rock coast inheritance an example from galicia northwestern spain a shore platform on the western coast of galicia in northwestern spain has been inherited from interglacial stages when sea level was similar to today the wide gently sloping intertidal platform is backed in places by supratidal rock ledges and in other places by a steeper and narrower supratidal ramp the gradient of the intertidal platform is consistent with the relationship between platform gradient and tidal range but the slope of the ramp is much too high the abandoned and degraded sea cliff is grass covered along most of this coast and the ledges and the ramp which extend up to several metres above the highest tides are covered by lichen and in places by salt tolerant plants radiocarbon dated sediments in the cliff which range up to 36 000 years in age lie on top of an ancient beach deposit the former beach remnants of which are found in situ on the ramp and rock ledges as well as two caves that are filled with the dated sediments are probably last interglacial in age the morphological and sedimentary evidence suggests that the supratidal ramp and ledges were also formed during the last interglacial stage whereas the wider intertidal platform is probably the product of several older interglacials when sea level was generally similar to today a general model is proposed for the inheritance of shore platforms in macro and microtidal environments copyright 1999 john wiley sons ltd

downwearing rates of vertical limestone surfaces in the intertidal zone gulf of trieste italy abstract in 2007 we installed seven micro erosion meter stations on a vertical limestone slab located in the intertidal zone in the gulf of trieste italy in order to observe rock surface changes at elevations ranging between 0 75 m and 0 75 m m s l furlani et al 2010 in this paper we present the micro erosion metre mem data for most months between february 2008 and may 2013 and the traversing micro erosion metre tmem data collected twice a year since 2007 the mem and tmem data were consistent and indicated that the mean lowering rate ranged between 0 007 mm yr and 0 205 mm yr and 0 001 mm yr and 0 260 mm yr according to the elevation of the stations maximum downwearing rates were observed in the mid lower intertidal zone and decreased upward and downward the natural trend of erosion started in 2010 after 2 years of exposure when the slab formerly smoothed and not colonized by marine organisms started to be acclimated to the local environment after 2010 the erosion rate increased to a maximum of 0 31 mm yr this value can be more representative for long term studies and is similar to the downwearing rates locally collected on natural limestone surfaces this dataset represents the first collection of downwearing rates mainly measured using mems but also tmems on vertical limestone surfaces in an intertidal zone and provides interesting new information for addressing the debate on notch genesis and development the shape of a tidal notch has been found to be consistent with the distribution of erosion rates along the slab even if the present day notch was not surveyed in the gulf of trieste due to the local tectonic subsidence

the effect of holocene changes in relative sea level on the morphology of rocky coasts abstract a mathematical wave and weathering model was used to study the effect of holocene changes in relative sea level rsl on rock coast development model runs were made for fast and slow eroding coasts in macro and mesotidal environments using holocene rsl records from sweden northeastern usa southwestern britain central japan western africa and southern australia a further series of otherwise identical runs were made with constant sea level changes in rsl determined the amount of time that marine processes have operated within the modern intertidal zone and rates of wave attenuation and erosion continue to be influenced by subtidal morphology that developed in most areas when rsl was rising to its present level the model suggested that although tidal range is also important holocene rsl changes promoted subhorizontal platform development in australasia and over much of the southern hemisphere and sloping platforms over much of the northern hemisphere shore platforms may have been partly inherited from earlier periods in the holocene when rsl was similar to today s nevertheless most platforms continue to be eroded at all tidal levels where geological and wave conditions are less favourable erosion in the lower intertidal zone has essentially terminated in areas where rsl rose to its present position whereas erosion only occurs today in the lower intertidal zone in places where rsl rose to above its present level in the middle holocene

scale issues in weathering studies a review of the major scale issues in weathering studies reveals concerns over the fundamental spatio temporal distributions of weathering phenomena as well as issues of upscaling microscope based observations and linking different scales of observations in explanations of landform development various strategies are proposed which can be used to tackle these issues many rooted in non linear dynamical systems ideas as an initial step spatio temporal scale distributions are estimated here for weathering processes landforms and controls based on a range of empirical data two case studies of phytokarst in grand cayman and blistering and scaling of building stones are presented to illustrate the types of data that might be used to establish more convincing scale linkages in weathering investigations

hydrodynamic constraints and storm wave characteristics on a sub horizontal shore platform few studies of wave processes on shore platforms have addressed the hydrodynamic thresholds that control wave transformation and energy dissipation especially under storm conditions we present results of a field experiment conducted during a storm on a sub horizontal shore platform on the east coast of auckland new zealand small 2 5 times the gravity wave height 0 05 0 33 hz is necessary for waves to propagate onto the platform without breaking on the platform surface the wave height is a direct function of water depth with limiting maximum wave height to water depth ratios of 0 55 and 0 78 at the centre of the platform and cliff toe respectively a relative platform edge submergence water depth water height ratio threshold of 1 1 is identified below which infragravity 0 05 hz wave energy dominates the platform energy spectra and above which gravity waves are dominant infragravity wave height transformation across the platform is governed by the relative platform edge submergence finally the paper describes the first observations of wave setup on a shore platform during the peak of the storm wave setup on the platform at low tide 0 21 m is consistent with measurements from planar sandy beaches but at higher tidal stages the ratio between incident wave height and maximum setup was lower than expected copyright 2014 john wiley sons ltd

modeling the development of wave cut shore platforms abstract a mathematical model was used to investigate the development of wave cut shore platforms with constant sea level the model considered the effects of deep water wave height spectra period and wavelength breaker height and depth breaker type the width and bottom roughness of the surf zone the gradient of the submarine slope an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot intertidal erosion rates were calculated according to the force of the surf reaching the shoreline whereas submarine erosion rates were determined using a depth decay variable each of the two hundred and fifty model runs consisted of 300 000 iterations platform width increased and gradient progressively decreased through model runs and states of static equilibrium were attained by the end of one hundred and nine runs when the wave induced force at each point in the intertidal zone had became too weak to continue eroding the rock runs with mesotidal spring tidal range 3 m generally produced subhorizontal platforms with cliff platform junctions at the mean low water neap tidal level a greater variety of profiles was produced in runs with macrotidal spring tidal ranges 9 m although almost 30 of these runs produced gently sloping platforms with average gradients of only 0 3 about two thirds of the simulated profiles had average gradients ranging from about 1 to 3 simulated platform width increased with tidal range and decreased with the rate of submarine erosion rock resistance the roughness or irregularity of the platform surface the amount and persistence of the cliff foot debris and wave period because higher waves break in deeper water than lower waves there was no consistent relationship between simulated platform width and wave height

the timing of the last glacial maximum in australia abstract late pleistocene glaciation of australia was restricted to the snowy mountains and the tasmanian highlands glaciers were most extensive in tasmania where ice caps formed on the central plateau and west coast ranges and systems of valley and cirque glaciers formed on surrounding mountains to investigate the timing of maximum glacier advance during the last glacial maximum lgm we dated boulders on 18 moraines in 8 glaciated areas using cosmogenic 36cl and 10be we sampled moraines deposited by cirque and valley glaciers in a range of climate types and lithologies over a 7 latitudinal and a 1430 m altitudinal transect exposure ages for lgm moraine boulders group tightly in the range 17 20 ka boulders from the hamilton moraine often treated as the lgm type moraine range in age from 190 350 ka indicating that it was deposited well before the last glaciation collectively the exposure ages show that southeastern australia was glaciated briefly during and after the lgm and deglaciated well before the holocene ice retreated from the terminal moraines after the period of coldest sea surface temperatures in the southwest pacific ocean no evidence was found for readvance of glaciers during the antarctic cold reversal or the younger dryas period

shore platform morphology on a rapidly uplifting coast wellington new zealand the coast of wellington new zealand is tectonically active and contains a series of uplifted and contemporary shore platforms that are developed in triassic greywacke the platform profiles are rugged with relief of metre scale common the surveyed platforms were formed at and at two distinct levels 1 1 5 and 2 2 5 m above mean sea level they range in width up to 70 m and are highly fractured with fracture densities in excess of 20 sol m2 common the rate of development of these platforms is rapid with lateral erosion rates of up to 0 15 m sol yr calculated allowing platform development to occur over centennial scales even given this rapid development continued instantaneous uplift of the coast has meant they are unable to reach an equilibrium state whereby the effectiveness of wave processes in removing material is reduced by platform extension the co seismic uplift means that the rear of the platforms is raised beyond the limits of marine process and has become an area of deposition although no direct process measurements were made the highly fractured nature of the bedrock appears to play a major role in platform evolution with wave processes being easily able to pluck blocks as evidenced by fresh erosion scars and active gravel beaches at the rear of many platforms this coast therefore represents an extremely dynamic youthful shore platform environment where the processes of marine abrasion can be observed over historical timescales copyright 2005 john wiley sons ltd

block removal and step backwearing as erosion processes on rock shore platforms a preliminary case study of the chalk shore platforms of south east england shore platforms frequently exhibit steps or risers facing seaward landwards or obliquely across shore a combination of soft copy photogrammetry ortho rectification geo referencing and field measurement of step height are linked in a gis environment to measure step retreat on chalk shore platforms at sample sites in the south of england over two periods 19732001 20012007 the methods used allow for the identification delineation and measurement of historic change at high spatial resolution the results suggest that while erosion of chalk shore platforms by step backwearing is highly variable it appears to be of similar magnitude to surface downwearing of the same platforms measured by micro erosion meters mems and laser scanning in a range equivalent to 00006 00050my 1 of surface downwearing this equates to annual chalk volume loss from the platforms by the two erosion processes combined of between 00012m3m 2 and 00100m3m 2 results from the more recent years data suggests that step retreat has variability in both space and time which does not relate solely to climatic variability the results must be viewed with caution until much larger numbers of measurements have been made of both downwearing and step erosion at higher spatial and temporal resolution

micro erosion meter measurements of rock wear on the otway coast of southeast australia abstract the use of the micro erosion meter mem has been refined by providing 1 a base plate on which to check the relationship of legs and probe and 2 a micrometer level to check the relationships of the three studs countersunk in the rock at each site along 50 km of the otway coast lines of mem stations were installed across shore platforms normal to the shore and surveyed to mean low water readings were made bimonthly from 1978 to 1980 average site downwear ranged from 0 02 to 1 8 mm yr 1 according to rock type and the amount of exposure to the almost continuous swell waves the results of this study combined with other information available are used to discuss the origin and evolution of otway coastal morphologies

long term shore platform surface lowering rates revisiting gill and lang after 32 years abstract in 1978 e d gill and j g lang installed 53 micro erosion meter mem sites on shore platforms along the otway coast in south eastern australia surface lowering rates were originally determined from 2 yr of measurements 1979 and 1980 and showed that the mean annual rate of lowering from all sites was 0 37 mm yr 1 we re measured these mem sites 32 yr after the first set of readings were taken in february 1979 we relocated 49 of the original 53 bolt sites and were able to measure 45 of them from the sites we measured the mean annual rate of shore platform lowering was 0 31 mm yr 1 rates of surface lowering on shore platforms are commonly reported from studies of only two or three years and only one other record exceeds 30 yr kaikoura peninsula nz 1 09 mm yr 1 in that case fewer than half of the original bolt sites were functioning because erosion had removed bolts along the otway coast rates of erosion are much slower hence the greater number of still readable sites after 32 yr compared to other micro erosion meter studies the rates reported here are at the lower end of the range of values from around the world but nevertheless consistent with rates from the otway coast and others in similar lithology we found no statistical difference between erosion rates calculated over 2 yr 1979 to 1980 and 32 1979 to 2011 years supporting the view that shore platform lowering rates measured over 2 yr are representative of decadal scales

towards an improved understanding of erosion rates and tidal notch development on limestone coasts in the tropics 10 years of micro erosion meter measurements phang nga bay thailand knowledge and understanding of shore platform erosion and tidal notch development in the tropics and subtropics relies mainly on short term studies conducted on recently deposited carbonate rocks predominantly holocene and quaternary reef limestones and aeolianites this paper presents erosion rates measured over a 10 year period on notches and platforms developed on the permian ratburi limestone at phang nga bay thailand in so doing it contributes to informing a particular knowledge gap in our understanding of the erosion dynamics of shore platform and tidal notch development in the tropics and subtropics notch erosion rates on relatively hard ancient limestones measured directly on the rock surface using a micro erosion meter mem over time periods of a decade or more the average intertidal erosion rate of 0 231 mm yr is lower than erosion rates measured over 2 3 years on recent weaker carbonate rocks average erosion rates at phang nga vary according to location and site and are in rank order from highest to lowest mid platform 0 324 mm yr notch floor 0 289 mm yr rear notch wall 0 228 mm yr lower platform 0 140 mm yr notch roof 0 107 mm yr and supratidal 0 095 mm yr the micro relief of the eroding rock surfaces in each of these positions exhibits marked differences that are seemingly associated with differences in dominant physical and bio erosion processes the results begin to help inform knowledge of longer term shore platform erosion dynamics models of marine notch development and have implications for the use of marine notches as indicators of changes in sea level and the duration of past sea levels copyright 2014 john wiley sons ltd

reconceptualising the role of organisms in the erosion of rock coasts a new model attempts to understand the morphodynamics of rock coasts focus on the nature and rate of erosion and how this influences the evolution of coastal profiles over century to millennial timescales biological contributions to this process are often ignored or treated in a rather simplistic way as merely producing microscale decreases in rock strength using a combination of field observations and literature review we address two key issues hampering a more rounded assessment of biological impacts erosion of coastal rocks firstly we reconceptualise the biological contributions to erosion of rock coasts into direct and facilitative types and secondly we discuss the need for more appropriate reporting of rates of bioerosion for direct bioerosion this means clearly documenting the percentage of platform surfaces affected by bioerosive agents and quantifying the volume of material eroded and the amount of fine sediment produced for facilitative bioerosion we must quantify the roles of biota in changing the material properties of rocks creating or altering surface morphologies and or weakening joint boundaries in this way facilitative bioerosion is one of several processes mediating geomorphic alteration of rock surfaces contributing to the production of landforms and or reducing the resisting force of rock subsequently we build on these ideas to produce a new conceptual model which more accurately portrays the multiple and cross scalar ways that biological processes notably bioerosion influence the resistance of coastal rocks to erosive forces such a model provides a stronger basis for numerical modelling and understanding the morphodynamics of rock coasts in the future and allows a quantitative assessment of the role of biota

the micro erosion meter use and limitations detection of anomalies in measurements of low rates of limestone surface lowering with a traversing micro erosion meter mem led to temperature controlled laboratory and field investigations of some sources of error in the method regressions for the correction of temperature change in the instrument and in the stud rock interface were obtained probe erosion tests permitted a correction to be devised and also provided information whereby a measure of operational irregularity was adopted corrections and error terms were applied to field measurements from two southern new south wales karsts and a collection of australian limestone slabs exposed at one site examination of these results and of published mem rates from other parts of the world validated the mem method marine platforms are lowered at such gross rates that these error sources may be neglected there however limestone lowering in terrestrial environments cannot be assumed to proceed at rates which permit this and recommendations are made about procedures to ensure that investigations are prosecuted within the limitations of the method

tidal notches a sea level indicator of uncertain archival trustworthiness abstract in this paper after a short summary on the processes and rates of bioerosion that contribute to the deepening of a tidal notch profile some mediterranean case studies are presented where a tidal notch is prevented either from forming or from being preserved furthermore as shown also in a complementary paper the recent global sea level rise is preventing the development of new tidal notches in the present mid littoral zone this very useful sea level indicator of past temporary standstills of the relative sea level in carbonate rock areas is of great value in assisting interpretations of relative sea level change in locations where it is preserved the possibilities of absence of formation or of preservation however imply that it should be interpreted carefully before reconstructing local relative sea level histories in particular the lack of fossil tidal notches cannot be relied upon to interpret the absence of past periods of relative sea level stabilization

cosmogenic dating of fluvial terraces fremont river utah absolute dating of river terraces can yield long term incision rates clarify the role of climate in setting times of aggradation and incision and establish the rates of pedogenic processes while surface exposure dating using cosmogenic 10be and 26al would seem to be an ideal dating method the surfaces are composed of individual clasts each with its own complex history of exposure and burial the stochastic nature of burial depth and hence in nuclide production in these clasts during exhumation and fluvial transport and during post depositional stirring results in great variability in clast nuclide concentrations we present a method for dealing with the problem of pre depositional inheritance of cosmogenic nuclides we generate samples by amalgamating many individual clasts in order to average over their widely different exposure histories depth profiles of such amalgamated samples allow us to constrain the mean inheritance to test for the possible importance of stirring and to estimate the age of the surface working with samples from terraces of the fremont river we demonstrate that samples amalgamated from 30 clasts represent well the mean concentration depth profiles show the expected shifted exponential concentration profile that we attribute to the sum of uniform mean inheritance and depth dependent post depositional nuclide production that the depth dependent parts of the profiles are exponential argues against significant post depositional displacement of clasts within the deposit our technique yields 10be age estimates of 60 9 102 16 and 151 24 ka for the three highest terraces corresponding to isotope stages 4 5d and 6 respectively the mean inheritance is similar from terrace to terrace and would correspond to an error of 30 40 ka if not taken into account the inheritance likely reflects primarily the mean exhumation rates in the headwaters of order 30 m ma

measuring erosion with the micro erosion meter contributions to understanding landform evolution abstract we review the contribution made to understanding landform evolution through the use of the micro erosion meter mem and the variant the traversing micro erosion meter tmem the mem has allowed the direct measurement of bedrock erosion in terrestrial and coastal settings as well as of building stone as recorded in mem measurements world wide the average rate of surface lowering on shore platforms is 1 486 mm a 1 and on terrestrial rock surfaces measured lowering rates are on average 0 903 mm a 1 reported means obscure significant variation in rates from a range of environmental settings and lithologies the mem has in a number of examples allowed the identification of the contribution of individual processes in polygenetic settings particularly in shore platform studies the dynamic nature of rock weathering has been highlighted where the tmem has revealed rock surfaces swelling and contracting at time scales ranging from hours to years the mem will continue to provide useful data on erosion rates and processes but the most fruitful investigations will be those that combine the t mem with other techniques that transcend time and space scale issues in erosion and process measurement

modelling the effect of waves weathering and beach development on shore platform development a mathematical model was used to study shore platform development mechanical wave erosion was dependent on such variables as tidal range wave height and period breaker height and depth breaker type surf zone width and bottom roughness submarine gradient rock resistance and the elevational frequency of wave action within the intertidal zone also included were the effects of sand and pebble accumulation cliff height and debris mobility and downwearing associated with tidal wetting and drying the occurrence location and thickness of beaches often depended on initially quite minor variations in platform morphology but owing to their abrasive or protective effect on underlying rock surfaces they were able to produce marked differences in platform morphology generalizations are difficult but the model suggests that platform gradient increases with tidal range platform width also increases with tidal range with slow downwearing but it decreases with fast downwearing platform gradient decreases and width increases with wave energy and decreasing rock resistance and platform roughness with low tidal range platform gradient is generally lower and platform width greater with beaches of fine sand than with gravel but the relationship is more variable with a high tidal range platform width increases and platform gradient decreases with the rate of downwearing on bare surfaces particularly in low tidal range environments but the pattern is less clear on beach covered platforms platforms with large amounts of beach sediment tend to be narrower and steeper than bare platform surfaces platform gradient increases and platform width decreases with increasing cliff height and with decreasing cliff debris mobility copyright 2005 john wiley sons ltd

experimental frost and salt weathering of chalk i experiments are described in which chalk cubes were soaked in solutions of either sodium chloride sodium sulphate or magnesium sulphate at concentrations of 5 5 per cent and 12 5 per cent or in a mixed solution of sodium chloride and sodium sulphate or in distilled water after removal of excess liquid the cubes were subjected to six freeze thaw cycles with temperatures ranging from either 15 to 10 c or 15 to 30 c the results confirm that frost weathering can be enhanced by the presence of certain salts but the extent of weathering was much less than that previously reported for samples frozen totally immersed in the same liquids evidence is presented which suggests that salt crystallization is the major weathering process operative when non immersed samples are frozen but a combination of frost and salt weathering operates when fully immersed samples are frozen

coastal staircase sequences reflecting sea level oscillations and tectonic uplift during the quaternary and neogene many coasts feature sequences of quaternary and neogene shorelines that are shaped by a combination of sea level oscillations and tectonics we compiled a global synthesis of sea level changes for the following highstands mis 1 mis 3 mis 5e and mis 11 also we date the apparent onset of sequences of paleoshorelines either from published data or tentatively extrapolating an age for the uppermost purported oldest shoreline in each sequence including the most documented mis 5e benchmark we identify 926 sequences out of which 185 also feature holocene shorelines six areas are identified where elevations of the mis 3 shorelines are known and 31 feature elevation data for mis 11 shorelines genetic relationships to regional geodynamics are further explored based on the elevations of the mis 5e benchmark mean apparent uplift rates range from 0 01 0 01 mm yr hotspots to 1 47 0 08 mm yr continental collision passive margins appear as ubiquitously uplifting while tectonic segmentation is more important on active margins from the literature and our extrapolations we infer ages for the onset of formation for 180 coastal sequences sea level fingerprinting on coastal sequences started at least during mid miocene and locally as early as eocene whether due to the changes in the bulk volume of seawater or to the temporal variations in the shape of ocean basins estimates of eustasy fail to explain the magnitude of the apparent sea level drop thus vertical ground motion is invoked and we interpret the long lasting development of those paleoshore sequences as the imprint of glacial cycles on globally uplifted margins in response to continental compression the geomorphological expression of the sequences matches the amplitude and frequency of glacial cyclicity from middle pleistocene to present day moderately fast 100 000 yrs oscillating sea levels favor the development of well identified strandlines that are distinct from one another pliocene and lower pleistocene strandlines associated with faster cyclicity 40 000 yrs are more compact and easily merge into rasas whereas older cenozoic low frequency eustatic changes generally led to widespread flat lying coastal plains

evidence for active retreat of a coastal cliff between 3 5 and 12 ka in cassis south east france this study on the cap canaille cliff n 43 19 e 5 55 cassis se france combines cosmic ray exposure cre dating using two cosmogenic nuclides in situ produced 10be and 36cl and morphological analyses to gain a better understanding of a major coastal cliff collapse event morphological analysis reveals evidence cliff morphology presence of big collapsed blocks of a possible major collapse of cap canaille in the past aerial pictures and gis software allow estimation of a potential collapsed volume of at least 7 106 m3 of which roughly 6 106 m3 fell into the mediterranean sea in situ produced 10be and 36cl concentrations were measured in samples collected on collapsed block surfaces and in situ produced 10be was measured along the cliff face to date the last major collapse event statistical analysis of the cre ages calculated from cliff samples shows that these ages cluster around 3 5 and 6 7 ka suggesting the existence of a two step past major collapse the older ages obtained at 9 and 12 ka coincides with the approach of present day sea level implying a control of sea level on the cliff retreat the cre ages calculated from collapsed block samples are more scattered toward younger ages due to several geomorphological factors the estimated collapsed volume associated with the last major collapse around 3 5 ka seems sufficient to have triggered a local tsunami in the cassis bay if it fell at once into the sea

decadal scale micro erosion rates on shore platforms abstract knowledge of the long term rates of erosion of shore platforms are needed to assist modeling platform development understand rates and modes of development and decipher issues of inheritance from former sea level few studies report rates from more than 2 years of monitoring we report decadal scale erosion rates using both a micro erosion meter and a traversing micro erosion meter with measurements from 30 years and 10 years respectively gross mean surface lowering rates measured over 10 years with a traversing micro erosion meter were 0 901 s e 0 116 mm yr compared with 1 130 s e 0 217 mm yr over two years over thirty years 1973 2003 12 micro erosion meter sites provide a mean surface lowering rate of 1 09 s e 0 126 mm yr compared to 1 43 s e 0 128 mm yr calculated over twenty years 1973 1993 from 15 bolt sites and 1 53 s d 1 45 mm yr from 31 bolt sites rates calculated over longer time periods are reduced compared to short term rates as a result of faster eroding bolt sites being removed from the data set comparison of means between short and long time periods for existing bolts show no significant difference that is short term measurements over two years are representative of decadal scale erosion rates in fact decadal scale rates may under represent rates of platform development because of the loss of faster eroding bolt sites the loss of such bolts means that obtaining long term erosion rates is problematic future modeling of shore platform development can use mem rates with more certainty but we recommend using higher rates from shorter term studies unless longer records are complete

cosmogenic nuclide concentrations in episodically eroding surfaces theoretical results the buildup of cosmogenic nuclides in an eroding surface can be used to infer erosion rates and exposure ages this situation is often modelled by assuming that the erosion rate is constant in time in many cases however the erosion is episodic surface denudation occurs by the spalling off of slabs of rock at discrete times we consider a stochastic model of such exfoliation processes and compute the expected behavior of the cosmogenic nuclide concentration we also consider a nonstochastic model in which the exfoliation events occur at regularly spaced intervals these two models represent extreme end members of the episodic spallation scenarios in the first the spallation events are uncorrelated in time while in the second they are tightly correlated understanding how the nuclide concentration is related to the timing and the magnitude of these events is important in making geologic inferences

long term shoreline retreat rates on whidbey island washington usa abstract long term retreat rates of puget sound s unconsolidated sediment shorelines have been difficult to quantify and little systematic research has been completed to constrain retreat in this area we put forward a new application of cosmogenic 10be exposure dating to assess long term shoreline retreat on whidbey island wa by dating lag boulders exposed on the shore platform as the shoreline erodes production of 10be in shoreline boulders is modulated by both tidal submergence and topographic shielding from the retreating bluff by modeling the combined effect of these variables on 10be production the timing of exposure can be determined and used to calculate long term 103 104 yr bluff retreat rates in rare cases retreat rates are underestimated due to inherited 10be within the study area average retreat rates ranged between 0 and 8 cm yr 1 our results demonstrate the utility of cosmogenic nuclides for determining long term shoreline retreat rates in areas with thick sediment cover where large numbers of samples can be collected and where the pre depositional history of the boulders is uncomplicated

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

statistical analysis of the significance of site topography and erosion history on erosion rates on intertidal shore platforms kaikoura peninsula south island new zealand sites with five periods of consecutive measurements from the kaikoura peninsula data were used to assess the influence of erosional history and surface topography upon subsequent erosion rates analysis of multilevel models suggests that initial erosion rates and initial surface topography have a significant but decreasing influence upon subsequent erosion rates surface topography and erosion rates immediately prior to each measurement period have a consistent positive and negative relationship respectively to erosion rates in the subsequent measurement periods these data suggest that there is a short term memory influencing erosion rates at any specific measurement period use of traversing microerosion meter data may however not be the most appropriate means of analysing the causes of the variance of erosion at the intra site scale

evolution and inheritance of a rock coast western galicia northwestern spain there is increasing evidence that shore platforms and other elements of rock coasts may be inherited at least in part from interglacial stages when sea level was similar to today s most of this evidence which includes ancient beaches and datable terrestrial deposits has been obtained from areas of resistant slowly eroding rock where the platforms often appear to be much too wide to have developed since the sea reached its present level it is much more dif cult to demonstrate that inheritance has occurred in areas of weaker rock which generally lack any datable material the coast of western galicia in northwestern spain has shore platforms in igneous and metamorphic rocks that were deeply weathered during the tertiary these platforms are closely associated with ancient beaches from the last interglacial stage and associated periglacial and uvio nival deposits that covered and fossilized most of the eemian platforms and cliffs during the late middle and late weichselian glacial stage the sedimentary processes and the thickness and facies of the sediments were determined by the height aspect and gradient of the coastal mountains and their distance from the coast radiocarbon dating sedimentary analysis and platform morphology indicate that the shore platforms of galicia have been inherited from at least the last interglacial stage they were fossilized in places beneath thick weichselian deposits and then exhumed during the holocene transgression the abundant evidence for inheritance in galicia has important implications for other coasts in fairly weak rocks where such evidence is generally lacking copyright 2003 john wiley sons ltd

shore platform erosion and evolution implications for cosmogenic nuclide analysis abstract determining rates and modes of shore platform development and the age of associated elements are among the greatest challenges facing rock coast researchers today these coasts generally lack dateable deposits but cosmogenic nuclide analysis cna can be applied directly to bare rock surfaces to estimate erosion rates or the time that a surface has been exposed over millennial timescales therefore this technique has the potential to revolutionize current theories on rock coast evolution and modes of development because environmental and geomorphological factors affect rates of nuclide accumulation and retention however the results of cna analysis are dependent on the validity of the theoretical models that have to be employed according to the particular application among the important assumptions that may be made are those concerned with shading tidal immersion beach sediment covers and other factors that influence rates of nuclide accumulation and with possible spatial and temporal patterns in shore platform erosion primarily by wave generated backwearing and weathering induced downwearing that reduce nuclide concentrations our lack of understanding of the factors that control these variables and in particular shore platform erosion which is the subject of this review has important implications for modelling rock coast evolution assessing the possible contribution of inheritance and dating especially by cna the occurrence of important formative events

icesat waveform measurements of within footprint topographic relief and vegetation vertical structure 1 the ice cloud and land elevation satellite icesat mission determines land surface vertical structure within laser footprints due to topographic relief and vegetation using received waveforms recorded by the geoscience laser altimeter system glas in low relief areas with tree cover the waveforms and derived elevation products provide useful biophysical parameters including maximum canopy height crown depth the outer canopy ruggedness and a measure of canopy cover for areas where within footprint topographic relief is large compared to vegetation height interpretation of the waveforms is complex the contribution of canopy and ground to received waveforms is illustrated by comparing them with co located waveforms computed using an instrument model applied to high resolution digital elevation models dems the model includes representations of the transmit pulse s spatial and temporal distributions and the receiver field of view sensitivity and temporal smoothing this provides a means to validate glas waveforms elevation products and footprint geolocation

rates and patterns of bedrock denudation by coastal salt spray weathering a seven year record rapid surface lowering of bedrock is taking place in the supratidal zone by salt spray weathering a seven year run of data demonstrates a mean rate of lowering of 0 625 mm a 1 considerable variation exists in annual point lowering values within measurement sites although between site variation is not significant aggregate year to year variations in surface lowering are not significant spatial variation in individual point values may be compensated by temporal variation over an 11 year period there is a marked summer maximum in surface lowering rate and this is strongly correlated with monthly air temperature spatially and temporally episodic swelling of the rock surface is demonstrated this does not correlate statistically with any available climatic variable and is deemed to be a real and largely stochastic phenomenon it is interpreted as rock bursting at the granular scale due to haloclasty the processes most likely to be responsible for the observed rapid denudation are crystallization and thermal expansion of halite both of which are enhanced by high summer temperatures

modeling the erosion of cohesive clay coasts a model was developed to study the erosion of cohesive clay coasts in macro to non tidal environments the model shares some of the characteristics of previous models including the erosion of bare clay surfaces by wave generated bottom shear stresses and of mobile sediment covered surfaces by abrasion it differs from previous models however in several important ways the morphodynamics of beaches with clay foundations under different wave conditions are based on a previously developed model for beaches on rocky shore platforms sediment thickness along a beach profile is calculated at regular intervals and compared with the maximum thickness that could be moved at that location under prevailing wave conditions wave friction factors are determined where necessary according to the occurrence and morphology of ripples on the bottom in addition to abrasion and the effect of wave induced shear stresses on the clay bottom erosion by stresses generated by wave impact at the bluff foot and on the intertidal platform is calculated using an expression derived from hard rock coastal models tides are represented by their computed tidal duration values the amount of time each year that the water level falls within each 0 1 m vertical interval water depths are modified by wave setup and set down conditions several preliminary model runs were made the profiles were concave in the submarine zone and roughly linear in the intertidal zone equilibrium profiles developed which were maintained as they migrated landwards

geomorphologic equifinality a comparison between shore platforms in hoga kusten and faro sweden and the vale of glamorgan south wales uk this paper presents a case study comparing shore platforms of the same lithology and different rock structures limestone with those of different lithologies but similar rock structures limestone dolerite in wales and sweden results of this study illustrate that different erosion mechanisms i e wave action and ice scour produce similar erosion products and meso scale cm m landforms i e stepped shore platforms in structurally similar lithologies in contrast lithologically similar rocks i e limestones generate different meso scale landforms and shore platform morphologies thus structural controls appear to be more critical than lithological controls in generating meso scale erosion products such as rock blocks in this comparative study the similarities in the meso scale geomorphology appear to be caused by uniform rock structure i e rock hardness joint density spacing of bedding horizontal jointing and the slope and direction of bedding horizontal jointing in relation to the sea blocks produced by the jointing have been eroded by high energy waves in the case of wales and drifting sea ice in the case of one of the swedish sites meanwhile different rock structures in a similar lithology i e limestone resulted in very different landforms under the same environmental conditions as the previous example as such this research also provides observational evidence supporting the concept of equifinality

sea cliff retreat and shore platform widening steady state equilibrium we challenge the notion of steady state equilibrium in the context of progressive cliff retreat on micro tidal coasts ocean waves break at or close to the abrupt seaward edge of near horizontal shore platforms and then rapidly lose height due to turbulence and friction conceptual models assume that wave height decays exponentially with distance from the platform edge and that the platform edge does not erode under stable sea level these assumptions combine to a steady state view of holocene cliff retreat we argue that this model is not generally applicable recent data show that 1 exponential decay in wave height is not the most appropriate conceptual model of wave decay 2 by solely considering wave energy at gravity wave frequencies the steady state model neglects a possible formative role for infragravity waves here we draw attention to possible mechanisms through which infragravity waves may drive cliff retreat over much greater distances and longer timescales than imaginable under the established conceptual model copyright 2013 john wiley sons ltd

field observations of infragravity waves and their behaviour on rock shore platforms infragravity wave igw transformation was quantified from field measurements on two shore platforms on new zealand s east coast making this the first study to describe the presence characteristics and behaviour of igws on rock platform coasts data was collected using a cross shore array of pressure transducers during a 22 hour experiment on oraka shore platform and a 36 hour experiment at rothesay bay shore platform a low pass fourier filter was used to remove gravity wave frequency oscillations allowing separate analysis of igws and the full wave spectrum offshore igw heights were measured to be 7 cm oraka and 9 cm rothesay bay which were 21 oraka and 7 5 rothesay bay the height of incident wave height at the cliff toe significant igw height averaged 15 cm at oraka and 13 cm at rothesay bay this increase in igw height over the platform during both experiments is attributed to shoaling of 40 to 55 over the last 50 60 m before the cliff toe respectively shoaling across the platform was quantified as the change in igw height from the platform edge to cliff toe resulting in a maximum increase of 1 88 and 2 63 on rothesay bay and oraka platforms igw height at the cliff toe showed a strong correlation with incident wave height the proportional increase in igw height shows a strong correlation to water level on each platform the rate of shoaling of long period waves on the shallow horizontal platforms increased at higher water levels resulting in a super elevation in water level at the cliff toe during high tide greater igw shoaling was also observed on the wider oraka shore platform results from this study show the first measurements of igws on shore platforms and identify long wave motion a significant process in a morphodynamic understanding of rock coast copyright 2011 john wiley sons ltd

modelling the quaternary evolution of shore platforms and erosional continental shelves a mathematical model was used to investigate the effect of glacially induced fluctuations in sea level on the evolution of wave cut shore platforms and erosional continental shelves during the quaternary the model used two deep water wave sets which were used to calculate breaker height and depth and the force of the waves at the waterline according to the width and bottom roughness of the surf zone and the gradient of the submarine slope the model also incorporated an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot most runs were made using a sea level model that consisted of 26 glacial cycles from 2 million to 0 9 million years ago and nine of approximately twice the amplitude and wavelength in the last 0 9 million years the model emphasized the dynamic association between the contemporary intertidal platform and the continental shelf both surfaces trend towards a state of static equilibrium under oscillating sea level conditions when attenuated waves are unable to continue eroding the rock if there has not been enough time to reduce the gradient of the shallower portions of the continental shelf however intertidal shore platforms can be in a temporary though possibly long lasting state of dynamic equilibrium the model suggests that most platforms are at least in part inherited from one or in many cases more interglacial stages when sea level was similar to today s copyright 2001 john wiley sons ltd

on the role of discontinuities in mediating shore platform erosion in this paper we quantitatively demonstrate that dominant erosion processes on different shore platforms can be explained in part by geological properties we selected sites with a considerable history of rock coast geomorphology study to evaluate whether geological data can improve our understanding of spatial variations in erosion between sites schmidt hammer tests and discontinuity data were collected on blue lias limestone shore platforms in wales uk and sandstone platforms in victoria australia significant differences in joint spacing persistence of discontinuities and block size were found between the australian and welsh study sites these data were related to evidence of meso scale erosion to examine how geological contingency influences the nature and scale of erosion processes and thresholds this study quantitatively demonstrates that discontinuities play a fundamental role in altering rock resistance the findings of this research have important implications for the design of rock coast erosion studies concerned with measuring rates of change and determining the relative contributions of different processes to platform development

modelling tidal notch formation by wetting and drying and salt weathering abstract the formation and morphology of marine notches formed by tidal wetting and drying and salt weathering was modelled for 6 micro to megatidal environments the model used published tidal elevation dependent weathering and erosional data from 1 to 3 year experiments conducted on more than 2000 sandstone argillite and basalt samples from eastern canada the model analysed annual tidal predictions to convert the weathering data into slope recessional units realistic model profiles with notches at the high tidal level were produced within the 3000 6000 year period since the sea attained its present level there were up to 4 cycles of notch formation and collapse during this time in the rapidly eroding sandstones and a smaller number in the argillites notch morphology was affected by the tidal range the rock type and the initial slope gradient but the maximum depth of the notch before collapse controlled only the number and frequency of the collapse events continuous positive and negative changes in rsl extended the notches in the vertical plane according to the rate and direction upwards or downwards of these changes a distinct series of notches can develop from episodic changes in rsl but the survival of older notches and consequently their utility as palaeosea level indicators depends upon such factors as their elevation with respect to the present tidal range

transverse micro erosion meter measurements determining minimum sample size two transverse micro erosion meter tmem stations were installed in each of four rock slabs a slate shale basalt phyllite schist and sandstone one station was sprayed each day with fresh water and the other with a synthetic sea water solution salt water to record changes in surface elevation usually downwearing but with some swelling 100 measurements the pilot survey the maximum for the tmem used in this study were made at each station in february 2010 and then at two monthly intervals until february 2011 the data were normalized using box cox transformations and analyzed to determine the minimum number of measurements needed to obtain station means that fall within a range of confidence limits of the population means and the means of the pilot survey the effect on the confidence limits of reducing an already small number of measurements say 15 or less is much greater than that of reducing a much larger number of measurements say more than 50 by the same amount there was a tendency for the number of measurements for the same confidence limits to increase with the rate of downwearing although it was also dependent on whether the surface was treated with fresh or salt water about 10 measurements often provided fairly reasonable estimates of rates of surface change but with fairly high percentage confidence intervals in slowly eroding rocks however many more measurements were generally needed to derive means within 10 of the population means the results were tabulated and graphed to provide an indication of the approximate number of measurements required for given confidence limits and the confidence limits that might be attained for a given number of measurements

dating fluvial terraces with and profiles application to the wind river wyoming abstract fluvial strath terraces provide a record of river incision and the timing of climatic perturbations to the fluvial system dating depositional surfaces like terraces that are older than the range of 14 c however is difficult we employ a cosmogenic radionuclide crn profile technique that addresses a major problem of crn dating on such surfaces nuclide inheritance by measuring 10 be and 26 al profiles we constrain the exposure age and the mean crn inheritance for the deposit the crn profile also yields a self check on the assumptions underlying the method we report our attempts to date terraces along the wind river wy like many sequences of western north american fluvial terraces these are inferred to reflect oscillation between glacial and interglacial conditions in the headwaters previous dating of some of these terraces and the associated terraces and glacial deposits makes this a unique location to compare dating methods dates from five sites along the bull lake glacial correlative terrace wr 3 are 118 125 ka which agrees with dates on bull lake age moraines and independent age estimates on the terrace and is consistent with the model of terrace glacial relationship crn inheritance is significant and highly variable requiring it be considered despite the additional sampling complexity assuming all inheritance in wr 3 deposits arises during exhumation in the headwaters we obtain minimum mean rates of exhumation of 13 130 m my for the source rocks alternatively assuming the crns are inherited during clast transport the time of fluvial transport from source to terrace is 10 ka it increases downstream and is lower for sand than cobbles the crn ages for older terraces wr 7 300 ka and wr 15 510 ka are lower by 50 than previous estimates based on tephrochronology the most plausible explanation is eolian deflation of a once thicker loess cover on the terrace surfaces mean thicknesses of loess of 0 5 1 5 m are required to reconcile these concentrations of crn with the previous estimates of age difficulty in dating the older terraces emphasizes that geologic caution independent estimates of age and multiple sample sites should still be part of dating depositional surfaces with crns even when employing the inheritance correction technique

patterns of surface downwearing on shore platforms in eastern canada downwearing rates were measured on shore platforms at about 200 transverse micro erosion meter tmem stations over periods ranging from 2 to 6 years there were seven study areas in eastern canada the platforms were surveyed and a schmidt rock test hammer was used to measure rock hardness more than 1200 rock samples from three of the study areas were also subjected each day over a 3 year period to two tidal cycles of immersion and exposure which simulated the central intertidal zone a further 840 samples were subjected to longer periods of exposure and immersion over a 1 year period which represented different elevations within the upper and lower intertidal zone respectively these experiments suggested that tidally generated weathering and debris removal is an effective erosional mechanism particularly at the elevation of the lowest high tides in the field mean rates of downwearing for each study area ranged from 0 24 mm yr 1 to more than 1 5 mm yr 1 rates tended to increase with elevation in the field with maxima in the upper intertidal zone this trend in the field cannot be attributed entirely to the tidally induced weathering processes that were simulated in the laboratory and must reflect in part the effect of waves frost ice and other mechanisms it is concluded that there are no strong spatial downwearing patterns on shore platforms and that downwearing rates in the intertidal zone are the result of a number of erosional mechanisms with different elevation efficacy characteristics furthermore even if only one or two mechanisms were dominant in an area any resulting relationship between downwearing rates and elevation would be obscured or eliminated by the effect of variations in the chemical and physical characteristics of the rocks copyright 2010 john wiley sons ltd