predicting the crest height of a gravel beach the beach crest is a common morphological feature formed by the deposition of sediment carried up slope by wave swash the elevation to which waves can pile gravel is a function of the size and density of the material relative to the hydraulic components of swash velocity wave frequency and runup height two equations 17 and 21 that predict the height of the beach crest to the wave forces and the beach material are derived the first derivation compares the wave force acting to move a stone up the beach face with a weight force acting to hold the stone in place the second derivation relates the potential energy per unit area of the beach crest to the total wave energy that lifted and deposited the material above a given sea level datum as a test of the derived equations the actual crest height of one natural gravel beach was accurately estimated by both equations derived further research and testing on other natural beaches are needed to fully verify eqs 17 and 21 a comparison of other equations eqs 2 3 and 4 that predict crest height is also made the poor fit of the other equations are a result of using values for the coefficients that were established in wave tank experiments another shortcoming of eqs 3 and 4 is that they do not include variables related to the beach material hence they predict that all particle sizes from sand to boulders would be piled to the same elevation by the same wave forcing eq 2 includes a particle size variable but predicts increasingly higher beach crests for larger particles more realistic results for all three equations eqs 2 3 and 4 would be expected with field tested values for the coefficients but a range in values for each different beach would be necessary the advantage of eqs 17 and 21 is that equations are not dependent on coefficients whose values come from correlation with other data sets

coastal gravel barrier hydrology observations from a prototype scale laboratory experiment bardex abstract a prototype scale laboratory study bardex barrier dynamics experiment was conducted within the 250 m long and 7 m deep delta wave flume the netherlands a 4 m high and 50 m long gravel barrier d50 11 mm was constructed within the central region of the flume enabling a back barrier lagoon to be located at its landward side by the installation of a multi stage pump system the water levels at the sea and lagoon sides of the barrier could be manipulated independently a series of experiments were undertaken to examine the groundwater fluctuations and flow within the barrier system subject to varying lagoon levels and wave conditions in accordance with previous sand experiments the wave induced watertable over height at the beachface was confirmed to be independent of sediment characteristics varying back barrier lagoon levels were observed to have significant effect on both the maximum watertable over height within the barrier and shoreline set up vertical position of the point of intersection between mean water surface through the swash zone and beachface as well as the direction and magnitude of though barrier groundwater flux the effective hydraulic conductivity of the d50 11 mm gravel barrier was determined to be k 0 16 m s 1 at higher reynolds numbers re 40 associated with local watertable gradients exceeding 0 025 and resulting turbulent losses the transition from laminar to turbulent through barrier flow was indicated by a reduction in local k however for the parameter range encountered this effect was modest only

continental ichnofossil assemblage from the upper silurian of laurentia the bloomsburg formation of eastern pennsylvania abstract few unequivocal silurian examples of continental ichnofossils have been reported in eastern pennsylvania the upper silurian bloomsburg formation consists of fluvial deposits that have yielded a low diversity ichnofauna described here the rarity of reported silurian continental ichnofauna the quality of the recovered ichnofossil specimens as well as the richly descriptive sedimentary and palaeontological context makes this discovery significant by expanding our understanding of continental ichnodiversity and affirming ichnotaxa reported elsewhere the bloomsburg formation ichnofauna now suggests the possibility that there was a cosmopolitan global ichnofauna of relatively low ichnodiversity in continental especially fluvial paleoenvironnments during the late silurian the fluvially deposited bloomsburg formation is characterized by erosively based fining up sequences from medium grained sandstone to mudstones channel fills are dominated by ripple laminated strata and thinner graded beds floodplain deposits are characterized by thinly laminated graded beds consisting of fine grained siltstones to mudstones thicker laminated mudstones contain reduction halos around ribosome traces mudcracks and some well developed bk horizons of calcisols the bloomsburg fluvial systems thus were low gradient systems that built extensive floodplain deposits and were transitional between low and high sinuosity fluvial systems the strata contain a low diversity invertebrate ichnofauna that includes 1 sinuous traces palaeophycus 2 bilobate oval traces rusophycus 3 slightly sinuous traces with a medial ridge and scratches cruziana 4 two rows of parallel circular or ellipsoid depressions diplichnites 5 substrate penetrating burrows not identified and 6 traces of fossil plant roots palaeophycus and substrate penetrating burrows are the dominant ichnofossils in the bloomsburg formation the bloomsburg formation ichnofauna adds an important datapoint in western laurentia to the distribution of the biota of the freshwater ecosystem of the late silurian it also well represents the epifaunal arthropod ichnofauna of the diplichnites ichnoguild of the scoyenia ichnofacies developed in fluvial environments during the silurian to devonian

reconstructing the siluro devonian coastline of gondwana insights from the sedimentology of the port stephens formation falkland islands silurian and lower devonian sedimentary successions are uncommon within the remnants of gondwana the port stephens formation the basal unit of the middle palaeozoic west falkland group presents a rare opportunity to study gondwanan material of siluro devonian age the formation on west falkland is c 2560 m thick and consists of five members plantation albemarle mount alice south harbour and fish creek thirty five lithofacies are defined using variations in grain size and bedding characteristics the distribution of these lithofacies and their associated ichnofacies between the various members lead us to suggest terrestrial and shallow marine deposition on an extensive gently shelving alluvial to coastal plain vertical facies trends through the port stephens formation and into the base of the overlying fox bay formation record a complex superposition of subenvironments within a distinct overall transgressive regressive transgressive pattern with the bulk of sediment accumulating during the regressive phase palaeocurrents indicate a basin to the present day ne throughout these results together with lithostratigraphic correlations between the port stephens formation and the nardouw subgroup in south africa are consistent with a reconstructed position off eastern south africa and on the palaeo pacific margin of gondwana requiring a near 180 rotation of the falkland island microplate during break up in agreement with previous models we suggest that global changes in sea level during the mid late silurian and early devonian strongly influenced changes in the depositional environment enhanced erosion of the continental margin and extensive sediment bypass during the regressive phase of this cycle could help to explain the low abundance of preserved gondwanan material of this age

observations of gravel beach dynamics during high energy wave conditions using a laser scanner the work described in this publication was supported by the epsrc project arcoes adaptation and resilience of the uk energy system to climate change epsrc reference ep 1035390 1 and by epsrc grant ep h040056 1 in partnership with the channel coastal observatory cco the full text is under embargo until 01 01 16

palaeoecology of an early permian playa lake trace fossil assemblage from castle peak texas usa abstract the early permian choza formation of the clear fork group at castle peak in texas usa contains a diverse and remarkably abundant trace fossil assemblage comprising exquisitely preserved arthropod trackways diplichnites gouldi types a and b diplichnites isp a and b lithographus isp and cf kouphichnium isp striated trails cruziana problematica and isolated resting traces rusophycus carbonarius and r furcosus surface or shallow subsurface grazing trails or burrows gordia indianensis helminthoidichnites tenuis treptichnus isp a nodular trail and unilobate epichnial trails backfilled deposit feeding burrows planolites beverleyensis meniscate backfilled burrows taenidium barretti horizontal branching networks and tetrapod trackways dromopus palmatus erpetopus willistoni varanopus curvidactylus and cf amphisauropus isp trace fossils formed in and around the margins of a shallow ephemeral playa lake within an alluvial plain and provide evidence of temporary communities comprising arthropods most notably notostracan branchiopod crustaceans as well as euthycarcinoids myriapods insects and tetrapods including protorothyridid captorhinid and araeoscelid reptiles and rare amphibians periodic influxes of water into the alluvial plain filled various depressions creating temporary habitats and flourishes of life and activity the trace fossil assemblage is typical of the scoyenia ichnofacies and is similar to other assemblages from a range of different transitional subaqueous to subaerial settings indicating that the distribution of trace fossils is not inextricably linked to the depositional setting itself but rather to the environmental factors that arise such diverse trace fossil assemblages probably reflect relatively long lived ephemeral water bodies whereas more impoverished examples probably represent shorter lived ephemeral water bodies assemblages such as castle peak with abundant delicate arthropod trackways probably reflect low energy conditions conducive to the presence of an abundant vagile epifauna and the preservation of their trackways whereas assemblages with open vertical burrows tend to lack arthropod trackways and probably reflect higher energy conditions trace fossil assemblages dominated by arthropod and tetrapod trackways may represent fleeting preservation windows following sheetfloods on floodplains

silurian vegetation stature and density inferred from fossil soils and plants in pennsylvania usa silurian fossil plants range from small vascular plants rhyniophytes to moderately large fungi nematophytes but give little idea of the stature rooting depth and plant density of vegetation on land silurian to earliest devonian palaeosols from the bloomsburg formation show unusually deep bioturbation of several distinct kinds surface ground parallel rhizomes of vascular land plants to 20 cm deep are penetrated by burrows like those of millipedes to 80 cm but the deepest stratum down to 2 m below the surface has features interpreted as bioturbation by fungal hyphae and rhizines plant like axes associated with palaeosols are evidence of vegetation with three distinct tiers above ground as inferred from diameters using allometric scaling equations nematophytes germanophyton psygmophylloides up to 1 3 m tall formed a tier above herbaceous vascular land plants 30 cm and ground cover 2 with spacing 20 cm that closed canopy in seasonally dry wetland palaeosols comparable with modern marsh vegetation vascular land plants of well drained soils in contrast were scattered with bare earth between wetland ground cover was thus more extensive than cover of well drained soils and precursor lichens facilitated early evolution of vascular land plants supplementary material tables of mineral and grain size proportions major element chemical analyses and plant spacing and size are available at http www geolsoc org uk sup18848

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

polar gravel beach ridge systems sedimentary architecture genesis and implications for climate reconstructions south shetland islands western antarctic peninsula abstract the sedimentary architecture of polar gravel beach ridges is presented and it is shown that ridge internal geometries reflect past wave climate conditions ground penetrating radar gpr data obtained along the coasts of potter peninsula king george island show that beach ridges unconformably overlie the prograding strand plain development of individual ridges is seen to result from multiple storms in periods of increased storm wave impact on the coast strand plain progradation by contrast is the result of swash sedimentation at the beach face under persistent calm conditions the sedimentary architecture of beach ridges in sheltered parts of the coast is characterized by seaward dipping prograding beds being the result of swash deposition under stormy conditions or aggrading beds formed by wave overtopping by contrast ridges exposed to high energy waves are composed of seaward as well as landward dipping strata bundled by numerous erosional unconformities these erosional unconformities are the result of sediment starvation or partial reworking of ridge material during exceptional strong storms the number of individual ridges which are preserved from a given time interval varies along the coast depending on the morphodynamic setting sheltered coasts are characterized by numerous small ridges whereas fewer but larger ridges develop on exposed beaches the frequency of ridge building ranges from decades in the low energy settings up to 1600 years under high energy conditions beach ridges in the study area cluster at 9 5 7 5 5 5 and below 3 5 m above the present day storm beach based on radiocarbon data this is interpreted to reflect distinct periods of increased storminess and or shortened annual sea ice coverage in the area of the south shetland islands for the times around 4 3 c 3 1 1 9 ka cal bp and after 0 65 ka cal bp ages further indicate that even ridges at higher elevations can be subject to later reactivation and reworking a careful investigation of the stratigraphic architecture is therefore essential prior to sampling for dating purposes

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

extreme value statistics for wave run up on a natural beach abstract statistics of wave run up maxima have been calculated for 149 35 minutes data runs from a natural beach during the experiment incident wave height varied from 0 4 to 4 0 m incident wave period from 6 to 16 s and beach face slope from 0 07 to 0 20 four extreme statistics were calculated the maximum run up height during each run the 2 exceedence level of shoreline elevation the 2 exceedence height for individual run up peaks and the 2 exceedence level for swash height as determined by the zero upcrossing method these statistics were best parameterized when normalized by the incident significant wave height and plotted against the iribarren number h l 0 1 2 the swash data with set up removed showed less scatter than total run up with set up included for iribarren number greater than 1 5 the run up was dominated by the incident frequencies for lower iribarren number longer period motions dominated the swash a reasonable value of wave steepness for a fully developed storm sea is 0 025 so that a storm iribarren number can be estimated as 6 3 times the beach slope using this and an offshore design wave height the included graphs may provide guidance in determining a design run up height

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

processes controlling river mouth lagoon dynamics on high energy mixed sand and gravel coasts abstract the river mouth lagoons of new zealand s gravel bed braided rivers are highly dynamic responding to changes in waves and river flows at timescales of hours and days to years unlike other freshwater dominated coastal wetlands and lagoons they exist along open coasts that are typically retreating with cliffed hinterlands these lagoons are common on new zealand s high energy coarse sediment coastlines and are known locally as h pua this paper employs field observations from the hurunui h pua to investigate the main processes controlling the dynamics of h pua lagoons based on two years of time lapse imagery plus concurrent wave river flow and sea level data an improved conceptual model of lagoon dynamics was developed the model describes how onshore bar migration of river sourced gravel and sand drives initial constriction offsetting of the river mouth following floods it also explains how gravel deposition in the lagoon reduces the threshold flow required to cause primary breach of the barrier opposite the point the river enters the lagoon three processes are identified which affect lagoon width wave overwashing of the gravel barrier narrows the lagoon migration of the highly dynamic lagoon outlet channel resets the barrier position to seaward and river floods occurring while the outlet channel is offset from the river flush sediment from the lagoon system eroding its bed and banks both processes affecting lagoon widening rely on lagoon outlet channel migration indicating that outlet channel dynamics are an important control on lagoon size

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

trace fossil evidence for late ordovician animals on land fossil burrows within newly recognized buried soils in the late ordovician juniata formation near potters mills in central pennsylvania represent the oldest reported nonmarine trace fossils they are thought to have been an original part of the soil because their greater density toward the top of the paleosols corresponds with mineralogical microstructural and chemical changes attributed to ancient weathering and because about half the burrows are encrusted with nodular carbonate interpreted as caliche associated fossil caliche the size distribution of the burrows and their w shaped backfills are evidence that the burrows may have been excavated by bilaterally symmetrical organisms that grew in well defined growth increments and were able to withstand desiccation among well known soil organisms millipedes are burrowing animals that satisfy these requirements but have a fossil record not quite this old this trace fossil evidence for animals on land together with recent palynological evidence for land plants of a bryophytic grade of evolution during late ordovician time are indications of terrestrial ecosystems of slightly greater antiquity and complexity than hitherto suspected

measurements of morphodynamic and hydrodynamic overwash processes in a large scale wave flume overwash is an important process that controls short term barrier dynamics as well as long term barrier migration but this process is difficult to study in the field due to its rare occurrence and the challenging conditions under which it occurs this paper uses data collected during the bardex ii experiment in the delta flume the netherlands where a proto type barrier was subjected to a range of wave and water level conditions the objectives of this research are to 1 compare the morphologic response to overwash on a gravel barrier bardex 2008 experiment with that on a sandy barrier bardex ii 2 understand the influence of wave period on overwash characteristics and sediment transport and 3 improve current knowledge of overwash hydrodynamics the comparative analysis shows that barrier overwash can be affected by negative feedback that stabilises the barrier through barrier crest accretion on gravel barriers and by submerged bar development on sandy barriers an increase in the wave period induced a reduction in overwash frequency over the crest but no significant relation was found between wave peak period and overwash discharge nevertheless overall water discharge during an overwash episode significantly correlates with overall overwash sediment transport rate overwash flow depths during the experiment were relatively shallow and velocities were similar compared to those measured during previous studies and reported in the literature despite the controlled laboratory conditions collection of reliable and accurate measurements of overwash velocities remains challenging

storm overwash of a gravel barrier field measurements and xbeach g modelling abstract gravel barriers provide a natural form of coastal protection and flood defence for many sites around the uk and worldwide predicting their vulnerability to different storm impact regimes that cause overtopping and overwash is crucial as these processes can lead to hazardous consequences such as inundation of the back of the barrier or breaching this paper presents the first field measurements of storm overwash events on a gravel beach loe bar cornwall england high frequency in situ observations 2 hz were performed using a 2d laser scanner and allowed a complete characterization of the overwash flows velocity and depth and morphological response along a cross shore section of the barrier these novel measurements are used to validate the numerical model xbeach g to forecast overwash discharge several simulations were performed with xbeach g to investigate the thresholds for the different storm impact regimes given a variety of water levels and wave heights wave period and wave spectral shape are found to significantly affect these thresholds while short period waves dissipate most of their energy by breaking before reaching the swash zone and produce short runup excursions long period waves due to their low steepness arrive at the swash zone unbroken with enhanced heights due to shoaling thus promoting large runup excursions when the offshore wave spectrum has a bimodal shape wave transformation in shallow water causes the long period peak to dominate the swash giving large runup excursions long period waves or strongly bimodal waves result in enhanced runup thereby reducing the thresholds for barrier overtopping or overwashing

identifying storm impacts on an embayed high energy coastline examples from western ireland abstract large sections of the western irish coast are characterised by a highly compartmentalised series of headland embayment cells in which sand and gravel beaches are backed by large vegetated dune systems exposure to modally high energy swell renders most of these beaches dissipative in character a mesotidal range c 3 5 4 5 m exists along much of the coast analysis of instrumental wind records from three locations permitted the identification of a variety of storm types and the construction of storm catalogues few individual storms were recorded at all three stations indicating a lack of regional consistency in storm record of the total storms recorded only a small percentage are potentially damaging onshore directed and even fewer span a high tide and thus potentially induce a measurable morphological response at the coast through a combination of historical records meteorological records field observations and wave modelling we attempt to assess the impact of storms quantifiable records of coastal morphology maps air photos and beach profiles are few in number and do not generally record responses that may be definitely attributed to specific storms numerical wave simulations and observations at a variety of sites on the west irish coast however provide insights into instantaneous and medium term decadal storm responses in such systems we argue that beaches and dunes that are attuned to modally high energy regimes require extreme storms to cause significant morphological impact the varying orientation of beaches a spatially nonuniform storm catalogue and the need for a storm to occur at high water to produce measurable change impart site specific storm susceptibility to these embayments furthermore we argue that long period wave energy attenuation across dissipative shorefaces and beaches reduces coastal response to distant storms whereas short period locally generated wind waves are more likely to cause major dune and beach erosion as they arrive at the shoreline unrefracted this apparently variable response of beach and dune systems to storm forcing at a decadal scale over a coastline length of 200 km urges caution in generalising regarding regional scale coastal responses to climatic change

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

runup estimations on a macrotidal sandy beach abstract this paper presents a methodological approach to calculate runup from the analysis of morphodynamic conditions on a macrotidal sandy beach the method is based on measurements of the elevation of high tide deposits and on the analysis of morphological and hydrodynamic changes a series of measurements has been carried out on the beach of vougot brittany france under different wave conditions this allowed to assess runup formula effectiveness on a macrotidal sandy beach and to determine the best slope parameters to estimate runup the results suggest that on that macrotidal sandy beach the slope of the active section of the upper beach should be used instead of the entire slope of the foreshore the latter resulting in an underestimation of runup elevations when used in predictive equations from the literature results obtained with widely used equations are relatively well correlated with observed values r2 0 63 an analysis of the relationship between observed runup elevations and various variables has enabled the establishment of a runup estimation formula with a relatively good fit to the study site r2 0 86

estimation of grain size distributions and associated parameters from digital images of sediment abstract a new technique to estimate the grain size distribution gsd from a digital image of sediment is proposed advancing the applicability of a suite of sedimentary look up catalogue approaches originated by rubin rubin d m 2004 a simple autocorrelation algorithm for determining grain size from digital images of sediment journal of sedimentary research 74 1 160 165 the outputs of an automated procedure to estimate the gsd from digital images of sediment are examined with reference to the distributions obtained from both manually sieving the corresponding sediment samples and axial measurements made on the grains in the images measures of grain size obtained from the imaging procedure correlate very well with grain size measures derived from both the number frequency and mass frequency curve as expected the gsd obtained from the new automated approach based on kernel density compared better with point counts because of a shared two rather than three dimensionality the gsd shape is not always mimicked exactly however the percentiles obtained from the cumulative gsd compare well with those from sieved distributions which allow for the first time computation of graphical sorting and skewness from digital images of sediment which are accurate reflections of those measures obtained for point count and sieved samples the new approach allows for realistic gsds from which the residual can be computed thus a numerical criterion upon which the grain size distribution from an image can be accepted or rejected finally a method is presented whereby two dimensional autocorrelogram fields are derived from image power spectra ellipsoids are fitted to isolines of autocorrelation coefficients and from this the dominant axial lengths and orientation of these isolines which could facilitate computation of major and minor axis lengths of grains in sample images as well as their dominant orientation in turn this could allow for parameterisation of axial ratios for parameterisation of 2d shape such analysis is completely automated rapid and non intrusive

storm response and beach rotation on a gravel beach slapton sands u k abstract continuous argus video data and fortnightly measurements of subaerial morphology were obtained over a 3 year period from a steep macrotidal gravel beach on the southwest coast of the u k concurrent wave and water level data were also collected enabling the correlation of the observed morphological changes to the hydrodynamic forcing wave conditions are generally low h s 0 5 1 m but the beach is affected by frequent storm wave activity c 15 storms per year with h s 2 4 m with waves either approaching from the south swell waves or from the east wind waves an assessment of the three dimensional morphological response of the beach to the two typical storm types was carried out by analysing the impact of 27 storms that occurred from april 2007 to april 2009 southerly storms cause accretion of the supratidal zone and erosion of the intertidal zone and a significant loss in overall beach volume easterly storms on the other hand induce supratidal erosion and intertidal accretion and a significant gain in overall beach volume during the intervening calm periods a small supratidal berm is constructed and a modest gain in overall beach volume occurs wave modelling indicated that opposing longshore energy fluxes occur for the different storm types with a northerly energy flux during southerly storms and a southerly flux during easterly storms weekly shorelines derived from the argus images revealed that the northern end of the beach widened by c 30 m and the middle beach receded by c 40 m over a relatively brief period a few months the occurrence of this beach rotation event is attributed to a higher frequency of southerly storms and or a lower frequency of easterly storms over this period thus the development and stability of the beach on annual time scales depend on the relative contributions of the two storm types and their sequencing longshore sediment transport lst rates derived from the data on beach morphological change were compared with several littoral drift formulae previously applied to gravel beaches the cerc equation with a proportionality factor k between littoral drift rate i l and longshore wave energy flux p l of k 0 054 yielded the best results

wave runup and overwash on a prototype scale sand barrier abstract accurate methods to predict wave runup are of critical importance to coastal engineers extreme runup during storm conditions can present a danger to coastal infrastructure and lead to dune overtopping and erosion overwash of barrier beaches and is an essential design parameter for certain coastal protection works this paper uses data obtained during the unique bardex ii prototype scale laboratory experiment on a reflective sand barrier to investigate wave runup and overwash runup measurements were acquired using ultrasonic altimeters 2d scanning lidar and camera systems under controlled wave and water level conditions it was found that extreme runup r 2 scaled well with the deepwater irribarren number where the beach slope was taken to be the beach face gradient the lower limit of the swash zone defined by the 2 wave rundown limit was also found to be a function of the irribarren number and was consistently below the swl in all tests the high resolution free surface measurements obtained using the ultrasonic altimeters and lidar enabled an analysis of the dynamics of individual swash events it was found that the vertical runup excursion of each swash correlated strongly with the height of the bore at collapse and could be predicted based on the assumption of a conversion of potential to kinetic energy at bore collapse

mechanisms to account for the longshore spacing of overwash throats on a coarse clastic barrier in southeast ireland abstract the longshore spacing of overwash throats on two contrasting sections of a coarse clastic reflective barrier beach in southeast ireland is examined for evidence of spatial periodicity a fixed barrier section carnsore with an irregular barrier top dune field exhibits random longshore throat positions related to pre existing irregularities in the seaward dune boundary a free barrier section tacumshin without a barrier top dune field shows regular longshore throat positions with a peak throat to throat periodicity of between 30 40 m similar longshore periodicity is found in persistent high level beach cusps above mhws though not always spatially in phase there is no consistent near shore rhythmic morphology that can account for this spacing the storm event which generated the tacumshin overwash appears to have dominant longer incident wave periods than normal in celtic sea storms on weight of circumstantial evidence it is reasoned that this dominant wave period range 9 11 s can be related to a zero mode sub harmonic edge wave whose longshore wavelength matches the peak periodicity of overwash spacing overwash sites on this reflective barrier may be determined by an edge wave controlled extension of run up which generates high level cusps and thereby creates washover routeways the presence or absence of a barrier top dune field is a secondary control on whether washover is successful in reaching the back barrier usually only where surge penetration and pre existing dune irregularities coincide does washover occur

alluvial facies evolution during the palaeozoic greening of the continents case studies conceptual models and modern analogues the palaeozoic greening of the continents the appearance and expansion of embryophytes land plants in terrestrial environments was arguably the most fundamental phanerozoic change to the earth system thirteen case studies of cambrian to devonian fluvial deposits from north america and europe are documented here to illustrate the evolution of fluvial style during this period during the cambro ordovician prior to the advent of terrestrial vegetation fluvial systems laid down relatively coarse sands with little mud resulting in self formed channels and an architecture dominated by broad sheets of trough cross beds sheet braided style similar deposits formed across a wide range of latitudes and passed basinward into sandy coastal deposits from the mid ordovician onwards an increase in floodplain mudstone corresponds broadly with the appearance of embryophytes which would have progressively enhanced upland weathering mud production and floodplain storage of fines during the late silurian small heterolithic channel bodies with lateral accretion sets provide the first evidence of meandering channels and floodplain mudstones contain more varied palaeosols especially calcretes which appear abundantly for the first time by the early devonian channel deposits comprise sandstone lenses channelled braided style probably due to the increased bank strength and cohesion and reduced potential for sediment sorting imparted by sand mud mixtures muddy coastal deposits are prominent by the upper devonian fluvial deposits commonly contain fossil trees and large mainstem meandering channels with lateral accretion sets indicating that rooted vegetation stabilized channels the advent of stable floodplains with levees crevasse splays and organic litter would have encouraged the diversification of terrestrial invertebrates which left alluvial ichnological signatures from the late silurian onwards

impact of coral reef mining pits on nearshore hydrodynamics and wave runup during extreme wave events small island developing states are among the most vulnerable areas to the impact of natural hazards and climate change flooding due to storm surges and extreme waves coastal erosion and salinization of freshwater lenses are already a serious threat and could lead to irreversible consequences in the coming decades reef flat mining is one of the most common practices to source the required material for the implementation of coastal protection measures but concerns remain that partial removal of the protective reef could increase wave loading on the islands however the available data and knowledge on the effects of these mining pits are currently very limited this study provides new insights on the effects that pits may have on nearshore hydrodynamics and wave runup results are based on a large numerical data set of fringing reefs derived using the validated xbeach nonhydrostatic process based model model results indicate that excavation pits cause a decrease in infragravity wave energy around the fundamental mode of the reef which is partly caused by reduced wave transmission additionally changes in sea and swell wave energy are attributed to reduced transmission a decrease in wave dissipation and triad wave wave interaction furthermore in 13 of all modeled cases an increase in wave runup is observed mainly due to more sea and swell wave energy reaching the shoreline this probability is lowest for narrow pits relative to the reef flat width or pits located further from shore

large scale laboratory investigation into the effect of varying back barrier lagoon water levels on gravel beach morphology and swash zone sediment transport abstract it is generally accepted that the effect on beach morphology of the interactions between swash motion and the beach groundwater table depends on the elevation of the latter relative to that of the sea specifically a low beach groundwater table is considered to enhance onshore sediment transport and beach accretion while the reverse is thought to hold for a high beach groundwater table here we use the results of a carefully designed series of tests conducted in the delta flume the netherlands as part of the barrier dynamics experiment bardex to unequivocally demonstrate the validity of this assertion during the experiment a 4 m high and 50 m long gravel barrier d 50 11 mm was constructed within the central region of the 250 m long and 7 m deep wave flume enabling a back barrier lagoon to be located at its landward side the groundwater table in the beach was manipulated by lowering and raising the lagoon level and the gravel beach was subjected to variable wave conditions and sea lagoon levels using as the initial beach profile the morphology resulting from 90 min of wave forcing with the sea and lagoon at the same level the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and beach accretion whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and beach erosion the divergent beach morphological responses for the low and high lagoon levels could not be attributed to changes in the bulk swash hydrodynamics i e based on single point velocity measurements arising from a difference in the amount of swash infiltration into the unsaturated beach instead application of a sediment transport model that accounts for the effects of in exfiltration suggested that the onshore sediment transport and beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the beachface due to the large hydraulic conductivity of gravel k o 0 1 m s 1 the effect of altered shear stresses due to in exfiltration may be an important factor in sediment transport in the swash zone of gravel beaches

late holocene storm imprint in a coastal sedimentary sequence northwest iberian coast a combination of sedimentological geomorphological and pedological methods has been used to study a late holocene sedimentary sequence in a rock coast sector from nw spain with the aim of relating it to storm events and their morphodynamic effects the sequence contains two coarse beach layers at an elevation of 2 8 3 5 m above the present highest astronomical tide hat radiocarbon dating revealed that their deposition had begun during 1735 1590 cal yr bp and has continued until the present the entire beach system experienced considerable morphological change after 1320 1230 cal yr bp with a westward displacement of the beach and a retreat of the sedimentary cliff in the eastern section the two beach layers seem to have been formed by vertical aggradation of clasts and sand during high energy storm events highlighting the role of these events in the formation of sedimentary sequences on the rocky coasts of mid atlantic europe the effects of a recent storm event recorded in march 2008 and the

physical modelling of reef island topographic response to rising sea levels abstract low lying coral reef islands are considered extremely vulnerable to the impacts of climate change particularly sea level rise and increasing storm magnitude inundation and erosion are expected to destabilise reef islands and render them uninhabitable within decades however such assertions are founded upon the assumption that reef islands are geomorphologically inert landforms whereas recent planform and cross sectional analysis of reef island morphodynamics demonstrates that many islands are highly dynamic landforms changing in size shape and position on the reef platform this paper describes the first physical modelling experiments to model the whole of island morphodynamic response of reef islands to changes in sea level and wave regime a wave basin is utilised to construct a 1 50 scale three dimensional model of fatato island tuvalu and document the whole of island response across a broad range of wave and water level conditions whole of island results corroborate flume studies and provide new insights into the modes and styles of island change spit rotation as well as lagoonward island recession and vertical oceanward crest accretion are identified as the core island responses to increasing water level and wave conditions however results show that the rate and magnitude of physical adjustment is strongly dependent on the rate and magnitude of sea level rise and wave conditions results challenge existing models of future island susceptibility to wave driven flooding demonstrating that washover processes can provide a mechanism to build and potentially maintain island freeboard above sea level these insights highlight an urgent need to incorporate island morphodynamics into flood risk models in order to produce accurate assessments of future wave driven flood risks and better resolve island vulnerability

detailed investigation of overwash on a gravel barrier abstract this paper uses results obtained from a prototype scale experiment barrier dynamics experiment bardex undertaken in the delta flume the netherlands to investigate overwash hydraulics and morphodynamics of a prototype gravel barrier gravel barrier behaviour depends upon a number of factors including sediment properties porosity permeability grain size and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration a detailed quantification of overwash flow properties and induced bed changes is crucial overwash hydrodynamics of the prototype gravel barrier focused on the flow velocity depth and discharge over the barrier crest and the overwash flow progression across and the infiltration through the barrier during the bardex experiment overwash peak depth 0 77 m velocity 5 m s 1 and discharge max 6 m 3 m 1 were high especially considering the relatively modest wave energy significant wave height 0 8 m conversely to schemes found in the literature average flow depth did not linearly decrease across the barrier rather it was characterised by a sudden decrease at the crest a milder decrease at the barrier top and then propagation as a shallow water lens over the backbarrier the barrier morphological evolution was analysed over a series of 15 min experimental runs and at the timescale of individual overwash events overall the morphological variation did not result from an accumulation of many small consistently erosive or accretionary events but rather the mean bed elevation change per event was quite large 10 mm and the overall morphology change occurred due to a small imbalance in the number of erosive and accretionary events at each location two relationships between overwash hydrodynamic variables were deduced from results 1 between overwash flow depth and velocity a power type relation was obtained and 2 a linear relation was observed between overwash flow depth and maximum overwash intrusion distance across the barrier top i e overwash intrusion findings from this study are useful to enhance the knowledge of overwash processes and also have practical applications on the one hand results shown here can be use for the validation of overwash predictive models and additionally the simple empirical relations deduced from the dataset can be used by coastal managers to estimate overwash intrusion distance which in turn can assist in the location of areas under risk of overwash and breaching

early forest soils and their role in devonian global change a paleosol in the middle devonian aztec siltstone of victoria land antarctica is the most ancient known soil of well drained forest ecosystems clay enrichment and chemical weathering of subsurface horizons in this and other devonian forested paleosols culminate a long term increase initiated during the silurian from silurian into devonian time red clayey calcareous paleosols show a greater volume of roots and a concomitant decline in the density of animal burrows these trends parallel the decline in atmospheric carbon dioxide determined from isotopic records of pedogenic carbonate in these same paleosols the drawdown of carbon dioxide began well before the devonian appearance of coals large logs and diverse terrestrial plants and animals and it did not correlate with temporal variation in volcanic or metamorphic activity the early paleozoic greenhouse may have been curbed by the evolution of rhizospheres with an increased ratio of primary to secondary production and by more effective silicate weathering during silurian time

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

processes and timescales by which a coastal gravel dominated barrier responds geomorphologically to sea level rise story head barrier nova scotia sea level rise slr is considered to be important for barrier behaviour when barriers are swash aligned and single crested which is typical of only one part of a barrier s lifeterm under such conditions gravel barrier retreat rate correlates with mesoscale sub decadal 102 a slr rate is the critical control on barrier retreat as mesoscale slr variation in combination with surge potential is able to raise water level to the elevation threshold sufficient for barrier overwash and hence drive barrier retreat

crestal overtop and washover sedimentation on a fringing sandy gravel barrier coast carnsore point southeast ireland abstract storm sedimentation on a fringing sandy gravel barrier system in southeast ireland is examined recent wave overtopping and overwashing during severe onshore storms have resulted in a distinctive pattern of crest and backbarrier sedimentation this is not easily matched with available models of washover sedimentation drawn from the barrier islands of the eastern united states beach crest overtopping occurs at heights up to 6 m mhws and is related to the development of upper beach swash ramps that are plastered against storm wave eroded dune scarps located at the barrier crest ramp sediments comprise coarse basal beach gravels overlain by coarsening upward units and finally topped by distinctive seawarddipping fine grit coarse sand couplets in places where ramps reach the dune cre t overtopping swash has deposited a fine marine gravel veneer

overwash occurrence consequent on morphodynamic changes following lagoon outlet closure on a coarse clastic barrier the reduction in sediment volume of an ebb tide delta as a consequence of lagoon outlet closure on a coarse clastic barrier in southeast ireland initiated a sequence of beachface and barrier changes downdrift elimination of sediment supply to the ebb delta caused a cessation of downdrift longshore swash bar welding and led to beach volume reductions which in turn allowed a temporal sequence of beach and nearshore morphodynamic domains to develop these domains then controlled the sedimentation regime of the barrier adjacent to the old outlet a temporal sequence of a dissipative barrier b reflective barrier and c inner reflective barrier face outer dissipative subtidal wave regimes match respectively periods of a barrier crest build up by crestal dune development b barrier crest instability barrier width increasing barrier height decreasing due to rhythmic overwash and c a return to barrier crest stability with limited aeolian accretion two barriers at different stages in this sequence are discussed

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

shallow miocene basaltic magma reservoirs in the bahia de los angeles basin baja california mexico the basement in the bahia de los angeles basin consists of paleozoic metamorphic rocks and cretaceous granitoids the neogene stratigraphy overlying the basement is formed from the base to the top by andesitic lava flows and plugs sandstone and conglomeratic horizons and miocene pyroclastic flow units and basaltic flows basaltic dikes also intrude the whole section to further define its structure a detailed gravimetric survey was conducted across the basin about 1 km north of the sierra las flores in spite of the rough and lineal topography along the foothills of the sierra la libertad we found no evidence for large scale faulting gravity data indicates that the basin has a maximum depth of 120 m in the valle las tinajas and averages 75 m along the gravimetric profile high density bodies below the northern part of the sierra las flores and valle las tinajas are interpreted to be part of basaltic dikes the intrusive body located north of the sierra las flores is 2 5 km wide and its top is about 500 m deep the lava flows of the top of the sierra las flores together with the distribution of basaltic activity north of this sierra suggests that this intrusive body continues for 20 km along a nnw trending strike between the sierras las flores and las animas a 0 5 km wide 300 m thick intrusive body is interpreted at a depth of about 100 m this dike could be part of the basaltic activity of the cerro las tinajas and the small mounds along the foothills of western sierra las animas the observed local normal faulting in the basin is inferred to be mostly associated with the emplacement of the shallow magma reservoirs below las flores and las tinajas

overwash threshold for gravel barriers abstract this paper uses results obtained from the large scale bardex experiments undertaken in the delta flume to investigate the morphological response of a prototype gravel barrier to wave and tidal forcing during overwash conditions gravel barrier behaviour depends upon a number of factors such as sediment properties porosity permeability grainsize geological setting and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration the development of a robust quantitative method to define the critical conditions leading to gravel barrier overwashing is important both for scientific and practical management purposes it is known that when wave runup exceeds the barrier crest elevation three outcomes are possible 1 insignificant morphological change when wave runup just overtops the barrier crest and flow velocities are very weak 2 overtopping resulting in accretion on the barrier crest region and barrier stabilisation and 3 overwashing resulting in erosion lowering of the crest region and ultimately to barrier inundation this study provides an insight into the critical conditions that distinguish these two possible outcomes and to the different mechanisms that provide the required positive and negative feedbacks to the sediment dynamics in order to define the overwash threshold condition and to predict the morphological outcome of particular overwash events use is made here of the overwash potential op defined as the difference between the wave runup and the barrier crest elevation to make effective use of op it is necessary to identify a reliable runup predictor following tests using 12 runup equations the stockdon et al stockdon h f holman r a howd p a sallenger a h 2006 empirical parameterization of setup swash and runup coast eng 53 573 588 approach has been identified as the best predictor of runup conditions necessary to generate positive values of op with overtopping and overwashing predicted to occur for average op values of 0 2 m and 0 5 m respectively the use of op values provides a practical means by which to identify potential coastal hazards associated with gravel barrier overwash processes and is considered to have a range of practical coastal management applications

modelling gravel barrier response to storms and sudden relative sea level change using xbeach g abstract this paper investigates the response of a mixed sand and gravel msg barrier coastline to storms and sudden relative sea level change using the numerical model xbeach g the barrier beaches of southern hawke s bay new zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 hawke s bay earthquake historic 1931 and contemporary 2017 morphodynamics of one tectonically uplifted 1 5 m and one subsided 0 78 m barrier were modelled under energetic waves hs 1 6 m xbeach g was designed to simulate pure gravel beach morphodynamics but despite this the model demonstrated high quantitative skill when calibrated for the msg coast results reveal the storm impact regimes of each profile and potential linkages to decadal scale barrier development observed in historical beach profile data storm swash processes at the uplifted profile indicate long term barrier stability due to a lack of change at the barrier crest and ridge building observed in model simulations provides a potential formative mechanism for decadal scale beach progradation at the subsided barrier modelled historic crest build up up to 0 3 m and narrowing over 5 m indicate an overtopping mode of response to sudden relative sea level rise simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions but further work is needed to distinguish the relative importance of historical sudden sea level rise versus deficits in sediment supply to this shoreline

late devonian glacial deposits from the eastern united states signal an end of the mid paleozoic warm period abstract a late devonian polymictic diamictite extends for more than 400 km from northeastern pennsylvania across western maryland and into east central west virginia the matrix supported unbedded locally sheared diamictite contains subangular to rounded clasts up to 2 m in diameter the mostly rounded clasts are both locally derived and exotic some exhibit striations faceting and polish the diamictite commonly is overlain by laminated siltstone mudstone facies associations laminites the laminites contain isolated clasts ranging in size from sand and pebbles to boulders some of which are striated the diamictite laminite sequence is capped by massive coarse grained pebbly sandstone that is trough cross bedded a stratigraphic change from red calcic paleo vertisols in strata below the diamictite to non calcic paleo spodosols and coal beds at and above the diamictite interval suggests that the climate became much wetter during deposition of the diamictite the diamictite deposit is contemporaneous with regressive facies that reflect fluvial incision during the late devonian of the appalachian basin these deposits record a late devonian episode of climatic cooling so extreme that it produced glaciation in the appalachian basin evidence for this episode of climatic cooling is preserved as the interpreted glacial deposits of diamictite overlain by glaciolacustrine varves containing dropstones and capped by sandstone interpreted as braided stream outwash the appalachian glacigenic deposits are contemporaneous with glacial deposits in south america and suggest that late devonian climatic cooling was global this period of dramatic global cooling may represent the end of the mid paleozoic warm interval that began in the middle silurian

how well can wave runup be predicted comment on laudier et al 2011 and stockdon et al 2006 abstract laudier et al 2011 suggested that there may be a systematic bias error in runup predictions using a model developed by stockdon et al 2006 laudier et al tested cases that sampled beach and wave conditions that differed from those used to develop the stockdon et al model based on our re analysis we found that in two of the three laudier et al cases observed overtopping was actually consistent with the stockdon et al predictions in these cases the revised predictions indicated substantial overtopping with in one case a freeboard deficit of 1 m in the third case the revised prediction had a low likelihood of overtopping which reflected a large uncertainty due to wave conditions that included a broad and bi modal frequency distribution the discrepancy between laudier et al results and our re analysis appear to be due in part to simplifications made by laudier et al when they implemented a reduced version of the stockdon et al model

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

seasonal accretion and erosion patterns of a microtidal sandy beach monthly elevation surveys of a 1 5 km stretch of coast at noordwijk the netherlands were made 1 to quantify seasonal variability in the cross shore position of high mean and low tide contours beach width and beach volume and 2 to examine the dependence of the variability on the offshore wave characteristics additionally daily cross shore positions of contours obtained from video images were used to examine daily beach response to wave characteristics between successive surveys the more intense and frequent storm events in winter than in summer resulted in a seasonal change from a wide beach with a small volume at the end of winter to a narrow large volume beach in summer the seasonal pattern in beach width resulted from the cross shore sediment exchange between the supratidal and lower intertidal part of the beach in contrast to the coupling between beach behaviour and wave characteristics on a seasonal scale beach variability between successive surveys was unrelated to day to week averages of the preceding offshore wave conditions partly due to the precise timing of a storm relative to the two survey moments moreover daily variability determined from the video images showed that differing antecedent morphology to storms and alongshore variations in beach morphology contributed to spatially and temporally variable beach response

significance of different modes of rhizolith preservation to interpreting paleoenvironmental and paleohydrologic settings examples from paleogene paleosols bighorn basin wyoming u s a abstract different modes of preservation of root traces rhizoliths provide information on soil moisture regimes in alluvial paleosols in the paleogene fort union and willwood formations of the bighorn basin wyoming u s a this paper links different styles of rhizolith preservation to paleosols whose other pedogenic attributes provide information on ancient soil drainage consequently the paleodrainage significance of different rhizolith preservation patterns is established more confidently rhizoliths consisting of elongate gray mottles rhizohaloes with red rims are common in relatively well drained red paleosols the gray zones are depleted of iron fe whereas the color of the rims indicates hematite accumulation these features are typical of surface water gley processes that caused fe and manganese mn to move from the root channel outward to the soil matrix calcareous rhizocretions either calcareous tubular concretions or micro accumulations of carbonate within gray rhizotubules are also common in moderately well drained red paleosols more poorly drained purple paleosols also have rhizoliths consisting of fe depletion zones however the rhizohaloes are surrounded by yellow brown goethite rims rather than red hematitic rims in many paleosols the red and yellow brown accumulation rims were partly removed by continued depletion producing abundant irregular shaped mottles the nature of the rhizohalo and the color of the fe oxide rim provide information about the intensity of gleying that a paleosol underwent the poorly drained paleosols also show rhizoliths preserved as goethite accumulations contained within gray depletion zones indicating movement of reduced fe from the matrix towards the root channel probably as a result of groundwater gley processes the goethite accumulations are intermingled locally with lignite representing preservation of the root organic material some rhizoliths are preserved as tube shaped concentrations of small 0 1 0 2 mm diameter black spheres whose color indicates a mix of mn and fe oxides these are most common in paleosols with low chroma gray matrix colors indicating very poor drainage the very poorly drained paleosols also show rhizoliths preserved in jarosite which is an oxidation product of pyrite careful observational and geochemical analysis of rhizoliths which are common in continental deposits can help produce a clearer and more thorough interpretation of ancient drainage conditions information about degree of ancient soil wetness or moisture is important for understanding past climatic conditions and for reconstructing terrestrial paleolandscapes

organisational controls typologies and time scales of paraglacial gravel dominated coastal systems abstract the fundamental controls on the initiation and development of gravel dominated deposits beaches and barriers on paraglacial coasts are particle size and shape sediment supply storm wave activity primarily runup relative sea level rsl change and terrestrial basement structure primarily as it affects accommodation space this paper examines the stochastic basis for barrier organisation as shown by variation in gravel barrier architecture we recognise punctuated self organisation of barrier development that is disrupted by short phases of barrier instability the latter results from positive feedback causing barrier breakdown when sediment supply is exhausted we examine published typologies for gravel barriers and advocate a consolidated perspective using rate of rsl change and sediment supply we also consider the temporal variation in controls on barrier development these are examined in terms of a simple behavioural model barch for prograding gravel barrier architecture and its sensitivity to such controls the nature of macroscale 10 2 10 3 years gravel barrier development including inherited characteristics that influence barrier genesis as well as forcing from changing rsl sediment supply headland control and barrier inertia is examined in the context of long surviving barriers along the southern england coastline

deposition and diagenesis of clinton ironstones silurian in the appalachian foreland basin of pennsylvania clinton ironstones mid silurian on the southeastern margin of the appalachian foreland basin in central pennsylvania consist largely of skeletal grainstone storm beds whose skeletal fragments are extensively impregnated and replaced by ferric oxide other forms of iron mineralization consist of ooids superficial ooids cavity fillings and cements composed of ferric oxide and or chamositic clay and two generations of iron rich carbonate spar true oolite is rare small proportions of ferruginized grains are present in coarse lags at tops of some small scale 1 to 5 m coarsening upward sequences which are the record of mid shelf shoals from which the skeletal grainstone storm beds were derived ooids and superficial ooids are likely to have formed in dysaerobic conditions where the pycnocline of a highly stratified sea intersected shoal flanks ferrous iron from anaerobic deeper waters precipitated on quartz and skeletal fragment nuclei in weakly reducing conditions with episodic gentle agitation several stages of early diagenetic ferruginization affected skeletal grainstone storm beds and sequence capping coarse lags chamositic clay precipitated in pores and cavities of skeletal fragments within quartz sand adjacent to crinoid ossicles and as bed parallel connectors of large skeletal fragments as diagenesis progressed with further burial many skeletal fragments were extensively replaced by ferric oxide most chamositic clay altered to ferric oxide other chamositic clay matured from berthierine to chamosite and clusters of bladed specularite replaced parts of primary grains and secondary carbonate cements paleomagnetic and fluid inclusion analysis indicates that many late diagenetic changes took place at elevated temperatures during deen burial in an early phase of the alleghanian orogeny

a subaerial arthropod trackway from the upper silurian clam bank formation of newfoundland trackways are reported for the first time from silurian rocks in newfoundland they occur in the clam bank formation of the port au port peninsula at least one of the trackways represents one of the earliest known occurrences of a large subaerial arthropod trace fossil it is preserved in hyporelief in a red fine grained sandstone the trackway diplichnites dawson 1873 consists of two parallel series of clearly defined imprints it is attributed to a myriapod similar to the lower devonian eoarthropleura the sandstone contains halite pseudomorphs that indicate that the sediment horizon had been subject to desiccation immediately prior to the formation of the trackway the arthropod walked on a red siltstone deposited in an alluvial flats environment analysis of the trackway suggests that the arthropod was approximately 23 cm long and had 17 pairs of walking appendages it appears that a high geared gait with a ratio of forestroke backstroke of 8 2 was used in walking across the substrate that is ap

pedogenic slickensides indicators of strain and deformation processes in redbed sequences of the appalachian foreland pedogenic slickensides are convex concave slip surfaces that form during expansion contraction in expansive clay soils such as vertisols in the central appalachians they occur near the tops of fining upward cycles in paleozoic redbeds such as the bloomsburg catskill and mauch chunk formations pedogenic slickensides are found in association with other pedogenic or paleosol features such as clay skinned peds in situ calcareous nodules and root impressions repeated movements along these shear planes during pedogenesis produce strongly aligned clay particles adjacent to pedogenic slickensides as a result they are preserved as discrete fractures throughout diagenesis compaction and superimposed tectonic deformation during whole rock deformation pedogenic slickensides segregate penetratively deformed rocks into independent foliated packets and serve as discontinuities that are followed by later structural features because the original morphology of pedogenic slickensides is known they can be used as crude strain markers

a simple model for the spatially variable coastal response to hurricanes abstract the vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm induced water levels to those of the dune or berm a simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50 km stretch of the north carolina coast to the landfalls of hurricane bonnie on august 27 1998 and hurricane floyd on september 16 1999 maximum total water levels at the shoreline were calculated as the sum of modeled storm surge astronomical tide and wave runup estimated from offshore wave conditions and the local beach slope using an empirical parameterization storm surge and wave runup each accounted for 48 of the signal the remaining 4 is attributed to astronomical tides indicating that wave driven process are a significant contributor to hurricane induced water levels expected water levels and lidar derived measures of pre storm dune and berm elevation were used to predict the spatially varying storm impact regime swash collision or overwash predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall the storm averaged mean accuracy of the model in predicting the observed impact regime was 55 4 a significant improvement over the 33 3 accuracy associated with random chance model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84 2 and 89 7 for hurricanes bonnie and floyd respectively the model not only allows for prediction of the general coastal response to storms but also provides a framework for examining the longshore variable magnitudes of observed coastal change for hurricane bonnie shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore swash regime during hurricane floyd this pattern became more pronounced as magnitudes of change were four times greater within the overwash regime than in the swash regime comparisons of pre storm topography to a calm weather survey collected one year after hurricane floyd s landfall show long term beach volume loss at overwash locations here the volume of sand eroded from the beach was balanced by the volume of overwash deposits indicating that the majority of the sand removed from the beach was transported landward across the island rather than being transported offshore in overwash locations sand was removed from the nearshore system and unavailable for later beach recovery resulting in a more permanent response than observed within the other regimes these results support the predictive capabilities of the storm scaling model and illustrate that the impact regimes provide a framework for explaining the longshore variable coastal response to hurricanes

non marine arthropod traces from the subaerial ordovician borrowdale volcanic group english lake district arthropod trace fossils are described from the borrowdale volcanic group a sequence otherwise devoid of faunal evidence two forms both made by the same probably myriapod like organism are assigned to the ichnogenera diplichnites and diplopodichnus the lithologies preserving the trace fossils are non marine and may have been deposited in a freshwater lacustrine environment some of the traces were probably made in temporarily emergent conditions the change from one form of trace to the other reflects drying out of the substrate the trace fossils probably record some of the earliest freshwater arthropods before the widespread colonization of land by the group