rapid erosion of a small southern california beach fill abstract a winter storm eroded a small 160 000 m3 beach fill at torrey pines state beach in southern california the fill constructed in april 2001 was a 600 m long flat topped berm extending from a highway revetment seaward about 80 m terminating in a 2 m tall near vertical scarp the size distributions of the preexisting and fill beach sand were similar median 0 2 mm a total of 56 cross shore transects were surveyed between the revetment and 8 m water depth biweekly along 2 7 km of the beach centered on the fill area during summer and fall the incident significant wave heights measured 1 km offshore of the fill usually were below 1 m the scarp was not overtopped and the fill did not change greatly the beach face alongshore of the fill accreted consistent with the usual seasonal cycle in southern california during a storm 3 m significant wave height in late november erosion began when wave uprushes overtopped the scarp and reached the relatively flat elevated fill where the overwash flowed alongshore to initially small depressions that channeled the flow seawards the offshore flow rapidly deepened and widened the channels which maintained steep vertical faces and eroded by slumping thirty hours after the storm began the shoreward end of the eroded channels had retreated to the highway revetment leaving uneroded sand peninsulas protruding seawards 50 m from the revetment and elevated 1 75 m above the surrounding beach erosion of the beach adjacent to the fill was much less variable alongshore than within the fill region during the next few days the peninsulas eroded almost completely

the formation and evolution of the barrier islands of inhaca and bazaruto mozambique abstract the barrier islands of inhaca and bazaruto are related to the extensive coastal dune system of the mozambican coastal plain south east africa optically stimulated luminescence osl dating of key stratigraphic units indicates that accretion of sediment within these systems is episodic both islands appear to have been initiated as spits extending from structural offsets in the coastline superposition of significant quantities of sediment upon these spits during subsequent sea level highstands formed the core of the islands which were anchored and protected by beachrock and aeolianite formation at least two distinct dune building phases occurred during marine oxygen isotope stage mis 5 tentatively attributed to marine transgressions during sub stages 5e and 5c although some localized reactivation of dune surfaces occurred prior to the holocene large quantities of sediment were not deposited on either island during the low sea levels associated with mis 2 significant dune building and sediment reworking occurred immediately prior to and during the holocene though it is not clear whether these processes were continuous or episodic significant erosion of the eastern shoreline of bazaruto suggests that it is far less stable than inhaca and may suffer further large scale erosion a model is presented for the formation of barrier islands along the mozambican coastal plain

storm induced response of a nearshore bar system abstract a nearshore bar system was surveyed periodically through a storm and the following recovery period the data showed a very rapid response of morphology to changing wave conditions and allowed various models on bar formation to be tested under low energy conditions prior to the storm a small bar was surveyed 13 m offshore both the high reflectivity of the beach and the cross shore distance to the bar are consistent with a model of sediment convergence at the node or antinode of a standing wave of incident period such a small scale bar may be a common feature on beaches with steep foreshores and more gentle offshore slopes with the increase in wave height during the storm the bar became better developed and migrated offshore at rates up to 2 2 m h 1 the bar maintained its form in that the ratio of trough depth to crest depth h t h c remained roughly constant the bar was in no way related to processes which would cause the convergence of sediment in the breaker zone through most of the storm the bar crest distance offshore was typically only 10 of the surf zone width analysis of the bar distance offshore in terms of a standing wave motion showed that the causative wave period must have been much longer than that of incident waves probably on the order of a minute surf zone wave data showed significant energy in the infragravity band at these periods although no definite link has been made after the height of the storm the bar had a crescentic morphology the development of this morphology occurred very rapidly with parts of the bar migrating onshore at rates up to 1 2 m h 1 in contrast to the storm during the recovery period h t h c varied by nearly a factor of three analysis of the offshore and longshore length scales showed the bar to be similar to one which would be generated by a standing mode 1 edge wave of period on the order of one minute

laboratory investigation of dune erosion using stereo video abstract simple parameterizations of dune erosion are necessary for forecasting erosion potential prior to an oncoming storm dune erosion may be parameterized in terms of the elevation of the total water level composed of surge tide and wave runup above the dune base and period of exposure of the dune to waves in this work we test several versions of this model using observations from a large wave tank experiment designed to model a storm hydrograph and we develop a new method for acquiring the appropriate data with confidence intervals using stereo video techniques the stereo method results in observations of dune morphology at higher spatial and temporal resolutions than traditional survey methods allow resolution of the stereo technique was 0 1 m in the horizontal and 0 04 m in the vertical and errors in stereo observations were on the order of 0 02 to 0 08 m 1 to 2 pixels when compared with surveys a new method was developed to estimate confidence intervals on stereo observations when the unchanging dune top was repeatedly sampled the new confidence intervals encompassed 2 standard deviations of scatter about the mean dune surface 98 of the time observations from the stereo method were used to quantify wave runup and dune erosion we tested a variety of runup statistics based on a gaussian distribution of swash properties and found that the most predictive statistic for dune erosion was the 16 exceedance elevation above the dune base lower than the often used 2 exceedance value we found that the parameterization of runup was sensitive to the definition of beach slope and that the most accurate beach slope for predicting runup was through the region of the beach profile defined by the mean water level plus one standard deviation of swash the dune base retreated along a relatively constant trajectory that was a half of the initial beach slope finally a simple model for dune erosion was tested and found to reproduce 64 of the observed variance in dune erosion rate given known forcing at the dune and 49 of the observed variance in dune erosion rate given parameterized forcing integrating the simple model over time 93 of the observed dune retreat distance was reproduced given offshore forcing

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

the last glacial maximum in central and southern north island new zealand a paleoenvironmental reconstruction using the kawakawa tephra formation as a chronostratigraphic marker abstract kawakawa tephra formation comprising oruanui ignimbrite flow member and aokautere ash airfall member represents the products of an exceptionally large and widespread volcanic eruption from taupo volcanic centre in the north island of new zealand the eruption occurred during the last glacial maximum and is radiocarbon dated at c 22 6 ka b p thermoluminescence ages are in broad agreement with the radiocarbon age the presence of aokautere ash in loess deposits in alluvial gully fills on river terraces and its absence from unstable sites permits a detailed assessment of geomorphic activity during the last glacial maximum widespread erosion of regolith aggradation of river valleys and deposition of loess particularly in the period following eruption of the kawakawa point to a cold dry variable climate a collation of pollen data for sediments containing aokautere ash and those 14c dated in the range 17 23 ka shows that tall forest was highly restricted in the central and southern parts of the north island an apparently subalpine grassland shrubland was present at sites from present sea level to over 800 m elevation suggesting that factors other than lower temperatures such as exposure to wind and frost fire and reduced rainfall were important in controlling vegetation patterns we conclude that the interval 23 13 ka b p broadly equivalent to oxygen isotope stage 2 represents the period of greatest environmental change in the north island

beach and dune erosion during storm surges this paper presents the set up and results of an extensive research programme concerning the erosion of coastal dunes during storm surges a large number of two dimensional and three dimensional mobile bed model tests has been carried out to investigate the process of dune erosion the state of art after a series of small scale tests is summarized attention is focussed on large scale tests carried out in the delta flume with random waves up to 2 m significant height sediment concentration and orbital velocity measurements are discussed the large scale tests have confirmed the validity of a modelling technique based on the dimensionless fall velocity parameter h tw the model results are being applied to check the safety of existing coastal dunes as a water retaining structure that has to protect the major part of the netherlands from inundation during storm surges

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

sediment transport on dissipative intermediate and reflective beaches abstract in this paper we review and synthesize field measurements of suspended sediment transport on the shoreface of dissipative intermediate and reflective beach states the morphodynamic beach state continuum was originally established in the 1970s but at the time only hydrodynamic processes and morphologies in these various states were described since the early 1980s when sensors capable of resolving suspended sediment concentration at intra wave time scale became available many studies have examined suspended sediment transport by waves and currents on the shoreface the synthesis of this work shows that the two end states in the morphodynamic continuum which are the dissipative and reflective states exhibit relatively small rates of cross shore sediment transport and weak gradients in that transport which both ensure that the nearshore morphology is relatively stable the intervening intermediate beach states typically exhibit prominent bar topographies and in these states strong morphodynamic feedbacks between hydrodynamic processes and morphology create locally large transport rates and sharp transport gradients which is the reason for the dynamic nature of these beach states transport processes driving sediment onshore and offshore within beach states are discussed as well as the transport processes responsible for state transitions

experimental simulation of shoreface nourishments under storm events a morphological hydrodynamic and sediment grain size analysis this study focuses on barred beach shoreface nourishments physically simulated in a wave flume the attack of a schematic storm on three different nourishments is analysed the apex and waning storm phases lead respectively to offshore and onshore sediment transports nourishments in the trough and on the outer bar feed the bar and increase wave dissipation offshore the bar acts as a wave filter and reduces shore erosion lee effect in contrast nourishment on the beach face leads mostly to shore feeding and reconstruction feeder effect with successive nourishments the beach face clearly becomes steeper and onshore sediment transport is reduced during moderate wave climates the surface grain size analysis reveals marked variations coarser sediments are sorted on the bar and the upper beach face these locations correspond to large wave dissipation zones during the storm apex

complex evolution of transient slip derived from precise tremor locations in western shikoku japan transient slip events which occur more slowly than traditional earthquakes are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle surface based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip either in time or in space accompanying some of these slip transients is a relatively weak extended duration seismic signal known as nonvolcanic tremor which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event by precisely locating the tremor we can track some features of slip evolution with unprecedented resolution here we analyze two weeklong episodes of tremor and slow slip in western shikoku japan we find that these slip transients do not evolve in a smooth and steady fashion but contain numerous subevents of smaller size and shorter duration in addition to along strike migration rates of 10 km d observed previously much faster migration also occurs usually in the slab dip direction at rates of 25 150 km h over distances of up to 20 km we observe such migration episodes in both the updip and downdip directions these episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts the surrounding regions of the fault may slip more continuously driving these stronger patches to repeated failures tremor activity has a strong tidal periodicity possibly reflecting the modulation of slow slip velocity by tidal stresses

origin of eolian sand mobilization during the past 2300 years in the mu us desert china abstract eolian sand dunes and sand sheets are extensive in the semiarid regions of northern central china previous studies indicated that these eolian sands mainly formed during historical times however the sand sources and their reworking processes have not been well studied and even the reasons for their occurrence are still controversial field investigation and sedimentary evidence indicate that both the inner mu us desert and its southern marginal region both sources of modern eolian sand are largely associated with reworking of sands of the last glaciation based on geological documentary and archaeological data three phases of land cultivation during the past 2300 years together with historical droughts high wind energy and the easily reworked sand sources largely account for the occurrence of active sand dunes and sand sheets in the mu us desert

last glacial coastal dunes in eastern australia and implications for landscape stability during the last glacial maximum abstract the last glacial maximum or lgm 25 000 15 000 yr b p has been recognized in australia as a period of increased dryness coolness continentality and windiness compared to earlier and later period enhanced aeolian activity during the lgm occurred in arid and semi arid regions of western central and eastern australia the east coast has been considered to have been better watered and vegetated however at a number of sites from tasmania to north queensland there is evidence for extensive aeolian instability of coastal sand deposits dating by radiocarbon and thermoluminiscence techniques has supported morphologic and stratigraphic evidence of dune formation during the lgm under the influence of westerly offshore winds in the southern sector of the east coast i e south of 31 s latitude and southeast winds to the north it is now apparent that vegetation cover on sandy surfaces was quite patchy during the lgm sand surface instability under conditions of strong west or southeast winds promoted linear and or parabolic dune development this suggests greater concentration of forests in more discrete protected sites along the eastern escarpment than was previously considered by palaeoecologists more widespread drier and cooler climatic conditions operated even in coastal regions on expanded continental shelves at this time stabilization of areas of active dunes became more likely as sea levels rose reduced windiness occurred and precipitation increased as sea surface temperatures began to rise in the holocene

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

observations of sand bar evolution on a natural beach waves currents and the location of the seafloor were measured on a barred beach for about 2 months at nine locations along a cross shore transect extending 255 m from 1 to 4 m water depth the seafloor location was measured nearly continuously even in the surf zone during storms with sonar altimeters mounted on fixed frames the crest of a sand bar initially located about 60 m from the shoreline moved 130 m offshore primarily when the offshore significant wave height exceeded about 2 m with 1 5 m of erosion near the initial location and 1 m of accretion at the final location an energetics type sediment transport model driven by locally measured near bottom currents predicts the observed offshore bar migration but not the slow onshore migration observed during low energy wave conditions the predicted offshore bar migration is driven primarily by cross shore gradients in predicted suspended sediment transport associated with quasi steady near bottom offshore flows these strong 50 cm s currents intensified near the bar crest by wave breaking are predicted to cause erosion on the shoreward slope of the bar and deposition on the seaward side the feedback amoung morphology waves circulation and sediment transport thus forces offshore bar migration during storms

late quaternary lunette dune sedimentation in the southwestern kalahari desert south africa luminescence based chronologies of aeolian activity abstract through the application of luminescence dating techniques great advances have recently been made in the understanding of the late quaternary histories of many dryland regions including southern africa here this work has largely applied optical dating to sediments from the extensive linear dune systems which dominate the kalahari region of the central southern african interior relatively little attention has been given to localised aeolian accumulations such as lunette dunes despite their wide distribution over many parts of the region in particular the arid southwest kalahari to redress this we consider the palaeoenvironmental significance of pan margin lunettes and investigate the timing of lunette dune development in the southwest kalahari through the application of optical dating to sediments from lunette dunes associated with four closed basins pans ages show that localised aeolian activity occurred frequently throughout the past 18 ka indicating that the factors controlling lunette sedimentation are markedly different from those determining regional linear dune development it is proposed that the mechanisms controlling sediment supply to lunette dunes are controlled at both the regional and local pan specific scales by factors such as groundwater levels where pans support more than one discrete lunette the time since any individual lunette crest received significant accumulations of sediment increases with distance away from the pan margin outer and inner lunette sequences may be chronologically disparate features inner lunette formation may arise in response to modifications to the local atmospheric boundary conditions by the presence of large downwind outer lunette features or by shifts in sediment supply

ubiquity of anomalous fading in k feldspars and the measurement and correction for it in optical dating anomalous fading rates were measured in k feldspars separated from 49 sediment samples mainly from north america the intensity of the optically stimulated luminescence was found to decrease linea

upper quaternary marine terrace chronology and deformation south taranaki new zealand an extensive flight of late quaternary marine terraces in the south taranaki region of the north island of new zealand is dated using fission track radiocarbon and amino acid racemization methods a simple model of terrace deformation based on a doming type uplift pattern allows terrace strandline ages to be estimated twelve strandlines are recognized and are estimated to have formed during high sea level stands at 60 000 80 000 100 000 120 000 135 000 210 000 310 000 340 000 400 000 450 000 520 000 600 000 and 680 000 yr b p

laboratory investigation of the bruun rule and beach response to sea level rise abstract rising sea levels are expected to cause widespread coastal recession over the course of the next century in this work new insight into the response of sandy beaches to sea level rise is obtained through a series of comprehensive experiments using monochromatic and random waves in medium scale laboratory wave flumes beach profile development from initially planar profiles and a 2 3 power law profile exposed to wave conditions that formed barred or bermed profiles and subsequent profile evolution following rises in water level and the same wave conditions are presented experiments assess profile response to a step change in water level as well as the influence of sediment deposition above the still water level e g overwash a continuity based profile translation model ptm is applied to both idealised and measured shoreface profiles and is used to predict overwash and deposition volumes above the shoreline quantitative agreement with the bruun rule and variants of it is found for measured shoreline recession for both barred and bermed beach profiles there is some variability between the profiles at equilibrium at the two different water levels under these idealised conditions deviations between the original bruun rule the modification by rosati et al 2013 and the ptm model predictions are of the order of 15 and all these model predictions are within 30 of the observed shoreline recession measurements of the recession of individual contour responses such as the shoreline may be subject to local profile variability therefore a measure of the mean recession of the profile is also obtained by averaging the recession of discrete contours throughout the active profile the mean recession only requires conservation of volume not conservation of profile shape to be consistent with the bruun rule concept and is found to be in better agreement with all three model predictions than the recession measured at the shoreline

palaeocirculation across new zealand during the last glacial maximum at 21 ka abstract what circulation pattern drove southern alps glacial advances at 21 ka late 20th century glacial advances in new zealand are commonly attributed to a dual precipitation increase and cooler than normal temperatures associated with enhanced westerly flow that occur under synoptic pressure patterns termed zonal regimes kidson 2000 but was the circulation pattern that supported major southern alps glacial advances during the global lgm similar to the modern analog here a regional climate regime classification rcrc time slice was used to infer past circulation for new zealand during the lgm at 21 ka palaeoclimate information that supported the construction of the 21 ka time slice was derived from the nz intimate climate event stratigraphy ces one new auckland maar proxy record and additional low resolution data sourced from the literature the terrestrial evidence at 21 ka implicates several possibilities for past circulation depending on how interpretations for some proxies are made the interpretation considered most tenable for the lgm based on the agreement between terrestrial evidence marine reconstructions and palaeoclimate model results is an anticyclonic zonal circulation regime characterized by increased influences from blocking highs over the south island during winter and an increase in zonal and trough synoptic types with southerly to westerly quarter wind flow during summer these seasonal circulation traits would have generated lower mean annual temperatures cooler than normal summer temperatures and overall lower mean annual precipitation for new zealand particularly in the western south island at 21 ka the anticyclonic zonal time slice reconstruction presented in this study has different spatial traits than the late 20th century and the early little ice age signatures suggesting more than one type of regional circulation pattern can drive southern alps glacial activity this finding lends support to the hypothesis that temperature over precipitation change is more important as the primary modulator of southern alps ice advances the rcrc approach also demonstrates some subtle advantages of integrating multi proxy data within a palaeocirculation context for new zealand notably because this reconstruction technique enables direct comparisons to coarsely resolved palaeoclimate model outputs that do not have downscaled information

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

morphological hysteresis in the evolution of beach profiles under sequences of wave climates part 1 observations abstract novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates the experiments were conducted in a wave flume at medium scale using both monochromatic and random waves representing 2d conditions beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler from which shoreline location bar position and sediment transport rates were derived experiments were conducted for sequences of wave climates where a sequence comprised of 6 13 sequential tests each commencing with the beach profile from the preceding test each test was run until equilibrium conditions were obtained and had a constant wave height increased or decreased relative to the preceding test cyclical conditions were also included with erosive and accretive wave conditions of short durations alternating through multiple cycles so that equilibrium conditions were not reached during a test with a sequence of increasing wave heights the relationship between the shoreline position and the bulk cross shore sediment transport at equilibrium was non monotonic indicating a maximum in the landward sediment transport rate for test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights morphological hysteresis was observed in the equilibrium shoreline position and bulk cross shore sediment transport such that shoreline recession or offshore transport continued in some instances after reductions in wave height this is inconsistent with classical equilibrium type shoreline evolution models however when equilibrium conditions were not reached in the cyclic sequences no such morphological hysteresis was observed and a dynamic equilibrium is reached the morphological hysteresis occurs because of the decay stranding or increased relative depth of the breaker bar following a reduction in wave height often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone similar sequences of morphological response are evident in field data and larger scale tests in the literature finally it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of wright et al 1985 by introducing the concept of a subsequent alternate active beach state which may occur following a change in wave conditions

detecting low frequency earthquakes within non volcanic tremor in southern taiwan triggered by the 2005 mw8 6 nias earthquake 1 we use a matched filter technique to detect 41 low frequency earthquakes lfes within 700 s of triggered tremor signals in the southern central range in taiwan during the surface waves of the 2005 mw8 6 nias earthquake off the coast of northern sumatra the depth distributions of lfes after double difference relocations concentrate at the depth range of 12 38 km below the background seismicity and above the moho depth inferred from receiver function studies the locations of lfes are close to the downward extension of the steep dipping chaochou lishan fault with only modestly high vp vs ratios 1 75 1 85 our observation indicates that at least portions of triggered tremor consists of many lfes similar to ambient tremor observed at other major plate boundary faults

southern north sea storm surge event of 5 december 2013 water levels waves and coastal impacts the storm surge event that affected the coastal margins of the southern north sea on 5 6 december 2013 produced the highest still water levels on record at several tide gauges on the uk east coast on east facing coasts south of the humber estuary and north facing norfolk water levels were higher than in the twentieth century benchmark surge event of 31 january 1 february 1953 maximum significant wave heights were highest off the north norfolk coast peak hs 3 8 m offshore 2 9 m inshore and lowest off the suffolk coast hs 1 5 1 8 m inshore comparable offshore wave heights in 1953 were 7 8 m and ca 3 m the lower wave heights and their short duration in 2013 explain both localised breaching overtopping and back barrier flooding associated with gravel ridges and relatively low earthen banks as well as the lack of failure in more highly engineered coastal defences on barrier coasts and within estuaries the signal of maximum runup was highly variable reflecting the modification of the tide surge wave signal by inshore bathymetry and the presence of a range of coastal ecosystems the landscape impacts of the december 2013 surge included the notching of soft rock cliffs and cliffline retreat erosion of coastal dunes and the augmentation or re activation of barrier island washover deposits whilst surge event related cliff retreat on the rapidly eroding cliffs of the suffolk coast lay within the natural variability in inter annual rates of retreat the impact of the surge on upper beach sand dune margins produced a pulse of shoreline translation landwards equivalent to about 10 years of normal shoreline retreat the study of east coast surges over the last 60 years and the identification of significant phases of landscape change such as periods of rapid soft rock cliff retreat and the formation of new gravel washovers on barrier islands points to the importance of high water levels being accompanied by high wave activity future developments in early warning systems and evacuation planning require information on the variable impacts of such extreme events

bed level motions and sheet flow processes in the swash zone observations with a new conductivity based concentration measuring technique ccm detailed measurements of bed level motions and sheet flow processes in the lower swash are presented the measurements are obtained during a large scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves a new instrument ccm provides detailed phase averaged measurements of sheet flow concentrations particle velocities and bed level evolution during a complete swash cycle the bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase sheet flow occurs during the early uprush and mid and late backwash phases sheet flow sediment fluxes during these instances are highest in the pick up layer sediment entrainment from the pick up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave backwash interactions as opposed to oscillatory sheet flow the pivot point elevation of the sheet flow layer is time varying during a swash event moreover the upper sheet flow layer concentrations do not mirror the concentrations in the pick up layer both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange such as in oscillatory sheet flows but are strongly affected by horizontal advection processes induced by the non uniformity of the flow

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

antarctic dome c ice core dust at 18 k y b p isotopic constraints on origins we have determined the source area from which dusts from the last glacial maximum lgm section of the dome c ice core were derived by comparing their strontium and neodymium isotopic ratios with those of samples from potential source areas the87sr 86sr and143nd 144nd isotope ratios of the dusts deposited 18 k y b p at the east antarctic dome c site were compared with potential antarctic australian southern african and south american sources the isotope ratios clearly define the patagonian provenance of the dust with the other potential source areas being at most minor contributors contributions by volcanic ash and tephra to the dust sample were also determined to be minimal based on the patterns of rare earth elements knowing the source of the dusts places constraints on the aeolian trajectory by which it was transported to antarctica and this serves as a test of the simulation of southern hemispheric circulation by atmospheric global circulation models during the lgm

the age of the koputaroa dunes southwest north island new zealand abstract four recent dune phases have previously been identified in the manawatu and horowhenua regions of southwest north island new zealand the oldest of these dune phases the koputaroa dunes occur over a restricted area near the town of levin previous estimates of the age of these dunes have largely been based upon the occurrence of aokautere ash an airfall member of the kawakawa tephra ca 22 14 c ka b p interbedded within the dune sands nine samples of koputaroa dune sand were collected from five sites and dated using infrared stimulated luminescence irsl the results suggest that the dunes were originally deposited at or before 40 50 ka and that they were then re mobilised in the period from 24 to 10 ka these periods of dune activity are compared with records of loess deposition in wanganui basin aeolian influx of quartz in taranaki and dust flux in the vostok ice core

precise tremor source locations and amplitude variations along the lower crustal central san andreas fault 1 we precisely locate 88 tremor families along the central san andreas fault using a 3d velocity model and numerous p and s wave arrival times estimated from seismogram stacks of up to 400 events per tremor family maximum tremor amplitudes vary along the fault by at least a factor of 7 with by far the strongest sources along a 25 km section of the fault southeast of parkfield we also identify many weaker tremor families which have largely escaped prior detection together these sources extend 150 km along the fault beneath creeping transitional and locked sections of the upper crustal fault depths are mostly between 18 and 28 km in the lower crust epicenters are concentrated within 3 km of the surface trace implying a nearly vertical fault a prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6 0 parkfield earthquake

a new 14 c age for the oruanui wairakei eruption new zealand the oruanui eruption was the largest known outburst of taupo volcano new zealand and is among the larger quaternary eruptions documented the eruption deposits are variously known as the oruanui wairakei kawakawa tephra or aokautere ash formations and represent a bulk volume probably exceeding 500 km 3 four new 14 c age determinations on carbonized vegetation in the non welded oruanui ignimbrite are combined to give a conventional age of 22590 230 yr b p compared with the previously accepted figure of 20000 yr b p this new age resolves the anomaly of apparently older 14 c ages being obtained from a demonstrably younger new zealand deposit and strengthens correlation of this eruption with an antarctic ice core acid anomaly the trace of this eruption has great potential as a time plane marker in the antarctic just prior to the last glacial maximum the close similarity in ages between the oruanui and a comparable sized eruption ito aira tn in japan suggests that this period of activity may represent the best chance of resolving any linkages between large scale explosive silicic volcanism and climate changes

tremor bands sweep cascadia 1 during the slow slip events in cascadia and japan a well documented feature of nonvolcanic tremor nvt is its puzzling slow along strike migration but the cause possible implications and underlying physics of this long term tremor migration and its relationship with slow slip remain elusive here we use tremor data recorded by a dense seismic array in cascadia and apply a beam backprojection technique to map the spatiotemporal evolution of tremor with high resolution it reveals that elongated slip parallel bands of tremor activity illuminate the slipping part of the plate interface over the time scale of several hours and sweep cascadia along strike from south to north we propose that small changes in static stress due to slow slip in a section of the fault cause slip and associated nvt activity in the adjacent section and the resulting progressive along strike transfer of stress is responsible for the long term tremor migration during a slow slip event

flow velocities sediment transport and morphological change in the swash zone of two contrasting beaches abstract as part of a large uk research project focussing on the role of swash on shoreline change two field experiments were conducted on contrasting sandy beaches a flatter dissipative beach and a steeper intermediate beach this paper describes almost 300 h of nearshore velocity data collected during this project supplemented by suspended sediment transport sediment tracer and beach profile data during both field experiments the upper part of the beach experienced progressive accretion indicating that onshore sediment transport prevailed in the swash and inner surf zones suspended sediment transport and tracer dispersal were also onshore the associated cross shore flow field was however dominated by offshore directed mean flows especially on the steeper beach velocity skewness defined as u 3 u 2 1 5 where u is the cross shore velocity and kurtosis defined as u 3 u u 2 2 were mainly directed offshore implying that energetics based sediment transport models are unable to predict the direction of sediment transport in the swash zone possible explanations for the observed accretion include enhanced bed shear stress on the uprush due to in exfiltration effects flow acceleration and or bore turbulence and advection of bore entrained sediment into the swash zone

thermoluminescence chronology of sand profiles in the mu us desert china abstract thermoluminescence tl is used to calculate the ages of two sand loess profiles in the marginal zone of the mu us desert china alternating units of dune sand and loess with palaeosols in the two profiles imply episodes of dune formation separated by periods of loess accumulation and pedogenesis our results indicate that there are three layers of dune sand intercalated in sediments of the last full glacial cycle suggesting the occurrence of three arid episodes during this time the first arid episode within this period occurred between

climate of the last glaciation in new zealand based on aerosolic quartz influx in an andesitic terrain abstract on western north island new zealand a record of climatic change during the last glaciation is preserved in a terrestrial coverbed sequence of dominantly andesitic provenance here a succession of five loess like andisol units postdates the global high sea level stand of oxygen isotope substage 5e

late quaternary geomorphology of the manawatu coastal plain north island new zealand this review examines the geomorphological evolution of the manawatu coastal plain from the last glacial maximum through the holocene post glacial marine transgression c 7500 cal yr bp until the present providing a context within which to examine the extent to which the holocene evolution of the lower manawatu valley follows tripartite evolutionary models of incised valley infill during the last glaciation the manawatu river incised a broad deep valley while tributaries within the catchment dissected relict marine terraces this occurred concurrently with the formation of a parabolic dune field at koputaroa with sediment sourced from the bars of the manawatu river during the post glacial marine transgression rising sea levels inundated the incised valley at the culmination of the holocene marine transgression the himatangi anticline and poroutawhao high restricted oceanic influences in the proto manawatu estuary which was partially infilled with estuarine sediment estuarine deposition was quickly succeeded by fluvial deposition and floodplain due to high volumes of fluvial sediment introduced by the manawatu river a lack of characteristic bay head delta development may be explained by rapid infill and consequent sediment bypass

tremors along the queen charlotte margin triggered by large teleseismic earthquakes 1 we conduct a systematic search of tectonic tremors along the queen charlotte margin qcm in western canada triggered by distant earthquakes we identify triggered tremor as non impulsive high frequency signals coherent among several stations and coincident with passing surface waves so far the 2002 mw7 9 denali fault the 2004 mw9 2 sumatra and the 2011 mw9 1 tohoku oki earthquakes have triggered clear tremor in this region the 2010 mw8 8 maule chile and the 2012 mw8 6 sumatra earthquakes may have triggered but tremors in these two cases did not meet all of our criteria the triggered tremors are mostly located east of the queen charlotte fault in the southern portion of haida gwaii near the epicenter of the 28 october 2012 mw7 7 earthquake similar to the observations in other regions the triggered tremors were initiated by the love waves and continued during the subsequent rayleigh waves tremor bursts correlate with both the particle velocity and displacement of the love waves indicating they are triggered at either low angle thrust or vertical strike slip faults in addition we find that the triggering potential for the qcm is controlled by a combination of amplitude period and incident angles

porosity and packing of holocene river dune and beach sands the porosity and packing of 174 samples of surficial and shallowly buried to 17 m unconsolidated holocene sands medium to coarse grained were determined by point counting the upper surface of thin sections of epoxy impregnated samples in reflected light average depositional porosity for 124 surficial sands from beaches river point bars and braid bars and eolian dunes respectively is 47 48 and 49 the porosity values range between 40 and 58 beach sands exhibit an average packing value ci contact index of 0 79 fluvial sands an average ci of 0 91 and eolian sands an average ci of 1 02 beach sands typically contain 5 5 oversized pores river sands 3 8 oversized pores and eolian dune sands 4 0 oversized pores most oversized pores are depositional packing defects although trapped air bubbles are common in some beach sands extrapolation of our data for buried samples indicates depositional oversized pores are destroyed at a depth of less than 100 m average porosity is 46 for eolian ripple strata 50 for grain fall strata and 51 for grain flow strata differences in packing are significant for grain flow versus grain fall strata and for ripple versus grain flow strata for samples of similar grain size porosity is more uniform within individual beds from a river and a beach than among different beds at the same localities porosity of ancient sandstones from a particular bed or facies may be as uniform as sampled holocene sands unless cements having patchy distribution such as carbonate or anhydrite are present compaction associated with burial to 17 m is minor packing is tighter but our technique of measuring porosity is not sensitive enough to show any decrease in porosity changes in packing and porosity upon burial to common hydrocarbon reservoir depths will depend on individual histories of cementation compaction and secondary porosity development however if only physical compaction of quartzose river dune and beach sands takes place porosity would approach a limiting value of 26 and ci would approach 5 5

suspended sediment transport around a large scale laboratory breaker bar this paper presents novel insights into suspended sediment concentrations and fluxes under a large scale laboratory plunging wave measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar covering the complete breaking region from shoaling to inner surf zone with particular high resolution near the bed using an acoustic concentration and velocity profiler wave breaking evidently affects sediment pick up rates which increase by an order of magnitude from shoaling to breaking zone time averaged reference concentrations correlate poorly with periodic and time averaged near bed velocities but correlate significantly with near bed time averaged turbulent kinetic energy the net depth integrated suspended transport is offshore directed and primarily attributed to current related fluxes undertow at outer flow elevations i e above the wave bottom boundary layer the wave related suspended transport is onshore directed and is generally confined to the wave bottom boundary layer cross shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick up and deposition and of cross shore sediment advection suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion leading to local intra wave concentration changes at locations between the breaker bar crest and bar trough intra wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer sediment is entrained in the bar trough during the wave trough phase almost instantly advected offshore and deposited near the bar crest during the wave crest phase finally these results are used to suggest improvements for suspended sediment transport models

space time correlation of slip and tremor during the 2009 cascadia slow slip event 1 episodic tremor and slip ets involving transient deformations accompanied by emergent low frequency tremor occurs in subduction zones around the world ets events increase the shear stress on locked megathrusts and may potentially trigger damaging earthquakes despite the clear association of tremor and slip the physical relationship between them is unresolved tremor appears to result from slip on small asperities on the plate interface due to either creep on the surrounding fault or stress increases ahead of the propagating slow slip front previous studies of migrating slow slip events have not had sufficient spatial and temporal resolution to differentiate between these two models to address this we invert gps data from the august 2009 ets event in central cascadia for the space time evolution of fault slip rate we find a correlation in both space and time between tremor epicenters and the independently determined position of high fault slip rate this supports the first hypothesis that tremor asperities are loaded directly by slow slip rather than by stress increases ahead of the slip front and provides new insights into the mechanics of ets

large scale experiments on beach profile evolution and surf and swash zone sediment transport induced by long waves wave groups and random waves new large scale laboratory data are presented on the influence of long waves bichromatic wave groups and random waves on sediment transport in the surf and swash zones physical model testing was performed in the large scale ciem wave flume at upc barcelona as part of the susco swash zone response under grouping storm conditions experiment in the hydralab iii program vicinanza et al 2010 fourteen different wave conditions were used encompassing monochromatic waves bichromatic wave groups and random waves the experiments were designed specifically to compare variations in beach profile evolution between monochromatic waves and unsteady waves with the same mean energy flux each test commenced with approximately the same initial profile the monochromatic conditions were perturbed with free long waves and then subsequently substituted with bichromatic wave groups with different bandwidth and with random waves with varying groupiness beach profile measurements were made at half hourly and hourly intervals from which net cross shore transport rates were calculated for the different wave conditions pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross shore sediment transport patterns giving high confidence to the data set consistent with recent small scale experiments the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions the random waves have a similar influence to the bichromatic wave groups promoting offshore transport in comparison to the monochromatic conditions the data also indicate that the free long waves promote onshore transport but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time the experiments suggest that the inclusion of long wave and wave group sediment transport is important for improved near shore morphological modeling of cross shore beach profile evolution and they provide a very comprehensive and controlled series of tests for evaluating numerical models it is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups as much as the presence of the forced and free long waves induced by the groupiness the equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic waves with the same incident energy flux

extreme wave activity during 2013 2014 winter and morphological impacts along the atlantic coast of europe studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise rather than the complex coastal responses resulting from changes to the extreme wave climate here we investigate the 2013 2014 winter wave conditions that severely impacted the atlantic coast of europe and demonstrate that this winter was the most energetic along most of the atlantic coast of europe since at least 1948 along exposed open coast sites extensive beach and dune erosion occurred due to offshore sediment transport more sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport storm wave conditions such as were encountered during the 2013 2014 winter have the potential to dramatically change the equilibrium state beach gradient coastal alignment and nearshore bar position of beaches along the atlantic coast of europe

geomagnetic field control of 14c production over the last 80 ky implications for the radiocarbon time scale we have used a recent estimate of the geomagnetic dipole field strength over the last 80 ky to examine the extent to which changes in geomagnetic field intensity have affected the radiocarbon time scale the magnetic record was converted into a 14c production signal which was then used to produce a synthetic atmospheric 14c record using a two box model for the carbon cycle this calibration suggests that the geomagnetic field has been the main factor governing the production of cosmogenic 14c atoms over the period of time considered and that 14c changes due to other causes such as climatic changes have been of lesser importance the results indicate that the radiocarbon ages are 2 to 3 ky younger than true age in the interval 18 40 ky b p in good agreement with recent u th and 14c age comparisons moreover the results predict that a negligible difference between true and 14c ages should be observed around 45 50 ky

sediment transport processes and morphodynamics on a reflective beach under storm and non storm conditions abstract new field experiments of sediment transport on the shoreface of a reflective beach r 0 4 0 6 during pre storm storm and post storm conditions are reported data were collected outside the breakpoint and include water surface elevations cross shore and long shore flow velocity suspended sediment concentrations bedform dimensions and the morphological response instruments included two pulse coherent adps an adv multiple obs and a pencil beam sonar the depth averaged mean velocity was always offshore and increased by a factor five during the storm and this increase is attributed to undertow being enhanced by strong backwash plumes from cusp bays estimates of cross shore suspended sediment transport are landward during the pre and post storm phases consistent with the morphological response during the storm the shoreface quickly appeared to reach equilibrium despite energy levels being maintained with sediment transport rates reducing rapidly after the initial phase of the storm streaming in the wave boundary layer was observed and strongest during the pre storm phase consistent with the observed shoreward transport during the storm the near bed streaming was too small to reverse the increased offshore current consistent with the observed net offshore transport the generally small orbital velocity skewness observed on this steep reflective beach suggests that wave reflection may reduce the overall skewness of the velocity in turn contributing to the stability of reflective beach types

detecting deep tectonic tremor in taiwan with a dense array abstract we perform a systematic detection of deep tectonic tremor beneath the southern central range in taiwan using a dense small aperture seismic array deployed in february 2011 the array has been recording tectonic tremor nearly continuously for 134 days including tremor triggered by the 2011 m w 9 0 tohoku oki earthquake we use broadband frequency wavenumber beamforming and moving window grid search methods to compute array parameters for all continuous data and identify tremor as coherent nonimpulsive seismic signals with deep incidence angles the obtained array parameters closely match with those of relocated local earthquakes and triggered tremor bursts located by the waveform envelope correlation and clustering wecc method indicating the robustness of our array technique during the 134 day study period we detect tremor for 44 days with a total duration of 1481 min three to six times as long as the detection of tremor by the wecc method we find a relative quiescence in ambient tremor activity for about 20 days following the 2011 tohoku oki earthquake suggesting that dynamic stresses from the distant mainshock triggered most tremor close to failure resulting in a temporary lack of tremor activity in some cases we observe rapid tremor migration with a speed at the order of 40 50 km hr that is similar to the speed of fast tremor migration along dip on narrow streaks in japan and cascadia our results suggest that dense array techniques are capable of capturing detailed spatiotemporal evolutions of tremor behaviors in southern taiwan online material tables of station coordinates and tremor event parameters and figures of the moving window grid search test with local earthquakes tremor triggered by the 2011 tohoku oki earthquake and additional examples of detected ambient tremors

sediment transport and beach morphodynamics induced by free long waves bound long waves and wave groups new laboratory data are presented on the influence of free long waves bound long waves and wave groups on sediment transport in the surf and swash zones as a result of the very significant difficulties in isolating and identifying the morphodynamic influences of long waves and wave groups in field conditions a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences the evolution of model sand beaches each with the same initial plane slope was measured for a range of wave conditions firstly using monochromatic short waves subsequently the monochromatic conditions were perturbed with free long waves and then substituted with bichromatic wave groups with the same mean energy flux the beach profile changes and net cross shore transport rates were extracted and compared for the different wave conditions with and without long waves and wave groups the experiments include a range of wave conditions e g high energy moderate energy low energy waves which induce both spilling and plunging breakers and different turbulent intensities and the beaches evolve to form classical accretive erosive and intermediate beach states the data clearly demonstrate that free long waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions in contrast wave groups which can generate both forced and free long waves generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions the influence of the free long waves and wave groups is consistent with the concept of the relative fall velocity h wst as a dominant parameter controlling net beach erosion or accretion free long waves tend to reduce h wst promoting accretion while wave groups tend to increase the effective h wst promoting erosion

sediment transport partitioning in the swash zone of a large scale laboratory beach abstract swash zone sheet flow and suspended sediment transport rates are estimated on a coarse sand beach constructed in a large scale laboratory wave flume three test cases under monochromatic waves with wave heights of 0 74 m and wave periods of 8 and 12 2 s were analyzed sediment flux in the sheet flow layer exceeds several hundred kg m 2 s 1 during both uprush and backwash suspended sediment flux is large during uprush and can exceed 200 kg m 2 s 1 instantaneous sediment flux magnitudes in the sheet layer are nearly always larger than those for suspended sediment flux however sediment transport rates those integrated over depth indicate that suspended load transport is dominant during uprush for all cases and during the early stages of backwash except in the case for the 12 2 s wave case when the foreshore was steeper results could not be obtained for an entire swash event and were particularly truncated during backwash when water depths fell below the elevation of the lowest current meter

laboratory investigation of coastal beach erosion processes under storm waves of slowly varying height abstact storm induced large coastal waves are a predominant driver for coastal erosion problems but the physical processes of storm erosion have not been fully understood due to some technical difficulty in simulating storm waves with timely varying heights in the laboratory and collecting storm beach profiles in the field in this study novel series of experiments are proposed to study sandy beach processes under coastal storm conditions in a laboratory wave flume of 60 m long 3 m wide and 1 5 m high two water depths of h 0 5 m and h 0 7 m were used to investigate beach response under low and high tidal levels two initially uniform plane beach slopes of tan 1 15 for dissipation beach and tan 1 5 for reflection beach were used to study beach profile changes additionally intermediate beach tan 1 10 was also experimentally investigated under regular waves in another wave flume of 30 m long 0 6 m wide and 1 m high non intrusive instrumentation of high resolution cameras was used to record time series photo images on beach profile evolution in spatial resolution of 0 2 cm and a temporal resolution of 0 1 s image analyzing techniques were also developed to transform the recorded photo images to digital data on both beach and water surface profiles in analyzing the collected data it is found that the variation of storm wave height results in changes of wave breaking point and also sediment transport direction before and after the wave breaking point sediment transport direction was found to move onshore initially under small storm waves and then a sand bar was generated and a certain portion of sediment also moved offshore under large waves but such monotonic relationship between sediment transport and wave forcing could transform as morphology feedback and phase lags between wave orbital fluid velocity and sediment concentration the wave energy flux at the breaking point is shown to be suitable parameter in predicting beach mass change or storm erosion rate while the dimensionless sediment settling velocity parameter may not be a suitable criterion for predicting beach erosion or accretion under storm waves

an optical luminescence chronology for late pleistocene aeolian activity in the colombian and venezuelan llanos the lowland savannas llanos of colombia and venezuela are covered by extensive aeolian landforms for which little chronological information exists we present the first optically stimulated luminescence osl age constraints for dunes in the llanos orientales of lowland colombia and new ages for dunes in the venezuelan llanos the sampled dunes are fully vegetated and show evidence of post depositional erosion ages range from 4 5 0 4 to 66 4 ka with the majority dating to 27 10 ka marine isotope stage 2 some dunes accumulated quickly during the last glacial maximum although most were active 16 10 ka accretion largely ceased after 10 ka all dunes are elongated downwind from rivers parallel with dry season winds and are interpreted as source bordering features as they are presently isolated from fluvial sediments by gallery forest it is proposed that activity was associated with a more prolonged dry season which restricted gallery forest leading to greater sediment availability on river shorelines such variability in dry season duration was potentially mediated by the mean latitude of the itcz the cessation of most dune accretion after ca 10 ka suggests reduced seasonality and a more northerly itcz position consistent with evidence from the cariaco basin

fingerprints and age models for widespread new zealand tephra marker beds erupted since 30 000 years ago a framework for nz intimate abstract the role of tephras in the nz intimate project is a critical one because most high resolution palaeoclimatic records are linked and dated by one or more tephra layers in this review first we document eruptive distributional and compositional fingerprinting data both mineralogical and geochemical for 22 key marker tephras erupted since 30 000 years ago to facilitate their identification and correlation we include new glass compositional data the selected marker tephras comprise 10 from taupo and nine from okataina volcanoes rhyolitic one from tuhua volcano peralkaline rhyolitic and one each from tongariro and egmont volcanoes andesitic second we use four approaches to develop 2 age models for the tephras youngest to oldest 1 calendar ages for kaharoa and taupo y were obtained by wiggle matching log derived tree ring sequences dated by 14c 2 whakaipo v was dated using an age depth model from peat 3 14 tephras in the montane kaipo peat sequence waimihia s unit k whakatane tuhua mamaku rotoma opepe e poronui c karapiti b okupata konini waiohau rotorua rerewhakaaitu were dated by simultaneously wiggle matching stratigraphic position and 51 independent 14c age points against intcal04 using bayesian probability methods via both oxcal and bpeat and 4 the five oldest tephras erupted before ca 18 000 cal yr bp were dated by calibrating limited numbers of 14c ages using intcal04 okareka or comparison curves of the expanded cariaco basin sequence te rere kawakawa oruanui poihipi okaia kawakawa oruanui tephra the most widely distributed marker tephra was erupted probably ca 27 097 957 cal yr bp potential dating approaches for the older tephras include their identification in antarctic ice cores if present or annually laminated sediments for which robust calendar age models have been constructed high precision ams 14c dating on appropriate material from environmentally stable sites systematic luminescence dating or new radiometric techniques e g u th he if suitable minerals are available and errors markedly reduced further application of bayesian age modelling to stratigraphic sequences of 14c ages possibly augmented with luminescence ages may help refine age models for pre holocene tephras with the largest errors finally we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the new zealand region which is a key objective of australasian and southern hemisphere intimate projects