seasonal changes in beach morphology along the sheltered coastline of perth western australia abstract seasonal change in beach morphology is traditionally ascribed to a variation in the incident wave energy level with calm conditions in summer resulting in wide beaches with pronounced subaerial berms and energetic conditions in winter causing narrow beaches with nearshore bar morphology the coastline of perth western australia is characterised by a large seasonal variation in the incident wave height and local beaches exhibit a distinct seasonal change in morphology however these morphological changes are better explained by a seasonal reversal in the littoral drift direction than by variations in the incident wave energy conditions in summer when northward sediment transport prevails due to sea breeze activity beaches located south of coastal structures headlands or rocky outcrops become wider due to the accumulation of sediment against the obstacle these beaches will subsequently erode in winter during storms when the longshore sediment transport is toward the south in contrast beaches located north of obstacles will become narrower during summer and wider during winter the usefulness of the dimensionless fall velocity h b w s t where hb is the breaker height ws is the sediment fall velocity and t is the wave period as a predictor of presence absence of bar morphology and beach type was investigated it was found that fluctuates around the threshold of bar formation 1 5 2 over a variety of time scales daily weekly and seasonally these temporal variations in in conjunction with the relatively low wave energy level that characterises the coast negates the development of beach and nearshore morphology that is in equilibrium with the hydrodynamic conditions as a result bar occurrence and beach type can not be readily predicted using along the perth coast

an integrated approach to coastal erosion problems in northern tuscany italy littoral morphological evolution and cell distribution abstract occupation of the coast has significantly increased in recent decades mostly due to a greater demand for recreation and tourism today erosion threatens many human made structures and activities requiring an integrated approach for the understanding of coastal dynamics and identification of alternatives to associated problems this study investigates a 64 km long coastal physiographic unit in the northern microtidal littoral of tuscany italy vertical aerial photographs and direct field surveys were used to retrieve changes in shoreline position over 1938 1997 and 1997 2005 time intervals significant beach accretion was observed during the first period updrift of carrara 84 m and viareggio 280 m harbours and at marina di pietrasanta 100 m whereas severe erosion occurred downcoast of carrara harbour 130 m at marina dei ronchi and on the northern side of arno river mouth 400 m similar trends were observed between 1997 and 2005 beach slope between the 1997 shoreline position and the closure depth correlated well with the distribution of erosion accretion patterns from the 1938 1997 period slopes were lower in eroded areas than at sites under accretion longshore distribution of erosion accretion patterns was controlled by coastal compartmentalisation three of the main littoral cells were mostly formed by natural limits i e punta bianca promontory marina di pietrasanta the arno river mouth and the port of livorno several sub cells were created within these cells due to the introduction of human made structures such as carrara and viareggio harbours which formed artificial fixed limits that allowed the transport of sediments exclusively fines in one direction only results will help improve the understanding of coastal processes and manage littoral sediment transport in a sustainable manner this will reduce the need for structural interventions such as breakwaters and groynes which in the past decades prevented coastal retreat at local scale but shifted erosion downdrift leading to degradation of the investigated area and requiring continuous maintenance

short and medium term coastal evolution of necochea municipality buenos aires province argentina the short and medium term coastal evolution of necochea municipality buenos aires province argentina was studied the medium term evolution study was based on aerial photographs from 1967 and 1984 and satellite images from 2004 using the dune or cliff toe as coastline indicator the short term evolution was studied from february 2006 to december 2009 by means of seasonal beach profiles and sediment sampling results showed that in the medium term at necochea the coastline has remained stable or has advanced whereas in the short term the analysis has evidenced incipient erosion processes on the other hand at quequen the retreat of the coastline and the negative sedimentary balances medium and short term are clearly indicating an accentuated erosion process the different degrees of coastal erosion are related in part to beach vulnerability to wave storms but mainly to anthropogenic actions which have affected the beach sediment supply these results evidence the necessity to develop a coastal management programme

oxidative mobilization of cerium and uranium and enhanced release of immobile high field strength elements from igneous rocks in the presence of the biogenic siderophore desferrioxamine b abstract polyvalent trace elements such as the high field strength elements hfse are commonly considered rather immobile during low temperature water rock interaction hence they have become diagnostic tools that are widely applied in geochemical studies we present results of batch leaching experiments focused on the mobilization of certain hfse y zr hf th u and rare earth elements from mafic intermediate and felsic igneous rocks in the presence and absence respectively of the siderophore desferrioxamine b dfob our data show that dfob strongly enhances the mobility of these trace elements during low temperature water rock interaction the presence of dfob produces two distinct features in the rare earths and yttrium rey patterns of leaching solutions regardless of the mineralogical and chemical composition or the texture of the rock type studied bulk rock normalized rey patterns of leaching solutions with dfob show i a very distinct positive ce anomaly and ii depletion of la and other light rey relative to the middle rey with a concave downward pattern between la and sm these features are not observed in experiments with hydrochloric acid acetic acid or deionized water in dfob bearing leaching solutions ce and u are decoupled from and selectively enriched relative to light rey and th respectively due to oxidation to ce iv and u vi oxidation of ce3 and u4 is promoted by the significantly higher stability of the ce iv and u vi dfob complexes as compared to the ce iii and u iv dfob complexes this is similar to the relationship between the ce iv and ce iii pentacarbonate complexes that cause positive ce anomalies in alkaline lakes however while formation of ce iv carbonate complexes is confined to alkaline environments ce iv dfob complexes may produce positive ce anomalies even in mildly acidic and near neutral natural waters siderophore promoted dissolution processes also significantly enhance mobility of other immobile hfse and may not only cause or modify ce anomalies and th u fractionation but also mobilization of and fractionation between zr hf th and redox insensitive rey during weathering pedogenesis diagenesis and incongruent dissolution of particles in seawater and freshwater siderophores may significantly affect the use of hfse as geochemical tools concave downward light rey patterns may be used as a biosignature for water rock interaction in the presence of siderophores enhanced and preferential mobilization of u relative to th in the presence of siderophores may produce th u signals comparable to those indicative of weathering under oxidized conditions which might constrain the use of u concentrations and th u ratios as a paleoredox proxy the enhanced mobilization of zr and especially hf from igneous rocks in the presence of dfob might have implications for the use of the latter as a tracer for the impact of continental weathering on seawater chemistry because siderophore complexes affect the particle reactivity of hf and zr they may prevent effective removal of terrigenous hf and zr during aggregation coagulation of riverine particles in estuaries siderophore promoted solubilization and stabilization might hence be an additional way to transport continental hf and zr to the oceans furthermore siderophore enhanced mobilization may also have implications for the remediation techniques employed to immobilize hfse such as u th and rey at nuclear waste and reprocessing sites and at rey ore processing plants where soils are commonly contaminated with these sometimes radioactive heavy metals

temporal and spatial relationship between sediment grain size and beach profile abstract sediment samples and beach profile evolution data collected along one profile line at el puntal spit santander spain are used to analyze the spatial and temporal structure of the grain size distribution variability and its relationship with the beach profile changes standard principal component analysis pca and three way pca is applied to determine the temporal and spatial scales of variability of the data results indicate that the sediment grain size distribution varies markedly along the beach profile both spatially and temporally these variations are shown to be strongly related to morphological changes in the beach profile the spatial eigenvectors determined from the profile data and those from the sediment data exhibit similar patterns with their maxima and minima located at the same position since eigenvectors may be regarded as representative of uncorrelated modes of variability it is concluded that the spatial variability of both sediment and profile data are strongly related in particular it is shown that the location of the highest variability of grain size corresponds to that of the beach profile also different grain sizes are shown to exhibit a distinct degree of variability which leads to the conclusion that each sediment size responds to the same hydrodynamics differently the temporal eigenvectors determined from the profile and the sediment data shown a seasonal dependency however their maxima and minima are not located at the same position it is shown that this temporal shift is due to the different response of each sediment size to the hydrodynamics and in particular that the recovery of the profile starts with fine material from the bar it is inferred that models for beach profile evolution which do not take into account the sorting processes involved in the sediment transport cannot be fully succesful a master grain size sample constructed by adding all the grain samples taken over the profile is used to further examine the cross shore redistribution of the sediment the following working hypothesis is suggested for a beach profile within a physiographic unit the master grain size does not depend on time

low energy sandy beaches in marine and estuarine environments a review this review was undertaken to identify locations where low energy beaches may occur and their diagnostic forms and process controls including waves tides and water levels examples are drawn from the sheltered coastline of western australia near perth and fetch limited estuarine environments on the northeast coast of the united states we suggest that the term low energy be used in locations where 1 non storm significant wave heights are minimal e g 0 25 m 2 significant wave heights during strong onshore winds are low e g 0 50 m 3 beachface widths are narrow e g 20 m in microtidal environments and 4 morphologic features include those inherited from higher energy events micro topographic features can persist in the swash zone of low energy beaches under non storm wave conditions there is little evidence of cyclic cross shore sediment exchange bars excepting transverse forms located seaward of low still water level do not appear to be part of the sediment exchange system with the foreshore developing a better definition of the term low energy requires understanding the occurrence and duration of morphological characteristics and the type magnitude and frequency of hydrodynamic controls that are responsible for these characteristics efforts also should be directed toward 1 discriminating between processes generated within basins in true fetch limited environments and processes generated outside basins that affect sheltered environments 2 identifying the relative contributions of tide and surge related water level fluctuations on low energy beach shape and 3 estimating thresholds for beach change

p wave velocity features of the lithosphere under the eromanga basin eastern australia including a prominent mid crustal conrad discontinuity abstract the crustal structure of the central eromanga basin in the northern part of the australian tasman geosyncline revealed by coincident seismic reflection and refraction shooting contrasts with some neighbouring regions of the continent the depth to the crust mantle boundary moho of 36 41 km is much less than that under the north australian craton to the northwest 50 55 km and the lachlan fold belt to the southeast 43 51 km but is similar to that under the drummond and bowen basins to the east the seismic velocity boundaries within the crust are sharp compared with the transitional nature of the boundaries under the north australian and lachlan provinces in particular there is a sharp velocity increase at mid crustal depths 21 24 km which has not been observed with such clarity elsewhere in australia the conrad discontinuity in the lower crust the many discontinuous sub horizontal reflections are in marked contrast to lack of reflecting horizons in the upper crust further emphasising the differences between the upper and lower crust the crust mantle boundary moho is characterised by an increase in velocity from 7 1 7 7 km s to a value of 8 15 0 04 km s the depth to the moho under the canaway ridge a prominent basement high is shallower by about 5 km than the regional moho depth there is also no mid crustal horizon under the canaway ridge but there is a very sharp velocity increase at the moho depth of 34 km the ridge could be interpreted as a horst structure extending to at least moho depths but it could also have a different intra crustal structure from the surrounding area the sub crustal lithosphere has features which have been interpreted from limited data as being caused by a velocity gradient at 56 57 km depth with a low velocity zone above it because of the contrasting crustal thicknesses and velocity gradients the lithosphere of the central eromanga basin cannot be considered as an extension of the exposed lachlan fold belt or the north australian craton the lack of seismic reflections from the upper crust indicates no coherent accoustic impedance pattern at wavelengths greater than 100 m consistent with an upper crustal basement of tightly folded meta sedimentary and meta volcanic rocks the crustal structure is consistent with a pericratonic or arc back arc basin being cratonised in an episode of convergent tectonics in the early palaeozoic the seismic reflections from the lower crust indicate that it could have developed in a different tectonic environment

mobility and fluxes of major minor and trace metals during basalt weathering and groundwater transport at mt etna volcano sicily abstract the concentrations and fluxes of major minor and trace metals were determined in 53 samples of groundwaters from around mt etna in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma derived co 2 and the contribution of aqueous transport to the overall metal discharge of the volcano we show that gaseous input of magmatic volatile metals into the etnean aquifer is small or negligible being limited by cooling of the rising fluids basalt leaching by weakly acidic co 2 charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the s sw paterno and e zafferana volcano flanks where out flowing groundwaters are the richest in metals and bicarbonate of magmatic origin thermodynamic modeling of the results allows to evaluate the relative mobility and chemical speciation of various elements during their partitioning between solid and liquid phases through the weathering process the facts that rock forming minerals and groundmass dissolve at different rates and secondary minerals are formed are taken into account at mt etna poorly mobile elements al th fe are preferentially retained in the solid residue of weathering while alkalis alkaline earth and oxo anion forming elements as se sb mo are more mobile and released to the aqueous system transition metals display an intermediate behavior and are strongly dependent on either the redox conditions mn cr v or solid surface related processes v zn cu the fluxes of metals discharged by the volcanic aquifer of etna range from 7 0 10 3 t a th to 7 3 10 4 t a na they are comparable in magnitude to the summit crater plume emissions for a series of elements na k ca mg u v li with lithophile affinity but are minor for volatile elements basalt weathering at mt etna also consumes about 2 1 10 5 t a of magma derived carbon dioxide equivalent to ca 7 of contemporaneous crater plume emissions the considerable transport of some metals in etna s aquifer reflects a particularly high chemical erosion rate evaluated at 2 3 10 5 t a enhanced by the initial acidity of magmatic co 2 rich groundwater

the effects of weathering on rare earth element y and ba abundances in tertiary basalts from southeastern australia tholeiitic basalts showing anomalously high ba y and rare earth element ree concentrations occur within the tertiary newer volcanic province of victoria and these geochemical characteristics are related to incipient alteration accompanying weathering ree and y released during weathering of basalts are retained either in secondary phosphate or clay minerals and in rocks showing very high ba concentrations the ba is present as baso4 leaching experiments suggest that glassy or fine grained rocks are more likely to release ree y and ba while more extensively altered rocks are likely to hold these elements probably because they substitute in or are adsorbed on clay minerals or because secondary baso4 and ree phosphates are resistant to acid leaching samples taken sequentially across a weathering profile in a tholeiitic basalt flow from fresh to intensively altered rock illustrate that in the very earliest stages of alteration extreme variations in the abundances of ba y and ree can occur this is reflected in the broad patterns of trace element behaviour manifested by an extensive analysed sample suite from the victorian newer volcanic province where there is no correlation between anomalous enrichments in ba y or ree and the level of incipient alteration ba anomalies are not necessarily accompanied by abnormal y and ree behaviour and this is probably because the mobility of each trace element is a function of a the ionic radius and charge of the ionic species it forms in solution b local groundwater parameters such as eh ph groundwater flux and concentrations in the groundwater of species such as so42 and c the secondary mineral assemblages developed in a particular situation sr isotopic compositions are not strongly affected by incipient weathering and do not show significant changes until alteration has progressed to the point where plagioclase begins to break down the study illustrates that relatively slight alteration at the earliest stages of weathering can produce drastic changes in the concentrations of ree y and ba and petrographic assessment of the freshness of samples is not precise enough to eliminate prior to analysis cases where these effects may be manifested where weathering has caused changes in abundance patterns these may be recognised by careful comparisons of appropriate elemental ratios e g ba rb throughout a particular analysed sample suite

temporal and spatial scales of beach profile change duck north carolina abstract an 11 year time series of high resolution beach profile surveys made on an atlantic ocean beach was analyzed for spatial and temporal characteristics of beach profile change approximately 300 profile surveys most extending from the dune to 8 m depth were available for the analysis on each of four cross shore lines together with electronically recorded and statistically processed wave time series from a nearshore gage located seaward of the survey site the profile survey data set was analyzed for such quantities as depth change frequency of depth change general seasonal shape of the profile seasonal depth change and change in the profile produced by extreme storms the morphodynamics of an inner and outer longshore bar were also examined including depth to bar crest bar height and length and speed of bar movement onshore and offshore several properties of depth change were related to wave characteristics representative results were average profile elevation change from 4 m to 4 m was symmetric about the mean sea level shoreline the average spring and autumn profile shapes were almost identical and occurred as transitional states between the summer and winter profile shapes the depth of active profile movement within survey accuracy of about 0 025 m was 4 m for the summer and 6 m for the winter and the 10 year frequencies of maximum absolute depth change in depths of 2 4 6 and 8 m were 1 64 1 38 0 22 and 0 12 m respectively a surprising result was that typical large storms transported sand into the nearshore from the seaward end of the profile from a depth of about 6 8 m

reaction induced fracturing during replacement processes replacement processes are common transformation mechanisms in minerals and rocks at a variety of conditions and scales the underlying mechanisms are in general poorly understood but both mechanical and chemical processes are thought to be important replacement of leucite kalsi2o6 by analcime naalsi2o6 h2o is common in silica poor igneous rocks a 10 increase in volume is associated with the replacement process and this generates stresses that eventually cause fracturing of the reacting leucite experimentally reacted leucite samples display characteristic fracturing patterns that include both spalling of concentric onion skin like layers near the reacting interface and the formation of cross cutting often hierarchically arranged sets of fractures that divide the remaining leucite into progressively smaller domains these structures may explain the patchy alteration patterns observed in natural leucite samples and similar so called mesh textures associated with the serpentinization of olivine grains during hydration of mafic or ultramafic rocks they are also strikingly similar to larger scale patterns formed during spheroidal weathering processes a simple discrete element model illustrates the mechanics that control the formation of such systems and shows how these replacement processes may be accelerated due to the generation of new reactive surface area by hierarchical fracturing processes

seasonal changes and morphodynamic behavior of a high energy mesotidal beach case study of charf el akab beach on the north atlantic coast of morocco the morphodynamic behavior of a mesotidal sandy beach was monitored during both calm and energetic conditions two years of seasonal surveys were carried out on charf el akab a gently sloped beach in the north atlantic coast of morocco the method of survey consisted of a 3d study of the beach morphological changes and provided 2 cm vertical accuracy during the surveyed period charf el akab beach underwent very energetic wave conditions and the breaking wave height was of h b 1 5 m the beach is characterized by a nonpermanent swash bar and composed of well sorted medium sand the application of environmental parameters revealed a dissipative state with very low beach gradient which did not vary significantly over the studied period morphological changes consist of beach erosion and bar decay under high energy waves whereas the intertidal bar re established and the beach recorded an accentuated accretion due to relatively fair weather conditions the beach volume reveals a seasonal behavior the sand accumulated during summer is dramatically removed during winter season the range in beach sand volume from the most accreted to the most eroded conditions observed is about 5 493 m3 the average sand volume flux between surveys reaches 1 and 0 4 m2 day during peak erosion and accretion periods the relationships between the wave forcing and the sand volume adjustments were examined the sand volume change was found to be highly correlated 0 91 with the wave energy flux the highest correspondence 0 95 was found between the sand flux rate and the wave energy flux the wave forcing is expected to be the main factor governing beach morphodynamics at charf el akab site

a morphodynamic model for beach gradients this paper outlines a general framework for analysis of the problem of beach gradients which divides the system into 1 the independent controls 2 the hydrodynamics 3 the sediment dynamics and 4 the morphodynamics a model is derived from the combination of these stages which shows close agreement with field data for wave steepnesses of less than about 0 06 but predicts lower beach gradients than arc observed for steeper waves the use of analytical feedback in the present model rather than the iterative feedback which is used in computer simulations demonstrates that differential sediment transport may be responsible for stabilizing the beach gradient

from fine sand to boulders examining the relationship between beach face slope and sediment size abstract it is a long standing maxim that coarser sediment sizes are associated with steeper beach face slopes but because most work has focused on sandy beaches few data are available for the pebble cobble or boulder size ranges little is known therefore about how beach morphology and grain size relate at the coarser size grades we compiled data from the literature 2144 measurements of beach face slope with associated grain sizes covering the range from very fine sand to boulders this meta analysis shows that beach faces do tend to steepen as average grain size increases at least up to the cobble size range but the trend is not simple although previous studies suggested a simple power law relationship between grain size and beach face slope in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens and may trend downward for boulders fine and medium sands have the greatest range of reported slopes and the data support the importance of effective weight modification and boundary layer dynamics as primary controls on beach face steepness at these fine size grades around the very coarse sand size grade a plateau marks a shift in beach dynamics as hydraulic conductivity increases beaches switch to being infiltration dominated the trend toward steeper slopes continues but at a lower and steady rate from granules through cobbles there appears to be a falloff in slope for the coarsest boulder deposits but we note that this is based on very few locations so should be considered preliminary the overall data distribution is described by a power law function tan a d 50 0 125 b c the broadness of each transition zone also shows that a range of factors other than grain size governs where that tipping point occurs in the cobble and boulder size ranges there are two deposit categories boulder beaches and supratidal boulder ridges although not commonly thought of as beaches boulder ridges record long term storm deposition and reworking on the highest energy coasts supratidal ridges and boulder beaches seem to show different slope grain size relationships with the steepest slopes occurring in boulder ridges and with boulder beaches showing more gentle gradients than other coarse clastic beaches but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum and invites further work to investigate the sedimentology of cobble and boulder dominated systems

deep crustal reflection results from the central eromanga basin australia abstract from 1980 to 1982 deep seismic reflection profiles were recorded across the central eromanga basin in eastern australia to study the regional structure stratigraphy and geological history of the eromanga basin and infra basins the reflection data were recorded to 20 s to obtain additional information on the nature and structure of the crust below the sediments and their relationship to the development of the basins the seismic sections show good quality reflections from the deep crust as well as from the sedimentary layers based on the character strength coherence continuity and spatial distribution of the reflections the sections can be divided into four zones the tope zone between 0 and 2 5 s shows fairly uniform coherent and continuous events which correlate with the mesozoic and late palaeozoic sediments the zone from 2 5 to 8 s 4 to 22 km does not show any primary reflections and is interpreted as the highly deformed metasedimentary and metavolcanic rocks of the early palaeozoic thomson orogen underlying the sediments without any recognisable reflection or diffraction patterns in this zone it is difficult to say whether the faulting and folding observed in the sediments extend into the upper crustal basement the deeper zone of numerous reflection segments between 8 and 12 5 s 22 to 36 km is interpreted as thin laminae of alternating low and high velocity intermediate and basic rocks and correlates with the lower crust bounded by refraction velocity discontinuities the lowest zone of no reflections below 12 5 s corresponds with the upper mantle the reflection character and thickness as well as the refraction velocity structure of the crust under the central eromanga basin area are significantly different from those of the precambrian crust under the georgina basin to the northwest it is proposed that the crust under the eromanga basin is extensionally attenuated crust which had been intruded by sills of basaltic melt from the underlying asthenosphere

anthropogenic effects on shoreface and shoreline changes input from a multi method analysis agadir bay morocco abstract in many situations the links between shoreline fluctuations and larger scale coastal change embracing the shoreface are not always well understood in particular meso scale years to decades sand exchanges between the shoreface and the shoreline considered as important on many wave dominated coasts are rather poorly understood and difficult to identify coastal systems where sediment transport is perturbed by engineering interventions on the shoreline and shoreface commonly provide fine examples liable to throw light on these links this is especially so where shoreface bathymetric datasets which are generally lacking are collected over time enabling more or less fine resolution of the meso scale coastal sediment budget agadir bay and the city of agadir together form one of the two most important economic development poles on the atlantic coast of morocco using a combined methodological approach based on wave current modelling bathymetric chart differencing determination of shoreline fluctuations and beach topographic surveying we highlight the close links between variations in the bed of the inner shoreface and the bay shoreline involving both cross shore and longshore sand transport pathways sediment budget variations and new sediment cell patterns we show that the significant changes that have affected the bay shoreline and shoreface since 1978 clearly reflect anthropogenic impacts notably blocking of alongshore sand transport by agadir harbour completed in 1988 and the foundations of which lie well beyond the depth of wave closure construction of the harbour has led to the creation of a rapidly accreting beach against an original portion of rocky shoreline updrift and to a net sand loss exceeding 145 000 m 3 year between 1978 and 2012 over 8 5 km 2 of the bay shoreface downdrift shoreline retreat has been further exacerbated by sand extraction from aeolian dunes and by flattening of these dunes to make space for tourist infrastructure digital elevation models of part of the bay beach between 2012 and 2014 confirm this on going sand loss these changes have involved the establishment of two divergent longshore bay sediment cells instead of the original single unidirectional cell a prospective view of these changes suggests that perturbation of longshore drift and the on going bay sediment budget deficit will eventual directly pose threats to the harbour access and to coastal tourism on which the economic growth of agadir has been built

determination of earthquake focal mechanisms and crustal structure in eastern australia using surface waves abstract the surface waves from two medium sized m 5 5 earthquakes in southeast australia 1966 mt hotham and 1982 wonnangatta were examined to determine average s wave crustal structure for the region and the focal mechanisms of the two earthquakes the s wave models were determined from an analysis of the group velocities of the rayleigh waves for all paths a two layer crust overlying a moho at about 40 km is required to fit the observations in the upper layer down to about 25 km the velocity gradients are very small and the s wave velocities are in the range 3 4 3 6 km s in the lower crust the s wave velocities increase gradually to about 4 6 km s at the moho where the velocity gradients are again very small the region where the s wave velocities increase significantly with depth corresponds to the region of the lower crust which generates strong seismic reflections mathur 1983 the thin crust postulated beneath bass strait and tasmania johnson 1973 is not substantiated by these data and a crustal thickness of about 40 km is also required for this region for the longer profiles 1800 km to the north and northwest of the earthquakes the velocity step at the moho is smaller than for the shorter profiles 700 km however because the surface waves are less dispersed for the shorter profiles the resolution is poorer and the models less reliable for the 1982 wonnangatta earthquake the surface wave synthetics from a focal mechanism similar to that obtained by denham et al 1985 fit the observations at five regional stations very well and confirm the nw se compressive stress regime found by other workers however for the 1966 mt hotham earthquake the surface wave synthetics generated from the normal faulting solution which was obtained from an analysis of p wave first motions denham et al 1985 do not agree with the rayleigh wave trains observed at australian stations rather the surface wave observations support a thrust fault type mechanism with the pressure axis having a similar direction to that obtained from the 1982 wonnangatta earthquake and other earthquakes in the region

longshore realignment of shore parallel sand bars at wanganui new zealand abstract the disconnection and realignment of shore parallel nearshore sand bars in the longshore direction is a recently identified morphological behaviour which is referred to as bar switching this phenomenon has been observed in data from multi bar coasts in the netherlands in north carolina on the east coast of the usa and on the west coast of the new zealand north island this paper identifies the characteristics of bar switching along a 6 km stretch of coast at wanganui new zealand analysis of a 6 3 yr record of image based morphological data identified nine periods or episodes of bar switching switching occurred within transition zones which had longshore lengths between 500 and 1000 m episodes occurred throughout the study period at intervals ranging from 0 to 64 weeks mean 25 weeks episode duration ranged from 8 to 27 weeks mean 14 weeks episodes tended to occur sequentially at centres located 2000 3000 and 4400 5200 m from the nearby wanganui river mouth which marks the southeastern boundary of the study area two types of switching episodes were identified shoreward propagating episodes originate in the outer surf zone and the location of switching then moves landward by contrast stationary episodes begin and remain within the mid surf zone episodes of bar switching are characterised by strong longshore currents peak significant wave height values that are usually greater than the 1 exceedence level 3 2 m and significant wave heights above the 5 exceedence level 2 6 m for at least 4 5 of the switching period while high energy conditions are necessary for bar switching to occur such energy levels do not always result in this type of morphological behaviour antecedent morphology and other hydrodynamic factors may also play important roles in the morphodynamics of bar switching

average seismic source parameter relations for mid plate earthquakes mid plate earthquakes which are defined as having their epicenters at least 500 km from plate margins represent a small portion of the total global seismicity however because those occurring within continental interiors are characterized by anomalously large damage areas they are of particular interest empirical mb ms and m o data are used to develop scaling relations for mid plate earthquakes from them it is found that the corner period t o2 of their far field displacement spectra varies as the one fourth power of the seismic moment which indicates that average stress drop increases as seismic moment increases by use of savage s 1972 rectangular bilateral dislocation model the derived spectra of mid plate earthquakes yield estimates of fault rupture length and width average fault displacement and source rise time as a function of seismic moment these relations show that large mid plate earthquakes such as the 1886 south carolina and 1811 and 1812 new madrid events do not require large fault rupture length

storms and shoreline retreat in the southern gulf of st lawrence abstract storms play a major role in shoreline recession on transgressive coasts in the southern gulf of st lawrence gsl southeastern canada long term relative sea level rise off the north shore of prince edward island has averaged 0 3 m century over the past 6000 years 0 2 m century over 2000 years this has driven long term coastal retreat at mean rates 0 5 m a but the variance and details of coastal profile response remain poorly understood despite extensive sandy shores sediment supply is limited and sand is transferred landward into multidecadal to century scale storage in coastal dunes barrier washover deposits and flood tidal delta sinks charlottetown tide gauge records show mean relative sea level rise of 3 2 mm a 0 32 m century since 1911 a further rise of 0 7 0 4 m is projected over the next 100 years when differenced from tidal predictions the water level data provide a 90 year record of storm surge occurrence combined with wind wave hindcast and sea ice data this provides a catalogue of potentially significant coastal storms we also document coastal impacts from three recent storms of great severity in january and october 2000 and november 2001 digital photogrammetry 1935 1990 and shore zone surveys 1989 2001 show large spatial and temporal variance in coastal recession rates weakly correlated with the storm record in part because of wave suppression or coastal protection by sea ice large storms cause rapid erosion from which recovery depends in part on local sand supply but barrier volume may be conserved by washover deposition barrier shores with dunes show high longshore and interdecadal variance with extensive multidecadal healing of former inlet and overwash gaps this reflects recovery from an episode of widespread overwash prior to 1935 possibly initiated by intense storms or groups of storms in the latter half of the 19th century with evidence from the storms of 2000 2001 this points to the importance of storm clustering on scales of weeks to years in determining erosion vulnerability as well as the need for a long term large scale perspective in assessing coastal stability the expected acceleration in relative sea level rise together with projections of increasing storm intensity and greatly diminished winter ice cover in the southern gsl implies a significant increase in coastal erosion hazards in future

700 yr sedimentary record of intense hurricane landfalls in southern new england five intense category 3 or greater hurricanes occurring in 1635 1638 1815 1869 and 1938 have made landfall on the new england coast since european settlement historical records indicate that four of these hurricanes 1635 1638 1815 and 1938 and hurricane carol a strong category 2 storm in 1954 produced significant storm surges 3 m in southern rhode island storm surges of this magnitude can overtop barrier islands removing sediments from the beach and nearshore environment and depositing overwash fans across back barrier marshes lakes and lagoons in a regime of rising sea level accumulation of marsh lake or lagoon sediments on top of overwash deposits will preserve a record of overwash deposition we examined the record of overwash deposition at succotash salt marsh in east matunuck rhode island and tested the correlation with historical records of intense storms aerial photographs taken after hurricanes in 1954 and 1938 show overwash fans deposited at the site analysis of 14 sediment cores from the back barrier marsh confirmed the presence of these fans and revealed that 4 additional large scale overwash fans were deposited within the marsh sediments the four overwash fans deposited since the early seventeenth century at succotash marsh matches the historical record of significant hurricane induced storm surge these fans were most likely deposited by hurricanes in 1954 1938 1815 and either 1638 or 1635 radiocarbon dating of two prehistoric overwash fans indicated that these were deposited between a d 1295 1407 and 1404 1446 and probably represent intense hurricane strikes in the past 700 yr at least 7 intense hurricanes struck the southern rhode island coast and produced a storm surge that overtopped the barrier at succotash marsh

spatial and seasonal aspects of beach stability recent work at three contrasting sites in england and wales has shown characteristics atypical of those frequently reported elsewhere these differences are a taking each entire beach system there is no uniform trend of erosion or accretion nor a progressive variation in beach elevation or volume alongshore from one survey to the next however for swansea bay the long term i e 18 months range in profile height along that stretch of coast where the alignment of the beach is normal to the direction of wave approach correlates well with computed wave energy derived from relevant offshore wave directions b while beach variability is greatest during the winter i e storm period there is no overall tendency for a drawdown of sediment from the intertidal zone at that time response times are relatively short thus high beach levels need not necessarily be associated with summer conditions c although in swansea bay there is a tendency for the beach height to fluctuate least at mid tide level this is not true of the other two sites in no area does sediment eroded from the upper exposed part of the beach regularly appear to be deposited on the lower exposed part or vice versa

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

a heat production model of the crust and upper mantle abstract experimental evidence on the relationship between seismic velocity and radiogenic heat production has been used to estimate the vertical distribution of heat sources in the continental lithosphere the derived differentiation rate of the radioelements with depth has been investigated to depths 100 km in various world wide tectonic provinces the results show that more pronounced upward differentiation steeper heat production distribution corresponds to regions of higher heat flow and usually higher crustal temperatures thus crustal distributions of radiogenic heat may be related to tectonic age and crustal evolution the vertical distribution of heat production can be traced even in the subcrustal lithosphere and confirms the upward concentration of a substantial part of the radioelements into the crust at the expense of the upper mantle reflecting the early stages of crustal separation while in the uppermost crust the distribution of the heat sources seems to be controlled by uranium and thorium in the upper mantle it is potassium which controls it data obtained may be important in the geothermal modelling deep temperature calculation and in determinations of moho heat flow

the weathering of basalt and relative mobilities of the major elements at belbex france abstract a basalt and its weathered profile have been analysed for major elements graphical examination shows al fe and ti to have been essentially immobile determining mobility sequences for this deposit is complicated by the long pedogenetic history of the area three different sequences are presented two for different stages of weathering integrated over time and one that reflects the weathering regime of the present day

geochemical anatomy of a spheroidally weathered diabase major trace element concentrations and nd sr isotope ratios were measured in micro drilled samples of a 237 ga old hand specimen sized spheroidally weathered diabase from southern india a sample of the un weathered diabase dike was also analyzed x ray micro ct imaging of the weathered sample shows three dominant mineral phases which are plagioclase pyroxene and a fe bearing phase possibly hematite and or ilmenite this imaging documents the pervasive nature of two generations of ribbon like cross cutting fractures the older fracture is sealed while the more recent fracture is open without any in filling the values of the chemical index of alteration cia of the samples show a wide range but are less than 50 despite being a relatively less weathered rock we observe that concentrations of major minor and trace elements vary significantly with the percentage relative standard deviation rsd for the elements ranging from 10 2 41 8 the cia of the samples do not show any trend with the position of the sample in the hand specimen barring ca and li whose concentrations decrease from the core to the rim of the sample there is no significant spatial trend in the concentrations of the elements concentrations of na al and sr increase with increasing cia values while concentrations of mg fe and sc decrease with increasing cia the strong positive correlations of na and al as well as na and sr indicates preferential weathering of plagioclase in the diabase na ca increases while mg al mg na mg ca fe al and sc sr decrease with increasing cia values and the un weathered rock plots in the middle of these trends such variations are explained in terms of differential weathering of plagioclase in samples with lower cia than the un weathered rock w1 type and pyroxene in samples with higher cia than the un weathered rock w2 type which have varying resistance to weathering at the hand specimen scale the variability in the weathering indices like cia are controlled by differential weathering of minerals and might not accurately reflect the intensity of weathering chondrite normalized la sm and gd lu co vary with cia values indicating mobility of the rees during spheroidal weathering even at the hand specimen scale the eu anomaly also increases with increasing cia values which is explained by differential weathering of pyroxene and plagioclase we observe large percentage deviations of the nb normalized concentrations of elements from the un weathered rock in specific samples but no spatial trend is observed overall the variations in element concentrations can be explained by varying fluid mobility of the elements selective weathering of the minerals in the diabase and ambient environmental conditions considerable nd and sr isotopic variability is observed at the hand specimen scale and is explained in terms of weathering related fractionation of parent daughter ratios this elemental fractionation must have happened long time ago to allow for radiogenic decay of the long lived isotopes of rb 87 and sm 147 the spread rsd in the initial sr and nd isotope compositions of the weathered samples reach a minimum value around 12 13 ga which we interpret as the timing of the peak weathering event which led to fractionation of the parent daughter ratios for nd isotopes the average epsilon nd 1 2 ga of the weathered samples coincides with the epsilon nd 1 2 ga of the unweathered rock the timing of the weathering event coincides with the timing of the breakup of the columbia supercontinent and follows wide spread alkaline volcanism in the indian subcontinent this is the first such attempt to determine the timing of a weathering event in rocks using long lived radioactive isotopes c 2016 elsevier b v all rights reserved

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

medium term coastal response at the ebro delta spain abstract measurements of shoreline displacements along the ebro delta coast have been used to estimate the medium term evolution of the coastline aerial photographs and beach profile surveys covering the last 35 years have been used shoreline data obtained from beach surveys have been analysed using a linear regression technique in order to filter out short term components the medium term scale has been derived from the asymptotic trend with this filtered analysis results have been compared with trends observed in the past and a similar qualitative behaviour has been found rates of change have decreased because the shoreline has slowly evolved towards a more stable configuration a profile closure depth of 7 m has been estimated based on morphological changes in the submerged profiles and then used to convert shoreline displacements into yolume changes from these a medium term sediment budget has been calculated based on the available evidence it has been assumed that these changes are mainly due to wave induced longshore transport gradients assuming proper boundary conditions the net longshore transport scheme has been estimated for each hemidelta the results obtained using this method are in good agreement with the longshore transport rates predicted by well known transport formulae

statistical empirical index of chemical weathering in igneous rocks a new tool for evaluating the degree of weathering abstract chemical weathering indices are useful tools in characterizing weathering profiles and determining the extent of weathering however the predictive performance of the conventional indices is critically dependent on the composition of the unweathered parent rock to overcome this limitation the present paper introduces an alternative statistical empirical index of chemical weathering that is extracted by the principal component analysis pca of a large dataset derived from unweathered igneous rocks and their weathering profiles the pca analysis yields two principal components pc1 and pc2 which capture 39 23 and 35 17 of total variability respectively the extent of weathering is reflected by variation along pc1 primarily due to the loss of na 2 o and cao during weathering in contrast pc2 is the direction along which the projections of unweathered felsic intermediate and mafic igneous rocks appear to be best discriminated therefore pc1 and pc2 represent independent latent variables that correspond to the extent of weathering and the chemistry of the unweathered parent rock subsequently pc1 and pc2 were then mapped onto a ternary diagram mfw diagram the m and f vertices characterize mafic and felsic rock source respectively while the w vertex identifies the degree of weathering of these sources independent of the chemistry of the unweathered parent rock the w index has a number of significant properties that are not found in conventional weathering indices first the w index is sensitive to chemical changes that occur during weathering because it is based on eight major oxides whereas most conventional indices are defined by between two and four oxides second the w index provides robust results even for highly weathered sesquioxide rich samples third the w index is applicable to a wide range of felsic intermediate and mafic igneous rock types finally the mfw diagram is expected to facilitate provenance analysis of sedimentary rocks by identifying their weathering trends and thereby enabling a backward estimate of the composition of the unweathered source rock

morphological characteristics and medium term evolution of the beaches between ceuta and cabo negro morocco this work presents the results of a combined study on the beach morphology and the evolution at short and medium term of the littoral between ceuta and cabo negro morocco it is an interesting sector showing a great increase of human occupation and coastal structures the monitoring program allowed for the reconstruction of the beach morphological behavior and the seasonal changes the studied beaches presented reflective profiles recording little seasonality with the most notable morphological changes being strictly related to storms surf similarity and surf scaling parameters highlighted the existence of intermediate and reflective beach states characterized by plunging breakers aerial photographs and a satellite image have been geo referenced and elaborated with gis tools to reconstruct the short and medium term evolution of the littoral and the sediment transport pathways the littoral showed important erosion at short and medium term related to a negative sedimentary budget because of offshore transport sand accumulation was recorded close to the main ports i e marina smir and marina kabila these port structures constituted impermeable fixed limits which divided the studied area into littoral cells other free transit limits were also observed

port redesign and planned beach renourishment in a high wave energy sandy muddy coastal environment port gisborne new zealand redesign of port gisborne for the 21st century has encompassed a broad interdisciplinary approach this procedure has taken into account the operational requirements of the port effects of dredging and construction upon the benthic fauna and wave activity within the port confines after the proposed development added amenity value of the development to the local community is an important ancillary redesign consideration initially a major research project into the environmental impacts of the developments has been undertaken the project which commenced in 1996 and is still continuing involves an iterative approach integrating the initial design and development options with the operational feasibility construction constraints environmental constraints social acceptability and economic practicality of the port all of these require in depth assessment to obtain the necessary planning and development approvals this requires close liaison between the professional environmental research scientists port management port operation staff pilots construction engineers planners and the community interest groups numerical modelling of the hydrodynamics of poverty bay simulating waves and current effects on the various initial designs options and calibrated against data from a substantial field program has been a fundamental tool it was applied experimentally to determine the best option for the port layout as well as to assess sedimentation impacts modelling results indicated a significant increase in maintenance dredging expected as a result of deepening the navigation approach channel because this may have an impact on the nearby sandy beach by inducing erosion the best option for disposal of the sandy dredged material was determined to be disposal in the surf zone for subtidal beach profile renourishment textural analysis of the sediments trapped in the navigation channel demonstrated that they were suitable for this purpose d 2002 elsevier science b v all rights reserved

behaviour of beach profiles during accretion and erosion dominated periods beach profiles have been surveyed at monthly intervals between 1972 and 1988 at moruya on the south coast of new south wales australia four profile sites have been used as a data set to provide an understanding of changes to beach volume width and shape moruya beach represents a moderately high energy microtidal environment which responds in a dramatic way to major storm events such as those experienced in the mid 1970s this study distinguishes between profile characteristics associated with such a period erosion dominated or edp compared with periods when accretion dominated adp accompanied by foredune expansion in both height and width