geophysical surveys of a pluvial lake barrier deposit beatty junction death valley california usa abstract we used ground penetrating radar gpr and seismic refraction to image the internal stratigraphy of a beach barrier deposit at beatty junction northern death valley to better understand its depositional environment in the context of variations in the level of the former lake manly the deposit is a gravelly bar 500 m long with 4 m of surface relief that formed at a shoreline of lake manly during the end of the last pleistocene ice age the gpr profiles provide subsurface images that we interpret as progradational foreset beachface strata in the uppermost 2 m and the surface of an earlier bar at depths of 2 to 6 m we conclude that the crest of the bar migrated in a landward direction during the construction of the uppermost 4 m of the bar as lake level rose the seismic survey indicates a sharp velocity increase from 760 m s to 1510 m s at the base of the bar which we interpret as the boundary between well sorted gravelly beach deposits and underlying older fan deposits the depth of the base of the bar varies between 5 m and 10 m the elevation of the bar is comparable to that of other shoreline features in death valley that formed during the mis 6 5e 186 120 ka highstand measurements of fault slip on the nearby northern death valley fault have documented only strike slip motion in absence of any evidence for significant vertical uplift in the area during the late pleistocene and holocene we conclude that the bar probably formed during mis 6 5e this conclusion is subject to uncertainty due to discrepancies in age dates reported for the deposit

coarse clastic barrier environments evolution and implications for quaternary sea level interpretation abstract this paper reviews recent work particularly from eastern canada on the dynamics and evolution of coarse clastic barriers it is argued that an understanding of quaternary coastal changes on paraglacial glacially influenced coasts can only be achieved with a knowledge of gravel barrier morphodynamics and sedimentation gravel barriers are distinctive coastal forms in which morphological inheritance and sediment sorting provide major behavioral controls spatially adjacent gravel barriers may display different depositional tendencies prograde seawards migrate landward or aggrade vertically such inconsistent spatial behaviour must be considered in terms of an erosional front advancing landward under stationary or rising sea level redistribution of sediment across or along the erosional front supplies sediment for the development of gravel barriers which in turn provides environments for fine grained deposition which is favourable for further barrier migration an example of an erosional front is given from chezzetcook inlet nova scotia three stages are recognized in the development of gravel barriers starting with the initiation of small drift aligned forms at the leading edge of the erosional front as sea level rises this is followed by a period of consolidation and stabilization when drift aligned forms may become swash aligned conditions for this transition are discussed under rising sea levels it is difficult to explain the conditions leading to the formation of multiple parallel swash aligned ridges although three hypotheses are advanced all of which may operate in different locations the third stage is associated with the breakdown of barriers as sediment supply fails and or sea level rises drift aligned forms are inherently unstable and show signs of pre breakdown stress in the form of reworking and remobilization of proximal sediments into cells swash aligned barriers may be breached revert to drift alignment become segmented or be overstepped some gravel is re incoporated in barriers farther landward while other material is passed seaward of the erosional front and becomes abandoned on the shoreface gravel barriers may exert a major influence on estuary and back barrier environments especially where they control the depositional record the implications for the reconstruction and interpretation of quaternary environments are summarized

quantitative constraints on the sea level fall that terminated the littorina sea stage southern scandinavia abstract the island of anholt in the kattegat sea southern scandinavia is made up largely of an extensive beach ridge plain as a result of post glacial uplift the earliest beach ridge and swale deposits are now raised 8 9 m above present mean sea level it appears that growth of the plain has been almost uninterrupted over the past 7500 years here we constrain the evolution of this plain between 6300 and 1300 years ago using optically stimulated luminescence dates the topography and internal architecture of the fossil shoreline deposits were measured on high resolution maps and in ground penetrating radar gpr reflection data with a vertical resolution of 0 25 m shoreline topography shows significant changes with time and it appears that one of the most striking changes took place between 4300 and 3600 years ago in the shoreline deposits corresponding to this time interval the surface drops by around 3 5 m suggesting a marked fall in relative sea level assuming a constant uplift rate of 1 2 mm yr the corresponding drop in absolute sea level is estimated to be around 2 6 m this marked sea level fall in 700 years took place at the transition from the middle holocene thermal maximum to the late holocene thermal decline or at the end of the littorina sea stage in the baltic sea region

coastal lagoons and beach ridges as complementary sedimentary archives for the reconstruction of holocene relative sea level changes coastal lagoons and beach ridges are genetically independent though non continuous sedimentary archives we here combine the results from two recently published studies in order to produce an 8000 year long record of holocene relative sea level changes on the island of samso southern kattegat denmark the reconstruction of the initial mid holocene sea level rise is based on the sedimentary infill from topography confined coastal lagoons sander et al boreas 2015b sea level index points over the mid to late holocene period of sea level stability and fall are retrieved from the internal structures of a wide beach ridge system hede et al the holocene 2015 data from sediment coring georadar and absolute dating are thus combined in an inter disciplinary approach that is highly reproducible in micro tidal environments characterised by high sediment supply we show here that the commonly proximate occurrence of coastal lagoons and beach ridges allows us to produce seamless time series of relative sea level changes from field sites in sw scandinavia and in similar coastal environments

sedimentology of coarse clastic beach ridge deposits essex southeast england abstract the distinction of cheniers from other types of beach ridge can often be problematic the stratigraphy sedimentology and geomorphological development of sand and gravel rich beach ridges at three sites on the northern essex coast england were determined using ground penetrating radar gpr ground truthing trenches and auger holes and historical aerial photograph analysis the 900 mhz gpr system used achieved a maximum vertical resolution between 0 02 and 0 06 m there was good correspondence between the radar stratigraphy obtained from time migrated radar reflection profiles and the nature and form of bounding surfaces sets of lamination beds and bedsets observed in trenches data for one of the study sites colne point illustrate a complex beach ridge stratigraphy and sequence of development that confirms they are not true cheniers instead the ridges form part of both retrogradational and progradational barrier spit sequences chenier designation at the other two study sites foulton hall and stone point is more straightforward as the beach ridges lie at the junction between actively eroding mudflat and saltmarsh however despite the distinction between the barrier spit beach ridges and the cheniers the same types of deposit are recognised in both indicating similar formative processes washover sheet deposits consist of low angle

on the structure of the regional scale circulation over central africa seasonal evolution variability and mechanisms abstractatmospheric circulation over central africa is dominated by the tropical easterly jet the african easterly jet and the low level westerly jet in the lower troposphere a zonal overturnin

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

proxy records of holocene storm events in coastal barrier systems storm wave induced markers abstract extreme storm events in the coastal zone are one of the main forcing agents of short term coastal system behavior as such storms represent a major threat to human activities concentrated along the coasts worldwide in order to better understand the frequency of extreme events like storms climate science must rely on longer time records than the century scale records of instrumental weather data proxy records of storm wave or storm wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia this review provides a detailed state of the art compilation of the proxies available from coastal barrier systems to reconstruct holocene storm chronologies paleotempestology the present paper aims i to describe the erosional and depositional processes caused by storm wave action in barrier and back barrier systems i e beach ridges storm scarps and washover deposits ii to understand how storm records can be extracted from barrier and back barrier sedimentary bodies using stratigraphical sedimentological micro paleontological and geochemical proxies and iii to show how to obtain chronological control on past storm events recorded in the sedimentary successions the challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm chronologies using these various proxies are discussed and future research prospects are outlined

role of continents in driving the hadley cells gcm simulations are used to investigate how forcing that originates over land surfaces influences the hadley circulation the presence of continental surfaces is found to approximately double the intensity of the winter hemisphere hadley cell and to halve the intensity of the summer cell the strengthening of the winter cell occurs because the increase in surface friction associated with land enhances the angular momentum flux into the atmosphere the development of strong monsoon circulations in the northern hemisphere summer and the convergence zones of the southern hemisphere south pacific south atlantic and south indian convergence zones shifts mass out of the subtropics lowers the zonal mean subtropical highs and weakens the summer cells the responses of the summer and winter cells are different signs and occur by different processes because heating of the land surfaces in the summer is effectively communicated through the depth of the atmosphere whereas cooling in the winter is not also the higher surface wind speeds and shears of the winter hemisphere trade winds make the winter cell more sensitive to surface friction than the summer cell these results suggest that the axisymmetric models that have provided a theoretical basis for the understanding of the hadley circulation do not capture some of the important physical processes that determine the intensity of the mean meridional circulation

radarfacies and sedimentological analysis study of sedimentary substrate from an archaeological site shell mound southern brazil integrated results of gpr ground penetrating radar and sedimentological analysis are presented for the jabuticabeira ii archaeological site shell mound santa catarina brazil by means of rada

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

decoupling of pacific subduction zone guided waves beneath central japan evidence for thin slab the fine scale seismic structure of the northeast japan subduction zone is studied based on waveform analyses of moderate sized m4 5 6 deep focus earthquakes h 350 km and the finite difference method fdm simulation of high frequency up to 8 hz wave propagation strong regional s wave attenuation anomalies for specific source receiver paths connecting the cluster of events occurring in central part of the sea of japan recorded at fore arc stations in northern and central japanese islands honshu are used to model the deeper structure of the subducting pacific plate where recent teleseismic tomography has shown evidence for a possible slab tear westward beneath the sea of japan the character of the observed anomalous s wave attenuation and the following high frequency coda can be captured with the two dimensional 2 d fdm simulation of seismic waves in heterogeneous plate model incorporating the thinning of the plate at depth which is also compared with other possible causes of dramatic attenuation of high frequency s wave due to low q or much weaker heterogeneities in the slab the results of simulation clearly demonstrate that the dramatic loss of high frequency s wavefield from the plate into the surrounding mantle occurred due to the variation in the plate geometry i e thinning of the plate at depth near the source rather than due to variation in physical properties such as due to the lowered q and weaker heterogeneities in the plate the presence of such a thin zone defocuses the high frequency slab guided s wave energy from the subducting plate into the surrounding mantle and acts as a geometric antiwaveguide based on the sequence of simulation results obtained we propose thinning of pacific plate at depth subducting beneath northeastern japan localized to central part of honshu in agreement with the observations

insight into the late holocene sea level changes in the nw atlantic from a paraglacial beach ridge plain south of newfoundland constructional sedimentary features can provide insight into past changes in relative sea level rsl in regions where traditional bio stratigraphic markers are absent the paraglacial beach ridge plain at miquelon langlade located 50 km south of newfoundland is an example of a well preserved regressive barrier initiation of this plain correlates with a decrease in the rate of rsl rise from 4 4 mm yr to 1 3 mm yr at around 3000 years ago it developed under conditions of normal regression during a period of slow rsl rise 1 3 mm yr the barrier is composed of two oppositely prograding mixed sand and gravel beach ridge systems which evolved contemporaneously along two open coasts the growth of these features reflects high rates of sediment influx that was sourced from the erosion of proximal glacigenic sediment moraines and reworked alongshore and across shore by wave action the combination of stratigraphic ground penetrating radar and sediment cores topographic rtk gps and chronologic optically stimulated luminescence osl data provide a detailed understanding of the constructional history of the plain the well defined contact between coarse grained wave built facies and overlying aeolian deposits is used to demonstrate the dominant influences of rsl change in the development of the barrier system and produce a rsl curve over the period of its formation a net increase of 2 4 m in the surface elevation of wave built facies is observed across the plain corresponding to the increase in mean sea level during its formation coupled with osl dates trends in elevation of the wave built facies across the plain are used to reconstruct the relative sea level history during this period acknowledging the uncertainties inherent in the method applied in this study three distinct periods of sea level rise can be distinguished 1 an increase from 2 4 to 1 m below modern msl between 2400 and 1500 years average rate of 1 3 mm yr 2 relatively stable or slowly rising rsl 0 2 mm yr from 1400 to 700 years and 3 a rise of ca 0 7 m during the past 700 years 1 1 mm yr this study not only produces the first rsl reconstruction for the saint pierre et miquelon archipelago but also provides i additional details of rsl changes in a region exhibiting great spatial variations in rsl histories newfoundland ii field confirmation that wave built aeolian stratigraphic contacts in beach ridges can provide a powerful tool for sea level reconstructions in mixed clastic systems and iii evidence that sediment influxes can outpace the rate of accommodation creation producing a broad progradational coastal system

punctuated progradation of the seven mile beach holocene barrier system southeastern tasmania abstract prograded barriers are depositional coastal landforms which preserve past shoreline locations and have been studied in order to understand the fundamental drivers of barrier formation this paper reconstructs the holocene history of the seven mile beach prograded barrier in tasmania australia using optically stimulated luminescence osl dating ground penetrating radar gpr light detection and ranging lidar elevation models and sedimentological analyses shoreline progradation of the barrier commenced around 7300 years ago and continued to near present despite a 3000 pause in deposition between 6700 and 3600 years ago indicative of substantial changes in sediment availability gpr imaged subsurface structures contain a record of seaward dipping reflectors preserved as sediment supplied beaches and dunes leading to shoreline progradation in the past 500 years a large transgressive dune has formed built from reworked barrier sands and now dominates the eastern portion of the barrier implying that shoreline progradation has ceased this study reaffirms the notion that relict foredune ridges are strongly aligned with modal wave refraction patterns in planform and emphasises the importance of sediment delivery as a key driver of shoreline progradation through beachface and dune accretion the substantial pause in shoreline progradation on this barrier system as observed on others around the world requires further explanation although changes in sediment delivery have been inferred it may also be appropriate to reopen the debate on holocene sea level change in tasmania

quantifying rates of coastal progradation from sediment volume using gpr and osl the holocene fill of guichen bay south east south australia guichen bay on the south east coast of south australia faces west towards the prevailing westerly winds of the southern ocean the bay is backed by a 4 km wide holocene beach ridge plain with more than 100 beach ridges the morphology of the guichen bay strandplain complex shows changes in the width length height and orientation of beach ridges a combination of geomorphological interpretation shallow geophysics and existing geochronology is used to interpret the holocene fill of guichen bay six sets of beach ridges are identified from the interpretation of orthorectified aerial photographs the ridge sets are distinguished on the basis of beach ridge orientation and continuity a 2 25 km ground penetrating radar gpr profile across the beach ridges reveals the sedimentary structures and stratigraphic units the beach ridges visible in the surface topography are a succession of stabilized foredunes that overlie progradational foreshore and upper shoreface sediments the beach progrades show multiple truncation surfaces interpreted as storm events the gpr profile shows that there are many more erosion surfaces in the subsurface than beach ridges on the surface the width and dip of preserved beach progrades imaged by gpr shows that the shoreface has steepened from around 2 9 to around 7 5 the changes in beach slope are attributed to increasing wave energy associated with beach progradation into deeper water as guichen bay was infilled at the same time the thickness of the preserved beach progrades increases slightly as the beach prograded into deeper water using the surface area of the ridge sets measured from the orthophotography and the average thickness of upper shoreface foreshore and coastal dune sands interpreted from the gpr profile the volume of holocene sediments within three of the six sets of beach ridge accretion has been calculated combining optically stimulated luminescence osl ages and volume calculations rates of sediment accumulation for ridge sets 3 4 and 5 have been estimated linear rates of beach ridge progradation appear to decrease in the mid holocene however the rates of sediment accumulation calculated from beach volumes have remained remarkably consistent through the mid to late holocene this suggests that sediment supply to the beach has been constant and that the decrease in the rate of progradation is due to increasing accommodation space as the beach progrades into deeper water changes in beach ridge morphology and orientation reflect environmental factors such as changes in wave climate and wind regime

a holocene coastal aeolian system vejers denmark landscape evolution and sequence stratigraphy stratigraphical studies of holocene aeolian strata formed at the inner margin of the vejers dunefield on the west coast of jutland have contributed to an understanding of aeolian landscape evolution in a storm influenced temperate climate belt the aeolian system was characterized by alternating periods of activity and stabilization intense inland sand transport occurred just after 4000 bc 2300 bc 600 bc and ad 300 500 periods of sand movement were apparently initiated during climatic shifts towards more stormy conditions and they may be linked to a millennial scale cycle in north atlantic holocene climate preservation of the accumulated aeolian sand records a long term rise in ground water level water table behaviour was initially controlled by sea level but after about 2300 bc water table rise was linked to coastal outbuilding and to an overall change towards a more humid climate

ground penetrating radar antennae frequencies and transmitter powers compared for penetration depth resolution and reflection continuity1 twelve ground penetrating radar gpr experiments were conducted on the modern wave influenced william river delta on the southern shore of lake athabasca in northern saskatchewan canada the delta is a well sorted quartzoserich clean sand dominated water saturated geomorphic feature which provided an ideal site to test gpr penetration depths resolution and continuity of reflections were compared for different antennae frequencies 25 50 100 200 mhz and transmitter powers pulser voltage 400 v 1000 v the data show significant variations in vertical resolution from 0 15 m to 0 76 m 200 25 mhz depth of penetration from 14 m 28 m 200 25 mhz and continuity of reflections increasing the transmitter power from 400 v to 1000 v increases the depth of penetration by 5 to 14 and improves the continuity of reflections with little effect on the resolution

sedimentary records of extreme wave events in the southwestern caribbean abstract high energy events in the caribbean sea include hurricanes tropical storms cold fronts and tsunamis el rosario archipelago located on the colombian caribbean shelf sw caribbean consists of a set of ancient and successive coralline formations uplifted by tectonic and diapiric activity we undertook an integrated analysis of instrumental climate records and sediment records from a beach ridge system a reef lagoon and a mangrove lagoon in the archipelago to determine whether historical extreme weather events influenced the coastal geomorphology and reef sedimentation statistical analysis of historical extreme winds and waves was accomplished using era interim reanalysis data extreme sea level events were identified with calibrated data from the nearest tide gauge sediments from the reef and mangrove lagoon were dated using 210pb and 14c beach ridges were dated indirectly thorough their relationship with the closure of the mangrove lagoon the eroding capacity of the historical extreme waves i e maximum grain size that could be entrained by the orbital velocity of the waves was compared with the grain sizes present in the deposits and foraminifera species helped to determine the provenance of those deposits storms typically occur during the dry season associated with cold fronts foraminifera and coral fragments indicated that beach ridges were supplied with sediment that eroded from ancient terraces in the reef lagoon a 56 cm thick unit of coarse coral and shell debris grading to a finer sediment represents a major high energy event that occurred after ca 1655 ce this event was also recorded by the beach ridges the probable explanation for this high energy unit is that a strong event carried coarse sediments into the lagoon with subsequent reworking by minor events such as those reported in the historical record two tsunamis occurred in the caribbean after 1655 but the associated waves reaching the area were not strong enough to deposit the coarser clasts of the unit thus coarser material was probably delivered to the lagoon as a consequence of sudden diapiric and or tectonic activity our data show that major storms and other high wind extreme wave events shape the beach ridges on rosario island every 70 years the findings suggest that if global climate change increases the frequency and or magnitude of major storms and other high wind extreme wave events that impact the caribbean coast of colombia then el rosario archipelago will be susceptible to future significant landscape transformations

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

acquisition and processing of wide aperture ground penetrating radar data a 40 channel wide aperture ground penetrating radar gpr data set was recorded in a complicated fluvial aeolian environment in eastern canada the data were collected in the multichannel format usually associated with seismic reflection surveys and were input directly into a standard seismic processing sequence filtering static corrections common midpoint gathering velocity analysis normal and dip moveout corrections stacking and depth migration the results show significant improvements over single channel recordings in noise reduction and depth of penetration by stacking and in spatial positioning and reduction of diffraction artifacts by migration these characteristics increase the potential for reliable interpretation of structural and stratigraphic details thus without having to develop any new software gpr data processing technology is brought to the same level of capability flexibility and accessibility that is current in seismic exploration

depositional architecture of a wave dominated clastic shoreline pilmatue member argentina linking dynamics and stratigraphic record of bar trough systems abstract bar trough morphologies are a dominant feature of modern wave dominated clastic shorelines despite these barred configurations being widely described from modern systems there is still some uncertainties associated with their interpretation in the ancient record there is a lack of detailed outcrop based studies describing the facies distribution and architecture within bar trough systems which causes a disparity between observations of modern processes and the subsequent preserved rock record this work presents a detailed characterization and interpretation of the sedimentary record of a bar trough setting this was achieved through the analysis of nearshore i e upper shoreface and foreshore deposits within a parasequence in the lower cretaceous pilmatue member of the agrio formation neuquen basin argentina a high resolution facies and architectural analysis was developed combining detailed sedimentary logs with the mapping of bounding and internal surfaces within the nearshore deposits the facies analysis suggests that trough and planar cross bedded facies are remnants of dunes in the upper shoreface due to a strong influence of longshore currents while planar laminated facies would be the result of swash processes in the foreshore additionally the presence of a well defined surf diastem the persistent low angle obliquity of palaeocurrents and the preservation of concave upward stratigraphic surfaces led to the interpretation of those deposits as representing the production of a bar trough configuration with longshore currents distributing large amounts of sediment along the shore this analysis allowed us to reconstruct the dominant processes for sediment transport and deposition within these barred nearshore settings and to identify different key architectural surfaces for the upper shoreface and foreshore deposits the architectural analysis of such surfaces led to define four different orders of hierarchy which respond to depositional and erosional processes operating at different scales the comparison between different resulting architectures of wave dominated barred shoreline offers the possibility to improve in the palaeoenvironmental reconstructions for ancient or recent successions the proposed model for bar trough clastic shoreline successions relates an absence of bar related deposits to major storms and shoreline erosional processes this conceptual model offers a new interpretation for explaining the mid scale evolution of bar trough settings and the relationship between the modern and ancient record

some physical drivers of changes in the winter storm tracks over the north atlantic and mediterranean during the holocene the winter climate of europe and the mediterranean is dominated by the weather systems of the mid latitude storm tracks the behaviour of the storm tracks is highly variable particularly in the eastern north atlantic and has a profound impact on the hydroclimate of the mediterranean region a deeper understanding of the storm tracks and the factors that drive them is therefore crucial for interpreting past changes in mediterranean climate and the civilizations it has supported over the last 12 000 years broadly the holocene period this paper presents a discussion of how changes in climate forcing e g orbital variations greenhouse gases ice sheet cover may have impacted on the basic ingredients controlling the mid latitude storm tracks over the north atlantic and the mediterranean on intermillennial time scales idealized simulations using the hadam3 atmospheric general circulation model gcm are used to explore the basic processes while a series of timeslice simulations from a similar atmospheric gcm coupled to a thermodynamic slab ocean hadsm3 are examined to identify the impact these drivers have on the storm track during the holocene the results suggest that the north atlantic storm track has moved northward and strengthened with time since the early to mid holocene in contrast the mediterranean storm track may have weakened over the same period it is however emphasized that much remains still to be understood about the evolution of the north atlantic and mediterranean storm tracks during the holocene period

sea level markers identified in ground penetrating radar data collected across a modern beach ridge system in a microtidal regime sea level rise has been related to global warming the modern system on the northern coast of anholt denmark may well be analogous to other beach ridge systems formed in microtidal regimes and our results should have impact on estimation of past sea level variation ground penetrating radar data collected across the modern 30 years old berm beach ridge and swale deposits resolve downlapping reflections interpreted to mark sea level at the time of deposition existing time series of sea level data constrain actual sea level variation nineteen readings of sea level markers made along our profile fluctuate within 0 42 and 0 57 m above present mean sea level consistent with 95 of the sea level data these fluctuations reflect tidal effects and meteorological conditions main data uncertainties are well known and the sea level markers may be identified with a high degree of confidence

time dependent nonlinear hadley circulation the time dependent hadley circulation is studied numerically in a nonlinear nearly inviscid axially symmetric primitive equation model with the heating varying periodically on an annual cycle the annual average of the hadley circulation strength in this model with time dependent heating is about a factor of 2 stronger than the steady state response to the annual mean heating and is closer to the observed strength in the real atmosphere this is caused by the fact that heating centered off equator tends to produce stronger meridional circulation in the winter hemisphere than in the case when the heating maximum is located at the equator as pointed out previously by lindzen and hou however unlike the steady state solutions there is no abrupt change as the heating center is moved off the equator the temperature response in this time dependent model is simple to understand in the tropical region where there is a variable but persistent hadley circulation the temperature is homogenized latitudinally in the highlatitude region where there is no meridional circulation in the absence of the eddies the temperature response goes through an annual cycle with a phase lag relative to the phase of the heating this response is as predicted by the simple time dependent temperature equation in the absence of meridional circulation

storm flood impacts along the shores of micro tidal inland seas a morphological and sedimentological study of the vesterlyng beach the belt sea denmark abstract the morphological and sedimentological impacts of an extreme storm event bodil in december 2013 were investigated at a mixed sand and gravel beach vesterlyng in a micro tidal environment along the belt sea denmark the storm response was characteristic for mixed sand and gravel beaches gravelly storm berms with sandy to gravelly washover fans were formed at the upper beach where swash processes dominated during extreme water levels in combination with overtopping and overwash in addition storm scarps and gravel flats were formed the elevation of the storm berm crest was identical to a summation of the still water level 1 60 m in the belt sea during the storm flood and the wave run up 0 75 m at the shore the crest of 2 35 m is therefore a precise measure of the storm flood level this storm flood was classified as a large scale extreme event in a holocene perspective it is suggested that storm berm beach ridge heights above contemporaneous sea level can be used as a proxy of past flood events along micro tidal shores

the global monsoon as seen through the divergent atmospheric circulation a comprehensive description is given of the global monsoon as seen through the large scale overturning in the atmosphere that changes with the seasons and it provides a basis for delimiting the monsoon regions of the world the analysis focuses on the mean annual cycle of the divergent winds and associated vertical motions as given by the monthly mean fields for 1979 93 reanalyses from the national centers for environmental prediction national center for atmospheric research ncep ncar and european centre for medium range weather forecasts ecmwf which are able to reproduce the dominant modes a complex empirical orthogonal function analysis of the divergent circulation brings out two dominant modes with essentially the same vertical structures in all months of the year the first mode which depicts the global monsoon has a simple vertical structure with a maximum in vertical motion at about 400 mb divergence in the upper troposphere that is strongest at 150 mb and decays to zero amplitude above 70 mb and convergence in the lower troposphere with a maximum at 925 mb ecmwf or 850 mb ncep however this mode has a rich three dimensional spatial structure that evolves with the seasons it accounts for 60 of the annual cycle variance of the divergent mass circulation and dominates the hadley circulation as well as three overturning transverse cells these include the pacific walker circulation an americas atlantic walker circulation both of which comprise rising motion in the west and sinking in the east and a transverse cell over asia the middle east north africa and the indian ocean that has rising motion in the east and sinking toward the west these exist year round but migrate and evolve considerably with the seasons and have about a third to half of the mass flux of the peak hadley cell the annual cycle of the two hadley cells reveals peak strength in early february and early august in both reanalyses a second monsoon mode which accounts for 20 of the variance features relatively shallow but vigorous overturning with the maximum vertical velocities near 800 mb outflow from 750 to 350 mb and inflow peaking at 925 mb it is especially strong over africa where the shallow mostly meridional overturning migrates back and forth across the equator with the seasons it influences the middle east has a signature over australia and is also an important component of the overturning in the tropical eastern pacific and atlantic and thus of the convergence zones in these regions the relationship of the global monsoon to the regional monsoons is described over six zonal sectors africa australia asia north america south america and the pacific and atlantic oceans only the two ocean areas do not undergo a seasonal reversal required for monsoons although they have direct overturning cells and they nevertheless participate in the global monsoon through the changes in large scale overturning the regional meridional cross sections highlight the importance of the shallow overturning cell in lower troposphere monsoon activity the steadiness of the overturning circulation is determined by comparing the signal of the seasonal mean vertical motions at 500 mb with the standard deviation of the transient daily variations locations where this signal exceeds 60 of the daily noise correspond closely with the regional centers of the monsoon

the basic ingredients of the north atlantic storm track part i land sea contrast and orography understanding and predicting changes in storm tracks over longer time scales is a challenging problem particularly in the north atlantic this is due in part to the complex range of forcings land sea contrast orography sea surface temperatures etc that combine to produce the structure of the storm track the impact of land sea contrast and midlatitude orography on the north atlantic storm track is investigated through a hierarchy of gcm simulations using idealized and semirealistic boundary conditions in a highresolution version of the hadley centre atmosphere model hadam3 this framework captures the largescale essence of features such as the north and south american continents eurasia and the rocky mountains enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies the physical processes by which the forcing mechanisms impact the large scale flow and the midlatitude storm tracks are discussed the characteristics of the north american continent are found to be very important in generating the structure of the north atlantic storm track in particular the southwest northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the rocky mountains leads to enhanced storm development along an axis close to that of the continent s eastern coastline the approximately triangular shape of north america also enables a cold pool of air to develop in the northeast intensifying the surface temperature contrast across the eastern coastline consistent with further enhancements of baroclinicity and storm growth along the same axis

the architecture of prograding sandy gravel beach ridges formed during the last holocene highstand southwestern british columbia canada this study was conducted to establish the sedimentary architecture of a beach ridge system that developed in response to rising and then stabilizing sea level in a macrotidal setting the beach ridges document a shift from transgressive to highstand depositional conditions a beach ridge complex is being deposited on the boundary bay tidal flats that flank the fraser river delta in southwestern british columbia the delta onlapped an offshore island during the holocene and partially incorporated it into its delta plain sand and gravel eroded from this island is the sediment source for the beach ridges four depositional geomorphic environments are identified beach ridges lagoon and swales washover fans and tidal flats the beach ridges prograded over the tidal flats of the fraser delta when sea level stabilized and the late holocene highstand was established the very earliest beach ridges were deposited about 5200 to 4800 years bp but most were formed after 2250 years bp with the establishment of the holocene highstand beach ridge progradation rates varied between 1 6 m a 1 to 0 48 m a 1 ground penetrating radar gpr was used to provide continuous two and three dimensional images of the facies in order to delineate the depositional architecture of the sandy gravel beach ridges we supplemented the customary use of well logs and cores for ground truthing gpr lines with cone penetration testing cpt which provided a detailed suite of logs invaluable for correlating radar reflections with subtle lithologic variations unidentifiable in core a synthesis of geomorphic environments lithologic logs and radar facies is used to construct a depositional model of the beach ridge complex

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

formation of aeolian dunes on anholt denmark since ad 1560 a record of deforestation and increased storminess abstract sand dunes on the island of anholt denmark in the middle of kattegat form a relatively barren temperate climate aeolian system locally termed the desert the dunes have developed on top of a raised beach ridge system under the influence of dominant winds from westerly directions they are relatively coarse grained with an average mean grain size of 480 m the last phase of aeolian activity and dune formation on anholt started after ad 1560 when the local pine forest was removed historical sources report intense sand mobilization in the 17th century and new optically stimulated luminescence osl dates indicate that dune formation continued until the end of the 19th century this period of sand drift and dune formation took place during the later part of the little ice age which is characterized by increased summer storminess in large parts of nw europe dune stabilization in the beginning of the 20th century probably records a temporary decrease in storminess ground penetrating radar mapping of the internal structures in two dunes in the western part of the desert a parabolic dune and a linear dune indicates the importance of north westerly storm winds during dune formation

the sedimentary architecture of a holocene barrier spit sylt german bight swash bar accretion and storm erosion abstract the southern german north sea coast was shaped by the last post glacial sea level rise that caused a significant retreat of the coastline approximately 5 ka bp the rate of sea level rise decreased providing space for the formation of the frisian islands which line the coast this study is focused on the island of sylt located at the german north sea coast close to the danish border here two sandy spit systems developed during the holocene combining ground penetrating radar studies and sedimentological investigations based on shallow cores new aspects on the sedimentary history of this holocene spit system have been revealed the data indicate that strong erosional events alternated with phases of progradation and growth the welding of swash bars is shown to be the predominant process during progradational phases of the spit system during these periods progradation was not restricted to linear growth along the spit axis but also included a seaward directed component major erosion surfaces which delimit progradational sediment packages are interpreted to reflect exceptionally severe storms the fossilization potential of this sedimentary record was controlled by a positive net long term sediment balance and the position of the ground water table which controlled eolian deflation only with a stable or rising sea level and associated ground water table position are sediments protected from deflation the proposed sedimentary model may serve as a template for interpretation of comparable settings in the geological record

sea level variation during the holocene deduced from the morphologic and stratigraphic evolution of morgan peninsula alabama u s a abstract recent gulf of mexico shoreline studies interpret middle to late holocene sea level as falling from a level above present elevation or stable at present elevation however the architecture of morgan peninsula alabama does not support this morgan peninsula is a beach ridge strandplain composed of two obliquely aligned holocene beach ridge sets ground penetrating radar profiles discriminate between parallel even to wavy reflectors of the eolian dune environment and the underlying seaward dipping complex sigmoidal oblique reflectors of the foreshore and upper shoreface environment the contact between foreshore and eolian facies in beach ridges can be used as a sea level indicator the average elevation of this contact in morgan peninsula rises throughout shoreline accretion which occurred throughout the last 5 4 ka suggesting that there was continual sea level rise during this time morgan peninsula is a useful modern analog to ancient shoreface shelf parasequences and demonstrates the significant internal complexities that can exist in these deposits erosional discontinuities imaged in the holocene foreshore upper shoreface environment are laterally continuous extend to elevations above mean sea level and correlate to beach ridges and the transition between beach ridge sets an increase in the wave regime or fluctuations in sediment supply appear to be likely mechanisms for forming erosional discontinuities below beach ridges the erosional surface separating beach ridge sets may have formed by increased storm activity and associated barrier breaching or a reconfiguration of the mobile bay tidal delta complex superimposed on a gradual rate of sea level rise this boundary is recognized by a change in beach ridge orientation at the surface and an increase in the aggradational component of shoreline accretion

changes in holocene relative sea level and coastal morphology a study of a raised beach ridge system on samso southwest scandinavia changes in relative sea level rsl during the holocene are reconstructed based on ground penetrating radar gpr data collected across a raised beach ridge system on the island of samso denmark the internal architecture of the beach ridge and swale deposits is divided into characteristic radar facies we identify downlap points interpreted to mark the transition from the beachface to the upper shoreface and thus sea level at the time of deposition this new data set shows that beach steps can be preserved and resolved in gpr reflection data this is important as downlap points identified at the base of the beach steps should be corrected for beach step height in order to be used as a marker of sea level identification of beach steps in combination with observed changes in dips of the interpreted beachface reflections can give information about changes in the morphodynamic conditions of beach ridge progradation through time the vertical levels of identified downlap points are combined with an age m

structure and formation mechanisms of the northern hemisphere summertime subtropical highs abstract three dimensional structure and dynamics of the climatological mean summertime subtropical highs over the north pacific and atlantic i e the azores high are investigated each of the observed surface highs is accompanied by a meridional vorticity dipole aloft exhibiting barotropic and baroclinic structures in its northern and southern portions respectively in a manner dynamically consistent with the observed midtropospheric subsidence each of the highs develops over the relatively cool eastern ocean where a pronounced near surface thermal contrast exists with a heated landmass to the east the authors demonstrate through numerical experiments that those highs can be reproduced in response to a local shallow cooling heating couplet associated with this thermal contrast although the upper level response is somewhat underestimated the model experiments suggest that the near surface thermal contrasts associated with those surface subtropical highs over the pacific and atlantic can act as s

the evolution of chabahar beach ridge system in se iran in response to holocene relative sea level changes abstract the chabahar strandplain chs stretches along the chabahar bay at a width of more than 5 km along the northern coast of the gulf of oman and se iran an area that has been subjected to tectonic uplift as a part of the makran accretionary prism the chs comprises of beach ridges inter ridge swales sand dunes tidal channels and fluvial deposits we present the first documentation of the spatial distribution and the internal architecture of the chs based on topographic surveys sediment percussive coring trenching and ground penetrating radar gpr transects radiocarbon dating on marine shells from foreshore deposits of 8 representative beach ridges yielded ages between 4800 and 270 cal years bp at respective distances of 4800 to 670 m from the present shoreline we interpret the boundary between the foreshore beach and the foredune deposits as indicator of past sea levels by analogy to present shore processes this boundary is readily recognizable in sediment profiles from cores and trenches as well as gpr reflectors based on the age model and depositional features we estimate relative sea level fall of up to 15 m over the past 4800 years considering that the eustatic sea level changes for this period are negligible for the makran coast this relative sea level fall is related to tectonic uplift across the coastal makran the elevation of palaeo shorelines with similar ages decrease from east to west of the chs which suggest that alongshore variations in uplift rates are likely related to different movements of coastal fault blocks

ground penetrating radar profiles of holocene raised beach deposits in the kujukuri strand plain pacific coast of eastern japan abstract ground penetrating radar gpr profiles of holocene beach deposits were documented from the kujukuri strand plain pacific coast of japan to examine a marker of past sea level recognized in these profiles the kujukuri strand plain has been uplifted over the last 6000 years with a total relative sea level fall of about 5 m suggested by seaward lowering of the lithologic boundary between the foreshore and upper shoreface facies a gpr survey was performed on a modern aeolian dune and beach ridges of the strand plain using a pulseekko100 system with 100 mhz antennae the profiles obtained contain five vertically stacked radar units r1 r5 with characteristic reflections ground truthing using sediment cores and the morphology of the modern beach suggest that these radar units correspond to aeolian dune r1 small scale swale r2 backshore and foreshore r3 upper shoreface r4 and lower shoreface r5 deposits in descending order the backshore and foreshore radar unit shows a sequence of continuous reflections dipping seaward at an angle consistent with the modern beach whereas the underlying upper shoreface radar unit represents complicated and less continuous reflections the boundary between these two units is a downlap surface of the foreshore reflections and is thought to have formed at about 1 m below the mean sea level at the time of deposition the lateral tracing of the boundary in radar profiles across the strand plain indicates a total fall in relative sea level of 5 m which is consistent with the drill core results radar profiles of the foreshore and upper shoreface deposits in the kujukuri strand plain thus provide a past sea level indicator that is available without drilling sediment cores

holocene evolution of the chan may coastal embayment central vietnam changing coastal dynamics associated with decreasing rates of progradation possibly forced by mid to late holocene sea level changes abstract southeast asian coastal environments are undergoing massive transformations with unprecedented population and infrastructure development these transformations are occurring on a backdrop of intense natural and anthropogenic environmental change which are increasing the risk to the burgeoning coastal population little is known about how central vietnamese coastal environments have changed naturally since the mid holocene sea level highstand and how recent anthropogenic change and sea level variation have affected the coastal system the chan may embayment in central vietnam allows us to examine how recent changes in both anthropogenic development and sea level change have affected the coastline the embayment preserves a series of prograding beach ridges and is subject to intense human pressures with the construction of a large economic and industrial park and expansion of tourist facilities using ground penetrating radar and quartz optical dating we identify a switch from 6000 years of prograding beach ridges to transgressive dunes within the past century resulting in a decreasing rate of beach ridge progradation possibly in the last 100 years the recent modes of sediment deposition through washovers and a transgressive dune indicates that coastal progradation has slowed and might have stopped

a beach ridge progradation complex reflecting periodical sea level and climate variability during the holocene gulf of almeria western mediterranean detailed mapping based on aerial photographs at various scales analysis of morpho sedimentary units and radiocarbon dating of the prograding beach ridge complex of campo de dalias almeria allow the differentiation of six prograding units these are called h1 7400 6000 cal bp h2 5400 4200 cal bp h3 4200 3000 cal bp h4 2700 1900 cal bp h5 1900 1100 cal bp and h6 500 cal bp present h units are deposited during periods of high relative sea level and increased sediment input to the coast they are bounded by large swales or erosional surfaces associated with lower sea levels and reduced input of sediment to the coast these correspond to short periods of increased aridity inside the general arid trend recorded in the western mediterranean since 5 4 ka changes in the flux of atlantic superficial waters into the mediterranean sea and relative strength of the w sw winds account for the recorded oscillations of relative sea level we deduce a decadal periodicity for the deposition of a beach ridge and the adjacent swale and suggest that it is related to fluctuations of the north atlantic oscillation nao index and to variations of solar activity the duration of h units shows a quasi millennial periodicity punctuated by short hundred years episodes of reduced progradation or erosion representing events of increased aridity likely to be related to bond s holocene cold events

indications of an extreme event deposits along the west coast of india evidences from gpr investigations the ground penetrating radar gpr was used to trace the subsurface details in the palshet coastal zone maharashtra as it exhibits an interesting array of geomorphological features furthermore our main goal was to identify and locate features that might have formed during a reported extreme event and its effects on the flow of the nearby sundri river two profiles 8 and 4 m depth were collected across the beach and along the backshore respectively while the 8 m depth profile west to east across the beach indicates a series of coastline regression in this area the 4 m depth profile along the coastline north to south in the backshore zone reveals two significant incidents viz 1 stages of development of the paleo channels that indicate the migration of the sundri river towards south and 2 huge sediment deposits up to 2 5 m thick in the backshore area the erosional relict surface 2 5 m depth was traced along with various spells of sediments that perhaps occurred due to an extreme event sand samples were collected from two trial pits along the gpr profiles to understand the sedimentology and mineralogy in the backshore area these data together with beach profiles and geomorphological maps suggest that the sands were deposited by an extreme event perhaps during the 1854 cyclonic storm the sands were trapped in suitable geomorphological sites along the palshet coast and these sand deposits of about 2 5 m thickness forced the river sundri to shift its course towards the south this new revelation facilitates a further study that could focus on the nearby coastal areas to document such extreme event deposits and their influence on the geomorphic set up

on the role of planetary scale waves in the abrupt seasonal transition of the northern hemisphere general circulation the role of planetary scale waves in the abrupt seasonal transition of the northern hemisphere nh general circulation is studied in reanalysis data the winter to summer transition involves the growth of planetary scale wave latent heat and momentum transports in the region of monsoons and anticyclones that dominate over the zonal mean transport beginning in midspring the wave dominated regime coincides with an abrupt northward expansion of the cross equatorial circulation and reversal of the trade winds in the upper troposphere the transition coincides with the growth of cross equatorial planetary scale wave momentum transport and a poleward shift of subplanetary scale wave transport and jet stream the dynamics of the seasonal transition are captured by idealized aquaplanet model simulations with a prescribed subtropical planetary scale wave sea surface temperature sst perturbation the sst perturbation generates subtropical planetary scale wave streamfunction variance and transport in the lower and uppertroposphereconsistentwithquasigeostrophictheory beyondathresholdsst atransitionofthezonalmean circulation occurs which coincides with a localized reversal of absolute vorticity in the nh tropical upper troposphere the transition is abrupt in the lower troposphere because of the quadratic dependence of the wave transport on the sst perturbation and involves seasonal time scale feedbacks between the wave and zonal meanflow in theupper troposphere including cross equatorial wave propagation thezonal mean vertical and meridional flows associated with the circulation response are in balance with the planetary scale wave momentumand latentheat meridionalflux divergences the resultshighlightthe leading order roleofmonsoon anticyclone transport in the seasonal transition including its impact on the meridional extent of the hadley and ferrel cells they can also be used to explain why the transition is less abrupt in the southern hemisphere

storm response of a mixed sand gravel beach ridge plain under falling relative sea levels a stratigraphic investigation using ground penetrating radar beach ridge stratigraphy can provide an important record of both sustained coastal progradation and responses to events such as extreme storms as well as evidence of earthquake induced sediment pulses this study is a stratigraphic investigation of the late holocene mixed sand gravel msg beach ridge plain on the canterbury coast new zealand the subsurface was imaged along a 370 m shore normal transect using 100 and 200 mhz ground penetrating radar gpr antennae and cored to sample sediment textures results show that seaward of a back barrier lagoon the pegasus bay beach ridge plain prograded almost uniformly under conditions of relatively stable sea level nearshore sediment supply appears to have created a sustained sediment surplus perhaps as a result of post seismic sediment pulses resulting in a flat morphologically featureless beach ridge plain evidence of a high magnitude storm provides an exception with an estimated event return period in excess of 100 years evidence from the gpr sequence combined with modern process observations from msg beaches indicates that a palaeo storm initially created a washover fan into the back barrier lagoon with a large amount of sediment simultaneously moved off the beach face into the nearshore this erosion event resulted in a topographic depression still evident today in the subsequent recovery period sediment was reworked by swash onto the beach as a sequence of berm deposit laminations creating an elevated beach ridge that also has a modern day topographic signature as sediment supply returned to normal and under conditions of falling sea level a beach ridge progradation sequence accumulated seaward of the storm feature out to the modern day beach as a large flat uniform progradation plain this study highlights the importance of extreme storm events and earthquake pulses on msg coastlines in triggering high volume beach ridge formation during the subsequent recovery period

investigation of large scale washover of a small barrier system on the southeast australian coast using ground penetrating radar abstract prehistoric depositional signatures for large scale washover involving marine inundation events such as storms and tsunami have been the subject of considerable research over the last 15 years much of this research has focused on the identification of sandsheets in back barrier environments as depositional records for extreme washover events all these deposits must have a sediment source and by their nature the most likely source of sediment for washover into back barrier environments is the barrier itself this study identifies an erosional signature for large scale washover from a small coastal barrier on the southeast australian coast a distinct lens of marine sand up to 90 cm thick confined vertically by peat is found in the upper fill of a closed freshwater back barrier lagoon sequence this sand lens is attributed to a large scale washover event during the last 800 years and was possibly deposited by a tsunami the hypothesis for this study was that any event that breached the dune system must have caused considerable geomorphic change to the dunes and hence may have left an erosional signature ground penetrating radar transects of the system show an erosional contact between a series of truncated pre event dunes and several small overlying post event dunes this study outlines a relatively simple non invasive method for the identification of an erosional signature for prehistoric large scale washovers caused by storm surge exceptionally large waves or tsunami

radar facies of paraglacial barrier systems coastal new england usa analysis of a large data base of ground penetrating radar gpr profiles from both natural and developed paraglacial barriers along the coast of new england has allowed identification of eight reflection configurations that characterize this type of mid to high latitude coastal environment bedrock anchor points yield primarily hyperbolic configurations whereas glacial anchor points and sediment source areas are characterized by chaotic parallel and tangential oblique configurations beaches and dunes produce predominantly sigmoidal oblique hummocky reflection free and bounding surface configurations back barrier sediments may yield basin fill configurations but generally include abundant signal attenuating units the gpr data calibrated with information from cores were collected across swash aligned and drift aligned barriers in a variety of wave and tidal energy settings application of a 120 mhz antenna as used in this study enables portrayal of a range of sedimentary units from individual bedforms on single records to entire barrier elements using large numbers of intersecting gpr sections at maximum vertical resolutions that vary between 0 2 m and 0 7 m the most important drawback of gpr in the coastal environment is attenuation of the electromagnetic em signal by layers of salt marsh peat or by brackish or salty groundwater primarily along barrier edges this disadvantage is offset by many benefits data can be collected at rates of several km per day making gpr an excellent reconnaissance tool a core that is used in the calibration of gpr data can be matched with great accuracy to its position on the complementary gpr record allowing detailed correlation between lithostratigraphy and reflection configuration

quaternary coastal plains as reservoir analogs wave dominated sand body heterogeneity from outcrop and ground penetrating radar central santos basin southeast brazil abstract sub seismic sand body characterization depends largely on understanding the heterogeneities observed in outcrops of equivalent depositional settings to subsurface reservoirs reservoir analogs outcrop information however rarely covers the whole depositional system ground penetrating radar gpr on the other hand is a powerful tool for the high resolution visualization of sand rich deposits in the shallow subsurface allowing for the description of their internal architecture relationships with depositional systems and its larger scale stratigraphic evolution the internal character of radar patterns can be interpreted with respect to facies seen in exposures leading to the prediction of heterogeneities below radar resolution in this paper we use gpr and outcrops to describe the heterogeneity of quaternary coastal plain deposits from central santos basin parana state southern brazil where pleistocene and holocene wave dominated regressive barriers and transgressive lagoons and estuaries were formed under the influence of quaternary sea level and climatic changes sedimentary facies reveal the predominance of sand deposited under the influence of tidal processes fair weather and storm wave processes radarfacies indicate a tendency of progradation of beach face reflectors over subtidal radarfacies within two regressive successions separated by a regional unconformity interpretation of gpr resulted in the definition of 13 radarfacies arranged in three associations reflecting major depositional systems 1 strandplains formed by prograding beach dune ridge sets over subtidal deposits 2 spit inlets with progradation of beach faces over subtidal deposits and longshore accretion of spits and 3 paleolagoons paleoestuaries sedimentary facies indicate that strandplains and spit inlets are predominantly sandy while a muddy composition is expected in paleolagoons paleoestuaries the distribution and evolution of these systems were controlled by base level oscillations and or sediment supply that resulted in the formation of two regressive barriers separated by a wave ravinement surface configuring two parasequences with a wide variety of inter and intra sand body heterogeneities this arrangement imprints a relatively high degree of compartmentalization within deposits that are traditionally considered continuous and homogeneous therefore the quaternary coastal plain of parana can be used as an analog for compartmentalized coastal reservoirs

the termination of the last major phase of aeolian sand movement coastal dunefields denmark optically stimulated luminescence osl dating of sand samples from stabilized or inactive coastal dunes in denmark provides information on the age of the termination phase of the last major aeolian activity period a total of 26 sand samples were taken from four different coastal dunefields around the north sea skagerrak and kattegat coasts of denmark the osl dates indicate that the last major phase of aeolian activity terminated between ad 1860 and 1905 most of the dunes examined in this study were active around 1820 during a period documented to have been very stormy a dune management scheme started around 1792 and this no doubt was a major cause of dunefield stabilization but an overall decline of storminess particularly spring and summer storminess around the end of the 19th century must also have contributed to the increasing inactivity of coastal dunes the new osl dates on aeolian sand movement agree well with historical data and data from topographic maps on dune movement this agreement supports the observation from earlier work that osl dating of recent aeolian sand movement is accurate over the last few decades to centuries copyright 2005 john wiley sons ltd

lower palaeozoic unconformities in an intracratonic platform setting glacial erosion versus tectonics in the eastern murzuq basin southern libya the stratigraphic record of the eastern murzuq basin has been importantly influenced by deformation resulting in angular and or deeply erosional unconformities though the overall context is intracratonic major transgressive events and the ordovician glaciation are nevertheless documented allowing the delineation of tectonic eustasy or climate driven unconformities lower palaeozoic key events and related unconformities that characterize the north gondwana platform have therefore a signature in the eastern murzuq basin the basement cover unconformity also known as the infra tassilian surface truncates all the deformed and metamorphosed lower cambrian and older rocks above is a middle cambrian to lower ordovician megasequence murizidie and hasawnah fms which is in turn truncated by an intra ordovician angular unconformity this megasequence is unconformably overlain by a middle ordovician hawaz fm to silurian tanzzuft and akakus fms megasequence which includes the upper ordovician glaciogenic unit mamuniyat fm bounded at the base by a polygenic glacial erosion surface showing corrugated glacial lineations tillites and glaciotectonic structures the middle ordovician to silurian megasequence is finally truncated by a base devonian angular unconformity overlain by fluvial sandstones regarding the possibility that those fluvial deposits may be as younger as late devonian in the eastern murzuq basin based on palaeoflora the so called caledonian unconformity might be here a much younger mid eifelian surface and the occurrence of the lower devonian tadrart fm is questioned the upper ordovician glacial erosion surface which is sometimes referred to as the taconic unconformity usually truncates middle ordovician strata in the murzuq basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra ordovician deformation event in the murizidie southeastern murzuq basin the infra tassilian surface the intra ordovician unconformity and the upper ordovician glacial erosion surface amalgamate together here an estimate of the glacial erosion depth cannot be derived from the stratigraphic hiatus beneath the glacial incision the main part of which relate to the intra ordovician tectonic event the upper ordovician climate related glacial erosion surface is not a valid unconformity for a sequence hierarchy framework of the lower palaeozoic although it presents most of the physical attributes of tectonic driven unconformities

morphology and facies architecture of a falling sea level strandplain umiujaq hudson bay canada coastal strandplain deposits near umiujaq eastern hudson bay canada were formed under falling relative sea level conditions resulting from postglacial isostatic uplift ground probing radar profiles across the strandplain reveal a lower progradational unit lpu discordantly overlain by an upper progradational unit upu which were correlated with stratigraphic sections exposed in incised valley walls the discordance is a wave erosion surface wes that separates fine shoreface sands of the lpu from coarse sand and gravel of the upu major basal downlap surfaces can be traced updip into marine terraces and define downstepping wedges the downstepping is interpreted as representing autocyclic morphological reconfiguration rather than a response to changes in the rate of sea level fall the internal architecture is strongly dependent on the accommodation and thus on antecedent topography a conceptual model for strandplain deposition under falling sea level incorporates a bipartite shallowing upward sandy succession when sufficient accommodation is available where accommodation space is limited a sharp based bar and beach sandbody directly overlies muddy deeper water deposits and the wes resembles a regressive surface of erosion

reconstructing holocene shore displacement and stone age palaeogeography from a foredune sequence on ruhnu island gulf of riga baltic sea abstract holocene shore displacement and the palaeogeography of late mesolithic and late neolithic settlements on ruhnu island gulf of riga were reconstructed using foredune sequence luminescence dating sedimentological data supported by ground penetrating radar analysis and gis based landscape modelling the foredune ridges consist of very well to well sorted fine to medium grained aeolian sand and are underlain by seaward dipping foreshore sediments the studied sequence of 38 ridges was formed between 6 91 0 58 ka and 2 54 0 19 ka ago and represents a period of falling relative sea level foredune plain progradation with average rates of 0 3 0 6 m per year was controlled by isostatic land uplift which caused a continuous withdrawal of shorelines to lower elevations the dated foredune succession was used to reconstruct the coastal palaeogeography of the island palaeogeographical reconstructions show that during two phases of late mesolithic habitation at ca 7 2 cal ka bp and 6 2 cal ka bp seal hunters settled the coastal zone of ruhnu island based on tool material and pottery type they could have originated from saaremaa island which according to palaeoreconstruction of the gulf of riga was located approximately 70 km northwest of ruhnu island during the late mesolithic later signs of human occupation radiocarbon dated to ca 4 7 cal ka bp were from the centre of the island hundreds of metres away from the shore at about 8 m above its contemporary sea level this late neolithic habitation shows a clearly different pattern than earlier coastal settlement and suggests a shift in subsistence strategy towards agriculture and animal husbandry

impact of relative sea level changes since the last deglaciation on the formation of a composite paraglacial barrier abstract comprehensive onshore offshore surficial and sub surface mapping of a composite barrier combination of prograded aggraded and or transgressive segments have provided a better understanding of the i mechanisms responsible for the formation and development of coastal barrier systems ii relationships and interactions among individual parts of those systems and ii the overall stratigraphic framework of subaerial and subaqueous segments of the barriers here we investigate these facets of barrier evolution through integration of stratigraphic data from subaqueous high resolution seismic and subaerial ground penetrating radar sedimentology terrestrial cores and seafloor surface samples and merged topographic and bathymetric mapping of the miquelon langlade barrier northwest atlantic ocean south of newfoundland this barrier system has two open coasts and evolved in a paraglacial setting influenced by the reworking of glaciogenic sediment glacial moraines in a regime of complex sea level changes the barrier stratigraphic sequence is placed within the context of a shifting period from shoreline transgression to one of regression the resulting sedimentary units reflect the isolated position of the saint pierre and miquelon archipelago distal from continental influence seismic profiles reveal the position of the lowstand shoreline located 20 25 m below modern sea level further refining the existing lowstand model of southern newfoundland continuous onshore offshore subsurface geophysical mapping of the barrier allows for the identification of the relative positioning of distinct sedimentary units interpreted as subaerial barrier beaches dunes spit shoals and shoreface deposits and allows for estimation of the total barrier sediment volume 235 106 m3 and its relative subaqueous 90 and subaerial 10 components moreover it reveals the three distinct morphological units comprising the holocene barrier i central regressive swash aligned beach ridge plains developed atop both thin westward prograding and thick eastward prograding shoreface deposits ii drift aligned elongating spits located in the northwest and northeast of the island and iii a transgressive barrier located adjacent to the northwest spit pinned on its landward side to parabolic sand dunes and currently experiencing erosion and limited overwash finally this study places evolution of this system in the framework of paraglacial barrier evolutionary typology

the south indian convergence zone and interannual rainfall variability over southern africa abstract the south indian convergence zone sicz is identified in this paper as a region of enhanced precipitation extending off the southeast coast of southern africa during austral summer unlike the south pacific convergence zone the sicz is a land based convergence zone lbcz with position and intensity at least partially determined by surface conditions over southern africa an idealized gcm simulation is used to explore the basic dynamics of lbczs in the tropics and subtropics output from a realistic gcm simulation and the national centers for environmental prediction national center for atmospheric research 40 year reanalysis are analyzed to apply this basic dynamical framework to the case of the sicz in contrast to the intertropical convergence zone where column moisture convergence is primarily due to meridional wind convergence in the moist environment precipitation within the sicz and the lbczs in general is also supported by zonal wind convergence moisture convergence by transient eddy

retroarc basin reorganization and aridification during paleogene uplift of the southern central andes u s national science foundation ear 1049605 robert r shrock foundation at indiana university nsf ear award 1338583 project pdts unsj e985

the impact of the late holocene coastal changes on the rise and decay of the ancient city of histria southern danube delta histria istros is one of the earliest milesian colonies founded on the black sea coast during the archaic period 7th c bc its remains are located within what is today the razelm sinoe lagoon system which forms the southern part of the danube delta during its 13 centuries of existence histria experienced an environment favourable for a prosperous economy e g fishery farming grazing pottery marine trades as indicated by numerous archeological finds from both in situ and elsewhere in the black sea and mediterranean sea basins moreover it benefited from a strategic position on an open coast which was easy to defend important environmental changes occurred both during and after the existence of the ancient city and the most significant are related to major shoreline displacement this study reports late holocene coastal landscape changes from the open coast stage to the present day lagoon system based on numerical age determination of the paleoshorelines stratigraphic records by cores in lagoons and beach ridges and topographic surveys a new chronological framework is established which reports younger ages than previously suggested for the coastal morphosedimentary units of the histria region further the findings shed new light upon the evolution of the southern part of the danube delta the results point to the development of an ancient deltaic lobe dunav lobe 2000 1300 bp associated with the southernmost danube distributary which was situated 10 20 km north of the settlement the lobe was subsequently reworked by waves providing sediments which were accumulated downdrift southward as a continuous beach ridge plain saele chituc in front of the city leading to its isolation from the sea the abandonment of histria 7th c ad coincides with the decoupling of the city from the open coast as a consequence of the shoreline progradation the new beach ridge plain saele chituc is affected by intense neotectonic movements which led to the recent drowning of its central part and the formation of sinoe lagoon the same processes affected the downdrift part of the dunav lobe and histria and nuntasi lakes the new sea level curve obtained for the histria region shows relative stability within the last four millennia with oscillations within 0 to 2 m of the current level this contradicts the concept of a marine regression phanagorian which is suggested to have occurred during the 1st millennium bc however a few areas containing archeological remains are currently below sea level owing to local neotectonics

aeolian beach ridges and their significance for climate and sea level concept and insight from the levant coast east mediterranean abstract relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results most studies link the aeolian coastal deposits to regressive phases some to high sea level stands and a few to intermediate relative sea level positions we interpret the apparent contradictions as indicating the lack of an over arching concept and the inconsistent usage of sea level related terms in this paper we present an integrated morpho sedimentological concept for a microtidal mid latitudinal coast and review existing data from the levant east mediterranean coast to evaluate the concept and to eliminate nomenclatural confusion a coastal depositional environment in a semi arid environment consists of shallow marine aeolian and alluvial facies which together form an aeolian beach ridge complex as a package of strata which respond simultaneously to sea level change a transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit under regression the complex represents the falling stage and the associated downdip surface marks the lowstand on the levant coast we find chronologically well constrained offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between 200 ka and 10 ka the complexes represent the falling stage systems tract fsst of a short lived 5th order depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge three of these fssts and their up dip and down dip super bounding surface together form the 4th order 100 ka sequence of the last interglacial glacial cycle the absence of transgressive highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex the falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold on the levant coast sand delivery to the backshore continued during relative sea level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues the significance of the dune soil succession for climate is limited because the dunes are governed by relative sea level change the vegetation response to changes in precipitation is non linear and the dune dynamics are characterised by low resilience and hysteresis

beach ridges definitions and significance abstract beach ridges frequent components of quaternary coastal plains and other coastal landforms have been cited as indicators of the positions of ancient seashores and associated sea levels numerous authors utilized the term beach ridge for active and relict usually wave built supratidal and or intertidal forms wind built ridges have been only occasionally included in the definition the term was applied also to submerged landward shifting eventually stranded bars a consistent redefinition of the term is highly desirable beach ridges should include all relict strandplain ridges whether dominated by wave swash built or by eolian lithosomes all active ridge like shore features regardless of dimensions morphology and origin are excluded because of the resistance of coarse clastic ridges to wave and wind erosion swash built gravel or coarse shell storm ridges may build several meters above the level of high tide swash built high berms even on pure sandy beaches exceed the highest tides during episodes of wind induced record water levels frequently but not always burying underlying low relief berm ridges of berm lithosomes sequences of relatively steep multiple foredunes are commonly named beach ridge plains the narrow subparallel relict foredunes that form these strandplains presently are designated as eolian beach ridges beach ridges thus are defined as relict semiparallel multiple wave and wind built landforms that originated in the inter and supratidal zones until separated from the shoreline by progradation sandy pebbly or shell enriched backshore berm ridges behind an active foreshore should not be considered beach ridges strandplain progradation is either continuous or with the inclusion of subtidal cat s eye ponds discontinuous contrary to claims transgressive cheniers do not represent true cheniers alone within their overall progradational context cheniers a special category of beach ridges bracketed by subtidal intertidal mudflats may be transgressive or regressive in character landward driven transgressive ridges should be designated beach ridges only after they are stabilized on intertidal flats when recognizable between clearly identifiable intertidal and overlying eolian intervals the horizontal interface between these lithosomes in beach ridges may help the reconstruction of ancient tide lake levels diagnostic sedimentary textures structures and fossils however often may be unavailable in the deposits along with various types of elevated terraces composed of raised marine deposits and certain coastal landforms of erosional origin that occur worldwide beach ridges of clearly proven wave built origin may also serve as indicators of ancient higher than present sea levels

geomorphology and dynamics of a traveling cuspate foreland authie estuary france abstract cuspate forelands or salients occur all over the world in lakes estuaries and on ocean shores yet there have been few studies conducted on traveling cuspate forelands or salients that is forelands that migrate or travel alongshore this paper presents a study of a traveling foreland in the authie estuary france termed the bec du perroquet historical shoreline changes may be traced from the 1200 s ad and the region has experienced both marked intertidal subtidal accretion extending from the south and massive erosion in the north since this period an analysis of aerial photographs from 1947 until the present shows that the original bec foreland was established at the mouth of the authie estuary but gradually disappeared by the 1960 s and a new foreland developed in the middle of the northern central portion of the bay this foreland was composed of a suite of foredune ridges which have been successively eroded on the northern margin and initiated on the southern margin as the foreland traveled or migrated southwards as the foreland traveled south from 1947 to 2009 the northern part of the bay retreated more than 350 m while mid bay the coastline retreated 215 m as the foreland evolves and migrates incipient foredunes can develop rapidly e g 18 ridges formed in an 11 week period while at other times the ridges form slowly and may be eroded and disappear two or more foredune ridges may blend into a single ridge over time depending on the initial degree of vegetation cover on the ridge and swale set aeolian processes in dune swales are much more important in this system than in typical prograding foredune plain systems due to the sometimes marked lack of vegetation colonization in the swales following foredune ridge development and aeolian deflation of the swales along with blowout development is important particularly when they become open conduits to the beach as erosion of the nw foreland proceeds the ages of each of the surviving ridges on the foreland in 2009 have been determined and the evolutionary path of the ridges ascertained formerly intact relatively stable continuous ridges evolve to erosional knobs turrets and nebkha over time foredune ridges and swales can be extremely arcuate to semi circular in form where the foreland and especially the spit extension are exposed to a wide range of wind directions and where the shoreline trends through an arc of at least 270 this study illustrates a remarkable cycling of the formation destruction and reformation travel of a cuspate foreland over a 50 year period

internal architecture of a raised beach ridge system anholt denmark resolved by ground penetrating radar investigations abstract the internal architecture of raised beach ridge and associated swale deposits on anholt records an ancient sea level the holocene beach ridges form part of a progradational beach ridge plain which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years the ridges are covered by pebbles and cobbles and commonly show evidence of deflation material presumably removed from the beach ridges and adjacent swales form the present dune forms on anholt ground penetrating radar gpr reflection lines have been collected with 250 mhz shielded antennae across the fossil ridge and swale structures the signals penetrate the subsurface to a maximum depth of 10 m below the fossil features the gpr data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0 1 m gpr mapping indicates that the holocene beach ridges are composed of seaward dipping beachface deposits as well as minor amounts of inland dipping deposits of wash over origin the beachface deposits downlap on underlying shoreface deposits and we use these surfaces as markers of a relative palaeo sea level the new data indicate that the highest relative sea level at about 8 5 m was reached 6500 years ago 700 years later the relative sea level had dropped 0 7 m indicating a change in the relative sea level around 1 mm year this fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels

morphological records of storm floods exemplified by the impact of the 1872 baltic storm on a sandy spit system in south eastern denmark beach ridge systems are important geo archives providing evidence for past wave climate including catastrophic storm flood events this study investigates the morphological impacts of the 1872 baltic storm flood on a beach ridge system sandy spit in south eastern denmark and evaluates the frequency of extreme storm flood events in the area over a longer time perspective this paper combines field studies of morphology and sedimentary deposits studies of historical maps digital terrain model ground penetrating radar profiles and luminescence dating sea water reached 2 8 m above mean sea level amsl during peak inundation and based on studies of the morphological impacts of the 1872 storm flood the event can be divided into four phases phase 1 increasing mean water levels and wave activity at the beach brought sediments from the beach intertidal bars and normal berm higher up in the profile and led to the formation of a storm berm phase 2 water levels further increased and sediment in the upper part of the profile continued to build up the storm berm phase 3 water levels now reached the top of the dune ridge and were well above the storm berm level sea water was breaching the dune ridge at several sites and wash over fans were generated until a level where the mean water level had dropped too much phase 4 the non vegetated wash over fans functioned as pathways for aeolian sand transport and relatively high dunes were formed in particular along the margins of the fan where aeolian sand was trapped by existing vegetation the studied beach ridge system records about 4500 years of accumulation the storm flood sediments described are unique suggesting that the 1872 baltic storm flood event was an extreme event thus studies of beach ridge systems form a new source for understanding storm surge risk copyright 2013 john wiley sons ltd

the structure and development of foredunes on a locally prograding coast insights from ground penetrating radar surveys norfolk uk the internal structure of coastal foredunes from three sites along the north norfolk coast has been investigated using ground penetrating radar gpr which provides a unique insight into the internal structure of these dunes that cannot be achieved by any other non destructive or geophysical technique combining geomorphological and geophysical investigations into the structure and morphology of these coastal foredunes has enabled a more accurate determination of their development and evolution the radar profiles show the internal structures which include foreslope accretion trough cut and fill roll over and beach deposits foredune ridges contain large sets of low angle cross stratification from dune foreslope accretion with trough shaped structures from cut and fill on the crest and rearslope foreslope accretion indicates sand supply from the beach to the foreslope while troughs on the dune crest and rearslope are attributed to reworking by offshore winds bounding surfaces between dunes are clearly resolved and reveal the relative chronology of dune emplacement radar sequence boundaries within dunes have been traced below the water table passing into beach erosion surfaces these are believed to result from storm activity which erodes the upper beach and dunes in one example at brancaster a dune scarp and erosion surface may be correlated with erosion in the 1950s possibly the 1953 storm results suggest that dune ridge development is intimately linked to changes in the shoreline with dune development associated with coastal progradation while dunes are eroded during storms and where beaches are eroding a stable coast provides more time for dune development resulting in higher foredune ridges a model for coastal dune evolution is presented which illustrates stages of dune development in response to beach evolution and sand supply in contrast to many other coastal dune fields where the prevailing wind is onshore on the north norfolk coast the prevailing wind is directed along the coast and offshore which reduces the landward migration of sand dunes

development of spit lagoon complexes in response to little ice age rapid sea level changes in the central guilan coast south caspian sea iran the central guilan coast along the iranian caspian coastline is characterized by sandy beaches and the development of spit lagoon complexes which are prone to preserve past sea level fluctuations the morphology of three spit lagoon complexes along the central guilan coast was studied using ground penetrating radar gpr and sediment sequences to understand the effects of past sea level changes on spit lagoon development the results showed the prominent role of coastal setting in conditioning the development of spit lagoon formation in response to sea level change when the caspian sea experienced a highstand in the little ice age the coast of central guilan recorded fluctuations in sedimentation which are reflected for example by river avulsion and beach ridge formation depending on physical setting in the western half of the central guilan eastward longshore currents and strong wave action on a w e coastline coupled with sea level changes shaped the anzali spit lagoon complex while in the eastern part of the studied area river avulsion and changing the coastline orientation are responsible for development of the amirkola and kiashahr spit lagoon complexes under the same sea level fluctuations although sea level change has a major role in spit lagoon development an increase in the frequency of storms changes in sediment supply due to more precipitation and river avulsion are other players in spit lagoon development in the central guilan during the little ice age and more recent times

ground penetrating radar 2 d and 3 d subsurface imaging of a coastal barrier spit long beach wa usa abstract the ability to effectively interpret and reconstruct geomorphic environments has been significantly aided by the subsurface imaging capabilities of ground penetrating radar gpr the gpr method which is based on the propagation and reflection of pulsed high frequency electromagnetic energy provides high resolution cm to m scale and shallow subsurface 0 60 m near continuous profiles of many coarser grained deposits sediments of low electrical conductivity this paper presents 2 d and 3 d gpr results from an experiment on a regressive modern barrier spit at willapa bay wa usa the medium grained sand spit is 38 km long up to 2 3 5 km wide and is influenced by a 3 7 m tidal range spring as well as high energy longshore transport and high wave energy depositional processes the spit has a freshwater aquifer recharged by rainfall the gpr acquisition system used for the test was a portable digital pulseekko system with antennae frequency ranging from 25 to 200 mhz and transmitter voltages ranging from 400 to 1000 v step sizes and antennae separation varied depending on the test requirements in addition 100 mhz antennae were used for conducting antennae orientation tests and collecting a detailed grid of data 50 50 m sampled every meter the 2 d digital profiles were processed and plotted using pulseekko software the 3 d datasets after initial processing were entered into a landmark workstation that allowed for unique 3 d perspectives of the subsurface to provide depth near surface velocity measurements were calculated from common midpoint cmp surveys results from the present study demonstrate higher resolution from the 200 mhz antennae for the top 5 6 m whereas the 25 and 50 mhz antennae show deeper penetration to 10 m for the study site 100 mhz antennae provided acceptable resolution continuity of reflections and penetration the dip profiles show a shingle like accretionary depositional pattern whereas strike profiles show a horizontal and subhorizontal nearly continuous reflection pattern results from the gpr experiment reveal upper shoreface reflections with dip towards the ocean at about 1 2 the loss of signal from below a depth of 6 8 m indicates a lithofacies change because of the storm wave base the parallel broadside and perpendicular broadside antennae orientation tests show detailed stratigraphy continuity and depth of penetration the cross polarization test exhibits reduced continuity of reflections and less depth of penetration but dipping reflections are apparent the grid pattern data provided a detailed view of 3 d geometry of individual reflections high quality data were obtained processed and directly exported into a landmark workstation for interpretation the resulting interpretations of the upper shoreface beds from the test cube 50 50 m total 2600 traces are shown as vertical sections slices horizontal sections time slices contour maps 3 d representations of individual beds and an isopach map the 3 d depositional framework allows a more detailed interpretation than widely spaced 2 d profiles

internal structure of mixed sand and gravel beach deposits revealed using ground penetrating radar mixed sand and gravel beaches are a distinctive type of coarse clastic beach ground penetrating radar gpr and photographic records of previous excavations are used to investigate the stratigraphy and internal sedimentary structure of mixed beach deposits at aldeburgh in suffolk south east england the principles of radar stratigraphy are used to describe and interpret migrated radar reflection profiles obtained from the study site the application of radar stratigraphy allows the delineation of both bounding surfaces radar surfaces and the intervening beds or bed sets radar facies the deposits of the main backshore berm ridge consist of seaward dipping bounding surfaces that are gently onlapped by seaward dipping bed sets good correspondence is observed between a sequence of beach profiles which record development of the berm ridge on the backshore and the berm ridge s internal structure the beach profile data also indicate that backshore berm ridges at aldeburgh owe their origin to discrete depositional episodes related to storm wave activity beach ridge plain deposits at the study site consist of a complex progradational sequence of foreshore berm ridge overtop and overwash deposits relict berm ridge deposits separated by seaward dipping bounding surfaces form the main depositional element beneath the beach ridge plain however the beach ridges themselves are formed predominantly of vertically stacked overtop overwash units which lie above the berm ridge deposits consequently beach ridge development in this progradational mixed beach setting must have occurred when conditions favoured overtopping and overwashing of the upper beachface interannual to decadal variations in wave climate antecedent beach morphology shoreline progradation rate and sea level are identified as the likely controlling factors in the development of such suitable conditions

a climatology of the northern hemisphere winter anticyclones 1 a climatology of the northern hemisphere winter anticyclonic activity is presented based on the european centre for medium range weather forecasts reanalysis data set for the 1957 2002 period era 40 and a system centered method of tracking diagnostics the method tracks the anticyclonic systems and monitors their evolution along their paths thus allowing documentation of aspects that have been previously overlooked due to the common perception of anticyclones as semi stationary relatively uniform slowly evolving structures the anticyclonic signal is examined in a wide range of meteorological fields and at multiple levels over the continental masses over the subtropical ocean basins and over the sectors where blocking highs tend to develop structural features thermal and vorticity properties and mobility characteristics of the corresponding anticyclones are highlighted over continental regions an association with low level pools of cold air is found to be prevalent for the eurasian anticyclones but less so for the north american anticyclones in the subtropical zone the anticyclonic signal in the regions affected by the winter monsoon including southeastern asia and the western pacific features prominently in the upper levels in the eastern sectors of the subtropical ocean basins the anticyclonic signal is less deep intense anticyclonic development at low levels is also identified over the western sectors of the subtropical continents where it appears associated to the effect of orography and of low level cooling the dominant type of anticyclone observed in the regions of blocking is characterized by 5 6 days timescales and considerable eastward mobility