the lefkada barrier and beachrock system nw greece controls on coastal evolution and the significance of extreme wave events abstract the lefkada preveza coastal zone nw greece is characterised by an active barrier system and related extensive beachrock sequences besides the gradual coastal processes of longshore drift and spit evolution the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system in this paper we present the results of detailed multi proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back beach positions our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary breakdown of the barrier system sedimentary findings suggest that one generation of event deposits may be related to the 365 ad crete earthquake and associated tsunami according to our results the lefkada coastal system formed by the interaction of both long term gradual and sudden impulsive littoral geomorphodynamics extreme wave events are assumed to have played a significant role in the evolution of the present coastline acting as recurrent impulsive disturbances of the coastal system subsequently the onset of long term gradual coastal processes such as longshore drift re established a state of natural coastal balance by re arranging the coastal sediments

bonaire s boulder fields revisited evidence for holocene tsunami impact on the leeward antilles abstract supralittoral boulders and blocks are prominent sedimentary features along rocky shorelines worldwide in most cases their deposition is attributed to high energy wave events tsunamis severe storms even though tsunami waves are expected to have higher transport capacities compared to storm waves megaclasts of up to 100 t were observed to have been moved laterally by the latter waveform the deduction of certain extreme wave events tsunamis severe storms from the boulder record thus remains a major challenge in palaeo event research the debate on their differentiation is ongoing at the eastern coast of bonaire leeward antilles in the southern caribbean numerous limestone blocks and boulders up to c 130 t are distributed on top of a 3 6 m a s l above mean sea level palaeo reef platform disagreement exists among a number of authors concerning the transport processes involved in the formation of the boulder fields in this paper state of the art modelling approaches of coastal boulder entrainment and transport were applied in order to provide new and more reliable data to support challenge the working hypothesis of tsunami deposition to improve the reliability of the boulder transport model more realistic input parameters were provided by new dgps measurements of the boulder dimensions and the calculation of bulk densities by taking into account the heterogeneity of the reef rock boulders existing hydrodynamic equations were modified to allow for the irregular shape and real dimensions of the boulders the results indicate that i boulder weight and dimension and thus ii calculated wave energy and wave heights were overestimated in most of the previous studies where calculations of boulder volume were based on multiplication of the main axes the results of this study and wave heights observed during recent severe tropical cyclones seem to rule out storm generated waves for the dislocation of the largest blocks however the majority of coarse clast deposits may have been generated by periodic hurricane swells the results underline the significance of more realistic field data in modelling boulder transports by waves

high frequency of super cyclones along the great barrier reef over the past 5 000 years understanding long term variability in the occurrence of tropical cyclones that are of extreme intensity is important for determining their role in ecological disturbances1 2 3 4 5 for predicting present and future community vulnerability and economic loss6 and for assessing whether changes in the variability of such cyclones are induced by climate change7 our ability to accurately make these assessments has been limited by the short less than 100 years instrumented record of cyclone intensity here we determine the intensity of prehistoric tropical cyclones over the past 5 000 years from ridges of detrital coral and shell deposited above highest tide and terraces that have been eroded into coarse grained alluvial fan deposits these features occur along 1 500 km of the great barrier reef and also the gulf of carpentaria australia we infer that the deposits were formed by storms with recurrence intervals of two to three centuries8 9 10 11 and we show that the cyclones responsible must have been of extreme intensity central pressures less than 920 hpa our estimate of the frequency of such super cyclones is an order of magnitude higher than that previously estimated which was once every several millennia12 13 14 and is sufficiently high to suggest that the character of rainforests and coral reef communities were probably shaped by these events

tsunami imprints on the leeward netherlands antilles aruba curacao bonaire and their relation to other coastal problems abstract tsunami are one of the major natural hazards in the caribbean the historical record lists 88 tsunami from local events to teletsunami in the time period from 1489 to 1998 this study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of holocene age in the southern caribbean at a worldwide scale these debris deposits represent the most extensive and impressive records of holocene paleo tsunami so far studied hitherto the leeward lesser antilles consisting of the islands of aruba curacao and bonaire were not known to have had tsunami affecting their coastlines the possible contribution of tsunami to configuring coastlines e g the questions of embayment development the coastal environment changes and the absence of holocene fringing reefs along the windward coasts is discussed

ice 5g and ice 6g models of postglacial relative sea level history applied to the holocene coral reef record of northeastern st croix u s v i investigating the influence of rotational feedback on gia processes at tropical latitudes abstract fossil coral reefs along the northeastern coast of st croix in the caribbean sea provide an 8000 year record of dated and interpreted holocene sea level change we herein compare this record with the predictions of models of glacio hydro isostatic adjustment for st croix and for additional sites at similar latitudes in the greater and lesser antilles region rsl predictions are based upon the model ice 5g vm2 and with a modified model ice 6g vm5a both including and excluding the influence of rotational feedback misfits between the modeled sea levels and the local geologic data are most apparent for models without rotational feedback particularly in the prediction of a 2 to 4 m unsupported mid holocene misfit at 4 ka as well as a small amplitude highstand that extends from 2 5 to 1 5 ka incorporation of the influence of rotational feedback provides the best fit to the data largely eliminating the unsupported mid holocene misfit between the data field and the sea level histories predicted by the models without rotational feedback and fitting data older than 5 kyr more closely than a previously published latitudinally averaged sea level curve for the western atlantic the st croix data therefore demonstrate that rotational influence extends at least 27 further south from its 45 n mid latitude extremum along the us east coast and identifies tropical latitudes as influenced by proglacial forebulge collapse implications for reef based sea level reconstruction include the ability to accurately model sea levels at specific tropical sites with partial holocene chronologies using the ice 6g vm5a model with rotational feedback latitudinally averaged sea level curves are therefore of limited use in understanding the relative importance of contributing physical influences on postglacial sea level history

comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

the role of porosity in discriminating between tsunami and hurricane emplacement of boulders a case study from the lesser antilles southern caribbean coastal boulder deposits are a consequence of high energy wave impacts such as storms hurricanes or tsunami parameters useful for distinguishing between hurricane and tsunami origins include distance of a deposit from the coast boulder weight and inferred wave height in order to investigate the role of porosity on boulder transport and elucidate the distinction between tsunami and hurricane impacts we performed archimedean and optical 3d profilometry measurements for the determination of accurate physical parameters for porous reef and coral limestone boulders from the islands of aruba bonaire and curacao abc islands netherlands antilles leeward islands subsets of different coral species and lithotypes constituting the boulders were sampled the physical parameters of boulders were analyzed and each boulder component was attributed to a certain range of porosity and density lowest porosities were observed in calcarenite 5 8 whereas highest porosities were measured for serpulid reef rock 47 68 porous serpulid reef rock 0 8 1 2 g cm 3 and the coral diploria sp 0 6 1 0 g cm 3 possess the lowest bulk densities while less porous calcarenite 2 0 2 7 g cm 3 and the coral montastrea cavernosa yield the highest bulk density values 1 6 2 7 g cm 3 the obtained physical parameters were used to calculate boulder weights and both hurricane and tsunami wave heights necessary to initiate transport of these boulders boulders are up to 5 6 times lighter than given in previously published data and hence required minimum hurricane or tsunami waves are lower than hitherto assumed the calculated wave heights the high frequency of tropical storms and hurricanes in the southern caribbean and the occurrence of boulders exclusively on the windward sides of the islands implicate that for boulders on the abc islands a hurricane origin is more likely than a tsunami origin 2008 elsevier b v all rights reserved

mid to late holocene changes in tropical atlantic temperature seasonality and interannual to multidecadal variability documented in southern caribbean corals proxy reconstructions of tropical atlantic sea surface temperature sst that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability here we present monthly resolved records of sr ca a proxy of sst from fossil annually banded diploria strigosa corals from bonaire southern caribbean sea the individual corals provide time windows of up to 68 years length and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal sst variability in the western tropical atlantic during snapshots of the mid to late holocene comparable to modern climate the coral sr ca records reveal that mid to late holocene sst was characterised by clear seasonal cycles persistent quasi biennial and prominent interannual as well as inter to multidecadal scale variability however the magnitude of sst variations on these timescales has varied over the last 6 2 ka the coral records show increased seasonality during the mid holocene consistent with climatemodel simulations indicating that southern caribbean sst seasonality is induced by insolation changes on orbital timescales whereas internal dynamics of the climate system play an important role on shorter timescales interannual sst variability is linked to ocean atmosphere interactions of atlantic and pacific origin pronounced interannual variability in the western tropical atlantic is indicated by a 2 35 ka coral possibly related to a strengthening of the variability of the el nino southern oscillation throughout the holocene prominent inter to multidecadal sst variability is evident in the coral records and slightly more pronounced in the mid holocene we finally argue that our coral data provide a target for studying holocene climate variability on seasonal and interannual to multidecadal timescales when using further numerical models and high resolution proxy data

coral boulders gravel tongues and sand sheets features of coastal accretion and sediment nourishment by cyclone tomas march 2010 on taveuni island fiji abstract tropical cyclone tc tomas in march 2010 was a category 4 storm that struck the northern and eastern islands of fiji in the southwest pacific with the coast of taveuni island in particular experiencing a significant surge and high waves as the eye passed within 30 km post storm field investigations of the coastal geomorphic impacts concentrated on an area in central taveuni s16 50 179 52 w where protected fringing reefs and coastlines form part of the bouma national heritage park bnhp here a range of cyclone constructional imprints were found to have supplemented existing coastal sediments fresh coral boulders strewn across reef platforms indicate that tc tomas had sufficient power to deliver new coral blocks but that this material comprises a relatively minor component 20 of pre existing boulder fields comparison between the dimensions of fresh max 4 9 m 3 and older blocks max 40 m 3 reveals that unknown earlier events storms or tsunamis produced much larger debris and therefore presumably generated much stronger flow velocities across the fringing reefs than tc tomas analysis of calcarenite slabs quarried from in situ beachrock exposures was particularly useful for calculating storm surge flow velocities at the shoreline giving mean values of 3 4 and 1 9 m s for run up and backwash respectively several elongate tongues max length 75 m of fresh coral gravel were also constructed perpendicular to the reef crest a conceptual model of debris accretion based on wave refraction across a crescent shaped reef front is developed to explain their formation but which does not rely on the simultaneous existence of a reef parallel rubble rampart overall the patchy and discontinuous nature of cyclogenic accretionary features across reef beach and back beach locations indicates the potential challenges for identification and interpretation of palaeo cyclone events within the sedimentary record on affected coastlines in the south pacific islands

hurricane signatures and landforms toward improved interpretations and global storm climate chronology abstract the correct understanding of the geological and geomorphic evolution of paralic basins and coastal barriers is a prerequisite for establishing holocene hurricane archives worldwide detection and documentation of hurricane signatures in coastal deposits are becoming instrumental in attempts to reconstruct mid and late holocene storm climate history subsurface exploration and field studies on the ne gulf coast and data gleaned from the literature suggest the need for a complex approach that provides well documented details of coastal landscape evolution until recently prehistoric hurricanes and their intensity levels have been automatically interpreted from the frequency and thickness of sand layers in muddy paralic deposits however in addition to wind velocity several hydro aerodynamic and other factors a wide range of stratigraphic conditions topographic setting and sand sources also determine variations in the extent and intensity of storm flooding erosion transfer and deposition of sand layers in small paralic basins inherent limitations in these sedimentary records and their interpretation must be overcome in order to improve local hurricane chronologies and establish interregional correlations before sedimentary and chemical signatures are accepted as diagnostic indicators of overwash especially by catastrophic hurricanes alternative causes must also be considered a parallel scale of storm flood level stages should supplement the saffir simpson hurricane categories the relationship between storm intensities and flooding elevations is highly complex changes in sea level shore positions formation and extinction of preexisting incised valley networks the impact of transgression and regression processes on estuaries and their deposits play determining roles in setting the stage for overwash processes strandplain progradation followed by erosive shore retreat played a key role in framing certain paralic lakes without overwash sand layers and marine microfossils may be also emplaced by storm driven currents that enter unobstructed estuaries inlets and storm breaches bioturbation also distorts the storm record significant lateral variations in the number and thickness of intercalated sand layers at closely adjacent sites suggest the importance of local differences in sources transport and preservation processes in the dimensions relative positions and accessibility of sand resources inside and adjacent to coastal basins variations in the number thickness and ages of sand laminae may not be related to the number of storms and their intensities this may impair correlations between regionally interpreted calm and intensive phases in partial overlap with an assumed quiescent storm phase stable isotope ratios in lacustrine muds impacted by salt water influx reveal frequent hurricane activity during the last 1 5 ka as well by mimicking effects of reduced storminess the fewer and thinner sand laminae deposited between 7 0 and 3 4 ka b p may be attributed to greater distances of estuarine landward transport by storm tidal currents at times of lower sea levels

electron spin resonance and radiocarbon dating of coral deposited by holocene tsunami events on curacao bonaire and aruba netherlands antilles abstract electron spin resonance esr dating of coral has become an efficient geochronological tool for studying the last 500 000 years this study presents results of esr dating of holocene coral from curacao bonaire and aruba leeward netherlands antilles the coral accumulated in rubble ridges and ramparts onshore and the depositional process is attributed to a series of tsunami events in addition to the calculation of equivalent dose d e values it is crucial for esr dating to obtain the correct d 0 value for each sample the annual dose rate d 0 estimation of the samples in this study is uncertain as the timing of the tsunami event and the residence time of a component of the dated sediment in different environments marine versus terrestrial is difficult to quantify assuming that the tsunami event deposited coral shortly after death the esr and 14 c ages of 22 samples reaching from 3650 to 128 years correspond well with each other this confirms the idea that the living coral reef was partly destroyed by tsunami events the esr dating uncertainties coincide with the variability of 14 c ages caused by the marine reservoir effect the local marine reservoir effect was estimated using four recent samples from 1920 and provided values between 375 and 595 yr bp

a depth integrated sph model for debris floods application to lo wai hong kong debris flood of august 2005 in this work an approach to representing debris floods and flows is proposed based on a depth integrated mathematical model and smooth particle hydrodynamics numerical technique the main contribu

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

competing mechanisms for boulder deposition on the southeast australian coast this study investigates the role of late holocene sea level change large storms and possible pre historic tsunami in the deposition of boulder features on an exposed headland and sheltered rock ramp large accumulations of boulders are found on coastal rock platforms cliff tops and ramps in the jervis bay region of southeastern australia these deposits are elevated above sea level and in places exhibit obvious signs of imbrication as a response to flow in a landward direction the event history of these features is controversial and holocene sea level change storms and tsunami can be considered as possible non mutually exclusive mechanisms of deposition it is apparent that even if the detachment site transport distance elevation and final orientation of a boulder can be identified deciphering the event history remains a difficult task

tsunami probability in the caribbean region we calculated tsunami runup probability in excess of 0 5 m at coastal sites throughout the caribbean region we applied a poissonian probability model because of the variety of uncorrelated tsunami sources in the region coastlines were discretized into 20 km by 20 km cells and the mean tsunami runup rate was determined for each cell the remarkable 500 year empirical record compiled by o loughlin and lander 2003 was used to calculate an empirical tsunami probability map the first of three constructed for this study however it is unclear whether the 500 year record is complete so we conducted a seismic moment balance exercise using a finite element model of the caribbean north american plate boundaries and the earthquake catalog and found that moment could be balanced if the seismic coupling coefficient is c 0 32 modeled moment release was therefore used to generate synthetic earthquake sequences to calculate 50 tsunami runup scenarios for 500 year periods we made a second probability map from numerically calculated runup rates in each cell differences between the first two probability maps based on empirical and numerical modeled rates suggest that each captured different aspects of tsunami generation the empirical model may be deficient in primary plate boundary events whereas numerical model rates lack backarc fault and landslide sources we thus prepared a third probability map using bayesian likelihood functions derived from the empirical and numerical rate models and their attendant uncertainty to weight a range of rates at each 20 km by 20 km coastal cell our best estimate map gives a range of 30 year runup probability from 0 30 regionally

potential and limits of combining studies of coarse and fine grained sediments for the coastal event history of a caribbean carbonate environment the coastal deposits of bonaire leeward antilles are among the most studied archives for extreme wave events ewes in the caribbean here we present more than 400 electron spin resonance esr and radiocarbon data on coarse clast deposits from bonaire s eastern and western coasts the chronological data are compared to the occurrence and age of fine grained extremewave deposits detected in lagoons and floodplains both approaches are aimed at the identification of ewes the differentiation between extraordinary storms and tsunamis improving reconstructions of the coastal evolution and establishing a geochronological framework for the events although the combination of different methods and archives contributes to a better understanding of the interplay of coastal and archive related processes insufficient separation superimposition or burying of coarse clast deposits and restricted dating accuracy limit the use of both fine grained and coarse clast geoarchives to unravel decadal to centennial scale events at several locations distinct landforms are attributed to different coastal flooding events interpreted to be of tsunamigenic origin coastal landforms on the western coast have significantly been influenced by sub recent hurricanes indicating that formation of the coarse clast deposits on the eastern coast is likely to be related to past events of higher energy

the mystery of boulders moved by tsunamis and storms abstract boulders are moved differently in storm and tsunami and produce different characteristics of the boulder deposits this contribution is motivated by two observations one by bourgeois and macinnes 2010 which described that boulders were moved selectively due to different bed roughness during 15 november 2006 tsunami on the island of matua the second topic is motivated by the boulder lines on ishigaki island by goto et al 2010 both topics are approached with linear wave theory and stability analysis from both the safety factor is derived for a spherical boulder with bed roughness and exposure as moment arms with which we are able to quantify the influence of bed roughness on the incipient motion of boulders for constant forces a bed roughness of about 30 of the boulder radius will prevent boulder transport furthermore the comparison between storm and tsunami waves in terms of the amplitude necessary to move boulders revealed that amplitude of storm waves is smaller than tsunami which we ascribe to the contribution of both velocity components to lift forces the comparison of total energy and number of waves revealed that storms have a larger total energy and a much larger number of waves which lead us to the conclusion that tsunamis produce unorganized boulder deposits whereas storms are capable of organizing boulders along lines and in clusters

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

developing vanadium valence state oxybarometers spinel melt olivine melt spinel olivine and v cr al partitioning spinel melt for martian olivine phyric basalts a spiked with ree v sc martian basalt yamato 980459 y98 composition was used to synthesize olivine spinel and pyroxene at 1200 c at five oxygen fugacities iw 1 iw iw 1 iw 2 and qfm these run products were analyzed by electron microprobe ion microprobe and x ray absorption near edge spectroscopy to establish four oxybarometers based on vanadium partitioning behavior between the following pairs of phases v spinel melt v cr al spinel melt olivine melt and spinel olivine the results for the spinel melt olivine melt and v cr al spinel melt are applicable for the entire oxygen fugacity range while the spinel olivine oxybarometer is only applicable between iw 1 and iw 1 the oxybarometer based on v partitioning between spinel olivine is restricted to basalts that crystallized under low oxygen fugacities some martian all lunar as well as samples from 4 vesta the true potential and power of the new spinel olivine oxybarometer is that it does not require samples representative of a melt composition or samples with some remnant of quenched melt present it just requires that the spinel olivine pairs were in equilibrium when the partitioning of v occurred we have applied the v spinel olivine oxybarometer to the y98 meteorite as a test of the method

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

progress in esr dating of pleistocene corals a new approach for de determination abstract esr dating has been widely applied for dating of corals of the age up to 500 000 to 600 000 years ago many studies have yielded promising results but the accurate determination of the equivalent dose d e remains a major limitation inflexion points in the dose response curve are shown to hinder correct fitting and limit the reliability of d e values here we present a new approach to obtain more reliable d e values

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved