine sand beaches the addition of wave motion moves the saltwater wedge further landward for an inland watertable that is higher than the swl the opposite behavior occurred the numerical experiments showed that more sediment transport takes place on intermediate beaches than on dissipative beaches in addition beach profile variations are greater under plunging breakers while coarse sand beaches are steeper than fine sand beaches for the same wave conditions there is a strong correlation between in exfiltration and beach face deposition erosion for the coarse beaches while in exfiltration has a slight effect on sediment transport for fine beaches the model is capable of simulating the short term evolution of foreshore profile changes and beach watertable and saltwater wedge movement due to interactions between wave motion and coastal groundwater

modelling storm hydrodynamics on gravel beaches with xbeach g abstract in this paper we present a process based numerical model for the prediction of storm hydrodynamics and hydrology on gravel beaches the model comprises an extension of an existing open source storm impact model for sandy coasts xbeach through the application of 1 a non hydrostatic pressure correction term that allows wave by wave modelling of the surface elevation and depth averaged flow and 2 a groundwater model that allows infiltration and exfiltration through the permeable gravel bed to be simulated and is referred to as xbeach g although the model contains validated sediment transport relations for sandy environments transport relations for gravel in the model are currently under development and unvalidated consequently all simulations in this paper are carried out without morphodynamic feedback modelled hydrodynamics are validated using data collected during a large scale physical model experiment and detailed in situ field data collected at loe bar cornwall uk as well as remote sensed data collected at four gravel beach locations along the uk coast during the 2012 2013 storm season validation results show that the model has good skill in predicting wave transformation overall sci 0 14 0 21 run up levels sci

modelling gravel beach dynamics with xbeach abstract numerical cross shore profile evolution models have been good at predicting beach erosion during storm conditions but have difficulty in predicting the accretion of the beach during calm periods this paper describes the progress made in modifying and applying the public domain xbeach code to the prediction and explanation of the observed behaviour of coarse grained beaches in the laboratory and the field under accretive conditions the paper outlines in details the changes made to the original code version 12 including the introduction of a new morphological module based upon soulsby s sediment transport equation for waves and currents and the incorporation of packwood s infiltration approach in the unsaturated area of the swash region the competence of this modified model during calm conditions for describing the steepening of the profile and the growth of the beach berm is demonstrated preliminary results on the behaviour of the beach subject to both waves and tides are presented good agreement is found between the model simulations and large scale laboratory measurements as well as field observations from a composite beach in the uk the reasons for the model s capabilities are discussed

ion microprobe pb pb dating of carbonado polycrystalline diamond abstract we report in situ ion microprobe pb pb dating of quartz rutile and clay mineral inclusions and matrix part of polycrystalline diamonds carbonado derived from a proterozoic conglomerate in diamond bearing deposit of minas gerais in brazil together with u pb ages of zircons also extracted from the deposit thirty four spots on seven quartz grains located in the cavity of the gm01 carbonado yield 207pb 206pb isochron age of 3247 800 ma 2 mswd 0 75 and six spots on three rutile inclusions give the age of 3916 1300 ma 2 mswd 0 092 seven spots on three clay mineral inclusions of the do3 carbonado show common lead compositions while four spots on matrix define 207pb 206pb isochron age of 3811 1800 ma 2 mswd 0 012 seventy six spots on seventy zircon grains derived from the same conglomerate show three major u pb concordant ages of 2151 17 ma 2692 20 ma and 2931 22 ma with two concordant zircon outliers of 1726 58 ma and 3599 12 ma the youngest age is consistent with the formation age of 1750 1700 ma in the proterozoic conglomerate estimated by other workers the 3 6 ga zircon is the oldest record in the south american platform it may be detrital in origin and reflect the remnant of an archean craton the pb pb age of quartz and rutile inclusions in gm01 carbonado and that of do3 carbonado matrix are 3315 720 ma and 3811 1800 ma the matrix age is consistent with pb pb age of 2 6 3 8 ga of central african carbonados in the literature suggesting a close genetic relationship between brazilian and african carbonados

a rare earth element study of complex zircons from early archaean amitsoq gneisses godthabsfjord south west greenland we present high spatial resolution ion microprobe rare earth element ree data for discrete growth phases of complex polyphase zircons from early archaean amitsoq gneisses outer godthabsfjord sw greenland in matsuda diagrams the two major growth phases 3 8 ga cores and ca 3 65 ga rims have steep positive slopes from la to lu prominent positive ce anomalies and negative eu anomalies that are consistent with growth in a melt exceptions to this are non cathodolurnmescent zircon developed between the cores and rims sometimes truncating zoning in the cores and late archaean prismatic tip overgrowths both of which exhibit flatter light ree lree patterns and have small or no eu anomaly which we interpret as the result of metamorphism and or small degree isolated partial melting our data support previous interpretations that the ca 3 65 ga zircon phase was generated in a melt with the 3 8 ga phase representing either original protolith zircons in a large degree partial melt or inherited zircons in an introduced magma regardless which of these two interpretations is correct for these and similar rocks in the outer godthabsfjord the 3 65 ga event will have profoundly affected isotopic systems and obscured beyond recognition any earlier igneous features such as cross cutting relationships which may only be assigned a minimum 3 65 ga age c 2003 elsevier science b v all rights reserved

transport trajectories of smart pebbles on an artificial coarse grained beach at marina di pisa italy implications for beach morphodynamics abstract in this paper transport pathways for coarse sediments were studied on an artificial pebble beach located at marina di pisa tuscany italy radio frequency identification rfid technology was used to trace the pebbles the rfid technique is an inexpensive and reliable methodology that is used to address sediment displacement along the coastline the use of low frequency radio signals 125 khz enabled the detection of the marked pebbles within a range of 40 cm on the underwater and subaerial portions of the beach about one hundred pebbles were sampled on the beach and paired with passive transponders the tracers were released along a series of cross shore transects march 2009 the pebbles were injected on the fair weather berm on the swash zone and on the step crest along each transect the recovery campaign was carried out in may 2009 fifty three pebbles were detected this number is rather high given the intensity of the three storms that hit the coast during the period of the experiment and the significant reworking that this beach is subjected to even under fair weather conditions the analysis of the tracer pathways highlighted twofold convergent longshore movement on the beach the trajectories indicated that the longshore movement dominated the cross shore movement but there was no prevailing transport direction to explore the morphology of the sea bottom fronting the beach a topographic survey was carried out using an echo sounder the survey showed the presence of two distinct shoals 20 m off the coastline that are responsible for the resulting coarse sediment transport these results confirm that even mild sea bottom irregularities may significantly affect sediment transport dynamics along a beach suggesting that accurate planning for defense schemes such as artificial coarse replenishment must begin with an in depth knowledge of the morphology of the sea floor such information may increase the durability and or the efficiency of the intervention

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

the effects of storm clustering on beach profile variability abstract impacts of storms in reshaping coastlines are well known also the far greater impact of clusters of storms where storms occur at close succession has been noted in a number of previous studies in this paper we analyse and discuss the storm wave climate and the beach profile response to clusters of storms at narrabeen beach new south wales australia narrabeen beach is subjected to frequent storms all year round and the beach undergoes substantial variability as a result the impact of storm clusters with closely spaced individual storms reaching the beach is investigated by combining historic measurements of beach profile surveys and numerical modelling of storm induced beach change our analysis of storm power index of storm clusters and its correlation with the change in beach width reveals that the strengths of single storms in a storm cluster alone are not the reason for beach change but time interval between successive storms and the post storm recovery speed of the beach concerned also play important roles we have quantified and compared beach erosion return levels resulting from single storms and storm clusters it was found that beach erosion volumes resulting from storm clusters with two or more storms resemble potential beach erosion volumes induced by single storms of far higher return periods

early trace of life from 3 95 ga sedimentary rocks in labrador canada the authors provide evidence for the existence of life on earth in the earliest known sedimentary rocks and suggest that the presence of organic carbon and low stable isotope values of graphite from sedimentary rocks in labrador pushes back the existence of organic life to beyond 3 95 billion years the beginning of organic life on earth is being pushed back by evidence from the earliest known sedimentary rocks tsuyoshi komiya and colleagues argue that the presence of organic carbon and stable isotope excursions in graphite from sedimentary rocks in labrador canada pushes back the existence of organic life to more than 3 95 billion years ago together with recent work showing evidence for a diverse range of living organisms around 3 7 billion years ago including stromatolites living in sunlit surface waters and bacteria living in deep sea hydrothermal vents the work shows that life has been around almost as long as there has been a planet that it can call home the vestiges of life in eoarchean rocks have the potential to elucidate the origin of life however gathering evidence from many terrains is not always possible1 2 3 and biogenic graphite has thus far been found only in the 3 7 3 8 ga gigayears ago isua supracrustal belt4 5 6 7 here we present the total organic carbon contents and carbon isotope values of graphite 13corg and carbonate 13ccarb in the oldest metasedimentary rocks from northern labrador8 9 some pelitic rocks have low 13corg values of 28 2 comparable to the lowest value in younger rocks the consistency between crystallization temperatures of the graphite and metamorphic temperature of the host rocks establishes that the graphite does not originate from later contamination a clear correlation between the 13corg values and metamorphic grade indicates that variations in the 13corg values are due to metamorphism and that the pre metamorphic value was lower than the minimum value we concluded that the large fractionation between the 13ccarb and 13corg values up to 25 indicates the oldest evidence of organisms greater than 3 95 ga the discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves and will provide insight into early life not only on earth but also on other planets

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

a partial cell technique for modeling the morphological change and scour abstract a novel partial cell technique applied on structured grids is developed to track the deformation of water soil interface associated with beach morphological change and toe scour in front of coastal structures it allows the use of the same orthogonal structured grids for morphological sediment transport and hydrodynamic models therefore has the advantage of consuming less cpu and without the need to adapt grids to the evolving beach morphology an improved sand slide model with better mass conservation is introduced to resolve the avalanche behaviour of the sediment motion the rans vof hydrodynamic model has been extended to cope with complex bathymetry the newly developed numerical model suite coupling the rans vof model a bedload sediment transport model and a morphological model using the partial cell technique are validated against the analytical solutions and laboratory measurements for different incoming wave conditions local water depths and bottom slopes this study reveals the key processes that govern the behaviour of beach morphology change in front of a vertical coastal structure during storms the model data comparisons demonstrate the robustness of partial cell technique to capture the movement of the water soil interface

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

metamorphic alteration mineral paragenesis and geochemical re equilibration of early archean quartz amphibole pyroxene gneiss from akilia southwest greenland quartz amphibole pyroxene gneiss from the island of akilia southwest greenland has been claimed to contain the earliest traces of life on earth in the form of biogenic carbonaceous matter encapsulated as inclusions in apatite crystals various lines of evidence including petrography geochronology field relations and geochemistry have however been presented that challenge this interpretation textural relationships and geochemical signatures in this controversial gneiss presented here manifest a complex spatially variable metamorphic history that includes granulite and amphibolite facies overprints and metasomatism a peak metamorphic granulite facies quartz orthopyroxene clinopyroxene amphibole magnetite assemblage is preserved in only a few centimeter scale layers within the 5 m thick quartz amphibole pyroxene gneiss unit calcite veinlets that appear to postdate the peak metamorphism occur in pyroxene the quartz amphibole pyroxene gneiss unit has subsequently experienced isochemical except hydration amphibolite facies alteration during which pyroxenes were retrogressed to amphiboles and magnetite and calcite was consumed parts of the quartz amphibole pyroxene gneiss that contain texturally late hornblende have experienced metasomatic alteration by al carrying fluids these fluids controlled the alteration of pyroxenes and amphiboles to hornblende and modified the trace element composition by remobilizing lree and eu apatite has variable ree composition and 87sr 86sr in the quartz amphibole pyroxene gneiss but on the local scale cm is in equilibrium with co existing silicates effective recrystallization of apatite crystals as well as co existing silicates during several stages of the metamorphic history makes the intact preservation of diagenetic apatite with encapsulated primary carbonaceous matter implausible hence it is highly unlikely that akilia apatite could serve as repository of the earliest traces of life on earth

a numerical empirical approach for evaluating morphodynamic processes on gravel and mixed sand gravel beaches abstract pedrozo acuna et al pedrozo acuna a simmonds d j otta a k and chadwick a j 2006 on the cross shore profile change of gravel beaches coastal engineering 53 4 335 347 presented a numerical empirical investigation of the processes that control sediment transport in the swash zone on steep gravel beaches this was based on a sensitivity analysis of a sediment transport profile model driven by a highly non linear boussinesq model lynett p j wu t r and liu l f p 2002 modelling wave run up with depth integrated equations coastal engineering 46 89 107 which was compared to near full scale measurements performed in the gwk flume in hanover in this paper we have extended our analysis to compare these earlier results with those relating to a mixed sediment gravel and sand beach the parametric sensitivity analysis also incorporates a discussion of the effects of acceleration about which there is much debate the sensitivity analysis suggests that fluid acceleration can contribute to the onshore movement of sediment that causes steepening of initially flat beach faces composed of coarse sediment however acceleration alone cannot be the cause of the observed berm growth during the gwk tests instead a complex balance of processes is responsible for the profile evolution of coarse grained beaches with no single dominant process

observations of swash zone velocities a note on friction coefficients 1 vertical flow structure and turbulent dissipation in the swash zone are estimated using cross shore fluid velocities observed on a low sloped fine grained sandy beach raubenheimer 2002 with two stacks of three current meters located about 2 5 and 8 cm above the bed the observations are consistent with an approximately logarithmic vertical decay of wave orbital velocities within 5 cm of the bed the associated friction coefficients are similar in both the uprush and downrush as in previous laboratory results turbulent dissipation rates estimated from velocity spectra increase with decreasing water depth from o 400 cm2 s3 in the inner surf zone to o 1000 cm2 s3 in the swash zone friction coefficients in the swash interior estimated with the logarithmic model and independently estimated by assuming that turbulent dissipation is balanced by production from vertical shear of the local mean flow and from wave breaking are between 0 02 and 0 06 these values are similar to the range of friction coefficients 0 02 0 05 recently estimated on impermeable rough nonerodible laboratory beaches and to the range of friction coefficients 0 01 0 03 previously estimated from field observations of the motion of the shoreward edge of the swash run up

large scale experiments on gravel and mixed beaches experimental procedure data documentation and initial results abstract this paper provides information on the experimental set up data collection methods and results to date for the project large scale modelling of coarse grained beaches undertaken at the large wave channel gwk of fzk in hannover by an international group of researchers in spring 2002 the main objective of the experiments was to provide full scale measurements of cross shore processes on gravel and mixed beaches for the verification and further development of cross shore numerical models of gravel and mixed sediment beaches identical random and regular wave tests were undertaken for a gravel beach and a mixed sand gravel beach set up in the flume measurements included profile development water surface elevation along the flume internal pressures in the swash zone piezometric head levels within the beach run up flow velocities in the surf zone and sediment size distributions the purpose of the paper is to present to the scientific community the experimental procedure a summary of the data collected some initial results as well as a brief outline of the on going research being carried out with the data by different research groups the experimental data is available to all the scientific community following submission of a statement of objectives specification of data requirements and an agreement to abide with the gwk and eu protocols

turbulence based measurements of wave friction factors under irregular waves on a gravel bed very few studies have quantified the wave friction factor fw for coarse sediments at field scale to address this shortcoming high frequency measurements of turbulence obtained within the boundary layer of irregular waves over gravel in the delta flume have been used to calculate values of fw using different evaluation methods in the field scale laboratory experiments reported here three velocimeters were deployed on the seaward side of a 4 m high 5 m wide and 55 m long gravel barrier subject to a jonswap spectrum of waves with significant wave heights ranging from 0 8 m to 1 3 m and peak periods of 3 0 s to 10 s and offshore water depths ranging from 1 75 m to 3 75 m the deployment area was essentially flat with little or no predicted or observed sediment movement under the wave conditions investigated the turbulent kinetic energy method was found to be the most suitable approach for calculating the bed shear stress which can be related to fw wave friction factor values under the conditions tested here fell in the range 0 01 and 0 27 although fw predicted by an existing equation agrees well with the mean measured fw value the application of a new predictor for fw is recommended for improved parameterisation of skin friction over the range of relative roughness values encountered in this study this approach combines the wave reynolds number wave steepness and relative depth to provide a simple expression to assist assessments of coarse sediment transport by waves for uses within a range of practical engineering applications

uranium lead systematics of low ti basaltic meteorite dhofar 287a affinity to apollo 15 green glasses article i nfo dhofar 287 is a lunar meteorite found in oman in 2001 which consists of a major portion 95 of low ti mare basalt dho 287a and a minor attached part 5 of regolith breccia dho 287b here we report the u pb systematics of dho 287a using data collected with a sensitive high resolution ion microprobe shrimp in situ analyses of five merrillite and three apatite grains which are resistant to secondary petrologic events resulted in a total pb u isochron age of 3 34 0 20 ga in 238 u 206 pb 207 pb 206 pb 204 pb 206 pb 3 d space 95 confidence level the observed pb pb isochron of these eight phosphates coupled with four plagioclase grains alsoyieldeda 207 pb 206 pbageof3 35 0 13ga thisformationage whenconsideredasthecrystallizationageof

linkages between sediment composition wave climate and beach profile variability at multiple timescales the paper analyses compares and contrasts cross shore morphodynamic behaviour of four diverse beaches that have very different regional settings wave climates and sediment characteristics with the aid of rarely available long term measurements of beach profiles and incident waves the beaches investigated are narrabeen beach new south wales australia milford on sea beach christchurch bay uk hasaki coast ibaraki prefecture japan and joetsu ogata coast niigata prefecture japan a statistical analysis equilibrium beach profile analysis and empirical orthogonal function analysis are used to investigate compare and contrast spatial and temporal variability of cross shore beach profiles of the selected beaches at short medium and long term timescales all beaches show evidence of multi timescale morphodynamic change narrabeen beach profile has the highest sensitivity to local weather patterns milford on sea joetsu ogata and hasaki profiles are sensitive to seasonal variation of the wave climate however they also show some correlations with regional climate variabilities the nature of sediment exchange across the profile which contributes to profile shape change with time is found to be related to sediment characteristics across the profile at milford on sea and joetsu ogata both of which have composite profiles sediment exchange between the upper beach and the inter tidal zone dominates profile change irrespective of the distinct differences in sediment composition found in the two beaches on the other hand in narrabeen and hasaki where beach sediment comprises medium to find sand sediment exchange and hence profile change occur mainly in intertidal and subtidal zones

high frequency in situ field measurements of morphological response on a fine gravel beach during energetic wave conditions this paper presents novel data collected over four weeks at loe bar a fine gravel barrier d50 3 5 mm exposed to energetic wave conditions hs10 2 4 m combined remote and in situ measurements were used to identify 3d morphological response profile change and runup behaviour during successive energetic periods hs 2 5 m small intertidal beach volume losses occurred under high steepness waves h0 l0 0 01 but in general the overall beach volume was remarkably stable in fact the greatest morphological response was evident not in cross shore sediment exchanges but due to the alongshore redistribution related to the three dimensional beach cusp system specifically during energetic wave conditions the cusp morphology underwent horn growth and embayment deepening leading to increased cusp definition an additional explanation for the stability of the cross shore beach profile is related to the development of the beach step during energetic conditions and long period waves significant deposition c 1 m occurred at the top of the beach step above the still water line the enhanced step provided a focal point for wave breaking considerably curtailing the swash motion and reducing the runup limit thereby providing protection to the upper beach this study provides much needed insight into complex morphological response and runup characteristics on gravel beaches fundamental for improved model development and leading towards better predictive tools

vestiges of life in the oldest greenland rocks a review of early archean geology in the godthabsfjord region and reappraisal of field evidence for 3850 ma life on akilia abstract the godthabsfjord region of west greenland contains the most extensive best exposed and most intensely studied early archean rocks on earth a geological record has been described of numerous magmatic events between 3 9 and 3 6 ga and evidence of life at 3 85 ga and 3 8 3 7 ga has been proposed from two widely separated localities some of these claims have recently been questioned and the nature of the best preserved remnants of the oldest known terrestrial volcanic and sedimentary rocks in the isua greenstone belt are being reinvestigated and substantially reinterpreted the first part of this article reviews the evolution of geological research and interpretations outlining the techniques by which the geological history has been determined and the ensuing controversies the second part re examines crucial field evidence upon which the antiquity of the oldest terrestrial life is claimed from the island of akilia

on the cross shore profile change of gravel beaches abstract this paper investigates cross shore profile changes of gravel beaches with particular regard to discussing the tendency for onshore transport and profile steepening in the swash zone the discussion includes observed morphological changes on a gravel beach from experimental investigations at the large wave flume gwk in hanover germany during the tests all the profile changes occurred in the swash zone resulting in erosion below the still water line swl and formation of a berm above the swl we investigate the profile evolution evaluating the transport rates from a bed load sediment transport formulation coupled with velocities calculated from a set of boussinesq equations that have been validated for its use in the surf and swash zones lynett p j wu t r and liu l f p 2002 modelling wave runup with depth integrated equations coastal engineering 46 89 107 otta a k and pedrozo acuna a 2004 swash boundary and cross shore variation of horizontal velocity on a slope in j m smith editor proceedings 29th international conference on coastal engineering world scientific lisbon portugal pp 1616 1628 we discuss the influence of bottom friction on the predicted profiles using reported friction factors from experimental studies it is shown that the use of a different friction factor within a realistic range in each phase of the swash uprush and backwash improves prediction of the beach profiles although quantitative agreement between the measured and computed profile evolutions is not satisfactory furthermore if the friction factor and the transport efficiency c of the sediment transport formulation are kept the same in the uprush and backwash accurate representation of profile evolution is not possible indeed the features of the predicted profiles are reversed however when the c parameter is set larger during the uprush than during the backwash the predicted profiles are closer to the observations differences between the predicted profiles from setting non identical c values and friction factors for the swash phase are believed to be linked to both the infiltration effects on the flow above the beachface and the more accelerated flow in the uprush

coupling cross shore and longshore sediment transport to model storm response along a mixed sand gravel coast under varying wave directions abstract this paper investigates the profile response of a mixed sand gravel deltaic beach playa granada southern spain forced by storm waves from varying directions beach morphology was monitored over a 36 day period with variable wave conditions and profile response was compared to model predictions using the xbeach g model and a longshore sediment transport lst formulation xbeach g was applied over 2 day periods of low energy south westerly sw storm and south easterly se storm conditions and was coupled to lst using a parametric approach which distributes the lst across the swash surf and nearshore zones a calibrated wave propagation model delft3d was used to obtain the inshore conditions required to drive the xbeach g model and the lst formulation the storm response is clearly influenced by the free board difference between the height of the berm and the total run up and is also strongly dependent on storm wave direction with the sw storm eroding the surveyed area while the se storm induced beach accretion model results indicate that xbeach g on its own is capable of adequately reproducing the response of the beach under sw storm conditions b s s 0 95 but not under se storms due to the higher lst gradients at the study location the combination of xbeach g and lst fits the measured profiles reasonably well under both sw b s s 0 96 and se b s s 0 88 storms inspiring confidence in the coupled model to predict the storm response under varying wave conditions the combined xbeach g lst model was applied to the entire 6 8 km deltaic coastline to investigate the impact of extreme sw and se storm events and the model results reiterate the importance of cross shore and longshore sediment transport in driving coastal storm response at this location the approach proposed in this work can be extended to other worldwide coasts highly influenced by both cross shore and longshore sediment transport such as beaches with different coastline orientations and or forced by varying wave directions

ion microprobe uranium thorium lead dating of shergotty phosphates we report ion microprobe u th pb dating of shergotty phosphates by means of the sensitive high resolution ion microprobe shrimp recently installed at hiroshima university japan ten analyses of whitlockite merrillite and three analyses of apatite indicate a 238u 206pb isochron age of 225 200 ma and a tera wasserburg concordia constrained linear three dimensional isochron age of 217 110 ma in the 238u 206pb 207pb 206pb204pb 206pb diagram these ages agree well with the 232th 208pb age of 189 83 ma which suggests that primary crystallization or a shock metamorphic event defined the formation age of the phosphate minerals the average of the later two ages 204 68 ma is consistent with the previously published rb sr age of 165 11 ma and u th pb age of 200 ma these show marginal agreement with the 40ar 39ar age of 254 10 ma but are significantly different from the sm nd age of 360 16 ma taking into account the closure temperature of the u pb system in apatite we suggest the time that shergotty last experienced a temperature of 900 c was 204 68 ma

wave impact characteristics of plunging breakers acting on gravel beaches abstract this paper presents observations of pressure impulses from wave impacts of breaking waves on steep coarse grained beaches it builds upon recent investigations on gravel beaches which suggest the wave impact of a plunging breaker is an important process that shapes the morphology of these beaches and that is not taken into account under many modelling frameworks pedrozo acuna a simmonds d j chadwick a j and silva r 2007 a numerical empirical approach for evaluating morphodynamic processes on mixed and gravel beaches mar geol 241 1 2 1 18 full scale laboratory measurements of induced pressures by plunging breakers acting on gravel beaches are reported showing that these are more significant than those reported for sandy beaches under the forcing of similar wave conditions additionally four different types of pressure curves are identified and classified in terms of the type of forcing behind its generation it is shown that measured impact pressures within the gravel beach are a consequence of plunging breakers propagating over the beach profile with maximum pressure values being up to 4 5 times the quasi hydrostatic induced pressure for a given wave height it is demonstrated that the largest measured impacts are not only related to larger values of wave height and vertical displacement of the free surface but also to the wave steepness of the incident wave results suggest that between two plunging breakers of the same height the steeper will produce a stronger wave impact the plunging of breakers onto a gravel beachface and the ensuing pressure gradients are suggested as a key mechanism for understanding sediment transport and the resulting morphology of gravel beaches

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

ancient graphite in the eoarchean quartz pyroxene rocks from akilia in southern west greenland i petrographic and spectroscopic characterization because all known eoarchean 3 65 ga volcano sedimentary terranes are locked in granitoid gneiss complexes that have experienced high degrees of metamorphism and deformation the origin and mode of preservation of carbonaceous material in the oldest metasedimentary rocks remain a subject of vigorous debate to determine the biogenicity of carbon in graphite in such rocks carbonaceous material must be demonstrably indigenous and its composition should be consistent with thermally altered biogenic carbon as well as inconsistent with abiogenic carbon here we report the petrological and spectroscopic characteristics of carbonaceous material typically associated with individual apatite grains but also with various other minerals including calcite in a 3 83 ga granulite facies ferruginous quartz pyroxene unit qp rock from the island of akilia in southern west greenland in thin sections of the fine grained parts of akilia qp rock sample g91 26 mapped apatites were found to be associated with graphite in about 20 of the occurrences raman spectra of this carbonaceous material had strong g band and small d band absorptions indicative of crystalline graphite three apatite associated graphites were found to contain curled graphite structures identified by an anomalously intense second order d band or 2d band raman mode these structures are similar to graphite whiskers or cones documented to form at high temperatures raman spectra of apatite associated graphite were consistent with formation at temperatures calculated to be between 635 and 830 c which are consistent with granulite facies metamorphic conditions three graphite targets extracted by focused ion beam fib methods contained thin graphite coatings on apatite grains rather than inclusions sensu stricto as inferred from transmitted light microscopy and raman spectroscopy tem analyses of graphite in these fib sections showed a 0 0 0 2 interplanar spacing between 3 41 and 3 64 a for apatite associated graphite which is larger than the spacing of pure graphite 3 35 a and may be caused by the presence of non carbon heteroatoms in interlayer sites samples analyzed by synchrotron based scanning transmission x ray microscopy stxm also confirmed the presence of crystalline graphite but abundances of n and o heteroatoms were below detection limit for this method graphite in the akilia qp rock was also found to occur in complex polyphase mineral assemblages of hornblende calcite sulfides magnetite that point to high temperature precipitation from carbon bearing fluids these complex mineral assemblages may represent another generation of graphitization that could have occurred during the amphibolite facies metamorphic event at 2 7 ga several observations point to graphitization from high temperature fluid deposition for some of the akilia graphite and our results do not exclude a biogenic source of carbon in graphite associated with apatite but ambiguities remain for the origin of this carbon

surf zone dynamics simulated by a boussinesq type model part i model description and cross shore motion of regular waves abstract this is the first of three papers on the modelling of various types of surf zone phenomena in this first paper part i the model is presented and its basic features are studied for the case of regular waves the model is based on two dimensional equations of the boussinesq type and it features improved linear dispersion characteristics possibility of wave breaking and a moving boundary at the shoreline the moving shoreline is treated numerically by replacing the solid beach by a permeable beach characterized by an extremely small porosity run up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves the inclusion of wave breaking is based on the surface roller concept for spilling breakers using a geometrical determination of the instantaneous roller thickness at each point and modelling the effect of wave breaking by an additional convective momentum term this is a function of the local wave celerity which is determined interactively the model is applied to cross shore motions of regular waves including various types of breaking on plane sloping beaches and over submerged bars model results comprise time series of surface elevations and the spatial variation of phase averaged quantities such as the wave height the crest and trough elevations the mean water level and the depth averaged undertow comparisons with physical experiments are presented the phaseaveraged balance of the individual terms in the momentum and energy equation is determined by time integration and quantities such as the cross sectional roller area the radiation stress the energy flux and the energy dissipation are studied and discussed with reference to conventional phase averaged wave models the companion papers present cross shore motions of breaking irregular waves swash oscillations and surf beats part ii and nearshore circulations induced by breaking of unidirectional and multidirectional waves part iii

swash on a gently sloping beach waves observed in the inner surf and swash zones of a fine grained gently sloping beach are modeled accurately with the nonlinear shallow water equations the model is initialized with observations from pressure and current sensors collocated about 50 m from the mean shoreline in about i m depth and model predictions are compared to pressure fluctuations measured at five shoreward locations and to run up run up was measured with a vertical stack of five wires supported parallel to and above the beach face at elevations of 5 10 15 20 and 25 cm each 60 m long run up wire yields time series of the most shoreward location where the water depth exceeds the wire elevation as noted previously run up measurements are sensitive to the wire elevation owing to thin run up tongues not measured by the more elevated wires as the wire elevation increases the measured mean run up location moves seaward low frequency infragravity energy decreases and higher frequency sea swell energy increases these trends as well as the variation of wave spectra and shapes e g wave skewhess across the inner surf zone are well predicted by the numerical model

geo and cosmochemistry of the twin elements yttrium and holmium we have analyzed the y ho ratios in bulk chondrites chondrules and four ca and al rich inclusions cais from carbonaceous and unequilibrated ordinary and enstatite chondrites ec by laser ablation inductively coupled mass spectrometry la icpms we demonstrate that bulk rock sample preparation by containerless melting is a suitable method for preparation of bulk rock samples for high precision la icpms bulk chondrites have variable y ho ratios carbonaceous chondrites ci1 cm2 cv3 and ck4 have a common y ho ratio 25 94 0 08 2 that is regarded as the solar system y ho ratio the y ho ratio increases from carbonaceous through ordinary ll l h to enstatite chondrites el6 which show the highest y ho ratio of 27 25 we discuss the result with respect to the origin of fractionation of re and os between chondrite groups within analytical error y and ho show a good correlation in oc and cv3 chondrules and define an y ho ratio of 26 22 0 40 2 y ho fractionation in ca and al rich inclusions is related to differences in volatility the bulk silicate earth is suggested to have a solar y ho ratio and links the earth with carbonaceous chondrites y ho variations in primitive and differentiated terrestrial igneous rocks are discussed in framework of incompatibility of y and ho during partial melting applicability of y ho as tracer for or against a sedimentary origin of the putative host rock of the earth s oldest traces of life from the island of akilia is briefly discussed

velocity predictions for shoaling and breaking waves with a boussinesq type model abstract in this paper the performance of a 1 d boussinesq model is evaluated against laboratory data for its ability to predict surf zone velocity moments wave evolution over a plane beach and a complex bathymetry both extending into the surf zone is examined for six cases for the plane beach these comprise two cases a spilling and a plunging cnoidal wave for the complex bathymetry these comprise four cases of longer and short wavelengths spilling and plunging breakers with regular and irregular periodicity the model evaluation places emphasis on parameters of the wave field that could be used for the prediction of sediment transport orbital velocity undertow velocity skewness kurtosis and asymmetry it is found that despite an overestimation of the depth averaged horizontal velocity in the regular waves cases the predicted higher order velocity moments and undertow are in good agreement with the laboratory data a bispectral analysis demonstrates that the nonlinear transfers of energy amongst the low order harmonics are well reproduced but energy exchanges with the higher harmonics are less well predicted as a result the model handles velocity moments better in the shorter wave tests than in the long wave cases where triad interactions are stronger of the four parameters describing wave breaking the model behaviour is most sensitive to the critical wave front slope b especially with regard to velocity skewness and kurtosis predictions it is also found that increasing the thickness of the surface roller for the case of plunging breakers improves the model s performance